general care
positioning
nursing care
eye care
respiratory support - aims
avoid hypoventilation, hypoxaemia, hypercapnia + maintain blood oxygen content
Hypoxaemia and Hypoxia - causes
↓FiO2 Hypoventilation V/Q mismatch Cardiovascular depression Anaemia Increased O2 demand - pyrexia, ↑BMR
hypercapnia - define
incr CO2
hypercapnia - causes
Hypoventilation
rebreathing of exhaled gas
↑BMR
hypercapnia - effects
Tachycardia Hypertension Cardiac arrhythmias Increased intracranial pressure Cardiovascular depression at very high levels Respiratory acidosis
hypoxaemia and hypoxia - treatment
Check anaesthetic depth
Check airway
Increase FiO2 (if possible)
Ensure no rebreathing of CO2
Ventilate (Intermittent Positive Pressure Ventilation – IPPV)
Consider using albuterol (Ventolin) in horses - bronchodilator - incr ventilation
IPPV - define
intermittent positive pressure ventilation
IPPV - effects
Intrapleural pressures remain above zero throughout
respiratory cycle
Decr venous return decr cardiac output
Worse with high pressures and long inspiratory times
worse in hypovolaemic animals or those in heart failure
causes of hypoperfusion
Extremes of heart rate, disturbances of rhythm
Poor stroke volume - Poor ventricular filling (low preload), Poor myocardial contractility, High vascular resistance (afterload)
bradycardia - causes
High vagal tone
Electrolyte and acid-base disturbances (esp high K+)
Hypothermia
Drugs (potent mu-agonist opioids, α2 agonists)
Response to hypertension
Bradyarrhythmias
bradycardia - treatment
Check monitored parameters and anaesthetic depth
Remember α2 agonists = bradycardia
Beware raised intracranial pressure as a cause
atropine
Glycopyrrolate
tachycardia - causes
High circulating catecholamines – pain, hypotension, hypovolaemia, hypoxia, hypercapnia
Hyperthermia
Anaemia
Drugs (sympathomimetics, parasympatholytics)
Tachyarrhythmias
dehydration - due to stress
tachycardia - treatment
Check monitored parameters and anaesthetic depth
Rule out or treat underlying cause
AV block - treatment
Atropine or glycopyrrolate
Ventricular arrhythmias - treatment
Lidocaine
fluids
crystalloid fluids common - CSL most common as it’s balanced
May need rapid bolus in emergency situation
Plasma
Fresh whole blood (FWB)
Packed red blood cells (PRBC)
Human serum albumin (HSA)
blood volume loss - which fluid to give
Up to 10% total blood volume loss – Crystalloid
10-25% total blood volume loss – Colloid
> 25% total blood volume loss – Blood
PCV < 20% or [Hb] < 10g/dl – Blood or PRBCs
dopamine
positive inotrope
DA receptors at low concs, but at higher
concs also acts on α1 and β1 receptors
Not used in horses – causes more tachycardia
dobutamine
positive inotrope
Acts mainly on β1 receptors
Effects in peripheral vasculature tend to cancel out, so overall has +ve inotropic effect with minimal
effect on vascular resistance
Only mild chronotropic effects + less arrhythmogenic than dopamine
effects of hypothermia
Reduced requirement for anaesthetics (5% reduction in MAC for every degree C reduction)
Alters pharmacokinetics + pharmacodynamics of drugs - prolonged recovery
Incr blood loss (incr clotting times)
Shivering incr oxygen demand in recovery
Incr incidence of surgical wound infection
temperature support
Rebreathing circuits
Heat and moisture exchangers (HMEs)
Warm IV fluids
Bubble wrap, foil blankets, leg wraps, heated water blankets, warm air blowers
Warm operating theatre
Warm lavage of body cavities, stomach, bladder, colon
increased intercranial pressure (ICP)
Impending death ‘Last ditch’ attempt to maintain perfusion ↑ Blood pressure Bradycardia (Respiratory changes if not ventilated)
increased intercranial pressure (ICP) - treament
Hyperventilate as emergency measure (if anaesthetized)
Mannitol – osmotic effects also reduce blood viscosity which improves blood flow + oxygen delivery
Hypertonic saline
Furosemide – may be synergistic with mannitol
