THE ACTION OF MORPHINE-LIKE DRUGS ON IMPULSE TRANSMISSION IN MAMMALIAN NERVE FIBRES

Postoperative hemodynamics after high spinal block with or without intrathecal morphine in cardiac surgical patients: a randomized-controlled trial

PURPOSE

There is some evidence for the use of intrathecal morphine as a means to provide prolonged analgesia in selective cardiac surgical patients; however, the hemodynamic effects of intrathecal morphine are not well defined. This study was designed to study the effect of intrathecal morphine on hemodynamic parameters in cardiac surgery patients.

METHODS

In a prospective, double-blind study, 100 adult cardiac surgical patients were randomized to receive either intrathecal 40 mg of 0.5% hyperbaric bupivacaine alone (intrathecal bupivacaine [ITB] group, n = 50) or intrathecal 250 µg of morphine added to 40 mg of 0.5% bupivacaine (intrathecal bupivacaine and morphine [ITBM] group, n = 50). Hemodynamic data, pain scores, rescue analgesic use, spirometry, and vasopressor use were recorded every four hours after surgery for 48 hr. The primary outcome was the incidence of vasoplegia in each group, which was defined as a cardiac index > 2.2 L·min-1·m-2 with the requirement of vasopressors to maintain the mean arterial pressure > 60 mmHg with the hemodynamic episode lasting > four hours.

RESULTS

Eighty-seven patients were analyzed (ITB group, n = 42, and ITBM group, n =45). The incidence of vasoplegia was higher in the ITBM group than in the ITB group [14 (31%) vs 5 (12%), respectively; relative risk, 2.6; 95% confidence interval [CI], 1.0 to 6.6; P = 0.04]. The mean (standard deviation [SD]) duration of vasoplegia was significantly longer in the ITBM group than in the ITB group [8.9 (3.0) hr vs 4.3 (0.4) hr, respectively; difference in means, 4.6; 95% CI, 3.7 to 5.5; P < 0.001].

CONCLUSION

Intrathecal morphine added to bupivacaine for high spinal anesthesia increases the incidence and duration of vasoplegia in cardiac surgery patients.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT02825056); registered 19 June 2016.

Effect of extracorporeal shock wave therapy on the treatment of patients with carpal tunnel syndrome

Background:

The carpal tunnel syndrome (CTS) is the most common neuropathy. The aim of this study was to evaluate the effect of a new and noninvasive treatment including extracorporeal shock wave therapy (ESWT) in the treatment of CTS.

Materials and Methods:

This study is a clinical trial conducted on 60 patients with moderate CTS in selected health centers of Isfahan Medical University from November 2014 to April 2015. Patients with CTS were randomly divided into two groups. Conservative treatment including wrist splint at night for 3 months, consumption of nonsteroidal anti-inflammatory drugs for 2 weeks, and oral consumption of Vitamin B1 for a month was recommended for both groups. The first group was treated with ESWT, one session per week for 4 weeks. Focus probe with 0.05, 0.07, 0.1, and 0.15 energy and shock numbers 800, 900, 1000, and 1100 were used from the first session to the fourth, respectively. The evaluated parameters were assessed before treatment and after 3 and 6 months. Data were analyzed using SPSS version 19, Student’s t-test, and Chi-square test.

Results:

All parameters were significantly decreased in the ESWT group after 3 months. These results remained almost constant after 6 months compared with 3 months after treatment. However, only two parameters considerably improved after 3 months of treatment in the control group. The entire indexes in the control group implicated the regression of results in long-term period.

Conclusion:

It is recommended to use ESWT as a conservative treatment in patients with CTS.

The effectiveness of extracorporeal shock wave therapy vs. local steroid injection for management of carpal tunnel syndrome: a randomized controlled trial

OBJECTIVE

Local corticosteroid (CS) injection has been widely used to treat carpal tunnel syndrome, but its invasiveness can cause several complications. In this study, the authors tested the efficacy of a new treatment method, extracorporeal shock wave therapy (ESWT), compared with CS injection.

DESIGN

The authors carried out a randomized controlled trial comparing one session of ESWT (1000 shots at the maximal tolerable intensity) with one session of CS injection in 36 patients with carpal tunnel syndrome. Outcome measures including nerve conduction studies, a visual analog scale, and the Levine Self-assessment Questionnaire were performed at baseline and at 1 and 3 mos after treatment.

RESULTS

At baseline, there were no significant differences between the groups with respect to the outcome parameters. Both groups showed a significant reduction in the visual analog scale at 1 and 3 mos after treatment compared with baseline. For the symptom severity score on the Levine Self-assessment Questionnaire, the ESWT group showed a significant reduction at 1 and 3 mos after treatment, whereas the CS injection group showed a significant reduction at 3 mos after treatment. For the nerve conduction parameters, there were mild but no significant improvements in the ESWT group, whereas the sensory nerve conduction velocity, the sensory nerve action potential amplitude, and the distal sensory and motor latencies of the median nerve were significantly improved in the CS injection group.

