Intraoperative complications (Yr 3) Flashcards
what are the three main systems affected under anaesthetic?
CNS
cardiovascular
respiratory
(renal and hepatic)
what are the most common three complications of anaesthetic?
hypotension
hypothermia
hypoventilation (hypercapnia, hypoxia)
(three Hs)
what is the mean arterial blood pressure needed to be maintained for vital organ perfusion?
> 60mmHg
what is hypotension defined as?
low blood pressure (MAP <60mmHg)
what are the two general causes of hypotension?
reduced cardiac output
reduced systemic vascular resistance (vasodilation)
why may cardiac output be reduced?
reduced stroke volume
reduced heart rate
what can cause reduced stroke volume?
hypovolaemia/dehydration
reduced venous return (dorsal recumbency, IPPV)
disease (pericardial effusions)
what steps are taken if your patient become hypotensive?
check cuff/reading
check plane of anaesthesia (and reduce)
check heart rate (and treat if low)
give fluid therapy (crystalloids)
give drugs (vasopressor, positive inotrope)
what fluids would you give in a case of hypotension during surgery?
crystalloids 10ml/kg over 10-15 minutes
(blood products if haemorrhaging)
what are some positive inotropes?
dobutamine
dopamine
what are some consequences of hypotension?
acute kidney injury
myopathy (large animals)
poor cardiac perfusion (arrhythmias/death)
what causes hypothermia of anaesthetised patients?
increased heat loss
reduced heat production
abolished behavioural responses
alterations in hypothalamic function
what is a HME?
heat and moisture exchanger (stops as much heat/moisture being lost when the animal breathes)
what are some consequences of hypothermia?
cardiovascular/haematology - arrhythmias, coagulopathy, reduced immune function
metabolic - reduced drug metabolism, shivering (increased oxygen demand)
what are the two consequences of hypoventilation?
hypercapnia
hypoxaemia
how can CO2 in blood be measured?
arterial blood gas
capnograph
what is the normal CO2 of blood?
35-45 mmHg
when does hypercapnia need treating?
ETCO2 >60mmHg
how can hypercapnia be treated?
increase minute ventilation by lightening plane of anaesthesia or mechanical ventilation
when does hypoxaemia need treating?
SpO2 of <90%
PaO2 of <60mmHg
what are the causes of hypoxaemia?
not enough oxygen delivered
profound hypoventilation
impaired gas exchange (disease/compression)
airway obstruction
severe hypovolaemia (shock)
how can hypoxaemia be treated?
increase oxygen delivery
mechanical ventilation
bronchodilation
check ET tube for blockages
restore circulating volume (fluid/vasopressors)
what can cause bradycardia under anaesthetics?
increased parasympathetic system activation (drug or vagal response)
hypothermia
disease (hyperkalaemia, raised intracranial pressure)
what is a vagal response during surgery?
when the vagus nerve is stimulated causing parasympathetic tone to increase and the heart rate to decrease
