Anaesthesia - general Flashcards by Ella Townsend

What normally happens to urine output under anaesthesia?

decreased as ADH release from stress

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When is an animal hypoxaemic?

PaO2< 60 mmHg

SpO2<90%

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What can cause hypoxaemia / hypoxia?

low FiO2( fraction inspired O2)
hypventilation
V/Q mismatch
CVS depression
anaemia
increased O2 demand

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What can cause hypercapnia?

hypoventilation
rebreathing
high BMR
tachycardia
hypertension
arrhythmias
high intracranial pressure
CVS depression
resp acidosis

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How can you correct hypoxia / hypercapnia?

-check depth
-check if rebreathing
-increase FiO2
IPPV
ventolin in horse

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what is IPPV?

intermittent positive pressure ventilation

-get reduced venous return and CO as intrapleural pressure will be +ve

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What do you aim for with IPPV?

Tidal vol : 10-15 ml/kg
RR : 10-20
Inspire : expire : 1:2 - 1:3
ET CO2 : 35-45 mmHg
Peak inspiratory pressure : <5cm H2O

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What is classed as bradycardia?
What could be causing it?
What do you do?

<26bpm (horse)

due to: high vagal tone, acid-base distrubance, hypothermia, a 2 agonists , hypertension, high ICP, too deep
check : depthc, give atropine / glycopyrrolate

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What is classed as tacchycardia?
What could be causing it?
What do you do?

> 180 bpm (SA), > 50 bpm (horse)

due to: high catecholamines (pain, hypotension, hypovol, hypoxia, hypercapnia), hyperthermia, anaemia, drugs, tacchyarrhythmias
check depth and treat cause

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What do you do with an AV block?

if not due to a2 agonist then give atropine / glycopyrrolate

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what do you do with a VPC?

lidocaine

treat if haemodynamically significant

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What is cat, dog and horse blood volume?

dog and horse : 80-90 ml/kg

cat: 60-70 ml/kg

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How do you correct hypvolaemia / hypotension?

fluids

Inotropes - dopamine, dobutamine

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What fluid do you give for 10% blood loss?

crystalloid

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what type of fluid do you give for 10-25% blood loss?

colloid

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What type of fluid do you give for over 25% blood loss?

blood product

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What are the consequences of hypothermia?

decreased anaesthetic need
prolonged recovery
increased blood loss
shivering increases oxygen need
increased infection risk

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how can you treat hypothermia?

warm fluid
warm lavage
bubble wrap

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What effects does an increased intracranial pressure have?

high bp

bradycardia

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How can you control high ICP?

hyperventilate

osmosis (mannitol, hypertonic saline, furosemide) to decrease blood viscosity and improve blood flow

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What does pulse oximetry measure?

HbO2 sat, PaO2, Hr

used LED sensor to see how much oxygenated haemoglobin

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Where is pulse ox measured?

tongue
mammary gland
toe
prepuce 
ear

What are important things to consider with pulse ox?

if anaemic can still have high saturation but be hypoxic as not enough Hb
on 100% O2 cant hypoventilated enough to drop Pa02 so monitor during recovery and when not on O2
CO will still read as high saturation

what does capnography measure?

expired CO2

what is a normal end tidal CO2?

35-45 mmHg

what can cause hypercapnia?

hypoventilation high CO hyperthermia bicarb given

What can cause hypocapnia?

hyperventilation low CO hypothermia

what do you see on a capnograph if rebreathing?

non return to baseline

What reflexes can be tested for depth?

``` palpebral ocular position pupil diameter jaw tone lacrimation salivation nystagmus ```

what drug can interfere with reflex assessment of depth?

ketamine

Normal cat dog and horse bp?

dog = 100 cat =135 horse = 90

ok bp for anaesthetissed SA?

over 70

3 ways to measure bp?

doppler flow - sensor below cuff on limb / tail oscillometric - automatic direct - catheter in peripheral artery

How is central venous pressure measured?

catheter from jugular to vena cava | how ' full' the circulation is

When do you intubate?

eyes rotated ventrally minimal parapebral reflex loose jaw tone no swallowing reflex

what drug is used for intubation?

llidocaine spray | *careful as easy to overdose cat

what are the two type of ET cuff?

high pressure, low volume | low pressure, high volume

what are some problems with ET tubes?

- if too long then intubate one lung only - mucus in tube can occlude it - occlusion by tracheal wall prevented by murphy's eye - overinflated cuff - compress tube lumen or compress trachea and get necrosis

When do you extubate?

when swallowing reflex is back

what do you extubate earlier?

cats

who do you extubate later?

brachycephalic vomiting risk ruminants

How does anaemia affect anaesthesia?

- less Hb so although the Hb present may be fully saturated the oxygen content of the blood will be reduced - CO will increase to maintain oxygen delivery to tissues - be careful as most anaesthetic drugs decrease CO so can drop oxygen delivery to a critical level - consider transfusion if acute and have ongoing blood loss

How does mitral valve disease affect anaesthesia?

- increased SV but ejection fraction is reduced so get forward failure and reduced CO - compensatory increased ventricular filling and activation of RAAS - get pulmonary congestion - need to stabilise before anaesthesia - want to avoid bradycardia as can cause valve regurgitation

How does pulmonary oedema affect anaesthesia?

- very high risk if animal cyanotic and dyspnoiec - lungs wont expand as much and alveoli filled with fluid so will increase oxygen consumption as breathing is harder - will be V/Q mismatch and shunting so reduced blood oxygen content - treat before anaesthesia

When is an animal cyanotic?

Hb under 75-85% sat

how does hypoproteinaemia affect anaesthesia?

- affect amount of drugs free / bound - will have more unbound drug so a greater response seen to a given dose - risk of oedema as oncotic pressure is lower

How does azotaemia affect anaesthesia?

- increased free drug concentrations due to acidosis - oxygen dissocation curve shifted to the right (reducing o2 affinity) - changes in serum potassium affecting myocardial contractility - pre-op fluids to increase GFR and induce diuresis

How does HCM affect anaesthesia?

-have extra heart muscle which due to vasodilation from anaesthesia wont be perfused so more likely to get arrhythmias and arrest

how is sepsis a complication with anaesthesia?

already hugely vasodilated

What is anaesthesia?

loss of sensation resulting form pharmacological depression of nerve function

What is a GA?

a state of unconsciousness produced by controlled reversible drug-induced intoxication of the CNS in which the patient neither receives or recalls noxious stimuli

What do we want from a Ga?

``` unconsciousness analgesia muscle relaxation amnesia homeostasis normal oxygen delivery ```

how long do you fast each species for pre-op?

cat and dog - 6 h horse -12 h cow - 24 h rabbit - no

what can N2O exposure do?

inhibit DNA synthesis and cause CNS damage