High sensory block after intrathecal sufentanil for labor analgesia

Transient lower cranial nerve palsies following spinal anesthesia with bupivacaine-fentanyl combination for transurethral resection of the prostate

Spinal anesthesia is a widely used regional anesthesia for many infra-umbilical surgical procedures with proven efficacy and safety. However, although rare, some neurologic complications can occur with potentially life threatening consequences. Among them, lower cranial nerve palsies have been rarely reported in the literature. We report such a case in a 75-year-old man with transient dysphagia, dysphonia and spinal accessory nerve palsy occurring four days after spinal anesthesia for transurethral resection of the prostate. His symptoms completely resolved spontaneously within 2 weeks. The possibility of lower cranial nerve palsies should be added to the potential complications during or following spinal anesthesia with bupivacaine-fentanyl combination. Although transitional, this complication may occur few days after the procedure and need to be promptly recognized, carefully evaluated and treated by conservative measures.

A case of trigeminal hypersensitivity after administration of intrathecal sufentanil and bupivacaine for labor analgesia

Rostral spread of intrathecal drugs and sensitization of supraspinal sites may provoke several adverse effects. This case describes a patient with right hemifacial paresthesia, trismus and dysphasia on the trigeminal nerve distribution after intrathecal sufentanil administration. Primigravida, 34 years, 39 weeks of pregnancy, with hypothyroidism and pregnancy induced hypertension. Allergic to latex. In the use of puran T4, 50 μg /day. When the patient presented cervical dilatation of 4 cm, she requested analgesia. She was placed in the sitting position and a spinal puncture was performed with a 27G needle pencil point in L4/L5 (1.5 mg of bupivacaine plus 7.5 μg of sufentanil). Next, was performed an epidural puncture in the same space. It was injected bupivacaine 0.065%, 10 ml, to facilitate the passage of the catheter. After 5 min lying down in the lateral upright position, she complained of perioral and right hemifacial paresthesia, mainly maxillary and periorbital, as well as trismus and difficulty to speak. The symptoms lasted for 30 min and resolved spontaneously. After 1 h, patient requested supplementary analgesia (12 ml of bupivacaine 0.125%) and a healthy baby girl was born. Temporary mental alterations have been described with the use of fentanyl and sufentanil in combined epidural-spinal analgesia, such as aphasia, difficulty of swallowing, mental confusion and even unconsciousness. In this patient, facial areas with paresthesia indicated by patient appear in clear association with the ophthalmic and maxillary branches of the trigeminal nerve and the occurrence of trismus and dysphagia are in association with the mandibular motor branch. The exact mechanism of rostral spread is not known, but it is speculated that after spinal drug administration, a subsequent epidural dose may reduce the intratecal space and propel the drug into the supraspinal sites.

Transient unilateral brachial plexopathy and partial Horner's syndrome following spinal anesthesia for cesarean section

A healthy 21-year-old primigravida presented for elective cesarean section. At 45 min after intrathecal (IT) injection of bupivacaine, morphine and fentanyl she developed dysphagia, right sided facial droop, ptosis and ulnar nerve weakness. This constellation of signs and symptoms resolved 2 h later. Based on the time course and laterality of her symptoms, as well as the pharmacologic properties of spinal opioids, we believe her symptoms can be attributed to the IT administration of fentanyl.

Intraoperative neurological event during cesarean section under spinal anesthesia with fentanyl and bupivacaine: Case report and review of literature

Neurological events similar to transient ischemic attack in a peripartum woman are uncommon. Cerebral complications of preeclampsia, thrombo-embolic phenomena, or high spinal can mimic such situations. Spinal anesthesia with local anesthetic and opioid is an established anesthetic technique for cesarean section. Although intrathecal opioids are safe for both the mother and fetus; some unusual complications such as dysphagia alone or associated with facial numbness, aphasia, have been reported. We report a case of transient aphonia and tingling sensation over the face without any dysphagia after intrathecal administration of bupivacaine and fentanyl for cesarean section.

A comparative evaluation of intrathecal bupivacaine alone, sufentanil or butorphanol in combination with bupivacaine for endoscopic urological surgery

BACKGROUND

The objective of the present study was to compare the onset, degree and recovery time of sensory and motor block and hemodynamic effects of intrathecal bupivacaine alone and bupivacaine with sufentanil or butorphanol in endoscopic urological surgeries.

