High arterial pressures are associated with high levels of after load and cardiac work. This may predispose to myocardial ischemia and infarction, especially in the presence of coronary artery disease and left ventricular hypertrophy, and therefore simply ignoring markedly elevated arterial pressure may not be appropriate. Patients diagnosed as ‘hypertensive’ have a reputation for displaying increased cardiovascular lability during anesthesia. There is certainly a pathophysiological basis for such behaviour. Established hypertension is associated with an increased systemic vascular resistance. The systemic vasodilatation associated with anesthesia might well be expected to have profound effects on arterial pressure in such patients. For many anesthetists, however, cardiovascular lability implies something more than the decrease in arterial pressure seen at induction of anesthesia. It suggests swings in arterial pressure over a wide range of values. Interestingly, patients with preoperative hypertension appear more likely to develop intraoperative hypotension than non-hypertensive persons; this is particularly true for patients taking ACE inhibitors or angiotensin II receptor antagonists. In some patients, this may be related to a decrease in vascular volume.

      With regard to the management of surgical patients with elevated admission arterial pressure, there are few substantive guidelines over which patients should be cancelled to allow treatment before surgery or the duration of such treatment before proceeding with surgery. Several investigators have demonstrated exaggerated intraoperative blood pressure fluctuation with associated ECG evidence of myocardial ischemia in patients with preoperative blood pressure elevation. This effect can be modified by treatment. Because intraoperative ischemia correlates with postoperative cardiac morbidity, it follows that control of blood pressure preoperatively may help reduce the tendency to perioperative ischemia. Although an elevated blood pressure on an initial recording in a patient with previously undiagnosed or untreated hypertension has been shown to correlate with blood pressure lability under anesthesia, the definition of the severity of hypertension rests with subsequent recordings in a non-stressful environment. In patients undergoing therapy for hypertension, a thorough review of current medications and dosages, along with awareness of known intolerance to previously prescribed drugs, is essential. The physical examination should include a search for target- organ damage and evidence of associated cardiovascular pathology. A fundoscopic examination may provide useful data regarding the severity and chronicity of hypertension.

     If the initial evaluation establishes hypertension as mild or moderate, and there are no associated metabolic or cardiovascular abnormalities, there is no evidence that it is beneficial to delay surgery.18 Several investigators have established the value of effective preoperative blood pressure control among patients with established hypertension,8,10 and antihypertensive medications should be continued during the perioperative period. Particular care should be taken to avoid withdrawal of β-blockers and clonidine because of potential heart rate or blood pressure rebound. In patients unable to take oral medications, parenteral β-blockers and transdermal clonidine may be used. Medication selection and risks should be assessed on the basis of national guidelines.

     For stage 3 hypertension, according to JNC VI classification, (systolic blood pressure greater than or equal to 180 mm Hg and diastolic blood pressure greater than or equal to 110 mm Hg), the potential benefits of delaying surgery to optimize the effects of antihypertensive medications should be weighed against the risk of delaying the surgical procedure. The evidence from medical studies suggests that patients with stage 3 hypertension are at significantly increased risk of target organ damage, whether or not this is clinically evident. There is certainly evidence to support a steadily increasing incidence of postoperative myocardial ischemia with increasing admission systolic arterial pressure.

     However, there is evidence that very rapid control of arterial pressure with drugs such as sublingual nifedipine is associated with increased morbidity and mortality. Taken together, these concerns pose the dilemma that markedly raised arterial pressures and wide excursions of arterial pressure should be avoided in the perioperative period, but that dramatic acute reductions in arterial pressure may also be fraught with risk. Many patients with admission arterial pressures consistent with stage 3 hypertension will have isolated systolic hypertension. With rapidly acting intravenous agents, blood pressure can usually be controlled within a matter of several hours. If severe end-organ damage is present, the goal should be to normalize BP as much as possible before surgery.

     Effective lowering of risk may require 6 to 8 weeks of therapy to allow regression of vascular and endothelial changes, but too rapid or extreme lowering of BP may increase cerebral and coronary ischemia; therefore, the benefits of delaying surgery for treatment must be weighed against the risks. Thus, if surgery cannot be postponed, the goal is to not decrease chronically increased BP too rapidly. Severely elevated BP should be lowered over a period of several weeks. Studies suggest that hypotension intraoperatively is far more dangerous than hypertension.

     If the patient is considered fit for surgery in other respects, their operation should not be deferred simply on account of an elevated admission arterial pressure. If the arterial pressure is consistently elevated to levels of 180 mm Hg systolic or greater or 110 mm Hg diastolic or greater, surgery may proceed, but care should be taken to ensure perioperative cardiovascular stability. Invasive arterial pressure monitoring is indicated for major procedures, and the arterial pressure should be actively managed to prevent excursions of the mean arterial pressure of greater than 20% from baseline. Monitoring should continue into the postoperative period until it is clear that the patient is cardiovascularly stable. It may be appropriate to manage the patient in a high dependency area in the immediate postoperative period.

     Several reports have shown that the introduction of preoperative β-adrenergic blockers leads to effective

modulation of severe blood pressure fluctuations and a reduction in the number and duration of perioperative

coronary ischemic episodes. The preoperative administration of b-adrenergic blocking drugs has been shown to decrease the incidence of postoperative atrial fibrillation, and in patients who have or are at risk for CAD who must undergo noncardiac surgery, treatment with beta blockers during hospitalization can reduce mortality and the incidence of cardiovascular complications. However, the Preoperative Ischemia Evaluation (POISE) trial has recently questioned the safety of starting these agents acutely. The optimal time to start b-blocker therapy to achieve its benefit while minimizing risk is unknown. Even though diuretics are first-line therapies in most circumstances, starting them in the preoperative period is not generally a good idea because of the alterations in potassium (both hypokalemia and hyperkalemia) that may occur and the need for close monitoring and replacement. Calcium channel blockers (e.g., amlodipine, 5 to 10 mg daily) can be very effective. Frequently, anxiety increases BP, and therefore antianxiolytics can be used as adjunctive therapy. BP should not be lowered too rapidly. Continuation of antihypertensive treatment preoperatively is critical.

Preoperative Administration of Antihypertensives

     Most authors administer all antihypertensive drugs preoperatively, except ACE inhibitors or angiotensin II receptor blockers (ARBs), which needs to be tailored to the individual patient. It was demonstrated that more severe hypotensive episodes requiring vasoconstrictor treatment occur after induction of general anesthesia in patients chronically treated with an ARB and receiving the drug on the morning before surgery than in those in whom ARBs were discontinued on the day before surgery.25 If chronic ACE inhibitors/angiotensin receptor blockers are continued, vasopressin is the drug of choice for refractory hypotension. Most anesthesiologists even administer the patient’s chronic diuretics on the morning of surgery because the major effect of diuretics after 1 week of therapy is arteriolar vasodilation and assessment of urine output may be inaccurate if the diuretic is abruptly discontinued on the morning of surgery.

    Intraoperative and postoperative treatment of hypertension can be achieved with multiple agents. Since several days may lapse before oral intake is resumed, parenteral treatment with diuretics, adrenergic inhibitors, vasodilators, angiotensin-converting enzyme inhibitors, or use of transdermal clonidine have all been proposed in the JNC-VII. It is critical to initiate some form of therapy to prevent rebound hypertension and tachycardia observed from withdrawal of these agents. Consideration should be given to restarting ACEI in the postoperative period only after the patient is euvolemic, to decrease the risk of perioperative renal dysfunction.