NOTES ON ANESTHESIA COLLEGE OF SHYWANS - ht4D -SURGEONS COLUMBIA UNIVERSITY, NEW YORK In the absence of an adequate anestheeia textbook, the following notes are offered as a supplement to the refer- ences listed on the next page. The student who flnde that the physiological mechanisms briefly referred to in this outline are unfamlliar to him will do well to review them at this time in his textbooks, and lecture notes of previoua courees. There are three people of great importance in the conduct of the anestheeia: the patient, the anesthetist and the surgeon, The statements which follow take for granted an ideal situation: an experienced surgeon who works quickly and gently, and leaves the choice of the anesthetic agent and technic and the conduct of the anesthesia to the ones- thetist; a wholly capable anesthetist who knows how to choose and use all the anesthetic agents and technics well, and who understands fully the eurgeon's needs; and the most Important, but also the most variable individual, the patient. He be- comes lees unpredictable the more the surgeon and anesthetist know about hie disease and how it affects him as a whole, The anesthetist cannot adequately evaluate his patient unlees he is first a good physician with a work- knowledge of physi- ology, SUGGESTED READING 1. Guedel, A. E. "Fundamentale of In%alation Aneetheeia" 2. Goodman and Gibn. "Phsrmacological Baaie of Therapeutics" First 100 pagee, Chaps. 9, 12 and Seotion V. 3, American Medical Aseociation. '%undamentala of Aneetheela" 2nd Ed. 4. Cuflen, S. C. "Anesthesia in General Practice" 5. Cowville, C. B. '?Jntoward Reactims to Ritrous Oxide Anesthesia" Excellent for pathology of anoxia. 6. Brinker, cb K. "Puhonary Edema and Inflamtnation" Good background for pulmomary compllcatione. 7. Miller, W. S. "The Lungt1 9. Adrfanf, John "Pharmacology of Anesthesia" "Chemfatry of Aneetheaia" "Technics and Procedure6 of Anesthesia" 10, "Anesthesiology, I' a monthly Journal 11. Gillespie, N. aEndotracheal Anesthesia" 2nd Ed. 12. Leigh, M.D. "Pediatric Anestheeia" RES PIRATION It is most important that the anesthetist be thoroughly familiar with the physiology of respiration since the lungs are the only site at which oxygen may enter the body, the chief site of excretion of carbon dioxide, and the eite of absorption and excretion of many of the anesthetic agents, The mechanics, physical principles, and physiological control which cauae these gases and vapors to enter and leave the lungs should therefore be well understood, in order that the aneathetist may recognize the changes which take place when the nom1 state passes to the pathological, or when consciousness is replaced by progressively deepening anesthesia , Careful observation of all phaeee of respi- ratim telle more about the depth of anesthesia than all the other eigne cm- bined. Control The conscious control of respiration disappears entirely with the m- set of the anesthetic state. Respiration becomes machinelikw, and variations in it depend entirely on the mechanical or physiological changes produced by the ane 8 th e t is t or 6 urge on. The unconscious or automatic control is chiefly chemical in nature. It i8 the oonoentration cjf the H ions in the respiratoaPy center whiob aff& aeomd te aeclond osntr31 of respimtdon. Beosuse of the great diffwibility of earbon dioxide through cell nembranes, it usually oauees these changes in pH, but they may be due to lactic acid, unoxidized fatty acids, etc. Hyperpnea fOlhJ8 an increase in acidity and diminished tidal volume follcwa a decrease in acidity. When the reapiratory center is abnormally depressed by druga (anesthetic agent, morphine, barbiturates, etc.) the site of automatic control ie probably shifted to the carotid bodies. A low oxygen tension is now the respiratory etimulant, 2 not pH changes. Excess oxygen under these conditions will cause a period of apnea, until either the hypoxic stimulus recurs, or the C02 teneion rises above the level of the respiratory center's threshold. Reflex control is present to a lesser extent. Copmnon sites of origin €or the afferent inpulses are the skin (pain, cold), the receptors of the vagus in tho respiratory tract, the peritoneum, rectal sphincter, the carotid sinue, aortic arch, and carotid body. The afferent impulae probably travel6 up the peripheral or eamatic nerves to the respiratory center. The efferent impulse may travel down the vagus to the larynx and bronobi to cause lar,vngoepaem Or bron- chospasm, or dawn the cord to the cervical region (phrenics) and thoracic re- gions innervating the intercostal musclee. It ie an error to presuppose a noma1 reepiratory center in the eurgl- cal patient, Although sometimes stimulated (pain, fever) it is more often de- pressed, and its threshold to stimuli raised because of drugs wed, or because of abnormal metabolism arising from the patient's illness, In order of frequency, the most cannon respiratory depreasants are the anesthetic agent, the premedice- tion drugs, oxygen lack and a marked C02 excees. The production of oxygen lack, or carbon dioxide retention is ae In- excusable as an overdose of premedication drugs or anesthetic agents. A relative oxygen lack (hypoxia) is frequently present with certain diseases such a8 hyper- thyroidism, aevem anemia, pulmonary fibroaie and poorly compeneated circulatory systems, but the oxygen lack should be treated before operation is caneidered. Anatmv A knowledge of the anatmy of the reepiratory tract is Important eo that we may predict and thereby prevent respiratory obstruction, or looate it prmptly should it occur. Respiratory obstruction is the ccomnoneet aneethetio complication. Frequent causes for obstruction and their treatment are listed on the next page. 3 Upper Re e@frat bry Tract Treatment Chaqing position of head; artificial airway Tongue against pharyngeal wall in supine poeition Large tone ila , pharyngea 1 t mors ; pharyngeal edema FluidrJ: mucus, blood, pue, vomitus Laryngospasm: direct irritation aneethet- ia agent, nucu~, vanitus, pus Reflex laa!yngosp,sm Nasal obetruotion plus tightly closed mouth : adenoids, rhinltie, weeping Lawer Beapiratorz Tract Fluids : mucue, vmitus, blood, pus Asthma; ref lex bronchospasm S ubs te ma 1 thyroid, me dias t Ina 1 tumara canpressing trachea Artif ioial airway beyond point of obatruation Prophylaxis, premedication, head down, suction Slower induction, uae of non- irritating agent first, pre- medication, properly fitting airway, gravity and suction Gentle suraery; adequately deep anestheeia; avoidance of oxygen lack and GO2 excess Preoperative shrinkage naeal muc oua membrane ; ora 1 8 irway early Prophylaxis ; head down, suction Proper selection aneathetic agent; helium Airway eetabliehed beyond obatruction; helium Mechanics Contraction of the diapbragm and external intercoatale producee the negative