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ACVN - ANAESTHESIA > Anaesthesia for pre-existing conditions > Flashcards

Anaesthesia for pre-existing conditions Flashcards

1
Q

What is the intracranial cavity filled with?

A

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

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2
Q

How much cardiac output does the brain recieve?

A

15%

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3
Q

What is normal intercranial pressure?

A

5-12mmHg

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4
Q

What are clinical symptoms of raised inter-cranial pressure?

A

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

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5
Q

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

A

Maintain cerebral blood flow and reduce increases in ICP

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6
Q

What happens when ICP increases?

A
  • Compensatory mechanisms initiated when ICP
    increases, but can become exhausted if the
    pressure continues to build (ie haemorrhage)
  • CUSHINGS REFLEX
  • A reduction in blood flow causes an accumulation
    of carbon dioxide (Co2) as a result of poor perfusion.
  • Co2 is detected by the brain stem and the sympathetic nervous system responds by increase MAP, which in turn alerts baroreceptors and
    causes a reflex bradycardia
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7
Q

Why does the Cushings reflex occur?

A

because of the reduction in cerebral blood flow and hopes to decrease intracranial volume/ pressure

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8
Q

What signs are there of Cushings reflex?

A

brady cardia and hypertension, irregular breathing/apnoea

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9
Q

How can we avoid/control ICP?

A

Avoid coughing (anti tussive?)
- Avoid pulling on leads - utilise harnesses
- Careful intubation - adequate depth prior to attempt
- Avoid pressure on neck (during restraint)
- Avoid jugular sampling
- Avoid straining to defecate/ urinate

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10
Q

What are the general considerations for a neurological patient?

A
  • Pre-operative assessment (may include bloods, electrolytes, glucose, PCV,
  • Modified Glasgow Coma Scale (MGCS)
  • Stabilisation?
  • Drug choice- should not increase ICP or cause dramatic change to MAP
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11
Q

What should you consider with the use of opioids ina neurological patient?

A

–do not tend to alter cerebral blood flow or increase ICP to much and have minimal CV and respiratory depression. (avoid morphine/ hydromorphone as may increase incident of vomiting)

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12
Q

What should you consider when using a benzodiazepine for a neurological patient?

A

can reduce anxiety, but somewhat unpredictable. Will have no adverse effects on ICP, respiratory or CV system

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13
Q

What patients can you give ACP to?

A

intracranial pathology

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14
Q

What can ACP cause in neurlogical patients?

A

will cause systemic vasodilation, which causes hypotension and cerebral vasodilation. Vasodilation will increase ICP so may be best to AVOID

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15
Q

What can alpha-2s cause?

A

significant cardiopulmonary dysnfunction, will increase MAP and a bradycardia which will mask Cushing’s reflex, vomiting in cats

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16
Q

What can ketmain cause?

A

neuroprotective properties and fewer cardivascular and respiratory depressive effects

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17
Q

What are the general considerations for NUEROLOGICAL PATIENT?

A
  • Pre oxygenation may be beneficial
  • Ensure adequate depth prior to intubation (ie avoid coughing)
  • Isoflurane may slightly increase ICP whereas Sevoflurane wont!
  • capnography, BP, temperature etc
  • Maintain normocapnia
  • Fluid therapy
  • Mild head elevation to assist with venous drainage may be beneficial
  • Monitor for seizure activity
  • Careful handling and restraint- avoid jugular sampling/ pulling around neck (use harness not collars)
  • Avoid straining ie defaecation/ urination
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18
Q

Why might you need to do a GA for a neurological patient?

A
  • Imaging (MRI/ Myelography)
  • CSF tap
  • Spinal Surgery (hemilaminectomy/ ventral slot/ trauma)
  • For treatment of other issues not connected to neuro
  • patient may have pre-existing dx (epilepsy)
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19
Q

Where are CSF taps taken from?

A

Cisterna magna or Lumbar

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20
Q

Which CSF tap location has then neck bent?

A

cisterna

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21
Q

What are the airway considerations for neurological patient?

A
  • Lateral intubation – neck instabilities
  • Avoid coughing- must be deep enough plane prior to intubation
  • CSF tap- positioning? Problems for the ETT?
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22
Q

How can you monitor a seizure patient?

A

Often unknown cause
- Current medication/ anti-convulsant?
- Treat as if potential for increase ICP
- IV catheter essential
- Close monitoring before and after anaesthesia
- Capnography
- Blood pressure
- Risky phase? Post operative

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23
Q

How should you nurse a patient with a neuromuscular disorder?

A
  • May be pre-disposed to regurgitation and aspiration
  • Check gag reflex
  • Weakness may affect respiratory muscles
  • Capnography – may require IPPV
  • Rapid induction and recovery
  • Myasthenia gravis – exaggerated response to NMB’s
  • Consider local techniques
24
Q

What are the considerations for planned gasto-intestinal surgery?

