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Applied Clinical Veterinary Nursing > Anaesthesia for Pre-existing Conditions > Flashcards

Anaesthesia for Pre-existing Conditions Flashcards

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1
Q

what is contained in the intracranial cavity?

A

brain (80%)
CSF (10%)
blood (10%)

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2
Q

what might disrupt the blood-brain barrier?

A

trauma
inflammation
hypertension

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3
Q

how much of the total cardiac output does the brain receive?

A

15%

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4
Q

why do increases in CSF or intracranial blood volume have such an effect on ICP?

A

the skull is a fixed space and unable to expand

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5
Q

what can an increase in CSF or intracranial blood pressure result in?

A

increase in ICP

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6
Q

why is the brain reliant on maintenance of intracranial blood volume?

A

to support the brains high metabolic rate

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7
Q

what supports the brains high metabolic rate?

A

the maintenance of intracranial blood volume

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8
Q

what are the main aims when anaesthetising animals with neurological/brain trauma?

A

maintenance of cerebral blood flow

reduce increases in ICP

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9
Q

what is the normal ICP?

A

5-12 mmHg

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10
Q

what are the signs of high ICP?

A

papilledema, abnormal pulsing of retinal vessels, depression, stupor, coma

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11
Q

can compensatory mechanisms for ICP continue indefinitely?

A

they can become exhausted if ICP continues to build (e.g. haemorrhage)

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12
Q

what is the cushings reflex?

A

a response to raised ICP

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13
Q

what is involved in the cushings reflex?

A

reflex bradycardia and hypertension

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14
Q

what can also be seen in addition to bradycardia and hypertension in the cushings reflex?

A

irregular breathing/apnoea

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15
Q

why does the cushings reflex occur?

A

because of the reduction in cerebral blood flow

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16
Q

what is the aim of the cushings reflex?

A

decrease intracranial volume/pressure

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17
Q

what physiological marker triggers the cushings reflex?

A

a reduction in blood flow causes an accumulation of CO2 as a result of poor perfusion - increased in CO2 is detected by the brainstem

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18
Q

which branch of the nervous system involves the cushings reflex?

A

sympathetic

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19
Q

how does the sympathetic nervous system respond in the cushings reflex?

A

increases MAP, which in turn alerts baroreceptors and causes a reflex bradycardia

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20
Q

how can we avoid/control ICP?

A

avoid coughing (consider antitussives)
avoid neck leads
careful intubation
avoid pressure on neck during restraint
avoid jugular sampling
avoid straining to pass faeces/urine

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21
Q

what are the broad considerations for anaesthetising a neurological case?

A

thorough pre-operative assessment

use of mGCS

stabilisation pre-anaesthetic

consider drug choices carefully - should not increase ICP or cause dramatic change to MAP

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22
Q

what are the advantages of using opioids for neurological cases?

A

don’t tend to alter cerebral blood flow or increase ICP much
have minimal CVS and respiratory effects

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23
Q

which opioid should be avoided in neurological cases and why?

A

morphine/hydropmorphone - may increase incidence of vomiting

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24
Q

what are the advantages of using benzodiazepines in neurological cases?

A

no adverse effects on ICP, respiratory or CVS system

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25
Q

what effect do benzodiazepines have on anxiety in neurological cases?

A

can reduce anxiety (but somewhat unpredictable)

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26
Q

is ACP a good drug of choice in neurological cases?

A

no

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27
Q

why isn’t ACP an appropriate choice for neurological cases?

A

may seizure trigger activity

causes systemic vasodilation –> hypotension and cerebral vasodilation

vasodilation will increase ICP

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28
Q

what effect does vasodilation have on ICP?

A

increases

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29
Q

can a2 agonists be used in neurological cases?

A

don’t appear to affect ICP but can cause significant cardiopulmonary dysfunction - use with caution

can cause vomiting in cats

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30
Q

why is it difficult to observe the cushings reflex when an a2 agonists has been given?

A

alpha 2s also cause an increase in MAP and bradycardia

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31
Q

which drugs make it difficult to observe the cushings reflex?

A

a2 agonists

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32
Q

can ketamine be used in neurological cases?

A

it is historically reported to increase ICP and so avoided for these purposes

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33
Q

what are the possible advantages of using ketamine in neurological cases?

A

may have neuroprotective properties and have fewer CVS and respiratory depressive effects than some other drugs

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34
Q

what has ketamine been reported to do when given with propofol?

A

reduce ICP

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35
Q

what considerations should be made for neurological cases on induction of anaesthesia

A

pre-oxygenation likely beneficial if doesn’t cause extra stress

ensure adequate depth prior to intubation to reduce risk of coughing

mild head elevation to assist with venous drainage may be helpful

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36
Q

which inhalational anaesthetic is better for neurological cases?

