Spinal Clonidine Prolongs Labor Analgesia from Spinal Sufentanil and Bupivacaine

Outcomes of intrathecal analgesia in multiparous women undergoing normal vaginal delivery: A randomised controlled trial

Background and Aims

Although intrathecal analgesia is an effective option during labour, there is a need to establish sustainable and assured analgesia during the entire labour process. We aimed to assess the effect of adding dexmedetomidine, fentanyl or morphine to low-dose bupivacaine-dexamethasone for intrathecal labour analgesia in multiparous women.

Methods

This was a triple-blind, randomised controlled trial that included 140 multiparous women. Eligible women were randomly allocated to have intrathecal bupivacaine-dexamethasone with dexmedetomidine (group D), fentanyl (group F), morphine (group M) or saline (placebo) (group C). The duration of analgesia, intrathecal block characteristics and maternal and foetal outcomes were assessed and analysed.

Results

The longest analgesia duration and S1 regression time was recorded in group D followed by groups M, F and C, respectively, with statistical significance between all of them (P < 0.001). The shortest analgesia onset time and the highest sensory levels were recorded in group D followed by group F then group M with statistical significance between all of them (P < 0.001 and 0.003, respectively). Visual analogue scale values were comparable among groups M, F and D (P > 0.05) at most of the measurement time points and at the peak of the last uterine contraction before delivery while being significantly lower than those in group C (P < 0.001). However, there were similar motor block characteristics and normal neonatal outcomes in all groups.

Conclusion

In comparison to morphine and fentanyl, dexmedetomidine addition to intrathecal bupivacaine-dexamethasone significantly prolonged the duration and accelerated the onset of labour analgesia, with a good maternal and neonatal outcome.

Effect of epidural clonidine on characteristics of spinal anaesthesia in patients undergoing gynaecological surgeries: A clinical study

Background and Aims:

Combined spinal–epidural (CSE) anaesthesia is being increasingly used for effective post-operative analgesia. This study was designed to evaluate the effect of epidural clonidine on characteristics of spinal anaesthesia for gynaecological surgeries.

Methods:

This was a prospective randomised, double-blind, controlled study involving sixty patients belonging to American Society of Anesthesiologists Physical Status I and II who underwent gynaecological surgeries were randomly divided into clonidine (C) group and saline (S) group of thirty each. All patients received CSE anaesthesia. Ten minutes before subarachnoid block (SAB), Group C received clonidine 150 μg diluted to 5 ml in normal saline (NS) and Group S received NS epidurally. Hyperbaric bupivacaine (15 mg) was administered intrathecally for both groups after epidural injection. Sensory and motor block characteristics, analgesia, sedation and haemodynamics were observed. Statistical analysis was performed using appropriate tests.

Results:

Epidural clonidine produced faster onset (37.83 ± 8.58 s in Group C compared to 50.33 ± 8.80 s in Group S, P = 0.001) and prolonged duration of sensory block (241.17±18.65 minutes in group C compared to 150.33±19.16 minutes in group S, P = 0.001). Time for two segment regression of sensory block was193.67 ± 19.82 min in Group C and 109.33 ± 18.56 min Group S (P < 0.001). The duration of analgesia was 299.00 ± 43.38 min in Group C and 152.50 ± 21.04 min in Group S (P < 0.001). Haemodynamics and sedation scores were comparable between two groups.

Conclusion:

Administration of clonidine epidurally, 10 min before SAB, caused early onset and prolonged duration of motor blockade and analgesia, without any significant post-operative complication.

Analgesic and sympatholytic effects of low-dose intrathecal clonidine compared with bupivacaine: a dose-response study in female volunteers

BACKGROUND

A wide range of doses has been suggested for intrathecal clonidine, but no dose-ranging study has examined analgesic effects below 100 µg. The primary aim of this volunteer study was to assess the dose vs analgesic effect relationship for doses of intrathecal clonidine below 100 µg.

METHODS

After IRB approval and signed informed consent, 11 healthy female volunteers participated in this randomized, double-blinded, cross-over study using a dose-ranging sparse-sampling technique. Participants received intrathecal clonidine (doses 0-100 µg; n=10) and intrathecal bupivacaine (doses 0-8.8 mg; n=9) on separate study days. At baseline, 30, and 60 min from drug administration, experimental heat pain tolerance was assessed at both a lumbar and a cranial dermatome. Heat and cold perception thresholds were assessed at the same time intervals. Heart rate (HR), arterial pressure, and forearm-finger and toe-leg cutaneous temperature gradients (Tfinger-arm and Ttoe-leg) were used as measures of sympatholysis.

