Does Epinephrine Improve the Diagnostic Accuracy of Aspiration During Labor Epidural Analgesia?

Local anesthetic systemic toxicity

Local anesthetic systemic toxicity (LAST) is a rare yet devastating complication from the administration of local anesthesia. The ability to recognize and treat LAST is critical for clinicians who administer these drugs. The authors reviewed the literature on the mechanism, treatment, and prevention of LAST, with the goal of proposing a practical method for its management.

Local anesthetic systemic toxicity: prevention and treatment

Anesthesia is a sine qua non for most surgeries. Like any medical advance, progress in regional anesthesia has not come without its share of complications, including a spectrum extending from localized nerve injury to systemic cardiovascular toxicity and death. This article discusses the mechanisms and clinical presentation, prevention, treatment, and future trends of local anesthetic systemic toxicity. The adverse effects of lipid emulsion therapy are also included.

Side effects of spiramycin masquerading as local anesthetic toxicity during labor epidural analgesia

Significant fetal bradycardia occurred when a parturient receiving labor epidural analgesia experienced generalized numbness and tingling, a metallic taste and hot flushes. An emergent cesarean delivery under general anesthesia was performed with favorable outcomes for the mother and baby. The most likely source of the maternal symptoms was spiramycin, which was being administered for treatment of toxoplasmosis.

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.

[Comparison of intrathecal fentanyl and bupivacaine in combined spinal-epidural obstetric analgesia]

OBJECTIVES

To compare intrathecal injection of the opioid fentanyl to injection of bupivacaine, in terms of their effect of labour in the context within the combined spinal-epidural analgesia.

METHODS

Prospective single-blind trial in primiparas randomized to 2 groups for sedation with 25 microg of fentanyl or 2.5 mg of bupivacaine, followed in both cases by epidural infusion of ropivacaine. We measured time from puncture to delivery of the neonate, rescue analgesia, pain assessed on a visual analog scale (VAS), motor block, side effects, sensory level, Apgar score, and maternal satisfaction.

RESULTS

Sixty-four women were studied. The mean time elapsed between puncture and birth was 168.59 minutes (95% confidence interval [CI], 134.16 to 203.03 minutes) in the bupivacaine group and 189.13 minutes (95% CI, 151.93 to 226.32 minutes) in the fentanyl group. The mean difference was -20.53 minutes (95% CI, -70.21 to 29.15 minutes). Survival analysis applied to duration of labor, using type of delivery as the final outcome, also failed to show a significant between-group difference (chi2=0.59, P=.447). No significant differences in use of rescue analgesia, VAS scores, or motor block were observed. The incidence of pruritus in the fentanyl group was 34.37%, but there were no differences in maternal satisfaction.

CONCLUSIONS

Our findings do not support the use of intradural fentanyl with the aim of shortening labor. Fentanyl leads to more pruritus, although this side effect does not affect maternal satisfaction.

Epidural clonidine added to a bupivacaine infusion increases analgesic duration in labor without adverse maternal or fetal effects

PURPOSE

Many obstetric patients receiving epidural analgesia are encouraged to ambulate. This current study was designed to determine the potential for maximizing the time to first epidural supplement when adding clonidine to a 0.625 mg.ml(-1) bupivacaine continuous epidural infusion following epidural fentanyl bolus in early labor for patients allowed to ambulate. Maternal and fetal effects secondary to clonidine were also evaluated.

METHODS

Sixty-eight laboring primigravid women received a 3-ml epidural test dose of lidocaine with epinephrine, followed by a fentanyl 100-microg bolus (in a 10 ml-volume). The patients then received a 0.625 mg.ml(-1) bupivacaine continuous epidural infusion, either with or without clonidine (5 microg.ml(-1)), at a rate of 10 ml.h(-1). Pain scores and side effects were recorded for each patient.

RESULTS

The overall quality of analgesia was similar in both groups. The mean duration prior to request for additional analgesia was significantly longer in the clonidine group (269 +/- 160 min), compared to the control group (164 +/- 64 min). No patient in either group experienced any detectable motor block; one patient (clonidine group) complained of mild thigh numbness and was not allowed to ambulate. While mean blood pressure was approximately 6 mmHg lower in the clonidine group at 1, 1.5, and 3.5 h, this was not clinically significant. No adverse effects on maternal heart rate or fetal heart rate were noted.

