Diseases and Surgical Procedures

Hypertension

Hypertension defined as: series of blood pressure measurements reveal pressures greater than 160/100
Normal increases with age as the arteries become stiffer

Causes

Preoperative
Primary or essential hypertension (90%)
  • No known cause
Secondary (10%)
  • Renal: chronic pyelonephritis/renal artery stenosis/ polycystic kidneys
  • Endocrine: Pheochromocytoma/Cushing’s disease/Conn’s disease
  • Pregnancy
  • Coarctation of the aorta
Perioperative

Pain
Light anesthesia
Hypoxia
Hypercarbia
Fluid overload
Drug interactions/ vasopressors given
Surgical effects
Malignant hyperthermia
Measurement error

Postoperative

Inadequate post-operative analgesia
Anxiety
Hypothermia
Raised intracranial pressure
Rebound hypertension after aortic valve replacement or coarctation repair
Anesthetic assessment
Etiology investigated
Cancel elective surgery if diastolic more than 110 mmHg

Preoperative considerations

CBC/Electrolytes (Chem7/BMP) (renal impairment)
Blood sugar (diabetes)
ECG (LVH or ischemia)
CXR (enlarged heart or distended upper lobe veins)
Look for signs of end-organ damage

Continue medication
Local blocks e.g. brachial plexus blocks or ankle blocks

Monitoring and induction

Monitoring depends upon the degree of hypertension
Arterial line and CVP may be used

Measures to attenuate the pressor response to laryngoscopy and intubation

Beta-blockers
Short acting opioids
Lidocaine to larynx or IV 1mg/kg
Induction and maintenance using agents with CVS stability
Ketamine and pancuronium are contraindicated

Maintenance

Balance between light anesthesia with hypertension and deep anesthesia with hypotension
Avoid hypertension and tachycardia
High concentrations of volatile agents can cause hypotension by decreasing the systemic vascular resistance and by depressing the myocardium.
Nitrous oxide can be safely used.
Local anesthetic nerve blocks or infiltration are useful either on their own or to supplement general anesthesia.
Adequate fluids - hypotension poorly tolerated

Post-operatively

Good analgesia
Adequate warming- shivering and tachycardia dangerous
Restart regular antihypertensive medication

Drugs used in an emergency

Labetalol
Propranolol
Hydralazine
Nifedipine
Diazoxide