16 Complications in Anaesthesia.pdf

8/13/2019 16 Complications in Anaesthesia.pdf

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Department of AnaesthesiaUniversity of Cape Town

Lecture 16

Complications in Anaesthesia

Modern anaesthesia in a first world environment, administered by a trained anaesthesiologist, isremarkably safe. In South Africa relatively untrained medical officers are often required toanaesthetise patients in rural areas. Knowledge of potential complications of anaesthesia is importantas the majority can be avoided by a good pre-operative assessment and adequate planning.Complications may be divided into minor(non life-threatening) and major(life-threatening).

Minor complications

Although minor complications are not life threatening, they may be very important to the patient andsome may have the potential for litigation.

1) Airway injuriesInjuries to the mouth, throat and teeth can be caused by placement of a laryngoscope blade,oropharyngeal airway, laryngeal mask airway (LMA) or endotracheal tube (ETT). Patients dentitionmust always be examined pre-operatively and precautions taken if risks are high e.g. expensive bridgework or loose teeth. A gum guard may be used and laryngoscopy should be performed with extracare. The correct size ETT and careful placement will prevent damage to vocal cords. Avoid overinflation of the cuff as this can cause oedema and post-operative intubation stridor; and in the long-term, tracheal stenosis. The use of cuffed ETTs is controversial in children under the age of 8 years.Select the correct size of oropharyngeal airway and LMA to avoid trauma of the posterior pharynx.

2) Eye injuriesFacemasks should fit properly and avoid pressure on eyes. Anaesthesia obtunds the corneal reflexand paralysed patients are unable to blink. Corneal ulceration will occur if eyes are not taped closedduring anaesthesia. When in the prone position, eyes should be checked regularly to ensure that theyare free from pressure. Eyes should be padded before taped shut for head and neck surgery.

3) Positional injur ies

Improper positioning of patients allowing pressure on peripheral nerves can lead to nerve damage;particularly those nerves passing over bony prominences. Nerves at risk include the radial nerve(Saturday night palsy); ulnar nerve; brachial plexus from hyperextending the arm beyond 90 degrees;the lateral popliteal nerve in the lithotomy position (foot drop); and the femoral nerve can be damagedduring surgery in the Lloyd-Davis (extended lithotomy) position. During long procedures, pressurepoints should be padded to avoid the development of pressure sores and the limbs moved from timeto time by the anaesthetist if possible.

4) Complications of regional anaesthesiaSpinal and epidural anaesthesia are not without risk. Without meticulous attention to asepsis andproper technique, several complications can occur: epidural abscess, meningitis, epiduralhaematoma, and nerve injuries may follow. These are fortunately very rare and also not minor if theydo occur. Post-spinal headache is a common complication and can be reduced by using a pencil

point needle (e.g. Whitacre or Sprotte) and a smaller gauge (25 Gversus 22 G). Neuraxialanaesthesia often causes hypotension which is easily managed, however it can also lead to profoundhypotension if volume of local anaesthetic was too high or patient is volume depleted. A high spinal isa risk for respiratory depression and cardiovascular collapse, and even an anaesthesia-related death!

5) Complications of central venous cannulation

Early complications Late complications

TechnicalPneumothoraxHaemothoraxNerve damage

InfectionSepsisEndocarditis

Dysrhythmias (from guide wire) Thrombosis

Air embolism (patient should be head down) Tamponade


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Complications in anaesthesia

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6) Post-operative nausea and vomiting (PONV)PONV is common. Some patients with a history of severe PONV fear this complication more thanany other, including post-operative pain. Do not confuse the risks for and treatment of PONV with therisks of a full stomach and resultant aspiration. These are two very different complications. There arepatient, surgical and anaestheticfactors which increase the likelihood of PONV.

Risk factors for PONV

Patient factorsChildren, females, history of motion sickness, previous PONV, obesity.

Anaesthetic factorsProlonged preoperative starvation.Hypotension with spinals or epidurals.Emetic drugs: Opiates, Etomidate, Ketamine, N2O and all volatile anaesthetic agents.

Surgical factorsEar and eye surgery, especially strabismus (squint) surgery, intra-abdominal surgery,laparoscopy, gynaecological surgery, orchidopexy.

