Percutaneous nephrolithotomy to remove large kidney stones may be minimally invasive, but the pain that typically follows is anything but minimal. According to a recent study, however, the use of a paravertebral block could be an effective strategy for pain reduction in patients undergoing this procedure.
In the first randomized, double-blind, placebo-controlled trial investigating the use of paravertebral block prior to percutaneous nephrolithotomy, patients receiving the block showed improved pain scores and decreased use of opioids. Patients randomly assigned to paravertebral block also had lower rates of antiemetic use, which is a surrogate for nausea and vomiting. Although the power analysis called for twice the number of patients, the study was terminated early due to the significant results, the authors reported.
“Intraoperative opioid use, postoperative opioid use, frequency of opioid use and antiemetic use were significantly lower in the paravertebral block group as compared to the control group,” said Scott Byram, MD, associate professor of anesthesiology and medical director of the acute pain service at Loyola University Medical Center, in Maywood, Ill. “Based on these results, we found paravertebral block to be a very effective means of pain control for patients undergoing percutaneous nephrolithotomy, and we now offer this block to all patients having this surgery.”
As Dr. Byram reported at the 2017 annual meeting of the American Society of Regional Anesthesia and Pain Medicine (abstract 3292), percutaneous nephrolithotomy is considered the gold-standard minimally invasive treatment for large stone burdens, but postoperative pain control remains a challenge. Furthermore, although paravertebral block has been described for breast and thoracic surgery as an effective pain control approach, it is rarely used for percutaneous nephrolithotomy (Br J Anaesth 2010;105:842-852).
“These patients tend to have quite a bit of pain after surgery and have a high need for opioids, which can lead to opioid-related side effects,” Dr. Byram said. “The objective of this study was to evaluate whether paravertebral block following percutaneous nephrolithotomy would affect pain control and opioid use.”
In this study, patients at Loyola University Medical Center undergoing unilateral percutaneous nephrolithotomy for stone disease were randomly assigned to receive either paravertebral block or placebo intervention in the preoperative area. After sedating the patient with midazolam, an attending anesthesiologist on the acute pain service, the only group of practitioners unblinded in the study, performed the paravertebral block or placebo.
Figure. Intraoperative and recovery room fentanyl use.
PVB, paravertebral block
As Dr. Byram reported, the paravertebral block consisted of a single injection of 20 mL of 0.5% bupivacaine with epinephrine into the T10 paravertebral space under ultrasound guidance. For the patients in the placebo group, an ultrasound probe was applied and a subcutaneous lidocaine injection was administered, along with pressure, to mimic injection. Patients were then taken to the operating room and a standard general anesthetic was administered by a separate anesthesia team that was blinded (along with the surgeon and patient) as to study group. Patients received patient-controlled analgesia (PCA) following surgery.
The 45 patients enrolled in the study had no difference in baseline characteristics, and no complications were attributed to the paravertebral block, the authors said. Although average visual analog scale (VAS) pain scores were similar over the first 24 hours, according to Dr. Byram, the paravertebral group experienced statistically significantly less pain.
“It’s not that surprising that these patients had similar VAS scores because they had access to morphine PCA and could titrate to similar levels of pain,” he said. “What’s more impressive, however, is the amount of fentanyl that was used both intraoperatively and in recovery.”
According to Dr. Byram, the paravertebral block patient group used significantly less fentanyl in the operating room and recovery room than the control group (Figure). Total morphine use also decreased in the first 24 hours along with frequency of PCA demand in the paravertebral block group, and time to first analgesic administration was significantly longer in the paravertebral block group as well. Finally, antiemetic use was significantly lower in the paravertebral group than the control group (Table).
|Table. Postoperative Analgesic and Antiemetic Use Over 24 Hours|
|PVB Group||Control Group||P Value|
|Total IV morphine equivalents dose (mg)||17.5||31.1||0.02|
|Frequency of PCA demand (n)||14.4||26.9||0.004|
|Time to first analgesic administration (min)||119.7||31.9||0.006|
|Rate of supplemental oral narcotic use (%)||30.4||61.9||<0.001|
|Rate of antiemetic use (%)||30.4||52.4||<0.001|
|PCA, patient-controlled analgesia; PVB, paravertebral block.|
“The reduction in opioid use likely leads to improved nausea, as reflected in the decreased use of antiemetics,” Dr. Byram said.
Joseph Neal, MD, an anesthesiologist at Virginia Mason Medical Center, in Seattle, said the study has the potential to be practice changing, but he expressed concerns regarding its early termination.
“We had a planned interim analysis, which is why we stopped at 45 patients,” Dr. Byram said. “After analyzing our data and seeing its significance, we decided not to subject 40 more patients to placebo when paravertebral block had clearly demonstrated superior pain control. Ethically, we decided it was best to stop.”
“The only really significant difference in your VAS scores was 24 hours after surgery,” Dr. Neal said. “How do you explain that?”
“The VAS scores early on may have been affected by the relatively large doses of opioids given in the PACU, which lasted into the early postoperative period,” Dr. Byram said. “Perhaps once the patients were transferred to the floor, they couldn’t safely be given as much opioids, and only then did the groups show a difference.”