Intrathecal morphine and clonidine for coronary artery bypass grafting

Background. After cardiac surgery adequate postoperative analgesiais necessary. We assessed analgesia using intrathecal morphineand clonidine. Methods. In a double-blind randomized study, 45 patients havingcoronary artery bypass graft surgery were allocated randomlyto receive i.v. patient-controlled analgesia (PCA) morphine(bolus, 1 mg; lock-out interval, 7 min) (control group), eitheralone or combined with intrathecal morphine 4 µg kg^–1or with both intrathecal morphine 4 µg kg^–1and clonidine 1 µg kg^–1. Intrathecal injectionswere performed before the induction of general anaesthesia.Pain was measured after surgery using a visual analogue scale(VAS). We recorded i.v. PCA morphine consumption during the24 h after operation. Results. Morphine dosage [median (25th–75th percentiles)]was less in the first 24 h in the patients who were given intrathecalmorphine + clonidine [7 (0–37) mg] than in other patients[40.5 (15–61.5) mg in the intrathecal morphine group and37 (30.5–51) mg in the i.v. morphine group]. VAS scoreswere lower after intrathecal morphine + clonidine compared withthe control group. Time to extubation was less after intrathecalmorphine + clonidine compared with the i.v. morphine group [225(195–330) vs 330 (300–360) min, P<0.05]. Conclusion. Intrathecal morphine and clonidine provide effectiveanalgesia after coronary artery bypass graft surgery and allowearlier extubation. Br J Anaesth 2003; 90: 300–3     

Prevention of postoperative nausea and vomiting after spinal morphine for Caesarean section: comparison of cyclizine,dexamethasone and placebo

Background. Low-dose intrathecal (spinal) morphine (0.1–0.2mg) for Caesarean section delivers excellent postoperative analgesiabut is associated with significant nausea and vomiting. We comparedthe antiemetic efficacy of cyclizine, dexamethasone, and placeboin this clinical setting. Methods. Ninety-nine women undergoing elective Caesarean sectionunder spinal anaesthesia were allocated randomly, in a double-blindstudy design, to receive either cyclizine 50 mg, dexamethasone8 mg, or placebo as a single-dose infusion in saline 0.9%, 100ml on completion of surgery. Spinal anaesthesia consisted of:hyperbaric bupivacaine 0.5%, 2.0 ml; fentanyl 10 µg; andspinal morphine 0.2 mg. The primary outcome measure was theincidence of nausea. Results. The incidence of nausea was significantly less in patientsreceiving cyclizine compared with dexamethasone and placebo(33 vs 60 and 67%, respectively, P<0.05). Severity of nauseaand number of vomiting episodes were also less at 3–6h in cyclizine patients. Overall satisfaction with postoperativecare at 24 h, expressed on a 100 mm visual analogue scale, wasgreater in cyclizine [78 (28)] than either dexamethasone [58(31), P=0.03] or placebo [51 (28), P=0.008]. Conclusion. We conclude that following spinal morphine 0.2 mgand fentanyl 10 µg analgesia for Caesarean section, cyclizine50 mg i.v. reduces the incidence of nausea compared with dexamethasone8 mg i.v. or placebo. It also lessens the severity of nauseaand vomiting, and increases maternal satisfaction in the earlypostoperative period. Br J Anaesth 2003; 90: 665–70     

Addition of meperidine to bupivacaine for spinal anaesthesia for Caesarean section

