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Common anaesthetic emergencies and complications (Common respiratory…
Common anaesthetic emergencies and complications
Common
respiratory
complications
Hypercapnia
Detection
Capnography
Arterial blood gas analysis
Associated with hypoventilation
Reduced minute ventilation
Diaphragmatic compression
Muscular weakness
Hypothermia
Drugs
High intra-abdominal pressure
Intrathorvacic reasons
Equipment failure
Exhausted carbon dioxide absorber
Malfunctioning unidirectional valves
Treatment
IPPV
Address the underlying cause
Decrease the anaesthetic depth when possible
Reverse respiratory depressant drugs (or decrease their use)
Treat hypothermia
Reduce abdominal compression on the lungs
Check equipment
Hypoxaemia
Cyanosis of mucous membranes (late sign)
Pulse oximetry
Arterial blood gas analysis
This must be checked to determine if true hypoxaemia is present.
Aetiology
Ventilation/perfusion mismatch
Atelectasis
Shunt
Decreased CO to lungs
Pre-existing lung/thoracic conditions
pneumonia
pleural effusion
lung oedema
Failure to deliver oxygen
empty tank
malfunctioning flowmeters
wrong hose connection
Treatment
Address/treat underlying cause
Ventilation strategies
recruitment manœuvre
PEEP
Increased MV
Increase FiO2
Improve CO
Fluids
Vasopressors
Inotropes
Change position e.g. sternal v dorsal recumbency
Check equipment
Bronchodilators
Hyperventilation (=hypocapnia)
Detect with capnography and arterial blood gas analysis
Aetiology
Inadequate anaesthetic depth
Pain
Compensation for metabolic acidosis
diabetes
renal failure
profuse diarrhoea
poisoning
Hypoxaemia/anaemia
Hyperthermia
Treatment
Treat the cause!
Increase the depth of anaesthesia (consciousness?)
re-address the analgesic therapy (pain?)
Check unidirectional valves and oxygen flow (hypoxia?)
Adress haematological issues (anaemia?)
Correct acid-base status (metabolic acidosis?)
Calcium gluconate/carbonate?
Aspiration
Discharge from mouth or nares prior to intubation, or after intubation in the presence of non-secured airways (uncuffed ETT)
Pre-existing aspiration pneumonia confirmed by radiography
Aetiology
Hx: vomiting + GIT disease
No fasting before anaesthesia
High risk patients
Brachycephalic dogs
aortic arch malformation
megaoesophagus
pregnancy
Treatment/prevention
Pretreatment with MCP, H2 blockers, proton pump inhibitors
Appropriate fasting when possible
Head down position
Intubation and extubation in sternal recumbency
Rapid sequence induction
Treat patient according to clinical signs (IPPV, oxygen)
Extubation with partially inflated ETT
Active suction and flushing of the oesophagus
Respiratory arrest
Detection
Flat capnography waveform
Breathing bag not inflating/deflating
Lack of thoracic excursions
Aetiology
Tension pneumothorax
Overdose of respiratory depressant drugs
Propofol
Fentanyl
Brainstem injury
Hypoperfusion
Hypoxia
Mechanical trauma
Equipment failure
Kinked/rotated/obstructed ETT or hose
Obstructed breathing system (Bain)
Closed APL valve
Disconnection
capnography
breathing system
Treatment
Thoracocentesis (pneumothorax)
IPPV
Reversal of drugs
Check equipment
ETT + hose patency
opening of APL valve
Rule out disconnections
Common cardiovascular complications
Hypotension
Detection
Low ABP values
MAP <60mmHg, SAP <100mmHg, DAP <40mmHg
Poor peripheral pulse (may be accompanied by tachycardia)
The minimum acceptable mean arterial pressure for anaesthetised small animals is 60mmHg.
