Author: Michael Vlessides
Anesthesiology News
Current data do not strongly support the use of programmed intermittent bolus (PIB) technology in peripheral nerve blocks, a review from Mayo Clinic has concluded. Nevertheless, the investigators found that current literature shows advantages for the PIB technique in blocks with circumferential spread and compartment blocks in the early postoperative period, particularly for lower extremity blockade.
“As we know, local anesthetic infusion with peripheral nerve blockade is a mainstay of postoperative analgesia,” said Ram Jagannathan, MD, a fellow in anesthesiology at the Rochester, Minn., institution. “Programmed intermittent bolus is a relatively new infusion technique that is reported in anatomic studies to provide more uniform spread of local anesthetic solution in the epidural space. This was recently corroborated in a Cochrane analysis involving epidural labor analgesia, expressing higher block level, better patient satisfaction and lower demand dose.”
Despite the promising findings, the benefit of PIB in peripheral nerve blockade is far more unclear, as studies have largely demonstrated conflicting results. With that in mind, the investigators sought to summarize the existing knowledge comparing intermittent bolus techniques—which allow a set volume of solution to be administered as a bolus at a set interval—with conventional continuous infusion.
The search yielded 15 publications, of which three focused on nonsurgical patients. The remaining 12 studies were randomized controlled trials comparing a PIB technique and standard continuous infusion for postoperative analgesia at different peripheral nerve block sites.
Of these 12 studies, eight involved lower extremity blockade, two involved upper extremity blockade, one involved truncal blockade and one involved paravertebral blockade. Primary outcome variables in the majority of the studies included an assessment of pain or opioid use. Other variables were consumption of local anesthetic, patient satisfaction and functional outcomes. Except for a single publication from 1997, all of the reviewed studies were published between 2008 and 2017.
“We found that six studies showed some form of statistical significance favoring PIB technique in regard to pain scores, with two showing a transient decrease in one variable analyzed and four demonstrating a decrease in pain scores throughout the analysis,” Dr. Jagannathan reported at the 2018 Joint World Congress on Regional Anesthesia and Pain Medicine and annual meeting of the American Society of Regional Anesthesia and Pain Medicine (abstract 4812).
“We found that there could be some advantage of PIB in lower extremity blockade, usually before 48 hours, if statistical significance does indeed correlate with clinical significance, particularly with the use of pain scores,” Dr. Jagannathan said. “However, some of these studies quoted a [visual analog scale] difference of 1.5 to 2.0 as statistically significant. It remains to be seen whether this is clinically significant.”
The researchers concluded that PIB cannot be strongly recommended for peripheral nerve block. Future studies should focus on determining the advantages of PIB on a block-by-block basis to determine optimal bolus frequencies, they said.
“Because the data are heterogeneous, it was very difficult to synthesize the material and actually say that that programmed intermittent bolus could be routinely recommended,” he concluded. “In the future, variation in infusion delivery should not only focus on pain metrics, but also opiate sparing and differences in functional and adverse outcomes. PIB should also be studied in surgical cohorts where multimodal strategies do not routinely control pain.”
“Your meta-analysis included one study of truncal blockade and one paravertebral blockade, both of which have higher local anesthetic volumes,” said session moderator Jaime Baratta, MD, a clinical assistant professor of anesthesiology at Thomas Jefferson University, in Philadelphia. “Would your hypothesis have been that those groups would have shown the greatest benefit of PIB?”
“I think so,” Dr. Jagannathan replied. “Blocks based on compartmental spread—like the TAP block, paravertebral block and even the distal brachial plexus block—where you need spread in order to get a successful block, may all benefit from future research with PIB.”
“You may see more PIB studies now that the technology has improved, with new pumps being able to ask questions of patients, communicate with providers and address how we tailor therapy to each patient,” Dr. Baratta said. “This may make PIB more relevant and more important in the future. And once we start getting information from some of the more high-tech pumps, it could be easier to figure out optimal timing and dose.”