METHODS

In a randomized, double-blind study, 90 patients of either sex and age, belonging to ASA Grades I and II, scheduled for elective endoscopic urological surgeries under spinal anesthesia, were allocated into three groups of 30 each. Patients received either 2.5 ml of 0.5% hyperbaric buypivacaine 12.5 mg (Group A), 1.5 ml of 0.5% hyperbaric bupivacaine 7.5 mg with 10 μg sufentanil (Group B) or 1.5 ml of 0.5% hyperbaric bupivacaine 7.5 mg with 25 μg butorphanol (Group C). Vital parameters, level, duration and regression of sensory block and motor block and side-effects were recorded and compared.

STATISTICAL ANALYSIS

Analysis of variance (ANOVA), post hoc test and Chi-square test were used.

RESULTS

Intrathecal addition of sufentanil/butorphanol prolonged the duration of sensory block (DOSB) compared with bupivacaine alone (DOSB being 156.83±23.83 min, 170.87 ± 22.21 min and 171.17 ± 23.99 min in groups A, B and C, respectively) without altering the duration of motor blockade. Bromage score 3 was achieved in 100%, 90% and 54.4% patients in groups A, B and C, respectively. The time to first request for analgesia was 112 ± 46.3 min, 323 ± 65.0 min and 299 ± 73.9 min in groups A, B and C, respectively. Complications were reduced by the addition of butorphanol, which also has a lower tendency than sufentanil to produce pruritus (60%).

CONCLUSIONS

The analgesia was significantly prolonged in groups B and C; group C had a less-intense motor block. Complications were reduced by the addition of butorphanol, which also has a lower tendency than sufentanil to produce pruritus. Thus, this combination of butorphanol with low-dose bupivacaine is especially beneficial in the geriatric group of patients who have multiple co-morbid conditions.

Modern neuraxial labor analgesia: options for initiation, maintenance and drug selection

In the present review we outline the state-of-the-art of neuraxial analgesia. As neuraxial analgesia remains the gold standar of analgesia during labor, we review the most recent literature on this topic. The neuraxial analgesia techniques, types of administration, drugs, adjuvants, and adverse effects are investigated from the references. Most authors would agree that central neuraxial analgesia is the best form to manage labor pain. When neuraxial analgesia is administered to the parturient in labor, different management choices must be made by the anesthetist: how will we initiate analgesia, how will analgesia be maintained, which local anesthetic will we use for neuraxial analgesia and which adjuvant drugs will we combine? The present manuscript tries to review the literature to answer these questions.

Respiratory depression after neuraxial opioids in the obstetric setting

Neuraxial opioids have contributed significantly to improved labor and postcesarean delivery analgesia. In the obstetric population, epidural and intrathecal opioids are associated with a very low risk of clinically significant respiratory depression. Although rare, respiratory depression is a serious risk; patients may die or suffer permanent brain damage as a consequence. This review discusses the mechanism and incidence, as well as the prevention, detection, and management of respiratory depression with morphine, extended-release epidural morphine, and lipophilic opioids in the labor and cesarean delivery setting.

Aphonia and quadriplegia---a rare complication following epidural labor analgesia

We report an obstetric patient who developed unusual neurological complications after an epidural injection of a local anesthetic and a narcotic in a seemingly faultless manner. Ten minutes after receiving a loading dose, the patient developed aphonia, quadriplegia, and facial palsy while retaining normal consciousness and stable hemodynamics. The episode spontaneously resolved 40 minutes later. We wish to draw attention to anesthesiologists of the possibility that even in the presence of a negative aspiration test or without noticeable dural puncture, the injected drugs may enter the intrathecal or subdural space instead of pooling entirely in the epidural compartment. Once an unexpected high block and unusual symptoms or signs are noted, a prompt differential diagnosis must be made and treatment initiated as soon as possible.

[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 plainvs hyperbaric bupivacaine for labour analgesia: efficacy and side effects

PURPOSE

Baricity is an important determinant of block characteristics of the spinal component of a combined spinal epidural (CSE) for labour analgesia. This study compares the analgesic efficacy and side effects of intrathecally administered plain and hyperbaric bupivacaine (both with fentanyl) during active labour.

