M. A. E. Marcus

The prevalence of postoperative pain in a sample of 1490 surgical inpatients

Background and objective: To measure the prevalence of postoperative pain, an assessment was made of 1490 surgical inpatients who were receiving postoperative pain treatment according to an acute pain protocol. Methods: Measurements of pain (scores from 0 to 100 on a visual analogue scale) were obtained three times a day on the day before surgery and on days 0‐4 postoperatively; mean pain intensity scores were calculated. Patients were classified as having no pain (score 0‐5), mild pain (score 6‐40), moderate pain (score 41‐74) or severe pain (score 75‐100). Results: Moderate or severe pain was reported by 41% of the patients on day 0, 30% on days 1 and 19%, 16% and 14% on days 2, 3 and 4. The prevalence of moderate or severe pain in the abdominal surgery group was high on postoperative days 0‐1 (30‐55%). A high prevalence of moderate or severe pain was found during the whole of days 1‐4 in the extremity surgery group (20‐71%) and in the back/spinal surgery group (30‐64%). Conclusion: We conclude that despite an acute pain protocol, postoperative pain treatment was unsatisfactory, especially after intermediate and major surgical procedures on an extremity or on the spine.

Central and Peripheral Analgesia Mediated by the Acetylcholinesterase-Inhibitor Neostigmine in the Rat Inflamed Knee Joint Model

Intrinsic cholinergic inhibitory pathways present a key modulating system in pain perception.The use of intrathecal (IT) acetylcholinesterase-inhibitors, such as neostigmine, result in analgesia in both preclinical and clinical models. However, whether IT neostigmine suppresses tonic persistent pain or has peripheral sites of antinociceptive action has not been determined. Thus, we studied central (IT) and peripheral (intraarticular; IA) neostigmine in a rat inflamed knee joint model. Inhibition of thermal and mechanical hyperalgesia was assessed over 28 h using a modified Hargreaves box and von Frey hairs, respectively. IT neostigmine resulted in a dose-dependent thermal analgesia (50% of maximal effective dose [ED50] 0-4 h: 6.6 [micro sign]g, 24-28 h: 9.4 [micro sign]g) and mechanical analgesia (ED (50) 0-4 h: 3.5 [micro sign]g, 24-28 h: 4.3 [micro sign]g). IT atropine reversed analgesia by IT neostigmine. IA neostigmine also resulted in an IA atropine reversible dose-dependent increase of thermal analgesia, although it did not exceed 60% of a maximal possible analgesic effect with the largest applied dose (ED50 0-4 h: 76.2 [micro sign]g, 24-28 h: 140.1 [micro sign]g). Partial suppression of mechanical hyperalgesia was observed after IA neostigmine. We conclude that centrally administered neostigmine modulates thermal and mechanical antinociception in this animal model of inflammatory pain. These data suggest a peripheral site of muscarinic antinociception. Implications: This animal study shows that administration of the acetylcholinesteraseinhibitor neostigmine results in enhanced levels of the endogenous neurotransmitter acetylcholine, which seems to act as one of a group of analgesia-modulating compounds at central and peripheral sites in inflammatory pain. (Anesth Analg 1998;86:1027-32)

A multicentre trial comparing different concentrations of ropivacaine plus sufentanil with bupivacaine plus sufentanil for patient-controlled epidural analgesia in labour

Background and objective: To determine the optimal concentration of ropivacaine for bolus-only patient-controlled epidural labour analgesia, three different doses of ropivacaine were evaluated in comparison with bupivacaine in a double-blinded multicentre study. Methods: Four hundred-and-fifty labouring parturients at term in three different academic institutions were randomized to four groups receiving bupivacaine 0.125% with sufentanil 0.75 μg mL−1, ropivacaine 0.125% or 0.175% with sufentanil 0.75 μg mL−1, or ropivacaine 0.2%. After an initial bolus of 10 mL of the study solution, and once visual analogue scores (VAS) were below 30 mm, patient-controlled epidural analgesia was initiated with a bolus of 4 mL, a lockout interval of 15 min and without a background infusion. Variables studied were the quality of analgesia, incidence of side-effects, the degree of motor blockade, and the mode of delivery. Results: Bupivacaine 0.125% and ropivacaine 0.125% with sufentanil proved equally effective in providing labour analgesia without a difference in local anaesthetic consumption (48.6 ± 23 mg bupivacaine vs. 52.1 ± 38 mg ropivacaine), motor blockade or mode of delivery. Ropivacaine 0.175% plus sufentanil enhanced the quality of analgesia of the initial loading dose, whereas ropivacaine 0.2% without sufentanil increased the consumption of local anaesthetics (80.2 ± 34 mg; P < 0.05) and the degree of motor blockade. Conclusion: Despite recent studies indicating that bupivacaine and ropivacaine may not be equipotent, both local anaesthetics provided equi-effective analgesia at equal doses without a difference in side-effects.

