w/c 27-Jan-14 Flashcards
What are the three components of general anaesthesia?
1) unconsciousness -narcosis = lack of awareness
2) Analgesia (pain is a conscious perception) - antinocieption
3) Muscle relaxation
What is ‘balanced anaesthesia’
A movement away from using a single drug to do all three components we want from a GA.
It is a combination of drugs which reduces the side effects; allows ‘lightening up’
Which breed is said to be sensitive to acepromazine (ACP)?
Boxers are said to be susceptible to ACP
ACP is a sedative and an antiemetic
How many hours should be waited till GA in induced in dogs and cats?
Withhold food for 6 hours
According to statistics, which species is more likely to die under anaesthetic; cat or dog?
Healthy Cat: 1 in 895 die
Healthy Dog: 1 in 1849 die
Guinea Pig: 1 in 26 die
In the context of anaesthesia, what is the ASA score?
ASA score is a measure of the animals physical status
Dangers of nitrous oxide
More dangerous and can inhibit DNA synthesis and cause CNS damage.
What is the recommended maximum concentrations of anaesthetic gases?
Nitrous oxide:100ppm
Sevoflurane: 60ppm
Isoflurane: 50ppm
Halothane: 10ppm
A blue cylinder probably contains what gas?
What is important about this gas?
Nitrous oxide
Stored in a liquid phase with gas on the top. As long as some liquid is left, will always have a +ve pressure gauge. HAVE TO WEIGHT to determine amount left.
Significance of the Bodok seal
Must be placed between cylinder and anaesthetic machine to make a gas-tight join.
VERY LOAD NOISE if missing when cylinder turned on
Why does the vaporizer need to be kept upright?
Otherwise the bypass channel may flood with anaesthetic and dramatically increase output = DANGEROUS
Why do you need to be careful using emergency oxygen flush?
Oxygen is given at a pressure of 400kPa directly from the cylinder.(40 litres/minute)
Higher pressure= careful LUNG DAMAGE
What is a ‘low-resistant’ or ‘draw-over’ vaporizer?
Patients respiratory effort determines amount of anaesthetic agent breathed in.
Vaporiser is positioned WITHIN the anaesthetic circuit.
Anaesthesia too light = increased respiratory effort = sleep!
Advantage/Disadvantage of rebreathing system
ADVANTAGE: exothermic reaction when CO2 react.
Low volatile agent consumption
Most economical in large animal
DISADVANTAGE: Exact composition of gas is not known
Expensive
Slow to change depth of anaesthesia
Advantage/Disadvantage of non- rebreathing system
ADVANTAGE: Simple/cheap, inspired air composition is known, low resistance to breathing
DISADVANTAGE: High gas flow requirements
Expired heat loss
Breathing/Non-Rebreathing system can change depth of anaesthesia more quickly
Non rebreathing systems can change depth of anaesthesia more quickly
Which type of breathing system allows for heat to be retained?
Exothermic reaction between carbon dioxide and soda lime = REBREATHING SYSTEMS can RETAIN HEAT.
Most economic in large animals
Which set is best as IPPV?
IPPV: Intermittent Positive Pressure Ventilation
How are non-rebreathing sets classified?
Rebreathing of carbon dioxide is prevented by having enough fresh gas flow (FGF) into the circuit to wash away exhaled gas from previous exhalation.
Classified depending on FGF (Classification from A to F)
Which is the best sets for IPPV?
MAGILL and LACKS (not good for IPPV, as Mapleson classification A, need to increase FGF)
AYRE’ST PIECE/ BAIN (better for IPPV) as don’t need to increase FGF
IPPV: INTERMITTENT POSITIVE PRESSURE VENTILATION
Which set would be given for animals <10kg?
Ayre’ T-piece.
Good choice for IPPV (as already high FGF)
Low resistance to breathing.
When is the breathing set Humphrey ADE used?
Versatile system, by means of a lever switch system can be conversed from a Mapleson A to a Mapleson D or E.
i.e. A: good for spontaneous respiration
D/E good for controlled respiration
Why can circle rebreathing systems only be used in animals >10kg?
Gas can only move in one direction (i.e. a circle!)
