Preemptive intravenous morphine-6-glucuronide is ineffective for postoperative pain relief.
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BACKGROUND: Morphine-6-glucuronide (M-6-G), a major metabolite of morphine, is reported to be more potent than morphine when administered intrathecally; however, its efficiency remains under debate when administered intravenously. This study was designed to assess the analgesic efficiency of intravenous M-6-G for the treatment of acute postoperative pain. METHODS: After informed consent was obtained, 37 adults (American Society of Anesthesiologists physical status I-II) who were scheduled for elective open knee surgery were enrolled in the study. General anesthesia was induced with thiopental, alfentanil, and vecuronium and was maintained with a mixture of nitrous oxide/isoflurane and bolus doses of alfentanil. At skin closure, patients were randomized into three groups: (1) morphine group (n = 13), which received morphine 0.15 mg/kg; (2) M-6-G group (n = 12), which received M-6-G 0.1 mg/kg; and (3) placebo group (n = 12), which received saline. At the time of extubation, plasma concentration of morphine and M-6-G was measured. Postoperative analgesic efficiency was assessed by the cumulative dose of morphine delivered by patient-controlled analgesia. Opioid-related side effects were also evaluated. RESULTS: No difference was noted in patient characteristics and opioid-related side effects. Morphine requirements (mean +/- SD) during the first 24 h in the M-6-G group (41+/-9 mg) and the placebo group (49+/-8 mg) were significantly greater (P<0.05) compared with the morphine group (29+/-8 mg). CONCLUSION: A single intravenous bolus dose of M-6-G was found to be ineffective in the treatment of acute postoperative pain. This might be related to the low permeability of the blood-brain barrier for M-6-G. (+info)
Heat production in human skeletal muscle at the onset of intense dynamic exercise.
(26/794)
1. We hypothesised that heat production of human skeletal muscle at a given high power output would gradually increase as heat liberation per mole of ATP produced rises when energy is derived from oxidation compared to phosphocreatine (PCr) breakdown and glycogenolysis. 2. Five young volunteers performed 180 s of intense dynamic knee-extensor exercise ( approximately 80 W) while estimates of muscle heat production, power output, oxygen uptake, lactate release, lactate accumulation and ATP and PCr hydrolysis were made. Heat production was determined continuously by (i) measuring heat storage in the contracting muscles, (ii) measuring heat removal to the body core by the circulation, and (iii) estimating heat transfer to the skin by convection and conductance as well as to the body core by lymph drainage. 3. The rate of heat storage in knee-extensor muscles was highest during the first 45 s of exercise (70-80 J s-1) and declined gradually to 14 +/- 10 J s-1 at 180 s. 4. The rate of heat removal by blood was negligible during the first 10 s of exercise, rising gradually to 112 +/- 14 J s-1 at 180 s. The estimated rate of heat release to skin and heat removal via lymph flow was < 2 J s-1 during the first 5 s and increased progressively to 24 +/- 1 J s-1 at 180 s. The rate of heat production increased significantly throughout exercise, being 107 % higher at 180 s compared to the initial 5 s, with half of the increase occurring during the first 38 s, while power output remained essentially constant. 5. The contribution of muscle oxygen uptake and net lactate release to total energy turnover increased curvilinearly from 32 % and 2 %, respectively, during the first 30 s to 86 % and 8 %, respectively, during the last 30 s of exercise. The combined energy contribution from net ATP hydrolysis, net PCr hydrolysis and muscle lactate accumulation is estimated to decline from 37 % to 3 % comparing the same time intervals. 6. The magnitude and rate of elevation in heat production by human skeletal muscle during exercise in vivo could be the result of the enhanced heat liberation during ATP production when aerobic metabolism gradually becomes dominant after PCr and glycogenolysis have initially provided most of the energy. (+info)
Measurement of fatigue in knee flexor and extensor muscles.
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In order to examine fatigue of the knee flexor and extensor muscles and to investigate the characteristics of muscular fatigue in different sports, a Cybex machine was used to measure muscle fatigue and recovery during isokinetic knee flexion and extension. Eighteen baseball players, 12 soccer players and 13 marathon runners were studied. Each subject was tested in the sitting position and made to perform 50 consecutive right knee bends and stretches at maximum strength. This was done 3 times with an interval of 10 min between each series. The peak torque to body weight ratio and the fatigue rate were determined in each case. In all subjects, the peak torque to body weight ratio was higher for extensors than flexors. Over the 3 trials, the fatigue rate of extensors showed little change, while that of flexors had a tendency to increase. In each subject, knee extensors showed a high fatigue rate but a quick recovery, while knee flexors showed a low fatigue rate but a slow recovery. As the marathon runners had the smallest fatigue rates for both flexors and extensors, we concluded that marathon runners had more stamina than baseball players and soccer players. (+info)
Above-knee prosthetic femoropopliteal bypass for intermittent claudication. Results of the initial and secondary procedures.
