Essential Hypertension (Cardiac Anesthesia)


Essential hypertension is defined as 160/90 with no other obvious cause. Note that these patients are at increased risk for CAD as well as PVD. Importantly, a large percentage of patients with significant PVD will have 50% stenosis in at least one coronary artery – a study of 1000 patients who underwent elective peripheral vascular reconstruction (all of whom received a coronary angiogram) showed single, double, and triple vessel disease (defined as stenosis > 50%) in 23%, 20%, and 18% of patients [Hertzer NR et al. Ann Surg 199: 223, 1984]

Organ Effects

CNS Effects

The cerebral blood flow autoregulatory curve is also altered (right shift). Whether or not this is clinically significant is debatable – a multicenter regional database containing data on 19,224 patients undergoing coronary revascularization found the incidence of hypertension to be 75.56% in patients who had an intraoperative stroke, versus 68.52% in those who didn’t – this was statistically significant on univariate analysis, however was not significant on multivariate analysis, probably because patients with HTN have other comorbidities (such as peripheral vascular disease, a smoking history, or diabetes) which were significant on both univariate and multivariate analysis. Thus, it appears that a history of isolated hypertension (without comorbidities) is not important from a stroke risk standpoint, but is important in that it can alert the physician to conditions that do increase the risk of stroke – calcified aorta (OR 3.013), renal failure (OR 2.03), previous stroke (OR 1.909), smoking history (1.62), carotid vascular disease (OR 1.59), older age (OR 1.522), PVD (OR 1.50), diabetes (OR 1.37), and the use of cardiopulmonary bypass (OR 1.27) [John R et al. Ann Thorac Surg 69: 30, 2000]

Renal Effects

Renal dysfunction may be present and if so, should be taken into account when making medication decisions. As noted by John et al., renal failure is associated with an increased risk (OR 2.03) of stroke during coronary revascularization [John R et al. Ann Thorac Surg 69: 30, 2000]

Approach to Anesthesia

Perioperative Beta Blockade

Classically, it has been taught that patients at risk for MACE should be given perioperative beta blocker therapy, and that those who present on the day of surgery should be postponed until BP could be adequately controlled. Recently, these beliefs have been challenged. The POISE trial (which excluded patients already on beta-blockers) showed an increase in mortality following prophylactic perioperative beta-blocker administration [Devereaux et al. Lancet 31: 371, 2008]. Weksler et al. showed that cancellation and admission of patients with DBP between 110 and 130 mmHg does not lead to any differences in postoperative complications but significantly increases the average hospitalization time [Weksler et al. Journal of Clinical Anesthesia 15: 179, 2003]. For more information on beta blockade, see Cardiac Risk (Anesthesia Text)

Induction, Maintenance, and Post-Operative Care

Consider a modified cardiac induction (ex. higher doses of fentanyl and midazolam), as systemic blood pressure may drop more than usual. Etomidate should be considered. Hemodynamics can be volatile, thus attempt to minimize the time spent during direct laryngoscopy. Note that a 1 minute period of myocardial ischemia will increase the risk of cardiac morbidity by 10-fold and the risk of death by 2-fold [Stoelting RK. Basics of Anesthesia, 5th ed. Elsevier (China) p. 380, 2006]. Despite these recommendations, no maintenance technique has ever been shown superior in this patient population. The ability to rapidly titrate sevoflurane makes it an ideal treatment for sudden onset of hypertension. Heart rate should be vigorously controlled in these patients, although routine perioperative beta blockade may not be indicated. Postoperatively, many of these patients will display hemodynamic swings. Adequate pain control and short-acting beta blockers, if necessary, should be given first. Consider hydralazine as well as enalaprilat if beta-blockade is inadequate, and as a last resort, nitrates (ex. nitroprusside drip).

Summary: Essential Hypertension in Anesthesia

  • High incidence of PVD (and thus CAD)
  • Altered cerebral blood flow autoregulation
  • Heart rate control
  • Renal function may be compromised