The patient underwent a comprehensive preoperative assessment, which included a neurological examination. The examination confirmed spasticity and hypertonia but showed no signs of progressive neuromuscular deterioration. A preoperative anteroposterior radiograph confirmed severe spinal curvature consistent with neuromuscular scoliosis (Figure 1). Lateral imaging further demonstrated thoracolumbar deformity and pelvic obliquity (Figure 2), highlighting the extent of musculoskeletal compromise preoperatively. Pulmonary function testing revealed mild restrictive lung disease, characterized by reduced forced vital capacity (FVC) but adequate baseline oxygenation, indicating a potential for intraoperative respiratory challenges. Anesthetic considerations were thoroughly discussed, focusing on anesthesia risks related to neuromuscular disorders, airway management strategies, and the avoidance of succinylcholine and volatile anesthetics whenever possible to minimize the risk of MH. Despite these considerations, MH susceptibility testing was not performed, as the patient had no known family history of MH and had previously undergone general anesthesia without complications.

Anesthesia was induced with propofol (2 mg/kg), fentanyl (2 mcg/kg), and rocuronium (0.6 mg/kg) to facilitate endotracheal intubation. Maintenance anesthesia consisted of a propofol infusion, rocuronium, and sevoflurane. Standard intraoperative monitoring included continuous capnography, pulse oximetry, electrocardiography, invasive arterial blood pressure monitoring, and temperature measurement. Ninety minutes into the procedure, the patient exhibited a sudden increase in end- tidal carbon dioxide (EtCO₂) to 60 mmHg, despite adequate ventilation. This was followed by a rapid pulse increase to 190 bpm, hypotension (70/40 mmHg), hyperthermia (41°C), and muscle rigidity. Capnography played a crucial role in early detection, showing a rapid rise in EtCO₂, prompting immediate intervention. Based on these findings, a clinical diagnosis of MH was made. Sevoflurane was immediately discontinued, and the anesthesia machine was flushed and replaced to prevent further exposure. Anesthesia was then maintained using a propofol infusion (100–150 mcg/kg/min) with intermittent fentanyl boluses (1 mcg/kg), while neuromuscular relaxation continued with rocuronium. This non- triggering TIVA protocol was upheld for the remainder of the surgery. The crisis occurred 90 min into scoliosis correction surgery using sevoflurane, a known MH trigger, and involved deep muscular dissection, which may have contributed to the onset. The patient was pressure- ventilated with a tidal volume of 6–8 ml/kg, a respiratory rate of 14/min, and FiO₂ of 0.0.5, with a baseline EtCO₂ of 35–40 mmHg. At the onset of MH, the EtCO₂ spiked to 60 mmHg, with HR at 190 bpm, BP at 70/40 mmHg, and a core temperature of 41°C. Arterial blood gas analysis revealed a pH of 7.21, PaCO₂ of 48 mmHg, HCO_3⁻ of 17 mmol/L, as well as elevated serum potassium (5.9 mmol/L) and lactate (5.2 mmol/L). Urine appeared dark brown within 30 min, suggesting myoglobinuria. Serum CK was measured at 9, 800 U/L, and myoglobin levels at 520 ng/ml. Circulatory support included IV crystalloids (20 ml/kg bolus), norepinephrine infusion (0.05 mcg/kg/min), and the correction of metabolic acidosis with bicarbonate. Urine pH was not measured, but the appearance was dark brown, indicating myoglobinuria. Laboratory markers of muscle breakdown were elevated, including a peak creatine kinase (CK) of 9,800 U/L and serum myoglobin of 520 ng/ml, consistent with rhabdomyolysis. Vital signs improved over 60 min: HR decreased to 120 bpm, BP increased to 120/60 mmHg, and temperature lowered to 37.7°C, enabling surgical continuation. A graphical representation of the intraoperative physiological parameters was created to depict the progression and management of the MH episode (Figure 3). The graph displays the temporal trends in EtCO₂, HR, BP, and core temperature from baseline to peak crisis and subsequent stabilization following dantrolene administration and cooling measures.

Sevoflurane was immediately discontinued, and the ventilator circuit, including soda lime, was replaced to allow for 100% oxygen inhalation and hyperventilation. The patient was treated with an initial intravenous bolus of dantrolene at 2.5 mg/kg, followed by two additional boluses of 1 mg/kg each, totaling 4.5 mg/kg intraoperatively. A maintenance dose of 1 mg/kg was administered every 6 h for 24 h postoperatively to prevent recurrence. Metabolic acidosis correction was achieved using a total of 60 mEq of sodium bicarbonate, administered as a 30 mEq IV bolus over 10 min, followed by a continuous infusion of 30 mEq over 1 h, guided by serial arterial blood gas measurements. The temperature decreased to 37.7°C within 30 min. Following stabilization, the surgery proceeded as planned, lasting approximately three hours without any further intraoperative complications.

The patient was intubated in the intensive care unit (ICU) for continued dantrolene infusion and cooling measures. After 24 h, she was extubated once her vital signs remained stable. The dantrolene infusion was discontinued after 24 h, when the patient maintained normothermia, stable cardiovascular and respiratory parameters, and normalized metabolic markers without recurrence of symptoms, consistent with current MH treatment guidelines. No evidence of acute kidney injury or rhabdomyolysis was observed. A postoperative anteroposterior radiograph confirmed effective correction of the coronal deformity with well-aligned instrumentation (Figure 4). She was transferred to the spinal surgery ward on postoperative day 3 and discharged home on postoperative day 7 with stable vital signs. At the 2-week and 1-month follow-up, the patient demonstrated normal neurological and respiratory function with no recurrence of symptoms. The lateral postoperative view further confirmed the restoration of sagittal plane alignment (Figure 5). Genetic testing for MH susceptibility was recommended but declined. In vitro contracture testing (IVCT), particularly the caffeine-halothane contracture test, was also considered as a diagnostic tool but was not pursued due to its unavailability in our region and its invasive nature. Additionally, the favorable clinical response to dantrolene and the absence of recurrence reduced the urgency for further functional testing. This is consistent with current practices where genetic testing is often prioritized over IVCT when logistical constraints exist.

