60 mg of IV morphine, and equianalgesic parenteral fentanyl dose would be 0.6–1.2 mg of Fentanyl daily (600–1200 mcg). Therefore, the hourly drip dose would be closest to 25–50 mcg/hr. Additionally, using higher than necessary continuous infusion rates (choices B through E) can cause opioid‐induced hyperalgesia. Continuous opioid infusions at inappropriately high doses contribute to oversedation and delayed extubation. In context, a simple rule is that fentanyl is 100 x more potent than morphine. An infusion of 100 μg/h fentanyl is equivalent to 10 mg of morphine per hour.Answer: AHurley RW, Hurley NM, Elkassabany and Wu CL. Acute Postoperative Pain. In: Miller RD, ed. Miller’s Anesthesia. 9th ed. Philadelphia, PA: Elsevier Saunders.MedicationEquianalgesic dose IV/IMEquianalgesic dose POTypical adult starting dose IVTypical adult starting dose POMorphine10 mg30 mg5–10 mg q3‐4h15–30 mg q3‐4hOxycodone20 mg5–10 mg q4‐6hFentanyl100 mcg (not patch)25 mcg/h transdermal (patch) equivalent PO morphine dose 45–75 mg50 mcg/h patch approx equal 1 mg/h morphine infusionMethadone10 mg20 mg5–10 mg q12hCodeine200 mg30–60 mg q3‐4hHydromorphone (Dilaudid)1.5 mg7.5 mg1–2 mg q3‐4h4–8 mg q3‐4h10 An 18‐year‐old boy is emergently intubated and exhibits masseter muscle spasm after induction with succinylcholine. He is in the OR for emergency surgery for a ruptured appendix. Which of the following additional symptoms would give you a heightened suspicion for malignant hyperthermia (MH)?BradycardiaEnd‐tidal CO2 of 35 mmHGRigidity of skeletal muscles of the limbsErythemaDiaphoresisThe onset of malignant hyperthermia can be heralded by tachycardia, trismus or masseter muscle spasm, and arrhythmias. Although concerning, as few as 20% of patients with masseter spasm progress to malignant hyperthermia. Triggers for MH include succinylcholine and inhalation anesthetic gases such as desflurane. This susceptibility to these triggers is due to genetic mutations with the most common one being the RYR1 gene or dihydropyridine (DHP) receptors located within the t‐tubule membrane. Monitoring for signs of MH such as increasing temperature, end‐tidal CO2, and rigidity of skeletal muscles is key to prompt recognition. MH can be rapidly fatal and treatment with Dantrolene must be started immediately. Dantrolene is a direct skeletal muscle relaxant that blocks calcium release by antagonistic effect at the ryanodine receptor (RYR1). Metabolism is increased in malignant hyperthermia resulting in hypercarbia (choice B), hyperthermia, and tachycardia (choice A). In this scenario, masseter muscle spasm in combination with rigidity of other muscle groups makes the diagnosis of malignant hyperthermia likely (choice C). Erythema (choice D) or diaphoresis (choice E) is not specific for malignant hyperthermia.Answer: CBandschapp O, Girard T. Malignant hyperthermia. Swiss Med Wkly. 2012; 142:w13652.Denborough M. Malignant hyperthermia. Lancet. 1998; 352(9134):1131–6.Sessler DI. Temperature Regulation and Monitoring. In: Miller RD, ed. Miller’s Anesthesia. 8th ed. Philadelphia, PA: Elsevier Saunders.
11 Which of the following medications is best reversed with Sugammadex (Bridon)?Succinylcholine (Anectine)Cisatracurium (Nimbex)Midazolam (Versed)Ropivacaine (Naropin)Rocuronium (Zemuron)Sugammadex (Bridon) is a dextran compound that surrounds and encapsulates the nondepolarizing aminosteroid muscle relaxant rocuronium, allowing for reversal of its effects. It cannot reverse succinylcholine (Anectine), a depolarizing muscle relaxant which makes choice A incorrect. While sugammadex can reverse some other nondepolarizing medications, it has a lower affinity for the other aminosteroid paralytics such as vecuronium (Norcuron). Therefore, the quality of reversal depends on the class, amount of muscle recovery, and class of paralytic agent used. Choice B is incorrect because Sugammadex cannot reverse benzylisoquinolinium relaxants such as cisatracurium (Nimbex). Choice E is the correct answer here. Dosages to reverse rocuronium (Zemuron) are based on actual body weight and recovery at the motor end plate. For example, if two or more twitch responses to stimulation are present, 2 mg/kg of actual body weight is given. A higher dose, 4 mg/kg is needed if post tetanic stimulation is needed to produce a twitch response. For immediate reversal of rocuronium, 16 mg/kg is recommended. Train of four (TOF) monitoring is used to assess recovery from and depth of neuromuscular blockade. When using paralytic agents in the ICU, TOF monitoring should be used. Choice C, midazolam (Versed) is a benzodiazepine and can be reversed with flumazenil (Romazicon). Choice D, Ropivacaine (Naropin) is a local anesthetic and can be reversed with lipid emulsions in case of systemic toxicity.Answer: EDuvaldestin P, Kuizenga K, Saldien V, Claudius C, Servin F, Klein J, Debaene B, Heeringa M. A randomized, dose‐response study of sugammadex given for the reversal of deep rocuronium‐ or vecuronium‐induced neuromuscular blockade under sevoflurane anesthesia. Anesth Analg. 2010; 110(1):74–82.Hunter JM. Reversal of residual neuromuscular block: complications associated with perioperative management of muscle relaxation. Br J Anaesth. 2017; 119(suppl_1):i53–i62.