Background. In a prospective, randomized, double-blind, placebo-controlledtrial, we investigated the effect of adding meperidine 10 mgto intrathecal bupivacaine on the duration of early postoperativeanalgesia in 40 patients having elective Caesarean section underspinal anaesthesia. Methods. Patients received intrathecal injection of 0.5% hyperbaricbupivacaine 2.0 ml plus either normal saline 0.2 ml (salinegroup) or 5% meperidine 0.2 ml (meperidine group). Afteroperation, all patients were given i.v. patient-controlled analgesiausing morphine. Results. The duration of effective analgesia, defined as thetime from intrathecal injection to first patient-controlledanalgesia demand, was greater in the meperidine group (mean234 min, 95% confidence interval 200–269 min)compared with the saline group (mean 125 min, 95% confidenceinterval 111–138 min; P<0.001). The 24 hmorphine requirement was similar in the two groups. The meperidinegroup had a greater incidence of intraoperative nausea or vomitingcompared with the saline group (11 vs 3; P=0.02). Conclusion. Addition of meperidine 10 mg to intrathecalbupivacaine for Caesarean section is associated with prolongedpostoperative analgesia but with greater intraoperative nauseaand vomiting. Br J Anaesth 2002; 88: 379–83     

Emetic effects of morphine and piritramide

Background. Successful management of postoperative pain requiresthat adequate analgesia is achieved without excessive adverseeffects. Opioid-induced nausea and vomiting is known to impairpatients’ satisfaction, but there are no studies providingsufficient power to test the hypothesis that the incidence ofopioid-induced nausea and vomiting differs between µ-opioidreceptor agonists. Thus, we tested the hypothesis that the incidenceof vomiting and nausea differs between morphine and piritramide. Methods. In a prospective, randomized, double-blind fashion,we administered either morphine (n=250) or piritramide (n=250)by patient-controlled analgesia (PCA) for postoperative painrelief. We used a bolus dose of 1.5 mg with a lockout time of10 min. Incidence and intensity (numerical rating scale) ofpostoperative nausea, vomiting, pain, patient satisfaction (score0–10), side-effects (score 0–3) and drug consumptionwere measured. Results. Mean drug consumption did not differ between the piritramideand morphine groups (30.8 (SD 22.4) mg day^–1 vs 28.4 (21.8)mg day^–1) during the first postoperative day and therewere no significant differences in the overall incidence ofnausea (30% vs 27%) and vomiting (19% vs 15%). Intensity ofnausea correlated inversely (P=0.01) with morphine consumptionbut not with piritramide consumption. Pain scores both at rest(2.2 (1.9) vs 2.6 (2)) and during movement (4.4 (2.2) vs 4.9(2.3)) were slightly but significantly less with morphine. Conclusions. Opioid-induced emesis was observed in about one-thirdof the patients using morphine and piritramide for PCA and theincidence of vomiting was one-half of that. Potential differencesin the incidence of vomiting during PCA therapy between theseµ-opioid receptor agonists can be excluded. Br J Anaesth 2003; 91: 218–23     

Epinephrine and clonidine do not improve intrathecal sufentanil analgesia after total hip replacement

Background. We compared analgesia after intrathecal sufentanilalone, sufentanil with epinephrine 200 µg and sufentanilwith clonidine 30 µg in patients after total hip replacement,the endpoints being onset and duration of action. Methods. We performed a randomized double-blind study of 45patients for elective total hip arthroplasty using continuousspinal anaesthesia. As soon as a pain score higher than 3 ona 10 cm visual analogue scale was reported, sufentanil 7.5 µgalone, sufentanil 7.5 µg + epinephrine 200 µg orsufentanil 7.5 µg + clonidine 30 µg in 2 ml normalsaline was given intrathecally. Pain scores, rescue analgesia(diclofenac and morphine) and adverse effects (respiratory depression,postoperative nausea and vomiting, itching) were observed for24 h after surgery. Results. Time to a pain score of <3 [6 (SD 1) vs 6 (1) vs5 (1) min], time to the lowest pain score [7 (2) vs 8 (2) vs8 (2) min] and time to the first dose of systemic analgesicfor a pain score >3 [281 (36) vs 288 (23) vs 305 (30) min]were similar in all three groups. Adverse effects and analgesicrequirements during the first 24 h were also similar. Conclusion. After total hip replacement, all three analgesicregimens gave good analgesia with comparable onset and durationof action, and minor adverse effects. Br J Anaesth 2002; 89: 562–6     