RESULTS

Both intrathecal clonidine and bupivacaine caused significant, dose-dependent analgesic effects at the leg but not the head. Significant analgesia to experimental heat pain was detected above 25 µg clonidine and 3 mg bupivacaine. Administration of bupivacaine but not clonidine resulted in a significant dose-related decrease in HR and Ttoe-leg; neither drug caused dose-related sympatholytic effects in the doses used.

CONCLUSIONS

After 50 µg clonidine or 5 mg bupivacaine, the heat pain tolerance increased by ∼1°C, similar to the analgesic effect of 5 mg epidural morphine or 30 µg epidural fentanyl in previous studies using this experimental heat pain model. Our results provide additional data for rational dose selection of intrathecal clonidine.

Intrathecal clonidine in the neonatal rat: dose-dependent analgesia and evaluation of spinal apoptosis and toxicity

BACKGROUND

Neuraxial clonidine is used for perioperative analgesia in children of all ages. Preclinical studies in the postnatal rat allow comparison of the relative toxicity and safety of spinal analgesics throughout postnatal development.

METHODS

Rat pups aged 3, 7, or 21 postnatal (P) days were briefly anesthetized for intrathecal injections of saline or clonidine. At each age, the maximum tolerated, antinociceptive (increased hindlimb mechanical withdrawal threshold) and antihyperalgesic (hindpaw carrageenan inflammation) doses were determined. Lumbar spinal cord sections were assessed for apoptosis and cell death (histology, activated caspase-3 immunohistochemistry, Fluoro-Jade C staining), histopathology (hematoxylin and eosin staining), and increased glial reactivity (microglial and astrocytic markers). P3 intrathecal ketamine sections served as positive controls. In additional groups, thermal latency and mechanical withdrawal threshold were measured at P35.

RESULTS

Intrathecal clonidine produces age- and dose-dependent analgesia in rat pups. Maximal doses of clonidine did not alter the degree or distribution of apoptosis or increase glial reactivity in the neonatal spinal cord. No spinal histopathology was seen 1 or 7 days after injection at any age. Intrathecal clonidine did not produce persistent changes in reflex sensitivity to mechanical or thermal stimuli at P35.

CONCLUSIONS

Intrathecal clonidine in the postnatal rat did not produce signs of spinal cord toxicity, even at doses much larger than required for analgesia. The therapeutic ratio (maximum tolerated dose/antihyperalgesic dose) was >300 at P3, >30 at P7, and >10 at P21. These data provide additional information to inform the clinical choice of spinal analgesic drug in early life.

Effects of a continuous low-dose clonidine epidural regimen on pain, satisfaction and adverse events during labour: a randomized, double-blind, placebo-controlled trial

BACKGROUND AND OBJECTIVE

Epidural clonidine has been proposed as an adjunct for anaesthetic mixtures during labour. Administered as a bolus, clonidine may have side effects such as sedation and hypotension; its continuous infusion could be attractive in this respect. We, therefore, conducted a randomized, double-blind trial using patient-controlled epidural analgesia with a background infusion using a low dose of clonidine during labour.

METHODS

A total of 128 healthy parturients in active labour received a patient-controlled epidural analgesia solution of 0.0625% levobupivacaine and sufentanil 0.25 microg ml(-1) with or without clonidine 2 microg ml(-1). Ninety-five parturients were analysed. The pain score over time was evaluated as well as drug volume utilization; supplementation bolus and side effects were recorded. The primary endpoint was maternal satisfaction [ClinicalTrials.gov Identifier (NCT00437996)].

RESULTS

Three patients in the control group failed to achieve satisfactory epidural analgesia owing to a technical issue. Although the primary endpoint was not statistically significant, analgesia was more pronounced and obtained earlier in the clonidine group. The area under the curve for the visual analogue pain score was significantly lower in the clonidine group. In this group, hourly doses of levobupivacaine and sufentanil were reduced (13.9 +/- 4.3 vs. 16.3 ml +/- 4.0; P = 0.005) as well as rescue supplementation and pruritus incidence (18 vs. 46%; P = 0.004). Maternal blood pressure was significantly lower, over time, in the clonidine group but remained within the normal range. Sedation was similar in both groups (4.3 vs. 2.0%; not significant).

CONCLUSION

The addition of clonidine to epidural levobupivacaine and sufentanil for patient-controlled epidural analgesia in labour improved analgesia, reduced the supplementation rate and reduced pruritus without improvement in maternal satisfaction. Blood pressure was significantly lower in the clonidine group over time but without clinical consequence.