12 A 75‐year‐old woman is admitted to the ICU after axillary to bifemoral bypass. Patient complains of pain from anterior thigh to her toes and a quadratus lumborum block is performed. What is the most serious complication of this procedure?HypertensionPostdural puncture headacheHyperemia of the legNumbness of the lumbar dermatomesRetroperitoneal hematomaBecause the quadratus lumborum block (QL) is a deep block, complications to watch out for include direct injury to the kidney, lumbar arteries, leading to retroperitoneal hematoma and pleural penetration leading to pneumothorax (choice E). A prolonged motor block may result from anesthetic distribution to the lumbar plexus. Hypotension, which can result from the spread of local anesthetic to the paravertebral space, has also been described (choice A). Local anesthetic toxicity (LAST) is always a potential risk of any peripheral or neuraxial technique. Rupture of the dura mater causing postdural puncture headache is a complication of an epidural catheter placement (wet tap) and not a complication of QL block (choice B). Numbness of the lumbar dermatomes (choice D) is the desired effect and hyperemia of the leg is transient and not a complication (choice C) (Figure 12.1).Figure 12.1 Quadratus lumborum block. QL: quadratus lumborum; EO: external oblique; IO: internal oblique; TA: transverse abdominis; K: kidney; P: psoas major; LD: latissimus dorsi; IL: iliocostalis lumborum; Lo: longissimus; Mu: multifidus.Answer: EElsharkawy H, El‐Boghdadly K, Barrington M. Quadratus lumborum block: anatomical concepts, mechanisms, and techniques. Anesthesiology. 2019; 130(2):322–335.Krohg A, Ullensvang K, Rosseland LA, Langesæter E, Sauter AR. The analgesic effect of ultrasound‐guided quadratus lumborum block after cesarean delivery: a randomized clinical trial. Anesth Analg 2018; 126(2):559–565.Blanco R, Ansari T, Girgis E. Quadratus lumborum block for postoperative pain after caesarean section: A randomised controlled trial. Eur J Anaesthesiol. 2015; 32(11):812–8.
13 A 60‐year‐old morbidly obese man with a difficult airway and obstructive sleep apnea was taken for emergent laparotomy for peritonitis. After awake fiberoptic intubation with benzocaine and induction of anesthesia, the oxygen saturation reads and remains 85% with good signal quality. His lips appear cyanotic, and he has bilateral breath sounds. Which of the following is the most likely cause?CarboxyhemoglobinemiaMethemoglobinemiaCyanide toxicityMain stem intubationHgb A1c level greater than 10%Acquired methemoglobinemia is potentially threatening and must be immediately recognized. The most common cause of methemoglobinemia is exposure to oxidizing agents such as benzocaine and nitroglycerine (choice B). When iron is ferrous oxidized to its ferric state, oxygen binding to hemoglobin is prevented which shifts the oxygen hemoglobin dissociation curve to the left. Excess methemoglobin leads to hypoxia, cyanosis, impaired aerobic respiration, and metabolic acidosis. Other etiologies are genetic deficiencies of cytochrome‐b5 and cytochrome‐b5 reductase. Unfortunately, pulse oximetry and arterial blood gases can be misleading in patients with methemoglobinemia. Co‐oximetry is the gold standard. Treatment options for methemoglobinemia include supportive measures, methylene blue, and vitamin C which are potent reducing agents. Methylene blue is contraindicated in G6PD deficiency.There are no triggering agents to cause Carboxyhemoglobinemia (i.e., Smoke inhalation with CO) and Cyanide toxicity (i.e., Smoke inhalation, Sodium Nitroprusside, Poisons) in this case which makes choices A and C unlikely. The patient is intubated fiber‐optically and has bilateral breath sounds which makes choice D unlikely. Choice E indicates untreated diabetes mellitus and is therefore incorrect.Answer: BGuay J . Methemoglobinemia related to local anesthetics: a summary of 242 episodes. Anesth Analg. 2009; 108(3):837.Anderson CM, Woodside KJ, Spencer TA, Hunter GC. Methemoglobinemia: An unusual cause of postoperative cyanosis. J Vasc Surg. 2004; 39(3):P686–690.
