Case Series Gives Insight Into Surgical Intervention for SMA Patients with Severe Scoliosis

Patients with spinal muscular atrophy (SMA), an autosomal recessive neuromuscular disorder, often develop severe kyphoscoliosis as the disease progresses. Severe scoliosis can be addressed with surgery to avoid further worsening, but SMA patients face a high risk of complications with surgery. A recent case series provided insight into the preoperative considerations, anesthesia protocol, and postoperative recovery of patients with SMA and severe scoliosis.

The retrospective study assessed medical records from 79 patients with SMA (34 with type 2; 45 with type 3) who were considered for scoliosis surgery between 2007 and 2019 at a referral center specializing in this type of surgery and patient group. Each patient was evaluated by a senior orthopedic spine surgeon, physiotherapist, and anesthesiologists to assess the surgical options and anesthetic risks in their individual cases.

The clinical manifestations of SMA include impaired lung function, progressive muscle weakness, and difficulty swallowing. Therefore, an airway assessment, standard spirometry, and chest radiography were key aspects of the preoperative assessment. The results were then discussed with patients and legal guardians for patients who were minors. Potential risks and benefits were presented, using findings related to physical status, spirometry, spinal or ribcage range of motion, possible lung compression, and anticipated respiratory complications during recovery from surgery.

Of the 79 patients considered for surgery, 62 received clearance for surgery and anesthesia. One patient had anesthesia clearance revoked after suffering from pneumonia and aftereffects during the 5 months she was waiting for surgery, and 6 patients did not show up for surgery for unknown reasons. In total, the analysis includes 56 patients who were cleared and went through surgery. Those who were not cleared for surgery (n = 17) were either cleared for anesthesia but only had minor scoliosis (n= 3) or already had a very rigid spine (n = 1); or were not cleared for anesthesia due to a range of grave findings mostly related to respiratory concerns in the preoperative assessment (n = 13).

Patients who underwent surgery had a mean forced vital capacity (FVC) of 1.41 L in 1 second and forced expiratory volume (FEV) of 1.26 L in one second. Mean FVC and FEV in the patients who were not cleared for surgery were 0.65 L and 0.55 L, respectively. There is no current standard for cutoff values in SMA patients specifically, but greater than 1 L was preferred and at least .5 L was required. This finding alone could not determine surgical eligibility, but rather was integrated with other clinical findings. Patients were also instructed to practice exercises including breathing and coughing preoperatively with the main goal of forgoing intensive respiratory support after surgery.

“Considering that all 56 patients could be extubated in the operating room on average 14 min after wound closure and that no reintubation was needed indicates that we succeeded rather well as regards patient selection and weaning off the anesthetics, opioids, and muscle relaxants,” the authors wrote.

Despite often demanding intubations, direct laryngoscopy (DLS) was uneventful in 28 of 32 patients in which it was attempted. Fiberoptic intubation (FOI) resolved all 4 of the unsuccessful DLS attempts. FOI was used as the primary technique in 10 cases, all of which were successful. AirTraq was used as the primary method in 3 patients and presented difficulties due to the device’s bulkiness. Video laryngoscopy (VLS)was attempted as a primary method in 11 cases and successful in 10, with the remaining patient successfully intubated via FOI as a backup method. Where intubation is concerned, the authors cautioned that an anesthesiologist should be experienced and that visualization of the glottis should be expected to be challenging.

Postoperatively, weak coughing and mucus production were common, and 4 patients were diagnosed with pneumonia. The findings were largely in line with other studies, the authors reported. In the early postoperative days, 25 patients required potassium supplementation due to hypokalemia. While hypokalemia can have may causes, the authors noted that this finding is novel to the current review, to their knowledge.

Limited long-term outcome data and evolving anesthesia techniques over the decade were limitations of the study, as was the single-center and retrospective nature of the analysis. But overall, most patients were pleased with the results of their surgeries at follow-up. The findings provide additional data in a patient population lacking studies due to the disease’s rarity.

“It adds insight into the preoperative clearance process, the intraoperative anesthetic techniques applied (including details on airway management) and some of the postoperative complications,” the authors concluded.

Reference

Förster JG, Schlenzka D, Österman H, and Pitkänen M. Anaesthetic considerations in posterior instrumentation of scoliosis due to spinal muscular atrophy: case series of 56 operated patients. Acta Anaesthesiol Scand. Published online December 6, 2021. doi:10.1111/aas.14011