Post op factorsPain, opiates, forced oral fluids too soon, hypotension.

Prevent or reduce the incidence of PONV by avoiding emeticdrugs e.g. Etomidate, Ketamine, N2O,opiates and volatile anaesthetic agents. Regional anaesthesia is an option if appropriate as it avoidsmost of these drugs; and Propofol total intravenous anaesthesia (TIVA) is a good method for providinggeneral anaesthesia. Propofol has intrinsic anti-emetic properties.

Pharmacological management includes the administration of commonly used anti-emetic drugsintheatre: e.g. Droperidol (Inapsin

) a butyrophenone; Prochlorperazine (Stemetil

) a phenothiazine;

Ondansetron (serotonin3antagonists) or Dexamethasone (steroids). Metoclopramide (Maxolon), a

dopamine agonist, is also commonly used post-operatively, however, it is a poor anti-emeticand isreally a pro-kinetic, better used to promote gastric emptying in patients with a full stomach. Routinepharmacological prophylaxis is not indicated and should be reserved for high-risk patients. In high-risk

patients, prophylaxis with Dexamethasone and Droperidol are a good combination. Dexamethasoneis a prophylacticmeasure and will not be effectivepost-operation for treatment of vomiting.Ondansetron and the other serotonin antagonists, or Prochlorperazine are used post-operatively.

Non-pharmacological management includes keeping the patient well-hydrated with intravenousfluids; and several complementary and alternative therapies including the use of acupuncture pointbracelets and ginger. Interestingly, smoking is protective against PONV!

7) AwarenessAwareness under anaesthesia is the ability to recall events occurring during general anaesthesia.Hearing is the last sense to disappear under anaesthesia. Anaesthetists rely on clinical observation ofmotor movement and sympathetic nervous system stimulation (hypertension, tachycardia, sweating ortearing) to assess the depth of anaesthesia. Motor movement will be masked by muscle relaxants

and sympathetic signs modified by beta-blockers and opiates. Objective methods to measureawareness using processed electro-encephalogram (EEG) data have been developed, but are notalways available.

Causes of awareness include faulty equipment and light anaesthesia. Awareness due to inadequatevolatile agent is reduced by the use of an anaesthetic agent analyser to measure the concentration ofthe anaesthetic agent in the breathing circuit. Benzodiazepines are also extremely useful due to theirability to cause antero-grade amnesia.

Awareness is an extremely uncommon event and the incidence ranges from 1 in 10 000 for consciousawareness with pain; to 1 in 1 000 people being able to report some awareness in the post-operativeinterview, although not in any way distressing. The first type where the patient is fully aware whilebeing paralysedand feels painis the worst scenario and can lead to the patient developing post-traumatic stress disorder. These patients should be followed up regularly, and referred for psychiatric

help if necessary.


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2) AspirationThis topic is thoroughly dealt with in the Emergency Anaesthesiachapter. Peri-operative aspiration ofgastric contents can cause a chemical pneumonitis (Mendelsons syndrome), and result in thepotentially fatal acute respiratory distress syndrome (ARDS). Patients at risk include those with a fullstomach, ileus, acute abdomen, hiatus hernia, pregnancy, obesity and particularly in gastric outletobstruction. Patients should be starved of food for 6 hours and of clear fluid for at least 2 hours prior

to elective surgery. Trauma may delay gastric emptying for many hours.Strategies to reduce risk of aspiration include lowering gastric pH with sodium citrate 30 mlor H2-receptor antagonists (e.g. Ranitidine); increase gastric emptying plus the lower oesophageal sphinctertone with Metoclopramide; and reduce gastric volume via suction with a nasogastric tube. All patientsat risk of aspiration should be intubated using a rapid sequence induction (RSI) with pre-oxygenationand cricoid pressure. After surgery, such patients should remain intubated until consciousness hasbeen regained and airway reflexes returned.