Comparison of intrathecal isobaric bupivacaine-morphine and ropivacaine-morphine for Caesarean delivery

Background. This study was designed to evaluate the effectsof intrathecal isobaric bupivacaine 0.5% plus morphine and isobaricropivacaine 0.5% plus morphine combinations in women undergoingCaesarean deliveries. Method. Twenty-five parturients received ropivacaine 15 mg andmorphine 150 µg (RM group) and twenty-five parturientsreceived bupivacaine 15 mg and morphine 150 µg (BM group)for spinal anaesthesia. Sensory and motor block, haemodynamics,postoperative analgesia, fetal outcomes, and side-effects wereevaluated. Results. Intrathecal bupivacaine–morphine and ropivacaine–morphineprovided effective sensory anaesthesia and motor block. Timeto reach complete motor block was shorter and time to completerecovery from motor block was longer in the BM group than theRM group (P<0.05). The time to regression of two dermatomesand time for the block to recede to the S2 dermatome were similarin both groups (P>0.05). Time to first complaint of painand the mean total consumption of tenoxicam were similar inboth groups (P>0.05). APGAR scores at 1 and 5 min were similarin the two groups, as were mean umbilical blood pH values (P>0.05).Hypotension and pruritus were the most common side-effects inboth groups during the operation. Conclusion. Intrathecal isobaric ropivacaine 0.5% 15 mg plusmorphine 150 µg provides sufficient anaesthesia for Caesareandelivery. The ropivacaine–morphine combination resultedin shorter motor block, similar sensory and postoperative analgesia. Br J Anaesth 2003; 90: 659–64     

Effect of epidural bupivacaine vs combined epidural bupivacaine and morphine on gastrointestinal function and pain after major gynaecological surgery

In a double-blind study, we investigated the effects of postoperativeepidural local anaesthetic, with or without addition of epiduralmorphine, on postoperative pain and gastrointestinal functionin patients scheduled for radical hysterectomy and pelvic lymphadenectomy.Forty patients were randomized into two study groups: 48-h postoperativeepidural 0.2% bupivacaine 8 ml h^–1 (bupi group)or 48-h postoperative epidural 0.2% bupivacaine/morphine 50µg at 4 ml h^–1 (bupi/morph group). Patients wereobserved for at least 96 h after surgery. No differencesin pain at rest, during cough or mobilization were observed.Patients in the bupi group requested a significant greater amountof supplementary analgesics, but times to first flatus and defaecationwere reduced compared with patients in the bupi/morph group.Itching was a significant problem in patients in the bupi/morphgroup. No differences in postoperative nausea and vomiting,mobilization or time to discharge from hospital were observedbetween groups. The addition of morphine to postoperative epiduralbupivacaine has only limited effect on pain relief and increasestime to normalization of gastrointestinal function. Br J Anaesth 2001; 87: 727–32     

Parecoxib sodium has opioid-sparing effects in patients undergoing total knee arthroplasty under spinal anaesthesia

Background. This multicentre, double-blind, placebo-controlledstudy compared the opioid-sparing effectiveness and clinicalsafety of parecoxib sodium over 48 h, in 195 postoperativepatients after routine total knee replacement surgery. Methods. Elective total primary knee arthroplasty was performedunder spinal anaesthesia, with a single dose of spinal bupivacaine10–20 mg, and intraoperative sedation with midazolam0.5–1.0 mg i.v., or propofol <6 mg kg^–1h^–1. Patients were randomized to receive either parecoxibsodium 20 mg twice daily (bd) i.v. (n=65), parecoxib sodium40 mg bd i.v. (n=67), or placebo (n=63) at the completionof surgery, and after 12, 24, and 36 h. Morphine (1–2 mg)was taken by patient-controlled analgesia or by bolus dosesafter 30 min. Results. Patients receiving parecoxib sodium 20 mg bd and40 mg bd consumed 15.6% and 27.8% less morphine at 24 hthan patients taking placebo (both P<0.05). Both doses ofparecoxib sodium administered with morphine provided significantlygreater pain relief than morphine alone from 6 h (P<0.05).A global evaluation of study medication demonstrated a greaterlevel of satisfaction among patients taking parecoxib sodiumthan those taking placebo. Parecoxib sodium administered incombination with morphine was well tolerated. However, a reductionin opioid-type side-effects was not demonstrated in the parecoxibsodium groups. Conclusion. Parecoxib sodium provides opioid-sparing analgesiceffects in postoperative patients. Br J Anaesth 2003; 90: 166–72     

