Allergic Reaction to Vasoconstrictors
Vasoconstrictors (epinephrine and levonordefrin) are added to local anesthetics to counteract their vasodilatory action by constricting blood vessels, thus decreasing blood flow to the injection area. The absorption of the local anesthetic into the cardiovascular system is slowed resulting in lower anesthetic levels, minimizing the risk of local anesthesia toxicity and increasing the duration of anesthesia by allowing the local anesthesia to remain around the nerve for a longer period of time.
If too much vasoconstrictor is injected or the anesthetic is injected intravascularly, the vasoconstrictor is absorbed into the vascular system just as the anesthetic (see Table 3). Overuse of gingival retraction cord, especially in patients with a history of cardiovascular disease can cause vasoconstrictor toxicity. Increased vasoconstrictor into the blood stream causes moderate increases in systolic and diastolic blood pressures, cardiac output and stroke volume. These actions lead to an overall decrease in cardiac efficiency.
After reviewing the pre-operative medical history, the vasoconstrictor use should be avoided or minimized in:
Patients with a blood pressure in excess of 200 mm Hg systolic or 115 mm Hg diastolic.
Patients with uncontrolled hyperthyroidism.
Patients with severe cardiovascular disease.
Less than 6 months after myocardial infarction, post-coronary bypass surgery or cerebrovascular incident.
Daily episodes of angina pectoris.
Patients receiving halogenated general anesthetic agents.
Patients receiving nonspecific ß-blockers, MAO inhibitors, or tricyclic antidepressants.
The signs and symptoms of vasoconstrictor toxicity are:
Tachypnea (abnormal rapid breathing)
Should a patient experience vasoconstrictor toxicity, the following steps should be taken:
Reassure the patient
Assess and support circulation, airway, and breathing
Monitor vital signs