pressure which pulla the lungs outwards, causing an inrueh of air. Re- laxation of these muscles cause8 the reverse prooem, expiration. Only in foroed expiration are the internal intercoetafs and the abdaminal musolee contracted. Normally there is always a negative presaure in %he pleural apace, It can becane more negative by inepiring against a cloaed glottis, or by produciq a rtaesive atelectaais. It is more poaPtive with forced expiration against a aloeed glottic (beginning of a cougfi) and with pneumothorax. The intrapulmonary presaure, in tbe reeting phaee of respiration, ia the aam aa atmoepheric pressure. Dieturbed 4 intrathoracic pressure relations may embarrass thecirculatibn ae well as the reepiration by altering; the venoue return to the heart. Maintenance of the proper pressure relatime depends also on an Intact thoracic cage, with good mobility at the coetovertebral and sternoclavicular joints o Lung motion ia essentially passive. Active changes in bronchial lumen and length may contribute to lung expaneion with inspiration and expiration is aided by the elastic recoil of the lung tisaue. The beat aerated portions are the lower lobes and anterior parts of the upper lobes. With inspiration the apex and lung root move downward, the lung baee downward and outward, the remainder of the lung outward and slightly upward. Nwneroue factors may interfere with the meohanice of reapiratim, causing a decrease in vital capacity, and thereby producirq inadequate transport of anesthetic gase8, oxyeen and carbon dioxide to and from the blood atream. Pathological: Pulmonary.. . .Fibrosie of interstitial tissue Chronic bronchitis; emphysema Aathma Tuberculosis Pneumonia Atelectasis Pne moth orax Ple ura 1 a dhes ions Rilpyema Skeletal. o . . .Oeteoarthritis of' spine Previoue rib reeections Kyph om olios is Muecular. o o ..Residual poliomyelitis diaphragmatic paralysis intercostal paralyais paralyzed spinal musclee with chest deformity Diapkragina t ic hernia Mediastinal. .Tuxtors substernal thyroid Pericardia 1 effusion 5 Abdminal. . . .Distension of hollow viscera Pregnancy Ovarian cyst; fibroid uterue Ascites Bepato-.and splenmegalies Produced during operation: Change in position: head dawn, prone, lateral, Mdney bridge Open chest for thoracic surgery Weight of assfatant's arm on cheet Rmwa 1 of riba , th orac oplaety Retractore on coetal margin Pad8 against diaphragm Depreseion of muscular activity by aneathetic drugs A te Is c t a s i 8 IIIEPLRATORY OBSTRUCTION CIRCULATION CSroulation is as important a8 reepiration in the proper distribution of oxygen and the aneathetic agent to the tisauee, and in the excretion of carbon dioxide and the anesthetic sent. Circulatory signs are not eepecially helpful in determining the depth of anesthesia, but are of great aesistance In dotemining the reaction of the patient to the operative trauma and the anesthe- eiar Only with an accurate and frequent record of pulse rate by palpation, and blood pressure by auscultation can a proper interpretation and prbgnoeie be made. C ontsol The control of the circulation ie like respiration in that the stimu- lus ie chemical in nature, but unlike respiration, in that the "paoemaker" ie in a peripheral region rather than in the medulla. The eino-auricular node ie the origin of tho heart beat, and change8 in acidity of the tiseues which make up the S-A node influence the rhythm greatly. In the heart, the important chemical stimuli are the inorganic ions, Ca, K and Na, not carbon dioxide. The condmting tiesue of the heart ia quite different frcan the nervous tlssue carrying the respiratory impulees, but in both system8 activity leads to a refractory period, when further activation cannot take place. Several neurological connections exist which contribute to the control of c irc ulat i on . a. The right and left vagus nerves supply the S-A and A-V mdee respec- tively. Their normal action is one which keeps the heart in check. Stimulation of the vagus produces a marked afming in rate, with or without a heart block. Tbe accelerator nerves, belonging to the sympathetic nervous Bystam, b. supply the heart much more diffusely. Their cell bodies are located in the tho, raoic cord, frum T1 to TG and their first synapee occurs in any of the cervical and upper five thoracic sympathetic ganglia. The postganglionic fibers may travel in the cardiac plexus, or actually join the vagus nerve trunk. The aympathetics and vagus tenti to balance one another normally, but stimulation of one eystem depresses the activity of the other, and blocking of one system produces an exag- geration of the si@ of activity of the other. C. Both the diviaions of the autonmic nervous system supply the peri- pheral arterioles . Vasmonstriction occure with eympathetic stimulation; vaaodi- lation occurs loae forcefully but is probably mediated by the parasympathetic system. Exceptions to thia gemral rule are the coronary and cerebral vessels, which dilate with aympathetic stimulation. Capillaries apparently possess con- trictility Quite independent of the state of the arterioles, ar neurological connectione o Afferent connections of the nervous aystem with the circulation exist in many places * The morst important f olfm : 8. Carotid sinus : Receptors two preeent in tbe walls of the carotid ainue, at the bifurcation of the ccgnmon carotid into its external and internal bramhes, The afferent impulaea pas8 along the carotid 8inue nerve, a branch of the glaeeo- pharyneeal nerve, and branchee of the vague and cervical sympathetlce. Reflexee 7 frm this region normally keep the blood pressure at a constant level. Pressure changes inside or outside the sinus wall are the chief stimulating factors. Overstimulation results in hypotension and bradycardia . 3. Aortic arch: the afferent path is up the vagus nerve to the medulla. Its reactions are similar to the carotid sinus reflexes. All these impulses are collected by the vasomotor center in the me- dulla, which synchronizes the circulatory reaction. Changes in respiration fre- quently occur at the same time because of the cloae relation of the respiratory and vasomotor centers. Sh oc 1: This is the cmonest circulatory accident. The word is poorly chosen, for many connotations have been ascribed to it. What is meant is a discrepancy between the qirculating blood volume and the capillary bed. The sequence of events in increasing shock la: 1. 2. 3. 4. 5- 5. 7. 8. 