Dexamethasone for prophylaxis of nausea and vomiting after epidural morphine for post-Caesarean section analgesia: comparison of droperidol and saline

We have evaluated the prophylactic effect of i.v. dexamethasone8 mg in preventing nausea and vomiting during epiduralmorphine for post-Caesarean section analgesia. Droperidol 1.25 mgand saline served as the control. We studied 120 parturients(n=40 in each group) receiving epidural morphine for post-Caesareansection analgesia, in a randomized, double-blind, placebo-controlledstudy. All parturients received epidural morphine 3 mg. Bothdexamethasone and droperidol significantly decreased the totalincidence of nausea and vomiting compared with saline, withincidences of 18, 21 and 51% for the three treatments respectively(P<0.01 and P<0.05 respectively). Parturients who receiveddroperidol reported a more frequent incidence of restlessness(16%) than those who received dexamethasone (P<0.05). Br J Anaesth 2000; 85: 865–8     

Epidural versus intrathecal morphine for postoperative analgesia after Caesarean section

Background. Perispinal anaesthesia for Caesarean section allowsinjection of epidural (ED) or intrathecal (i.t.) morphine toprovide long-lasting postoperative analgesia. To compare thesetwo routes, a prospective, randomized, double-blinded studyof 53 patients undergoing elective Caesarean section was performed. Methods. Combined spinal-epidural anaesthesia with 6 mg of i.t.hyperbaric bupivacaine plus sufentanil 5 µg, and additionalED lidocaine was used. Additionally, each patient received either2 mg (2 ml) of ED morphine plus 1 ml of i.t. normal saline (EDgroup, n=28), or 0.075 mg (1 ml) of i.t. morphine plus 2 mlof ED normal saline (i.t. group, n=25). Additional postoperativeanalgesia was given in the form of propacetamol and ketoprofen,plus self-administered i.v. morphine. Results. No major respiratory depression occurred. Time to firstdemand of morphine was similar in the ED (307.5 min) and i.t.(310 min) groups, as was the incidence of side-effects suchas sedation, pruritis, nausea, and vomiting. During the first24 postoperative hours, VAS pain scores were greater in thei.t. group (P=0.032), as was additional morphine consumption(4 vs 1.5 mg) (P=0.03). Conclusions. The ED protocol was more effective than the i.t.protocol, whilst side-effects were similar. Br J Anaesth 2003; 91: 690–4     

Intrathecal morphine overdose during combined spinal-epidural block for Caesarean delivery

We describe a 25 mg intrathecal morphine overdose duringa combined spinal–epidural block for a Caesarean delivery.Naloxone infusion (5.24 mg over 24 h) was startedprior to the patient becoming symptomatic and almost immediatelyafter the overdose. Invasive therapeutics such as mechanicalventilation were avoided. Br J Anaesth 2002; 89: 925–7     

The effect of epidural sufentanil in ropivacaine on urinary retention in patients undergoing gastrectomy

