Baseline Blood Pressure and Implications for Anesthesia

Abnormalities in a patient’s baseline blood pressure, particularly in cases of high blood pressure, can have profound implications for anesthesia and surgery. Hypertension, or high blood pressure, affects a significant proportion of patients undergoing surgery. Its presence can complicate perioperative management and increase the risk of adverse cardiovascular events (1).

General anesthesia typically involves a combination of agents, each with distinct cardiovascular effects. Volatile anesthetics like sevoflurane and isoflurane can cause vasodilation and myocardial depression, leading to reduced systemic vascular resistance and potentially significant decreases in blood pressure. The hypotensive effect of certain anesthesia medications, while manageable in patients with normal baseline blood pressure, can be pronounced in hypertensive patients, whose vascular systems may exhibit altered responsiveness due to chronic hypertension-induced vascular changes (2).

Many intravenous agents, such as propofol, also induce vasodilation but differ in their mechanism, primarily acting on the endothelium and smooth muscle cells to facilitate systemic vasodilation. The rapid onset and significant vasodilatory effects of propofol necessitate careful titration and monitoring in hypertensive patients to avoid precipitous drops in blood pressure (1).

Regional anesthesia, including spinal and epidural techniques, offers an alternative that can minimize the systemic cardiovascular effects seen with general anesthesia for patients with abnormal baseline blood pressure. However, these techniques are not without their challenges in hypertensive patients. Spinal anesthesia, for example, can lead to sympathetic blockade, resulting in vasodilation below the level of the block and potential hypotension. This risk is particularly acute in patients with poorly controlled hypertension, who may have a blunted compensatory response to the decrease in systemic vascular resistance (3). Epidural anesthesia provides a more gradual onset and can be titrated more precisely than spinal anesthesia, potentially offering better control over hemodynamic changes. Yet, the risk of hypotension persists, especially with higher doses or extensive blocks, necessitating vigilant monitoring and the readiness to intervene with fluids or vasopressors as needed.

Local anesthesia, often perceived as the least impactful on systemic blood pressure, can be complicated by the addition of vasoconstrictors like epinephrine. These agents are commonly added to local anesthetics to prolong their duration and reduce bleeding. However, in patients with high baseline blood pressure, the systemic absorption of epinephrine alongside anesthesia can lead to transient but significant increases in heart rate and blood pressure, posing a risk of exacerbating preexisting hypertension or precipitating adverse cardiovascular events (4).

Managing blood pressure intraoperatively in hypertensive patients requires a delicate balance. Anesthesiologists can employ short-acting antihypertensive medications like esmolol, a beta-blocker with a rapid onset and short duration, allowing for fine-tuned control of blood pressure. Vasodilators such as nitroglycerin and sodium nitroprusside can also be used for their rapid action in lowering blood pressure, but their use must be carefully monitored to avoid excessive hypotension (2). Postoperative blood pressure management is critical, as patients may experience hypertensive surges due to pain, stress, or rebound effects from intraoperative blood pressure management. A strategy involving the careful titration of antihypertensive medications, effective pain management, and close monitoring is essential to navigate this period safely (4).

The perioperative management of hypertension demands a comprehensive understanding of the physiological impacts of anesthesia and responses of patients with an altered baseline, and a strategic approach to blood pressure control. Tailoring anesthetic techniques and medications to the individual patient’s needs, while remaining vigilant for the dynamic changes occurring during the perioperative period, is paramount in optimizing outcomes for hypertensive patients undergoing surgery.

References

1. Apfelbaum JL, Connis RT, Nickinovich DG, et al. Practice advisory for preanesthesia evaluation: an updated report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Anesthesiology. 2012;116(3):522-538.
2. Varon J, Marik PE. Perioperative hypertension management. Vasc Health Risk Manag. 2008;4(3):615-627.
3. Leslie K, Myles P, Devereaux P, et al. Neuraxial block, death and serious cardiovascular morbidity in the POISE trial. Br J Anaesth. 2013;111(3):382-390. doi:10.1093/bja/aet120
4. Howell SJ, Sear JW, Foëx P. Hypertension, hypertensive heart disease and perioperative cardiac risk. Br J Anaesth. 2004;92(4):570-583. doi:10.1093/bja/aeh091