A

sevoflurane - iso may slightly increase ICP

37
Q

what is the highest acceptable ETCO2 in neurological cases?

A

45mmHg

38
Q

what are the main issues involved in monitoring MRI cases?

A

careful positioning
no metal (patient/staff/equipment)
difficult to maintain temperature
remote monitoring can be less detailed
often separate from main building - less staff if something goes wrong

39
Q

what are the common CSF tap sites?

A

cisterna magna
lumbar

40
Q

why is it important to monitor the patient closely during a cisterna magna CSF tap

A

head must be bent towards chest and ET tube can become kinked

41
Q

what are the airway considerations for neurological cases?

A

lateral intubation may be needed if neck instabilities

avoid coughing - ensure deep plane of anaesthesia before attempt intubation

consider ET tube positioning when performing CSF tap

42
Q

what specific considerations are there for patients who have a history of seizures?

A

often unknown cause - treat as if potential for raised ICP

establish any current medications/anticonvulsants

IV catheter essential

close monitoring before and after GA - post-op period most risky

43
Q

what considerations are there for cases with neuromuscular disorders?

A

may be pre-disposed to regurgitation/aspiration

weakness may affect respiratory muscles

aim for rapid induction and recovery

careful drug choices with myasthenia gravis

IPPV likely required - ensure capnography available

44
Q

what risks should be considered when anaesthetising a patient for planned GI surgery?

A

stabilise patient beforehand
may be dehydrated/anorexic
may have acid/base disturbances
potential for GOR/AP
likely painful

45
Q

what drugs should be avoided in GI cases?

A

drugs that may induce vomiting e.g. morphine

46
Q

how can we reduce risk of GOR/AP in GI patients?

A

always have suction available

head elevated until ET tube inserted and cuff inflated

47
Q

why should nitrous be avoided in GI cases?

A

will find its way into gas-filled spaces

48
Q

why is blood pressure not a good indicator of perfusion in GDV cases?

A

BP = CO x SVR

cardiac output reduced by dehydration and hypovolaemia

SVR increased due to compression of CVC, restricting blood flow to heart

combined these make BP appear ‘normal’

49
Q

why is close post-op monitoring required in GDV cases?

A

arrythmias common (40%) - may last 24hrs into post-op period

will likely be very painful - good analgesia required

50
Q

what is important to consider when anaesthetising patients with a pre-existing GI condition?

A

risk of GOR - shorter starvation times

if chronic disease, important to research and understand it well

consider medications and diet

may have electrolyte/acid base disturbances - pre-op bloods sensible

51
Q

name some things which can be associated with hepatic dysfunction which may affect anaesthesia

A

ascites/oedema/pulmonary oedema (hypoproteinaemia/hypoalbuminaemia)

pu/pd

anaemia

hypocalcaemia

hypoglycaemia

reduced clotting times

hypothermia risk

acid base disturbances

jaundice

encephalopathy

52
Q

what is hepatic encephalopathy?

A

a collection of neurological abnormalities which can occur due to hepatic disease

53
Q

what are the signs of hepatic encephalopathy?

A

signs associated with increased levels of toxins (inc ammonia) in the blood - the liver cannot process it properly and they build up in the bloodstream, access the CNS and result in encephalopathic signs

54
Q

what is the aim of medical management of hepatic encephalopathy?

A

reduce ammonia levels in the blood (via absorption or reduction)

55
Q

what can be used for treatment/stabilisation of hepatic encephalopathy?

A

lactulose

56
Q

how does lactulose help treat hepatic encephalopathy?

A

it is transformed by colonic bacteria into organic acids - this results in trapping of the ammonia ions and a decrease in the absorption of ammonia

57
Q

what are the main effects of liver dysfunction on anaesthesia?

A

prone to hypothermia and hypoglycaemia

low albumin - reduced protein binding of drugs means may have more of an effect

potentially slower biotransformation of drugs

risk of surgical haemorrhage due to coagulopathies

electrolyte imbalances - sodium retention and lower K+

58
Q

what are the pre-anaesthetic considerations for hepatic cases?

A

stabilise patient i.e. treat encephalopathy/seizures

59
Q

what should be considered when choosing a premedicant for hepatic cases?

A

minimal premedication - cautious with dosing
consider short-acting drugs
consider drugs which can be antagonised

60
Q

how should induction of anaesthesia be performed in hepatic cases?

A

slow and titrate - use lowest possible dose

61
Q

what class of drugs should be avoided in management of hepatic cases under anaesthesia?

A

avoid NSAIDs - coagulation issues, hepatic/renal effects

62
Q

what parameters are important to monitor under anaesthesia for hepatic cases?

A

body temperature
blood glucose

63
Q

what special considerations are there for nursing patients with coagulopathies?

