Prediction of post-operative pain by an electrical pain stimulus

IT University of Copenhagen, København, Capital Region, Denmark
Acta Anaesthesiologica Scandinavica (Impact Factor: 2.32). 05/2007; 51(5):582-6. DOI: 10.1111/j.1399-6576.2007.01271.x
Source: PubMed


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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    • "Sample size of the included studies ranged from 20 to 162. A priori, studies were divided according to study population; (1) healthy volunteers (Eisenberg et al., 2010), (2) surgical patients (Wilder-Smith et al., 2003; Hsu et al., 2005; Pan et al., 2006; Martinez et al., 2007; Nielsen et al., 2007; Aasvang et al., 2008; Rudin et al., 2008; Buhagiar et al., 2011; Pedersen et al., 2013), and (3) patients with chronic pain (Attal et al., 2004; Edwards et al., 2006; Yarnitsky et al., 2012; Olesen et al., 2013). "
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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 · 2.93 Impact Factor
    • "Numerous experimental stimulation models for testing pain sensitivity have been studied, with the goal of predicting acute post-surgical pain.[234567891011] Electrical pain threshold appears to have superior predictive power, compared with thermal and mechanical assessment.[12] "
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    ABSTRACT: Experimental assessments can determine pain threshold and tolerance, which mirror sensitivity to pain. This, in turn, influences the post-operative experience. The study intended to evaluate whether the pre-operative pressure and electrical pain tests can predict pain and opioid requirement following cesarean delivery. Research was conducted on females scheduled for cesarean section at a tertiary care hospital of the state. Twenty women were enrolled, after obtaining written informed consent. PAIN ASSESSMENT WAS PERFORMED ON THE EVE OF CESAREAN SECTIONS USING THREE DEVICES: PainMatcher(;) determined electrical pain threshold while the algometers PainTest(™) FPN100 (manual) and PainTest(™) FPX 25 (digital) evaluated pressure pain threshold and tolerance. Post-operative pain relief included intravenous morphine administered by patient-controlled analgesia, diclofenac (100 mg, every 12 h, rectally, enforced) and paracetamol (1000 mg, every 4-6 h, orally, on patient request). Pain scores were reported on numerical rating scales at specified time intervals. Correlational and regression statistics were computed using IBM SPSS Statistics 21 software (IBM Corporation, USA). A SIGNIFICANT CORRELATION WAS OBSERVED BETWEEN MORPHINE REQUIREMENT AND: (1) electrical pain threshold (r = -0.45, P = 0.025), (2) pressure pain threshold (r = -0.41 P = 0.036) and (3) pressure pain tolerance (r = -0.44, P = 0.026) measured by the digital algometer. The parsimonious regression model for morphine requirement consisted of electrical pain threshold (r(2)= 0.20, P = 0.049). The dose of morphine consumed within 48 h of surgery decreases by 0.9 mg for every unit increment in electrical pain threshold. The predictive power of pain sensitivity assessments, particularly electrical pain threshold, may portend post-cesarean outcomes, including opioid requirements.
    Journal of Anaesthesiology Clinical Pharmacology 10/2013; 29(4):465-71. DOI:10.4103/0970-9185.119135
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    • "Thus, the existence of cortical region(s) relating specifically to the transition form a non-painful to a painful state remains unexplored (see, however, Baliki et al. 2009; Zhang et al. 2012; Schulz et al. 2012; Coghill et al. 2003 for evidence of cerebral regions tied to individual differences in suprathreshold pain perception). Further understanding of this is important, especially if we consider that individual differences in baseline pain sensitivity predict individual differences in the development of refractory chronic pain (Hsu et al. 2005; Strulov et al. 2007; Nielsen et al. 2007; and also see Granot 2009 for a review). The close link between pre-operative pain threshold values and the probability of developing post-operative chronic pain constitutes a provocative example (Pan et al. 2006). "
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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; 27(3). DOI:10.1007/s10548-013-0291-0 · 3.47 Impact Factor
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