Anaesthesia in animals with pre-existing disease Flashcards
What is the monroe Kellie hypothesis?
Is a pressure-volume relationship that aims to keep a dynamic equilibrium amoung the essential non-compressible components inside the rigid compartment of the skull
When may the blood brain barrier be disrupted?
Trauma
Inflammation
Hypertension
What % of the co does the brain receive and why?
15% because it has a high metabolic rate
What is intercranial pressure influenced by?
Cerebral perfusion pressure
PaCO2
PaO2
Cerebral metabolic activity
What is the cushings reflex?
Nervous system response to increased intercranial pressure
Cushings traid of increased blood pressure
Irregular breathing
Bradycardia
What can be used to reduce intercranial pressure?
Mannitol osmotic diuresis
What are the clinical signs of increased intercranial pressure?
Seizures Odema around the optic nerve Subdued Depressed mentation Reluctant to move
What is cerebral percussion pressure and what can it be influenced by?
Pressure gradient between MAP and ICP
Cerebral blood flow is autoregulated MAP 50-150mmhg
Coughing, vomiting, pressure on the jugulars increases venous outflow pressure
Why is it important to control PaCO2 in a neuro patient?
Every 1mmhg increase in co2 there’s a 4% increase in cerebral blood flow
At what parameters should you maintain CO2 at during anaesthesia for a neuro patient?
30-45mmhg
What steps may you take to decrease CO2 during anaesthesia in a neuro patient?
Ventilate
Pre-oxygenate before surgery
What should be avoided when placing an ET tube in a neuro patient?
Coughing raises ICP
What is intracerebral steal?
Damaged area loses ability to autoregulate whenundamged are vasodilates blood is shunted away from damaged area
What is inverse steal in the brain?
Damaged areas cannot auto-regulatevasoconstriction if un damaged area leads to blood shunted towards the damaged areas
Why should hypoxia be avoided in a neuro patient?
It will cause dilation
Consider 100% oxygen for recovery
Why should hypothermia and barbiturates be avoided in a neuro patient?
Will decrease cerebral activity
What are the effects of ACP and dexmedotomidine and which one should be used in a neuro patient?
Dexmeditomidine
Initial hypertension maintains MAP below 150mmHg
Cerebral protection
Can get vomiting
Acepromazine
Peripheral vasodilation can increase cerebral blood flow and intercranial pressure
Which inhalation agent should be used in a neuro patient and why?
Sevoflurane
Cerebral protectant
Why should neuro patients be handled and positioned carefully?
Harness to reduce pressure on jugular veins
Keep head elevated to improve cerebral venous drainage
Why should fluid balance be carefully monitored in the neuro patient?
Hypertension can increase intercranial pressure
Hypotension can limit the blood supply to the brain (vasodilation)
What should also be monitored for in the neuro patient?
Seizures
How should an anaesthetic patient be monitored if they have a clinical history of seizures?
Be aware of the current medication
Phenobarbital can induce hepatica enzymes
Potassium bromide causes and electrolyte abnormality
Iv carheter essential
Close monitoring before and after anaesthesia
Capnography
Blood presure
What must be considered when anaesthetising a neuromuscular disorder patient?
Pre-disposed to regurgitation and aspiration
Check gag reflex
May affect respiratory muscles
Capnography may require IPPV
What is important to consider when anaethetising and myasthenia graves patient?
Exxagerated response toNMB agents
What is important to consider in patients being anaesthetised who have an oesophageal foreign body?
Tube may be damaged during surgery or need to be removed
Stabilisation before
Dehydration( not been able to drink)
Potential for regurgitate and aspiration
Pre-oxygenation
Suction available
Keep the head elevated until the ET tube is inserted and cuff inflated
Possible rupture of the oesopagus
Analgesia
What are important considerations for the GI foreign body anaesthetised patient?
Fluid balance disruptions hypovolamia acid base electrolytes dehydration Avoid vomiting inducing drugs Potential regurgitate and aspiration Slow release of fluid from the abdomen Hypothermia Monitor respiratory rate carefully
What are the considerations for the GDV patient undergoing anaesthesia?
Shock, stabilise first fluids Decompress stomach Arrhythmias Careful monitoring cardiovascular system Hypotension Pressure on the diaphragm from distended viscous Clotting abnormalities Possible pneumothorax Intensive post-op care
What are the important considerations for the colic surgery horse being anaesthetised?
