Four-site distal paravertebral blocks improve physiologic indicators of analgesia in the immediate postoperative period as opposed to a 3-site distal paravertebral block.

Objective: To determine differences in surgical and postoperative analgesia between 3-site distal paravertebral (DPV) blocks and modified 4-site DPV blocks.

Methods: 12 healthy dairy or dairy cross steers were randomized into 1 of 2 treatments, 3-site DPV block (3DPV) or 4-site DPV block (4DPV); 2 mg/kg of 2% lidocaine was administered at each site-lumbar vertebrae 1, 2, and 4 in the 3DPV group (6 mg/kg), and an additional injection at lumbar vertebrae 3 for the 4DPV group (8 mg/kg). Heart and respiratory rates, temperature, reaction scores, and surgical condition scores were collected. Postoperative pain scores and physiologic data were collected for 24 hours following surgery. An ordinal logistic mixed-effects model was used to compare surgical conditions, reaction scores, and pain scores. A linear mixed-effects model was used for normally distributed data.

Results: The success rate of 3DPV blockade was 5 of 6 (83%), and that for 4DPV was 6 of 6 (100%). Only 11 steers were included in the data analysis due to the failed block. The 4DPV group had lower respiratory rates following the return to stall (32 ± 3 vs 44 ± 4 breaths/min; P < .019). Additionally, the 4DPV group had significantly lower heart rates immediately following the return to the stall (62 ± 8 vs 88 ± 9 beats/min; P < .036). No differences in pain scores or intraoperative conditions were identified.

Conclusions: Adding an injection site at L3 in a DPV reduced postoperative heart rate and respiratory rate in steers following laparotomy.

Clinical relevance: Adding a fourth injection site at L3 decreases physiologic indicators of postoperative discomfort.