Etiologies

Etiologies:

1. Catecholamine excess may be seen with inadequate anesthesia, especially with increased sympathetic stimulation during laryngoscopy, intubation, incision, emergence, patient anxiety, and pain or with hypoxia, hypercarbia, and prolonged tourniquet use.
2. Preexisting disease such as essential hypertension, secondary causes of hypertension such as pheochromocytoma, sleep apnea, or other endocrine, renal, or renovascular disorders.
3. Increased intracranial pressure (ICP). When ICP rises, blood pressure increases to maintain cerebral perfusion pressure.
4. Systemic absorption of vasoconstrictors (eg, injection of local anesthetic with epinephrine).
5. Aortic cross-clamping, which leads to a significant increase in SVR.
6. Rebound hypertension from discontinuation of clonidine or β-adrenergic blockers.
7. Drug interactions. The administration of ephedrine to patients receiving tricyclic antidepressants (eg, amitriptyline, nortriptyline, doxepin) and monoamine oxidase inhibitors (eg, isoniazid, rasagiline, selegiline) may cause an exaggerated hypertensive response.
8. Bladder distension. Sympathetic response with bladder distension leads to increased blood pressure.
9. Administration of indigo carmine dye (via an α-adrenergic effect).

The treatment of hypertension is directed toward correcting the underlying cause. It may include the following:

1. Optimizing oxygenation and ventilation.
2. Increasing the depth of anesthesia (eg, volatile and IV anesthetics and analgesics).
3. Sedating an anxious patient or emptying a full bladder.
4. Medications (for further discussion, see Chapter 18).
   1. Combined α- and β-adrenergic blocking agents: labetalol 5- to 10-mg increments IV.
   2. β-Adrenergic blocking agents: propranolol 0.5- to 1.0-mg increments IV; metoprolol 1.0 to 5.0 mg IV; or esmolol, 5- to 10-mg increments IV.
   3. Vasodilators: hydralazine 2.5- to 5-mg increments IV; nitroglycerin infusion, 30 to 50 μg/min IV and titrating to effect; nitroprusside infusion 30 to 50 μg/min IV and titrating to effect.
   4. Calcium channel blockers: verapamil 2.5 to 5 mg IV; diltiazem 5 to 10 mg IV.