The study, “A retrospective cohort study of children with spinal muscular atrophy type 2 receiving anesthesia for intrathecal administration of nusinersen,” was published in the journal Pediatric Anesthesia.
SMA is caused by mutations in the SMN1 gene, which provides instructions to make the survival motor neuron (SMN) protein — essential for motor nerve cells and muscle function. SMA is classified into five categories based on age of onset and severity.
Children with type 2 SMA typically have the first symptoms between 7 and 18 months of age and develop a so-called “intermediate SMA.” They may sit without support, but most of them won’t be able to stand or walk independently.
Spinraza, developed by Biogen, is currently the only approved treatment for all SMA types in the U.S., Europe, Canada, and Japan. It takes advantage of the existence of a second survival motor neuron gene (SMN2), boosting its ability to produce a functional SMN protein and restoring its normal levels.
Spinraza is currently administered through an injection into the cerebrospinal fluid (the fluid in the spine) — a procedure called an intrathecal injection — every two months initially, followed by every four months throughout a patient’s life.
Since it must be administered intrathecally, general anesthesia may be used for some children younger than 12, because they may not be able to lie still during the brief injection.
Researchers at the Children’s Hospital Colorado at the University of Colorado School of Medicine retrospectively evaluated the safety and effectiveness of standard anesthesia for Spinraza administration in children with type 2 SMA.
They reviewed clinical data of eight children (five girls and three boys) who underwent 61 anesthetics at the Children’s Hospital Colorado, within the CHERISH (NCT02292537) and SHINE (NCT02594124) clinical trials, between May 2015 and August 2017.
The randomized, placebo-controlled Phase 3 CHERISH trial evaluated the safety and effectiveness of Spinraza in children with SMA type 2, and the SHINE study — an ongoing Phase 3 open-label trial — is investigating Spinraza’s long-term safety and effectiveness in SMA patients who participated in previous Spinraza trials (including the CHERISH study). All patients enrolled in the SHINE study are being given the treatment.
Patients had a mean age of 4.1 years and received a median of eight anesthetic procedures to receive either Spinraza or a placebo.
Induction of anesthesia was performed with Ultane (sevoflurane), nitrous oxide, and oxygen (30%) via facemask, and maintained by administering Diprivan (propofol) directly into the blood in 58 of the cases and vapor anesthetics in the remaining three cases. Of these anesthesia procedures, 83% were performed by anesthesiologists.
Researchers found that general anesthesia was safe and effective, with no major anesthesia-related complications, and no deaths. No patient had major changes in their breathing rate and oxygen saturation or needed mechanical ventilation after the procedure. In addition, no interaction between the anesthetic agents and Spinraza was observed.
Two patients were reported to have been hospitalized during this time period, both due to lung-related conditions, which caused no permanent damage and were not associated with the delivery of anesthesia.
The team also noted that these findings may not be generalized to patients with other types of SMA, and that they did not assess the occurrence of muscle pain, fever, headaches, nausea, vomiting, or the levels of sugar in the blood.
“Nusinersen has revolutionized the care of patients with spinal muscular atrophy type 2 and anesthesiologists will be involved in its administration. We found that routine anesthetic care was safe and effective,” the researchers wrote.
However, additional and larger studies are required to clarify these results, and whether these findings “can be extrapolated to patients with SMA types 1 and 3 remains unknown,” they said.