Background. Although epidural opioids have excellent analgesicproperty, their side-effects limit its use in patient-controlledepidural analgesia (PCEA). This study was designed to compareside-effects of epidural sufentanil in ropivacaine with thatof morphine in ropivacaine focusing on lower urinary tract functionafter major abdominal surgery. Methods. In total 60 patients undergoing gastrectomy were randomlyallocated to receive either sufentanil in ropivacaine (GroupS, n=30) or morphine in ropivacaine (Group M, n=30) for theirPCEA. Epidural catheter was inserted between the 7th and 8ththoracic spine. Visual analogue pain score and side-effectssuch as nausea, vomiting, pruritus, hypotension and urinaryretention were evaluated during postoperative days (PODs) 1and 2 in the postanaesthetic care unit. Results. The incidence of serious to major micturition problemin Group S was lower than that in Group M (P<0.001). Theincidence of pruritus, nausea and vomiting was also lower inGroup S than in Group M on POD 1. Conclusions. The lower incidence of major/serious micturitionproblem in patients receiving sufentanil in ropivacaine thoracicepidural analgesia suggests that continuation of urinary drainagemay not be necessary from POD 1 onwards.     

Pre-emptive analgesic efficacy of tramadol compared with morphine after major abdominal surgery

Background. Studies of pre-emptive analgesia in humans haveshown conflicting results. This prospective, randomized, double-blind,controlled study was designed to test the hypothesis that areduction in postoperative morphine consumption can be achievedby tramadol administered after induction of anaesthesia. Methods. Ninety patients were allocated randomly to receivei.v. tramadol (1 mg kg^–1) (Group T), morphine(0.1 mg kg^–1) (Group M) or saline 2 ml(Group S) after induction of anaesthesia. At peritoneal closure,a standardized (0.1 mg kg^–1) morphine loadingdose was given to all patients for postoperative pain management.Patients were allowed to use a patient-controlled analgesia(PCA) device giving bolus doses of morphine 0.025 mg kg^–1.Discomfort, sedation, pain scores, cumulative morphine consumption,and side-effects were recorded at 1, 2, 6, 12 and 24 hafter the start of PCA. Results. There were no significant differences between groupsin mean pain, discomfort, and sedation scores at any study period.Cumulative morphine consumption was significantly lower in GroupM at 12 and 24 h after starting the PCA than in Group S.In Group T, it was lower only after 24 h (28% less in GroupM and 17% less in Group T; P<0.017). There were no significantdifferences in morphine consumption between Groups T and M. Conclusions. Tramadol (1 mg kg^–1), administeredafter induction of anaesthesia, offered equivalent postoperativepain relief, and similar recovery times and postoperative PCAmorphine consumption compared with giving morphine 0.1 mg kg^–1.These results also suggest that presurgical exposure to systemicopioid analgesia may not result in clinically significant benefits Br J Anaesth 2003; 91: 209–13     

Effects of acetaminophen on morphine side-effects and consumption after major surgery: meta-analysis of randomized controlled trials

Background. Acetaminophen is commonly used for the managementof perioperative pain. However, there is a marked discrepancybetween the extent to which acetaminophen is used and the availableevidence for an analgesic effect after major surgery. The aimof this systematic review is to determine the morphine-sparingeffect of acetaminophen combined with patient-controlled analgesia(PCA) with morphine and to evaluate its effects on opioid-relatedadverse effects. Methods. MEDLINE and the Cochrane Library were searched to selectrandomized controlled trials which compared PCA morphine alonewith PCA morphine plus acetaminophen administered orally orintravenously. Studies were evaluated for their quality basedon the Oxford Quality Scale. Outcome measures were morphineconsumption over the first 24 h after surgery, patient satisfactionand the incidence of morphine side-effects, including nauseaand vomiting, sedation, urinary retention, pruritus and/or respiratorydepression. Results. Seven prospective randomized controlled trials, including265 patients in the group with PCA morphine plus acetaminophenand 226 patients in the group with PCA morphine alone, wereselected. Acetaminophen administration was not associated witha decrease in the incidence of morphine-related adverse effectsor an increase in patient satisfaction. Adding acetaminophento PCA was associated with a morphine-sparing effect of 20%(mean, –9 mg; CI –15 to –3 mg; P=0.003) overthe first postoperative 24 h. Conclusion. Acetaminophen combined with PCA morphine induceda significant morphine-sparing effect but did not change theincidence of morphine-related adverse effects in the postoperativeperiod.      

