An in-vivo metabolic test for detecting malignant hyperthermia susceptibility in humans: a pilot study

The current status of malignant hyperthermia

Malignant hyperthermia (MH) is a rare and life-threatening pharmacogenetic disorder triggered by volatile anesthetics, the depolarizing muscle relaxant succinylcholine, and rarely by strenuous exercise or environmental heat. The exact prevalence of MH is unknown, and it varies from 1:16 000 in Denmark to 1:100 000 in New York State. The underlying mechanism of MH is excessive calcium release from the sarcoplasmic reticulum (SR), leading to uncontrolled skeletal muscle hyper-metabolism. Genetic mutations in ryanodine receptor type 1 ( RYR1) and CACNA1S have been identified in approximately 50% to 86% and 1% of MH-susceptible (MHS) individuals, respectively. Classic clinical symptoms of MH include hypercarbia, sinus tachycardia, masseter spasm, hyperthermia, acidosis, muscle rigidity, hyperkalemia, myoglobinuria, and etc. There are two types of testing for MH: a genetic test and a contracture test. Contracture testing is still being considered as the gold standard for MH diagnosis. Dantrolene is the only available drug approved for the treatment of MH through suppressing the calcium release from SR. Since clinical symptoms of MH are highly variable, it can be difficult to establish a diagnosis of MH. Nevertheless, prompt diagnosis and treatments are crucial to avoid a fatal outcome. Therefore, it is very important for anesthesiologists to raise awareness and understand the characteristics of MH. This review summarizes epidemiology, clinical symptoms, diagnosis and treatments of MH and any new developments.

Ultrasound Elastography for Rapid, Real-time Detection of Localized Muscular Reaction in Malignant Hyperthermia-susceptible Pigs

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Halothane and caffeine induce excessive sarcoplasmic calcium liberation and skeletal muscle contracture in patients susceptible to malignant hyperthermia (MH) and are utilized for diagnosis in the in vitro contracture test. Intramuscular injection previously caused a marked local lactate increase in MH-susceptible but not in MH-nonsusceptible individuals in vivo. Using shear-wave elastography, this study evaluated localized changes in muscle stiffness after intramuscular injection of halothane and caffeine.

METHODS

Microdialysis probes were placed into the gracilis muscle of 16 pigs (9 MH-susceptible and 7 MH-nonsusceptible). After local injection of either halothane or caffeine in different concentrations, changes of tissue elasticity surrounding the probe were examined by quantitative shear-wave elastography. Local lactate concentrations were analyzed spectrophotometrically.

RESULTS

Ultrasound elastography detected a temporary increase in local muscle rigidity in MH-susceptible but not in MH-nonsusceptible pigs after 2.5 and 5 vol% halothane and after 10, 40, and 80 mM caffeine, whereas there were no differences in the control groups (median [interquartile range] for maximum effect after 5 vol% halothane: MH-susceptible: 97 [31 to 148] vs. MH-nonsusceptible: 5 [-6 to 18] kPa; P = 0.0006; maximum effect after 80 mM caffeine: 112 [64 to 174] vs. -3 [-6 to 35] kPa; P = 0.0002). These effects were seen rapidly within 5 min. Local lactate concentrations were higher in MH-susceptible versus nonsusceptible pigs after 1 and 2.5 vol% halothane and 10, 40, and 80 mM caffeine (2.5 vol% halothane: MH-susceptible: 2.8 [1.9 to 4.4] vs. MH-nonsusceptible: 0.6 [0.6 to 0.7] mmol/l; P < 0.0001; 80 mM caffeine: 5.2 [4.1 to 6.3] vs. 1.6 [1.2 to 2.4] mmol/l; P < 0.0001). After 10 vol% halothane, rigidity and lactate levels were increased in both MH-susceptible and MH-nonsusceptible animals.

CONCLUSIONS

This pilot study revealed shear-wave elastography as a suitable technique for real-time detection of altered tissue elasticity in response to pharmacologic stimulation. By considering the variability of these results, further test protocol optimization is required before elastography could serve as a minimally invasive MH diagnostic test.