Pharmacological profiles of alpha 2 adrenergic receptor agonists identified using genetically altered mice and isobolographic analysis

Endogenous, descending noradrenergic fibers impose analgesic control over spinal afferent circuitry mediating the rostrad transmission of pain signals. These fibers target alpha 2 adrenergic receptors (alpha(2)ARs) on both primary afferent terminals and secondary neurons, and their activation mediates substantial inhibitory control over this transmission, rivaling that of opioid receptors which share a similar pattern of distribution. The terminals of primary afferent nociceptive neurons and secondary spinal dorsal horn neurons express alpha(2A)AR and alpha(2C)AR subtypes, respectively. Spinal delivery of these agents serves to reduce their side effects, which are mediated largely at supraspinal sites, by concentrating the drugs at the spinal level. Targeting these spinal alpha(2)ARs with one of five selective therapeutic agonists, clonidine, dexmedetomidine, brimonidine, ST91 and moxonidine, produces significant antinociception that can work in concert with opioid agonists to yield synergistic antinociception. Application of several genetically altered mouse lines had facilitated identification of the primary receptor subtypes that likely mediate the antinociceptive effects of these agents. This review provides first an anatomical description of the localization of the three subtypes in the central nervous system, second a detailed account of the pharmacological history of each of the six primary agonists, and finally a comprehensive report of the specific interactions of other GPCR agonists with each of the six principal alpha(2)AR agonists featured.

[30 microg intrathecal clonidine prolongs labour analgesia, but increases the incidence of hypotension and abnormal foetal heart rate patterns]

OBJECTIVE

To assess the efficacy of spinal clonidine combined with bupivacaine and sufentanil and its effects on maternal and foetal outcome.

STUDY DESIGN

Prospective double-blind randomized study.

PATIENTS AND METHODS

One hundred and five patients requesting labour analgesia had combined spinal epidural analgesia with intrathecal bupivacaine 2.5 mg and were randomly assigned to receive in addition either sufentanil 5 microg (S5), sufentanil 5 microg and clonidine 30 microg (C30), or sufentanil 10 microg (S10). Onset time, duration of analgesia, visual analogue scores, blood pressure, ephedrine requirements, heart rate, nausea, pruritus, sedation, motor block, foetal heart rate abnormalities, mode of delivery and Apgar scores were recorded.

RESULTS

Mean duration of spinal analgesia was significantly longer in patients receiving spinal clonidine compared to patients in S5 group (144+/-61 min versus 95+/-37 min). The onset time of analgesia was significantly shorter in S10 group (3+/-1 min) versus C30 group (4+/-1 min) and S5 group (4+/-1 min) (P=0.002). Hypotension was significantly more frequent in C30 group (29 versus 3% and 3% in S5 and S10 groups) (p=0,001). Foetal heart rate abnormalities and sedation were also significantly more frequent in C30 group. Mode of delivery (spontaneous, instrumental or caesarean delivery) and Apgar scores were unaffected by clonidine treatment.

CONCLUSION

Intrathecal clonidine 30 mug prolongs analgesia. However, it increases the incidence of hypotension, and abnormal foetal heart rate patterns. Thus, this study confirms that the use of 30 mug intrathecal clonidine for labour analgesia is not recommended.

Intrathecal sufentanil (1.5 microg) added to hyperbaric bupivacaine (0.5%) for elective cesarean section provides adequate analgesia without need for pruritus therapy

PURPOSE

We compared the effects of different doses of intrathecal sufentanil when administered together with hyperbaric bupivacaine for elective caesarean section.

METHODS

This was a prospective, randomized, double-blind, controlled trial involving 100 pregnant women, American Society of Anesthesiologists (ASA) I-II, who were scheduled for elective caesarean section under spinal anesthesia. The patients were assigned to four groups according to the dose of sufentanil used: no sufentanil (group I; placebo) or 1.5, 2.5, or 5.0 microg sufentanil (groups 2-4, respectively). In every group, the local anesthetic used was hyperbaric bupivacaine 0.5% (12.5 mg), and the total volume of the solution was 3.5 ml. The duration of complete analgesia, maternal side effects, and maternal/fetal outcomes were recorded. The duration of complete analgesia was defined as the time from intrathecal injection to a vernal analogue score (VAS) of more than 0.

RESULTS

No patient experienced intraoperative pain. The duration of complete analgesia was prolonged in all groups receiving opioids. The duration of the analgesia and the 0- to 6-h intravenous analgesic requirements were similar in the sufentanil groups. Moreover, the sufentanil groups had longer durations of complete analgesia than the placebo group. Pruritus was more frequent in the 2.5- and 5-microg sufentanil groups than in the 1.5-microg sufentanil and placebo groups. There were no differences among the groups in umbilical cord blood gases on in neonatal Apgar scores.

CONCLUSION

The addition of sufentanil 1.5 and 2.5 microg to hyperbaric bupivacaine provided adequate anesthesia for caesarean delivery and good postoperative analgesia. In addition, the incidence of pruritus was significantly lower in the 1.5-microg sufentanil group when compared with that in the 2.5- and 5-microg groups.

