A Comparison of Multiport and Uniport Epidural Catheters in Laboring Patients

Refinement of intrathecal catheter design to enhance neuraxial distribution

BACKGROUND

Delivery of therapeutics via indwelling intrathecal catheters is highly efficacious for targeting of pain, spasticity, neuraxial cancer and neurodegenerative disorders. However, current catheter designs have some major limitations. Given limited CSF flow, fixed intrathecal volume and the large distance of the rostro-caudal spinal axis, current intrathecal delivery routes fail to achieve adequate drug distribution. Additionally open catheter systems are plagued with cellular ingrowth and debris accumulation if used intermittently.

NEW METHOD

RESULTS/COMPARISON WITH EXISTING METHOD(S): High speed imaging showed micro-valve catheters greatly increase fluid exit velocities compared to typical open-ended catheters, which prevents pooling of injectate proximal to the opening. When implanted intrathecally in rats, small injection volumes (7.5 μL) of dye or AAV9-RFP, resulted in an even rostro-caudal distribution along the spinal axis and robust transfection of neurons from cervical to lumbar dorsal root ganglia. In contrast, such injections with an open-ended catheter resulted in localized distribution and transfection proximal to the delivery site. Our poly micro-valve catheter design resulted in equivalent transfection rates of cervical DRG neurons using 100x lower titer of AAV9-RFP. Unlike open port catheters, no debris accumulation was observed in the lumen of implanted catheters, showing potential for long-term intermittent use.

CONCLUSIONS

This catheter platform, suitable for small animal models is easily scalable for human use and addresses many of the problems observed with common catheter systems.

Ultrasound-guided continuous femoral nerve block: a randomized trial on the influence of femoral nerve catheter orifice configuration (six-hole versus end-hole) on post-operative analgesia after total knee arthroplasty

BACKGROUND

Multiorifice catheters have been shown to provide superior analgesia and significantly reduce local anesthetic consumption compared with end-hole catheters in epidural studies. This prospective, blinded, randomized study tested the hypothesis that, in continuous femoral nerve block (CFNB) under ultrasound guidance, multiorifice catheter would reduce local anesthetic consumption at 24 h compared with end-hole catheter.

METHODS

Eighty adult patients (aged ≥18 years) scheduled to undergo primary total knee arthroplasty under a combination of CFNB, sciatic nerve block and general anesthesia were randomized to CFNB using either a 3-pair micro-hole (Contiplex, BRAUN®, 20G - 400 mm) or an end-hole (Silverstim VYGON®, 20G - 500 mm) catheter. Once the femoral catheter was sited, a bolus of 20 mL lidocaine 1% was injected. An electronic pump then delivered an automated 5 mL bolus of ropivacaine 0.2% hourly, with 10 mL self-administered patient controlled analgesia boluses.

RESULTS

There was no inter-group difference in either median number of ropivacaine boluses on demand during the first 24 h (4(2-7) vs. 4(2-8) in six-hole and end-hole groups, respectively; P = 0.832) or median ropivacaine consumption at 48 h (365(295-418) vs. 387(323-466); P = 0.452). No significant differences were recorded between the groups at 24 h regarding median average verbal rate pain scale (2(0-3) vs. 2(0-4); P = 0.486) or morphine consumption (0(0-20) vs. 0(0-20); P = 0.749). Quadriceps muscle strength declined to 7% (0-20) and 10% (0-28) in the six-hole and end-hole groups, respectively, at 24 h after surgery (P = 0.733).

CONCLUSIONS

In this superiority trial, catheter orifice configuration did not influence the effectiveness of CFNB in this setting: quality of analgesia was similar, with no reduction in either local anesthetic or morphine consumption, and equivalent postoperative quadriceps weakness.

TRIAL REGISTRATION

Retrospectively registered at ( NCT03376178 ). Date: 21 November 2017.

