Anaesthesia Flashcards
Define GA
state of unconciousness produced by controlled reversible drug induced intoxication of the CNS so that the patient neither perceives or recalls the noxious stimuli
Define anaesthesia
loss of sensation due to pharmacological depression of nerve function
define local anaesthesia
temporary blockage of sensory nerves (usually with simultaneous block of motor nerves)
5 components or outcomes of GA?
Aims > unconsciousness > analgesia (anti-nociception) > muscle relaxation Controlling side effects - homeostasis - normal oxygen delivery
What is the main side effect of anaesthesia?
- CV and respiratory depression
- homeostatic depression (baroreceptor reflex, pulmonary hypoxic response esp important in horses)
- Specific drug effects (eg. NSAIDs and renal function - PGs needed for vasodilation to maintain blood flow)
What may pre-anaesthesia blood tests tell you?
- baseline values
- rarely actually influence anaesthetic protocol
- insensitive for measuring subclinical disease (>2/3 kidney tissue lost before urea^ in blood)
- good for risk animals or before major surgery
What is anaemia? Impact on GA?
- low Hbg or PCV
-> v o2 delivery to tissues (oxygen delivery = CO x o2 content; o2 content =(1.36 x Hb x SaO2%) + (PaO2 x 0.003) - transfusion triggers:
5-8g/dL [Hb]
PCV <20%
How may low plasma protein affect anaesthesi? Which drug is this escpecially important for?
- changes in ratio free: protein bound drug (esp. PROPOFOL 98% albumenbound)
- oncotic pressure -> oedema and ow BP
How is kidney failure defined by haematology parameters?
- BLood urea >10mmol/l
- creatinine >2–mmol/l
- concurrent acidaemia (^ free drug concentrations, depresses myocardial contractility.. MOER THINGS FIND SLIDE
5 reasons for anaesthesia?
- restraint (esp wild animals)
- surgery
- diagnostics
- therapy
- legal requirements
What is the triad of anaesthesia?
Unconciousness (narcosis)
Analgesia (anti-nociception)
Muscle relaxation
WHat physiological system must be carefully stabilised during anaesthesia? Why?
Cardiovascular (esp in underlying disease)
- with poor analgesia noxious stimuli can cause harmful autonomic responses and involuntary movement
What is the main aim of the anaesthetist?
Maintain oxygen delivery to tissues at the same time as prividing the three components of the triad
How do modern anaesthetic drugs differ from historical anaesthesia?
“Lighten up” - drugs should allow rapid onset, rapid recovery and rapipd responses to changes in delivered doses
Which anaesthetic drug is highly albumen bound?
Propofol >90%
Which breed are senstitive to acepromazine?
BOxers
Which breeds are more prone to airway obstruction?
brachycephalic
which animals may be difficult to estimate weight?
- fluffy breeds! Weigh!
How long after a meal should you wait before anaesthesia?
- dogs/cats 6 hours (unless emergency)
- horses 12hours
- birds and rabbits none
WHat signs in the patient history may indicate potential anaesthesia risks?
- cough
- excercise intolerance
- PUPD (kidney, liver or endocrine disease, pyometra)
- VD+ fluid and electrolyte imblanaces
- trauma (potential for ruptured diaphragm, bladder, traumatic myocarditis)
- seizures or syncope (CNS disease - may repsond strangely to anaesthetic drugs)
- concurrent drug tx (NSAId, steroids, ACEI, pimobendan)
Which way does the eye roll on induction?
Down and medially
What are the death rates of anaesthesia in different animals?
- 1/2000 dogs
- 1/1000 cats
- 1/100 rabbits
- 1/25 guinae pigs
What is TIVA?
- Total IV anaesthesia
MOrbidity asociated with anaesthetic?
- mm and nn damage (esp horses)
- cerebral hypoxia -> poor recovery (esp SA) and post op cognitive dysfunction
> eg. post-op blindness in cats after dentals due to maxillary a. crushing by jaw hyperextension - peripheral n damage/CNS damage
- renal dysfunction due to v BP
WHat factors influence risk of anaesthesia?
- physical status (ASA grade I-V)
- temperament
- staff available
- facilities available
- what youre used to!
What are the exposure limits according to COSHH regulations for anaesthetic gases?
NO 100ppm Sevoflurane 60ppm Isoflurane 50ppm Halothane 10ppm > monitor waste gases every 12 months
How can gas exposure be minimised?
- machine and vapourisers egularly serviced
- avoid mask and chamber inductions
- ensure endotracheal tube cuff properly inflated
- fill vapourisers at end of day
- caps back on!
- leave patient attached to circuit at end of anaesthesia
- flush circuit with oxygen and dump the bag into the scavenging system
- use low gas flow techniques