The use of neuraxial adjuvant drugs (neostigmine, clonidine) in obstetrics

PURPOSE OF REVIEW

Neuraxial adjuvant drugs are used to improve analgesia and to decrease complications associated with a high dose of a single drug. Opioids are used in routinely, but alpha2-agonists, such as clonidine or cholinesterase inhibitors (neostigmine), have also been used for labour analgesia or to relieve pain following caesarean section. Both drugs possess a common mechanism of action that can be beneficial.

RECENT FINDINGS

Small doses of intrathecal clonidine (30 microg), combined with local anaesthetics and opioids, prolong labour analgesia. Hypotension can occur and must be promptly treated by ephedrine to avoid fetal side effects. Epidural clonidine (60 to 75 microg) produces prolonged analgesia from local anaesthetics and opioids and allows a ropivacaine sparing effect. Intrathecal neostigmine has analgesic properties, but its gastro-intestinal side effects contraindicate its clinical use. Epidural neostigmine, combined with sufentanil or clonidine, initiates labour analgesia (minimum 6 to 7 microg/kg; 500 microg) without side effects, however, and allows a 'mobile epidural'. Epidural and spinal clonidine can be used to improve postcaesarean section analgesia. Epidural neostigmine at the doses studied produces modest analgesia following caesarean section.

SUMMARY

Co-administration of neuraxial drugs may enhance analgesia and reduce the side effects of each drug. Clonidine and neostigmine may be used in obstetrics, under some conditions.

Prophylactic Ephedrine and Combined Spinal Epidural

OBJECTIVE

Labor analgesia with the combined spinal epidural approach has been associated with maternal hypotension and fetal heart rate (FHR) changes. The purpose of this study was to estimate whether prophylactic intramuscular ephedrine before combined spinal epidural prevents these complications.

METHODS

In a prospective double blind trial, 100 healthy patients with term singletons received intramuscular ephedrine 25 mg or placebo by random allocation before combined spinal epidural. During the first hour after analgesia, maternal heart rate, blood pressure, and need for treatment of significant hypotension were recorded. Fetal heart rate tracings for 1 hour before and for 1 hour after administration of anesthetic were evaluated. Categorical variables were compared with Fisher exact test. Continuous variables were compared with one way analysis of variance for repeated measures. P < .05 was considered significant.

RESULTS

Prophylactic ephedrine reduced the incidence of maternal hypotension after combined spinal epidural (P < .007). In controls, there was a significant increase in the incidence and frequency of late decelerations in the hour following combined spinal epidural compared with the previous hour (P < .005 and P < .01). Compared with controls, there was an increased incidence of fetal tachycardia in patients who received prophylactic ephedrine (P < .006), which was associated with increased FHR reactivity (P < .03).

CONCLUSION

Although prophylactic ephedrine prevents maternal hypotension and fetal late decelerations, it is associated with fetal tachycardia. The value of prophylactic ephedrine at combined spinal epidural should be weighed against potential changes in fetal heart rate patterns.

LEVEL OF EVIDENCE

I.

Epidural analgesia for childbirth: effects of newer techniques on neonatal outcome

New low-dose, local anesthetic-opioid combinations, combined spinal epidural analgesia, and new anesthetic drugs, such as ropivacaine and levobupivacaine, have modified the anesthetic practice in obstetric labor analgesia. These new analgesic techniques have less or no neonatal effects when compared with traditional epidural labor analgesia. They also have less effect on mode of delivery, which may in turn affect neonatal outcome. The use of very diluted or low concentrations of local anesthetic solutions may reduce their placental passage and thus the possible subtle neonatal effects. Small doses of epidural or spinal opioids alone or combined with low doses of local anesthetics does not affect the well-being of the neonate at birth. When considering the neonatal outcome, combined spinal epidural analgesia is as well tolerated as low-dose epidural analgesia. Transient fetal heart rate changes have been described immediately after the administration of intrathecal or epidural opioids. Maternal hypotension may also occur at the onset of epidural analgesia. Whether the occurrence of transient fetal heart rate changes or maternal hypotension immediately after the epidural block may influence the neonatal outcome at birth needs verification.

Intrathecal clonidine prolongs labour analgesia but worsens fetal outcome: a pilot study

PURPOSE

Intrathecal clonidine prolongs total duration of spinal bupivacaine analgesia. However, there are contradictory reports about its effect on maternal blood pressure and only limited data are available on fetal and neonatal outcome. In this study, we evaluated the efficacy of spinal clonidine combined with ropivacaine and sufentanil and its effects on maternal and fetal outcome.

METHODS

Fifty patients requesting combined spinal epidural analgesia for labour pain relief were randomly assigned to receive intrathecal ropivacaine 3 mg, sufentanil 1.5 microg with or without clonidine 30 microg. Onset time and duration of analgesia, visual analogue scores for pain, blood pressure, ephedrine requirements, heart rate, incidence of nausea, pruritus and motor blockade, umbilical artery pH, fetal heart rate abnormalities and Apgar scores were noted and analyzed.

