Anesthetic Management of Hypertensive Patients

Anesthetic Management of Hypertensive Patients

Elective surgery should not be performed on patients with hypertension unless optimally treated. Patient hypertension should be managed in central hospitals which have many senior anesthetist and other resources to optimize patient condition preoperatively, manage anesthesia and provide critical care postoperatively.

When surgery cannot be delayed, however, you should weight the merits and de merits of the surgery and drugs and techniques chosen to provide anesthesia. Regional anesthetic is an excellent choice in patients with multiple medical conditions scheduled for peripheral surgery.

Preoperative Evaluation

Preoperative evaluation of patients with essential hypertension begins with a determination of the adequacy of systemic blood pressure control and a review of the pharmacology of the antihypertensive drugs being used for therapy (Table1.3). Antihypertensive drugs should be continued throughout the perioperative period. Evidence of major organ dysfunction (congestive heart failure, coronary artery disease, cerebral ischemia, renal dysfunction) must be sought and whenever there is inadequate control or manifestation of major organ dysfunction is suspected and if operation is elective and/or can be delayed consultation of physician is mandatory.

Patients with cardiac disease who are scheduled for elective surgery can have episodes of myocardial ischemia in the days prior to surgery. The night before surgery is stressful and prophylactic β-blockade or clonidine can reduce the risk of sympathetic stimulation resulting in tachycardia and subsequent myocardial ischemia.

Despite therapy, systemic blood pressure increases during the intraoperative period are more likely to occur in patients with a history of essential hypertension regardless of the degree of pharmacologic control of systemic blood pressure established preoperatively.

Antihypertensive drugs and anesthesia: Elective surgical cases are usually given their regular antihypertensive medications on the morning of surgery. Remember that anaesthetic agents also cause vasodilation and cardiac depression, and the effects may be cumulative. Analgesic agents will reduce anaesthetic requirement and allow a smoother induction. Beta blockers are avoided in patients with asthma. Excessive bradycardia from beta blockers may also cause adverse events and require treatment with anticholinergics (atropine or glycopyrrolate). Angiotensin converting enzyme inhibitors (e.g. captopril) cessation should be considered if marked blood loss is anticipated or spinal anesthetic are used.

Induction of Anesthesia

Induction of anesthesia with intravenous drugs is acceptable, remembering that an exaggerated decrease in systemic blood pressure may occur, particularly if hypertension is present preoperatively. Sodium thiopental, propofol, midazolam, opioids (fentanyl), and etomidate all have been used to induce anesthesia. Etomidate or combinations of midazolam and fentanyl are frequently used because of their limited hemodynamic effects. Ketamine is not selected for induction of anesthesia in patients with essential hypertension because it can increase systemic blood pressure and cause tachycardia, which may lead to myocardial ischemia.

Hypertension can occur during direct laryngoscopy for tracheal intubation in patients with essential hypertension but may be attenuated with administration of opioids and β-adrenergic blockers (Table1:4). Tachycardia may lead to episodes of myocardial ischemia. A single 1-minute episode of myocardial ischemia increases the risk of perioperative cardiac morbidity tenfold and death twofold. Maximal attenuation of sympathetic nervous system responses should be attempted during direct laryngoscopy by administering anesthetics, intravenous opioids (fentanyl 1-2 μg/kg), and β-blockers before attempting tracheal intubation. Careful attention to the airway is critical in all anesthetics, and the risks are even more intense in patients with cardiac disease.

Hypoxia, tachycardia, hypotension, hypertension, and myocardial ischemia must be avoided. Yet, an excessive concentration or dose of anesthetic drugs can produce hypotension, which is as undesirable as hypertension. An important concept for limiting pressor responses elicited by tracheal intubation is to limit the duration of direct laryngoscopy to less than 15 seconds if possible. In addition, the administration of laryngotracheal lidocaine immediately before placement of the tube in the trachea will minimize any additional pressor response.

Maintenance of Anesthesia

The goal during maintenance of anesthesia is to adjust the concentrations of anesthetics so tachycardia and wide fluctuations in systemic blood pressure can be avoided. Changes in the concentration of volatile anesthetics with opioid allow rapid adjustments in the depth of anesthesia in response to increases or decreases in arterial blood pressure.

Changes in surgical stimulation may lead to changes in blood pressure and heart rate. Additional doses of narcotics, β-blockers, and changes in the dose of volatile anesthetic can be used to control hemodynamics. Heart rate control is the most critical element for preventing cardiac morbidity and death. Heart rates above 120 beats/min increase mortality rate. Volatile anesthetics are useful for attenuating activity of the sympathetic nervous system, which is responsible for these pressor responses.

If hypotension occurs during maintenance of anesthesia it is often treated by decreasing the concentrations of volatile anesthetic while infusing fluids intravenously to increase intravascular fluid volume. Sympathomimetics, such as ephedrine (5-10mg), or vasoconstrictors such as phenylephrine (25-50μg ) may be necessary to restore perfusion pressures until the underlying cause of the hypotension can be corrected. Patients taking sympatholytic preoperatively may exhibit a decreased response to vasopressors, particularly ephedrine; in rare instances small doses of epinephrine, 2-5 mcg, may be necessary. Improper dosing of epinephrine in a hypertensive patient can cause significant cardiovascular morbidity.

The choice of intraoperative monitors for patients with coexisting essential hypertension include B/P, ECG, pulse oximeter, body temperature, urine catheter and other available monitors.

Postoperative Management

Hypertension in the early postoperative period is a frequent occurrence in patients with a preoperative diagnosis of essential hypertension. Prophylactic or therapeutic administration of β-blockers or clonidine can reduce these episodes of hypertension and reduce risk of perioperative ischemia and death. If hypertension persists despite β -blockers and adequate analgesia, intermittent injections of hydralazine (5 to 20 mg IV) or labetalol (0.1 to 0.5 mg/ kg IV) should be considered. Tachycardia in the postoperative period must be actively avoided as it increases morbidity and mortality rates. A heart rate of 120 beats/min raises the risk of postoperative death. Clearly the arterial blood pressure needs to be controlled during the entire perioperative period.