CONCLUSION

In early laboring patients, addition of clonidine prolongs the analgesia duration of a 0.625 mg.ml(-1) bupivacaine continuous epidural infusion following 100 microg epidural fentanyl (after a lidocaine-epinephrine test dose) without a clinically significant increase in side effects.

Walking Epidural : An Effective Method of Labour Pain Relief

BACKGROUND

Labour pain can be deleterious for mother and baby. Epidural analgesia relieves labour pains effectively with minimal maternal and foetal side effects. A prospective open label study was undertaken to ascertain effective dosing regime for walking epidural in labour.

METHODS

Fifty women with singleton foetus in vertex position were included. Epidural catheter was inserted in L2-3 / L3-4 interspinous space. Initial bolus of 10 ml (0.1% bupivacaine and 0.0002% fentanyl) solution was injected and after the efficacy of block was established, an epidural infusion of the same drug solution was started at the rate of 5 ml/hour.

RESULTS

In first stage of labour 80% of the parturient had excellent to good pain relief (visual analogue scale 1 to 3) with standard protocol while 20% parturient required one or more additional boluses. For the second stage, pain relief was good to fair (VAS 4-6) for most of the parturient. The incidence of caesarian section was 4% and 6% needed assisted delivery. No major side effects were observed.

CONCLUSION

0.1% bupivacaine with 0.0002% fentanyl maximizes labour pain relief and minimizes side effects.

The Epidural Test Dose: A Review

This review systematically examines the literature on the ability of the classical epidural test dose and other strategies to detect intravascular, intrathecal, or subdural epidural needle/catheter misplacement. For detection of simulated intravascular misplacements, a sensitivity (S) and a positive predictive value (PPV) > or =80 demonstrated by at least two randomized controlled trials coming from two different centers were determined for the following tests and patient populations: Nonpregnant adult patients = increase in systolic blood pressure (SBP) > or =15 mm Hg (S = 80-100 and 93-100; PPV = 80-100 and 83-100) or either an increase in SBP > or =15 mm Hg or an increase in heart rate > or =10 bpm after the injection of 10 (S = 100; PPV = 83-100) or 15 microg of epinephrine (S = 100; PPV = 83-100); pregnant patients = sedation, drowsiness, or dizziness within 5 min after the injection of 100 microg of fentanyl (S = 92-100; PPV = 91-95); and children = increase in SBP > or =15 mm Hg after the injection of 0.5 microg/kg of epinephrine (S = 81-100; PPV = 100). Conversely, more studies are required to determine the best strategies to detect intrathecal and subdural epidural needle/catheter misplacements in these three patient populations.

Patient-controlled epidural analgesia during labor using ropivacaine and fentanyl provides better maternal satisfaction with less local anesthetic requirement

PURPOSE

To test the hypothesis that patient-controlled epidural analgesia (PCEA) using ropivacaine and fentanyl provides better maternal satisfaction and less anesthetic requirement than conventional continuous epidural infusion (CEI) during labor, we studied 58 uncomplicated parturients (singleton, vertex presentation).

METHODS

After establishing effective epidural analgesia with 11 ml of 0.2% ropivacaine, all parturients were randomly divided into one of two groups: the PCEA group (n = 29) or the CEI group (n = 29). In the PCEA group, the pump was initiated to deliver a basal infusion at 6 ml x h(-1) and a demand dose of 5 ml; the lockout interval was 10 min, and there was a 31 ml x h(-1) limit. The drugs used were 0.1% ropivacaine + fentanyl 2 microg x ml(-1). In the CEI group, epidural analgesia was maintained with the same solution as the PCEA group at a constant rate of 10 ml x h(-1). If parturients requested additional analgesia in the CEI group, we added 8 ml of epidural 0.2% ropivacaine without fentanyl.

RESULTS

Parturients' demographic data, such as duration of labor, mode of delivery, Apgar score, and umbilical arterial pH did not differ between the two groups. However, the hourly requirement of ropivacaine was significantly less in the PCEA group than in the CEI group (9.3 +/- 2.5 vs. 17.6 +/- 7.6 mg x h(-1); P < 0.05). Parturients' satisfaction assessed by the Visual Analogue Scale tended to be higher in the PCEA group than in the CEI group. Side effects such as nausea, hypotension, and itching were similar for the two groups.

