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48 Cards in this Set
- Front
- Back
Emergency |
Events that lead rapidly and inevitably to death if untreated or mismanaged No or little time for preparation |
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Problems |
Minor, often predictable disturbances that may spontaneously resolve Individually - little concern Collectively - may create an emergency |
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How can apnoea occur? |
De novo - acute event End result of progressive untended hypoventilation Sign of cardiac arrest |
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In cardiac arrest when does breathing stop? |
Breathing continues until medullary ischaemia causes arrest |
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What can cause acute or end-result apnoea? |
Neural unresponsiveness Mechanical obstruction, restriction, ineffective ventilation |
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What may cause neural unresponsiveness? |
Intracranial hypertension, concussion, severe hypothermia, hypocapnia, anaesthetic overdose, normal dose of super-opioids |
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What are the clinical signs seen with an obstruction? |
Bizarre, "diaphragmatic or paradoxical" breathing pattern Overinflated respiratory bag if valve closed and FGF high Gurgling May be impossible to sigh animal |
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How do you find out if the obstruction is between the bag and the chest wall? |
Squeeze bag and see if chest wall moves |
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How should you treat respiratory arrest based on neural unresponsiveness? |
Ventilation should be supported manually End anaesthesia if cranial nerve reflexes absent -> indicates overdose Ventilate animal until drug is redistributed Don't give other drugs, wait until these drugs are out of system |
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What happens if the animal is hyperventilated? |
May cause hypocapnia, and animal may not breathe |
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Treating a mechanical obstruction? |
Clear obstruction or bypass with tracheostomy Vomit aspiration - position head down, mouth gagged if conscious, clear oropharynx of material with towel forceps or haemostats Lost consciousness - brief cleaning followed by ET intubation and PPV with O2, suction then lavage |
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4 causes of cardiac arrest |
Myocardial hypoxia (systemic hypoxia, local - hypotension, bradycardia, tachcardia, arrythmias) Toxaemia Electrolyte and pH disturbances Hypothermia |
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How do you treat systemic hypoxia caused by atmospheric hypoxia |
Increase FIO2 |
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Tidal hypoxia |
Intubate, IPPV O2 |
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Alveolar hypoxia |
Optimise VA and Qt |
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Haemoglobinaemic hypoxia |
Whole blood or RBCs |
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Stagnant hypoxia |
Correct cause, fluid, inotropes |
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How does tachycardia cause cardiac arrest? |
May be due to inadequate anaesthesia Shorter diastole so no coronary blood supply (occurs during diastole) |
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How do you detect hypotension? |
Imperceptible peripheral pulses Diminished blood flow at surgical site |
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prolonged hypotension will lead to post-operative failure in which organs? |
Kidney and GI tract Myositis in horses |
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Arterial BP = |
CO x SVR |
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CO = |
SV X HR |
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What 3 things affect SV? |
Preload Afterload Contractility |
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How should you treat severe hypotension? |
Fluids rapidly Inotropes/alpha-1 agonists like phenylephrine if contractility decreased or decreased SVR |
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How does bradycardia cause cardiac arrest? |
Insufficient CO to maintain adequate diastolic pressure required for coronary perfusion |
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treatment if cause is vagus? |
Check surgeon, suspend surgery, otherwise atropine |
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How does tachycardia cause myocardial hypoxia? |
Excessive work -> O2 requirement > delivery |
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What is VPC? |
Venricular premature complex - premature contraction |
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What will this be followed by? |
Ventricular fibrillation |
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What may cause arrhythmias? |
Myocardial hypoxia SNS activation (hypoxia, hypercapnia, light anaesthesia, hypotension, hypoglycaemia) Drugs - alpha 2 agonist, adrenaline Electrolyte abnormalities (K) Surgical procedures Pre-existing heart disease Conditions e.g. GDV |
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How are arrythmias diagnosed? |
ECG |
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What is EMD? |
Electro-mechanical dissociation - no mechanical activity of heart but normal ECG, no palpable pulses |
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How do you treat arrhythmias? |
May just need adequate anaesthesia and ventilation, sigh animal O2 |
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How does toxaemia affect the heart? |
Reduces myocardial contractility and excitability |
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Give examples of toxaemia occurrences |
Azotaemia - renal disease Ketoacidosis - diabetes Lactacidaemia - hypovolaemic shock Endotoxaemia - pyometra |
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How should toxaemia be treated? |
Correct underlying condition Restore perfusion (restore ECV) |
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Why should excessive levels of anaesthetic be avoided? |
Lead to prolonged recoveries Post-operative organ failure - caused by cardiopulmonary depression Predispose to or cause cardiac arrest |
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Which electrolyte imbalance is most likely to cause cardiac arrest? |
Hyperkalaemia Addison's, iatrogenic, renal failure, injury/burns, acidaemia |
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treatment |
Hyperventilation, fluids, bicarbonate, calcium gluconate, insulin, glucose, peritoneal dialysis |
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No pot no tea |
Hypokalaemia no T waves Hyperkalaemia no P waves |
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Why is hypothermia common under anaesthetic? |
Hypothalamic thermoregulation impaired Vasodilation of skin bvs Skeletal muscle activity ceases Shivering inhibited Visceral surfaces exposed Inspired gases cold and dry in non-rebreathing systems |
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Which animals are most at risk? |
Undeveloped/impaired thermoregulation- old and young High surface area to volume ratios - neonates, birds, small lab animals |
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Effects of hypothermia |
Reduced alveolar ventilation Reduced heart rate and CO Left-shifted oxyhaemoglobin curve Increased blood viscosity |
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Consequences |
Prolonged recovery cardiac arrest -Ventricular fibrillation |
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How to prevent hypothermia |
Increase operating room temp. Do not lay animals on cold, un-insulated surfaces No draught exposure BAIR hugger, aluminium foil, bubble wrap, blankets, heat lamps, heat incoming fluids |
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Why might the animal get skin burns? |
Hypothermia -> vasoconstriction, so no heat removed by venous supply |
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How to prevent with anaesthetic factors |
Short-acting anaesthetics Do not over-ventilate Not too deep anaesthesia Rebreathing system where appropriate |
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How to prevent with surgical factors |
Avoid unnecessary wetting and clipping of non-surgical areas Minimise surgical time Exposed viscera moistened with warm irrigation fluids Small incision size |