Effect of intravenous alizapride on spinal morphine-induced pruritus

Background. This double-blind study was undertaken to determinewhether alizapride inhibits spinal morphine-induced pruritus. Methods. Eighty-four patients undergoing Caesarean section underspinal anaesthesia (100 mg of hyperbaric lidocaine 5% plus morphine0.2 mg) were randomly allocated to one of two groups. Justafter birth, alizapride—50 mg (alizapride group)or metoclopramide—10 mg (metoclopramide group) wereinjected i.v. Patients were assessed after surgery for pruritus(absent, mild, moderate or severe) or other untoward symptoms. Results. In the metoclopramide group, pruritus was absent in5 (12%) patients, mild in 23 (55%), moderate in 11 (26%), andsevere in 3 (7%), while in the alizapride group, these incidenceswere, respectively, 5 (12%), 33 (79%), 4 (10%), and 0 (P=0.045,     

Cost-effectiveness of three combinations of antiemetics in the prevention of postoperative nausea and vomiting

Background. This study compares the cost-effectiveness of threecombinations of antiemetics in the prevention of postoperativenausea and vomiting (PONV). Methods. We conducted a prospective, double-blind study. NinetyASA I–II females, 18–65 yr, undergoing general anaesthesiafor major gynaecological surgery, with standardized postoperativeanalgesia (intrathecal 0.2 mg plus i.v. PCA morphine), wererandomly assigned to receive: ondansetron 4 mg plus droperidol1.25 mg after induction and droperidol 1.25 mg 12 h later (Group1); dexamethasone 8 mg plus droperidol 1.25 mg after inductionand droperidol 1.25 mg 12 h later (Group 2); ondansetron 4 mgplus dexamethasone 8 mg after induction and placebo 12 h later(Group 3). A decision analysis tree was used to divide eachgroup into nine mutually exclusive subgroups, depending on theincidence of PONV, need for rescue therapy, side effects andtheir treatment. Direct cost and probabilities were calculatedfor each subgroup, then a cost-effectiveness analysis was conductedfrom the hospital point of view. Results. Groups 1 and 3 were more effective (80 and 70%) thanGroup 2 (40%, P=0.004) in preventing PONV but also more expensive.Compared with Group 2, the incremental cost per extra patientwithout PONV was €6.99 (95% CI, –1.26 to 36.57) forGroup 1 and €13.55 (95% CI, 0.89–132.90) for Group3. Conclusion. Ondansetron+droperidol is cheaper and at least aseffective as ondansetron+ dexamethasone, and it is more effectivethan dexamethasone+droperidol with a reasonable extra cost. Br J Anaesth 2003; 91: 589–92     

Intrathecal morphine in anesthesia for cesarean delivery: dose-response relationship for combinations of low-dose intrathecal morphine and spinal bupivacaine

STUDY OBJECTIVE: To evaluate the quality of analgesia and the severity of side effects of intrathecal morphine administered for a dose range of 0.0 to 0.4 mg for postcesarean analgesia with low-dose bupivacaine. DESIGN: Double-blind, randomized study. SETTING: University hospital. PATIENTS: 100 ASA physical status I and II term parturients undergoing cesarean delivery with spinal anesthesia in the operating room. INTERVENTIONS: Patients were randomized to one of 5 groups to receive 0.0, 0.1, 0.2, 0.3, or 0.4 mg intrathecal morphine in addition to low-dose (7.5 mg) heavy bupivacaine. Each patient received intravenous (IV) patient-controlled analgesia (PCA) with morphine after the operation. MEASUREMENTS: 24-hour IV PCA morphine use and visual analog scores for pain were recorded. The severity score (4-point scale) of nausea, vomiting, and pruritus were assessed intraoperatively and at 4-hour intervals during the first 24 hours postoperatively. MAIN RESULTS: PCA morphine use was higher in the control group (0.0 mg) than in groups receiving 0.1, 0.2, 0.3, or 0.4 mg intrathecal morphine. There was no difference in IV PCA morphine use between the 0.1 and 0.4-mg groups, despite a 4-fold increase in intrathecal morphine dose. There was no difference between groups in nausea and vomiting, but pruritus increased in direct proportion to the dose of intrathecal morphine (linear regression, P = 0.0001). CONCLUSIONS: The dose of 0.1 mg intrathecal morphine produces analgesia comparable with doses as high as 0.4 mg, with significantly less pruritus when combined with low-dose bupivacaine.     