A

care with venepuncture - use peripheral veins

ample pressure after samples/IV catheters

avoid rough handling/pulling on leads

avoid trauma - consider in excitable/dysphoric recoveries

64
Q

what pre-anaesthetic lab tests should ideally be done in patients with hepatic disease?

A

liver enzymes
bile acids
clotting factors
urea
plasma proteins
glucose

65
Q

what is an insulinoma?

A

pancreatic islet cell tumour

66
Q

what are the considerations for anaesthesia for insulinoma?

A

painful during and after surgery - adequate analgesia

monitor blood glucose closely post-operatively

possibility for pancreatitis post-op

consider using NMBA

67
Q

what should occur before anaesthesia for elective procedures surrounding diabetes mellitus?

A

stabilisation

68
Q

which aspects of diabetes mellitus which may affect anaesthesia?

A

hyperglycaemia
dehydration
weight loss
fatty liver
ketosis

69
Q

what are the nursing considerations for anaesthesia for diabetes mellitus?

A

find out routine from owner inc favourite foods

1st patient of day so they can get back to normal routine ASAP

monitor glucose throughout entire stay

consider half-dose insulin at start of day, feed as soon as possible after anaesthesia with remaining insulin dose

70
Q

what specific anaesthesia considerations are there for patients with diabetes mellitus?

A

use short-acting drugs

avoid medetomidine (can cause hyperglycaemia)

monitor blood glucose - consider second IV catheter for blood glucose sampling

fluids inc glucose

71
Q

what factors are there to consider when anaesthetising patients with hyperthyroidism?

A

multi-organ dysfunction

consider temperament - usually highly strung, try to avoid stress

thin, low BCS

PU/PD

muscle weakness

hypertrophic cardiomyopathy

72
Q

what are good drugs of choice for premed for patients with hyperthyroidism?

A

opioid +/- ACP

73
Q

which drugs should be avoided in patients with hyperthyroidism and why?

A

ketamine - increases myocardial workload and increases HR

medetomidine - drops cardiac output

74
Q

how should patients with hyperthyroidism ideally be induced?

A

IV if possible - avoids stress of IM and patient being left unwatched after IM drugs (risky)

75
Q

what are the specific considerations for thyroidectomy?

A

monitor blood pressure closely

location of surgery - lose access to head end of patient, limited depth checking

potential for laryngeal paralysis post-op

monitor for hypocalcaemia post-op

keep IV catheter in and patent

76
Q

what factors are there to consider when anaesthetising a canine patient with hypothyroidism?

A

often geriatric patients - consider additional risks

may have megaoesophagus - care with induction and intubation

decreased GI motility

lethargy and obesity common

bradycardia and hypotension

likely slow biotransformation of drugs

77
Q

what is hyperadrenocorticism usually caused by?

A

pituitary or adrenal tumour - leads to glucocorticoid excess

78
Q

patients with cushings disease often have poor muscle tone - why is this a problem?

A

respiratory muscle weakness can affect ventilation

79
Q

what considerations are there for patients with cushings disease?

A

poor muscle tone (ventilation)

may be overweight + lethargic

poor thermoregulation - monitor temp

risk of pukmonary thromboembolism - hypercoagulability

PUPD (Na+ retention, K+ excretion)

risk of wound infection, bruising

80
Q

what factors are important to consider when anaesthetising a patient with hypoadrenocorticism (addisons)?

A

unable to mount normal stress response - avoid stress!

hyperkalaemia

bradycardia

dehydration

weight loss, weakness/lethargy

important to stabilise before anaesthesia

81
Q

what factors need to be considered when anaesthetising patients with kidney disease?

A

effects of hypoproteinaemia, uraemia, metabolic acidosis, hyperkalaemia, anaemia

82
Q

what is the effect of hypoproteinaemia on anaesthesia?

A

increased free fraction of drug and decreased oncotic pressure means accidental overdose is possible

83
Q

what is the effect of uraemia on anaesthesia?

A

causes CNS depression

84
Q

what is the relevance of metabolic acidosis on anaesthesia of patients with kidney disease?

A

decreased renal excretion of drug
myocardial dysfunction

85
Q

what is the relevance of hyperkalaemia on anaesthesia of patients with kidney disease?

A

potentially life-threatnening - measure potassium throughout

86
Q

what is the relevance of anaemia on anaesthesia of patients with kidney disease?

A

oxygen-carrying capacity may be compromised

87
Q

what are the anaesthetic considerations for renal patients?

A

pre-op bloods important to ascertain current function of kidneys, full clinical exam

pre-op planning - fluids to maintain circlating volume and hydration

avoid stress

select drug which have minimal effect of CVS and renal function/BP

careful patient monitoring throughout

88
Q
A

Applied Clinical Veterinary Nursing (31 decks)

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