Two way valves are present. Resistance to breathing is higher
What breathing set would you use for a 6kg Jack Russel?
Tpiece
minimal resistance
How do you calculate FGF?
FGF: Respiratory Rate x Tidal Volume x Circuit Factor
During a laporotomy the monitor shows
A falling blood pressure and rising pulse would be indicitive of what?
Hypovolemia
e.g. haemorrage?
When is the wet/dry/warm/cold quadrant used? What do the terms relate to?
In the absence of best evidence i.e. less common cardiac diseases.
Warm: output/circulatory signs
Wet: Congestive signs.
In the absence of best evidence, which drugs would be given for a COLD DRY patient? (CVS)
Cold: Poor circulation
Dry: No congestion
Afterload reduction, anti-arrythmics, inotropes
What is the main evidence of excessive a) preload
b) afterload
Excessive Preload: Congestion i.e. Pulmonary oedema
Excessive Afterload: Pale/Cold patients (increased resistance to ejection)
How do calcium channel blockers help improve diastolic function?
Calcium channel blockers hasten relaxtion (I.E. calcium antagonist- Amlodipine)
Also can use beta-blockers to slow heart rate.
Can reduce fibrosis by using ACEI
Amlodipine is also used to treat hypertension
Spironolactone is an example of a
Diuretic that works by blocking aldosterone receptors
What is the main problem associated with diuretics?
Kidney is very good at developing a new equilibrium (i.e. absorbing sodium in the distal tubule more)
Furosamide is a LOOP diuretic that blocks sodium reabsorption.
If not altered/ checked kidney can become refractory to diuretics
Function of Pimobendan
Pimbobendan (Vetmedin) is a phosphodiesterase inhibitor and calcium sensitiser
i.e. arterio/veno dilator and positive inotrope to enhance systolic function
Example of a venodilator
Nitroprusside (Nitrates act as endogenous nitric oxide to relax smooth muscle)
or glyceryl trinitrate (acts in same mechanism)
What is the function of Amlodipine?
Enhances diastolic rythem by allowing for ventricular filling. Hastens relaxtion
Is a calcium blocker i.e. calcium antagonist
Three main types of acquired cardiovascular disease in order of frequency
- Degenerative mitral valve disease: SMALL DOGS
- Dilated cardiomyopathy
- Pericardial effusion
A Cavalier King Charles Spaniel presents with a LEFT APICAL SYSTOLIC MURMER. What is the highly suggestive of?
DMVD: Degenerative Mitral Valve Disease
A dog with early disease of DMVD (murmur but no clinical signs) should be treated with…
No evidence that treating early in disease is of any benefit.
Administer medication once dog has gone into heart failure, MINIMUM Furosemide and Pimobendan, (and possibly ACEI and Spironalactolone)
How does Digoxin help in cardiac failure?
Blocks Na/K pump. Increases intracellular calcium (enhances systolic function)
Prognosis once in heart failure
200-300 days (less than a year)
Signalment of Dilated cardiomyopathy
LARGE breed dogs (c.f. DMVD) Dobermans, Boxers, Great Danes, Cocker Spaniels. Increases with age, males predisposed
Is an arrhythmia more likely to be present in a dog with DMVD or Dilated Cardiomyopathy
Arrhythmia is more likely in a dog with dilated cardiomyopathy
What is the difference between giving medication before signs of congestive heart failure in DCM and DMVD?
Not given in DMVD
With DCM, evidence to suggest benefit of ACEI prior to the onset of signs of heart disease
Following cardiac failure give same drugs for both
Furosamide, Pimobendan, ACEI, Spironolactone
St Bernards are predisposed to what type of heart condition?
Pericardial effusion
St Bernards tend to develop the disease earlier.
Also labrador retrievers, german shepherd dogs etc
What causes Pericardial effusion?
Idiopathic (unknown) or cancer or foreign body
Can cause forward failure (inadequate output) or backward failure (congestion- right sided heart failure)
Out of the three canine cardiac diseases, which one causes right sided heart failure instead of left sided heart failure?
