A 34-year-old carpenter presents to the emergency room after an accident in which he inadvertently chopped off the tip of his index finger. He is taken to the operating room for reattachment of the digit, and after sedation, a local anesthetic is administered around the site of the injury. The local anesthetic used in the procedure did not contain any epinephrine, as it usually does for most surgical procedures. The reason for this is

Correct Answer: D

Rationale: The correct answer is D. Epinephrine causes vasoconstriction, which can lead to vascular ischemia in digits. In delicate surgeries like finger reattachment, maintaining adequate blood flow is crucial for successful outcomes. Using epinephrine can constrict blood vessels excessively, leading to reduced blood supply and potential tissue damage. This can result in vascular ischemia, compromising the viability of the reattached finger. Explanation for incorrect choices: A: Epinephrine actually helps in reducing blood loss by constricting blood vessels. B: Epinephrine reduces tissue swelling, making surgery easier. C: Epinephrine is not contraindicated in emergency surgery; it is often used to control bleeding and prolong anesthesia.

Correct Answer: B

Rationale: The correct answer is B: Prazosin. α-1 adrenergic receptors are selectively blocked by prazosin. Prazosin is a selective α-1 adrenergic receptor antagonist, specifically targeting these receptors. It works by blocking the effects of norepinephrine, leading to vasodilation and reduced blood pressure. A: Phentolamine is a non-selective α-adrenergic receptor antagonist, blocking both α-1 and α-2 receptors. C: Propranolol is a non-selective β-adrenergic receptor antagonist, blocking β-1 and β-2 receptors. D: Ergotamine is a medication used for the treatment of migraines and has vasoconstrictive properties but does not selectively block α-1 adrenergic receptors.

Correct Answer: D

Rationale: The correct answer is D because physostigmine is used in the treatment of glaucoma due to its ability to lower intraocular pressure. It works by inhibiting the enzyme acetylcholinesterase, leading to increased levels of acetylcholine which helps in constricting the pupil and improving drainage of fluid in the eye. Options A and C are incorrect as physostigmine is a tertiary amine and a reversible anti-cholinesterase. Option B is incorrect as physostigmine does have CNS action, crossing the blood-brain barrier and affecting brain function.

Correct Answer: D

Rationale: The correct answer is D because anticholinesterase drugs are not bronchodilators; they actually increase cholinergic activity by inhibiting the breakdown of acetylcholine. Reversible and irreversible types do exist (A), neostigmine and physostigmine are examples (B), and they can cause miosis and lacrimation due to increased cholinergic activity (C). Hence, D is the incorrect statement.

Correct Answer: C

Rationale: Rationale: Edrophonium is used to differentiate myasthenia crisis and cholinergic crisis by temporarily improving muscle weakness in myasthenia crisis but worsening symptoms in cholinergic crisis. Neostigmine (A) and Succinylcholine (D) can exacerbate cholinergic crisis. Hyoscine (B) is not used for this purpose.