3) Respiratory complications\Once again, these can be due to patient, anaesthetic or surgical factors. A brief overview will begiven, also refer to the chapter onAnaesthesia for Respiratory Disease. The majority of thesecomplications end in one final common pathway: Hypoxia.

a) Laryngospasm

Causeso Insertion of an ETT, LMA or oral airway while still in a light plane of anaesthesia.o Inhalation of irritating gases (Isoflurane and Desflurane).o Secretions on the vocal cords.o Surgical stimulus e.g. dilatation of the cervix or anal sphincter.o Surgical stimulus during light level of anaesthesia.

Managemento Avoid manipulation of the airway while deeply anaesthetised (stage 2 + 3).o Stop the causative stimulus.o 100 % O2with facemask and positive pressure ventilationis often all that is needed.o A small bolus of Propofol (10

50 mg) is very helpful.

o Consider spraying cords with 2 % Lignocaine using the MacIntosh sprayer.o If fast control is needed, give Suxamethonium 1 mg kg

-1and intubate.

If the laryngospasm has occurred during emergence, then give only one-quarter of theusual dose of Suxamethonium to avoid prolonged paralysis..

b) Bronchospasm

Causeso Same causes as for laryngospasm, plus the following:o Pushing the ETT too deep with carinal stimulation can precipitate bronchospasm.o Asthmatics, chronic bronchitis or recent chest infection.o Histamine release from certain drugs, e.g. Morphine, Thiopentone, Suxamethonium, and

certain non-depolarising muscle relaxants (Atracurium).o Anaphylactic reaction.

Managemento Avoid elective surgery if underlying respiratory condition not optimised.o Consider regional techniques in high risk patients.o Stop precipitating cause. Give 100 % Oxygen.o Deepen anaesthesia with non-irritating inhalational agent.o Inhaled or intravenous 2-stimulant e.g. Salbutamol.o Once again a small dose of Propofol is very useful.o In resistant cases IV Aminophylline and Ketamine may be considered.


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c) Obstruction

Causeso In the ventilatory circuit, including the endotracheal tube.o In the airway from the oropharynx to the bronchi e.g. mucous plug or foreign body.o During spontaneous ventilation with facemask, the tongue may obstruct the oropharynx

when loss of tone occurs with anaesthesia.

Managemento Jaw thrust and chin lift during facemask anaesthetic.o Check all tubing for kinking, compression and foreign bodies.o Examine ETT for the same as well as cuff herniation.o Pass suction catheter down ETT to check patency and suction out secretions.o Ensure that the throat pack, blood or vomitus are cleared from the pharynx at the end.o Insert oral airway to prevent patient biting down on ETT at the end of the procedure as

well as post extubation if level of consciousness still low.

d) Post-operative respiratory depression and hypoventilation

Causeso Residual anaesthetic agents e.g. opioids or inhalational anaesthetic agent.o

Incomplete reversal of muscle relaxants.o Hypoglycaemia.o Electrolyte disturbances.o Central depression due to neurological damage e.g. stroke.o Partial airway obstruction.o Severe pain after abdominal surgery or abdominal distension.o High blockade after epidural or spinal anaesthesia could also cause hypoventilation.

Managemento Jaw thrust and chin lift.o Exclude and treat above causes.o Be careful of just giving patient Oxygen with a facemask; Good O2saturation on the

pulse oximeter is not an indication of adequate ventilation, and may mask dangeroushypoventilation.

o Assist ventilation until patient is making adequate breathing efforts.

e) Pneumothorax

Causeso Pre-existing due to trauma.o Attempts at central venous cannulation.o Surgery involving the diaphragm or thoracic cavity.o Barotrauma due to excessive PEEP

/peak airway pressures during assisted ventilation.

o Spontaneous rupture especially in patients with bullous lung disease.

Managemento Use low ventilatory pressures or spontaneous ventilation in high-risk patients.o Have high index of suspicion.

o Insert intercostal drain if needed.


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4) Cardiovascular complications

a) HypotensionMost anaesthetic agents tend to lower blood pressure (except Ketamine). In healthy patients, adecline to 20

30 % of the pre-operative blood pressure is acceptable. If the BP falls more than

this, cerebral and myocardial oxygenation become compromised. In patients with compromisedcirculations e.g. ischaemic heart disease, more meticulous pressure control is needed.