Failure rate and complications associated with the use of spinal catheters for the management of inadvertent dural puncture in the parturient: a retrospective comparison with re-sited epidural catheters

Objective To report on the failure rate of spinal catheters placed following inadvertent dural puncture (IDP) compared with re-sited epidural catheters in the obstetric population. Research design and methods Patients who experienced IDP during epidural or combined spinal epidural placement with 17 or 18 gauge Tuohy needles for labor analgesia between 2003 and 2014 were identified using our post-dural puncture headache (PDPH) database. Patients were categorized into two groups: those who had spinal catheters inserted and those who had epidural catheters re-sited. Main outcome measure Failure rate associated with spinal or re-sited epidural catheters (defined as need for repeat block or alternative analgesic modality). Secondary outcomes were incidence of PDPH, need for epidural blood patch (EBP), and adverse events. Results A total of 109 patients were included in the final analysis; 79 ultimately had spinal catheters and 30 ultimately had re-sited epidural catheters. There were no differences between spinal catheters and re-sited epidural catheters in failure rate (22% vs. 13%, P = 0.33), incidence of PDPH (73% vs. 60%, P = 0.24), need for EBP (42% vs. 30%, P = 0.28), number of headache days, or maximum headache scores. There was also no difference in the rate of adverse events including high block levels, hypotension, and fetal bradycardia (9% vs. 7%, P = 1.0) between the two groups. Conclusions There were no differences in failure rates, PDPH outcomes, or adverse events between spinal catheters and re-sited epidural catheters following IDP in parturients receiving labor analgesia. Limitations of the study include its single-center retrospective non-randomized design, and the uneven number of patients in the two groups with a relatively small number in the re-sited epidural catheter group.

Epidural catheter design: history, innovations, and clinical implications

Epidural catheters have evolved during the past several decades, as clinicians and manufacturers have sought to influence the quality of analgesia and anesthesia and reduce the incidence of catheter-related complications. This evolution has allowed a transformation from single-shot to continuous-infusion techniques and resulted in easier passage into the epidural space, more extensive medication distribution, and ultimately, improved patient satisfaction. Particular catheter features, including the materials used, tip design, and orifice number and arrangement, have been associated with specific outcomes and provide direction for future development.

Comparison of Automated Intermittent Low Volume Bolus with Continuous Infusion for Labour Epidural Analgesia

Delivery of local anaesthetics via automated intermittent bolus has been shown to improve epidural analgesia compared to delivery via continuous epidural infusion. However, the optimal bolus volume has not been investigated. This randomised, double-blind study compared the analgesic efficacy of automated intermittent bolus (volume 2.5 ml every 15 minutes) with that of a continuous epidural infusion (10 ml/hour) for the maintenance of labour epidural analgesia, to determine whether the advantages previously demonstrated for automated intermittent bolus over continuous epidural infusion are retained at this low bolus volume. With the approval of the Hospital Ethics Committee, we recruited 50 parturients who received combined spinal epidural analgesia with intrathecal ropivacaine 2 mg and fentanyl 15 μg. For epidural maintenance, participants were randomised to either the automated intermittent bolus group (2.5 ml automated intermittent epidural boluses of ropivacaine 0.1% plus fentanyl 2 μg/ml delivered over a two-minute period every 15 minutes) or the continuous epidural infusion group (continuous epidural infusion of ropivacaine 0.1% plus fentanyl 2 μg/ml at 10 ml/hour). The primary study outcome was the incidence of pain during labour that required management with supplemental epidural analgesia. There were no significant differences between the two regimens in terms of breakthrough pain (automated intermittent bolus 36% [9/25] vs continuous epidural infusion 32% [8/25], P=0.77). At the doses used in this study, maintenance of labour analgesia using automated intermittent bolus at a bolus volume of 2.5 ml every 15 minutes does not decrease the incidence of breakthrough pain or improve analgesic efficacy compared to continuous epidural infusion.

Minimum current requirements for epidural stimulation test confirmation of epidural and intrathecal catheter placement

BACKGROUND AND OBJECTIVES

The typical blind insertion of a catheter into the epidural space risks catheter misplacement into the intrathecal space. The epidural stimulation test is designed to confirm the correct epidural location of a catheter but may also detect unintended intrathecal catheter placement by evaluating the minimum electrical current required for appropriate motor stimulation. Using this test, we observed the minimum current requirements for appropriate motor stimulation of catheters placed in the epidural and intrathecal spaces.

METHODS

In this prospective observational study, patients scheduled for epidural catheter placement and intrathecal catheter placement were evaluated by the epidural stimulation test. The epidural space was localized by using a loss-of-resistance technique with normal saline, and the intrathecal space was identified by advancing a Tuohy needle until a continuous flow of clear cerebrospinal fluid was obtained. Afterward, a catheter was placed in the appropriate space, and a nerve stimulator delivered progressively, increasing electrical current until an appropriate muscle contraction was palpated. The minimum milliamperage required for this muscle contraction was our primary outcome measure.