Malignant Hyperthermia

Malignant Hyperthermia (MH) is a life-threatening pharmacogenetic disorder which results from exposure to volatile anesthetic agents and depolarizing muscle relaxants. It manifests as a hypermetabolic response resulting in tachycardia, tachypnea, hyperthermia, hypercapnia, acidosis, muscle rigidity and rhabdomyolysis. An increase in the end-tidal carbon dioxide is one of the earliest diagnostic signs. Dantrolene sodium is effective in the management of MH, and should be available whenever general anesthesia is administered. This review also aims to highlight the genetics and pathology of MH, along with its association with various inherited myopathy syndromes like central core disease, multi-mini core disease, Native-American myopathy, and King-Denborough syndrome.

Metabolic effects as a cause of myotoxic effects of fluoroquinolones

OBJECTIVES

To investigate if fluoroquinolones (FQs) influence skeletal muscle metabolism of healthy and malignant hyperthermia susceptible (MHS) pigs.

MATERIALS AND METHODS

After approval from of the Animal Care Committee, 10 MHS pigs, and 6 MHS pigs were anesthetized with hemodynamic and systemic metabolic monitoring. Microdialysis catheters were placed intramuscularly. After equilibration, levofloxacin and ciprofloxacin were injected as a rapid bolus and continuous infusions. Lactate was measured in the dialysate and statistically analyzed was done (Wilcoxon-test; U-test; P < 0.05).

RESULTS

There were no differences in age, weight, and baseline lactate levels between the groups. Both applications of levofloxacin- and ciprofloxacin-induced an increase of local lactate levels in healthy and MHS pigs. No difference between the two groups was observed.

CONCLUSION

FQs influence skeletal muscle metabolism. Myotoxic effects of FQs can, therefore, be explained by an influence on the cellular energy balance.

Management of malignant hyperthermia: diagnosis and treatment

Malignant hyperthermia is a potentially lethal inherited disorder characterized by disturbance of calcium homeostasis in skeletal muscle. Volatile anesthetics and/or the depolarizing muscle relaxant succinylcholine may induce this hypermetabolic muscular syndrome due to uncontrolled sarcoplasmic calcium release via functionally altered calcium release receptors, resulting in hypoxemia, hypercapnia, tachycardia, muscular rigidity, acidosis, hyperkalemia, and hyperthermia in susceptible individuals. Since the clinical presentation of malignant hyperthermia is highly variable, survival of affected patients depends largely on early recognition of the symptoms characteristic of malignant hyperthermia, and immediate action on the part of the attending anesthesiologist. Clinical symptoms of malignant hyperthermia, diagnostic criteria, and current therapeutic guidelines, as well as adequate management of anesthesia in patients susceptible to malignant hyperthermia, are discussed in this review.

A minimal-invasive metabolic test detects malignant hyperthermia susceptibility in a patient after sevoflurane-induced metabolic crisis

Malignant hyperthermia is a rare but life-threatening complication of general anesthesia in predisposed patients usually triggered by potent inhalation anesthetics and/or the depolarizing muscle relaxant succinylcholine. The authors present a case of delayed sevoflurane-induced malignant hyperthermia in a 21-year-old male patient that was sufficiently treated by discontinuation of trigger agent application and dantrolene infusion. After surviving an MH episode diagnostic procedures are indicated to increase patient safety. In the presented case, the use of a novel minimal-invasive metabolic test with intramuscular injection of halothane and caffeine successfully confirmed MH susceptibility and hence might be an alternative for invasive in vitro contracture testing in selected cases.

Minimally invasive metabolic testing for malignant hyperthermia susceptibility: a systematic review of the methodology and results

IMPORTANCE OF THE FIELD

Malignant hyperthermia (MH) is a potentially lethal hypermetabolic syndrome that develops in susceptible individuals exposed to volatile anesthetics or depolarizing neuromuscular blocking agents. Because genetic screening is successful only in 30 - 50% of all suspected cases, contracture testing following an open muscle biopsy is performed to diagnose MH susceptibility. Two different protocols exist, the in vitro contracture test (IVCT) for Europe and the caffine halothane contracture test for the US. As replacement for the IVCT, an in vivo metabolic test might allow an equal discrimination of MH susceptible individuals. In this systematic review, all available metabolic testing methods are analyzed.

