Muscular spasm in the lower limbs of laboring patients after intrathecal administration of epinephrine and sufentanil

Epinephrine reduces the sedative side effects of epidural sufentanil for labour analgesia

PURPOSE

The use of opioids in labour analgesia has primarily been as an adjuvant to local anesthetics. For early labour, satisfactory analgesia with epidural sufentanil alone is possible. This study evaluates the impact of epinephrine on sedative side effects and analgesia related to the latter technique.

METHODS

After Institutional Review Board approval and informed consent this prospective, randomized, double-blind study evaluated 43 nulliparous subjects requesting epidural analgesia. The study site, a tertiary care obstetric unit, accommodates 3500-4500 deliveries annually. Group selection was randomized and blinded by selection of a sealed envelope containing a number which corresponded to a premixed labelled syringe of saline or epinephrine (100 microg/mL). An epidural catheter was placed in a standardized fashion. All subjects received 40 microg of sufentanil and 0.5 mL from the premixed syringe, diluted to 10 mL with NaCl. A blinded observer collected data on maternal sedation, lightheadedness, hemodynamics, oxygenation, and fetal heart rate over a one-hour period following sufentanil injection.

RESULTS

The addition of epinephrine significantly (P <0.05) reduced the incidence of sedation and lightheadedness after epidural sufentanil at all data collection points, except two. Analgesic duration was also significantly prolonged by this addition (120 +/- 56 vs 84 +/- 32 min). Maternal satisfaction was high regardless of solution.

CONCLUSION

Forty micrograms of epidural sufentanil produces satisfactory analgesia in early labour. The addition of epinephrine improves the side effect profile of this technique while prolonging the duration of analgesia. Epidural sufentanil requires attention to maternal monitoring of oxygenation as maternal desaturation occurred in both groups.

Reversible Spastic Paraparesis Induced by High-Dose Intravenous Methadone

High doses of parenteral opioids can cause multifocal myoclonus and seizures. Spasticity has been reported in patients receiving intraspinal opioids. In this article, we describe a patient who developed reversible spastic paraparesis with prominent extensor spasms in the legs while receiving an infusion of intravenous methadone at 100 mg/hr. We discuss clinical presentation and possible pathophysiologic mechanisms of opioid side effects on the somatic motor system.

Promising non-narcotic analgesic techniques for labour

Epidural analgesia and spinal analgesia are the most effective techniques for relieving labour pain. Basically, local anaesthetics (i.e. bupivacaine) and opioids (i.e. fentanyl or sufentanil), especially when combined, produce excellent analgesia with minimal motor blockade. However, none of these agents is devoid of side-effects and analgesia remains sometimes imperfect, suggesting that new drugs would be welcome. Adrenalin and clonidine act on a2-adrenoceptors in the spinal cord and both have been found to improve analgesia. These two drugs have already been used in many patients and studies because the absence of neurotoxicity has been well documented. Clonidine looks more attractive, although sedation and hypotension limit its use. Other analgesic drugs are promising alternatives but are still at an experimental or very early clinical stage. Neostigmine and ketamine (without preservative) are not neurotoxic while midazolam neurotoxicity is still controversial. Intravenous remifentanil might prove useful when neuraxial analgesia is contraindicated.

Intrathecal labor analgesia: can we use the same mixture as is used epidurally?

In a randomized double-blind study, three groups of 25 term parturients received one of the following intrathecal drugs or combinations for relief of labor pain: sufentanil 7.5 microg (1.5 ml), sufentanil 5 microg + bupivacaine 1 mg (1.5 ml) or the combination bupivacaine 1.75 mg, sufentanil 1.05 microg and epinephrine 1.75 microg, that is 1.5 ml of our standard epidural mixture. After the intrathecal injection, patients received a peridural catheter for supplementation of analgesia. Onset and duration of the three regimens were similar. Analgesia lasted for approximately 95-115 minutes which was similar to durations obtained with the subsequent epidural top-ups. Pruritus was observed significantly less frequently in the group treated intrathecally with the epidural mixture. The incidence of other maternal side-effects was extremely low and not different among the groups. Instrumental delivery, Apgar scores and umbilical blood gases were identical. More cardiotocographic changes were observed in the plain sufentanil group but this was not related to neonatal outcome. It was concluded that intrathecal injection of the standard epidural mixture offers effective and long-lasting analgesia. This may avoid side-effects and complications, manipulations of drugs with the risk for contamination, spilling of drugs and loss of time.

