Failed spinal anesthesia tied to cold temperature.
Failed spinal anesthesia can have significant clinical consequences, possibly necessitating redosing, conversion to general anesthesia, or pain during surgery.
"Efforts to identify and reduce the incidence of failed neuraxial anesthesia are of utmost importance, considering the increased use of these techniques in obstetric cases," Dr. Manuel C. Vallejo Jr. said at the meeting.
The 14 cases, spanning an 8-week period, were all associated with three particular lots of unexpired BD spinal anesthesia trays. The cases were all under the care of experienced staff anesthesiologists and were associated with standardized neuraxial technique using hyperbaric bupivacaine 12 mg (0.75% with dextrose 8.25%) plus 20 mcg fentanyl plus 0.2 mg Duramorph (morphine). A 25-gauge Whitacre needle was used, and the free flow of cerebrospinal fluid was confirmed before and after the intrathecal drug placement, Dr. Vallejo reported.
His team at Magee-Women's Hospital contacted the bupivacaine manufacturer, Hospira Inc.; the spinal kit manufacturer, BD (Becton, Dickinson, and Co.); and the Food and Drug Administration, noting that the clustering of failures suggested problems with concentration/formulation or drug stability. Hospira tested samples from the drug lot and found no formulation or concentration issues.
For its part, BD replied that Hospira's testing showed that "all testing was within specification," and that "we were unable to find the cause of the insufficient anesthesia identified in your report."
The company also said that the drug supplier would "continue to monitor for the complaint condition through normal inspection and sampling procedures."
The negative batch analysis, normal product potency, and unremarkable testing of retained samples by Hospira led Dr. Vallejo and his team to suspect that the problem was related to drug stability issues in transit and/or storage of the spinal kit.
There had been a cold spell starting during the first week of December, during which the temperature was never above freezing, ranging from 15.4[degrees] to 30.9[degrees] F.
The bupivacaine is made in Indianapolis by Hospira and is shipped to BD in New Jersey, where the spinal kits are assembled. The suspect kits had been shipped to a warehouse in Pittsburgh, loaded onto a nonenvironmentally controlled truck in the evening, and unloaded at Magee the following morning, thus having been stored for more than 9 hours at temperatures below freezing before delivery, Dr. Vallejo said.
A mass spectrometric analysis done at the University of Pittsburgh demonstrated that there had been chemical alteration of the bupivacaine involved. The suspect sample had a molecular mass to charge ratio of 276, compared with 289 for normal bupivacaine.
As a temporary solution, a separate bupivacaine ampule was affixed to the suspect spinal kits, and temperature indicator strips were used.
All 14 of the women and newborns were fine with no long-term problems, he noted.
BD now directly drop ships the packaged spinal kits to Magee-Women's. These measures have dramatically decreased but not eliminated the rate of failed spinal anesthetics, Dr. Vallejo commented, adding that other factors may also contribute, including technical failure, inadequate patient position, inadvertent subdural or epidural injection, inadequate intrathecal dose, and "rachi-resistance," a phenomenon described in 1934 in which patients are "hyperresistant" to spinal anesthesia, possibly because of insensitive nerve roots.
"I think it's multifactorial, but we definitely showed a chemical alteration," he noted.
During the question and answer period, an audience member from Toronto said that approximately 400 cases of failed spinal anesthesia had been reported in the province of Ontario in October 2009 and were also suspected to be a result of cold temperature exposure.
"There's definitely a problem," Dr. Vallejo replied.
Asked to comment specifically for this story, BD replied in part: "Patient safety and quality of our products are BD's foremost priorities. The causes of failed regional anesthesia are multifactorial and an industrywide phenomenon. They are typically not associated with any single manufacturer's product.
"Evaluations of our complaint records do not show a correlation between the shipment of product during cold or hot months and complaint rates. The rate remains stable across the year.
"We are conducting a more extensive, controlled study to evaluate this hypothesis. When this investigation is completed, BD will take all actions deemed necessary and appropriate by the study, if any."
Major Finding: Fourteen cases of failed spinal anesthesia were attributed to chemical alteration from cold temperature exposure.
Data Source: Experience at Magee-Women's Hospital, Pittsburgh.
Disclosures: None was reported.
BY MIRIAM E. TUCKER
FROM THE ANNUAL MEETING OF THE SOCIETY FOR OBSTETRIC ANESTHESIA AND PERINATOLOGY