9- 10 . Precipitating trauma : severe burn, hemorrhage, prolonged surgical trauma, deep anesthesia Capillary dilatatian and arteriolar constriction: trapping of much blood in capillary bed making it unavailable for general circulation Constriction 01 spleen to supply zilore blood Increased heart rate, to deliver diminished volme better Diminighed venous return Increased reapirations (hypoxic etimulua to carotid body) to supply more oxygen to overworking heart, until center damaged by hypoxia Lose of proteins through capillary wall to tissues Viscosity of blood greater - lcore difficult for heart aa a pump Further capillary damage from prolonged hypoxia o IVm irreversible Failure of myocardiura because of poor oxygenation It is obvious that treatment of ahock must be prompt and rational. It is directed tawards: 8 1. Supplying ample oxygen 2. Restoring blood volume 3. Restoring plaspls proteins 4. Restoring RBC, if blood has been lost The anesthetist '8 inmediate reeponsibillty is to institute mans of providing the patlent's tissues, ehpecially the oerebral tissues, with ample oxygen# and to maintain optimal oxygenation while fluids, blood and blood substitutm~ are obtained and administered by &hers. If help is not available the anesthetiet should first set up a ~ouroe of excess axygen and an infallible alrway, befme embarking on What may be a difficult and time-oonsuming venipundum in a pa- tient with peripheral vascrmcrtor collapse. There is no rationale in giving cardiao rstimulants. Adrenalin, Ana- leptics (coramine, metrazol, etc .) and carbon dioxide stimulate heart muscle ONLY if it is well oxygenated. Ane a the t ic Ihp lic at i om 1. Evaluation of the risk of a cardiac patient is merely the evaluation of his compensation and reeerve. Any surgical operation or aneetheaia impoms a strain on his circulatory system, and a careful history of his tolerance of other kinds of strain will give better clues as to the length and eeverity of the surgical procedure he car, tolerate, than phyeioal examination of his heart and peripheral vessels . Determining the presence or absence of murmur^, abnormal rhythms, or vascular thickening cannot alone lead to an accurate prognosis 4s to functional efficiency and adaptability of the circulatory system. 2. All anesthetic agente depress heart muscle directly, mklng it a less effective pump. The deeper the anesthesia, the worse is the depression, Chloro- form and ethyl chloride are the moet sevwe depreseants, 3. Ether anesthesia, carried no deeper than second plane, is probably tbe 9 safest for a cardiec patient. Because of its irritating effect on the reepira- tmy system, inspiration is stimulated which causes a better venous return to the heart. Within certain limits, this meam an improved circulation. 11. Oxygen lack is the worst depreseant for heart nuscle especially if it is already danaged. (Myocarditis, rheumatic fever.) Ample oxygen MIET be sup- plied to cardiac patients. 3. The conduction system In %he heart is often affected by the agent. Cyc lopropane frequently produces irregularities in rhythm wh fch are not perma- nent. All druge, even procaine and the barbiturates, cause EXZ: changes. 5. The vasomotor center is depressed especially by the non-volatile drug8 : short-acting barbiturates avertin. Deep anesthesia with the inhalation agents €11130 cauees a mrked depremion, so that compensation for impending shock, by vasoconatriction, is completely lost. Tbe anest21etist always attempta to keep the blood preeawe and pule6 at their normal leve18, in spite of the surgery. Following are some of the CQDS mon reasons for changes in them. Increased Puleo Bate Rise in Blond Pressure Oxygen want, early Carbon dioxide excess Eemorrhage Ligh't anestheeia Ether Exceeeive sweating Wreased adrena lin output Fluids given too faet AnaLept ice Large doees atropine or scopolamine Decreased Pulse Rate Eigb epinaf anestheeia Neasynephrine Sudden, eevere anoxia Carotid sinus reflex Celiac plexus ref lex Chloroform, ethyl chloride cyclopropane Poeition of patient head dmn lith ot coly Oxygen want, earl? Carbon dioxide exce8e Manipulatian of toxic thgroid Analeptics Fluids Fall ia Blood Pressure Position of patient aitt ing change during anesthesia prolonged Trendelenbur6 Ckygen want, late Marked carbon dioxide excess Deep anesthesia 10 Decreased Pulse Rate Heart block Vomiting Drainage of cerebrospinal fluid Procaine reaction Fall in Blood Pressure High spinal aneethesia Avertin, i.v. barbiturate vomit in$ Carotid sinus, celiac plexus Prolonged operative trauma Sympathectcrmy for hypertension Hemorrhage . Accidents1 i.v. procaine ' Sudden release of increased abdominal pressure : pregnancy, ascites, cysts Decreased Pulse Pressure Carotid sinus ref lex Celiac plexus or other traction reflexes Shift of mediastinum: thoracic surgery High spinal anesthesia Intracranial pre Gswe change8 fntracranial manipulation CENTRAL IvERvuus SYm A reversible and oontroUahle depression of the nervous system is the aim of' any anssthesla. It would be desirable to limit the action of the drugs to the nervous system alone, but by most technics this is impossible, since the drugs are carried by the blood stream. Only by regional blocks (spinal, psrw blocks, local infiltration) are parts of the nekrvous system anesthetized di- rectly. The inhalation agents cause an ascending paralysis of the spinal cord. This means that the intercostal muscles, supplied by the thoracic cord are para- kyzed before the diaphragm, with its cervical innervation. During deepening anesthesia, the lower, then the upper interoostals and finally the diaphragm lose their activity and tone, an8 during recovery frm deep anesthesia, them musclea recover in the reverse order. Otservatian of the comparative activity of these two groups of muscles gives UB one of our most important respiratory signs . 11 Concomitant with the ascending cord paralysis, deprespJim of the brain progresses from ite most specialized to its least specialized centers. The cere- brum is depressed first, with early loss in judpent and reason, followed by loss of memory and consciousness. Of the special senee6, hearing remains intact the longest, and recovers first. The cerebellum then shares in the depression as evidenced by the ataxia of second stage. ObJective signs of further depression are not obvious, but progress dawn through the thalamus, midbrain and medulla. sgvere lnaduUary depression indicatea an approaching irreversibility of the an. esthesia. 