Severe pain during local infiltration for spinal anaesthesia predicts post-caesarean pain

Quantitative sensory testing (QST) measures response to painful stimuli and has been used to predict post-caesarean pain. Pain reported upon intravenous cannulation was shown to predict epidural analgesic use and pain intensity during labour. We hypothesized that pain intensity reported by women upon local anaesthesia injection (ILA) for spinal anaesthesia may predict acute pain after caesarean delivery (CD).

In a prospective observational trial, 229 women undergoing elective CD under spinal anaesthesia were enrolled. Using standardized script before ILA, women received ILA (lidocaine 1% 2.5 mL via 25 G needle), and provided an ILA score after the injection [verbal numeric pain scale (VNPS); 0-100]. Demographic data, average, peak pain (at rest, with movement and uterine cramping) and analgesic requests were recorded for the first 24 h.

Fourteen percent of women experienced severe pain (VNPS ≥70) upon ILA. Good correlation was noted between ILA and pain scores at rest and upon mobilization during the 24 h following surgery (average resting pain r = 0.529, p < 0.001, average pain at mobilization r = 0.483, p < 0.0001). Severe acute postoperative pain (VNPS ≥70) was predicted by severe ILA pain with a sensitivity of 91.6% and specificity of 93.3%.

This is the first study evaluating a clinical measure to predict post-caesarean pain. Our main findings were that 14% of women experience severe pain upon ILA, which was associated with increased pain during the first 24 h.