CONCLUSIONS

ESWT can be as useful as CS injection for relieving symptoms of carpal tunnel syndrome. Furthermore, in contrast to CS injection, it has the merit of being noninvasive.

Evaluation of analgesic effect of two different doses of fentanyl in combination with bupivacaine for surgical site infiltration in cases of modified radical mastoidectomy: A double blind randomized study

Background:

Limited evidence supports the efficacy of peripheral route fentanyl and local anesthetic combination for postoperative analgesia. Our study was therefore designed to demonstrate the analgesic efficacy of two different doses of fentanyl in combination with bupivacaine for surgical site infiltration in patients undergoing modified radical mastoidectomy (MRM).

Materials and Methods:

60 patients undergoing MRM under general anesthesia were randomly allocated into two groups, first group receiving 0.5% bupivacaine at a dose of 2 mg/kg body weight with 50 μg fentanyl and second group receiving bupivacaine 0.5% at a dose of 2 mg/kg body weight with 100 μg fentanyl as infiltration of operative field in and around the incision site, after the incision and just before completion of surgery. In postoperative period pain, nausea-vomiting and sedation was recorded at 0 hr, 2, 4, 6, 12 and 24 hrs.

Results:

Both the combinations of bupivacaine and fentanyl (Group I and Group II) were effective for postoperative analgesia. In both the groups the Visual Analogue Scale (VAS) score was less than 3 at each time interval. None of the patients required rescue analgesia. The comparison of VAS scores at different intervals showed that group II had lower VAS scores at all time points.

Conclusions:

Fentanyl and bupivacaine combinations in doses of 50 and 100 μg along with 0.5% bupivacaine at a fixed dose of 2 mg/kg body weight are effective in the management of postoperative pain. Patients who received 100 μg fentanyl (Group II) had lower VAS scores as compared to the patients who received 50 μg fentanyl (Group I) with similar side effects.

Calcium ions, morphine tolerance and noradrenergic transmission in the mouse vas deferens

The response of the isolated vas deferens of the mouse to electrical stimulation is inhibited by morphine and levorphanol via an opiate receptor, the inhibition decreasing with increasing stimulation frequency (0.2-16 Hz). Tolerance to the locomotor stimulant effect of morphine was induced over 48 h using a slow release preparation. Vasa from mice similarly treated with the slow release preparation showed a shift to the right of the morphine and levorphanol twitch inhibition curves. The reduction in the fractional release of [3H]noradrenaline by morphine and levorphanol was less in vasa from morphine-pretreated mice. Altering the Krebs solution by reducing the Ca2+ or Na+ or adding Mg2+ increased the effect of opiate agonists in vasa from naive and morphine-tolerant mice. Therefore, tolerance to morphine has not changed the ability of these ions to modulate opiate responses.

An electrophysiological analysis of the effects of morphine on the calcium dependence of neuromuscular transmission in the mouse vas deferens

1 The effects of morphine on the Ca-dependence of the synaptic potential amplitude in the mouse vas deferens have been determined. 2 The synaptic potential increased with a power factor of 2.4 for [Ca]o between 0.7 mM and 1.8 mM. Morphine (40 nM) decreased the synaptic potential, without altering the second power relationship between the synaptic potential and [Ca]o. 3 Morphine reversed the depression in the synaptic potential which develops during a short high-frequency (10 Hz) train of impulses to facilitation. Consequently the synaptic potential beyond the tenth impulse was unaffected by morphine. 4 Morphine did not alter the facilitation of the synaptic potential which develops during a short low-frequency (less than or equal to 2 Hz) train of impulses in normal [Ca]o. Consequently morphine decreased the synaptic potential for each impulse by about the same percentage amount. 5 Morphine increased the small facilitation in the synaptic potential which occurs during a short low-frequency (less than or equal to 2 Hz) train of impulses in high [Ca]o. This facilitation approximated the predictions based on the assumption that each impulse leaves residual Ca ions bound to receptors involved in transmitter release from the nerve terminal.

Analgesia produced by morphine when acting from the liquor space

1 In cats analgesia was produced by morphine sulphate introduced into different parts of the liquor space in doses too small to be effective on intravenous injection. Analgesia was measured with the tail pinch method of Russell & Tate (1975). 2 On infusion into the fourth ventricle or into the subarachnoid space beneath the ventral surface of the brain stem caudal to the pons, doses of 100 to 200 mug of morphine sulphate were sufficient to produce strong long-lasting analgesia. On injection into the cisterna magna somewhat larger doses (400 to 800mug) were required. 3 It is concluded that the site where morphine acts when producing analgesia in all three circumstances is at the ventral surface of the brain stem. 4 The possibility is discussed that the structures acted upon are tryptaminergic nerve fibres. They arise from the raphe nuclei, belong to a descending inhibitory pathway, and on their way to the spinal cord, reach the ventral surface of the brain stem lateral to each pyramid, where they could be reached and acted upon by the morphine. This theory postulates a morphine sensitivity of tryptaminergic nerve fibres.