Left Sided: DMVD, DCM
Right Sided: Pericardial effusion
Difference in auscultation between DMVD and Pericardial effusion
DMVD: Loud systolic apical murmer
Pericardial effusion: Muffled heart sounds.
Jugular venous distention, NO HEART MURMUR. Underdiagnosed
Enalapril is an example of a
ACE inhibitor.
Significance of Pericardial tampanade
No drugs will help. Need pericardiocentesis.
Right atrium pressure less than effusion pressure
Valve disease is very rare in ___
Cats
Which cardiac disease is thought to be a significant contributor to sudden death in cats?
Hypertrophic cardiomyopathy.
Diastolic dysfunction due to inaqequate filling.
HCM has what cat breed dispositions
ANY AGE. AS young as 6 months
Maine coons, Ragdolls, Persians.
Most cats with HCM are ‘Moggies’
Mutation in myocin binding protein C?
Which conditions does HCM in cats predispose to?
Aortic thromboembolism, Ventricular complexes= sudden death.
Should be given Clopridogel or Asprin to prevent thromboembolism.
Normally have huge atria
What should the diameter of the left ventricular wall thickness be during diastole?
LV wall thickness should be <6mm during DIASTOLE
Abnormal motion of the anterior mitral leaflet during systole (SAM) is characteristic of what…(in cats)
Obstructive HCM
i.e Left Ventricular Outflow Tract Obstruction.
Causes tract obstruction and mitral regurgitation
Restrictive Cardiomyopathy (RCM)
Impaired diastolic filling, Stiff Left ventricle. Normal Older cats, Dyspnoea, Arrhythmias common
Arryhythmogenic right ventricular cardiomyopathy (ARVC) is characterised by
Characterised by fibrofatty infiltration of the right ventricle.
Right heart enlargement , syncopeal
Tricuspid regurgitation normally present
ECG of atrial fibrillation shows..
Radom electrical activity in the atria. No P waves Random depolarisation of AV node. Irregularly irregular R-R NORMAL RATE
A p wave without QRS is indicative of
atrioventricular block
1st degree: prolonged
2nd degree: occasional failure
3rd degree: complete failure: has to be a escape focus
QRS wave without P wave is indicitive of
Atrial fibrillation,
Escape focus can be ventricular, supraventricular in origin
How would the complexes on ECG vary IN APPEARANCE between supraventricular and ventricular complexes?
Supraventricular: largely normal appearance
Ventricular: Wide, bizarre QRS complex without P-waves
A horse presents with AF, what drug that has extensive side effects can you prescribe?
How does this work?
Quinidine sulphate. Prolongs the refractory period.
Unwanted side effects: hypotension, negative inotrope, gastrointestinal ulceration.
Treat with digoxin first
Following oral administration of Quinidine Sulphate the horse develops tachycardia (seen on ECG), what do you do next?
EMERGENCY. Due to vagolytic side effect causing supraventricular tachycardia.
Administer: Digoxin (to slow HR)
Bicarbonate to increase plasma binding and reduce effective concentration
Intravenous fluids to support blood pressure (hypotension due to alpha adrenergic antagonism)
A horse that has had AF for more than ___ should not be treated with quinidine sulphate as its not effective and has unacceptable side effects
> 6months
greater than 3 months has a recurrence rate of 60%
Treatment for atrial premature complexes
APC’s rarely require specific anti-arrhythmic because venttricular rate is not increased.
Corticosteriods??
Which type of ultasound is the best way of measuring the diameter of the ventricles?
M-mode echo produces 2D images which is the best way to measure diameter
A horse owner wants to know if they can ride a horse with AF. What do you advise?
AF is ok but may develop ventricular arrthmias which is associated with sudden death.
Take exercising ECG before signing off as safe
Jugular distention in the horse is associated with ___ sided heart failure
Right sided cardiac failure.
Ventral oedema: Ventral oedema
In horses with a VSD, what murmur do you get
Get TWO murmurs. Pressure gradient goes from Left to Right.
Get systolic murmur as blood hits RIGHT wall.
Another Systolic murmur Pulmonary artery (left third rib). TOO much blood
During what stage of the cardiac cycle would aortic regurgitation be heard
Heard in Diastole.