Causeso Overdose of anaesthetic agents e.g. premedication, induction agents, opioids,

inhalational agents.o Spinal and epidural anaesthesia through vasodilatation due to sympathetic block.o Hypovolaemia due to bleeding, starvation, evaporation and third space losses from

surgical field, and preoperative diuretic use.o Pre-operative -blocker therapy compounds the drop in pressure due to other causes.o Increased intrathoracic pressure due to high ventilation pressures can decrease venous

return, and therefore cardiac output.o Septic shock.o Anaphylactic reactions.

Managemento Evaluate the clinical scenario and treat the cause.o Elevate the legs if appropriate and possible during the surgery; or tilt the whole table

head down; improving the venous return.o Decrease anaesthetic agent administration.o Volume load appropriately with crystalloids or colloids.o Vasopressor therapy e.g. Ephedrine, Phenylephrine or inotropes where appropriate.

b) Hypertension

Causeso Sympathetic stimulation during laryngoscopy and intubation especially in a known

hypertensive patient.o Hypercarbia due to hypoventilation.o

Insufficient analgesia or anaesthetic agent.o Essential hypertension.o Hyperthyroidism.o Phaeochromocytoma.o Drug administration error e.g. Ephedrine or Adrenaline instead of another drug. Always

check your ampoules carefully for name, dose and expiry date.

Managemento Treat cause.o Increase depth of anaesthesia.o Analgesia if needed.o Antihypertensives where indicated e.g. -blockers (Labetalol, Esmolol), nitrates, Mg

2+.

c) Dysrhythmias and cardiac arrest

Dyshythmias occur in 1 % of all anaesthetics and are mostly benign. It is important torecognise life-threatening dysrhythmias and treat them appropriately.

Causeso Drugs, e.g. Halothane increases sensitivity of cardiac conduction system to

catecholamines. It is the most dysrhythmogenic volatile.o Electrolyte abnormalities especially hyperkalaemia.o Sympathetic or parasympathetic stimulation e.g. intubation, peritoneal stretching.o Underlying heart disease.

Managemento Identify high risk patients preoperatively and review need for pacemaker.o Treat the cause.o Use appropriate anti-dysrhythmic drugs.o Check and know how to operate defibrillator preoperatively. Follow the advanced life

support (ALS) guidelines for life-threatening dysrhythmias and cardiac arrest.Refer to the lecture on CPR and the algorithms at the back of the book.


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d) Myocardial infarction

These factors have been shown to increase the likelihood of peri-operative myocardial infarction.

Patient factorso Cardiac diseaseo Peripheral vascular diseaseo Hypovolaemiao Acute coronary syndromeo Decompensated CCFo Dysrhythmiaso Severe valvular heart disease

Anaesthetic factorso Hypotensiono Hypertensiono Tachycardiao Hypoxia

Surgical factors: Types of surgeryo Intrathoracico Abdominalo Vascular surgeryo Emergency surgery

Managemento Identify high risk patients preoperatively and order appropriate special investigations e.g.

stress test, angiography where indicated.o Postpone elective surgery until patient optimised.o Postpone elective surgery for 6 months after an acute coronary event.o Optimise O2supply

:demand ratio by optimising Hb, O2administration, HR and BP.

o Keep HR controlled with preoperative -blocker therapy and anxiolytic premed, adequateanalgesia and fluid therapy.

o Reduce afterload with analgesia, inhalational agents and nitrates where appropriate.

5) Equipment failureThe anaesthetic machine, ventilator, tubing, vaporisers, intubation equipment, wiring, and monitorscan all malfunction. Faulty equipment or lack of essential equipment can lead to disastrous outcomessuch as failure to ventilate, hypoxia, awareness, electrical shock and burns. All equipment must bechecked prior to an anaesthetic. Warning alarms should be in place such as an Oxygen failure alarmand Oxygen analyser. Monitoring alarms should be set to detect any adverse clinical parameters andabnormal ventilatory pressures. A self-inflating emergency resuscitator (e.g. Ambubag) and anOxygen cylinder should be available in case of ventilator failure. Equipment must be serviced andcalibrated at appropriate intervals.