METHODS

Sixty-two women in active labour (cervical dilatation >or=5 cm and pain score > 5) were randomized in a prospective, single-blinded fashion to receive 2.5 mg of either hyperbaric or plain bupivacaine both combined with 15 microg of fentanyl as the spinal component of a CSE. The primary outcome was failure of satisfactory analgesia within ten minutes of the intrathecal injection as defined by a verbal pain score > 3. Secondary outcomes included need for rescue analgesia, hypotension, respiratory depression, nausea and vomiting, pruritus and sustained fetal bradycardia.

RESULTS

Sixty patients were analyzed. The failure rates were 20% in the hyperbaric group vs 0% in the plain group (P=0.024). The plain solution provided faster onset, higher sensory levels and less motor block at all times during the first 30 min. The incidence of both pruritus and sustained fetal bradycardia was 33% in the plain group and 10% in the hyperbaric group (P=0.03).

CONCLUSION

A plain rather than hyperbaric solution of bupivacaine 2.5 mg with fentanyl 15 microg provides a faster onset of analgesia, higher sensory levels and less motor block, while demonstrating an increased incidence of pruritus and sustained fetal bradycardia.

Two additional cases of excessive extension of sensory blockade after intrathecal sufentanil for labor analgesia

Combined spinal-epidural anesthesia (CSE) is an effective technique with rapid onset of labor analgesia. We describe two cases of excessive cephalad spread of sensory blockade without motor blockade in two parturients in spontaneous labor with CSE. The patients received sufentanil 5 microg intrathecally with 1.25 mg bupivacaine. Spinal injection produced dyspnea and extension of sensory blockade to cervical or facial level without fetal consequences. We conclude that the risk of these side-effects previously described with the 10 microg dose persists for lower sufentanil spinal doses.

Intrathecal Clonidine for Postoperative Analgesia in Elderly Patients: The Influence of Baricity on Hemodynamic and Analgesic Effects

Intrathecal (IT) clonidine is an effective analgesic, but it also produces hemodynamic depression and sedation which are likely to be related to IT clonidine's cephalad spread within the cerebrospinal fluid. We hypothesized that IT clonidine's side effects could be reduced without compromising the duration and quality of analgesia by injecting clonidine IT in a hyperbaric solution and elevating the patient's trunk. We prospectively randomized 30 elderly patients to receive IT 150 microg of either isobaric (ISO) or hyperbaric (HYPER) clonidine for postoperative analgesia after surgical repair of traumatic hip fracture. Hemodynamics, IV fluid administration, visual analog pain scores, sedation scores, and clonidine cerebrospinal fluid levels were recorded at fixed intervals. Patients in the ISO group required significantly more crystalloid fluid administration (median, 2500 mL; range, 1500-3000 mL) than those in the HYPER group (median, 1500; range, 500-3000 mL) to maintain adequate arterial blood pressure (P < 0.01). Also, the decrease in heart rate was significantly more pronounced in the ISO than in the HYPER group (P < 0.01). The duration of analgesia was significantly larger in the ISO (median, 400 min; range, 115-400 min) than in the HYPER (median, 265 min; range, 205-400 min) group (P < 0.05). Sedation scores did not differ between groups. We conclude that increasing the baricity of IT clonidine solution in the conditions of our experiment reduces hemodynamic side effects but also analgesia from IT administered clonidine.

Body habitus does not influence spread of sensory blockade after the intrathecal injection of a hypobaric solution in term parturients

PURPOSE

To determine if the extent of sensory blockade after the intrathecal injection of hypobaric fentanyl (25 micro g) and bupicavaine (2.5 mg) in the sitting position in term parturients is influenced by body habitus.

METHODS

A prospective observational study in 245 term parturients who received intrathecal fentanyl and bupivacaine plus an epidural test dose to initiate labour analgesia at an academic university hospital. The highest sensory blockade to ice and pinprick was determined at 15 and 30 min after the intrathecal injection. Correlations between sensory blockade and parturient height, weight and body mass index (BMI) were determined.

RESULTS

There was no association between highest sensory blockade and parturients' height. Increasing weight and BMI were associated with increased cephalad sensory blockade at 15 min, but not at 30 min. The estimated difference in sensory level between women at the extremes of BMI, based on our linear regression model, was less than one dermatome.

