Prediction of post-operative pain by an electrical pain stimulus
ABSTRACT Treatment of post-operative pain is still a significant problem. Recently, interest has focused on pre-operative identification of patients who may experience severe post-operative pain in order to offer a more aggressive analgesic treatment. The nociceptive stimulation methods have included heat injury and pressure algometry. A simple method, Pain Matcher (PM), using electrical stimulation, is validated for pain assessment, but has not been evaluated as a tool for prediction of post-operative pain. Our aim was to assess the predictive value of pre-caesarean section pain threshold on intensity of post-caesarean section pain using the PM.
Thirty-nine healthy women scheduled for elective caesarean section were studied. The anaesthetic/analgesic procedures included spinal anaesthesia, paracetamol, diclofenac, controlled-release (CR) oxycodone and morphine on request. Pre-operatively, the sensory and pain thresholds were measured using the PM. Post-operatively, a midwife, blinded for pre-caesarean pain threshold assessments, assessed the pain at rest and during mobilization every 12 h for 2 days. Consumption of analgesics was also recorded.
Pre-operative pain threshold correlated significantly with post-caesarean pain score (VAS) at rest and mobilization: [Spearman's rho =-0.65 (-0.30 to -0.75), P < 0.01] and [Spearman's rho =-0.52 (-0.23 to -0.72), P < 0.01], respectively. There was no significant correlation between pre-operative PM assessment of sensory threshold and post-operative pain.
Electrical pain threshold before caesarean section seems to predict the intensity of post-operative pain. This method may be used as a screening tool to identify patients at high risk of post-operative pain.
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ABSTRACT: The role of quantitative sensory testing (QST) in prediction of analgesic effect in humans is scarcely investigated. This updated review assesses the effectiveness in predicting analgesic effects in healthy volunteers, surgical patients and patients with chronic pain. A systematic review of English written, peer-reviewed articles was conducted using PubMed and Embase (1980-2013). Additional studies were identified by chain searching. Search terms included 'quantitative sensory testing', 'sensory testing' and 'analgesics'. Studies on the relationship between QST and response to analgesic treatment in human adults were included. Appraisal of the methodological quality of the included studies was based on evaluative criteria for prognostic studies. Fourteen studies (including 720 individuals) met the inclusion criteria. Significant correlations were observed between responses to analgesics and several QST parameters including (1) heat pain threshold in experimental human pain, (2) electrical and heat pain thresholds, pressure pain tolerance and suprathreshold heat pain in surgical patients, and (3) electrical and heat pain threshold and conditioned pain modulation in patients with chronic pain. Heterogeneity among studies was observed especially with regard to application of QST and type and use of analgesics. Although promising, the current evidence is not sufficiently robust to recommend the use of any specific QST parameter in predicting analgesic response. Future studies should focus on a range of different experimental pain modalities rather than a single static pain stimulation paradigm.European journal of pain (London, England) 10/2013; 17(9). DOI:10.1002/j.1532-2149.2013.00330.x · 3.22 Impact Factor
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ABSTRACT: Although humans differ widely in how sensitive they are to painful stimuli, the neural correlates underlying such variability remains poorly understood. A better understanding of this is important given that baseline pain sensitivity scores relate closely to the risk of developing refractory, chronic pain. To address this, we used a matched perception paradigm which allowed us to control for individual variations in subjective experience. By measuring subjective pain, nociceptive flexion reflexes, and, somatosensory evoked brain potentials (with source localization analysis), we were able to map the brain's sequential response to pain while also investigating its relationship to pain sensitivity (i.e. change in the stimulation strength necessary to experience pain) and spinal cord activity. We found that pain sensitivity in healthy adults was closely tied to pain-evoked responses in the contralateral precuneus. Importantly, the precuneus did not contribute to the actual representation of pain in the brain, suggesting that pain sensitivity and pain representation depend on separate neuronal sub-systems.Brain Topography 05/2013; DOI:10.1007/s10548-013-0291-0 · 2.52 Impact Factor
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ABSTRACT: Surgery-induced neuroplasticity at spinal and supra-spinal levels is assumed to evoke a clinical acute post-operative pain (cAPOP) experience, which is expressed by allodynia and/or hyperalgesia. It remains unclear whether the systemic pain perception measured outside the incision area remains unchanged and whether it is affected by the presence of cAPOP. This study explored whether the systemic perception of experimental pain would be altered towards hypersensitivity following elective gynecological surgery unmasked by opioids. A perioperative psychophysical evaluation of heat pain thresholds (HPT) and pain estimations were obtained in a remote bodily area before and after surgery among 35 women. The ratings for both pain dimensions of intensity and unpleasantness remained stable following surgery. However, there was a reduction found in HPT the day after surgery (43.6 ± 2.2 °C to 42.2 ± 3.1 °C, p = 0.002). This reduction was associated with lower HPT measured before surgery (r = .56, p < 0.000) and with higher cAPOP intensity obtained at rest (r = -.44, p = 0.008). This post-surgical allodynia, as reflected by the systemic enhancement of pain perception, may represent plasticity in the central pain pathways at the supra-spinal level. Pre-surgical assessment of a patient's pain perception profile may predict certain pain dimensions of post-surgical pain plasticity. The evaluation of individual pain profiles may contribute to a mechanism-based approach aimed to attenuate the cAPOP.European journal of pain (London, England) 02/2012; 16(2):247-55. DOI:10.1016/j.ejpain.2011.07.003 · 3.22 Impact Factor