Anesthesiologists searching for a simple alternative to the paravertebral block in breast surgery patients might consider a technique adopted by researchers at the University of Ottawa, in Ontario. Their two-step surgical field block proved comparable to the paravertebral block in all measured outcomes in the early postoperative period and in the setting of chronic postsurgical pain.
“There’s quite a bit of literature suggesting that paravertebral blocks are superior to traditional opioid analgesic techniques in breast cancer surgery patients,” said Shachar Ben-Zeev MD, a fellow in regional anesthesia at the University of Ottawa. “But we noticed that a lot of the literature that supports this notion is really limited, most importantly by the fact that there’s no active comparator. And we thought we’d look at the impact of paravertebral blocks compared with what we call a two-step surgical field block, which is essentially wound infiltration with local anesthetic by the surgeons combined with instillation of local anesthetic into the surgical drain.”
Dr. Ben-Zeev and his colleagues conducted a secondary analysis of data that had been previously collected for a published randomized, double-blind trial (Ann Surg Oncol 2014;21:795-801). In that trial, women undergoing surgery for breast cancer were randomly assigned to receive the paravertebral or surgical field block.
Patients in the paravertebral block group had a T1-T6 paravertebral block with 5 mL of 0.5% ropivacaine per level; saline was injected by the surgeon into the wound and into the drain. Those in the surgical field block group received subcutaneous saline injections at T1-T6, with 10 mL of 0.5% ropivacaine injected by the surgeon into the wound and 20 mL into the surgical drain.
“We then analyzed these data looking at the quality of recovery score, predominantly on day 2, because we felt that this was a good reflection of the patients’ postoperative function,” Dr. Ben-Zeev explained. “We also looked at the proportion of patients with pain greater than 3 [on the Numeric Rating Scale (NRS)] on postoperative day 2. And the third thing we looked at was the shoulder and arm disability, by measuring something called the Constant score, which is a validated 100-point metric used by orthopedic surgeons looking at things like activities of daily living, pain, range of motion and power.”
As Dr. Ben-Zeev reported at the 2016 annual meeting of the Canadian Anesthesiologists’ Society (abstract 146364), of the 129 patients recruited, 65 were assigned to the paravertebral block and 64 to the surgical field block; the groups were demographically similar. Results showed the groups were similar in all measured outcomes, including quality of recovery on postoperative day 2 (paravertebral, 18 vs. surgical field block, 17; P=0.83), proportion of patients with NRS pain levels greater than 3 on postoperative day 2 (paravertebral, 16.4% vs. surgical field block, 14.1%; P=0.81) (Figure 1) and Constant score (paravertebral, 75 vs. surgical field block, 69; P=0.68).
Furthermore, the differences in quality of recovery and NRS pain scores were not significant in repeated measures analysis (P=0.76 and P=0.25, respectively).
The investigators pointed out that this is the first adequately blinded randomized trial to compare the effect of paravertebral block with an active comparator on recovery, pain and function after breast cancer surgery. “We hypothesize that a possible reason for the divergence of our results from previous results out there is that the two-step surgical block may represent a slightly higher standard of care for breast cancer surgery patients than is usually done,” Dr. Ben-Zeev explained.
“That would also fit in with the fact that our measured incidence of chronic pain in patients in both groups—less than 10%—was significantly lower than the average that you see reported in the literature, which is between 25% and 60%. This also begs the question whether our study wasn’t adequately powered to detect a real difference. With such a low incidence, this is a possibility,” he said.
“In any event,” he added, “the conclusion to draw is that when performing a paravertebral block in similar patient populations, you should certainly carefully weigh the risks and benefits of the block. It’s an invasive procedure with potential complications and some question of benefit.”
Jacques E. Chelly, MD, PhD, MBA, congratulated the investigators for what he called a “well-designed clinical study on a relatively significant number of patients. Although it seems that both techniques yielded similar outcomes, I hope the final article will also include analgesic consumption along with the time required for the surgeons to perform these blocks,” he said. “One of the advantages of performing paravertebral blocks is that they can be done before the transfer of the patient to the OR.”
Dr. Chelly, who is professor of anesthesiology and orthopedic surgery at the University of Pittsburgh Medical Center, was quick to point out that evidence supports the notion that a paravertebral block may delay cancer recurrence. “Since the proposed technique is performed after rather than before surgery, it would be interesting to know if similar beneficial benefits can be claimed with the two-step surgical field block.”
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