Thread: Computer program improves neuromuscular blockade quality, safety

Computer program improves neuromuscular blockade quality, safety

MedWire News: Use a computer control program for neuromuscular blockade dosing markedly improves the quality of blockade during surgery and raises postoperative train-of-four ratios, shows a preliminary study.

“We believe that this technology has the potential to greatly enhance patient safety,” say Stephan Schwarz (University of British Columbia, Vancouver, Canada) and colleagues.

The Neuromuscular Blockade Advisory System (NMBAS) is an adaptive computer control program that advises the anesthesiologist on the timing and dose of neuromuscular blockade drugs.

Its recommendations are generated from a model (sixth-order Laguerre model) based on published pharmacokinetic–pharmacodynamic parameters, and are modified by the patient’s electromyographic responses to train-of-four stimulation.

Schwarz and team assessed 60 patients undergoing surgery lasting more than 1.5 hours who were randomly assigned to undergo neuromuscular blockade with or without the NMBAS.

They report in the journal Anesthesia & Analgesia that just eight of 30 patients assigned to the NMBAS had intra-operative events that indicated inadequate neuromuscular blockade, compared with 19 of 30 controls.

Such events included inadequate surgical relaxation, patient motion (as judged by the surgeon), breathing against the ventilator, and bucking or coughing on the ventilator.

Furthermore, the average train-of-four ratio after surgery was 0.59 in the NMBAS group, compared with just 0.14 in the control group.

“Anesthesiologists' compliance on the whole with the NMBAS and its recommendations was high, which provides an indication of the system's overall clinical applicability and utility,” the researchers note.

They observe that the design of the NMBAS can be adapted for control of other patient parameters, such as depth of anesthesia, blood pressure, and dysrhythmias.

“Therefore, the NMBAS’ Laguerre-based adaptive control technology represents a general platform from which to develop other automatic drug delivery systems for the operating room, intensive care unit, or, eventually, ambulatory use,” the team concludes.

Aural canal thermometers poor measure of peri-operative temperature

MedWire News: The widely used infrared aural canal thermometers are inadequate for assessing peri-operative temperatures, warn US researchers.

The American Society of Anesthesiologists is considering adopting maintenance of peri-operative temperature at greater than 36oC as a performance indicator for surgery lasting more than 1 hour.

Jerome Modell and colleagues from the University of Florida College of Medicine in Gainesville tested whether they could meet this standard in 101 patients undergoing anesthesia for just 10 to 20 minutes, to facilitate electroconvulsive therapy.

Before anesthesia, 35 patients had temperatures lower than 36oC, as measured using infrared aural canal thermometers, and 18 had low temperatures on arrival in the postanesthesia care unit.

Overall, temperatures fell during anesthesia in 30 patients, rose in 64, and were unchanged in seven. Pre- and post-anesthesia temperatures did not correlate, the team reports in the journal Anesthesia and Analgesia.

“We did not calibrate our aural measurements against oral measurement instruments because, if these temperature threshold criteria are to be used as a basis for making financial (reimbursement) decisions, we wanted to follow the usual clinical practice at our institution,” say Modell and team.

“Thus, our data provide an important cautionary tale.”

Editorialists Alexander Hannenberg (Tufts University School of Medicine at Newton-Wellesday Hospital, Massachusetts, USA) and Daniel Sessler (The Cleveland Clinic, Ohio, USA) said: “The ‘take home’ message of Modell et al’s study is that reliance on the nearly ubiquitous, but inaccurate, infrared aural canal thermometers has important patient care implications and may soon have financial consequences as well.”

They stressed: “Anesthesiologists and hospitals need to make certain that postoperative temperature is accurately measured. This means using a reliable device, and ensuring that it is used correctly.”

Anesthesiologist shortage may raise cardiac risks of spinal anesthesia

MedWire News: Research from Thailand suggests that increasing the availability of anesthesiologists to perform spinal anesthesia could help prevent related cardiac arrest, which is infrequent but often fatal.

Writing in the journal Anesthesia & Analgesia, Somrat Charuluxananan (Chulalongkorn University, Bangkok) and co-authors explain: “Much of the literature regarding cardiac arrest related to regional anesthesia involves retrospective studies or case reports [and] few prospective surveys assessing a large number of patients have been published.”

To address this issue, the investigators examined the outcomes of spinal anesthesia as part of the Thai Anesthesia Incidents Study, a large, prospective multicenter study of anesthesia procedures carried out in 20 hospitals across Thailand. The analysis included over 40,000 cases of spinal anesthesia carried out over a 12-month period between March 2003 and February 2004.

Overall, only 11 cardiac arrests occurred during spinal anesthesia, translating to an incidence of just 2.73 cases per 10,000 anesthetic procedures. However, cardiac arrest was fatal in all but two of these patients.

Five of the 11 patients who experienced cardiac arrest received spinal anesthesia for cesarean delivery, while the remaining six were undergoing surgery to the lower extremity, Charuluxananan et al report.

Multivariate analysis revealed that longer duration of surgery and shorter stature were significant risk factors for cardiac arrest. The researchers note that the latter relationship may be partly explained by the fact that nine of the 11 patients who experienced cardiac arrest were female.

Importantly, performance of spinal anesthesia by a surgeon rather than a specialist anesthesiologist significantly increased the risk for cardiac arrest (odds ratio=23.5). This finding was of particular interest given that 5% of patients in the registry were anesthetized by surgeons due to a shortage of anesthesiologists.

Based on these results, “increasing the number of anesthesiologists, improving monitoring guidelines for spinal anesthesia and improving the nurse–anesthetist training program may decrease the frequency of arrest and/or improve patient outcome,” the investigators propose.