Chapter 25
Hypertension

Essential hypertension (chronic hypertension) typically arises from chronic dysregulation of the renin-angiotensin-aldosterone system, age-related vascular changes, or ventricular remodeling. This section of the chapter focuses on intraoperative hypertension, which is more often the result of acute sympathetic nervous system activation. Patients with chronic hypertension will exhibit greater levels of intraoperative hypertension due to altered vascular autoregulation and increased baseline sympathetic tone. Additionally, they may have LVH, which allows them to mount higher systemic pressures under stress.

Why It Matters

Sustained intraoperative hypertension increases the risk of stroke and cardiovascular events. Bleeding risk is only increased at extremes of blood pressure, since most bleeding is due to venous oozing. During microvascular, ENT, or neurosurgical procedures involving small, delicate structures, even modestly elevated blood pressure can significantly impact surgical visualization and thus should be avoided.

Common Causes of Intraoperative Hypertension

The most common cause is surgical stimulation. With time, you’ll become familiar with the “hot zones” of stimulation. Try to anticipate these rather than react to them post-hoc:

Peritoneal insufflation and stretching
Bone manipulation (e.g., orthopedic or spinal instrumentation)
Oral surgery and any ENT procedure involving the face
Open thoracotomy or laparotomy, during the exposure phase
Ventriculoperitoneal (VP) shunt tunneling
Tourniquet pain

Illustration of a trophy. Pro-tip: Tourniquet pain is unique: it causes a very gradual rise in BP and HR, which is difficult to mitigate with anesthetic agents. Be cautious when treating this pain. Err on the side of using short-acting agents and not piling on opiates. This is because post-tourniquet deflation usually results in brief, significant hypotension. This is due to systemic vasodilation and release of lactic acid from the ischemic limb. Once the tourniquet is down, this profound sympathetic stimulation will cease.