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Anaesthesia > Care of the Anaesthetised Patient > Flashcards

Care of the Anaesthetised Patient Flashcards

1
Q

Main aim for care of anaesthetised patient

A

Maintain tissue oxygen delivery

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2
Q

What contributes to oxygen delivery?

A

Cardiac output and oxygen content

CO = HRxSV
Oxygen content (haemaglobin and oxygen saturation)
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3
Q

Why may respiratory support during anaesthesia be necessary?

A 
May need support to avoid
\+ Hypoventilation
\+ Hypoxaemia
\+ Hypercapnia
therefore to maintain blood oxygen content
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4
Q

Why may hypercapnia occur? What is the normal CO2 range?

A

Hypoventilation

Rebreathing of exhaled gas
+ Not enough fresh gas
+ Scavenging expired

Increased basal metabolic rate

Normal range = 35-45mmHg

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5
Q

When can hypercapnia be a good thing in anaesthesia?

A

Increases sympathetic tone
Stimulates respiratory centre
Can be good if mild

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6
Q

What are the bad side effects of severe hypercapnia?

A 
Tachycardia
Hypertension
Cardiac arrhythmias
Increased intracranial pressure
CV depression at high levels
Respiratory acidosis
Vasoldilation (severe hypotension)
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7
Q

What is the difference between hypoxaemia and hypoxia?

A

Hypoxaemia = arterial partial pressure of oxygen (PaO2) is below normal

Hypoxia = reduction of oxygen supply at the tissue level

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8
Q

When does an animal have hypoxaemia? (value)

A

Arterial PaO2 <60mmHg

SpO2 <90%

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9
Q

Why may hypoxaemia occur?

A

Decreased fraction inspired oxygen (FiO2)

Hypoventilation

V/Q mismatch

Cardiovascular depression

Thickening of diffusion barrier eg. alveolar fibrosis

Anaemia

Increased O2 demand
+ Pyrexia
+ Increased base metabolic rate
+ Shivering

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10
Q

How can we help in cases of hypoxaemia and hypercapnia?

A 
Check anaesthetic depth
Check airway
Increase FiO2 (if possible)
Ensure no rebreathing of CO2
Ventilate (IPPV)
Consider use of PEEP
Consider use of salbutamol in horses
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11
Q

Is more pressure required to breathe spontaneously or mechanically (IPPV)?

A

Mechanically

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12
Q

Effects of IPPV (intermittent positive pressure ventilation)

A

Intrapleural pressure remains above 0

Decreased venous return and CO
+ Worse with high pressures and long inspiratory times
+ Worse in hypovolaemia animals/heart failure

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13
Q

Guidelines for using IPPV…

A

Deliver tidal volume 10-15ml/kg

Rate 10-20 breaths/min

Inspiratory:expiratory ratio should be 1:2-1:3
+ Expirations passive process so needs more time

End-tidal CO2 35-45mmHg

Peak inspiratory pressure <20cmH2O

Positive end-expiratory pressure (PEEP) <5cmH2O

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14
Q

What is CO reduced by during anaesthesia?

A 
Extremes of HR
Disturbances of rhythm
Poor stroke volime
Poor ventricular filling
Poor myocardial contractility
High vascular resistance
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15
Q

How should you approach CVS support in anaesthesia?

A

Attend any problems with HR/rhythm

Treat underlying hypovolaemia/hypotension

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16
Q

What causes bradycardia in the anaesthetised patient?

A

High vagal tone

Electrolyte and acid-base disturbance (high K+)

Hypothermia

Drugs

Potent μ agonist opioids
alpha2 agonists

Response to hypertension (baroreflex)

Bradyarrhythmias

17
Q

When does an animal have bradycardia?

a. Dog
b. Cat
c. Horse

A

a. <50bpm
b. <90bpm
c. <26bpm

18
Q

Treatments for bradycardia and bradyarrhythmias in the anaesthesia patient…

A

Check monitored parameters and anaesthetic depth

Remember alpha2 agonists cause bradycardia

Beware raised intracranial pressure as a cause (atropine can be disaster)

Atropine IV
Glycopyrrolate IV (anticholinergic)
19
Q

What causes tachycardia in the anaesthetised patient?

A 
High circulating catecholamines
Pain
Hypotension/hypovolaemia
Hypoxia
Hypercapnia
Hyperthermia
Anaemia
Drugs (sympathomimetics, parasympatholytics)
Tachyarrhythmias
20
Q

When does an animal have tachycardia?

a. Dog
b. Cat
c. Horse

A

Dog: >180bpm
Cat: >220bpm
Horse: >50bpm

21
Q

Treatment for tachycardia in anaesthesia…

A

Check monitored parameters and anaesthetic depth

Rule out or treat underlying cause

22
Q

How can you treat AV block?

A

Atropine or glycopyrrolate

23
Q

Is atrial fibrillation usually a problem during anaesthetic?

A

Unusual to develop during anaesthetic

24
Q

Describe the occurrence of ventricular arrhythmias during anaesthetic..

A

Can occur singly or in runs or as ventricular tachycardia

Try to determine cause

25
Q

When would you treat ventricular arrhythmia? What with?

A

If haemodynamically significant
+ Assess pulse quality and rate
+ Assess blood pressure
+ SpO2 mm colour and CRT

Lidocaine (slow IV bolus followed by continuous rate infusion) 2mg/kg.

26
Q

How can you treat underlying hypovolaemia/hypotension during anaesthesia?

A

Reduce depth of anaesthesia if possible

Give IV fluids

Inotropes/vasopressors

27
Q

What fluids is it common practice to give during anaesthesia?

A

Crystalloids (relative hypovolaemia)

Most common = compound sodium lactate because it is balanced (electrolytes in similar concentration to plasma)

May need rapid bolus if emergency

28
Q

Blood volume of:

a. Dog
b. Cat

A

Dog: 80-90ml/kg
Cat: 50-60ml/kg

29
Q

What type of fluid should be given:

  1. Up to 10% total blood volume loss
  2. 10-25% total blood volume loss
  3. > 25% total blood volume loss
  4. PCV <20% or [Hb] <7g/dl
A
  1. Crystalloid
  2. Colloid
  3. Blood
  4. Blood or packed red blood cells
30
Q

What inotropes can be given during anaesthesia?

A

Dopamine

Dobutamine

31
Q

Effects of dopamine during anaesthesia?

a. Low rate
b. Mid range
c. High rate

A

a. DA receptor
b. Beta 1 receptors positive inotrope
c. Alpha 1 receptors, vasoconstriction

Arrhythmogenic

32
Q

Effects of dobutamine during anaesthesia?

A

Acts mainly on beta1 receptors

+ve inotrope effect with minimal effect on vascular resistance

Mild chronotrope

Less arrhythmogenic

33
Q

Which vasopressor drugs can be given during anaesthesia?

A

Noradrenaline
Ephedrine
Phenylephrine
Vasopressin

34
Q

What is meant by a vasopressor drug?

A

A drug that contracts blood vessels to raise blood pressure.

35
Q

What is the increased intracranial pressure Cushing reflex?

A

Impending death

Last ditch attempt to maintain perfusion

Triad:
+ Increased blood pressure
+ Bradycardia
+ Respiratory changes

36
Q

How can we treat increased ICP?

A

Hyperventilate as emergency measure

Mannitol (osmotic effects reduce blood viscosity = improves flow and O2 deliver)

Hypertonic saline

Furosemide?

Anaesthesia (9 decks)

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