A
  • Stabilise patient
  • May be dehydrated/ anorexic
  • May have acid base disturbances
  • Potential for GOR / AP
  • PAINFUL!
  • Limited access to head
25
Q

What are the anaesthetic consdierations for planned GI surgery?

A
  • Avoid drugs that may induce vomiting e.g. morphine
  • Pre-oxygenate
  • Suction available
  • Head elevated until ET tube inserted and cuff inflated
  • Removal per os or via thoracotomy
  • Rupture of oesophagus possible
  • Analgesia
  • Avoid nitrous
  • Care with heat preservation
26
Q

What are the considerations for an emergency GI surgery?

A
  • Stabilise prior to sx- but not too long!
  • AIM- improved CV and pulmonary function prior to GA
  • Decompress stomach if able
  • Emergency Surgery INCLUDING gastropexy
  • Arrhythmias common
  • Careful monitoring of cardiovascular system
  • Quick surgeon!
  • Good team of nurses
27
Q

What are the consideratiosn for GDV?

A
  • Pressure on diaphragm from distended viscus
  • Electrolyte and acid base abnormalities
  • Clotting abnormalities
  • Potential pneumothorax
  • Intensive care required post-operatively
  • Blood pressure often OK but perfusion poor – don’t be fooled!
28
Q

What is the formula for blood pressure?

A

blood pressure = cardiac output X systemic vascular resistance

29
Q

What causes reduced cardiac output?

A

dehydration and hypovolaemia

30
Q

What should you consider with a patient who has pre-existing disease?

A
  • May require sedation/ GA for diagnostic or surgical procedures
  • gastro-oesophageal reflux a risk- starvation times crucial
  • understand chronic disease
  • May be on medication already
  • May need special diet
  • May have electrolyte/ acid base disturbances- pre op bloods sensible
31
Q

Nursing considerations for geriatric patient with pre-existing conditions?

A
  • Large dog- positioning/ handling/ lifting/ may have
    OA/ may be on medication?
  • Chronic D+- may have electrolyte imbalances/ need
    reg opportunities to go
  • Procedure: needs lower GI scope= dirty op
  • Will need preparation – enema/ KleanPrep
  • Pain????
  • Nursing care: will have D+/ may need IVFT/ messy!/
    clip fur around tail/ clean up prior to recovery
    48 hour before procedure- starve and start KleanPrep
    solution
  • On day of admit: 2 x enema
  • Recheck bloods/ electrolytes on day
  • Place IV catheter in CEPHALIC NOT SAPHENOUS and
    maintain fluid therapy
  • PREMED: Opioid +/- acepromazine (or alpha 2)/ Propofol
    induction/ maintain Isoflurane via circle system.
  • Nursing; keep warm, padded bed, care with positioning,
    wrap tail and clip bottom, clean area reg, provide inco
    sheets,
32
Q

What is the function of the liver?

A
  • Production of substances – urea, clotting factors, albumin
  • Bilirubin excretion
  • Biotransformation of drugs/ toxins
  • Metabolism of carbs, proteins and fats
  • Function on glucose homeostasis- glycogen storage/ gluconeogenesis
  • Major metabolic organ- heat
33
Q

What are some examples of hepatic dysfunction?

A
  • Porto-systemic shunt
  • Biliary obstruction/trauma
  • Chronic disease
  • Acute failure
  • Neoplasia
34
Q

What can hepatic dysfunction be associated with?

A
  • Ascites/ oedema/ pulmonary oedema (hypoproteinaemia/ hypoalbuminemia)
  • Pu/ pd
  • Anaemia
  • Hypocalcaemia
  • Hypoglycaemia
  • Hypothermia risk
  • Reduced clotting times
  • Acid base disturbances
  • Jaundice
  • Encephalopathy
35
Q

What is hepatic encephalopathy?

A

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

36
Q

What are the signs of hepatic encephalopathy?

A

increased levels of toxins, including ammonia, in the blood as the liver can not process it properly and so it builds up and up

37
Q

How do you treat/stabilise hepatic encephalopathy?

A

reduce ammonia levels in the blood via absorption or reduction

38
Q

What are patients with liver dysfunction prone to?

A

hypothermia and hypoglycaemia

39
Q

What affects does liver dysfunction have on anaesthesia?

A

-Low albumin
- Reduced protein binding of drugs
- Oncotic pressure of blood ( harder to retain fluid in circulation )
- Potentially slower biotransformation of drugs
- Inc risk of surgical haemorrhage – coagulopathies
- Electrolyte imbalances- sodium retention and lower potassium

40
Q

How do you manage the hepatic patient?