6) AnaphylaxisAnaphylactic reactions are a potential hazard of any anaesthetic. Anaphylaxis is a type Ihypersensitivity reaction. The Ig E molecules on the mast cells and basophils recognise the allergen(antigen) and when the Ig E become cross-linked by this antigen, the final common pathway isdegranulation of mast cells or basophils and the release of potent preformed substances such ashistamine, and newly formed substances such as arachadonic acid metabolites.

The clinical presentation is a classic triadof skinreactions, plus respiratoryand cardiovascularinvolvement. Signs include a wheal and flare skin reaction with urticaria; respiratory involvementincludes angioedema (upper airway swelling), bronchospasm and hypoxia; cardiovascular effectsranges from hypotension and tachycardia to cardiovascular collapse and in severe cases a cardio-respiratory arrest. Not all anaphylactic reactions present with all three of the triad; and there is greatvariation in severity from the very mild to severe with a cardiac arrest unresponsive to resuscitation.

Anaesthetists frequently administer a number of drugs intravenously within a short space of time. Thedrugs most likely to cause anaphylactic reactions are the antibiotics and muscle relaxants(especially Suxamethonium and the benzylisoquinolinium non-depolarising muscle relaxants). Other

potential antigens include the induction agents (Thiopentone, Propofol), opiates, local anaesthetics(esters more than amides), colloids (not crystalloids), blood, and latex. Volatiles do not causeanaphylaxis.


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Emergency management involves theA B Cs, call ing for helpand the administration ofAdrenaline.The dose depends on the severity of the presentation. In an arrest, follow the Resuscitation Council ofSouth Africa (RCSA) guidelines for anaphylaxisattached and give 1 mgIV and start CPR. If the BP islow, titrate smaller doses of adrenaline to effect dilute 1 mg(1 amp) of adrenaline into 10 mlandgive

1 ml(50

100 g) at a time. The RCSA guidelinessuggest the intramuscularadministration

of Adrenaline; however in the situation of a cardiovascular collapse the IM dose of Adrenaline will

not work quickly due to peripheral shutdown. You will have IV access in theatre so it is the superiorroute of administration.

Further management includes aggressive IVfluidreplacement with crystalloid or colloid (if a colloidprecipitated the reaction, use a different colloid). Steroid (Hydrocortisone 100 mgIV) and abronchodilator will help with bronchospasm, but these will take some time to work and they aresecond line treatment. Do not delay administration of Adrenaline. Airway oedema may be significantand there may be a need for prolonged ventilation. Do not extubate if uncertain. If the patient isunstable and requires ongoing ventilatory and inotropic support they should be admitted to the ICU.

The diagnosis of an anaphylactic reaction can be confirmed by the presence of mast cell tryptase inserial blood samples. Patients should be referred to an allergy clinic to determine the drug thatcaused the anaphylactic reaction, a Medic-Alert bracelet issued and the patients GP informed.

7) Pharmacogenetic DiseasesPharmacogenetic diseases are genetic diseases that are unmasked by exposure to specific drugs.Several of these have particular relevance to anaesthesia.

a) Malignant hyperthermia (MH)

DefinitionA rare inherited syndrome characterised by a life threatening acute hypermetabolic state triggeredby exposure to a triggering agent: all volatile anaesthetic agentsor Suxamethonium. It iscaused by a defect in a receptor on the sarcoplasmic reticulum called the Ryanodine receptor.This is a calcium channel receptor. Once exposed to the trigger agent, the receptor stays openand floods the cell with calcium with a resultant persistent contractile state. Hyperthermia isdefined as a core temperature above 38 C, although this is a late sign with MH.

Clinical features (in order of presentation):o Tachycardia.o Tachypnoea if breathing spontaneously.o Increased O2consumption, and eventually cyanosis.o Hypercapnia with PetCO2rising to >

3 x normal and the baseline rises as Soda lime is

overwhelmed.o Masseter muscle spasm and whole body skeletal muscle rigidity.o Dysrhythmias and cardiovascular collapse.o High temperature is a latesign. The term malignant hyperthermiais a misnomer.o Metabolic and respiratory acidosis.o Hyperkalaemia.o Myoglobinuria.o Untreated, it is likely to progress to acute renal failure, hepatic failure, coagulopathy,

cerebral oedema and death. If diagnosed early however, it is fully treatable.