Electrolyte and acid base imbalance Hypovolameia shock Dehydration Cardiovascular arrhythmia Very painful! Analgesia-NSAIDs, Xylazine, opioids Decompress stomach Distended viscera pressure on the lungs risk of rupture Endotoxamia Fluids-Hartmanns, 7.5% Nacl, colloids
What conditions can affect the livers function?
Acute liver failure
Portosystemic shunt
Billary tract obstruction/trauma
Chronic disease
What is the livers function?
Clotting factors Production plasma proteins Drug and hormone bio transformation Bilirubin excretion Urea production 80% of the blood supply passes through the portal vein
What are liver patients at risk of during surgery?
Hypothermia
Hypoglycemia
Haemorrhage
Increased free fraction of drugs (less plasma proteins to bind to)
Decreased hepatic clearance of drugs
Water and sodium retention, potassium loss
What are the effects of anaesthesia on the liver function?
Hypotension-decreased perfusion
Hepatotoxicity
Enzyme induction
Pre-anaesthetic laboratory tests required for the liver
Liver enzymes Bile acids Clotting function Urea Plasma proteins Glucose
What are the general considerations for a anaethetised liver patient?
Thermoregulation Medical management encephalopathy Monitor blood glucose Blood pressure Maintain adequate renal perfusion Monitor blood loss Avoid hypoxia and hyopercapnia CVP Use of short acting drugs Monitor individual animal response
What considerations should you make for an anaethetised insulinoma patient?
Monitor glucose 5% dextrose infusion Pain!! Medical management-prednisalone, diaoxide, glucose Avoid hyperglycaemia and hypoglycemia May consider NMB agent Post-operative pancreatitis
What considerations must we make for a diabetic patient undergoing anaesthesia?
Stabilise prior to surgery- ketosis, dehydration, weight loss, fatty liver
Feed asap after surgery
Postpone fasting for as long as possible
Glucose infusion if required
Avoid hypoglycemia and hyperglycaemia
Monitor temperature
Give half dose insulin before the procedure then half dose once eaten afterwards
Know the routine at home (favourite food)
1st patient of the day
Fluids include glucose
Avoid medetomidine(hyperglycemia)
Good analgesia
Short acting drugs
Poss 2nd iv
What considerations should we make for the anaesthetised hyperthyroid patient?
Difficult to handle Easily stressed IM sedation then IV Sedation with opioids and ACP Avoid ketamine and medetomidine Iv induction Consider chamber Iv fluids Monitor ECG Fast metabolism Prone to hypothermia PUPD Thin Muscle weakness Hypertrophic cardiomyopathy
What considerations should we make for the anaesthetised patient undergoing a thyroidectomy?
Monitor blood pressure Monitor other parameters for depth of anaesthesia as surgery located at the head end Potential laryngeal paralysis post op Monitor for hypocalcemia Keep Iv in and patent
What considerations should we make during anaesthesia for the hypothyroid patient
Prone to hypothermia May have megaoesophagus Decreased GI motility Obesity Lethargy Bradycardia and hypotension Slow biotransofrmation of drugs
What considerations should we make for hyperadrenocortisim?
Cushings Poor muscle tone Overweight Lethargic Poor thermoregulation Bruising Risky of pulmonary thromboembolism Hypercoagulability PUPD sodium retention potassium excretion Risk of wound infection and dehiscence
Hypoadrenocortisim considerations for the anaesthetised patient?
Addisions Lack of cortisol production. Hyperkalaemia Dehydration Bradycardia Weight loss Weakness Lethargy Stabilise before anaesthetic
Why is jaundice a problem in the anaesthetised patient?
Neohrotoxic
Why might hypoalbmenia be a problem in an anaesthetised patient?
More free fraction of drugs
Albumin binds the anaesthetic drugs
Why may hypotension be a problem in the liver diseases anaesthetised patient?
Reduced hepatic perfusion
Hepatocellular compromise
What drug is recommended for analgesia in the liver patient?
Pethidine usually lasts 1-2 hours can last up to 24 hours in a hepatic compromised patient
What other drug should be avoided if an insulinoma patient is already receiving prednisalone?
NSAIDS
What may hyperthyroid cats be predisposed to before surgery?
Arrhythmia
What does obesity increase the risks of in anaesthesia?
Ventilation compromised
Regurgitate and aspiration
What is it important to encourage a hyperadrenocortisim patient to do after surgery?
Mobilise
What is an hypoadrenocortisim patient unable to do?
Mount a stress responses