'RlemOSt serious depressant for the nervous systm is oxygen lack. In normal persons, it is a matter only Qf minutes (cerebrum, 8 min.; medulla, 30 min.) before permanent destruction takes place. In a person who is already in a chronic hypoxic state (cardiac, pulmonary pathology, anemia, prolonged partial obstruction of airway) this time interval is reduced to seconds. After a mvere hypoxic episode, permanent sequellae, such as personality change#, visual dis- turbances, and changes in muscle tonus, sensation and control of fine movements may occur. Cerebral hypoxia in the newborn is known to be related to certain types of mental deficiency and spastic states appearing during the child's de- velopment. An eplsode of hypoxia severe enough to be inccaapatible with recovery fa characteristically follcwed by failure to regain consciousness, restlessness, convulsians, hyperthermia, cm and death. Since no treatment can change this pictnre once it develops, prevention of oxygen want is the only mema of control- ling thia problem. AUTONOMIC NERVOUS SYSTEM The autoncanic mrvoua system is one of tbe most cmpUcated and one of the most fascinating ooncepts in physiology. For a clear presentation of the problem, especially of that part relating to chemical mediatian of the nerve im- pulse, Chapter 19 in Goodman and Gihn, is recammended. None of the anesthetic drugs fits entirely into an adrenergic 0.1- cholinergic classification but the common agents can be divided roughly as fol- Adrenergic stimulation: ether, chlorof om, oxygen lack, C02 excess Cholinergic stimulation: cyclopropane, barbiturates, morphine Spinal or nerve blocks paralyze the sympathetic fibers to the part anesthetized Atropine and scopolamine depress cholinergic activity Although a patient may be anesthetized to various stages of depression, stimuli are not prevented frm reaching the nervous system and produciw re- sponses. Most of these .reflexes are respiratory and circulatmy in nature and are mediated by. the autonmic nervous system. Correctly speaking, this is solely an effector system, but many afferent fibers run in autonomic nerve trunks (splanchnic, vagus).. The cell bodies for these fibers are in the dorsal root ganglia, or the vagus nucleus. Origin of afferent impulses : Traction on upper abdominal viscera, mesentery, cecum, pelvic organs, Manipulation of recurrent and superior laryngeal nerves, phrenio nerves, Periosteal sthulation - especially rib periosteum Lung hilum stinulation Stimulation of celiac plexus: manipulation of conanon duct, pads, retractors, Stimulation of carotid sinus: neck infections, head dawn position, re- perinem vagi elevated kidney rest tractor in thyroid surgery, neck dissections, anesthetiet 's finger pressure, extreme lateral flexion OT neck Dilatation of rectum, vagina, cervix Overdistention of lungs Irritation of nasal or tracheal mucous membranes Marked apprehension preoperatively; marked excitement stage The efferent effects may be: Respiratory: hryngospam, or adduction of vocal cords apnea, YMTegular Circulatory: change in pulse rate, arrhythmia, hypotension, diminution in Increase in puscle tanus, agnvulsions re spire t i on, b ypo ypqea , br mch ospa 8m pulse pressure, hypertensian Treatment is mainly prophylactic 1. 2. 3, Adequate premedication to control psychic state and to diminish irri- 4, 5, Blocking of area of reflex activity with procaine Deep anesthesia before traction ia exerted 3roduction of a8 little trauma as poesible, and if necessary gently and steady, not sudden traction tability of the nervous system (morphine) Endotracheal airway for upper abdcaninal and neck surgery Aner ref lex has occurred, treatment may be : 1. 2. Blocking the reeion with procaine locally 3. 4. 5. Stopping trauma or traction when POSSible : reexerting traction slowly and steadily Changiw level of anesthesia, giving adequate oxygen, and removing Supplementing light anesthesia with additional doses of morphine (with me of some drug to cban&e the balance in the autonomic system: atro- excess C02 mopolamine or atropine) for general reflex depreseion pine ephedrine, physostigmine, ergotamine : all have been succeesful in @me cases PHEMEDIC ATION Premedication is as important in anesthesia as the choice of' agent or technic. The reasons for using premedication are several: 1. Psychic depression of patient: Abolition of undue alertness and anxiety reduces the incidence of excitement during induction, and increases the eaee with which subsequent anesthesias may be given to the same person. A atoMoy In- duction usually leads to hyperactive ref lexes and increased secretions, come- quently to a stormier uaintenance and recovery. 2. To lower patient '8 ref-lex irritability, which parallels his metabolic rate. Less anesthetic agent in actual amount is needed to produoe and maintain surgical anesthesia if the starting paint of the anesthesia is at a relatively low metabolic plane, Excretion of the agent and recovery frm anesthesia is 14 consequently more prmpt o If ref lex irritability is depressed by premedication, there is less likelihood of such cmplications as vmiting during inductian, breath holding and coughing with imitating agents, and reflex Larpgospasm. 3. To prevent excessive seoretime in the respiratory tract. The develop- ment and retention of excessive secretions during anesthesia increases the ever- the stimulation of secretions by ether that the tern itether pneumonia" was coined. This misnamer is camonly applied to what starts a8 an atelectasils and later develops into pnewaonia . 4. To prevent the convulsant action of drug6 used for local, block or spinal anestheaia. Acarding to experimental evidence the barbiturates are the most effective o 5. To coynteract autonomic nervous system effects of certain anesthetic agents; i .e., intravenous barbiturates and cyclopropane are apparently cholin- ergic drugs and are best preceded by scopolamine or atropine. kPES OF DRUGS USED: Barbiturates are best for psychfc depression, and for counteracting the convulsant effects of the regional drugs. They are not satisfactory for lowering reflex irritability. Alone, they cause increased secretions. Morphine is the best drug for genere1 lletabolio depreaeion and dim;irutirn of reflex lrritabillty, Dsrmerol is almost a8 satisfaatmy and ha the addea advantage of produalng brcmchobilatien, leas reeplratary center bapcssion and lees nausea an8 vdting t& comparable riosea qf mrgkir-e, Atropine and sccrgolamine ere both good drugs for preventing eecmtians, counteracting the respiratmy depression and the tendency to vamit after mor- phine, and preventing excessive parasympathetic activity. The only important dif- ference between the two drugs is their opposite effect on the cerebral centera: atropine ie atikulating, causing increased alertness, while scopolamine is a mild depressant causing drowsiness, and suinetimes amnesia . Avertin is a premedicatim and not an anesthetic drug. It is desirable from the patient's point of view because of the ease with which it produces un- consciousness, but is undesirable because of the length of time protective (cou&) reflexera are depressed. Used, however, only to produce amnesia, most or' the ObJections to the drug are outweighed. Intravenous barbiturates also produce prmpt and easy lOS8 of con- sciousness but in moderate doses are preferable to averbin since they are meta- bolized so quickly that laryngeal and cough reflexes return rapidly. The dose of these drugs depends upon certain factors in the patient's pathology and physiolog;!. The following conditions are c~lllllon ones demanding than average doses of depressant