CONCLUSION

Height did not influence the extent of sensory analgesia after initiation of intrathecal labour analgesia using a hypobaric solution injected with the parturient in the sitting position. Weight and BMI were associated with a non-clinically significant increase in the cephalic spread of analgesia, suggesting that dose adjustments based on body habitus in this population are not necessary.

Newer techniques of labor analgesia

In maternity units in which central neuraxial techniques are frequently used, newer methods of epidural drug delivery (continuous infusion, patient-controlled) are well established and combined spinal-epidural analgesia is commonly used. Continuous spinal analgesia has reemerged as a useful approach after accidental dural puncture. Lumbar sympathetic block has been revisited and the safety of paracervical nerve block improved. The analgesic properties of systemic opioid in labor are poor, but PCIA at least has psychological benefits and allows rapid drug titration. PCIA is again under investigation because of the potent antinociceptive effects of the short-acting mu-opioid agonist, remifentanil. The premixing of nitrous oxide and a subanesthetic concentration of volatile anesthetic for patient-controlled administration has been tested under control of midwifery staff and without direct medical supervision.

The effect of large-dose intrathecal opioids on the autonomic nervous system

Decreases in blood pressure after the spinal injection of opioids suggest that intrathecal (IT) opioids may have a sympatholytic effect similar to that of local anesthetic drugs. We compared two groups of patients aged 10-16 yr (n = 10 in each group). Group One (IT group) received IT opioids. Group Two (Epidural group) received 0.5% bupivacaine epidurally. The sympathetic effects of IT opioids and epidural bupivacaine were monitored by the changes in toe relative to calf temperature and by the changes in pulse wave gradients with digital plethysmography. Changes in temperature gradients comparing calf to toe and increases in pulse amplitude indicate vasodilatation caused by sympathetic blockade in this model. Calf to toe temperature gradients (Deltacalf-Deltatoe) were evaluated by subtracting the two measurements. Pulse wave plethysmography was recorded before and after spinal and epidural injection at intervals of 10 min for 40 min. All patients demonstrated changes in their calf to toe gradients after IT and epidural injections (-3.2 +/- 1.6). Systolic blood pressure decreased from a mean of 70 +/- 15 mm Hg to 55 +/- 10 mm Hg. Pulse wave plethysmography amplitude increased after the intrathecal opioid and epidural bupivacaine injection similarly. We conclude that the increases in pulse wave amplitude and decreases in calf-toe gradients indicate a sympatholytic effect after IT opioids similar to that of local anesthetics.

IMPLICATIONS

The sympatholytic effects of neuraxial opioids were compared with those of local anesthetics. Two groups of patients were assigned to receive a neuraxial opioid or bupivacaine. Our results demonstrate that opioids cause hypotension and peripheral vasodilatation similar to bupivacaine. This finding suggests that neuraxial opioids have a sympatholytic effect comparable to that of local anesthetic drugs.

Regional anesthesia for obstetrics

The practice of administration of labor analgesia has undergone dramatic changes this decade. This is largely attributable to unparalleled interest in the field by many dedicated and capable investigators around the world. Through their efforts, this decade has witnessed the introduction of new techniques (pencil point needles, CSE, PCEA, ultradilute epidural regimens) that have permitted us to come closer than ever to realizing the goal of complete relief from the pain and suffering of labor while safeguarding the well-being of mother and child and minimizing effects on the labor process. Neuraxial anesthetic techniques and modern multimodal analgesic approaches to postoperative pain relief now minimize the effects of cesarean delivery on maternal satisfaction and participation in the birth process.

Analgesia, pruritus, and ventilation exhibit a dose-response relationship in parturients receiving intrathecal fentanyl during labor