CONCLUSION

We found that PCEA was an effective means of providing optimal analgesia, with better satisfaction during labor and less local anesthetic requirement.

Obstetric epidural test doses: a survey of UK practice

BACKGROUND

With the advent of low-dose epidural analgesia in labour, the content of the test dose has once again become the subject of debate.

METHOD

A postal survey of 500 members of the Obstetric Anaesthetists' Association was conducted in 1999-2000, assessing the use of test doses during epidurals in labour and for caesarean section.

RESULTS

There was a 67% response rate. Test doses are used in labour, at elective caesarean section and before epidural top-up for emergency caesarean section, by 90%, 93% and 37%, respectively. There was large variation in both drugs and doses. During labour, doses of bupivacaine range from 3 to 20 mg and of lidocaine 15 to 90 mg. There has been a three-fold increase in the use of low-dose local anaesthetic test doses since a previous national survey in 1997. The size of local anaesthetic test doses used at caesarean section is also variable. Epinephrine is used in 5% of labour, 14% of elective and 34% of emergency caesarean sections. Signs and symptoms that are commonly sought after test doses include somatic motor block, blood pressure change, sensory effect and symptoms from systemic local anaesthetic. The effect of the test dose is usually assessed after 5 min.

CONCLUSION

There is no consensus about the nature of the ideal test dose in obstetric anaesthesia. There is a trend to use less concentrated test doses during labour. Doses that risk a high block if given spinally are still used. Epinephrine, aspiration testing and cardiovascular monitoring are uncommon.

Are combined spinal-epidural catheters reliable?

The combined spinal-epidural (CSE) technique can rapidly relieve labor pain. However, the location of the epidural catheter is initially uncertain. In an emergency, this untested catheter may fail to provide adequate anesthesia. This study compared the efficacy of catheters placed as a part of an epidural or needle-though-needle CSE technique in laboring women. Patients requesting pain relief received either epidural (n=601) or CSE (n=1061) analgesia. All patients had a 20 gauge, closed tip multi-holed polyamide catheter. (B. Braun Medical, Inc.) inserted 2-8 cm into the epidural space. Catheters were tested to rule out intrathecal and intravascular location. Then, epidural patients received 10-20 ml local anesthetic +/- opioid in divided doses. CSE patients received and infusion of 0.083% bupivacaine with opioid at 10-15 ml/h. Of the 1495 catheters that were adequately tested, those inserted as part of a CSE technique were more likely to produce bilateral sensory change and adequate analgesia than were those inserted without prior spinal analgesia (98.6% vs 98.2%, P<0.02). Stand-alone epidural catheters were more likely to produce neither sensory change nor analgesia than those inserted as part of CSE technique (1.3% vs 0.2%, P<0.02). The only catheters that failed completely and were not intravascular were stand-alone epidural catheters. In this clinical setting, catheters inserted as part of a CSE technique had a high probability of being in the epidural space and functioning appropriately.

Automated intermittent epidural boluses improve analgesia induced by intrathecal fentanyl during labour

PURPOSE

We compared the efficacy of epidural continual intermittent boluses (CIB) with a continuous epidural infusion (CEI) in prolonging labour analgesia induced by the combined spinal epidural (CSE) technique.

METHODS

CSE was instituted in 42 nulliparous parturients at the L3 to 4 level with intrathecal (IT) fentanyl 25 micro g followed by an epidural test dose of 3 mL of 1.5% lidocaine. These parturients were then randomly assigned to receive either epidural CIB (n = 21) or CEI (n = 21) with 0.1% ropivacaine and fentanyl 2 micro g x mL(-1). For the CIB, 5 mL boluses were given hourly, with the first bolus 30 min postinduction. CEI at the rate of 5 mL.hr(-1) was initiated in the minute after CSE. The duration of analgesia, pain score, degree of sensorimotor block were compared.