drugs : Fever Hyperactive personality Pa in Muscular constitution Ma rke d appm h e ns i on Hyperthyroidism Pregnancy Neurosis Adolescence Manic type of psychosis. Determination to resist sleep Chronic alcoholism The following demand - less than average doses: Anemia Hemorrhage Shock Hypothyroidism Chronic illness Weight loss Acute alcoholism Cardiac diaease Obesity Ne ph r i t i s Senility, infancy Previ ou~ depressant drug Jaundice Mental deficiency Sc h i z oph re nia Senile psychosis Phlegmatic personality Addison's disease The route of administration of these drugs depends on the time avail- able before start of anesthesia, since it is desirable that the peak of action of the pr~~dicati~ be reached or just paswd at the tima anesthesia is begun, When the medication is given h~od~~ically 90 mZnu%es is necessary far the de- velopment of ~x~~ effect, when intr~us~u~rly, 45-60 minutes, while only 10 to 15 ~nutes are needed for the peak of action after intravenous pre~di~ati~. The last is, therefore, the only efficacious route when the tlme between sc~edul~~ an operation and the start; of a~sthesi~ is short. The mal and rectal routes are both ~de~nda~le because of the maw variabla factors in ab- sorpt i on. The follwing ~e~~al~tie~ are s~~sted far ~dicat~~ before various . Nitrous oxide needs heavy premedication. Nitrous oxide is nat; a patent agent, therefore the metabolfc rate and reflex irritabilfty mu& be brought to It Lbasaf conditions" by appropriate doses of morphine or by a basal aneElfrhetiGff (Avertin) in order to produce surgical anesthesia without sacrificing adequate oxygenation, Reduction of reflex irritability and metabalio rate not on& Bsmn t the amount of nitrous oxide necemary, but also tend to reduce the oxygen re- quirements of the tissues. Cyclopropane is potent and rapid in effect, therefore need not be gm- ceded by the de~res~ant type of ~~~icati~n, but because it is cholinergic atra. pine OT aoopolamine should be administered to counteract this effect, Ether, because of' 5ts slaw onset and unpleasant imitating qualltfels should be preceded by moderate doses of the d~p~~sa~ drugs and sufficierrt atropine or ~co~o~~~e to inhibit excess secretions. XmaL, ~~ina1 or regiona3. technics am best preceded by B short acting barbiturate, and 8 mall dose of morphine, but inbibition of sacretias is not necessary unless the use of ~u~ple~~~a~ a~sthesia (ether, c~lopr~ane, i.v4 bar~~t~a~es~ is anticipated, ~opo~ine iB frequently used before local, blaok or spinal anesthesia, but it is used for its counteracting of respiratory depression and nausea from morphine, and for its production of amnesia, rather than for its effect on secretions. Intravenous barbituratee, like cyclopropane are cholinergic, and are frequently accompanied by increased secretione. Atropine or scopolamine should therefore be given before their use. Small doses of morphine to reduce pain per- ception are helpful since reeponses to pain stimuli are abolzshed only with re- latively deep barbiturate anesthesia, Oral premedication with ems11 amounts of other barbituratee is not contraindicated, but is ueually unnecessary and beat omit ted. Avertin is eseentially a depreeeant premedication, and eo should be preceded by minimal doees of morphine (for reflex depression) but the neceeattry amount of atropine or ecopolamhe should not be reduced. Suggested dosea in healthy adults are Magendie 0.3 C.C. (morphine .009 gm} + Scopolamine 0,0004 gm. Demerol 0.075 gm + Scopolamine 0.0004 gm. General princlplee of medication: 1. A combination of two depressant drugs, i.e., nembutal and morphine is more depressant than either one alone. Correct this by decreasing the dose of each. 2. Because the cambination of barbiturate, morphine and a general anesthe- - tic so often produces marked respiratory depreesion, it is better to give the barbiturate the night before operation, uslng; a medium or long acting one so that its action will be present but waning on the morning of operation. For case8 scheduled late in the morning a short-acting barbiturate (nembutal, seconal) given "on awakening" will allay anxiety, yet be past it8 peak of action when the pre-operative morphine le given, 3. Beware of using depressant drugs in patients with preexisting 18 respiratory difficulty. Such patient '6 respiratory exchange may be just adequate to keep them oxygenated without such drugs, but even slight respiratory depres- sion caused by the drugs nay lead to mvere hypoxia. Patient8 with severe hemor- rhage, anemia, asthma , cardiac decmpensation, substernal thyroids, marked e- phosis, and marked abdominal distention, are in this group, as well as those with pulmonary disease o 4. Every time a depressant drug is used, the cough reflex is diminished. me dosage of opiates necessary ta control cough is materially smaller than that neceasary to relieve pain, An active cough reflex is the best prophylaxis against respiratory complications. THINK TWICE before ordering depressant drugs. INHALATION AGENTS There are at least ten anesthetic gases and vapors. A omparison of im- portant properties of the six most common is tabulated on page 19. The anesthetic gases obey all the well-established physical gas laws, but the one of particular importance to the physiology of aneatheeia is that the direction of diffusion of a gas 18 from a region of high tension (partial pres- sure) to regions of lower tensions. This is the machanim by which gases pass from the alveoli to the blood stream and thence to the tissues when they are ad- ministered, and pass in tie reverse direction to be excreted when administration Is stopped, An important difference between the voletile agents and the nun-vola- tile one8 is that they are not changed in the body, and are quantitatively ex-. areted by the lungs. A negligfble amount diffuses through the sMn and into the sweat, urine, and other secretions, but the liver and kidneys are spared the $ metabolic work of inactivating the drugs. The significance of this mode of exom- tion :E that should overdose occur, the drug can be removed from the body by SCME PROPERTIES OF CCNMON INEALATION ANESTVE!l?IC AGElpflS CHLOROI CYCLO- N-rrROUS NAME ETHER FORM VINE!I'HENE PROPANE E'J3YIZI'?E OXIDE STABam ~. . FAIR FAIR POOR GOOD GOOD GOOD 4.1 2.42 1.45 *97 1.52 FIRE 80 EXPLOSZON ++* 0 ++++ ++++ ++++ 0 HAZAiW PCVEIICY WITHUJT OfiGEll WANT $ IN INSPIfiED AIR 4.C$ (2nd plane) MPLDITY OF INDtfc- TION - CONTROL & IIECOVERY 4- ++ ++ U++ ++++ ++++ MARGm OF SAW Depends on ability 05 anestbetist IKR. SECRETIOHS ++++ +++ ++++ +' + 0 ADVERSE METAB.%tC CHANGES +++ +U+ +++ ++ + 0 CAUSE OF DEATH liESP. CARDIAC RESP o ma. DEPrnSS. mPmss, rnPRESs* DEPrnSS. AFlJOX;LA ANOXIA ANOXIA ANOXIA ANOXIA ANOXIA Waxe prepdkations administered Intravenously can be used to produce relaxation of striated muscle and is especially indicated with the lese potent anesthetic agents. Some respiratory depression always accompanies its use and some method of assisted ventilation should always be at hand to assure proper exchange of eases. 