Sabine Ahlers

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

BackgroundPain 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.MethodsWe 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).ResultsInter-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 ≥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).ConclusionThe different scales show a high reliability, but observer-based evaluation often underestimates the pain, particularly in the case of high NRS values (≥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 patients 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.

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.

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.

Morphine Glucuronidation and Elimination in Intensive Care Patients: A Comparison with Healthy Volunteers.

BACKGROUND:Although morphine is used frequently to treat pain in the intensive care unit, its pharmacokinetics has not been adequately quantified in critically ill patients. We evaluated the glucuronidation and elimination clearance of morphine in intensive care patients compared with healthy volunteers based on the morphine and morphine-3-glucuronide (M3G) concentrations. METHODS:A population pharmacokinetic model with covariate analysis was developed with the nonlinear mixed-effects modeling software (NONMEM 7.3). The analysis included 3012 morphine and M3G concentrations from 135 intensive care patients (117 cardiothoracic surgery patients and 18 critically ill patients), who received continuous morphine infusions adapted to individual pain levels, and 622 morphine and M3G concentrations from a previously published study of 20 healthy volunteers, who received an IV bolus of morphine followed by a 1-hour infusion. RESULTS:For morphine, a 3-compartment model best described the data, whereas for M3G, a 1-compartment model fits best. In intensive care patients with a normal creatinine concentration, a decrease of 76% was estimated in M3G clearance compared with healthy subjects, conditional on the M3G volume of distribution being the same in intensive care patients and healthy volunteers. Furthermore, serum creatinine concentration was identified as a covariate for both elimination clearance of M3G in intensive care patients and unchanged morphine clearance in all patients and healthy volunteers. CONCLUSIONS:Under the assumptions in the model, M3G elimination was significantly decreased in intensive care patients when compared with healthy volunteers, which resulted in substantially increased M3G concentrations. Increased M3G levels were even more pronounced in patients with increased serum creatinine levels. Model-based simulations show that, because of the reduction in morphine clearance in intensive care patients with renal failure, a 33% reduction in the maintenance dose would result in morphine serum concentrations equal to those in healthy volunteers and intensive care patients with normal renal function, although M3G concentrations remain increased. Future pharmacodynamic investigations are needed to identify target concentrations in this population, after which final dosing recommendations can be made.

Is intraoperative remifentanil associated with acute or chronic postoperative pain after prolonged surgery? An update of the literature

Objective:Remifentanil is an ultra-short-acting opioid that is used commonly during both short-term and prolonged surgery. This review investigated associations of intraoperative remifentanil administration with acute postoperative pain, hyperalgesia, and chronic postoperative pain, with emphasis on the perioperative coanesthetic drug regimen used. Methods:Medline and Embase databases were searched for randomized studies, evaluating the intraoperative use of remifentanil (>2 h) versus another analgesic or a different dosage of remifentanil, and reporting acute postoperative pain parameters such as postoperative pain scores, hyperalgesia, acute opioid tolerance, or analgesics requirements. Furthermore, all studies in which remifentanil was used intraoperatively and parameters for chronic postoperative pain were measured were included (pain levels after a prolonged period of time after surgery). Results:From the 21 studies that were identified, less than half of the studies found higher acute postoperative pain, higher postoperative analgesic requirements after intraoperative remifentanil use, or both. Coanesthetics to some extent determined this incidence, with mainly studies using volatile agents reporting increased pain levels. There was less evidence when remifentanil was combined with total intravenous anesthesia or a combination of anesthetics. The limited number of studies (n=4) evaluating chronic pain suggested a potential association with the intraoperative use of remifentanil. Discussion:Although studies are diverse and sample sizes small, coanesthetics used in combination with remifentanil may influence the occurrence of postoperative hyperalgesia. No firm conclusions could be made regarding acute and chronic pain, indicating that further research with the goal to investigate the effect of volatile or intravenous anesthetics along with simultaneous remifentanil infusion on acute and chronic postoperative pain is needed.

Adherence to all steps of a pain management protocol in intensive care patients after cardiac surgery is hard to achieve

Purpose. To investigate adherence to our pain protocol considering analgesics administration, number and timing of pain assessments, and adjustment of analgesics upon unacceptably high (NRS ≥ 4) and low (NRS ≤ 1) pain scores. Material and Methods. The pain protocol for patients in the intensive care unit (ICU) after cardiac surgery consisted of automated prescriptions for paracetamol and morphine, automated reminders for pain assessments, a flowchart to guide interventions upon high and low pain scores, and reassessments after unacceptable pain. Results. Paracetamol and morphine were prescribed in all 124 patients. Morphine infusion was stopped earlier than protocolized in 40 patients (32%). During the median stay of 47 hours [IQR 26 to 74 hours], 702/706 (99%) scheduled pain assessments and 218 extra pain scores were recorded. Unacceptably high pain scores accounted for 96/920 (10%) and low pain scores for 546/920 (59%) of all assessments. Upon unacceptable pain additional morphine was administered in 65% (62/96) and reassessment took place in 15% (14/96). Morphine was not tapered in 273 of 303 (90%) eligible cases of low pain scores. Conclusions. Adherence to automated prescribed analgesics and pain assessments was good. Adherence to nonscheduled, flowchart-guided interventions was poor. Improving adherence may refine pain management and reduce side effects.

Randomized Controlled Trial on the Influence of Intraoperative Remifentanil versus Fentanyl on Acute and Chronic Pain after Cardiac Surgery

Remifentanil has been associated with increased acute and potentially chronic postoperative pain. The objective of this prospective randomized controlled trial was to investigate the influence of intraoperative remifentanil on acute and chronic postoperative pain after cardiac surgery.