Stability of a sufentanil-ropivacaine mixture in a glass and a PVC reservoir

BACKGROUND AND OBJECTIVEnDrug mixtures containing sufentanil may be unstable owing to absorption into the drug reservoirs of patient-controlled epidural analgesia systems that contain polyvinylchloride. The stability of sufentanil in a mixture of ropivacaine 0.2% in a 750 mL reservoir was therefore investigated.nnnMETHODSnDuring simulated epidural infusions of 5 mLh(-1) at 25 degrees C, sufentanil concentrations were measured for 96 h. Samples were taken from the reservoir and from the end of the epidural catheter under the following conditions: into glass or polyvinylchloride reservoirs containing ropivacaine 0.2% with sufentanil 1, 0.75 or 0.5 microg mL(-1); and into polyvinylchloride reservoirs with ropivacaine 0.2% and sufentanil 1 microg mL(-1) which were stored for 4 weeks at 8 degrees C.nnnRESULTSnThe different solutions remained stable over the observation period of 96 h. Using the same solutions, independent samples ANOVA showed no difference in the sufentanil concentrations between the glass and polyvinylchloride reservoirs, or between the polyvinylchloride reservoirs when stored for 4 weeks. Correlations between the concentrations at the different measurement times were extremely high for the reservoir (r(min) = 0.98, r(max) = 1.00) and the catheter end (rmin = 0.86, r(max) = 1.00).nnnCONCLUSIONSnSufentanil citrate at 0.5-1.0 microg mL(-1) in an admixture of ropivacaine 0.29 for 5 days, which is the usual period for postoperative epidural analgesia, remains stable in a polyvinylchloride reservoir. There is no change in the drug concentration even if the reservoir is stored for 4 weeks at 8 degrees C.

Hemodynamic effects of intravenous isoproterenol versus epinephrine in the chronic maternal-fetal sheep preparation

Isoproterenol 5 micro gram may be an effective marker of accidental intravascular injection in women in labor; however, before isoproterenol can be incorporated in routinely used epidural test doses, the safety and usefulness should be determined in an animal model.This study was designed to examine the hemodynamic effects of isoproterenol in comparison with epinephrine in the pregnant ewe. Five doses of isoproterenol were tested and compared with two doses of epinephrine in a randomized cross-over fashion. After administration of isoproterenol there was a small decrease of uterine blood flow (UBF) and maternal mean arterial pressure (MMAP), which both almost immediately returned to baseline. When epinephrine was used a more pronounced and more prolonged decrease of UBF occurred. Increasing doses of isoproterenol resulted in dose-dependent increases in maternal heart rate (MHR), while with epinephrine this was not the case. A significant increase in the cardiac output was seen after isoproterenol. Neither isoproterenol nor epinephrine affected fetal heart rate (FHR), fetal mean arterial pressure (FMAP), amniotic fluid pressure (Amn-pr), blood gases, or acid base status in the mother and the fetus. Provided that neurotoxic effects are absent, isoproterenol might be a better alternative than epinephrine as a test dose for possible intravenous placement of an epidural catheter in pregnant women. (Anesth Analg 1996;82:1023-6)

Effects of Cafedrine/Theodrenaline, Etilefrine and Ephedrine on Uterine Blood Flow during Epidural-Induced Hypotension in Pregnant Sheep