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OBJECTIVES: [corrected] to report the results of primary and secondary prosthetic above-knee femoropopliteal bypass for intermittent claudication. DESIGN: a retrospective study in a University hospital. PATIENTS: one hundred and twelve operations performed in 103 patients (26 women) between January 1990 and June 1997. METHODS: a comparison of primary assisted patency was made between Dacron and PTFE, between men and women and between operations performed early and late in the study period. Patency of secondary procedures was also studied. RESULTS: there were no operative deaths. The 5-year survival rate was 81% and equal to that of a demographically matched population. The primary assisted graft patency was 58% after two years. Women had a significantly better graft patency than men (79% vs. 49%). The type of graft and the date of the operation did not influence the outcome. Forty of the 55 occluded grafts were subjected to a redo procedure with a 1-year patency of 29%. CONCLUSIONS: the results after prosthetic above-knee femoropopliteal bypass procedures are disappointing, and a controversy persists as to whether this operation should be performed for intermittent claudication. The results of secondary procedures are even worse, and perhaps should only be considered in patients suffering critical ischaemia. (+info)
Fatigue responses of human triceps surae muscles during repetitive maximal isometric contractions.
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Nine healthy men (22-45 yr) completed 100 repetitive maximal isometric contractions of the ankle plantar flexor muscles in two knee positions of full extension (K0) and flexion at 90 degrees (K90), positions that varied the contribution of the gastrocnemii. Electromyographic activity was recorded from the medial and lateral gastrocnemii and soleus muscles by using surface electrodes. Plantar flexion torque in K0 was greater and decreased more rapidly than in K90. The electromyographic amplitude decreased over time, and there were no significant differences between muscles and knee joint positions. The level of voluntary effort, assessed by a supramaximal electrical stimulation during every 10th contraction, decreased from 96 to 70% (P < 0.05) with no difference between K0 and K90. It was suggested that a decrease in plantar flexion torque was attributable to both central and peripheral fatigue and that greater fatigability in K0 than in K90 would result from a greater contribution and hence more pronounced fatigue of the gastrocnemius muscle. Further support for this possibility was provided from changes in twitch torque. (+info)
Postactivation potentiation, fiber type, and twitch contraction time in human knee extensor muscles.
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In small mammals, muscles with shorter twitch contraction times and a predominance of fast-twitch, type II fibers exhibit greater posttetanic twitch force potentiation than muscles with longer twitch contraction times and a predominance of slow-twitch, type I fibers. In humans, the correlation between potentiation and fiber-type distribution has not been found consistently. In the present study, postactivation potentiation (PAP) was induced in the knee extensors of 20 young men by a 10-s maximum voluntary isometric contraction (MVC). Maximal twitch contractions of the knee extensors were evoked before and after the MVC. A negative correlation (r = -0. 73, P < 0.001) was found between PAP and pre-MVC twitch time to peak torque (TPT). The four men with the highest (HPAP, 104 +/- 11%) and lowest (LPAP, 43 +/- 7%) PAP values (P < 0.0001) underwent needle biopsies of vastus lateralis. HPAP had a greater percentage of type II fibers (72 +/- 9 vs. 39 +/- 7%, P < 0.001) and shorter pre-MVC twitch TPT (61 +/- 12 vs. 86 +/- 7 ms, P < 0.05) than LPAP. These data indicate that, similar to the muscles of small mammals, human muscles with shorter twitch contraction times and a higher percentage of type II fibers exhibit greater PAP. (+info)
Knee functions and a return to sports activity in competitive athletes following anterior cruciate ligament reconstruction.
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We investigated knee functions and a return to sports in 50 competitive athlete patients treated with arthroscopic anterior cruciate ligament reconstruction using double-looped STG augmented by woven polyester at a 1-year follow-up. There were 25 males and 25 females with a mean age of 24.3 years (range: 19-39 years). The majority of preinjury sports were basketball, volleyball and soccer. Athletic rehabilitation including agility training and sports-specific training was started at 12 weeks. Fourty patients (80%) was rated as normal or nearly normal on the assessment of International Knee Documentation Commitee postoperatively. Fourty-eight patients (96%) obtained full range of motion, and the mean quadriceps muscle strength of the injured side was 91.3%of that of the uninjured side. As for a return to sports, 46 patients (92%) were able to do fully competitive sports at a mean of 8.1 postoperative months. These results suggest that arthroscopic reconstruction using augmented double-looped STG allows early athletic rehabilitation, and lead satisfactory outcome as well as a reliable and early return to preinjury level of sport activity for the majority of the competitive athlete patients. (+info)
Pseudoaneurysm of the medial inferior genicular artery following anterior cruciate ligament reconstruction.
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Pseudoaneurysm is a rare complication of surgery or trauma around the knee. A 30-year-old man presented 10 days following anterior cruciate ligament repair with a 2 cm pulsatile swelling on the medial side of the knee. Angiography demonstrated a pseudoaneurysm of the medial inferior genicular artery. Surgical exploration and ligation of the feeding vessel to the aneurysm was performed and the patient made a full recovery. Vascular injury must be suspected in patients presenting with a haemarthrosis or pulsatile swelling following surgery on the knee. (+info)