RESULTS

Of 37 catheters intentionally placed in the epidural space, the mean current required to produce an appropriate palpable motor contraction was 7.8 +/- 3.3 mA with a range of 2 to 14 mA. Of the 11 catheters intentionally placed in the intrathecal space, the mean current required to produce an appropriate palpable motor contraction was 1.3 +/- 0.8 mA with a range of 0.05 to 2.4 mA.

CONCLUSIONS

We conclude that the epidural stimulation test minimum electrical current requirement seems to be lower for intrathecal compared with epidural catheter placement.

[Failure of extension of epidural analgesia to anesthesia for emergency cesarean section]

Epidural analgesia provides effective control of labor pain and allows emergency cesarean section to be performed without recourse to general anesthesia. This technique is subject to failure, however. We sought to determine the incidence of failure of extension of epidural analgesia for labor to epidural anesthesia for emergency cesarean section. We also analyzed possible risk factors for failure. A 2-month observational study was carried out in a tertiary-care university hospital in patients who had an epidural catheter inserted for labor analgesia and who later underwent emergency cesarean section. Epidural catheter failure was defined if additional analgesia was required during surgery or if general anesthesia was required. Data were gathered on possible risk factors, such as obesity, difficult epidural puncture, leakage of blood on insertion, history of cesarean delivery, need for rescue analgesia, and level of satisfaction with analgesia during dilation. In total, 134 emergency cesareans were performed in women carrying an epidural catheter. The catheter failed to administer the anesthetic in 18 patients (13.4%). General anesthesia was required in 9 cases (6.7%). Difficult insertion (more than 2 attempts) was associated with a higher failure rate (P=.064). The relative risk of epidural catheter failure was 2.86-fold higher when rescue analgesia was needed during delivery than in cases when no supplement was required (P=.021). Receiving adequate analgesia during labor seems to be a protective factor (80%) against anesthetic catheter failure during cesarean section (P=.01). We conclude that high demand for rescue analgesia and signs of inadequate analgesia during labor should warn of epidural catheter failure if extension to anesthesia becomes necessary for a cesarean delivery.

A randomized prospective study comparing two flexible epidural catheters for labour analgesia

BACKGROUND

Previous studies evaluating stiff epidural catheters found that the three-holed design provided superior labour analgesia compared with an end-holed design. This was believed due to improved medication distribution. Recently, flexible epidural catheters with both designs have been shown to be superior to the stiff epidural catheters. We investigated the success of labour analgesia comparing the flexible three-holed with the flexible end-holed epidural catheter.

METHODS

This was a prospective, single-blinded randomized study. We enrolled 500 parturients in active labour. The primary outcome was complete relief of labour pain assessed at 30 min. We also assessed the occurrence of paresthesias, intravascular and intrathecal placement, catheter replacement, and treatment of breakthrough pain during labour. Comparisons were made using Pearson's chi(2), with significance determined at the 0.05 level.

RESULTS

Four hundred and ninety-three subjects completed the study. Initial analgesia was similar (complete labour analgesia: end-holed=85% vs 80% 95% CI of difference: 13% to -3%; P=NS). The incidence of paresthesia was similar (end-holed=3.6% vs 5.3%; P=NS). There was one intrathecal and three intravascular catheters in the three-holed group and two intravascular catheters in the end-holed group. The number of supplemental boluses and catheter replacements required during labour was similar between the groups.

CONCLUSIONS

There were no differences in the initial analgesia success rate, complications, or labour analgesia between end-hole vs multi-hole flexible epidural catheters.

A systematic review of randomized controlled trials that evaluate strategies to avoid epidural vein cannulation during obstetric epidural catheter placement

BACKGROUND

In this systematic review, we evaluated the evidence for seven strategies which have been proposed to minimize the incidence of epidural vein cannulation during lumbar epidural catheter placement in pregnant women.

METHODS

Multiple databases were searched to identify prospective, randomized, controlled trials between December 1966 and October 2007 that evaluated methods to avoid epidural vein cannulation after lumbar epidural catheter placement in pregnant women. Published trials were evaluated using a quality assessment tool, and results were combined to evaluate efficacy to prevent epidural vein cannulation.