RESULTS

Patients receiving spinal clonidine had significantly longer lasting analgesia compared to patients treated without clonidine (122 +/- 56 min vs 90 +/- 36 min, P < 0.05). Clonidine-treated patients experienced a more pronounced decrease in mean arterial pressure as compared to patients treated without clonidine (25 +/- 10% vs 15 +/- 12%, P < 0.05). The groups also differed in ephedrine requirement (4.91 mg vs 0.75 mg, P < 0.05), number of new onset fetal heart rate abnormalities (28% vs 0%, P < 0.05) and umbilical artery pH (7.219 +/- 0.096 vs 7.289 +/- 0.085, P < 0.05).

CONCLUSION

Intrathecal clonidine prolongs spinal analgesia with ropivacaine and sufentanil at the expense of maternal hypotension, worse fetal well being and worse neonatal umbilical artery pH. We do not recommend routine administration of spinal clonidine 30 microg to sufentanil and ropivacaine for labour pain relief.

Stability of clonidine in clonidine-hydromorphone mixture from implanted intrathecal infusion pumps in chronic pain patients

Clonidine is frequently added to opioids in implantable intrathecal pumps for the management of chronic pain. In such devices, a small non-retrievable volume is always present in the reservoir, and its effect on drug stability is unknown. Furthermore, stability of clonidine, when mixed with hydromorphone, has not been previously determined. This study examined the stability of clonidine when co-administered with hydromorphone in implanted intrathecal pumps. Samples of hydromorphone-clonidine before pump refill and from residual solution at subsequent refill were obtained from chronic pain patients. Clonidine concentration was measured using HPLC. Twenty paired samples from 3 patients were analyzed. All 3 patients had a SynchroMed pump implanted for 3-5 years. We found no loss in clonidine concentration during the time between refills (35 +/- 13 days), and no correlation between clonidine concentration and time interval between refills. In conclusion, clonidine, mixed with hydromorphone, is stable when delivered by implantable intrathecal pump for long-term use.

The caudal ventrolateral medulla as an important inhibitory modulator of pain transmission in the spinal cord

The caudal ventrolateral medulla (VLM) has emerged during the last decade as one of the main components of the endogenous pain control system. Profound and long-lasting analgesia is produced by mild stimulation of the VLM. The VLMlat, the reticular formation located between the spinal trigeminal nucleus and the lateral reticular nucleus (LRt), appears to play a major role in that antinociceptive action. The projections to spinal cord laminae involved in nociceptive transmission originate exclusively in the VLMlat. The VLMlat participates in a disynaptic pathway involving spinally projecting pontine A5 noradrenergic neurons, which appears to convey alpha(2)-adrenoreceptor-mediated analgesia produced from the VLM. Neurons in the VLMlat and in lamina I are reciprocally connected by a closed loop that is likely to mediate feedback control of supraspinal nociceptive transmission. On the other hand, the LRt, which is targeted by ventral (lamina VII) and deep dorsal (laminae IV to V) horn inputs, projects to the premotor lamina VII. Nociceptive input ascending from the cord and increases in blood pressure are discussed as possible physiologic triggers of the analgesia produced by the VLM. The overall role of the VLM as a center for integration of nociceptive, cardiovascular, and motor functions is discussed. The putative therapeutic benefits of manipulating the VLM for the control of chronic pain are envisaged.

Intrathecal opioids for combined spinal-epidural analgesia during labour

In <25 years, intrathecal administration of opioids (i.e. spinal analgesia) has evolved from an experimental model into an important therapy for obstetric analgesia and anaesthesia. A small dose of opioid delivered into the CSF provides almost immediate relief from labour pain with minimal risks to the mother and fetus. Careful attention, and prompt treatment when needed, can ameliorate the adverse effects of fetal bradycardia, respiratory depression and pruritus. The major limitation of intrathecal opioids for labour analgesia is the short duration of effect: 90-180 minutes under ideal circumstances. To address this problem, and to increase flexibility for anaesthesia as well as analgesia, the combined spinal-epidural (CSE) technique was developed. The CSE technique involves injection of drugs into the CSF and placement of an epidural catheter. An intrathecally administered opioid provides a rapid onset of labour analgesia without motor block or significant haemodynamic perturbation. The epidural catheter allows ongoing administration of medications to maintain labour analgesia and provides a means of delivering anaesthesia for operative delivery. This review will focus on intrathecally administered opioids as used as part of CSE analgesia. Considerable research has focused on the optimum dose of opioids when delivered intrathecally, with or without adjuncts, in the CSE technique. Fentanyl and sufentanil, two of the lipophilic synthetic opioids, have emerged as the most useful. Bupivacaine, a long-acting local anaesthetic, is often added to prolong the duration of analgesia, although this tends to increase the likelihood of motor blockade of the lower extremities. Comparisons of the CSE technique with standard epidural practices have shown that both are effective means of providing analgesia during labour. Controversy revolves around the incidence of fetal bradycardia following CSE and whether this phenomenon increases the rate of operative deliveries. The rapid onset of analgesia with intrathecally administered opioids must be balanced against the added risks of dural puncture and considered in the context of the whole duration of labour. Ultimately, the decision to choose a CSE technique depends on the experience of the anaesthesia provider and the local availability of drugs, equipment and monitoring capabilities.

