Use of Continuous Wound Infusion of Bupivacaine for Analgesia Following Axillary Clearance Surgery

Does Continuous Wound Infusion of 0.2% Bupivacaine Provide Superior Analgesia Compared to Standard Opioid-based Therapy in Patients Following Axillary Clearance Surgery?

Axillary clearance forms part of the surgical armamentarium for the treatment of breast cancer. Although the introduction of sentinel lymph node mapping and dissection has allowed for the decreased use of axillary clearance, it remains a frequently performed operation. Axillary clearance is associated with moderate postoperative pain.

We hypothesize that a continuous wound infusion of 0.2% Bupivacaine at 4ml/hr would provide superior analgesia, when compared to standard opioid-based analgesia, in patients undergoing axillary lymph node clearance surgery.

The study will take the form of a prospective randomised clinical trial. The following assessment tools will be used

• The visual analogue scale (VAS) consists of a 100 mm horizontal line with the two end points labelled "no pain" and "worst pain ever". Patients are asked to mark on the line a point that corresponds to the level of pain intensity they feel. The score is obtained by measuring the distance (mm) from the left end of the line.
• The short-form McGill Pain Questionnaire (SF-MPQ) consists of 15 representative words from the sensory and affective categories of the standard McGill Pain Questionnaire. It also includes the present pain intensity and a VAS to provide overall indices of pain intensity. It has been shown to be sensitive to clinical changes brought about by various interventions, postoperative analgesic drugs (6).
• The Pain Catastrophising Score (PCS) is a 13 item instrument which asks patient to reflect on past painful experiences, and to indicate the degree to which they experienced each of these 13 thoughts or feelings, on 5-point scales with the end points; 0 = not at all, 4 = all the time. The PCS yields a total score and three subscale scores assessing rumination, magnification and helplessness (7).
• The Hospital Anxiety and Depression Score (HADS) is a 14-item scale, which screens for these, the two most common disturbances encountered in a medical setting (8).

Inclusion Criteria:

• Patients undergoing axillary clearance surgery
• ASA physical status I - III

Exclusion Criteria:

• Patient refusal
• Pre-existing pain conditions
• Regular use of opioid analgesia
• Pregnancy
• Severe cardiac, renal or hepatic disease
• Psychiatric illness precluding ability to give informed consent
• Intercurrent neurological disease
• Contraindications to bupivacaine or morphine use