Comparative study between effect of pre- versus post-incisional transversus abdominis plane block on acute and chronic post-abdominal hysterectomy pain.

BACKGROUND: The prevalence of persistent chronic pain after abdominal hysterectomy is 5-32%. Our objectives were to determine the influence of transversus abdominis plane (TAP) block on the incidence of acute and chronic post-hysterectomy pain and to examine potential associations between time of block administration, either before surgical incision (preemptive) or after end of surgical procedure and its effect.

MATERIALS AND METHODS: Seventy-five patients undergoing elective total abdominal hysterectomy under general anesthesia were allocated randomly to receive TAP block either pre-incisional, or before emergence from anesthesia or sham block (just a needle puncture, control group). Pain was evaluated postoperatively at rest and movement by visual analogue scale. Peri-operative analgesic requirements, sedation, postoperative nausea and vomiting scores were recorded. Patients were questioned at three, and six months after surgery for type and severity of chronic pain.

RESULTS: Pain scores were significantly higher in Group II versus Group I (P<0.05), but both demonstrated significantly lower pain scores than control Group. Analgesic requirements decreased significantly in patients received TAP block (P<0.0001) with more significant decrease in the pre-incisional group. The incidence of chronic pain was significantly reduced in the pre-incisional group than others. The incidence of sedation was noted to be higher in the control group (61%) versus other groups (18% and 32% respectively), at time point 12 h postoperatively but was comparable between 12, 48 h (awake and alert). Incidence of postoperative nausea and vomiting (PONV) was reduced in patients who received TAP block (16% and 29%) in Group I and II respectively versus 66.5% in Group III. There were no complications attributed to the TAP block.

RESULTS: Pain scores were significantly higher in Group II versus Group I (P<0.05), but both demonstrated significantly lower pain scores than control Group. Analgesic requirements decreased significantly in patients received TAP block (P<0.0001) with more significant decrease in the pre-incisional group. The incidence of chronic pain was significantly reduced in the pre-incisional group than others. The incidence of sedation was noted to be higher in the control group (61%) versus other groups (18% and 32% respectively), at time point 12 h postoperatively but was comparable between 12, 48 h (awake and alert). Incidence of postoperative nausea and vomiting (PONV) was reduced in patients who received TAP block (16% and 29%) in Group I and II respectively versus 66.5% in Group III. There were no complications attributed to the TAP block.

CONCLUSIONS: TAP block seems to be an acceptable choice for postoperative analgesia; pre-incisional TAP block appeared to reduce the severity of acute pain, analgesic requirements with its undesirable side-effects and incidence of chronic pain in comparison with blockade before emergence from anesthesia.