Think when blood SHOULD be passing through.
A quiet murmur following exercise only heard on the left hand side is likely to be a _____
flow murmur
DDx for Systolic murmur on the RHS
- VSD (check for mumur on left associated with pulmonary artery)
- Tricuspid regurgitation
How does fractional shortening vary in DCM and DMVD?
DCM: Decreased fractional shortening (DD)
DMVD: Increased fractionally shortening
Left atrial size increases with BOTH
In dogs you could expect a flow murmur over…
Outlet valves - left heart base.
In systole.
Low intensity
Where would you hear a murmur caused by a VSD in a dog?
Right side systolic murmur.
2 murmurs in horse
A continuous murmur throughout the cardiac cycle in a dog is indicitive of a
PDA
What is the quickest way to determine if mitral regurgitation is significant?
- resting tachycardia?
- Signs of left sided heart failure? Ventral oedema etc
- Arrthmias? Atrial fibrillation
You have heard a continuos murmur in a 8 day old foal. What action do you take?
Continuous murmur= patent ductus arteriosus.
Normally patent in foals up to 10 days old.
Consider abnormal if still present >1 month
Closes earlier in farm animals.
‘Washing machine murmur’
How do you radiograph a horses heart
Can’t because plates are not large enough and too high exposure factors would be involved
Dogs with mitral valve disease frequently present with a cough. What causes this?
Cough doesn’t necessarily mean heart failure (pul oedema)
Probably due to compression of left main bronchus by enlarged left atrium.
Treatment involves bronchodilation and cough supressents (Butorphanol/Codeine)
Cardiac tamponade is normally haemorrgaic in the dog. What causes the associated clinical signs?
Right-sided congestive failure.
Normally ideopathic or secondary to neoplasm(check AGE)
Clinical signs associated with a) LEFT SIDED HEART FAILURE
b) RIGHT SIDED HEART FAILURE
a) LEFT= LUNGS
b) RIGHT= Ascities, jugular distention, tachypnoea, hepatomegaly (consequence of cardiac tamponade)
Which drugs are contraindicated in the treatment of Pericardial effusion in the dog
Pericardial effusion leading to cardiac tamponade is most common in male golden retrievers and st bernards.
ACE inhibitors are contraindicated (may lead to collapse).
Muffled heart sounds
Why are puppies predisposed to flow murmurs?
Less viscous blood (lower PCV, lower plasma protein concentration) therefore predisposed to turbulance. Innocent flow murmur.
Also tend to have slightly higher cardiac output
Which type of congenital ‘abnormality’ is normal in foals <10days old?
Patent ductus arteriosus- diastolic component should disappear within a few days
Left heart base murmurs of the dog are likely to be
stenosis of an outflow valve.
Aortic stenosis associated with dampered pulses (c.f. PDA = dynamic pulses).
Intense right sided murmur is likely to be
ventricular septal defect. Pressure difference from LEFT to RIGHT (hits RIGHT WALL)
Why would you check the PCV of an animal with a murmur?
If persistant hypoxia due to shunting of blood (right to left) will cause a polycythaemia (increased PCV)
Why is right to left shunting not enough to cause cyanotic heart disease? What other pathology needs to be present?
Right to left (pulmonary to systemic shunt) e.g. VSD, ASD will lead to deoxygenated blood going around systemic circulation.
ALSO NEED INCREASED RIGHT HEART PRESSURE/PULMONARY CIRCULATION.
e.g. Pulmonary stenosis (tetology of fallot), pulmonary hypertension.
Clinical signs of right to left shunt
combined with increased pulmonary pressure
- stunted growth
- visible cyanosis
- severe exervise intolerance
- polycythaemia (persistant hypoxia) leads to increased viscosity
How does the size of heart affect the frequency of transducer required?
Larger heart - low frequency transducer
Where would you locate the heart of a snake? `
1/3 of the way down its body
Which anaesthetic giving set does not have a circuit factor?
CIRCLE does not have a circuit factor.
Air only flows in one direction
Can only be used >10kg due to the one way valves increasing resistance.
Can be used for IPPV (ABC of IPPV)
