A 70-year-old man with stable angina is scheduled for cataract removal with a retrobulbar block. After injection of 5 ml of 0.75% bupivacaine, heart rate decreases from 90 to 55 bpm, and frequent premature ventricular contractions are noted on the EKG. These changes are most likely caused by
Two days after myocardial infarction involving the left anterior descending coronary artery, a patient's blood pressure decreases acutely from 125/80 to 70/40 mmHg, heart rate increases from 75 to 90 bpm, pulmonary artery pressure increases to 50/30 mmHg, and urine output decreases from 60 to 10 ml/hr. Thermodilution cardiac output has increased from 4 to 7 L/min. The most appropriate action is to
(A) compare mixed venous oxygen saturation in the right atrium and pulmonary artery
(B) draw blood for culture and start antibiotic therapy
(C) start dopamine infusion in low dose
(D) administer a fluid challenge
(E) monitor peripheral capillary oxygenation by transcutaneous oximetry
A 72-year-old patient who takes levodopa and carbidopa is undergoing colon resection. Metoclopramide is administered preoperatively and anesthesia is maintained with proposal, fentanyl, and nitrous oxide, with vecuronium for muscle relaxation. Fifteen minutes after reversal of muscle relaxation with neostigmine and atropine and tracheal extubation, the patient has dyspnea and muscular rigidity. Which of the following is the most likely cause?
(A) Central anticholinergic syndrome
(B) Fentanyl-induced rigidity
(C) Inhibition of methionine synthetase by nitrous oxide