Several studies have characterized the 50% and 95% effective doses (ED50 and ED95, respectively) of intrathecal sufentanil for labor analgesia. Few have investigated these same criteria for the less expensive alternative, fentanyl. In addition, the ventilatory effects of intrathecal fentanyl at clinically relevant doses are unclear. We performed this study to establish the dose-response relationship of intrathecal fentanyl for both analgesia and ventilatory depression. Ninety parturients in active early labor (< or = 5 cm dilation) received intrathecal fentanyl 5, 7.5, 10, 15, 20, or 25 micrograms in a double-blinded, randomized fashion (n = 15 patients in each group). Parturients were monitored for degree of pain (measured using a 100-mm visual analog pain scale), blood pressure, arterial oxygen saturation (SaO2), respiratory rate, ETCO2, and fetal heart rate 0, 1, 5, 10, 15, 20, 25, and 30 min after the administration of intrathecal fentanyl. An absolute visual analog pain scale score < or = 25 mm was defined a priori as analgesic success. The percentage of parturients who achieved analgesic success was used to construct quantal dose-response curves, from which the ED50 and ED95 values were derived for the total population (mixed parity) and the nulliparous and multiparous subpopulations separately. Overall ED50 and ED95 values (95% CI) were 5.5 (3.4-7.2) and 17.4 (13.8-27.1) micrograms, respectively. Nulliparous values were lower (5.3 and 15.9 micrograms, respectively) than multiparous values (6.9 and 26.0 micrograms, respectively) but were within the 95% CIs of the total population. Pruritus incidence in parturients with analgesic success displayed a dose-response relationship identical to that seen for analgesia. ETCO2 displayed a dose-related increase, particularly at doses > or = 15 micrograms, without concomitant changes in respiratory rate or SaO2, which suggests a decrease in tidal volume. Even in the absence of overt signs or symptoms of somnolence, intrathecal fentanyl at doses within the effective analgesic range induced a change in ventilation that may last longer than the 30-min period we studied.

IMPLICATIONS

Intrathecal fentanyl induces rapid and satisfying dose-dependent analgesia in early labor; however, it also produces dose-related decreases in ventilation in the absence of overt somnolence.

New epidural techniques for labour analgesia: patient-controlled epidural analgesia and combined spinal-epidural analgesia

Epidural analgesia in labour aims to provide high-quality pain relief of rapid onset and prolonged duration, while minimizing both maternal side-effects, particularly impairment of mobility, and impact on the fetus or on the outcome of labour. In conjunction with pharmacological research on spinal analgesics (local anaesthetics, opioids and other drug classes), refinement of new or established drug delivery techniques has allowed progress toward more reliable and improved pain relief at all stages of labour and childbirth, reduced individual drug doses with reduction of unwanted effects and greater safety and enhancement of maternal satisfaction. Patient-controlled epidural analgesia in labour has been in use for almost a decade, although is only now at a stage where its role is well defined and utility can be increased. Combined spinal-epidural analgesia is a more recent refinement which appears to be extremely promising but awaits further investigation.

An intravenous fluid bolus is not necessary before administration of intrathecal fentanyl for labor analgesia

STUDY OBJECTIVE

To determine if an intravenous (i.v.) fluid bolus is necessary to prevent any possible hemodynamic sequelae after administration of intrathecal fentanyl in laboring parturients.

DESIGN

Prospective, randomized study.

SETTING

Labor suite of a women's tertiary care hospital.

PATIENTS

30 ASA physical status I and II parturients in active labor requesting labor analgesia.

INTERVENTIONS

Patients were randomly divided into two groups of 15. One group received no i.v. fluid prior to the administration of 25 micrograms of intrathecal fentanyl, and the other group received 500 ml of lactated Ringer's solution before the block.

MEASUREMENTS AND MAIN RESULTS

Blood pressures [systolic (SBP), diastolic (DBP), mean (MAP)], heart rate (HR), cardiac index (CI; using impedance cardiography), and visual analog scores were measured before the block, after fluids, and then every 5 minutes for 45 minutes after the block. Prenatal baseline blood pressures before the onset of labor were obtained from the obstetrician's office records. Results were analyzed using analysis of variance. All patients reported good pain relief. No patient from either group required treatment for hypotension. In the no fluid group, SBP and MAP decreased 10% and 14%, respectively (p = 0.05), following intrathecal fentanyl administration compared with preblock values obtained during labor but not when compared with prelabor prenatal values. In the fluid group, no significant changes occurred in SBP after intrathecal fentanyl but MAP decreased approximately 12% only in comparison to preblock values. No significant changes were noted in CI in either group. Fluid infusion itself caused an increase in HR and CI of approximately 12% and 9.4%, respectively.

CONCLUSION

Intrathecal fentanyl produces only minimal hemodynamic changes with or without prior fluid administration.

Respiratory arrest following intrathecal injection of sufentanil and bupivacaine in a parturient

PURPOSE

To present a case of respiratory arrest following the use of intrathecal sufentanil and bupivacaine for combined spinal-epidural anaesthesia in a healthy labouring parturient.