20 artificial respiration provided that the circulation has not entirely ceased to carry the drug from the tissues to the lungs. There is more safety in using a drug which can be removed in the same way it is administered, than in using a drug which must be metabolized by the patient before li&teniag of the anesthe- sia can DCCLW. Many theories (see Goodman and Gilman, p. 32) have been advanced to explain the phenmenon of narcosis, but few are equally applicable to all types of anesthetic drws. It is most likely that the ultimate mechanism of the pro- duction of narcosis is an interference with the oxidative enzyme systems of nervous tissue. The oil-water solubility ratio of the anesthetic drug, it8 ad- sorptive properties, or its alteration of surfaoe tension may be of importance only in intermediate stepe leading to the afteration of tissue oxidation. This assumption explains why several of the theories may have coneiderable corrobora- tive evidence without being sufficientlx applicable to all drugs to permit their acceptance. It is far from established at the pmsent time that enzyme disturb- ances are the explanation of reversible cell depression (narcosie), but a shift in the relative importance of different enzyme systems is a tempting way of ex- plaining haw nerve cell activity (energy production) can be ixhibited by anes- thetic drugs without causing death of the cell. IMlALATION TECHNICS Inhalation methods as previously mentioned are the on$y ones in which the anesthetic drug can be removed frm the patient at will, and thereby are the - safest of all methods. They also allow the most accurate individualization of dosage o The follawing factors directly influence inhalation anesthesia: 21 Change in the inspired atmosphere Minute volume exchange Available alveolar surface Pat lent 's respirat my tract Efficiency of the cimulation Blood supply to various tissues Amount of adipose tissue in body Composition of the blood There are three fundamental types of inhalation technics, with nmr- ous variation; open drop, carbon dioxide absorption, and insufflation technics. The open drop method is characterized by the use of a wire mask covered thinly with layers of gauze, on which the liquid anesthetic agent is dropped and allowed to vaporize. The vapor being heavier than air, ooncentratea under and close to the mask, and is inhaled by the patient, Exhalation through the mask increases the rate of vaporization of the liquid. The carbon dioxide absorption system involves the us0 of a machine with yokes for attaching tanks of cmpressed gasee, valves to adjust the rate at which the gases escape from the tanks, a fhmeter to indicate the flaw of gas, a rubber bag to act 88 a reservoir for the gas mixture, and a canister of absorbing material (sodalime, baralyme) to absorb the carbon dioxide made by the patient . Ineufflation mthods are characterized by blowing an anesthetic mix- ture into the patient 's respiratory tract (naso-pharynx, mouth or trachea) in sufficient concentrations to maintain surgical anesthesia, after it has been induced by one of the above methods. The anesthetic mixture may be oainposed of gases delivemd frcan high presaure tanks at a mure rapid rate of flow than used with the closed system, and nay be used as vehicle8 to carry the vapor of a liq- uid drug from a reservoir to the mtient. (Exanplea: Insufflation of nitrous oxide and oxygen, &her vapor earried by a atream of oxygen.) Cmpmsaed air piped to the operatine; room from a central source, or delivered by a motor- driven pump or foot bellme, may be used instead of oxygen as the vehicle for the vapor of volatile agents. All tbree systems can be considered a6 extensions of the respiratory 22 system of the patient. The gases under the mask, in the breathing bag, or in the insufflation stream come into equilibrium with the alveolar gas concentrations after a short time. From this point, equilibrium is reached with the blood stream, and finally with the tissues. There are advantages and disadvantage of each method: PRO Open drop - 1. SSmple, portable 2. Inexpensive equipment 3. Minimal rebreathing C02 4. Minimal reaistance to breathing ,Ab sorption 1. Good control respiration 2. Re susc Itati on easy 3. Economical, anes. agent 4, Heat, water vapor preserved 5. Oxygen easily added, carbon dioxide removed Insufflation 1. Technically easy, head and neck surgery 2. Lowest rebreathing C% 3. Easy route to add 02 1. 2. 3. 4. 5. 6. 7. E;. 1. 2. 3. 4. 5. 5. C ON No control of respiration Poor set-up for resuscitation Very wasteful, anes. agent Loss of heat, and water vapor Irritating, cold vapor Always lower oxygen than air Fire hazard Skin burns, liquid ether - Initial expense hi@ Less portable; tanks of gases Can get out of order Increased temperature inspired Slight resistance to breathing Explosion hazard a ir 1,2,3,4,5, and 7 same a8 open 1 and 3 mnte as ab8~rptiOn Re la t ive ly purtab le when f oat Cif f ic ult to maintain deep drap metbad bellows type used am s th e a ia To each ayetern, an endotracheal airway, introduced througb the nose or mouth, may be added. Its advantages and disadvantages are listed below: 1. 2. 3. 4. 5. 5. PRO I_ Free airway, cc~nmon sites of ob struo t i on under c ontr ol (tongue , larynx 1 Dead apace diminished - quieter respiration, lower C02 Prevention of material from entering trachea (tube with cuff or packing) Pathway for auction established Control. of pressure in chest Ideal aet-up for resuscita- tion 1. 2. 3. 4. C ON Moderate obstruction to respf- - ration if tube too low or Possible trauma to larynx and pharynx by inexperienced Possible injury to epithelium of trachea or larm by Anesthesia must be kept deep enou& to abolish cough narrow ane sthet ist pressure of tube or cuff ref lex Indications for endotracheal airwag 1. 2. 3. 4. 5. 5. 7. 8. 