Postoperative Analgesic Effect of Bilateral Quadratus Lumborum Block (QLB) for Canine Laparoscopic Ovariectomy: Comparison of Two Concentrations of Ropivacaine

SIMPLE SUMMARY: Laparoscopic ovariectomy is currently considered the gold standard for neutering female dogs thanks to the reduced surgical trauma, lower perioperative pain, and decreased hospitalization stays.

Perioperative analgesic management becomes crucial to reduce the occurrence of uncontrolled post-surgery stress response.

The quadratus lumborum block is an ultrasound-guided block capable of providing somatic and visceral analgesia to the abdomen.

The aims of this study were (I) to evaluate the efficacy of the transversal quadratus lumborum block performed with two different concentrations of ropivacaine (0.5% and 0.33%) in prolonging the time to the first postoperative rescue analgesia in dogs undergoing laparoscopic ovariectomy, in comparison with a fentanyl-based protocol, and (II) to investigate the cardiovascular impact of the block on the arterial blood pressure.

The results of this study showed a significantly longer time to the first postoperative rescue analgesia in groups receiving the block, in comparison with the group receiving a fentanyl-based protocol.

Surprisingly, ropivacaine 0.33% produce a more important reduction in the arterial blood pressure than ropivacaine 0.5%.

Further studies are needed to better assess the intraoperative efficacy of the quadratus lumborum block.

ABSTRACT: The aim of this study was to evaluate the effect of the transverse quadratus lumborum block (QLB(LQL-T)) on time to the first postoperative rescue analgesia in dogs submitted to laparoscopic ovariectomy.

A total of twenty-three female dogs were included.

Dogs were randomly assigned to receive a bilateral QLB(LQL-T), performed either with 0.3 mL kg(−1) ropivacaine 0.5% [group QLB(0.5%) (n = 8)] or with ropivacaine 0.33% [group QLB(0.33%) (n = 8)] or a fentanyl-based protocol [group No-QLB (n = 7)].

Dogs were premedicated intravenously (IV) with fentanyl 5 mcg kg(−1), general anesthesia was induced IV with propofol and maintained with sevoflurane.

Invasive mean arterial pressure (MAP) values were recorded five minutes before and five minutes after performing the QLB(LQL-T).

The short-form of the Glasgow composite measure pain scale was used every hour after extubation, and methadone 0.2 mg kg(−1) was administered IV when pain score was ≥5/24.

Kolmogorov–Smirnov test, ANOVA test combined with Tukey post hoc test, Student’s T-test and Chi-square test were used to analyze data; p < 0.05.

Time from QLB(LQL-T) to the first rescue analgesia was significantly longer in QLB(0.5%) than in group QLB(0.33%) and No-QLB.

MAP pre- and post-block decreased significantly only in group QLB(0.33%).