Neuromuscular blockers — MCQs

During a nerve conduction study, which of the following ions is primarily responsible for the rapid upstroke of the action potential?

A 59-year-old woman is scheduled to undergo a right hip total arthroplasty for severe hip osteoarthritis that has failed conservative management. She has never had surgery before. She has a history of major depressive disorder and takes sertraline daily and ibuprofen occasionally for pain. Her mother died of breast cancer and her father died from a myocardial infarction. She has a brother who had an adverse reaction following anesthesia, but she does not know details of the event. In the operating room, the anesthesiologist administers isoflurane and succinylcholine. Two minutes later, the patient develops hypercarbia and hypertonicity of her bilateral upper and lower extremities. Her temperature is 103.7°F (39.8°C), blood pressure is 155/95 mmHg, pulse is 115/min, and respirations are 20/min. A medication with which of the following mechanisms of action is most strongly indicated for this patient?

A 46-year-old man presents after he accidentally got splashed with a liquid insecticide that was stored in a bucket in the storeroom one hour ago. He says that he can’t stop coughing and is having problems breathing. He also says he has a pain in his thighs which is unbearable, and his vision is blurry. His temperature is 36.7°C (98.1°F), the pulse is 130/min, the blood pressure is 144/92 mm Hg, and the respiratory rate is 20/min. On physical examination, the patient shows mild generalized pallor, moderate respiratory distress, excessive salivation, and diaphoresis. Cough is non-productive. Pupils are constricted (pinpoint). The cardiopulmonary exam reveals bilateral crepitus. The patient is administered atropine and pralidoxime, which help improve his symptoms. Which of the following is most likely to improve in this patient with the administration of atropine?

A 25-year-old man is scheduled for an orthopedic surgery. His routine preoperative laboratory tests are within normal limits. An urticarial reaction occurs when a non-depolarizing neuromuscular blocking agent is injected for muscle relaxation and mechanical ventilation. The patient’s lungs are manually ventilated with 100% O2 by bag and mask and then through an endotracheal tube. After a few minutes, edema of the face and neck rapidly ensues and giant hives appear over most of his body. Which of the following neuromuscular blocking agents was most likely used in this operation?

A neurophysiology expert is teaching his students the physiology of the neuromuscular junction. While describing the sequence of events that takes place at the neuromuscular junction, he mentions that as the action potential travels down the motor neuron, it causes depolarization of the presynaptic membrane. This results in the opening of voltage-gated calcium channels, which leads to an influx of calcium into the synapse of the motor neuron. Consequently, the cytosolic concentration of Ca2+ ions increases. Which of the following occurs at the neuromuscular junction as a result of this increase in cytosolic Ca2+?

A 23-year-old man is brought to the emergency department by ambulance following a motor vehicle accident. He was pinned between 2 cars for several hours. The patient has a history of asthma. He uses an albuterol inhaler intermittently. The patient was not the driver, and admits to having a few beers at a party prior to the accident. His vitals in the ambulance are stable. Upon presentation to the emergency department, the patient is immediately brought to the operating room for evaluation and surgical intervention. It is determined that the patient’s right leg has a Gustilo IIIC injury in the mid-shaft of the tibia with a severely comminuted fracture. The patient’s left leg suffered a similar injury but with damage to the peroneal nerve. The anesthesiologist begins to induce anesthesia. Which of the following agents would be contraindicated in this patient?

A 1-year-old boy presents to the emergency department with weakness and a change in his behavior. His parents state that they first noticed the change in his behavior this morning and it has been getting worse. They noticed the patient was initially weak in his upper body and arms, but now he won’t move his legs with as much strength or vigor as he used to. Physical exam is notable for bilateral ptosis with a sluggish pupillary response, a very weak sucking and gag reflex, and shallow respirations. The patient is currently drooling and his diaper is dry. The parents state he has not had a bowel movement in over 1 day. Which of the following is the pathophysiology of this patient’s condition?

A 16-year-old girl is brought to the emergency department by her friends who say that she took a whole bottle of her mom’s medication. They do not know which medication it was she ingested. The patient is slipping in and out of consciousness and is unable to offer any history. Her temperature is 39.6°C (103.2°F), the heart rate is 135/min, the blood pressure is 178/98 mm Hg, and the respiratory rate is 16/min. On physical examination, there is significant muscle rigidity without tremor or clonus. Which of the following is the best course of treatment for this patient?

A 50-year-old woman presents with acute onset fever and chills for the past hour. She mentions earlier in the day she felt blue, so she took some St. John’s wort because she was told by a friend that it helps with depression. Past medical history is significant for hypertension, diabetes mellitus, and depression managed medically with captopril, metformin, and fluoxetine. She has no history of allergies. Her pulse is 130/min, the respiratory rate is 18/min, the blood pressure is 176/92 mm Hg, and the temperature is 38.5°C (101.3°F). On physical examination, the patient is profusely diaphoretic and extremely irritable when asked questions. Oriented x 3. The abdomen is soft and nontender with no hepatosplenomegaly. Increased bowel sounds are heard in the abdomen. Deep tendon reflexes are 3+ bilaterally and clonus is elicited. The sensation is decreased in the feet bilaterally. Mydriasis is present. Fingerstick glucose is 140 mg/dL. An ECG shows sinus tachycardia but is otherwise normal. Which of the following is the most likely cause of this patient’s condition?

A 32-year-old woman is admitted to the hospital after undergoing an open cholecystectomy under general anesthesia. Preoperatively, the patient was administered a single dose of intravenous ceftriaxone. Now, the anesthetic effects have worn off, and her pain is well managed. The patient has a prior medical history of hypertension which has been well-controlled by captopril for 2 years. Her vitals currently show: blood pressure 134/82 mm Hg, heart rate 84/min, and respiratory rate 16/min. Postoperative laboratory findings are significant for the following: Serum glucose (random) 174 mg/dL Serum electrolytes Sodium 142 mEq/L Potassium 3.9 mEq/L Chloride 101 mEq/L Serum creatinine 0.9 mg/dL Blood urea nitrogen 10 mg/dL Alanine aminotransferase (ALT) 150 U/L Aspartate aminotransferase (AST) 172 U/L Serum bilirubin (total) 0.9 mg/dL Preoperative labs were all within normal limits. Which of the following drugs is most likely responsible for this patient’s abnormal laboratory findings?