Depression by morphine of excitatory junction potentials in the vas deferens of the mouse

1 Intracellular recordings were made from smooth muscle cells of the mouse vas deferens. Excitatory junction potentials (e.j.ps) were evoked by stimulation of the intramural nerves. 2 Normorphine (50 nM-5muM) depressed the amplitude of the e.j.p. The ED50 was 430 nM. The latency of the e.j.p. and the resting membrane potential of the smooth muscle cells were unaffected by normorphine. 3 The depression of the e.j.p. by narcotic analgesic drugs was stereospecific. 4 Naloxone (100 nM) completely reversed the depression of the e.j.p. produced by normorphine (1 muM). Naloxone (100 nM) alone did not alter the amplitude of the e.j.p. 5 Normorphine (1 muM) did not prevent the depolarization of the smooth muscle cells produced by exogenous noradrenaline (10 muM). 6 It is concluded that narcotic analgesic drugs act directly upon the transmitter release sites to reduce the amount of noradrenaline liberated by each nerve impulse.

Proceedings: Calcium influx into single crustacean muscle fibres as measured with a glass scintillator probe

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Effect of etorphine, morphine and diprenorphine on neurones of the cerebral cortex and spinal cord of the rat

1. The actions of etorphine, morphine and diprenorphine were investigated on neurones of the cerebral cortex and spinal cord of rats anaesthetized with pentobarbitone.2. In the cerebral cortex, intravenous etorphine increased the latency of the primary evoked response to a peripheral nerve stimulus and suppressed the rhythmical after-discharge. Diprenorphine reversed this effect. These actions were demonstrated on both field potentials and unit firing.3. Morphine had no effect on the primary response but the frequency of after-discharge bursts was reduced and there was an increase in firing between bursts.4. In the cerebral cortex, electrophoretically applied etorphine reduced after-discharges when applied for long periods but had no effect on the depressant actions of glycine and gamma-aminobutyric acid (GABA) nor on the excitant action of acetylcholine and L-glutamate. Similarly there was no alteration by etorphine of the effects of glycine, GABA and L-glutamate on spinal cord neurones.5. It is concluded that etorphine may act pre-synaptically in the cerebral cortex.

Excitatory action of sympathomimetic amines on 5-hydroxytryptamine receptors of gut

1. Twenty-two sympathomimetic amines were tested for excitatory activity on isolated guinea-pig ileum, rabbit jejunum, and rat stomach.2. Eight amines contracted all or almost all guinea-pig ileum preparations; five amines contracted half the preparations and relaxed the others. Nine amines were consistently relaxant. Structural requirements for excitatory activity were not clear.3. Six amines contracted rat stomach and only four contracted rabbit jejunum. Only beta-phenylethylamine and (-)-amphetamine contracted all three preparations.4. The excitatory effects of the sympathomimetic amines on guinea-pig ileum seem to be due to an action on 5-hydroxytryptamine receptors. This conclusion is based on evidence that their excitatory action is antagonized by 2-bromolysergic acid diethylamide, by morphine and by desensitization with 5-hydroxytryptamine, and that there is cross-protection between 5-hydroxytryptamine and the excitatory sympathomimetic amines against block by phenoxybenzamine.

Resting and action potentials recorded by the sucrose-gap method in the superior cervical ganglion of the rabbit

1. Evoked ganglionic action potentials and drug-induced changes in resting potential were recorded by the sucrose-gap method. The height of the action potential was 10-20 mV.2. Since the amplitude of the P wave is inversely proportional to the external potassium concentration between 0.5 and 12 mM, the P wave is probably caused by a phase of increased permeability to K(+).3. In the absence of an anticholinesterase, the depolarizing actions of choline and acetylcholine on the ganglion are almost equal, whereas acetylcholine is 2-3 times more potent than choline on the fibres of the internal carotid nerve. In the presence of eserine, acetylcholine induces a depolarization of the ganglion of up to 14 mV, while increase in [K(+)](o) causes a depolarization of up to 55 mV.4. Although the post-ganglionic fibres in the distal pole of the ganglion are depolarized by drugs, for example, acetylcholine, they contribute little to drug-induced potential changes and probably little to evoked action potentials.5. The hyperpolarization which occurs after exposure of the ganglion to acetylcholine is not due to a phase of increased permeability to K(+).