Mutations in the RYR1 gene, which encodes the ryanodine receptor, are a common cause of MH (5). These mutations lead to dysregulated calcium release from the sarcoplasmic reticulum, triggering uncontrolled muscle contraction and hypermetabolic responses under anesthetic exposure (6). Patients with neuromuscular scoliosis, particularly those with cerebral palsy, central core disease, or multiminicore disease, have a higher likelihood of RYR1 mutations, which predispose them to MH (7). While preoperative genetic screening is not routine, this case underscores its potential value in identifying high-risk patients, as undiagnosed MH susceptibility can lead to severe intraoperative complications (8).

Unlike the findings of Su et al. (9) and Alderson et al. (10), who reported no MH cases in their 3-year study of 400 pediatric scoliosis patients, our case demonstrates that MH can still occur in neuromuscular scoliosis patients, particularly when exposed to volatile anesthetics (9). This discrepancy underscores the importance of patient-specific risk assessments rather than relying solely on general epidemiological trends. Additionally, studies such as Rosenberg et al. (1) found that 17% of neuromuscular scoliosis patients tested positive for MH susceptibility, compared to only 1% of non-scoliotic patients, reinforcing the higher risk in this patient population (1, 11). Research by Rendu et al. (12) and Riazi et al. (13) suggest that abnormal calcium regulation in skeletal muscle cells may explain the increased vulnerability to MH in patients with neuromuscular disorders, further supporting the need for enhanced perioperative monitoring in scoliosis surgeries (13). This case aligns with previous reports where RYR1 mutations were implicated in patients with neuromuscular conditions who developed MH despite no prior known susceptibility (13). Although neither genetic testing nor in IVCT was performed, the diagnosis of MH in this case was made based on clinical criteria. The patient exhibited hallmark signs of malignant hyperthermia (MH), including a sudden rise in end-tidal CO₂ (60 mmHg), hyperthermia (41°C), generalized muscle rigidity, severe metabolic acidosis, elevated creatine kinase (CK) levels, and myoglobinuria, all of which occurred intraoperatively after exposure to a known trigger (sevoflurane). Using the Clinical Grading Scale (CGS) proposed by Larach et al. (14), the calculated score exceeded the threshold for a rank of “almost certain,” strengthening diagnostic confidence. Differential diagnoses such as muscular dystrophy, neuroleptic malignant syndrome, and isolated rhabdomyolysis were considered but ruled out based on clinical context, medication history, and the specific timing and constellation of symptoms. The rapid response to dantrolene further supported MH as the most plausible diagnosis.

To enhance patient safety and minimize the risk of MH in neuromuscular scoliosis patients undergoing general anesthesia, we propose several key recommendations. Preoperative MH screening should be considered for all patients with neuromuscular scoliosis, particularly those undergoing major surgical procedures under general anesthesia, to assess potential susceptibility and mitigate intraoperative risks. When selecting anesthetic agents, non-triggering options such as propofol and dexmedetomidine should be prioritized over volatile anesthetics and succinylcholine, both of which are known MH triggers and can significantly increase the likelihood of a hypermetabolic crisis. Additionally, anesthetic teams must have dantrolene readily available at all times and be trained in rapid MH response protocols, ensuring immediate and effective intervention in the event of a suspected reaction. Proper preparation, awareness, and protocol adherence are critical in improving patient outcomes and preventing life-threatening complications in high-risk populations.

Preoperative risk assessment should include a detailed family and anesthetic history, paying special attention to previous unexplained anesthetic events or known neuromuscular diagnoses. High-risk patients include those with congenital myopathies (central core disease), confirmed or suspected RYR1 mutations, or prior intraoperative complications suggestive of MH. Genetic testing should be pursued when available. Although caffeine-halothane contracture testing is considered definitive, it remains largely inaccessible in many countries, including Saudi Arabia, where clinical evaluation and genetic screening are used to guide risk stratification.

In response to this case, our institution has revised anesthetic protocols for patients with neuromuscular scoliosis and cerebral palsy. Inhaled anesthetics and succinylcholine are now avoided, and total intravenous anesthesia using agents such as propofol and dexmedetomidine is the standard of care. This policy change reflects evolving best practices and aligns with literature supporting non-triggering anesthetic strategies in MH-susceptible populations. The diagnostic and therapeutic approach adopted in this case is consistent with current expert guidelines (15). The European Malignant Hyperthermia Group (EMHG, 2020) and the Malignant Hyperthermia Association of the United States (MHAUS, 2023) recommend prompt recognition based on clinical signs, discontinuation of triggering agents, administration of dantrolene, active cooling, and supportive care as the first-line treatment (1). Our reliance on the Clinical Grading Scale to support diagnosis aligns with its validated use in malignant hyperthermia assessment, particularly when confirmatory genetic or contracture testing is unavailable. These recommendations are also reflected in recent literature reviews and international expert consensus Cong et al. (16), which emphasize vigilance in high-risk populations, preparedness with dantrolene, and the avoidance of volatile anesthetics and depolarizing neuromuscular blockers in susceptible individuals.