Blood pressure monitoring can be obtained indirectly with the use of Doppler and oscillometric devices or directly from a cannulated artery
Aetiology
Hypovolaemia
Blood loss
Dehydration
Changes in blood composition
Changes in TS and albumins
Low PCV
low COP
Decreased heart contractility
Cardiac disease
Anaesthetic agents (e.g. inhalational, propofol)
Inhalants cause a dose-dependent decrease in cardiac contractility and systemic vascular resistance
Severe hypercapnia
Vasodilation
Toxic shock
Endotoxaemia
Histamine release (morphine, allergies)
Drugs (e.g. Acepromazone, propofol, inhalational)
Treatment
Fluids or blood products (if hypovolaemia or changes in blood composition)
Crystalloids, colloids, FFP, FWB, Packed RBC, FP, Albumins
Positive inotropes (hypocontractility)
Dobutamine
Ephedrine
Noradrenaline
Vasopressors (Vasodilation)
Dopamine
Phenylephrine
Noradrenaline
Anti-histamines (histamine release)
Dyphenydramine
Using the lowest effective dose of an injectable agent +/- reducing the vaporiser setting = most beneficial in minimising hypotension during the anaesthetic event
Tachyarrhythmias
Fast rhythm detected by ECG, pulse-oximeter, doppler signal, arterial waveform or pulse palpation
Sinus tachycardia
Pain, arousal, hypotension, drugs (e.g. ketamine, alfaxalone), cardiac disease, hyperthyroidism, phechromocytoma, hyperthermia, hypokalaemia, atropine
Treatment
Re assess analgesia and anaesthetic depth
Measure blood pressure
Ensure adequate perfusion and oxygen delivery to the heart
Treat underlying conditions
If 2ry to drug/toxin exposure or underlying causes addressed then can consider use of beta-adrenergic blockers (esmolol, propranolol). Side effects include bradycardia, negative isotropy and hypotension.
Atrial fibrillation
Underlying cardiac disease (DCM), hypoxaemia
Treatment
Consider electrical cardioversion
Lidocaine effective only in case of acute onset
Ventricular tachycardia
Cardiac disease
Myocardial hypoxia/acidosis
Coronary hypoperfusion
Sepsis
Endotoxaemia
Hypomagnesaemia
Hypokalaemia
Hypercapnia
treatment
Ensure adequate perfusion and oxygen delivery to the heart
Give lidocaine IV
Address acid-base imbalances
Consider defibrillation/electrical cardioversion
HRs >200bpm in cats and >160bpm in dogs
Bradyarrhythmias
Slow rhythm detected by ECG, pulse oximeter, doppler signal, arterial waveform or pulse palpation
Sinus bradycardia
2nd degree AV block
3rd degree AV block
Aetiology
Drugs/drug overdose
opioids
a2-agonists
Propofol
inhalational agents
Hypothermia
Hypertension
Vagal stimulation
Oculocardiac reflex
Intubation
Increased ICP
Sino atrial node sickness
hypothyroidism
Hyperkalaemia
Treatment
Reverse/antagonise (Nalazone, atipamezole)
Ensure normal body temperature
Re-assess anaesthetic depth
Address hypertension (pain? increased ICP?)
Anticholinergics (vagal stimulation)
Atropine, glycopyrronium
Normalise ICP (mannitol)
External pacing (SAN disease)
Correct electrolyte imbalances (calcium gluconate, insulin, glucose, Na bicarbonate)
Bradycardia is expected reflex following a2 administration and need not be treated unless hypotension +/- reduced peripheral perfusion become present
in this case a2 antagonist should be administered first and given time to take effect before administering an anticholinergic
Bradycardia
HR<50bpm in large dogs
HR<70bpm in small dogs
HR <100bpm in cats
Cardiac arrest
Asystole, usually preceded by bradycardia
Absence of peripheral pulsation
Loss of capnography waveform
Aetiology
Drugs/drug overdose (opioids, a2 agonists, propofol, inhalational agents)
Intense vagal stimulation
Hyperkalaemia
Myocardial acidosis/hypoxia
Coronary hypoperfusion
Hypercapnia
Cardio-pulmonary-cerebral resuscitation (CPCR)
Maintenance of airways
100% O2
IPPV: 12-15 breaths/min
Maintenance of circulation
Cardiac massage
about 100/min
right lateral recumbency, left leg towards cranial
Stop all anaesthetic drugs/reverse and antagonise
Pharmacological treatment
Atropine IV: 20microgram/kg
conservative IPPV (low TV because CO is also low)
Cardiac massage (80-100 compression per min)
Adrenaline IV: 20 microgram/kg
If no success within 2 minutes: atropine/adrenaline
In case of fibrillation: defibrillation
If capnograph
shark fin pattern
may suggest partial obstruction of tube
DEMOCRAT
: Drugs, Equipment, Mechanical, Other patient problems and procedure, Cardiac, Respiratory, Allergic, Toxic.