CLINICAL FEATURES

A 20-yr-old term parturient received 10 micrograms sufentanil and 2.5 mg bupivacaine intrathecally as part of a combined spinal-epidural technique for labour analgesia. She had received no previous analgesics. Twenty-three minutes after the intrathecal injection she became unresponsive and suffered a respiratory arrest. Resuscitation included manual bag/mask ventilation with oxygen and intravenous naloxone.

CONCLUSION

Respiratory arrest is a rare but potentially life-threatening complication associated with the use of intrathecal opioids for labour analgesia. Vigilance in post-procedure patient monitoring is imperative.

Neuraxial opioids in labour

Neuraxial opioids were first used for labour analgesia in 1980 following the description of spinal cord opioid receptors in 1979. Via these receptors in the dorsal horn, opioids modulate both the visceral and the somatic pain of labour. The onset and duration of action of the individual opioid are determined primarily by its relative lipid solubility. Neuraxial opioids have a local anaesthetic sparing effect, allowing the use of lower concentrations of both agents while maintaining analgesia. As a sole agent, intrathecal opioids can be used to provide analgesia during the first stage of labour, especially in the high-risk parturient. They also have a role in the management of perineal pain and the provision of rapid-onset analgesia. Unfortunately maternal and neonatal side-effects can occur, the most important being respiratory depression.

Does dextrose affect analgesia or the side effects of intrathecal sufentanil?

Intrathecal (i.t.) sufentanil provides rapid effective pain relief for early labor, but it also produces undesirable side effects, which may be primarily related to cephalad spread. Although the combination of dextrose and positioning the patient head-up limits the spread of other spinally administered drugs, these factors have not been examined in laboring women receiving i.t. sufentanil. We hypothesized that the addition of dextrose to i.t. sufentanil injected with women in the sitting position would limit cephalad spread and side effects. Sixty-six healthy nulliparous parturients in early labor were randomized to receive 2-mL i.t. injections of sufentanil 10 micrograms plus saline with patients in either the lateral decubitus or sitting position, sufentanil 10 micrograms plus dextrose 7.5% with patients in either the lateral decubitus or sitting positions, or plain dextrose 7.5%. Pain scores using a 10-cm visual analog pain scale, sensory block height, and side effects were recorded. Dextrose 7.5% did not affect cephalad spread, as measured by block height to pin testing, but it did significantly reduce the duration of analgesia and the incidence of pruritus from i.t. sufentanil administered to patients in the sitting position compared with patients in the lateral position. In contrast, patient position had no effect on analgesia or side effects in patients receiving i.t. sufentanil in saline. I.t. dextrose alone had no effect.

IMPLICATIONS

The authors conclude that the addition of dextrose to intrathecal sufentanil injected into patients in the sitting position reduces the duration of analgesia without significantly reducing side effects with the exception of pruritus, and therefore does not improve the clinical utility of intrathecal sufentanil.

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.

Intrathecal sufentanil for labor analgesia: do sensory changes predict better analgesia and greater hypotension?

Sensory changes and hypotension occur after intrathecal sufentanil (ITS) is given during labor. The goal of this study was to determine whether sensory changes are predictive of hemodynamic changes or duration of pain relief. We also examined whether sensory and hemodynamic changes relate to the concentration of ITS administered. Forty-five ASA physical status I and II women in active labor were randomly assigned to receive 10 micrograms ITS diluted in either 1, 2, or 3 mL of normal saline (15 in each group). An observer blinded to treatment recorded verbal pain scores, blood pressure, and sensory changes to light touch, pinprick, and cold at frequent intervals. Excellent analgesia was obtained in 42 of 45 patients. There were no differences among the groups with respect to the number of patients with sensory changes, the duration of analgesia or sensory changes, the quality of analgesia, or the severity of hypotension. The groups were therefore combined for further analyses. Among this combined group, the duration of analgesia was 99 +/- 7 min (mean +/- SE). Cold, pinprick, and light touch sensation were decreased in 66%, 50%, and 33% of patients, respectively. Motor block was absent in all patients. The duration and quality of analgesia were similar in subjects with and without sensory changes. Systolic blood pressure decreased 23 +/- 2 mm Hg (P < 0.05) during the first 30 min after ITS, and six patients were given ephedrine. The magnitude of blood pressure change was not affected by the diluent volume or the presence of sensory changes. Because sensory changes were not predictive of the duration or quality of analgesia or the degree of hemodynamic change, we conclude that analgesia with ITS is predominantly mediated via spinal cord opioid receptors rather than by a local anesthetic-type conduction blockade.