RESULTS

Of 90 trials screened, 30 trials were included (n = 12,738 subjects). Five strategies reduce the risk of epidural vein cannulation: the lateral as opposed to sitting position (six trials, mean (sd) quality score = 35% [11%], odds ratio (OR) 0.53 [95% confidence interval (CI) 0.32-0.86]), fluid administered through the epidural needle before catheter insertion (8 trials, quality score 48% [18%], OR 0.49 [95% CI 0.25-0.97]), single rather than multiorifice catheter (5 trials, quality score 30% [6%], OR 0.64 [95% CI 0.45-0.91]), a wire-embedded polyurethane compared with polyamide epidural catheter (1 trial, 31%, plus 4 unscored abstracts, OR 0.14 [95% CI 0.06-0.30]) and catheter insertion depth < or =6 cm (2 trials, 47% [11%], OR 0.27 [95% CI 0.10-0.74]). The paramedian as opposed to midline needle approach and smaller epidural needle or catheter gauges do not reduce the risk of epidural vein cannulation.

CONCLUSION

The risk of intravascular placement of a lumbar epidural catheter in pregnancy may be reduced with the lateral patient position, fluid predistension, a single orifice catheter, a wire-embedded polyurethane epidural catheter and limiting the depth of catheter insertion to 6 cm or less. In general, low manuscript quality weakens the strength of these conclusions.

Detection of Intravascular Epidural Catheter Placement: A Review

Intravascular placement of an epidural catheter is recognised as a potentially fatal complication of epidural anaesthesia and analgesia. Up to 10% of epidural catheters may be inserted into an epidural vessel, the majority of which will be recognised; however, a proportion (1% of all epidural catheters inserted) may not be identified as lying intravascularly. Opinions differ on the optimal method for identifying intravascular catheters and no perfect method exists. Some debate the need for a test of correct location, as a lack of specificity may mean that a proportion of correctly located catheters are withdrawn and resited. This review outlines the incidence and risk factors associated with intravascular placement and aims to evaluate the detection methods that have been described, in an attempt to answer the question: “What is the optimal way of detecting intravascular placement of an epidural catheter?”

An In Vitro Comparison of the Electrical Conducting Properties of Multiport Versus Single-Port Epidural Catheters for the Epidural Stimulation Test

Effective conduction of electricity through a catheter is essential for the success of the epidural stimulation test. In this in vitro study we examined the electrical conductivity of single and multiport epidural catheters (with and without embedded metal elements) after being primed with normal saline. Seven different types of 19-gauge catheters (n = 5), either single-port or multiport catheters, with or without embedded metal elements, were studied. The proximal end of each epidural catheter was connected to the cathode of a nerve stimulator via an electrode adapter. The catheter, primed with normal saline, was placed at the bottom of a syringe filled with 5 different volumes of saline (1, 2, 3, 4 and 5 mL) and attached to an electrode adapter. The voltage of the peripheral nerve stimulator was measured using an oscilloscope. The electrical resistance between the proximal and distal end of the catheter was calculated using Ohm's Law. In catheters without metal elements the electrical resistances were too high to be measured. In catheters that had metal elements, the mean electrical resistances of the same catheter design (single-port or multiport) were similar. However, the electrical resistances of the multiport metal reinforced epidural catheters were significantly lower (P < 0.05) than the single-port metal coil reinforced epidural catheters. The volume of saline in the syringe had no impact on the measured electrical resistances. This study suggests that multiport metal reinforced epidural catheters have low electrical resistances and, thus, are a reasonable alternative to single-port catheters for transmitting sufficient current for performing the epidural stimulation test. On the other hand, epidural catheters without metal elements (single-port or multiport) are not suitable for performing the stimulation test.

Automated regular boluses for epidural analgesia: a comparison with continuous infusion

BACKGROUND

Intermittent epidural bolus dosing is a method of drug delivery that can prolong the duration of labour analgesia induced by a combined spinal epidural (CSE). In this randomized, double-blinded study, we compared the analgesic efficacy of two drug delivery systems: regular intermittent epidural boluses and continuous epidural infusion and assessed the incidence of breakthrough pain after CSE.

METHODS

With the approval of the Hospital Ethics Committee, we recruited 60 parturients into this randomized controlled trial. A CSE was performed with intrathecal fentanyl 25 mug in all patients. The parturients were then randomly allocated into two groups. The infusion group received a continuous epidural infusion of levobupivacaine 0.1% with fentanyl 2 microg/mL at a rate of 10 mL/h. The bolus group received 5-mL epidural boluses every half hour. The sample size was computed to detect a 40% reduction in the rate of breakthrough pain.

RESULTS

The bolus group had a lower incidence of breakthrough pain than the infusion group (10% vs. 37%, P < 0.05). The bolus group also had significantly higher satisfaction scores for labour analgesia: 97+/-8 (mean+/-SD) vs. 89+/-7 (P < 0.05).