MALIGNANT HYPERTHERMIA MANAGEMENT PROTOCOL

Discontinue volatile anaesthetic and Suxamethonium

Call for help!!

Hyperventilate with 100 % Oxygen at high flows

Mix Dantrolene sodiumwith sterile water and administer 2,5 mg kg-1

IV ASAP

Institute cooling measures

Treat complications such as dysrhythmias, hyperkalaemia, and acidosis

Administer additional doses of Dantrolene if needed.(Dantrolene is a type of centrally acting muscle relaxant, and once administeredthe patient will have weakness and must therefore be ventilated)

Transfer to ICU


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DiagnosisDefinitive diagnosis can be made after the event with a muscle biopsy. This is now rarelyperformed as it is difficult to do. If the patient has a family history of malignant hyperthermia thena diagnosis is presumed and a MH-safe anaesthetic is performed.

MH-safe anaesthesiao Avoid general anaesthesia entirely and choose a regional technique.o If GA is needed:

Patient should be first on the list. Use an anaesthetic machine that has no vaporisers on it to prevent inadvertent

administration of volatile. The machine should be flushed with high-flow O2for 20minutes prior to the anaesthetic.

A Propofol TIVA technique is ideal. For muscle relaxation: Non-depolarising muscle relaxants are safe. Know where the Dantrolene is kept in your hospital usually locked up.

b) Halothane Hepatit isIn 1

:35 000 anaesthetics metabolites of halothane can trigger fatal fulminant hepatitis via an

immune mediated mechanism (type 2 hypersensitivity reaction). This rare condition is morecommon after repeat exposure to Halothane within 6 months. For this reason repeat Halothaneanaesthetics should not be administered within 6 months of a previous Halothane anaesthetic.Additional risk factors include middle age, females, obesity, and existing hepatic diseases.Hepatitis is more likely to occur with Halothane than with other volatile gents as it undergoes 20 %metabolism and the others much less so. Isoflurane and Desflurane have been implicated incausing fulminant hepatitis, although much less frequently, presumably because of the lowermetabolism in the body.

c) PorphyriaA pharmacogenetic disease involving porphyrin metabolismin which certain drugs such asbarbiturates (Thiopentone) can precipitate an acute attack resulting in paralysis, abdominal painand even death. South Africa has a relatively high incidence of the variegata form, especially inpatients of Dutch

/Afrikaner descent (butnot unknown in the English speaking population). The

acute Swedish type is also found our population. Most patients are aware of the presence of thedisease in their family and this must be ascertained at the pre-operative assessment.

If confronted with a patient at risk of having the disease, consult one of the safe/use with caution

/

unsafe drug lists and plan accordingly.

d) Scoline apnoeaSusceptible individuals have an abnormal or absent pseudocholinesterase enzymeresulting inprolonged paralysis after a single dose of suxamethonium (Scoline

/Succinylcholine).

Homozygous patients for the condition will need to be sedated and ventilated for several hoursafter administration of Suxamethonium. The missing enzyme is found in the plasma, therefore tospeed up recovery you may administer fresh frozen plasma (FFP), but this is a blood product and itdoes have the same risks as a blood transfusion. You will have to weigh up the risks and benefits.

Always check for recovery from Suxamethonium before administering a non-depolarising muscle

relaxant. The patient should show return of twitches on the nerve stimulator or signs of breathing.If you dont do this, at the end of the case when the patient remains paralysed with no twitches onthe nerves stimulator, you will not know whether it is due to the Suxamethonium or the non-depolarising muscle relaxant.

On discharge the patient should be fully informed and be given a Medic-Alert bracelet.

Documentation

Documentation is of the utmost importance whenever a complication or critical incident has occurred.Document clinical parameters as well as management. Precaution to prevent complications shouldalso be documented on the anaesthetic chart such as: eyes checked

/taped, pressure points padded

and protected and special dentition noted. Patients should be notified post-operatively of

complications that can recur with a subsequent anaesthetic. Please remember to practise medicinewith medical insurance.


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16 Complications in Anaesthesia.pdf