Introduction:Maternal hypotension is a major concern in obstetric anesthesia, and concerns have been raised about standard vasopressor therapy with ephedrine. Therefore, we evaluated the maternal and fetal hemodynamic effects of two potential alternatives to ephedrine. Methods: Hypotension was induced by epidural administration of lidocaine in 6 chronically instrumented pregnant ewes (at 118–122 days of gestation, term 145 days). Three treatments were studied: 25 mg ephedrine, 5 mg etilefrine and 100 mg cafedrine/5 mg theodrenaline (C/T) intravenously. Mean fetal and maternal blood pressure and heart rate, uterine blood flow, as well as fetal and maternal arterial blood gases were recorded for 60 min. Results:All three vasopressors increased maternal blood pressure, accompanied by a significant increase in uterine blood flow. C/T caused marked maternal tachycardia, whereas ephedrine decreased maternal heart rate. Maternal and fetal blood gases did not change during any of the three treatment regimens. Conclusion:All three vasopressors restored maternal blood pressure and uterine blood flow after epidurally induced maternal hypotension. However, restoration of uterine perfusion was delayed and less pronounced with C/T.

Transplacental transfer of remifentanil in the pregnant ewe

Background and purpose:u2002 While remifentanil can be used either during labour or fetal surgery, more should be known about the transplacental transfer of this opioid. The aim of this study was to investigate the placental transfer and haemodynamic effects of remifentanil after i.v. administration to pregnant ewes.

Epidural Local Anesthetics: A Novel Treatment for Fetal Growth Retardation?

Background: Chronically compromised uterine perfusion may lead to placental insufficiency and subsequent intrauterine growth restriction (IUGR). Various therapeutic approaches (e.g. vasodilators, low-dose aspirin, intravenous glucose infusion, and hemodilution) are often of limited efficacy. Local anesthetics have been shown to improve placental blood flow in pre-eclamptic women. We hypothesized that epidural administration of local anesthetics might improve outcome in IUGR independent of the underlying cause. In preparation for a clinical trial to test this hypothesis, we performed a pilot study in 10 patients. Methods: After approval of the study protocol, 10 pregnant women presenting with oligohydramnios and IUGR were included in the study. In addition to our standard protocol (magnesium, glucose, betamethasone), each patient received an epidural catheter (T10/T12) with continuous infusion of bupivacaine 0.175% at a rate of 5 ml/h. Uteroplacental circulation was monitored by Doppler sonography and the amount of amniotic fluid was estimated daily. Results: Epidural insertion and infusion was performed without complications. Four patients continued to deteriorate rapidly, amniotic fluid volume did not change and uterine artery pulsatility index (PI) tended to increase. In the remaining 6 patients the clinical status stabilized, amniotic fluid volume tended to increase and uterine artery PI tended to decrease during treatment. This improvement was associated with a prolonged interval to cesarean section and increased infant birth weight. Conclusion: Our data suggest that, even if the underlying cause of IUGR is not pre-eclampsia, epidural local anesthetic administration might improve placental blood flow and be beneficial in a subgroup of patients. A clinical trial to test this hypothesis appears warranted.

Assessment of volume preload on uteroplacental blood flow during epidural anaesthesia for Caesarean section.

Background and objective: Epidural and spinal anaesthesia are the preferred mode of anaesthesia for Caesarean section. Volume preloading is recommended to prevent maternal hypotension and a reduction in uteroplacental blood flow, although positive effects of volume preloading on maternal cardiac output and arterial pressure are debatable. Doppler measurements of the umbilical artery beyond deriving pulsatility indices are not routinely performed. Methods: After Institutional Review Board approval and written informed consent, 14 consecutive women with epidural anaesthesia for Caesarean section received either hydroxyethyl starch 500 mL or gelatine 500 mL. Haemodynamic variables monitored were maternal arterial pressure, maximal blood flow velocity and pulsatility indices of the uterine artery derived from Doppler measurements. Conclusions: Maternal arterial pressure and pulsatility indices in both groups did not change from baseline after intravenous colloid infusion. However, uterine blood flow increased significantly in both groups. The effectiveness of volume preloading may therefore be better described by changes in maximum uterine blood flow velocity than by pulsatility indices or maternal arterial pressure.

Prostaglandin-induced ventricular fibrillation during cesarean section

A case report is presented of ventricular fibrillation after intramyometrial injection of 1 mg dinoprostone (PGE(2)) during cesarean section performed under general anesthesia. Anesthesiologists should be aware of the potential cardiovascular side-effects of prostaglandins used by the obstetrician.