Perioperative management of hypertension
Hypertension affects an estimated 50 million persons in the USA, including 25% of adults and more than 50% of individuals over age 65 years. Thus, many surgeons, anesthesiologists, primary care physicians, and consultants will care for surgical patients with hypertension. Hypertension can increase surgical risk, and it often causes end-organ damage of the brain, heart, and kidneys, with important implications for surgical risk and perioperative management. The essentials of diagnosis, evaluation, and treatment of hypertension have been detailed in recent reviews. This chapter concentrates on the preoperative risk assessment of hypertensive patients and on the perioperative management of hypertension.
Hemodynamic response to anesthesia
A discussion of perioperative hypertension requires a basic understanding of the physiologic responses to anesthesia in normotensive and hypertensive patients. There are four main periods during anesthesia: the induction, intubation, maintenance, and recovery periods. During induction, most patients have a fall in blood pressure. During laryngoscopy and intubation, the sympathetic nervous system is activated and blood pressure and heart rate rise. With deepening anesthesia, a decline in mean arterial pressure and heart rate occur due to the effects of pharmacologic agents, a decrease in sympathetic nervous system activity, and loss of the baroreceptor reflex. During recovery from anesthesia around the time of extubation, blood pressure and heart rate slowly increase in the first 15 minutes, and are accompanied by general arousal.
Patients with untreated hypertension can have exaggerated responses during all of these phases.