RESULTS

From Kaplan Meier survival analysis, the duration of analgesia was significantly longer in CIB (mean survival time 239 +/- SD 24 min vs 181 +/- 17, P < 0.05 using log rank test). During the first three hours postblock, the median sensory block to cold was higher in CIB (P < 0.05, Mann U Whitney test) but no difference in blood pressure was detected [P > 0.05, repeated measure analysis of variance (RMANOVA)]. The serial pain scores were lower in the CIB (P < 0.05, RMANOVA).

CONCLUSION

CIB prolonged the duration and improved the quality of analgesia. CIB could have resulted in an improved spread of analgesics in the epidural space or encouraged a direct passage of infusate into the IT space. This could have also rendered a higher sensory block to cold in the CIB group. CIB is a good alternative to CEI for the maintenance of epidural analgesia after CSE.

Assessing bupivacaine 10mg/fentanyl 20μg as an intrathecal test dose

After ethics committee approval and verbal consent, women undergoing elective caesarean section given spinal anaesthesia with hyperbaric 0.5% bupivacaine 10 mg (2 mL) plus fentanyl 20 microg (spinal group, n = 20) and women requesting epidural analgesia in labour given the same drugs and doses epidurally, either in the same concentration (epidural small volume group, n = 10) or as 10 mL of 0.1% bupivacaine plus fentanyl 20 microg (epidural large volume group, n = 12) were recruited. The temperature of the great toes, sensory block on the outer ankle (S1 dermatome), motor block at the ankle and haemodynamic changes were recorded every 2 min for 10 min. There was a significant rise in foot temperature only in the spinal group. At four minutes a combination of warm toes and motor or sensory block, usually both, were seen only in the spinal groups. Haemodynamic changes were non-specific. We conclude that bupivacaine 10 mg with fentanyl 20 microg is a reliable agent to detect intrathecal placement by 4 min by which time a combination of motor and sensory block at the ankle and toe warming should be present.

The epidural test dose in obstetric anesthesia: it is not obsolete

Many anesthesiologists have called for the abandonment of the epidural test dose in the obstetric patient, citing its lack of sensitivity and specificity. A test dose of lidocaine 1.5% with epinephrine 1:200,000, in combination with aspiration, is highly effective in detecting incorrect placement of an epidural catheter. If the catheter is intrathecal, it requires approximately 2 minutes to obtain a sensory level. For the detection of an intravascular catheter, a positive test dose would result in a sudden increase in the maternal heart rate of 10 beats per minute within 1 minute after injection. It should not be administered during uterine contraction, as labor pain may trigger a tachycardic response. This test dose has been extensively studied and is safe both for both mother and fetus.

Diluent volume for epidural fentanyl and its effect on analgesia in early labor

Epidural fentanyl after a lidocaine and epinephrine test dose provides adequate analgesia and allows for ambulation during early labor. We designed the current study to determine the influence of the diluent volume of the epidural fentanyl bolus (e.g., whether it has an effect on the onset and duration of analgesia). Sixty laboring primigravid women received a 3-mL epidural test dose of lidocaine with epinephrine and then received a fentanyl 100- micro g bolus in either a 2-mL, 10-mL, or 20-mL volume. Pain scores and side effects were recorded for each patient. The onset of analgesia was similar in all three groups. The mean duration before re-dose was not significantly different in the 2-mL group (108 +/- 40 min), the 10-mL group (126 +/- 57 min), or the 20-mL group (126 +/- 41 min). No patient in any group experienced any detectable motor block; one patient (2-mL group) complained of mild knee weakness and was not allowed to ambulate. In early laboring patients, the volume in which 100 micro g of epidural fentanyl (after a lidocaine-epinephrine test dose) is administered does not affect the onset or duration of analgesia, nor does it affect the ability to ambulate.

IMPLICATIONS

In early laboring patients, the volume in which 100 micro g of epidural fentanyl (after a lidocaine-epinephrine test dose) is administered does not affect the onset or duration of ambulatory analgesia.