A randomized, double-blinded trial of subarachnoid bupivacaine and fentanyl, with or without clonidine, for combined spinal/epidural analgesia during labor

Subarachnoid clonidine may increase the duration of spinal opioid and local anesthetic analgesia during labor, but it may also increase hypotension and sedation, and the therapeutic range is unclear. We studied 110 term parturients of mixed parity having combined spinal/epidural analgesia during labor in this randomized, double-blinded trial. All received subarachnoid fentanyl 20 micro g and bupivacaine 2.5 mg, plus either saline or clonidine (15, 30, or 45 micro g). Of 101 per-protocol parturients (n = 25, 24, 26, and 26 in Groups C0, C15, C30, and C45, respectively), 22 delivered before the cessation of spinal analgesia. Group demographics and pain scores from Time 0 to 120 min were similar. There was no significant difference among groups in the duration of spinal analgesia (P = 0.09) or in the duration of clonidine groups combined compared with control (median, 120 min [interquartile range, 96-139 min] versus 98 min [80-120 min]; P = 0.07). Systolic blood pressure was significantly lower in all clonidine groups between 40 and 90 min (P = 0.001). Hypotension (P = 0.05) and the requirement for ephedrine (P = 0.02) were dose dependent, but groups had a similar incidence of hypotension. The addition of clonidine 15-45 micro g to subarachnoid fentanyl and bupivacaine reduced blood pressure and did not significantly increase the duration of spinal analgesia.

IMPLICATIONS

The addition of 15-45 micro g of clonidine to subarachnoid fentanyl plus bupivacaine did not significantly increase the duration of spinal analgesia but did decrease maternal blood pressure. The results of this study do not support the use of subarachnoid clonidine to prolong the action of spinal labor analgesia when fentanyl plus bupivacaine are administered.

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

BACKGROUND

We compared analgesia after intrathecal sufentanil alone, sufentanil with epinephrine 200 microg and sufentanil with clonidine 30 microg in patients after total hip replacement, the endpoints being onset and duration of action.

METHODS

We performed a randomized double-blind study of 45 patients for elective total hip arthroplasty using continuous spinal anaesthesia. As soon as a pain score higher than 3 on a 10 cm visual analogue scale was reported, sufentanil 7.5 microg alone, sufentanil 7.5 microg + epinephrine 200 microg or sufentanil 7.5 microg + clonidine 30 micro g in 2 ml normal saline was given intrathecally. Pain scores, rescue analgesia (diclofenac and morphine) and adverse effects (respiratory depression, postoperative nausea and vomiting, itching) were observed for 24 h after surgery.

RESULTS

Time to a pain score of <3 [6 (SD 1) vs 6 (1) vs 5 (1) min], time to the lowest pain score [7 (2) vs 8 (2) vs 8 (2) min] and time to the first dose of systemic analgesic for a pain score >3 [281 (36) vs 288 (23) vs 305 (30) min] were similar in all three groups. Adverse effects and analgesic requirements during the first 24 h were also similar.

CONCLUSION

After total hip replacement, all three analgesic regimens gave good analgesia with comparable onset and duration of action, and minor adverse effects.

Intrathecal magnesium prolongs fentanyl analgesia: a prospective, randomized, controlled trial

Magnesium is a noncompetitive, N-methyl-D-aspartate receptor antagonist that does not effectively cross the blood-brain barrier when given IV. Intrathecal magnesium potentiates opioid antinociception in rats, and the safety of intrathecal magnesium has been demonstrated in animals. This is the first prospective human study evaluating whether intrathecal magnesium could prolong spinal opioid analgesia. Fifty-two patients requesting analgesia for labor were randomized to receive either intrathecal fentanyl 25 micro g plus saline or fentanyl 25 micro g plus magnesium sulfate 50 mg as part of a combined spinal-epidural technique. The duration of analgesia of the intrathecal drug combination was defined by the time of patient request for additional analgesia. There was significant prolongation in the median duration of analgesia (75 min) in the magnesium plus fentanyl group compared with the fentanyl alone group (60 min). There was no associated increase in adverse events in the group that received intrathecal magnesium. Larger doses of intrathecal magnesium were not studied in this group of patients because of the limitations on cephalad spread when hyperbaric solutions are injected in the sitting position. Our data indicate that intrathecal magnesium prolongs spinal opioid analgesia in humans and suggest that the availability of an intrathecal N-methyl-D-aspartate antagonist could be of clinical importance for pain management.

