Superior hypogastric plexus nerve block in minimally-invasive gynaecology: a double-blind randomised controlled trial
Clinical trial to evaluate the efficacy of a superior hypogastric plexus nerve block with 10ml 0.75% ropivacaine in reducing opiate requirements in the first 24 hours after minimally invasive gynaecological surgery. This was a double-blind RCT at a single institution. Primary outcome was the total opiate use in first 24h after surgery (mag of fentanyl). Secondary outcome was patient pain measured on a visual analogue scale (1 to 10) at 1, 2, 6, 12 and 24-hours post-surgery.. Patients were randomised over a 5-month period, March to July 2020. 27 patients were randomised to receive a nerve block and 23 to the control. There were no significant demographic or intraoperative differences between the two groups. Opiate use followed a non-parametric distribution. A 40% median opiate reduction was seen in patients randomised to the nerve block (p=0.02). Pain scores were significantly lower in the nerve-block group compared with no-block group at 1 hour and 12 hours. Mean pain scores were 2.67 vs 4.00 at 1 hour (p=0.035) and 1.07 vs 2.09 (p=0.033) at 12 hours respectively.
Steps to reproduce
Recruitment included patients who were undergoing either laparoscopic hysterectomy, laparoscopic myomectomy, robotic-assisted hysterectomy or robotic-assisted myomectomy. These were the most common benign gynaecological surgeries being performed in our unit. Patients needed to be over the age of 18 years and able to give informed consent. Exclusion criteria were known malignancy, liver failure, long-term opiate medication use (to avoid opiate tolerance confounding), allergy to local anaesthetic and anaesthetic concerns on patient using patient-controlled analgesia (PCA) post-operatively. Total opiate used for the 24h was summarized in micrograms (mcg) of fentanyl. This was calculated by adding up the total volume of Fentanyl PCA used during the 24h period. If the PCA was able to be discontinued prior to 24h enteral opiate doses of tapentadol were included in our calculation of total use. We used Visual Analogue Scale (VAS) scores as a marker of a patient’s pain. This was a well-studied marker of pain scores in research (11). VAS scores were taken by nursing staff at intervals of 1h, 2h, 4h, 6h, 12h and 24h post operatively. A VAS form was attached to the notes of all patients participating in the trial with a pictorial Likert scale for patients to refer to. The SHPB consisted of 10ml 0.75% Ropivacaine injected to the retroperitoneal area where the SHP lies. The landmark to determine area of infiltration was the peritoneum overlying the sacral promontory at the level of L5/S1. Two laparoscopic/robotic instruments were used to grasp the peritoneum and tent it up. A third instrument inserted a fine needle (interject) in the sub-peritoneal space (see figure 1). Infiltration then took place ensuring a large bleb of fluid appeared under the peritoneum in the desired site. This block was performed under vision at the end of the operation prior to withdrawal of laparoscopic or robotic instruments. As the patient was anaesthetized and therefore not aware of receiving the block the control arm was no block rather than a placebo injection. Patients underwent stratified-randomisation taking into account what surgery they were having. This was done to ensure similar proportions of the different laparoscopic and robotic operations received the intervention or control. The four stratified groups were laparoscopic hysterectomy, laparoscopic myomectomy, robotic-assisted hysterectomy, robotic-assisted myomectomy.