The effect of epidural test dose on motor function after a combined spinal-epidural technique for labor analgesia

Labor analgesia initiated with intrathecal bupivacaine and fentanyl, without a local anesthetic epidural test dose, provides effective analgesia and allows ambulation. In this study, we sought to determine the effect of a lidocaine-epinephrine test dose administered immediately after the initiation of combined spinal-epidural (CSE) analgesia with bupivacaine 2.5 mg and fentanyl 25 micro g on parturients' hemodynamic stability, posterior column function, motor strength, and subjective ability to walk. Parturients (n = 153) were randomized to receive either 3 mL of epidural saline or lidocaine 1.5% with epinephrine 1:200,000. Hemodynamic variables, proprioception, straight leg raise, and the modified Bromage score were analyzed in 110 parturients who completed the study protocol and were not different between groups. Vibratory sense, the ability to perform a partial deep knee bend and to step up on a stool, and the subjective ability to walk were impaired in a larger number of parturients in the lidocaine-epinephrine group at 30 min (P < 0.05). At 60 min, there were no differences between the groups except that fewer parturients in the lidocaine-epinephrine group could step up on a stool. The straight leg raise against resistance and the modified Bromage scale did not correlate well with other tests of motor strength (Spearman's rho, 0.273-0.405). These data suggest that the test dose should be avoided immediately after initiation of CSE analgesia when early ambulation is desired.

IMPLICATIONS

A lidocaine-epinephrine epidural test dose (3 mL of lidocaine 1.5% with epinephrine 1:200,000), injected immediately after the initiation of combined spinal-epidural labor analgesia with bupivacaine 2.5 mg and fentanyl 25 microg, may interfere with the ability to perform simple tests of motor function and ambulation.

New techniques and drugs for epidural labor analgesia

Several new techniques and medications are available for epidural labor analgesia. Two significant additions are ropivacaine and levobupivacaine. This article reviews the current applications of these drugs on the labor ward. The clinical implications of patient controlled epidural analgesia and ambulatory epidural techniques are discussed. The controversies surrounding epidural test dose and fluid preloading are examined.

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.

Lateral recumbent head-down posture for epidural catheter insertion reduces intravascular injection

PURPOSE

The unintentional and unrecognized cannulation of an extradural vein is a potentially serious complication of an epidural anesthetic. The present study was undertaken to assess the incidence of blood vessel puncture related to epidural catheterization performed in three different body positions.

METHODS

The study was conducted in 900 (three groups of 300) obstetric patients undergoing continuous epidural analgesia during their labour and who were randomly allocated to three groups. Epidural catheterization was performed with patients in the sitting, lateral recumbent horizontal, or lateral recumbent head-down position.

RESULTS

There was a lower incidence of vessel cannulation when this procedure was performed in the lateral recumbent head-down position (2%) than in the lateral recumbent horizontal (6%) and in the sitting position (10.7%).

CONCLUSION

Adoption of the lateral recumbent head-down position for the performance of lumbar epidural blockade, in labour at term, reduces the incidence of lumbar epidural venous puncture.

Obstetric anesthesia practice in Canada

PURPOSE

To describe obstetric anesthesia in Canada as practiced in 1997: to identify practices at variance with the literature and the opinions of experts: and to identify questions for future research.

METHODS

In 1997, a detailed postal questionnaire asking about the practice of obstetric anesthesia was mailed to all 1,539 specialist anesthesiologist members of the Canadian Anaesthetists' Society residing in Canada. Nonresponders were mailed a second questionnaire three months later

RESULTS

There were 865 completed questionnaires returned for analysis (56.2%). Of these, 522 anesthesiologists practiced obstetric anesthesia (60.3%). The data were subdivided into those from anesthesiologists with a full or part-time university based practice (40.1%) and those from a community based practice (59.9%). University based and community-based anesthesiologists have very similar patterns of practice. Specific areas where anesthesia practice was different from current recommendations included: (1) information provided when obtaining consent for labour epidural analgesia, (2) use of opioids and local anesthetics for initiation of epidural analgesia, (3) use of coagulation testing in preeclampsia, (4) the common use of cutting spinal needles, (5) use of neuraxial morphine and nonsteroidal anti-inflammatory agents after Cesarean deliveries, (6) optimal treatment of neuraxial opioid side effects, (7) when to insert an endotracheal tube for general anesthesia after delivery, and (8) withdrawing epidural catheters through epidural needles.

CONCLUSIONS

This survey presents reference data on the practice of obstetric anesthesia in Canada in 1997. Anesthesiologists with university affiliation have very similar practices to those without university affiliations.

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.