7.17: Malignant Hyperthermia (Malignant Hyperpyrexia)
- Page ID
- 59720
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Malignant hyperthermia, was first described in Australia in 1960. It is a life threatening inherited (autosomal dominant) disorder of skeletal muscle. The incidence is 1:5,000 to 1:200,000. Exposure to triggering agents (suxamethonium and volatile anesthetics) causes a reduction in calcium reuptake by the sarcoplasmic reticulum, which causes sustained muscle contraction.
Malignant hyperthermia usually occurs in the operating room but can occur up to 11 hours postoperatively. It can occur in patients who have had normal anesthetics in the past.
Assessment
Symptoms of malignant hyperthermia may include: Sustained muscle contraction. Masseter spasm may be an early sign of malignant hyperthermia but not all patients with masseter spasm will have malignant hyperthermia.
Symptoms of malignant hyperthermia may include: Sustained muscle contraction. Masseter spasm may be an early sign of malignant hyperthermia but not all patients with masseter spasm will have malignanthyperthermia.Muscle breakdown causing hyperkalaemia and myoglobinemia. Hyperkalaemia above 6.5 mmol/l will cause ECG changes including tall peaked T waves, prolonged PR interval, loss of P waves and widening of the QRS complexes. Hyperkalaemia will cause ventricular arrhythmias including ventricular fibrillation and cardiac arrest.Increased metabolism causing increased oxygen consumption and carbon dioxide production. Spontaneously breathing patients will hyperventilate. Increased temperature of up to 1°C every 5 minutes. The patient’s temperature may reach 45°C. The rise in temperature is often a late sign of malignant hyperthermia. Tachycardia Metabolic acidosis.
Complications of malignant hyperthermia include disseminated intravascular coagulopathy, acute tubular necrosis and death.
Other conditions that cause unexplained tachycardia, increased metabolism or increased temperature may appear like malignant hyperthermia. These include light anaesthesia, infection, hyperthyroidism, pheochromocytoma and drug reactions (neuroleptic malignant syndrome, cocaine overdose).
Prevention
The anesthetist must always take a careful family anaesthetic history. As malignant hyperthermia is an inherited disorder, other members of the patient’s family may have had an unexplained death during anaesthesia. If at all suspicious avoid the triggering agents suxamethonium and volatile anaesthetic agents. For patients known to have malignant hyperthermia the anesthetist must avoid the triggering agents. The anaesthetic machine should have the vaporizer removed, the anaesthetic tubing and bag and new soda lime should be new. The anaesthetic machine should be flushed with 100% oxygen (10 L/min) for at least 10 minutes.Patients suspected of having malignant hyperthermia can be diagnosed by a muscle biopsy test.
Management
Malignant hyperthermia is a life threatening disorder that can develop rapidly and requires multiple treatment tasks.
Dantrolene is the only drug that can reverse the effect of malignant hyperthermia.
Call for help.
Stop the volatile anesthetics (anaesthesia can be maintained by intravenous propofol and opioid).
Hyperventilate the patient with 100% oxygen.
Check the ECG for signs of hyperkalaemia (hyperkalaemia can be treated with an intravenous infusion of 100 ml of 10% dextrose with 10 units of insulin over 30 minutes or sodium bicarbonate 50 to 150 mEq. Calcium gluconate 10 mls of 10% may be given for severe hyperkalaemia). Check the temperature. If the temperature rises above 38°C try to cool the patient (surface cooling with cool water or ice, cold intravenous fluids, gastric lavage with cold water).
Check the urine output. Patients are at risk of acute tubular necrosis. Try to keep the urine output greater than 2 ml/kg/h with intravenous fluids and frusemide.
Be prepared to treat ventricular arrhythmias (procainamide 3 mg/kg or lignocaine).
Dantrolene should be administered as soon as malignant hyperthermia is suspected. Unfortunately the drug is expensive and has a short shelf life. The dantrolene dose is2.5 mg/kg repeated every 10 minutes if needed up to 10 mg/kg.