Densities of dextrose-free intrathecal local anesthetics, opioids, and combinations measured at 37 degrees C

Dextrose-free anesthetic medications are commonly used to provide subarachnoid anesthesia and analgesia. Hypobaricity has been proposed as a mechanism to explain postural effects on the extent of sensory block produced by these drugs. Densities of dextrose-free solutions of local anesthetics and opioids, and commonly used anesthetic/opioid mixtures were determined at 37.00 degrees C for comparison with the density of human cerebrospinal fluid (CSF). Measurements accurate to 0.00001 g/mL were performed using a mechanical oscillation resonance frequency density meter. All undiluted solutions tested are hypobaric relative to human lumbar CSF with the exception of lidocaine 1.5% and 2.0% with epinephrine 1:200,000. All mixtures of local anesthetics and opioids tested are hypobaric. We observed good agreement between measured densities and calculated weighted average densities of anesthetic mixtures. While the influence of baricity on the clinical effects of dextrose-free intrathecal anesthetics remains controversial, attempts to attribute postural effects to the baricity of these drugs requires establishment of accurate density values. These density data may facilitate elucidation of the mechanisms underlying the behavior of dextrose-free intrathecal anesthetics.

Maternal posture influences the extent of sensory block produced by intrathecal dextrose-free bupivacaine with fentanyl for labor analgesia

The cephalad extent of sensory block produced by intrathecal (IT) dextrose-free local anesthetics and opioids has been reported to be quite variable. Most reports describing the effects of IT analgesics do not control for patients posture. Because these medications are hypobaric relative to cerebrospinal fluid (CSF), parturients in a sitting position may develop greater cephalad extents of sensory block than those in a lateral position during IT injection. Parturients in labor were randomized to sitting or lateral position during IT administration of dextrose-free bupivacaine 0.25% with fentanyl 0.005%. Extent of sensory block was evaluated at intervals thereafter. Free flow of CSF was obtained in 20 parturients. Those in a sitting position during IT injection had significantly higher maximal cephalad extent of block than those in a lateral position (mean +/- SD, T-3.1 +/- 2.9 vs T-6.3 +/- 3.4, P = 0.036). Mean cephalad extent of block was greater in the sitting group at 20 and 30 min. When sensory block asymmetry was observed, the extent of block was greater on the nondependent side. Posture during IT injection of this dextrose-free analgesic combination affects extent of sensory block in laboring parturients.

A comparison of the local anesthetic effects of meperidine, fentanyl, and sufentanil on dorsal root axons

The local anesthetic effects of opioids have been demonstrated in both clinical and laboratory studies. Clinically, both meperidine and sufentanil can produce segmental sensory anesthesia. However, previous studies of the effects of opioids on nerve conduction have all made use of peripheral nerve preparations and yielded conflicting results. In the present study we describe the local anesthetic effects of phenylpiperidine opioids on individual dorsal root axons, the probable target for intrathecal local anesthetics. Dorsal roots were removed from anesthetized adult male rats and maintained in vitro. Standard single fiber recording techniques were used to isolate activity in the individual axons. Drug exposure was accomplished by perfusing the isolated dorsal root with an artificial cerebrospinal fluid containing the study drug at a clinically relevant concentration. Steady-state drug effects were measured after 15-30 min of exposure and compared to control measurements in the same preparation. Meperidine (705 microM) blocked conduction in 61.5% of 39 myelinated and unmyelinated axons, and significantly reduced conduction velocity in the remaining unblocked axons. These effects were not naloxone reversible. Fentanyl (0.6 microM and 3 microM) and sufentanil (1.04 microM) failed to affect the nerve conduction in any dorsal root axon. The discrepancy between laboratory and clinical observations is discussed. We suggest that the site of conduction block may occur at the proximal end of the dorsal root as it passes through the dorsal root entry zone, an anatomically unique segment of the primary sensory pathway with decreased conduction safety for action potential propagation.