IMPLICATIONS

Magnesium occurs naturally in the spinal cord and blocks the NMDA glutamate channel. In animal studies, intrathecal magnesium sulfate improves spinal morphine analgesia. For patients receiving spinal analgesia for labor, the addition of magnesium sulfate to the opioid fentanyl prolonged analgesia with no increase of side effects.

Electrophysiologic characterization of the antinociceptive actions of S18616, a novel and potent alpha2-adrenoceptor agonist, after acute and persistent pain states

alpha (2)-Adrenoceptor (AR) agonists are active in behavioral models of persistent pain involving tissue and nerve damage. We evaluated the spinal effect of a novel, potent, and selective alpha (2)-AR agonist, [7,8](2-chlorobenzo)-2-amino-1-aza-3-oxa[4,5]spirodeca-1,7-diene (S18616), on the responses of dorsal horn neurons in halothane-anesthetized rats. Intrathecal administration of S18616 (0.1 to 3.0 microg) dose-dependently suppressed C- and A delta-fiber evoked responses but not the A beta-fiber evoked response. Drug effects were reversed by the alpha (2)-AR antagonists, atipamezole and idazoxan (100 microg). In rats with unilateral spinal nerve (L5-L6) ligation performed 2 weeks before study, S18616 (0.1 to 3.0 microg) dose-dependently suppressed the C- and A delta-fiber evoked responses and blocked "wind-up" in these neurons. The potency was comparable between nerve-injured and sham-operated rats, and S18616 was equally effective against responses to thermal and high-intensity mechanical stimuli. Interestingly, the effectiveness of S18616 on the low-intensity mechanical evoked response was significantly enhanced after nerve injury. Finally, S18616 (0.3 and 3.0 microg) reduced the neuronal responses produced by intraplantar injection of formalin. In conclusion, S18616 dose-dependently and potently inhibits the responses of dorsal horn neurons to peripheral stimulation in normal, inflamed, and neuropathic rats. These data support the use of spinal S18616 and other alpha (2)-AR agonists in the management of clinical pain.

Combined spinal-epidural analgesia for labor: breakthrough or unjustified invasion?

The combined spina-epidural (CSE) technique has become increasingly popular for labor analgesia. The advantages of the CSE include more rapid onset of analgesia, reduced total drug dosage, minimal or no motor blockade, and increased patient satisfaction. CSE has also been associated with more rapid cervical dilation when compared to epidural analgesia in nulliparous women in early labor. Despite these potential advantages, the indications for CSE versus epidural analgesia remain unclear and controversial. This review should allow better understanding of the benefits and risks of this technique, and bearing in mind that no ultimate neuraxial analgesic exists, it would seem that CSE should be considered a major breakthrough in the management of labor analgesia.

The addition of morphine prolongs fentanyl-bupivacaine spinal analgesia for the relief of labor pain

The combination intrathecal fentanyl (25 microg) and bupivacaine (2.5 mg) provides effective labor analgesia for approximately 90 minutes. The purpose of this prospective, randomized, double-blinded investigation was to determine if the addition of morphine (150 microg) to the intrathecal combination of fentanyl (25 microg) and bupivacaine (2.5 mg) would prolong labor analgesia. By using the combined spinal epidural technique, 95 healthy primiparous laboring women in early labor received 2 mL of one of the two intrathecal study solutions, either FB (n = 48): fentanyl (25 microg) and bupivacaine (2.5 mg); or FBM (n = 47): fentanyl (25 microg) and bupivacaine (2.5 mg) plus morphine (150 microg). The mean duration of labor analgesia was significantly longer in the FBM group than in the FB group (252 +/- 63 min vs 148 +/- 44 min, P < 0.01). There were no significant differences between the two groups regarding the sensory levels, the incidence of nausea, vomiting, pruritus, hypotension, or operative delivery. In conclusion, the addition of 150 microg of morphine to the intrathecal combination of fentanyl plus bupivacaine prolonged the duration of labor analgesia duration without increasing adverse effects.

IMPLICATIONS

The addition of morphine (150 microg) to intrathecal fentanyl (25 microg) and bupivacaine (2.5 mg) prolongs the duration of labor analgesia duration without increasing adverse effects.

