Author: Michael Vlessides
Previous research demonstrated the efficacy of the quadratus lumborum block in abdominal surgeries, but a new study has concluded that the block is not effective when used in colorectal surgeries.
Researchers concluded that patients receiving the posterior quadratus lumborum block did not need fewer opioids postoperative ly and actually had higher postoperative pain scores than their counterparts who did not have the block as part of a multimodal analgesic regimen.
“Over the past few years, many abdominal wall blocks have been used to improve postoperative pain following abdominal surgeries. In particular, the quadratus lumborum block seems advantageous over others, because according to previous studies it can last up to 48 hours and offers coverage of dermatomes from T7 to L2. Nevertheless, its effectiveness remains controversial,” Dr. Paquet said.
To help determine the effectiveness of the novel block in this patient population, Dr. Paquet and her colleagues enrolled 62 patients (63% men; average age, 63 years) with ASA physical status I to III into the double-blind, randomized controlled trial.
Patients were excluded from the study if they were chronic opioid users, had an allergy to local anesthetic, weighed less than 45 kg, had a body mass index more than 35 kg/m2, or had cardiac or hepatic dysfunction.
The 31 patients in the quadratus lumborum block group received an ultrasound-guided injection of 20 mL of 0.375% ropivacaine on each side prior to surgery. The controls were given a sham injection.
The study’s primary outcome was 24-hour opioid consumption. Secondary outcomes included opioid administration, pain severity, time to resumption of intestinal transit, postoperative nausea and vomiting, and hospital length of stay.
“Our hypothesis was that the addition of the block would improve postoperative pain and that patients who received the block would use 50% less opioids in the first 24 hours after surgery,” Dr. Paquet explained. “We chose the 50% threshold because that is what we considered clinically significant and could lead to a change in practice.”
Opioid Use Higher in Block Group
As Dr. Paquet reported at the 2019 annual meeting of the Canadian Anesthesiologists’ Society (abstract 628674), patients who received the quadratus lumborum block consumed an average of 100.2 morphine milligram equivalents (MME) in the 24 hours after surgery (95% CI, 68.9-131.5 MME), compared with 88.7 MME among controls (95% CI, 59.3-118.0 MME) (P=0.80). Opioid consumption at various time points is shown in the Table.
|Table. Opioid Consumption at Different Times With and Without Block|
|Time Interval||Quadratus Lumborum Block Patients, MME||Sham Injection Controls, MME||P Value|
|MME, morphine milligram equivalents|
The trial also found that patients who did not receive the block reported lower mean 24-hour postoperative pain scores (3.8; 95% CI, 2.8-4.7) than those given the block (5.7; 95% CI, 4.7-6.6) (P=0.005) at rest, with cough and with deep inspiration. Other outcomes were similar between the groups.
“In addition, there are three types of quadratus lumborum block described, and we don’t know if one is better than the other,” she said. “So it’s possible that we may have had different results with another type of block. But at this point, our results do not support the inclusion of the quadratus lumborum block as the standard of care in colorectal surgical patients.”
“Did you look at the type of incision performed by the surgeon?” asked Pascal Labrecque, MD, an associate clinical professor of anesthesiology and intensive care at Laval University. “You included different types of colorectal surgeries, and they each come with different types of incisions. I know you didn’t have many patients, but it would be interesting if you performed these subgroup analyses to see if that had an impact on the quality of the block.”
“We did collect those data, and the most important was when patients had to be converted to a laparotomy,” Dr. Paquet replied. “There were two patients in the control group that had a laparotomy incision, compared with none in the block group. As for other incisions and procedures, they were all similar after randomization in both groups.”