WHAT THE READER WILL GAIN

The reader will gain insight in methods and results of alternative approaches to diagnose MH.

AREAS COVERED IN THIS REVIEW

Relevant studies involving in vivo metabolic testing were systematically searched (Medline) and reviewed. Their ability to discriminate MH susceptible individuals was analyzed and compared. Any systemic or local side effects were documented and evaluated in order to allow more robust conclusions based on larger sample sizes than the single trials.

TAKE HOME MESSAGE

All discussed study protocols allowed an adequate discrimination of MH susceptible individuals. The latest study protocol reaches a specificity of 79% with a sensitivity of 100%. No severe systemic or local adverse effects could be seen in the pooled analysis. Minimally invasive metabolic testing is a promising novel approach to diagnose MH. Further multi-center studies have to be conducted to optimize the results in order to replace the IVCT.

Screening test for malignant hyperthermia in patients with persistent hyperCKemia: a pilot study

INTRODUCTION

Persistently elevated serum creatine kinase (CK) is frequently associated with predisposition to malignant hyperthermia (MH). We investigated whether a minimally invasive metabolic test is suitable to diagnose MH susceptibility among patients with hyperCKemia.

METHODS

Thirty-nine participants were included: 10 were MH susceptible (MHS); 21 MH were non-susceptible (MHN); and 8 had MHN with persistent hyperCKemia >500 U/L. Microdialysis probes were inserted into the vastus lateralis muscle, and halothane or caffeine was injected via an attached microtubing catheter. Lactate concentrations in dialysis samples were measured spectrophotometrically.

RESULTS

Baseline lactate did not differ between the groups. After local application of halothane or caffeine, a significant lactate increase was detected only in the MHS group.

CONCLUSIONS

Test results were not influenced by hyperCKemia. To avoid risks and complications of a surgical muscle biopsy this microdialysis test might be a useful screening tool for MH susceptibility among patients with persistent CK elevation.

Minimally invasive monitoring of skeletal muscle hypermetabolism induced by the phosphodiesterase-III-inhibitor milrinone and sodium fluoride

OBJECTIVES

We hypothesized that the phosphodiesterase-III-inhibitor milrinone and the non-specific G-protein activator sodium fluoride increase the skeletal muscular lactate levels as a sign of a hypermetabolic response.

METHODS

With approval of the local animal care committee Sprague-Dawley rats were killed and artificially perfused either with Ringer's solution or sodium fluoride 110 mM, while milrinone 1.32 mM or Ringer's solution at 1 μl/min was applied via microdialysis probes in both hind limbs. Lactate was measured spectrophotometrically in the dialysate.

KEY FINDINGS

Baseline lactate levels before drug application did not differ between hind limbs. Local infusion of milrinone via microdialysis did not significantly increase intramuscular lactate concentrations compared with the Ringer control group. Muscular perfusion with sodium fluoride resulted in a significant increase of lactate and was potentiated by combination with local milrinone.

CONCLUSIONS

Phosphodiesterase-III-inhibition alone does not significantly influence the lactate levels in skeletal muscle of sacrificed rats. Sodium fluoride infusion leads to an intramuscular lactate increase, which was further potentiated by local inhibition of phosphodiesterase-III. The fluoride-mediated hypermetabolic response following sodium fluoride could be a possible explanation for the observed myotoxic adverse effects in individuals treated by fluoride-containing agents.

Malignant hyperthermia in the oral and maxillofacial surgery patient: an update

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that presents as a hypermetabolic response to potent volatile anesthetic gases, such as halothane, sevoflurane, desflurane, the depolarizing muscle relaxant succinylcholine, and, rarely in humans, to stresses, such as vigorous exercise and heat. The syndrome is likely to be fatal if untreated. Early recognition of the signs of MH provides the clinical diagnostic clues. Diagnostic testing relies on assessing the in vitro contracture response of biopsied muscle to halothane, caffeine, and other drugs. Dantrolene sodium is a specific antagonist of the pathophysiologic changes of MH and should be available wherever general anesthesia is administered. The prevention and treatment of acute episodes of this disorder is of paramount importance to the oral and maxillofacial surgeon. The management of such patients in the oral and maxillofacial surgery setting and the recent advances in the field of MH are presented.