The role of peripheral afferents in persistent inguinal postherniorrhaphy pain: a randomized, double-blind, placebo-controlled, crossover trial of ultrasound-guided tender point blockade.

BACKGROUND: Severe, persistent inguinal postherniorrhaphy pain (PIPP) is a debilitating condition that develops in 2-5% of patients. PIPP may be neuropathic in nature, yet the lesion in the peripheral nervous system has not been located. Most PIPP-patients demonstrate a tender point (TP) in the medial aspect of the inguinal region that triggers pain upon minimal pressure. As TPs may play a role in the pathophysiology of PIPP, the aim of this trial was to investigate the analgesic effects of local anaesthetic TP-blockade. METHODS: A randomized, double-blind, placebo-controlled, crossover trial was performed in 14 PIPP-patients and six healthy volunteers. All participated in two sessions, seven days apart, receiving 10 ml of 0.25% bupivacaine or normal saline via an ultrasound-guided fascial plane block at the TP. The TP-area was used for pain assessments (at rest, on movement, with 100 kPa pressure-algometry) and quantitative sensory testing (pressure pain thresholds, thermal detection/pain thresholds, supra-threshold heat perception), before and after the TP-blockade. RESULTS: The median (95% CI) reduction in pain was 63% (44.1 to 73.6%) after bupivacaine compared with 36% (11.6 to 49.7%; P=0.003) after placebo. Significant increases in cool detection (P=0.01) and pressure pain thresholds (P=0.009) with decreases in supra-threshold heat pain perception (P=0.003) were seen after bupivacaine only. In four out of six volunteers, increased thermal and evoked-pain thresholds after bupivacaine compared with placebo, was demonstrated. CONCLUSIONS: This trial demonstrates that peripheral afferent input from the TP-area is important for maintenance of spontaneous and evoked pain in PIPP. CLINICAL TRIAL REGISTRATION: NCT02065219.

Evaluation of point-of-care haemoglobin measuring devices: a comparison of Radical-7™ pulse co-oximetry, HemoCue(®) and laboratory haemoglobin measurements in obstetric patients*.

We prospectively compared two point-of-care haemoglobin concentration measuring devices with laboratory measurements to determine their accuracy in women undergoing caesarean section delivery. The two devices were the Masimo Rainbow SET(®) Radical -7™ pulse co-oximeter and the HemoCue(®) HB 201+, which is a cuvette-type system that uses photometry. Co-oximeter readings and HemoCue measurements were taken before and after surgery, and compared with laboratory measurements of haemoglobin concentration taken at the same time. We analysed data from 137 patients using Bland-Altman plots. Limits of agreement for co-oximeter readings were -2.19 to 3.41 g.dl(-1) and for the HemoCue were -1.52 to 1.79 g.dl(-1) . The bias (mean difference) for the co-oximeter was -0.61 g.dl(-1) (95% CI 0.36 to -0.86) and for the HemoCue was 0.13 g.dl(-1) (95% CI -0.015 to 0.28). [corrected] Overall, 110/274 (40%) co-oximeter readings were within 1 g.dl(-1) of laboratory values compared with 247/274 (90%) HemoCue measurements (p < 0.001 for difference). The co-oximeter gave lower readings and was less accurate than the HemoCue system when compared with laboratory measurements.