Phentolamine

INTRODUCTION

Indications

IV: Control of blood pressure during surgical removal of a pheochromocytoma. IV, Infiltration: Prevention and treatment of dermal necrosis and sloughing following extravasation of norepinephrine, phenylephrine, or dopamine. Unlabeled Use: IM, IV: Treatment of hypertension associated with pheochromocytoma or adrenergic (sympathetic) excess, such as administration of phenylephrine, tyramine-containing foods in patients on MAO inhibitor therapy, or clonidine withdrawal.

Action

Produces incomplete and short-lived blockade of alpha-adrenergic receptors located primarily in smooth muscle and exocrine glands. Induces hypotension by direct relaxation of vascular smooth muscle and by alpha blockade. Therapeutic Effects: Reduction of blood pressure in situations in which hypertension is due to adrenergic (sympathetic) excess. When infiltrated locally, reverses vasoconstriction caused by norepinephrine or dopamine.

Adverse Reactions/Side

Effects With parenteral use

CNS: CEREBROVASCULAR SPASM, dizziness, weakness. EENT: nasal stuffiness. CV: HYPOTENSION, MI, angina, arrhythmias, tachycardia. GI: abdominal pain, diarrhea, nausea, vomiting, aggravation of peptic ulcer. Derm: flushing.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Continually monitor for signs of MI, including sudden chest pain, pain radiating into the arm or jaw, shortness of breath, dizziness, sweating, anxiety, and nausea. Seek immediate medical assistance if patient develops these signs.

• Be alert for signs of cerebrovascular spasm, including sudden severe headache, confusion, nausea, vomiting, dizziness, paralysis, numbness, speech problems, and visual disturbances. Report these signs to the physician or nursing staff immediately.

• Assess blood pressure (BP) periodically and compare to normal values (See Appendix F). Report low BP (hypotension), especially if patient experiences dizziness, fatigue, or other symptoms.

• Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Report any rhythm disturbances or symptoms of increased arrhythmias, including palpitations, chest pain, shortness of breath, fainting, and fatigue/weakness.

Interventions

• Because of the risk of MI, cerebrovascular spasm, and abnormal BP responses, use extreme caution during aerobic exercise and other forms of therapeutic exercise. Assess exercise tolerance frequently (BP, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

• To minimize orthostatic hypotension, patient should move slowly when assuming a more upright position.

Patient/Client-Related Instruction

• Advise patient and family or caregiver about the signs of MI and cerebrovascular spasm (see above under Examination and Evaluation), and to seek immediate medical assistance if these signs develop.

• Instruct patient or family/caregivers to report other bothersome side effects such as severe or prolonged nasal stuffiness, skin reactions (flushing), or GI problems (diarrhea, nausea, vomiting, abdominal pain, peptic ulcer).