9. Operations in areas of high reflex irritability: upper abdomen Operatiom on patients with high reflex irritability: alcoholics Head and neck surgery: anesthetist out of surgeon's way, but goad con- Poor risk patients: if resuscitation may be necessary; eapecially Thoracic surgery: control of pressure relations in chest; suction of Insufflation technics, delivery of agent more efficient and effective Long operations in unphysiological positions: Ex. : spinal fusion, in prone positJon. Respirations often aided by anesthetist Patients in whom an adequate airway cnanot be establi&ed and main- tained by simpler means: receding jaw, short neck, intractable In war sqery when one anesthetist must manage several general anes- trol of airway neurological patients secretions frm trachea and branchi laryngospasm thesias at once OmEER TECHNICS Rectal, Intravenous, Regional Blocks In these technics, d~ugs can be administered with comparative ease, but cannot be recovered at will. The patient destroys and excretes the metabo- lized drug at varying and wontrollable rates of speed. PRO - Reotal route Slmple, portable Painless No fire hazard (except ether) Intravenous ' Simpl.5, portable Minimal pain No fire hazard Quick induction Quick recovery Inte'rmittent dosage quite accurate Good supplement for blocks C ON c_ Unpre dic tab le ab s orpt i on Variation in rectal preparation Sph inc t er re laxat i on Needs cooperative patient Rectal patholaigy Long recovery period, requiring constant nursing care Narrow margin of safety Overdose of drug easy No control of respiration ' Only light anesthesia obtainable May need help to keep free airway (two people desirable) 24 Nerve Blocks Excellent re laxation No fire hazard Portable Need cooperation (children Minima 1 metabolic Special knowledge and training Limited duration of' block dif f io ult ) disturbance because of anesthesia POsSible damage to nerve of limited area Avertin overdose results in marked ciroulatory and respiratory depres- sion (more of depth than rate). Treat with pressor drugs (ephedrine, neosyne- phrine) and oxygen. Pentothal overdose results in apnea with variable degrees of circula- tory depression. Treat with artificial respiration with oxygen. Analeptic drugs (coramine, benzedrine, metrazol, picrotoxin) are advisable only when overdose is known to be large since smaller doses of pentothal my be metabolized quickly and the patient then may have an overdose of the analeptic. Procaine "reaction" frm overdose or intravenous injection results in one of two syndromes: 1. Marked blood pressure drop, bradycardia, pallor, nausea and vcnniting. Treat with pressor drugs (ephsdrine, neosynephrine ) and oxygen. 2. Increased C .N.S. stimulation: apprehension, reetle~~~ness, convuleions afid hypoventilation from spasm of respiratory muscles. Treat with intravenous barbiturate and oxygen (artificial respiration if necessary) . Prevent by proper premedication. PRO cc Simple technic, portable Non -explosive Excellent re laxat ion Minima 1 me tab olio changes CON - Numerous uncontrollable factors Drug cannot be recovered C irc ula t or y de pre as ion f req uent Pos8ible nerve root damage Late recovery of active intercostale Shwk more eevere after hemorrhage 25 LI 8 8 d 0 x h d d x 9 m 26 Factors concerned in the DURATION and HE^^ of spinal anesthesia Controllable Urn ontrollab le Space of injection Speed of injection Volume of solution used Dosage of drug Specific gravity 601. Posit ion of patient Choice of drug Diffusion Circulation cf spinal fluid Movemnt of fluid by respirations Length of spine Previous pathology or anmalies Movement of patient and pulsations Change CSF pressure by straining Breaking needles during a dmini stra t i on DRUGS used: Procaine.. . . . .short acting, but least toxic Monocaine . . . . .isomer of procaine Metycaine.. . . .longer acting than procaine Pontocaine. . . .long acting, 1OX more toxic 11 than procaine II 11 Nupercaine . . . . I' I' , 20x Glucose or alcohol may bo added to tbe ffrst four drugs to make the solution hyper- or hypobaric. Nupercaine is slightly hyperbaric in the 1:200 solution, and may have glucose added; it is hypobaric in the 1:1500 solution. Continuous or intermittent method of administration allows for much more accurate dosage, and es8ures adequate anesthesia until end of operation. Severe respiratory depression frmn too high a level oan be avoided entirely. Circulatory depression, hawever, has not been avoided by the continuous method. some of the Taotors in the production of circulatory depreseion by spinal anesthesia during surgery, are listwa below: 1. 2. 3. 4. 5. 6. 7. 9. 10 . a. Relaxation of skeletal muscles, followed by poorer venous return. Vasodilatation of blood vossels in the anesthetized regime. Stagnation of blood in tAe peripfieral vaecolar bed. Dbinished thoracic excursion frm partly paralyzed intercostal muscles caueiw dieturbance of preseure relations and poor venoue return to heart. Eypaxia of myocardium. ?Toxic'' effect of anesthetic drug itself. Accentuated vagotonic response to traction, due to autonomic imbalance Poor adjustment to change in position. Poor canpensation to changes in blood volume (hemorrhage). Decreased adrenalin output. (Adrenals functionally denervated.) resulting frm anesthetized splanchnic nerves. Treatment is best prophylactic, by use of a vasopressor drug, which may act at one of three sites, the vaaanotor oantsr, the heart muscle, or on the blood veesels peripherally. The best vasopressor drug is ephedrine, because of its sustained action, and minimal toxic effects. Other drugs in use for this purpose are neospephrine, benzedrine, cobefrin and paredrine . After the drop in pressure has occurred, treatment should be directed toward providing ample oxygenation for the brain and heart muscle. 1. 2, 3. 4. 5. Fluid therapy: blood, plasma or salipe, as indicated Head down position (if hyperbaric drug has not been added to subarach- Oxygen, bg insufflation or closed inhalation system Restoration of normal ventilation by manual methods Additional doses of pressor drug noid space recently) Retchin6 is a cmon and troublesome complication of spinal anesthesia. It may be caused by: 1. Intraabdcaninal traction 2. Hypoxia due to: a. Marked blood preasure fall b . Respiratory paralysis c. Overdose premedication 3. Reaction to premedication (morphine) 4. Psychic a. Inadvertent seeing of blood on drapes b. Odor of "prep" ether - odor of cautery C. Anxiety Reaction to spinal drug (only with very laree doses) 5. Treatment of retching .under spinal anesthesia depends on the cauee. For 1: Exert traction as slowly and gently as pos6ibb. Depress reflex irritability with morphine or light general aneethesia. For 2: Sapply oxygen: artificial respiration with mask and bag if tidal volume is too small or paralysis cmplete. For 3: Scopolamine or atropine may help. (1 part:25 parts morphine) add treat as for $+. For 4: Any treatment that distracts patient will help: deep breathing, ice water cmpress to forebead, aromatic apirita of ammonia, etc o For 5: As for procaine overdose. 28 POSTOPERATIVE PULMONARY COMPLICATIONS Pulmonary complications f olluwing anesthesia and surgeryf om the most frequent and most serious type of morbidity and mortality, Many factors cmtrib- ute to their incidence, but most revolve around the ineffectual removal of 88- cretions from the tracheobronchial tree. Under normal conditions, secretions are constantly produced in this tract, are in part dried by the air currents, and in part removed by the action of the ciliated epithelium, as well as by the peri- staltic action of the bronchial musculature. Both these actions are inhibited by anesthetic agents, and by therapeutic doees of morphine. The defense of the pa- tient against accumulated secretions is further weakened by the presence of an ineffective cou&. The f ollming circumstances contribute to its ineffectiveness. 