Anaesthesia for pre-existing conditions Flashcards
What is the intracranial cavity filled with?
brain (80%), CSF (10%)
and blood (10%)
How much cardiac output does the brain recieve?
15%
What is normal intercranial pressure?
5-12mmHg
What are clinical symptoms of raised inter-cranial pressure?
Papilledema, abnormal pulsing of retinal vessels,
depression, stupor, coma
What are the main aims when anaesthetising animals with neurological/brain trauma?
Maintain cerebral blood flow and reduce increases in ICP
What happens when ICP increases?
- 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
Why does the Cushings reflex occur?
because of the reduction in cerebral blood flow and hopes to decrease intracranial volume/ pressure
What signs are there of Cushings reflex?
brady cardia and hypertension, irregular breathing/apnoea
How can we avoid/control ICP?
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
What are the general considerations for a neurological patient?
- 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
What should you consider with the use of opioids ina neurological patient?
–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)
What should you consider when using a benzodiazepine for a neurological patient?
can reduce anxiety, but somewhat unpredictable. Will have no adverse effects on ICP, respiratory or CV system
What patients can you give ACP to?
intracranial pathology
What can ACP cause in neurlogical patients?
will cause systemic vasodilation, which causes hypotension and cerebral vasodilation. Vasodilation will increase ICP so may be best to AVOID
What can alpha-2s cause?
significant cardiopulmonary dysnfunction, will increase MAP and a bradycardia which will mask Cushing’s reflex, vomiting in cats
What can ketmain cause?
neuroprotective properties and fewer cardivascular and respiratory depressive effects
What are the general considerations for NUEROLOGICAL PATIENT?
- 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
Why might you need to do a GA for a neurological patient?
- 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)
Where are CSF taps taken from?
Cisterna magna or Lumbar
Which CSF tap location has then neck bent?
cisterna
What are the airway considerations for neurological patient?
- Lateral intubation – neck instabilities
- Avoid coughing- must be deep enough plane prior to intubation
- CSF tap- positioning? Problems for the ETT?
How can you monitor a seizure patient?
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
How should you nurse a patient with a neuromuscular disorder?
- 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
What are the considerations for planned gasto-intestinal surgery?
- Stabilise patient
- May be dehydrated/ anorexic
- May have acid base disturbances
- Potential for GOR / AP
- PAINFUL!
- Limited access to head
What are the anaesthetic consdierations for planned GI surgery?
- 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
What are the considerations for an emergency GI surgery?
- 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
What are the consideratiosn for GDV?
- 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!
What is the formula for blood pressure?
blood pressure = cardiac output X systemic vascular resistance
What causes reduced cardiac output?
dehydration and hypovolaemia
What should you consider with a patient who has pre-existing disease?
- 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
Nursing considerations for geriatric patient with pre-existing conditions?
- 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,
What is the function of the liver?
- 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
What are some examples of hepatic dysfunction?
- Porto-systemic shunt
- Biliary obstruction/trauma
- Chronic disease
- Acute failure
- Neoplasia
What can hepatic dysfunction be associated with?
- Ascites/ oedema/ pulmonary oedema (hypoproteinaemia/ hypoalbuminemia)
- Pu/ pd
- Anaemia
- Hypocalcaemia
- Hypoglycaemia
- Hypothermia risk
- Reduced clotting times
- Acid base disturbances
- Jaundice
- Encephalopathy
What is hepatic encephalopathy?
A collection of neurological abnormalities which can occur due to hepatic disease
What are the signs of hepatic encephalopathy?
increased levels of toxins, including ammonia, in the blood as the liver can not process it properly and so it builds up and up
How do you treat/stabilise hepatic encephalopathy?
reduce ammonia levels in the blood via absorption or reduction
What are patients with liver dysfunction prone to?
hypothermia and hypoglycaemia
What affects does liver dysfunction have on anaesthesia?
-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
How do you manage the hepatic patient?
- 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
How can you nurse a patient with a coagulopathy?
- Care with venepuncture- use periphery not central vein!
- Pressure after samples/ IV catheters
- Avoid rough handling/ pulling leads
- Avoid trauma – i.e. excited recoveries
What pre-anaesthetic lab tests can you perform?
- Liver enzymes
- Bile acids
- Clotting function
- Urea
- Plasma proteins
- Glucose
What is insulinoma?
Pancreatic islet cell tumour
What medical treatment can you give for insulinoma?
prenisoone, diazoxide, glucose
What surgery can you perform for insulinoma?
aparotomy partial pancreatectomy
What are the post-op considerations for a patient who has hd surgery for insulinoma?
pancreatitis, pain, hypoglycaemia
How can you monitor a patient after they have had surgery for insulinoma?
- Monitor blood glucose
- Avoid hyperglycaemia (stimulate insulin release) and hypoglycaemia
- May consider using neuromuscular blocking agent
- Post-operative pancreatitis
What are the pre-med considerations for a aptient with diabetes?
- Short acting drugs
- Good analgesia
- Avoid medetomidine (hyperglycaemia)
- Fluids inc glucose
- MONITOR BLOOD GLUCOSE
- Poss 2nd IV catheter
What are the considerations for a patient with hyperthyroidism?
- Usually elderly cats
- Multi-organ dysfunction
- Usually highly strung!
- Thin
- PU/PD
- Muscle weakness
- Hypertrophic cardiomyopathy
- Investigation and stabilisation essential
What are the anaesthetic considerations for a patient with hyperthyroidism?
- 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
What are the considerations for a patient having a thyroidectomy?
- Monitor blood pressure
- Location of surgery!
- Potential for laryngeal paralysis post-op
- Monitor for hypocalcaemia post-operatively
- Keep IV cannula in and patent
What are the considerations for canine hypothyroidism?
- Elderly dogs
- May have megaoesophagus
- Decreased GI motility
- Obesity
- Lethargy
- Bradycardia and hypotension
- Slow biotransformation of drugs
What is Cushings (hyperadrenocorticism)?
Pituitary or adrenal tumour – glucocorticoid excess
What are the considerations for a patient with cushings?
- 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
What are the considerations for hypoadrenocosticism? addisons
- Unable to mount normal stress response
- Hyperkalaemia
- Bradycardia
- Dehydration
- Weight loss
- Weakness/lethargy
- Often non specific clinical signs
- Stabilise before anaesthesia
- AVOID STRESS!
What are the effects of kidney disease on anaesthesia?
- 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
What are the considerations for the rena patient?
- 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?
