A 42-year-old woman is evaluated in the postoperative care unit for sudden-onset tachycardia and dyspnea 15 minutes after surgery. The patient underwent a dilation and curettage for gestational trophoblastic diseases complicated by intraoperative bleeding that required 2 units of packed red blood cells. The bleeding was controlled, and the remainder of the procedure and subsequent extubation were uneventful. The patient has a 10-pack-year smoking history but no other medical conditions or prior surgeries. She takes no daily medications. Temperature is 37.8 C (100 F), blood pressure is 160/110 mm Hg, pulse is 134/min, and respirations are 38/min. The patient appears diaphoretic and has shallow, labored breathing. Cardiac examination shows sinus tachycardia with no rubs or murmurs. The lungs are clear to auscultation bilaterally. The abdomen has no marked distension, rebound, or guarding. Bilateral extremities have generalized rigidity. The Foley catheter is draining brown-appearing urine. Which of the following is the most likely diagnosis for this patient?

Question

A 42-year-old woman is evaluated in the postoperative care unit for sudden-onset tachycardia and dyspnea 15 minutes after surgery.  The patient underwent a dilation and curettage for gestational trophoblastic diseases complicated by intraoperative bleeding that required 2 units of packed red blood cells.  The bleeding was controlled, and the remainder of the procedure and subsequent extubation were uneventful.  The patient has a 10-pack-year smoking history but no other medical conditions or prior surgeries.  She takes no daily medications.  Temperature is 37.8 C (100 F), blood pressure is 160/110 mm Hg, pulse is 134/min, and respirations are 38/min.  The patient appears diaphoretic and has shallow, labored breathing.  Cardiac examination shows sinus tachycardia with no rubs or murmurs.  The lungs are clear to auscultation bilaterally.  The abdomen has no marked distension, rebound, or guarding.  Bilateral extremities have generalized rigidity.  The Foley catheter is draining brown-appearing urine.  Which of the following is the most likely diagnosis for this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d898_2844_bc81_49bf4a1716be_MD0003_00 This patient developed tachycardia, dyspnea, generalized muscle rigidity, and dark urine soon after general anesthesia, raising strong suspicion for malignant hyperthermia (MH). MH is an autosomal dominant or sporadic skeletal muscle receptor disorder marked by excessive calcium release following exposure to succinylcholine or a volatile anesthetic (eg, halothane). In MH, sustained muscle contraction leads to: hypercarbia (due to increased levels of cellular metabolism) that does not improve with increased minute ventilation (tachypnea) sinus tachycardia masseter/generalized muscle rigidity myoglobinuria, as seen in this patient with dark urine (due to muscle breakdown) hyperthermia (late manifestation due to the sustained contractions generating more energy than the body can dissipate; not usually present initially). Most cases arise shortly after induction or during maintenance of anesthesia, but symptoms can occur soon after anesthetic cessation. Urgent treatment with dantrolene (a skeletal muscle relaxant) and supportive care are required to prevent death. (Choice A) Disseminated intravascular coagulation can be due to ABO-incompatible blood transfusion but is most common with infection, malignancy, trauma, and obstetric complications. It generally presents with bleeding symptoms such as oozing from catheters, drains, or incisions. Muscle rigidity would be atypical. (Choice C) Neuroleptic malignant syndrome is often associated with rigidity, myoglobinuria, tachypnea, and tachycardia. However, it is caused by administration of a neuroleptic agent (eg, haloperidol, fluphenazine), not by surgery or surgical anesthesia. In addition, most cases progress over a few days, not minutes. (Choice D) Pulmonary embolism is a common complication of surgery and is frequently associated with sinus tachycardia and dyspnea. However, most cases occur >24 hours after surgery (not immediately) due to immobility. Furthermore, muscle rigidity and dark urine would be uncommon. (Choice E) Transfusion-related acute lung injury usually presents during or shortly after blood transfusion with acute dyspnea, hypoxia, and lung infiltrates. Muscle rigidity and a clear lung examination make this diagnosis less likely. Educational objective: Malignant hyperthermia is a genetic disorder associated with sudden-onset tachypnea, tachycardia, myoglobinuria, and masseter/generalized muscle rigidity following exposure to succinylcholine or a volatile anesthetic. Most cases arise during or shortly after induction, but symptoms are sometimes delayed until just after anesthesia cessation.

A 42-Year-Old Woman Is Evaluated in the Postoperative Care Unit