MalignantHyperthermia.

Malignant hyperthermia is a pharmacogenetic disorder. Patients with inherited mutations in the RYR1 gene (and less commonly CACNA1S) have abnormal calcium regulation in their skeletal muscle. Under most circumstances, this produces no symptoms. But when the patient is exposed to a triggering agent — any volatile inhaled anesthetic or the paralytic succinylcholine — calcium is released uncontrollably from the sarcoplasmic reticulum, muscles contract massively, metabolism accelerates, and body temperature rises precipitously.

Without treatment, the cascade leads to rhabdomyolysis (muscle breakdown), hyperkalemia (dangerous potassium elevation), metabolic and respiratory acidosis, disseminated intravascular coagulation, and multi-organ failure. Historical mortality was over 70 percent. Modern mortality — with prompt recognition, dantrolene administration, and supportive care — is approximately 5 percent.

That reduction did not happen by accident. It happened because the Malignant Hyperthermia Association of the United States (MHAUS) developed and disseminated clear protocols, because dantrolene became widely available, and because anesthesia training programs built MH recognition into every curriculum. The standard of care is well-defined and widely known. When outcomes are bad despite that infrastructure, the question is usually not whether MH could have been prevented — it is whether it was recognized and treated in time.

The triggering agents have been identified with precision:

• Volatile inhaled anesthetics. Sevoflurane, isoflurane, and desflurane are the commonly-used modern agents. All three can trigger MH in a susceptible patient. Halothane and enflurane are no longer in common use but triggered MH historically.
• Succinylcholine. A depolarizing paralytic used primarily for rapid-sequence induction. Triggers MH and is often the faster trigger of the two.
• Nitrous oxide. Not a trigger. Can be used in MH-susceptible patients.
• Propofol. Not a trigger. Widely used for total intravenous anesthesia (TIVA) in MH-susceptible patients.
• Nondepolarizing paralytics. Rocuronium, vecuronium, cisatracurium — not triggers. Safe alternatives to succinylcholine.
• Opioids, benzodiazepines, local anesthetics. Not triggers. Safe in MH-susceptible patients.

The consequence of this list is operational clarity. When a patient is known or suspected to be MH-susceptible, the anesthetic plan has a straightforward substitution: use a TIVA technique with propofol and a nondepolarizing paralytic, avoid volatile agents and succinylcholine, run the anesthesia machine in vapor-free mode. This is routine for any competent anesthesia team.

A common misconception is that MH begins with fever. It does not. Temperature rise is a late manifestation — sometimes hours into the crisis. The earliest signal, and the one that should trigger diagnostic suspicion, is a steadily-rising end-tidal CO2 reading despite adequate ventilation. Because capnography is continuous under modern anesthesia, the signal appears on the monitor in real time and in the record afterward.

The published progression:

• Rising end-tidal CO2. The earliest and most sensitive sign. The patient's accelerated metabolism produces CO2 faster than ventilation can remove it. A rising ETCO2 that does not respond to increased minute ventilation is, in the right context, MH until proven otherwise.
• Unexplained tachycardia. Heart rate rises as the body responds to the metabolic crisis. Often accompanies the ETCO2 rise.
• Masseter muscle rigidity after succinylcholine. When the jaw muscles remain rigid after succinylcholine administration, instead of relaxing as expected, MH susceptibility is a consideration.
• Generalized muscle rigidity. As the crisis progresses, diffuse muscle rigidity develops across the body.
• Temperature rise. Often 1°C every 5 minutes once established. A late sign — waiting for it is waiting too long.
• Metabolic acidosis, respiratory acidosis, hyperkalemia. Laboratory findings that confirm the hypermetabolic state.
• Rhabdomyolysis. Muscle breakdown releases myoglobin into the bloodstream. Dark-colored urine can be visible.
• Cardiac arrest. Without prompt intervention, often from hyperkalemia.

The American Society of Anesthesiologists and MHAUS have published standardized recognition and response protocols. Failure to recognize a classic ETCO2 rise in real time — when it is visible on the monitor — is a frequent finding in MH malpractice cases.

