CAL: How do we anaesthetise this animal? Flashcards
Why is anaemia a problem in anaesthesia? Actions?
The oxygen content of the blood will be reduced and CO will need to be increased to maintain adequate oxygen delivery. Most anaesthtics reduce CO and this may reduce oxygen delivery to a critical level in anaemic patients. Blood transfusion may be necessary - depends on underlying cause, acute/chronic anaemia and whether there is ongoing blood loss.
Are acute or chronic anaemic patients likely to be more tolerant of anaesthesia?
Chronic - due to a rightward shift in the oxyhaemoglobin dissociation curve (due to increased 2,3-diphosphoglycerate levels).
What would you have to do to anaesthetise a patient with MVD resulting in CHF?
The ondition should be stabilized before anaesthesia. Anaesthesia should aim to produce mild reductions in systemic vascular resistance (to promote forward flow of blood and reduce regurgitant fraction), mild increases in HR, with avoidance of bradycardia and hypertension.
When can cyanosis be detected clinically?
clinically when haemoglobin is 75-85% saturated, but at least 5g deoxyHb/100ml blood is a requirement (so not obvious in anaemia). Clinical detection also depends on lighting conditions, skin/MM pigmentation and perfusion of the area examined.
Will pulmonary oedema affect the risk of anaesthesia?
Yes
What actions should you take to anaesthetise a patient with pulmonary oedema?
find out and treat the cause of the pulmonary oedema (often CHF) before anaesthesia is induced, usually diuretic Tx. Pre-oxygenation is essential, (flow-by, facemask, or oxygen cage).
When does hypoproteinaemia usually become clinically detectable?
in very severe cases only
How does hypoproteinaemia affect anaesthesia? 2
- Changes in albumin concentrations will affect the amount of free/bound drugs. Many anaesthetic agents are highly protein bound (e.g. propofol is 98% albumin bound) and hypoalbuminaemia will increase the amount of free (unbound) drug greater response with a given dose.
- Also, plasma proteins maintain colloid oncotic pressure, so that there is a risk of oedema if albumin concentrations are < 20g/litre.
Define azotaemia
is blood urea ~>10mmol/litre OR creatinine ~>200mmol/litre
When do you see azotaemia? 2
renal failure
dehydration
How does acidosis due to azotaemia affect anaesthesia?
Concurrent acidosis increases free drug concentrations, changes resting membrane potential (resulting in myocardial depression), O2 dissociation curve shifted to the right (reducing oxygen affinity). There may also be changes in serum K+ concentrations, which will also affect myocardial contractility and excitability
What might you need to do preoperatively in patients with azotaemic patient?
give IV fluids (to increase GFR and induce diuresis)
What could be the cause of oxygen pressure gauages pointing to zero? 2
no oxygen left in any of the attached tanks OR neither valve has been turned on to allow the oxygen to flow into the machine
What analgesia might be provided in addition to the anaesthetics for a dog castrate? 3
- an opioid in the pre-anaesthetic medication (such as buprenorphine)
- a NSAID (such as carprofen)
- intratesticular injection of lidocaine once asleep.
What is a T piece?
a part of anaesthetic equipment connecting the 2 pipes.