A
  • Stabilise ( i.e. treat encephalopathy/ seizures)
  • Minimal premedication/ cautious dosing/ short acting/ antagonism? Induction: slow and titrate- use lowest dose
  • Analgesia
  • Avoid NSAIDS? (coag and hepatic/ renal)
  • Maintain body temperature
  • Monitor BG
  • Beware of coagulopathies
41
Q

How can you nurse a patient with a coagulopathy?

A
  • Care with venepuncture- use periphery not central vein!
  • Pressure after samples/ IV catheters
  • Avoid rough handling/ pulling leads
  • Avoid trauma – i.e. excited recoveries
42
Q

What pre-anaesthetic lab tests can you perform?

A
  • Liver enzymes
  • Bile acids
  • Clotting function
  • Urea
  • Plasma proteins
  • Glucose
43
Q

What is insulinoma?

A

Pancreatic islet cell tumour

44
Q

What medical treatment can you give for insulinoma?

A

prenisoone, diazoxide, glucose

45
Q

What surgery can you perform for insulinoma?

A

aparotomy partial pancreatectomy

46
Q

What are the post-op considerations for a patient who has hd surgery for insulinoma?

A

pancreatitis, pain, hypoglycaemia

47
Q

How can you monitor a patient after they have had surgery for insulinoma?

A
  • Monitor blood glucose
  • Avoid hyperglycaemia (stimulate insulin release) and hypoglycaemia
  • May consider using neuromuscular blocking agent
  • Post-operative pancreatitis
48
Q

What are the pre-med considerations for a aptient with diabetes?

A
  • Short acting drugs
  • Good analgesia
  • Avoid medetomidine (hyperglycaemia)
  • Fluids inc glucose
  • MONITOR BLOOD GLUCOSE
  • Poss 2nd IV catheter
49
Q

What are the considerations for a patient with hyperthyroidism?

A
  • Usually elderly cats
  • Multi-organ dysfunction
  • Usually highly strung!
  • Thin
  • PU/PD
  • Muscle weakness
  • Hypertrophic cardiomyopathy
  • Investigation and stabilisation essential
50
Q

What are the anaesthetic considerations for a patient with hyperthyroidism?

A
  • Avoid stress!
  • ?Sedation opioid+/- ACP
  • ?Avoid ketamine (increases myocardial work
    load and increases HR) and medetomidine
    (drops CO)
  • IV induction if possible
  • Monitor ECG
  • IV fluids
51
Q

What are the considerations for a patient having a thyroidectomy?

A
  • Monitor blood pressure
  • Location of surgery!
  • Potential for laryngeal paralysis post-op
  • Monitor for hypocalcaemia post-operatively
  • Keep IV cannula in and patent
52
Q

What are the considerations for canine hypothyroidism?

A
  • Elderly dogs
  • May have megaoesophagus
  • Decreased GI motility
  • Obesity
  • Lethargy
  • Bradycardia and hypotension
  • Slow biotransformation of drugs
53
Q

What is Cushings (hyperadrenocorticism)?

A

Pituitary or adrenal tumour – glucocorticoid excess

54
Q

What are the considerations for a patient with cushings?

A
  • May be iatrogenic
  • Poor muscle tone – why is this a problem?
  • May be overweight and lethargic
  • Poor thermoregulation
  • Bruising
  • Risk of pulmonary thromboembolism – hypercoagulability
  • PU/PD Na retention, K excretion
  • Risk of wound infection
  • May or may not be on medical treatment
55
Q

What are the considerations for hypoadrenocosticism? addisons

A
  • Unable to mount normal stress response
  • Hyperkalaemia
  • Bradycardia
  • Dehydration
  • Weight loss
  • Weakness/lethargy
  • Often non specific clinical signs
  • Stabilise before anaesthesia
  • AVOID STRESS!
56
Q

What are the effects of kidney disease on anaesthesia?

A
  • Hypoproteinaemia
  • Increased free fraction of drug
  • Decreased oncotic pressure
  • Uraemia
  • CNS depression
    Metabolic Acidosis
  • Decreased renal excretion of drugs
  • Myocardial dysfunction
  • Hyperkalaemia
  • Potentially life-threatening – acute v chronic!
  • MEASURE POTASSIUM
  • Anaemia – oxygen carrying capacity may be compromised
57
Q

What are the considerations for the rena patient?

A
  • Pre op bloods- ascertain current function of kidneys
  • Planning- could patient require fluids PRE operatively? (maintain circulating volume and maintain hydration)
  • Full clinical exam
  • Avoid stress
  • Select drugs that have minimal effect on CV and renal function/ BP Careful patient monitoring
  • Feed at home?

ACVN - ANAESTHESIA (12 decks)

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