Anesthesia for Surgical Specialties and Coexisting Disease
Specialty items pair a procedure with the coexisting disease that changes anaesthetic conduct. Learn the pathophysiology-to-management link for each system rather than lists.
Neuro and cardiac
- Cerebral perfusion pressure = MAP − ICP; maintain MAP, avoid hypoxia and hypercapnia; short-term hyperventilation to PaCO₂ 30–35 mmHg only for impending herniation.
- Severe aortic stenosis: fixed stroke volume - avoid tachycardia, keep sinus rhythm, preload and afterload; hypotension is poorly tolerated.
- Pulmonary hypertension: avoid hypoxia, hypercapnia, acidosis and nitrous oxide.
Thoracic and abdominal
- One-lung ventilation: tidal volume 5–6 mL/kg predicted body weight, PEEP to the dependent lung, CPAP to the non-dependent lung for hypoxaemia.
- Laparoscopy: CO₂ absorption, raised intra-abdominal pressure, vagally mediated bradycardia; avoid nitrous oxide in bowel obstruction and pneumothorax.
- Renal failure: avoid succinylcholine if potassium exceeds 5.5 mmol/L; morphine accumulates (M6G); atracurium is organ-independent.
Obstetric, paediatric, geriatric
- Aortocaval compression from 20 weeks: left uterine displacement.
- Children: higher MAC, rapid desaturation, vagally mediated bradycardia on induction; dose by weight.
- Elderly: lower MAC and clearance, greater sensitivity to benzodiazepines and opioids; optimise anaemia and polypharmacy.
Worked example
A 60-year-old with severe aortic stenosis for hip fracture. A rapid spinal causes sympathectomy that a fixed stroke volume cannot compensate for. Plan invasive arterial monitoring, an incremental spinal or general anaesthetic, phenylephrine support, and maintenance of systolic pressure within 10% of baseline.
Traps
Using nitrous oxide with a pneumothorax or obstruction; giving succinylcholine in burns after 24–48 hours or in spinal cord injury; applying adult tidal volumes to children.