Mythbusting the PainBuster

How they let them in, I do not know, but I see on the notice board that a rep from the mob that market a local anaesthetic wound instillation device are to host the theatre staff monthly breakfast meeting. The marketers have worked on nursing staff in recent years, presuming they will in turn suggest, or coerce medical staff to use or prescribe their products. This work has contributed to much use of tramadol and IV paracetamol in the perioperative setting.

Local anaesthetics into or under the wounds of caesarean section and abdominal hysterectomy have been quite well studied, but the efficacy of this practice has struggled to show benefit. In its simplest administration, infiltration of bupivacaine (Leung et al, AIC Oct 2000 and Klein et al BJA Feb 2000) into Pfannensteil hysterectomy wounds are ineffective. Leong et al (Aust N Z J Obstet Gynaecol. 2002 Nov) used an elastomeric infusor of 0.5% bupivacaine at 2 mL/hr for 48 hours after hysterectomy without benefit. Ng et al (Anesth Analg. 2002 Jul) found early postoperative effect from peritoneal instillation of bupivacaine. Ng’s patients only receive a modest 10 mg of morphine at the start of surgery. Ali et al (BJA 1998) used a similar technique but found no benefit at all. Even caring surgeons (Ann R Coll Surg Engl. 2007 Apr) infused bupicvacaine into the rectus sheath after laparotomy but, again, without benefit.

The device presented at the meeting, On-Q Pain Management System, was studied by Givens et al (AmJOG, June 2002). It was placed subcutaneously at the end of of elective caesarean section with epidural anaesthesia. A 25 ml load and 4 ml/h of bupivacaine 0.25% reduced morphine consumption but not pain scores. No other analgesia apart from IVPCA morphine was used and whether the morphine sparing improved other outcomes was not presented. I wonder if a multimodal regimen including diclofenac and paracetamol would have swamped the benefit of the LA.


The technique of LA instillation does seem to have merit where the noxious stimulus is more clearly somatic and peripheral: chest wall, hernia, breast, shoulder and axilla surgeries do benefit from the technique. It seems that for abdominal hystercectomy the evidence for benefit is at best equivocal, and for caesarean section it is at best marginal.