Question

Epinephrine is commonly included in formulations of local anesthetics such as lidocaine. Epinephrine itself does not have analgesic properties; however, it is able to minimize the systemic distribution of a lidocaine by promoting vascular occlusion.

· What beneficial action does epinephrine produce in vascular smooth muscle, which explains why it is mixed with lidocaine? How does the addition of epinephrine to lidocaine aid in the localization of the anesthetic effect?

It is common for patients with diabetes mellitus to have the comorbidity of hypertension. Beta adrenergic receptor antagonists (i.e., “beta blockers”) are commonly used in treating hypertension; however, they are not considered a first-line antihypertensive treatment, particularly for patients with diabetes. [As an aside, diabetic patients will commonly be able to “sense” their blood sugar is low due to “feeling shaky” and experiencing a rapid heartbeat and lightheadedness.]

· Why should beta blockers be used with caution in patients with diabetes mellitus?

· Based on their differences in receptor specificity, what additional concerns would a nurse have about a diabetic patient receiving propranolol [versus metoprolol]?

Answer 1

1. What beneficial action does epinephrine produce in vascular smooth muscle, which explains why it is mixed with lidocaine? How does the addition of epinephrine to lidocaine aid in the localization of the anesthetic effect?

Epinephrine does counteract the vasodilatory action in vascular smooth muscle by constricting blood vessels which means it causes contraction of the smooth muscle that lines most arterioles, thus decreasing blood flow to the injection area. The addition of lidocaine is used to reduce the rate of vascular absorption of the local anesthetic by slowed absorption into the cardiovascular system and thus resulting in lower anesthetic level & minimizing the risk of local anesthesia toxicity resulting in increasing the duration of anesthesia by allowing the local anesthesia to remain around the nerve for a longer period of time.

Why should beta blockers be used with caution in patients with diabetes mellitus? Based on their differences in receptor specificity, what additional concerns would a nurse have about a diabetic patient receiving propranolol [versus metoprolol]?

As the function of the beta blockers is reduction of heart beats and in case of diabetes the lowering of heartbeats can be due to low blood sugar. SO the distinction might not be easy to pin point and hence it is to be used in caution patients with diabetes mellitus

Based on their differences in receptor specificity, the additional concerns a nurse might have about a diabetic patient receiving propranolol is that it may mask some of the signs or symptoms of low blood sugar (hypoglycemia) and as compared to metoprolol it could worsen metabolic control in patients and increase the risk of cardiovasular risk factors.