Malignant Hyperthermia Susceptibility and the Trauma Patient

Military Medicine, Jun 2005 by Sheehan, Jacqueline A

Assorted casualties are expected from combat. Triage of the wounded may result in some going directly to surgery. Although every minute is essential, anesthetic care of these trauma patients must adhere to all established standards of care. A timely preoperative assessment must include identifying the patient's risk for malignant hyperthermia (MH). If a patient is found to be malignant hyperthermia susceptible, all appropriate measures must be taken to provide the patient with a safe anesthetic. In the forward, austere military environment, anesthesia providers may experience logistical and manpower constraints when administering anesthesia. In this setting, it may be more even more crucial for preoperative recognition of MH and when this is not possible, focus must shift to perioperative detection and early treatment. The following case report emphasizes the importance of preoperative recognition and having an established MH protocol and access to dantrolene.

Introduction

A 26-year-old male presented to the Emergency Medical Treatment (EMT) section of a level III Combat Support Hospital in Northern Iraq following a crush injury to the abdomen. The patient was conscious and described a history per interview of malignant hyperthermia (MH) diagnosed during a tonsillectomy as a child.

In the acutely injured trauma patient, circumstances may not allow for the preoperative identification of malignant hyperthermia susceptibility (MHS). Focus must then shift to preoperative recognition and treatment of the disorder. In this instance, MHS was immediately discovered preoperatively and the case proceeded with the avoidance of triggering agents. No changes indicative of MH, such as elevated central body temperature or end tidal carbon dioxide (ETCO^sub 2^), were detected. This report focuses on the importance of preoperative recognition and administering a trigger-free anesthetic for the trauma patient in the remote field anesthesia setting.

Case Report

A 26-year-old patient initially presented to a Battalion Aid Station (level I) in Northern Iraq after being pinned between two military vehicles, a Bradley and M88. Initial assessment at this level of care noted the patient was alert and oriented to person, place, and time, with no loss of consciousness; the patient's vital signs were stable with a slightly decreased blood pressure (BP), and physical examination revealed contusions on the abdomen. An intravenous line and fluids were started and the patient was air-evacuated to a higher echelon of care for further evaluation.

Upon arrival to the EMT section of a Combat Support Hospital (level III), on primary survey the patient had stable vital signs: BP, 130/80 mm Hg; pulse, 73 beats/minute; respiration, 28/. minute; and oxygen saturation of 98%. The FAST ultrasound was positive for blood on the right side. Past medical history was unremarkable and past surgical history included a tonsillectomy and adenoidectomy as a child. The patient stated he was allergic to "succinylcholine" and had a "bad reaction" to anesthesia as a child. He was unsure if he had ever been tested for MH. but other family members "died" from anesthesia. The patient was sent immediately to the operating room for an exploratory laparotomy.

Initial vital signs on arrival to the operating room were BP, 143/83 mm Hg; pulse, 81 beats/minute; saturation, 100% on 100% oxygen via non-rebreather mask; and relative risk, 24. The patient was premedicated with 2 mg of midazolam. General endotracheal anesthesia was initiated using a rapid sequence induction consisting of 100 µg of fentanyl, 14 mg of etomidate, and 50 mg of rocuronium. The airway was secured without difficulty. General anesthesia was maintained with total intravenous anesthesia consisting of propofol, fentanyl, midazolam, and rocuronium. ETCO^sub 2^ and core temperature were monitored throughout the case. The patient was hand-ventilated with a clean circuit on the anesthesia machine and 100% oxygen.

The case proceeded with total intravenous anesthesia. Initial hemoglobin and hematocrit were 47.3 and 15.4, respectively. Approximately 2 hours after incision, there was a decrease in blood pressure to 80/40 and increase in heart rate to 110. Estimated blood loss was 1000 mL. The patient was transfused with 2 units of packed red blood cells (PRBCs). The propofol infusion was discontinued and anesthesia was maintained with rocuronium and intermittent boluses of midazolam. Multiple attempts to place a radial arterial line were made without success. Vital signs stabilized following the transfusion of blood for the remainder of the case. Total intraoperative fluids included 2 L of normal saline, 4 L of lactated Ringer's, and 2 units of PRBCs. Urinary output was 300 mL. The following surgical procedures were performed: repair of a transected right rectus muscle and fascia; an excision of devitalized jejunum with sideto-side jejunostomy; a resection of jagged mesenteric laceration; and the closure of a mesenteric defect. Approximate surgical time was 3 hours.