1. 2. 3. 4. Inability to inspire deeply Splinting of abdominal musoles inhlbiting motion of diaphragm Pam.1ysi.s or paresis of interoostals following spinal anesthesia Fluid or air below diaphragm, or in chest Tight binders Prone, or lateral position IFhrenicect qr Bronch ospaLm Too much postoperative medication (morphine) Irresponsive central nervous system Weak, exhausted patient, senility Inability to tighten abdominal lnuscles Post- spinal paresis Avitaminosis Eefect in chest wall (thoracuplasty) Open glottis (endotracheal tube) ; tracheotmy Inadequate cough reflex Ventral herniae, diastasis f Inability to produce positive pressure in chest The ptient; most likely to develop postoperative pulmonary cmplica- tims are those with : 1. 2. Chronic respiratory infection, with sputum: chronic bronchitis and 3 . Upper abdominal operations 4, Neurological operations 5. Previous history of pulmonar=. camplication, especially postoperative pne monia emph yseme Long period of irmnob$lity in imnediate postoperative period: plaster mat, or poor nursing car0 1. 2. 3. 4. 5. 7. / 3. 1. 2. 3. 4. 5- 6. 7. 8. 6. Alcabolic history 7. 8. Operations of over three hours' duration Presence of shock dur3.ng operation or in postoperative period The two types of pathology which dovelop are: 1. Atelectasis: patchy or confined to one lobe, or one lung. The origin of the atelectasis is most frequently obstruction by mucous plugs lodged in the major bronchi, or in smaller divisions of the bronchi. The obstruction my ab0 be caused by reflex bronchospaam. The gases in the lung distal to the obstruc- tion are absorbed into the blood stream, %he alveoli becme airless, and the solid area of lung thus produced is a perfect field for the development of in, fections, or 2. Bronchopneumonia: the causative organisms of this complication may be thoae present in the lower tract before operation, or ones aspirated during an- esthesia. Aapiratian of vcanitus almost as6ures development of pnemonia, not so much because of the bacteria present in this instance, but because the chemical irritation fram the hydrochloric acid predisposes to infection. Prophylactic treatment before operation consists of Preventing secretions by use of belladonna group. Minimal use of belladonna group if secretions already present. Postural drainage to remove sputum; occasionally bronchoecopy. Afternoon operations far thoracic surgery. Choice of non-irritating anesthotfc agent . Good ore1 hygiene, Ernpty stomach before operation. Prophylactic treatment at end of operation consists of ?rei%2nce of cough reflex before patient k3aVeS operating row-. Removal of secretions by aspiration, and stimulation of cough reflex. Mhbw1 postoperative medication for pain relief. Byperventilation, by voluntary deep breathing, or by carbm dioxide Frequent change in positiolr. Head dwn position until patient conscious. ~tercoatal. block in upper abdcminal cases. Use of non-diffusible gas at end of anesthesia (air or helium). inhalations ( ~OO$ air) if patient uncooperative . Treatment if atelectasis oocurs: 1. 2. 3. 4. 5. 6. Change in position, with affected lung uppermost. Hyperventilation in several positions. Assistance with expiration by judioious pounding on chest. Aspiration of trachea with catheter, and 8tUulation of cough reflex. Bronchoscopy, if above are inadequate . Pen; ci llin therapy . The incidence of explosions with ethylene, cyclopropane and ether is rou@ly between l:lOO,OOO and 1:500,000 cases. Statistically this is one of the most unimportant anesthesia cmplications, but it should be zero. The cantroversy between safety of a cmpletely grounded operating room VB. room completely isolated fram ground still continues. Other questions under investigation involve the use of conductive rubber, the use of inert gases with explosive gases to make them non-explosive, and the true nature of statio electricity. Air conditioning, by raising the humidity in the operating room, permits partiel distribution of statio cbargea so that sparks are less apt to pas8 between points of different potentials. If the atmosphere has been mebed free of C02 by the air conditioning, however, even very humid air will not prevent sparks . All the inhalation agents except nitrous oxide and chloroform are exploaive in the ranges in which we use them. A few common sense principles ap- ply to their we: 1. If' the use of electrical equipment is imperative far the surgery, ohoose a non-explosive agent : nitrous oxide, with ample premedication; in$ra- venous barbiturate, spinal, nerve block or local infiltration, or coanbinations of` these technics. 2. If explosive agents are being used, avoid using electrical equipment; i.e . , carbolic knife for severing appendix instead of cautery. 31 3. The danger zone with these drugs,,is at ana near the face mask. It is the mixture leaking at the face mask which is hazardous, not blood or tissues contalnia the agent. If electrical equipment must be used at a distance frcnn the face', partla1 protection may be afforded by heping fit of the mask as tight as possible, or enclosing the area in a wet towel. 4. It is believed widely that dapger is minimized if the patient, machine and ahesthetist are kept at the same electrical potential by using an inter- coupler between these three - This proteats only against static electricity, and is entirely useless for sparks from a cautery, coagulating machine, or X-ray apparatus, and similar electrical equipment. 5. Members of the operating rom staff, visitors and bystanders should avoid brushing past the anesthesia machine or bumping it with metal obJects, such as spotlights, and portable tables. 5. Elncwn sources of static slectricity, such as wool blankets and wool, @ilk or rayon outer garments should be prohibited frm the operating roan. RESUSCITATION A €ew general prlnciples apply to any type of Pesusoltation done for any Hason by any of a number of techpics. I, There must be a FIE3 AW4Y. Artificial respiration is futile unless the airway is patent. Explore mouth with finger, remove foreign bodies. Remove fluids by gravity: head dawn position. Elevate chin, turn In lateral or prone positim to keep tongue frm obstructing airway. Introduce pharyngeal or endotracheal airway if available . Po tracheotomy, if above not avaihbb. 32 2. The patient must be ventilated. There is no way to store oxygen. It must be supplied bmedfately. Prone prensure method, or mouth to mouth respira- tion are always available, 3. The patient is in shock. Warmth and head dawn position should be sup- plied. 4. Stimulating drugs are of NO USE unless the patient is well oxygenated.