Chapter 22 Anaesthesia Practice for Existing Conditions Flashcards
What is anaesthsia related death rate in small animals?
1 in 500-1000
List criteria for ASA (American Society for Anaesthesiologists) classifications 1-5
What is the goal of anaethesia (3 things)
Analgesia
Anaesthesia
Muscle relaxation
What is meant by MAC reduction
Concept whereby addition fo anaesthetic/analgesic drugs change the required dose of inhalant anaesthetic
List describe the mechanism of action of a calcium channel blocker and list 3 examples
MoA: Block calcium channels in vascualr smooth muscle, cardiac myocytes or pacemeker cells –> relaxation of vessel/myocyte/slowing of AP. Therefore all -ve inotropes and -ve chronotropes
Amlodipine - acts of vascular calcium channels only
Verapamil - acts on cardiac myocytes and pacemaker cells only
Dilatiazem - in between the abve two, some action at all sites
Varying degree of effect depending on site/drug
How many beta receptiors are there? Where are the main sites for each type?
Beta - 1: Heart. Adrenergic simulation –> +ve inotropy and chronotropy. Also juxtaglomerular apparatus of kidney - if stimulated (by drop in BP) –> activation of RAAS
Beta - 2: Brochioles, arteries, detrusor m of bladder. Adrenergic stimulation –> relaxation.
Beta-3: Adipocytes
Eg atenolol, propaolol
List 3 positive inotropes
Dobutamine (a beta-agonist), pimobendan, digoxin e.g. DCM may require dobutamine
List some specific considerations when anaestehtising patient with cardiac disease:
- Echo
- Pre-oxygenate
- Oesophageal stethoscope to allow detection of crackels
- CVP monitoring
- Continue most cardiac drugs as uusal but ACE-inhibitor can be skipped on morning of sx.
- Alpha-2 agonists contraindicated as compromise CO/myocardial oxygen delivery
- Etomidate induction (CV sparing - N.B. Supressed cortisol production…relevant in other conditions), or co-induction (benzo = propofol/alfax)
- Nerveblocks to minimise inhalant
- No lidocaine if 2nd or 3rd degree AV block
- Awareness re Branhams reflex (PDA)
List indications for treatment of ventricular ectopy
- HR >150 bpm
- Multiform ventricular beats
- Hypotension during periods of abnormal beats
- R-on-T phenomenon (QRS follows straight after T, without retrun to baseline)
List some specific considerations when anaestehtising patient with thyroid disease
- Hypertension
- Underlying renal insufficiency
- Thyrotoxic cardiomyopathy
- “Thyroid storm”
- Thyroid neoplasia part of multiple endocrine neoplasia syndrome?
- Post-op laryngeal paralysis
- Post-op hypocalcaemia (wiht removal of parathyroid glands)
- In dogs - full staging before surgery in case of multiple endocrine neoplasia syndrome
- No ketamine - due to cardiomyopathy and risk of thyroid storm
List some specific considerations when anaestehtising patient with DM
- Higher infection risk
- Minimize insulin changes 1/2 dose morning of sx
- Hourly glucose monitoring
List some specific considerations when anaestehtising patient with insulinoma.
Which cells affected in insulinoma
Insulinoma = tumour of pancreatic beta-cells
- Pre-op stabilization with lots of small meals and glucocorticoids (induce insulin resistance)
- BG q30m
Adrenal cortex divided into 3 zones - what are they and what do they produce? What does adrenal medulla produce?
Cortex:
- Zona glomerulosa:* Mineralocorticoids
- Zona fasciculata:* Glucocorticoids
- Zona reticularis:* Androgens
Medulla (Chromaffin cells): Cathecholamines
In cases of phaeo, what is pre-treatment recommendation?
What drugs would be used to treat the following intra-op effects?
- Tachycardia
- Hypertension
- Arrythmia
Phenoxybenzamine 0.5 mg/kg po bid for 2-3 weeks before
- Tachycardia: Beta blocker (esmolol) or calcium channel blocker (diltiazem)
- Hypertension: Nitroprusside
- Arrythmia: Lidocaine
Give corticosteroids post-op if functional tumour
List some specific considerations when anaestehtising patient with respiratory disease
- Pre-op stabilisation eg thoracocentesis
- Consider ketamine premed - brochodilator and maintains respiratory centre sensitivity to PaCO2)
- Pre-oxygenation
- Prepartion for difficult intubation
- Katmine/benzo induction does not produce apnea. Propofol in brachys as fast
- Avoid pre-med if assessing laryngeal function
- Larger volume pepidural infustae to reach thoracic region, do not use local as risk of paralysis to muscles of respiration
- Repidly exhaled inhalant agent i.e. desflourane
- Pressure-limited ventilation of fibrosing pleuritis (<10 cm H2O)
- Care re re-expansion oedema