The MHAUS treatment protocol has been refined over decades and is the reference standard for MH management. The steps, in parallel:

• Discontinue all triggering agents. Stop the volatile anesthetic. Stop succinylcholine infusion if running. Change to a non-triggering anesthetic plan.
• Hyperventilate with 100% oxygen. High flows, full oxygen, high minute ventilation to manage the CO2 load and maximize oxygenation.
• Administer dantrolene. Initial dose 2.5 mg/kg IV, repeated every 5-10 minutes as needed. Total cumulative dose often reaches 10 mg/kg or higher. Ryanodex, a reformulated dantrolene, allows faster reconstitution than traditional dantrolene.
• Activate the MH emergency protocol. Call for additional staff, notify OR leadership, call the MH hotline (MHAUS operates one), ready ICU transfer.
• Cool aggressively. Cold IV fluids, surface cooling, nasogastric cold lavage for severe cases.
• Treat the metabolic derangements. Bicarbonate for acidosis. Insulin-dextrose, calcium, kayexalate for hyperkalemia. Pressors as needed for hemodynamic support.
• Maintain urine output. Mannitol or furosemide as needed to prevent myoglobin-induced renal injury.
• Transfer to ICU. Continuous monitoring post-crisis, given the risk of recrudescence (return of MH) in the first 24-48 hours.

The sequence is memorized by every anesthesia resident. The equipment — dantrolene, MH cart, cooling supplies — is expected to be immediately available in any facility performing general anesthesia. A facility that does not have adequate dantrolene on hand, or that has dantrolene located where it cannot be retrieved within minutes, is exposed at a systems level.

MH malpractice cases do not typically turn on whether MH was the correct diagnosis. The diagnosis is usually retrospectively clear — the ETCO2 trend, the temperature curve, the laboratory values, the response (or non-response) to dantrolene. What the cases turn on is whether the team acted in time given what they could see in real time.

The recurring breach patterns:

• Preoperative history missed. The patient or family reports a prior adverse anesthetic event, a family member who "died from anesthesia," or a known MH diagnosis in a relative. The preoperative assessment should specifically ask about all of these. Failure to ask, or failure to act on a positive answer, is a foundational breach.
• Known susceptibility ignored. A patient with a documented prior MH event, confirmed RYR1 mutation, or established MH in a first-degree relative is anesthetized with triggering agents anyway. Every major medical system has protocols for MH-susceptible patients; ignoring the flag is rare but recurring.
• Inadequate dantrolene supply. MHAUS recommends facilities stock sufficient dantrolene for initial treatment (at least 36 vials of traditional dantrolene, or the Ryanodex equivalent). Hospitals that administer volatile anesthetics and have insufficient dantrolene on hand face systems-level liability when an MH crisis exceeds the supply.
• Delayed recognition. The capnograph showed a steadily rising ETCO2 for 15 minutes before the team recognized MH as the cause. The anesthesia record will show both the ETCO2 trend and the timing of the diagnostic suspicion. Long gaps are common breach findings.
• Delayed dantrolene. Once the suspicion is raised, dantrolene must be mixed and administered. Traditional dantrolene requires reconstitution with sterile water — a process that takes time. Ryanodex is faster. Delay from decision to administration, if long, is another recurring breach pattern.
• Inadequate follow-up. Post-crisis, the patient is at risk for recrudescence for 24-48 hours and requires ICU monitoring. Discharge to a floor or home too soon has been documented in fatal recurrence cases.

Each of these patterns is documentable from the anesthesia record, the facility's emergency protocols, and the pharmacy records of dantrolene stocking and dispensing. Expert witnesses in MH cases are typically board-certified anesthesiologists with specific experience in MH management.

The evidentiary record in an MH case is unusually rich. Because anesthesia monitoring is continuous and automated, the ETCO2 trend, temperature curve, heart rate, and blood pressure are all logged minute-by-minute. Because dantrolene is a controlled substance that requires pharmacy dispensing or refrigerator-box removal, the exact time of administration is documentable. Because MH emergency protocols are written procedures, deviation from them is comparable against the written reference.

Key evidence categories:

• Anesthesia record. ETCO2 trend, temperature timeline, heart rate, blood pressure. When did abnormalities appear, and when did the team respond?
• Pharmacy and facility records. When was dantrolene removed from stock? How many vials? What was the timeline from the ETCO2 rise to dantrolene administration?
• MH cart inventory. Did the facility have the full recommended dantrolene supply and accessory supplies on hand?
• Preoperative assessment. Was family history of anesthesia complications asked about? What was documented?
• Genetic testing. Confirmed RYR1 or CACNA1S mutation establishes MH susceptibility and has implications for surviving family members.
• Expert witnesses. Board-certified anesthesiologist with MH experience; often an MHAUS-affiliated expert. For fatal cases, a forensic pathologist reviews the autopsy findings.

Under Florida Statute § 766.102, the corroborating expert affidavit must be from a same-specialty physician — a board-certified anesthesiologist — before the case can be filed. The 90-day pre-suit investigation required by § 766.203 applies. Fatal cases also raise Wrongful Death Act damages under Florida Statute § 768.21.