Dolasetron prophylaxis reduces nausea and postanaesthesia recovery time after remifentanil infusion during monitored anaesthesia care for extracorporeal shock wave lithotripsy

Background. Remifentanil is used as an analgesic for differentprocedures performed during monitored anaesthesia care. Opioid-inducednausea and vomiting can be troublesome. Methods. This prospective, randomized, double-blind study wasperformed to evaluate the efficacy of prophylaxis with dolasetronin reducing the frequency of postoperative nausea and durationof discharge time. Forty urological patients, undergoing electiveambulatory extracorporeal shock wave lithotripsy (ESWL) receivedrandomly either dolasetron 12.5 mg i.v. (Group 1) or placebo(Group 2) 10 min before a patient-adapted continuous infusionof remifentanil 0.15–0.4 µg kg^–1 min^–1was administered. Frequency and intensity (VAS 0–100 mm)of nausea, retching, and vomiting were assessed by patientsand blinded investigators during and after the procedure. Results. Patient characteristics, baseline values, durationof ESWL, and total dose of remifentanil did not differ betweengroups. The frequency (Group 1/Group 2; 20/55%; P<0.05) andmean (SD) maximal intensity [15 (9)/45 (14) mm; P<0.05] ofnausea during 24 h was significantly reduced after dolasetronand discharge times in Group 1 were less than Group 2[22 (14)/45 (28) min; P<0.05]. Br J Anaesth 2003; 90: 194–8     

Electrophysiological effects of morphine in an in vitro model of the 'border zone' between normal and ischaemic-reperfused guinea-pig myocardium

Background. Morphine is commonly used in clinical practice inpain management. Although morphine has been shown to preconditionthe myocardium, its effects on action potential parameters andischaemia–reperfusion-induced arrhythmias and conductionblocks remain unknown. Methods. In a double-chamber bath, guinea-pig right ventricularmuscle strips were subjected partly to normal conditions andpartly to 30 min of simulated ischaemia (hypoxia, hyperkalaemia,acidosis, and lack of nutritional substrate) followed by 30 minof reperfusion. Action potential parameters were recorded continuouslyin the normal zone and in the ischaemic– reperfused zone.Spontaneous arrhythmias and conduction blocks were noted. Theelectro physiological effects of morphine were studied at 0.01and 0.1 µM. Results. In control conditions, morphine did not modify actionpotential parameters of resting membrane potential, maximalupstroke velocity (V_max), action potential amplitude (APA) andaction potential duration at 50 and 90% of repolarization. Morphinereduced ischaemia-induced depolarization and lessened the ischaemia-induceddecrease in APA and V_max. Morphine significantly decreased theoccurrence of conduction block during simulated ischaemia (20%at 0.01 and 0.1 µM vs 67% in the control group, P<0.05)and reperfusion-induced arrhythmias (40% at 0.01 µMand 30% at 0.1 µM vs 92% in the control group, P<0.05). Conclusions. In ischaemic–reperfused guinea-pig myocardium,morphine at clinically relevant concentrations decreased ischaemia-inducedconduction blocks and reperfusion-induced ventricular arrhythmias. Br J Anaesth 2002; 89: 888–95