Author: Michael Vlessides
Ultrasound-guided rectus sheath block proves superior to field block with respect to perioperative pain control and stress response in patients undergoing midline hernia repair, new research has concluded. The team of Egyptian investigators behind the trial stressed that ultrasound guidance reduces the risk for accidental bowel puncture when performing the technique.
According to Mohammed S. Hassan, MSc, a research assistant at the Theodor Bilharz Research Institute, in Giza, Egypt, the rectus sheath block has been shown to provide effective pain relief for midline surgical incisions by blocking the intercostal nerves. “Although the rectus sheath block carries the risk of puncturing the posterior rectus sheath, peritoneum and bowel, the use of ultrasound technology has reduced this risk considerably,” he said.
To determine the block’s effectiveness, Hassan and his colleagues enrolled 75 ASA physical status I and II patients into the trial presenting at the institute between August and December 2017, all of whom were undergoing midline hernia repair. All surgical procedures were done by the same surgical team; patients underwent a standardized general anesthetic regimen.
The participants were randomly assigned to one of three groups:
The investigators measured the visual analog scale (VAS) immediately after surgery was completed, as well as two, four and six hours postoperatively. The time to first analgesia requirement also was measured, as well as 24-hour morphine consumption. Cortisol and catecholamine levels were measured 30 minutes preoperatively, one hour after induction of general anesthesia, and at two and six hours postoperatively.
Superior Hemodynamics Among the Benefits
Hassan reported that significantly lower VAS scores were observed in patients receiving the rectus sheath block than in either of the two other groups in the PACU, as well as at two, four and six hours after surgery (P<0.05).
The rectus sheath block group also lasted a significantly longer time before first analgesia (232.0±148.0 minutes) than patients in the field block group (39.2±54.0 minutes) and controls (31.2±28.0 minutes; P<0.05). Similarly, 24-hour postoperative morphine consumption was 6.0±4.3 mg in the rectus sheath block group, 16.0±5.7 mg in the field block group, and 17.6±3.8 mg among controls (P<0.05).
“With respect to supplemental intraoperative fentanyl, we saw that the rectus sheath block group had a lower incidence,” Hassan explained. “Only two of the 25 patients required additional intraoperative fentanyl, compared to 16 patients in the field block group.”
The researchers also examined intraoperative hemodynamic parameters among the three groups, finding that patients un dergoing the rectus sheath block enjoyed a superior hemodynamic profile compared with their counterparts in the other two groups. “We saw that in the rectus sheath block group, all patients demonstrated a reduction in heart rate compared to the other two groups, both of which showed a significant increase in heart rate.” Systolic blood pressure values were lower in the rectus sheath block group than either of the other two groups.
Serum cortisol and catecholamine levels also were found to be lower among rectus sheath block patients than in the other two groups at one hour after induction of anesthesia, as well as two and six hours postoperatively.
“I think it’s quite impressive to perform a blinded, prospective, randomized controlled trial on this topic,” said session co-moderator Angela Selzer, MD, an assistant professor of anesthesiology at the University of Colorado School of Medicine, in Denver. “I’m curious why you chose to study serum cortisol and catecholamine levels. Why are we interested in looking at that? And why do you think those levels actually went down in the rectus sheath block group?”
“To our knowledge, few studies have looked at these parameters,” Hassan replied. “There’s been only one other study that examined hormonal response with rectus sheath block [BMC Anesthesiol 2018;18(1):19], but it only looked at cytokines, not catecholamines or cortisol.”
“I was a little surprised to see that the field block didn’t seem to make much of a difference relative to your control group,” Dr. Selzer noted.
“We found that local infiltration was better than placebo, but only marginally,” Hassan said. “Nevertheless, the field block can be helpful in certain patient populations, such as those in whom the rectus sheath block is contraindicated.
“We conclude that in patients undergoing midline hernia repair, ultrasound-guided rectus sheath block provides excellent intraoperative analgesia and cardiovascular stability, suppression of catecholamine and cortisol response to surgical trauma, excellent and prolonged postoperative analgesia, and reduced postoperative narcotic requirements,” he said.