Optimal dose of intrathecal clonidine added to sufentanil plus bupivacaine for labour analgesia

PURPOSE

The combination of intrathecal (IT) 5 microg sufentanil plus 1.25 mg bupivacaine is useful for inducing labour analgesia, albeit of short duration and slow onset. As a supplementation to this regimen, the effect of IT clonidine on the duration of analgesic action was investigated.

METHODS

Forty-eight healthy parturients were randomly assigned into three groups to receive 0 microg (group C0), 15 microg (C15) or 30 microg (C30) of clonidine IT in addition to 5 microg sufentanil plus 1.25 mg bupivacaine IT for labour analgesia. The quality of pain relief was assessed on 0-100 visual analogue scale by the author. The occurrence of side effects was also evaluated before the request for additional analgesia.

RESULTS

Clonidine (C15 and C30), produced a longer duration of analgesia than C0 (mean 144 +/- sd 27.9, 165 +/- 31.8 vs 111 +/- 21.9 min, P < 0.01). Also, C15 and C30 produced a more rapid onset and a higher quality of analgesia than C0, (P < 0.01). The most cephalad level of sensory block was higher in C30 than C15 (median T3 vs T4, P < 0.05) but lowest in C0 (median T7 vs T3,T4, P < 0.01). Side effects, sedation and hypotension, occurred more frequently in C30 than in either C0 or C 15, (9 vs 2,5 and 9 vs 1,3, respectively, P < 0.05).

CONCLUSION

The optimal dose of intrathecal clonidine to enhance labour analgesia with the current sufentanil-bupivacaine regimen is 15 microg. In view of the side effect profile, doses greater than 30 microg clonidine are unlikely to be useful.

Low-dose intrathecal clonidine combined with sufentanil as analgesic drugs in abdominal gynecological surgery

STUDY OBJECTIVES

To determine whether a low dose of spinal clonidine either alone or combined with sufentanil would provide effective analgesia following abdominal surgery, as a supplement to bupivacaine spinal anesthesia.

DESIGN

Randomized double-blind study.

SETTING

Gynecological surgery, teaching hospital.

PATIENTS

73 ASA physical status I and II patients undergoing gynecological abdominal surgery with spinal anesthesia.

INTERVENTIONS

Patients were randomly assigned to one of four groups and prospectively studied to examine anesthesia, analgesia, and adverse effects. The control group received saline as the test drug; the sufentanil group received 10 microg of sufentanil; the clonidine group received 30 microg of clonidine; and the sufentanil/clonidine group received 5 microg of sufentanil plus 15 microg of clonidine. All groups received intrathecal 15 mg of bupivacaine (3 mL) plus the intrathecal test drug (2 mL). The concept of visual analog scale (VAS) was introduced. All patients were premedicated with intravenous midazolam. Rescue analgesics were available.

MEASUREMENTS AND MAIN RESULTS

The groups were demographically the same. Sensory block to pinprick at 10 min was higher for clonidine and sufentanil/clonidine groups compared to the control group (p < 0.02). Anesthetic time (Bromage score 2) was also longer for clonidine and sufentanil/clonidine groups compared to the control and sufentanil groups (p < 0.05). Time to first rescue analgesics was shorter in the control group compared to the other groups (p < 0.02). The number of IM diclofenac dose injections in 24 hours was higher in the control group compared to all other groups (p < 0.05). The incidence of adverse effects and ephedrine consumption were similar among groups.

CONCLUSIONS

Intrathecal 15- and 30-microg clonidine doses expanded the anesthesia sensory block and duration of motor block, and provided analgesia.

Effect of epidural clonidine added to epidural sufentanil for labor pain management

Labor analgesia with intrathecal sufentanil has been shown to be prolonged by the addition of intrathecal clonidine. The current study was designed to determine if epidural clonidine would prolong labor analgesia provided by epidural sufentanil. Forty laboring primiparous women at less than 5 cm cervical dilation requesting epidural analgesia were enrolled. Following a 3 mL test dose of lidocaine with epinephrine, patients were randomized to receive 10 mL of either sufentanil 20 microg (S) or sufentanil 20 microg with clonidine 75 microg (SC). After administration of the analgesic, pain scores and side-effects were recorded for each patient at 5, 10, 15, 20 and 30 min, and every 30 min thereafter, by an observer blinded to the technique used. There were no demographic differences between the two groups. Pain relief was rapid for all patients. The mean duration of analgesia was similar between the S group (153 +/- 78 min) and the SC group (178 +/- 55 min). Side-effects were similar between the two groups. There was no difference between the two groups in time from sufentanil administration to delivery, incidence of operative or assisted delivery, or cervical dilation at the time of redose. For early laboring patients, epidural sufentanil 20 microg after a lidocaine test dose provides analgesia comparable to that of sufentanil 20 microg with clonidine 75 microg; there was no significant difference in analgesic duration between the two groups.