Intraoperative complications (Yr 3)

Question 1

what are the three main systems affected under anaesthetic?

Answer 1

CNS
cardiovascular
respiratory
(renal and hepatic)

Question 2

what are the most common three complications of anaesthetic?

Answer 2

hypotension
hypothermia
hypoventilation (hypercapnia, hypoxia)
(three Hs)

Question 3

what is the mean arterial blood pressure needed to be maintained for vital organ perfusion?

Answer 3

> 60mmHg

Question 4

what is hypotension defined as?

Answer 4

low blood pressure (MAP <60mmHg)

Question 5

what are the two general causes of hypotension?

Answer 5

reduced cardiac output
reduced systemic vascular resistance (vasodilation)

Question 6

why may cardiac output be reduced?

Answer 6

reduced stroke volume
reduced heart rate

Question 7

what can cause reduced stroke volume?

Answer 7

hypovolaemia/dehydration
reduced venous return (dorsal recumbency, IPPV)
disease (pericardial effusions)

Question 8

what steps are taken if your patient become hypotensive?

Answer 8

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)

Question 9

what fluids would you give in a case of hypotension during surgery?

Answer 9

crystalloids 10ml/kg over 10-15 minutes
(blood products if haemorrhaging)

Question 10

what are some positive inotropes?

Answer 10

dobutamine
dopamine

Question 11

what are some consequences of hypotension?

Answer 11

acute kidney injury
myopathy (large animals)
poor cardiac perfusion (arrhythmias/death)

Question 12

what causes hypothermia of anaesthetised patients?

Answer 12

increased heat loss
reduced heat production
abolished behavioural responses
alterations in hypothalamic function

Question 13

what is a HME?

Answer 13

heat and moisture exchanger (stops as much heat/moisture being lost when the animal breathes)

Question 14

what are some consequences of hypothermia?

Answer 14

cardiovascular/haematology - arrhythmias, coagulopathy, reduced immune function
metabolic - reduced drug metabolism, shivering (increased oxygen demand)

Question 15

what are the two consequences of hypoventilation?

Answer 15

hypercapnia
hypoxaemia

Question 16

how can CO2 in blood be measured?

Answer 16

arterial blood gas
capnograph

Question 17

what is the normal CO2 of blood?

Answer 17

35-45 mmHg

Question 18

when does hypercapnia need treating?

Answer 18

ETCO2 >60mmHg

Question 19

how can hypercapnia be treated?

Answer 19

increase minute ventilation by lightening plane of anaesthesia or mechanical ventilation

Question 20

when does hypoxaemia need treating?

Answer 20

SpO2 of <90%
PaO2 of <60mmHg

Question 21

what are the causes of hypoxaemia?

Answer 21

not enough oxygen delivered
profound hypoventilation
impaired gas exchange (disease/compression)
airway obstruction
severe hypovolaemia (shock)

Question 22

how can hypoxaemia be treated?

Answer 22

increase oxygen delivery
mechanical ventilation
bronchodilation
check ET tube for blockages
restore circulating volume (fluid/vasopressors)

Question 23

what can cause bradycardia under anaesthetics?

Answer 23

increased parasympathetic system activation (drug or vagal response)
hypothermia
disease (hyperkalaemia, raised intracranial pressure)

Question 24

what is a vagal response during surgery?

Answer 24

when the vagus nerve is stimulated causing parasympathetic tone to increase and the heart rate to decrease

Question 25

what are the consequences of bradycardia?

Answer 25

reduced cardiac output leading to reduced blood pressure and hence reduced perfusion leading to organ/tissue damage

Question 26

is bradycardia more of a concern in young or old animals?

Answer 26

neonates - heart not as good at responding by increasing contractility (they maintain cardiac output by using their heart rate)

Question 27

when does bradycardia need treating?

Answer 27

depends on blood pressure…
if MAP <60mmHg

Question 28

what causes tachycardia under anaesthetic?

Answer 28

increased sympathetic tone (pain)
hypovolaemia
hyperthermia
hypercapnia

Question 29

what can be done to treat tachycardia?

Answer 29

treat underlying cause…
pain - analgesia
hypovolaemia - fluid/vasopressor
hyperthermia - cool
hypercapnia - reduce anaesthetic plane, start ventilation