Determination of the dose-response relationship for intrathecal sufentanil in laboring patients

Multiple studies have investigated the efficacy of intrathecal opioids, particularly sufentanil, in laboring parturients. However, until the important pharmacological indices of the 50% and 95% effective doses (ED50 and ED95, respectively) are defined, reliable comparative studies among drugs at equipotent doses cannot be performed. This study was performed to establish the dose-response relationship of intrathecal sufentanil analgesia in labor. Sixty parturients presenting in active labor received intrathecal sufentanil 2.5 (n = 10), 5.0 (n = 10), 7.5 (n = 10), 10.0 (n = 10), 12.5 (n = 10), or 15.0 (n = 10) microg in a blind, randomized fashion. Patient 100-mm visual analog pain scale (VAS) scores, fetal heart rate (FHR), blood pressure, and heart rate were recorded at 0, 1, 5, 10, 15, 20, 25, and 30 min after administration of sufentanil and then again when the patient requested additional analgesia. Absolute VAS < or =25 mm was considered an analgesic success. Percent responders was used to construct a dose-response curve and calculate ED50 and ED95. The ED50 and ED95 for intrathecal sufentanil in laboring parturients were 2.6 (1.8-3.2, 95% confidence interval) and 8.9 (7.5-11.5) microg, respectively. There was a trend toward increasing analgesic duration with increasing sufentanil dose. The maternal side effect profile was not different among groups. FHR did not appreciably change for any group or individual studied. Assisted delivery and cesarean section rates were similar for all groups. Intrathecal sufentanil provides rapid onset of analgesia for labor. The ED50 and ED95 values established in this study should help to provide benchmarks both for the safe clinical use of intrathecal sufentanil for labor and for future comparison studies with other intrathecal analgesic techniques.

[Neurotoxicity of intrathecally administrated agents]

Spinal anaesthetics can induce histopathologic lesions and regional haemodynamic alterations in the spinal cord. There are numerous causes of neurologic lesions, including direct trauma of the spinal cord and nerve roots during puncture or catheter insertion, compromised spinal cord perfusion and direct neurotoxic effect. Histopathologic lesions are localized either in meninges (meningitis or arachnoiditis) or in neuraxis (myelitis or axonal degeneration). Neurotoxicity can result from decrease in neuronal blood supply, elicited by high concentrations of the solutions, long duration exposure to local anaesthetics, and the use of adjuvants. They have been implicated in the occurrence of cauda equina syndrome after continuous spinal anaesthesia using hyperbaric solution of lidocaine and tetracaine given through small diameter catheters. Selective spinal analgesia is induced by spinal opioids without motor blockade except for meperidine. Complications occurred in patients after high doses of morphine, which were related to one of its metabolites, morphine-3-glucuronide. Preservative-free opioid solutions are to be preferred for spinal anaesthesia. There is no report of neurotoxicity neither in animal studies, nor in humans, using spinal clonidine. In order to reduce the incidence of neurotoxicity, some safety rules should be followed. The lowest efficient dose of local anaesthetics must be given. Incomplete blockade should not necessarily lead to a reinjection. Large volume of hyperbaric lidocaine or repeated injections of such solutions must be avoided as well as preservative-containing solutions. The administration of new compounds by the spinal route must be supported by data of spinal neuropharmacology and the lack of neurotoxicity must have been previously checked with animal studies.

Side effects of intrathecal and epidural opioids

The purpose of this article is to review the literature on the side effects of intrathecal and epidural opioids. English-language articles were identified through a MEDLINE search and through review of the bibliographies of identified articles. With the increasing utilization of intrathecal and epidural opioids in humans during the 1980s, a wide variety of clinically relevant side effects have been reported. The four classic side effects are pruritus, nausea and vomiting, urinary retention, and respiratory depression. Numerous other side effects have also been described. Most side effects are dose-dependent and may be more common if the opioid is administered intrathecally. Side effects are less common in patients chronically exposed to either intrathecal, epidural, or systemic opioids. Some side effects are mediated via interaction with specific opioid receptors while others are not. It is concluded that the introduction of intrathecal and epidural opioids marks one of the most important breakthroughs in pain management in the last two decades. However, a wide variety of clinically relevant non-nociceptive side effects may occur. All physicians utilizing intrathecal and epidural opioids must be aware of these side effects, for while most are minor, others are potentially lethal.