Anaesthesia Flashcards
What type of physiological changes are expected with liver disease which may have an impact on anaesthesia and surgery?
- Altered pharmacokinetics of anaesthetic drugs
- Altered glucose metabolism
- Reduced albumin production
- Increased bleeding tendencies
- Jaundice
- Hepatomegaly
What features of gastrointestinal disease should be taken into account during anaesthesia?
- Disturbances in fluid, electrolytes, acid-base balance, and protein levels
- Hypovitaminosis, weight loss, and emaciation
Why should morphine and alpha2-agonists be avoided in patients with gastrointestinal disease?
- These drugs induce nausea and vomiting
What modulates cerebral vascular resistance (CVR)?
Blood-gas values, especially PaCO2
What is the cerebral perfusion pressure?
- Difference between carotid arterial blood pressure and jugular venous pressure
- Cerebral perfusion pressure (CPP) is defined as the difference between the force driving blood into the brain (mean arterial pressure [MAP]) and the force resisting movement of blood into the brain (intracranial pressure [ICP] or central venous pressure [CVP], whichever is the highest).
What is the Monro-Kellie Hypothesis?
Any increase in volume in either of cellular component, ventricles, and blood vessels of the brain has to have a reciprocal decrease in the other two, or the intracranial pressure will rise
What is the cerebral central venous pressure (CVP)?
Pressure that resists movement of blood into the brain
Describe the physiological changes severe hyperventilation will cause in the brain.
Severe hyperventilation decreases CO2 pressure. A decrease in PaCO2 will cause vasoconstriction of cerebral blood vessels. Thus, a reduction in PaCO2 by hyperventilating can cause a rapid decrease in cerebral blood flow and intracranial pressure.
Describe the physiological changes severe hypoventilation will cause in the brain.
Severe hypoventilation will cause an increase in PaCO2 and will result vasodilation of cerebral vessels and increase in cerebral blood flow and intracranial pressure
How is cerebral blood flow calculated?
[Cerebral perfusion pressure]/[cerebral vascular resistance]
What are some options for treating intracranial hypertension?
- Minimize central venous pressure
- Modest hyperventilation
- Use of diuretics
- Use of steroidal anti-inflammatories
- Use of cytoneuroprotectives
- Induction of hypothemia
- Craniotomy
What are some methods to minimize central venous pressure in the brain perioperatively?
- Use of head-up position
- Avoidance of fluid overload
- Avoidance of coughing and gagging (causes the vessels in the head to expand)
What is Mannitol?
- Osmotic diuretic
Name a steroidal anti-inflammatory.
Methylprednisolone
How can occular immobility be achieved for occular surgery?
- Stay sutures
- Retrobulbar block
- Deep anaesthesia
- Neuromuscular block
What is the occulo-cardiac reflex?
Decrease in pulse rate associated with traction applied to extraocular muscles (media rectus muscle, for example) and/or compression of the eyeball
What should be considered when formulating an anaesthetic plan for an animal with endocrine disease?
- Chronicity of the disease
- Severity of the disease
- Physiological pertubations caused by the disease
- If the condition can be stabilized before anaesthesia
- If the condition will be destabilized by the anaesthesia
- If there are any contraindications for loco-regional anaesthesia
Why must a hyperkalaemic patient be stabilized for anaesthesia? How can this be achieved?
- A hyperkalaemic patient will be more likely to produce action potentials and changes the resting potential of the heart
- Treament
- Treat the underlying problem
- Administer calcium
- Administer bicarbonate therapy
- Moves the potassium ions into the intracellular space
- Administer glucose and insulin therapy
- Moves the postassium ions into the intracellular space
Why should metabolic acidosis be considered when making an anaesthetic plan?
Metabolic acidosis decreases excretion of certain drugs in the kidney
How should ureaemia be considered when making an anaesthestic plan?
Uraemia causes reduced protein-binding which allows more free drug to be available
What cardiovascular changes occur during pregnancy?
- Decreased systemic vascular resistance
- Increase in heart rate and stroke volume
- If heart rate is not able to increase something else will have to decompensate
- Uterine contractions
- Cardiac output with changes to uterine flow
- Decreased cardiac reserve
- Oxytocin release
- Increases blood flow to uterus to increase vasodilation and hypertension
What haematological parameters change in the female during pregnancy?
- Increase in blood volume
- Increase in plasma volume
- Increase in red blood cell mass
- Decrease in haemaglobin and PCV
- Decrease in oxygen-carrying capacity
- Uterine blood reservoir increases
What is Mendelson’s Syndrome?
- Chemical pneumonitis caused by aspiration during anaesthesia
What should be part of the anaesthetic plan to manage gastrointestinal conditons caused by pregnancy.
- Full stomach should be avoided
- Metoclopramide (prokinetic) given iv
- Maropitant (anti-emetic) can be administered
- Antacids can be administered
- H2-antagonist (such as Ranitidine) can be administered
Describe some pulmonary changes that occur with pregnancy.
- Increase in oxygen consumption
- Reduction in total pulmonary resistance
- Increase in dead space
- Reduciton in functional residual capacity
- Increase in circulating progesterone and endorphins
- Reduces minimal alveolar concentration (concentration of the vapour in the lungs that is needed to prevent movement (motor response) in 50% of subjects in response to surgical (pain) stimulus.)
What gastrointestinal changes accompany pregnancy?
- Decrease in gastric volume
- Increase in gastric pressure
- Lower oesophageal tone
- Decreased gastric motility
- Increase in gastrointestinal acid, chloride, and enyzmes
What hepatic changes accompany pregnancy?
- Reduction in plasma proteins
- Slight increase in liver enzymes
- Decrease in plasma cholinesterase
What renal changes accompany pregnancy?
- Increase in renal blood flow and increase in glomerular filtration rate
Describe the changes that occur to uterine vasculature during pregnancy.
- Decreased uterine blood flow (UBF)
- Causes hypotension, hypovolemia, uterine manipulation, contractions, anaesthesia
- Increase in uterine vasculature resistance (UVR)
What are the most important factors to keep in mind when creating an anaesthetic plan for a pregnant female?
- There is a reduced cardiac reserve in these patients
- There is reduced functional residual capacity (FRC) and O2-carrying capacity
- There is a large increase in risk of regurgitation
- Nephrotoxic drugs should be avoided
- There is increased sensitivity to inhalants and local anaesthetics
What are some good induction agents for pregnant patients?
- Alfaxalone
- Midazolam and lidocaine as co-induction agents
- Fentanyl
List some ways in which hypothermia can impair cardiac function.
- Causes shivering and increases oxygen utilization
- Depresses ventilation
- ‘Left shifts’ oxygen-haemaglobin disassociation curve (ODC)
- Arrhythmogenic
