The Val158Met polymorphism of the COMT gene is associated with increased pain sensitivity in morphine-treated patients undergoing a painful procedure after cardiac surgery.

AIMS: The catechol-O-methyltransferase (COMT) Val158Met polymorphism affected pain sensitivity of healthy volunteers upon application of experimental pain stimuli. The relevance of these findings in morphine-treated postoperative cardiac patients undergoing painful healthcare procedures is unknown; therefore, the aim of this study was to investigate whether the COMT Val158Met polymorphism increases pain sensitivity in morphine-treated patients undergoing an unavoidable painful routine procedure after cardiac surgery. METHODS: One hundred and seventeen postoperative cardiac patients in the intensive care unit were genotyped for the COMT Val158Met polymorphism. All patients were treated with continuous morphine infusions for pain at rest, and received a bolus of morphine (2.5 or 7.5 mg) before a painful procedure (turning and/or chest drain removal) on the first postoperative day. Numerical rating scale (NRS) scores were evaluated at the following four time points: at baseline (at rest), and before, during and after the painful procedure. RESULTS: Overall mean NRS scores were significantly higher in patients carrying the Met-variant allele. During the painful procedure, the mean NRS score was significantly higher for Met/Met patients compared with Val/Met and Val/Val patients (mean NRS 3.4 ± 2.8, 2.7 ± 2.4 and 1.7 ± 1.7, respectively; P = 0.04). In Met/Met patients, the increase in NRS scores during the painful procedure compared with the baseline NRS score was clinically relevant (ΔNRS ≥ 1.3) and statistically significant and appeared to be independent of sex and the morphine bolus dose. CONCLUSIONS: Our results show that the COMT Val158Met polymorphism contributes to variability in pain sensitivity after cardiac surgery of morphine-treated patients in the intensive care unit, because Met-allele carriers were more sensitive to overall pain and procedure-related pain.

Risk factors for chronic thoracic pain after cardiac surgery via sternotomy.

OBJECTIVE: This study examines the influence of patient demographics and peri- and postoperative (<7 days) characteristics on the incidence of chronic thoracic pain 1 year after cardiac surgery. The impact of chronic thoracic pain on daily life is also documented. METHODS: A prospective cohort study of 146 patients admitted to the intensive care unit after cardiac surgery via sternotomy was carried out. Pain scores (numeric rating scale 0-10) were recorded during the first 7 postoperative days. One year later, a questionnaire was used to evaluate the incidence in the 2 preceding weeks of chronic thoracic pain (numeric rating scale >0) associated with the primary surgery. RESULTS: One year after surgery, 42 (35%) of the 120 responding patients reported chronic thoracic pain. Multivariate regression analysis of patient characteristics revealed that non-elective surgery, re-sternotomy, severe pain (numeric rating scale ≥ 4) on the third postoperative day, and female gender were all independent predictors of chronic thoracic pain. In addition, the chronic sufferers reported more sleep disturbances and more frequent use of analgesics than their cohorts. CONCLUSIONS: We have identified a number of factors correlated with persistent thoracic pain following cardiac surgery with sternotomy. Awareness of these predictors may be useful for further research concerning both the prevention and treatment of chronic thoracic pain, thereby potentially ameliorating the postoperative quality of life of a significant proportion of patients. Meanwhile, chronic thoracic pain should be discussed preoperatively with patients at risk so that they are truly informed about possible consequences of the surgery.

Improved analgesia after the realisation of a pain management programme in ICU patients after cardiac surgery.

BACKGROUND AND OBJECTIVE: Although clinical guidelines recommend systematic evaluation of pain in ICU patients, we know little about the effects from such systematic pain evaluation. This study aims to quantify the effect of a pain management programme in the ICU. METHODS: In this prospective two-phase study, pain levels scored by ICU patients after cardiac surgery through sternotomy were compared before and after the implementation of a pain management programme. The pain management programme consisted of a three-fold strategy; all staff was trained in assessing pain and in providing adequate analgesia, a new patient data management system obliged nurses to ask patients for their pain score three times a day and the preferred analgesic treatment was optimised. The numeric rating scale (NRS 0-10) was used by 190 patients. A NRS at least 4 was considered unacceptable. A generalised linear mixed-effects model was used for analysing repeated measurements data. RESULTS: The occurrence of unacceptable pain (NRS > or = 4) was significantly lower in the intervention group [odds ratio 2.54 (95% confidence interval 1.22-5.65; P = 0.01) for the control group]. Patients in the intervention group received significantly more morphine (29.3 vs. 22.6 mg a day, P<0.01), with higher morphine amounts administered to patients with higher NRS scores (P = 0.01). In the control group, no such relationship was observed (P = 0.66). There was no difference in length of stay in the ICU or in ventilation time. CONCLUSION: The intervention programme successfully reduced the occurrence of unacceptable pain. Further improvement of pain management should focus on the prevention of pain.

Comparison of different pain scoring systems in critically ill patients in a general ICU.

BACKGROUND: Pain in critically ill patients in the intensive care unit (ICU) is common. However, pain assessment in critically ill patients often is complicated because these patients are unable to communicate effectively. Therefore, we designed a study (a) to determine the inter-rater reliability of the Numerical Rating Scale (NRS) and the Behavioral Pain Scale (BPS), (b) to compare pain scores of different observers and the patient, and (c) to compare NRS, BPS, and the Visual Analog Scale (VAS) for measuring pain in patients in the ICU. METHODS: We performed a prospective observational study in 113 non-paralyzed critically ill patients. The attending nurses, two researchers, and the patient (when possible) obtained 371 independent observation series of NRS, BPS, and VAS. Data analyses were performed on the sample size of patients (n = 113). RESULTS: Inter-rater reliability of the NRS and BPS proved to be adequate (kappa = 0.71 and 0.67, respectively). The level of agreement within one scale point between NRS rated by the patient and NRS scored by attending nurses was 73%. However, high patient scores (NRS > or = 4) were underestimated by nurses (patients 33% versus nurses 18%). In responsive patients, a high correlation between NRS and VAS was found (rs = 0.84, P < 0.001). In ventilated patients, a moderate positive correlation was found between the NRS and the BPS (rs = 0.55, P < 0.001). However, whereas 6% of the observations were NRS of greater than or equal to 4, BPS scores were all very low (median 3.0, range 3.0 to 5.0). CONCLUSION: The different scales show a high reliability, but observer-based evaluation often underestimates the pain, particularly in the case of high NRS values (> or = 4) rated by the patient. Therefore, whenever this is possible, ICU patients should rate their pain. In unresponsive patients, primarily the attending nurse involved in daily care should score the patient's pain. In ventilated patients, the BPS should be used only in conjunction with the NRS nurse to measure pain levels in the absence of painful stimuli.