Åsa Rudin

Prediction of postoperative pain: a systematic review of predictive experimental pain studies.

Quantitative testing of a patients basal pain perception before surgery has the potential to be of clinical value if it can accurately predict the magnitude of pain and requirement of analgesics after surgery. This review includes 14 studies that have investigated the correlation between preoperative responses to experimental pain stimuli and clinical postoperative pain and demonstrates that the preoperative pain tests may predict 4–54% of the variance in postoperative pain experience depending on the stimulation methods and the test paradigm used. The predictive strength is much higher than previously reported for single factor analyses of demographics and psychologic factors. In addition, some of these studies indicate that an increase in preoperative pain sensitivity is associated with a high probability of development of sustained postsurgical pain.

Pain relief and safety after major surgery A prospective study of epidural and intravenous analgesia in 2696 patients.

Background:  Adverse effects may still limit the use of continuous epidural and intravenous analgesia in surgical wards. This study postulated that postoperative epidural analgesia was more efficient, and had fewer side‐effects than intravenous morphine. The aim was to investigate efficacy, adverse effects and safety of the treatments in a large patient population.

Prediction of post-operative pain after a laparoscopic tubal ligation procedure.

Background: Pre‐operative identification of reliable predictors of post‐operative pain may lead to improved pain management strategies. We investigated the correlation between pre‐operative pain, psychometric variables, response to heat stimuli and post‐operative pain following a laparoscopic tubal ligation procedure.

Morphine Metabolism After Major Liver Surgery

BACKGROUND:Impaired metabolism of morphine may lead to an increase in sedation and respiratory depression. METHODS:In the present study we investigated morphine pharmacokinetics in patients who had undergone liver resection (n = 15) compared to a control group undergoing colon resection (n = 15). Morphine was administered IV by patient-controlled analgesia. Plasma concentrations of morphine, morphine-6-glucuronide, and morphine-3-glucuronide were measured 2–3 times daily for the first two postoperative days. Pain intensity scores were assessed three times daily and respiratory rate and sedation scores every third hour. RESULTS:There were no differences in morphine requirements 1.1 (0.8–2.5 [median, interquartile range]) mg/h (liver resection) and 1.5 (1.1–1.7) mg/h (colon resection) [P = 0.84]) or in pain intensity scores (P > 0.3) between the groups. Plasma morphine concentrations were higher in patients undergoing liver resection than in the control group (P < 0.01) reflecting a lower rate of morphine metabolism. Plasma morphine concentrations were correlated with the volume of liver resection (P < 0.02). However, plasma concentrations of morphine-6-glucuronide and morphine-3-glucuronide did not differ between the groups (P = 0.62 and P = 0.48, respectively). There was a higher incidence of sedation (P = 0.02), but not respiratory depression (P = 0.48), after liver resection. CONCLUSION:The study demonstrates that plasma concentrations of morphine are higher in patients undergoing liver resection compared with patients undergoing colon resection. Sedation scores were higher in patients undergoing liver resection. Caution is therefore recommended when administering morphine to this patient group.

Could benefits of epidural analgesia following oesophagectomy be measured by perceived perioperative patient workload

Background: A controversy exists whether beneficial analgesic effects of epidural analgesia over intravenous analgesia influence the rate of post‐operative complications and the length of hospital stay. There is some evidence that favours epidural analgesia following major surgery in high‐risk patients. However, there is a controversy as to whether epidural analgesia reduces the intensive care resources following major surgery. In this study, we aimed at comparing the post‐operative costs of intensive care in patients receiving epidural or intravenous analgesia.

Pain following surgery: management, outcome, and prediction

Despite advances in the treatment of postoperative pain, nearly 30% of patients experience moderate to severe pain following major surgery. The present thesis includes four studies intended to evaluate important aspects of postoperative pain. In studies I and II, patient-controlled epidural analgesia (PCEA, n = 1,670), using local anesthetics and morphine, was associated with significantly lower pain ratings than intravenous patient-controlled analgesia (PCA, n = 1,026) using morphine following major surgery. Respiratory depression, sedation, confusion, hallucinations, and nightmares were more frequently observed in the PCA group, while technical difficulties leading to insufficient analgesia were more frequent in the PCEA group. In study III, morphine pharmacokinetics were studied in patients undergoing major liver resection (n = 15) in comparison with a group undergoing colon surgery (n = 15). Liver resection was associated with higher plasma concentrations of morphine indicating a decrease in morphine clearance, compared to controls. Sedation scores were higher in patients undergoing liver resection than in controls. In study IV, the predictive potential of psychometric variables and preoperative responses to experimental heat stimuli were evaluated in patients scheduled for a laparoscopic sterilization procedure (n = 59). Pre-surgical pain and preoperative heat pain sensitivity were important predictors of postoperative pain, while psychometric estimates of vulnerability, anxiety, and depression only contributed to a lesser degree. The prediction model accounted for 29-43% of the total variance in postoperative movement-related pain. Optimum pain management requires careful consideration regarding surgical procedure, analgesic technique, pharmacokinetics, and risk factors in the development of postoperative pain. (Less)