CONCLUSION

Automated regular bolus delivery of epidural analgesia when compared with continuous infusion decreased the incidence of breakthrough pain and increased maternal satisfaction. In a busy obstetric unit, this may also serve to decrease the anesthetists' workload.

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.

Incidence and characteristics of failures in obstetric neuraxial analgesia and anesthesia: a retrospective analysis of 19,259 deliveries

A retrospective analysis was performed on 19,259 deliveries that occurred in our institution from January 2000 to December 2002. Anesthesia records and quality assurance data sheets were reviewed for the characteristics and failure rates of neuraxial blocks performed for labor analgesia and anesthesia. The neuraxial labor analgesia rate was 75% and the overall failure rate was 12%. After adequate analgesia from initial placement, 6.8% of patients had subsequent inadequate analgesia during labor that required epidural catheter replacement. Ultimately 98.8% of all patients received adequate analgesia even though 1.5% of patients had multiple replacements. Six percent of epidural catheters had initial intravenous placement but 46% were made functional by simple manipulations without higher subsequent failure. Unintended dural puncture occurred in 1.2% of labor neuraxial analgesia. The incidences of overall failure, intravenous epidural catheter, wet tap, inadequate epidural analgesia and catheter replacement were lower in patients receiving combined spinal-epidural versus epidural analgesia. For cesarean section, 7.1% of pre-existing labor epidural catheters failed and 4.3% of patients required conversion to general anesthesia. Spinal anesthesia for cesarean section had a lower failure rate of 2.7%, with 1.2% of the patients requiring general anesthesia. The overall use of general anesthesia decreased from 8% to 4.3% over the three-year period. Furthermore, regional anesthesia was used in 93.5% of cesarean deliveries with no anesthetic-related mortalities. Future investigations should identify acceptable international standards, risk factors associated with failure and methods to reduce failure before cesarean section.

Mechanisms and management of an incomplete epidural block for cesarean section

Epidural blockade is an important option for anesthesia in parturients undergoing abdominal delivery. Despite the multiple benefits of this method, there is at least one significant downside--a relatively high occurrence of unsatisfactory anesthesia that requires intervention. Depending on the presumed mechanism of epidural block failure and other clinically relevant factors (e.g., timing of diagnosis, urgency of the procedure, and so forth), certain effective measures are recommended to successfully manage this demanding situation. In general, it is important to make every effort to make the pre-existing epidural effective or replace it with another regional technique, because overall, regional anesthesia is associated with significantly lower maternal mortality. It is important to identify a dysfunctional epidural block preoperatively before a maximum volume of local anesthetic has been administered. If catheter manipulation does not produce substantial improvement, and there is no time constraint, it is safe and reasonable to replace the epidural catheter. However, risks associated with excessive volume of local anesthetic should be kept in mind. Additional epidural injections or a second catheter placement might be considered under special circumstances. Single-shot spinal anesthesia after a failed epidural may provide fast onset and reliable surgical anesthesia. Available data, although limited and contradictory, suggest the possibility of unpredictably high or total spinal anesthesia. Many authors, however, believe that appropriate precautions and modifications in technique make this a safe alternative. These modifications include limiting the amount of epidural local anesthetic administered when diagnosing a nonfunctioning epidural and decreasing the dose of intrathecal local anesthetic by 20% to 30%. If there is no documented block when the spinal is inserted, and more than 30 minutes have passed from the last epidural dose, it is probably safe to use a normal dose of local anesthetic. Continuous spinal anesthesia with a macro catheter might be a dependable alternative, particularly if large amounts of local anesthetic have already been used or the patient's airway is a cause for concern. Although there are no reports of combined spinal epidural anesthesia being used in this context, it would appear to be an attractive alternative. It allows the anesthesiologist to give smaller doses intrathecally, while still offering the flexibility of augmenting the block if needed. When inadequate epidural block becomes apparent during surgery there are limited alternatives. Depending on the origin and the pattern of inadequate anesthesia, options may include psychological support, supplementation with a variety of inhalational and intravenous agents, and local anesthetic infiltration. Induction of general anesthesia is typically left as a backup option, but must be strongly considered if the patient continues to have pain/discomfort.

Predictors of breakthrough pain during labor epidural analgesia

Parturients who receive labor epidural analgesia may experience breakthrough pain that requires supplemental medications. We investigated the factors associated with breakthrough pain. This prospective observational study included 1963 parturients who received epidural analgesia. Subjects were categorized into two groups on the basis of the number of episodes of breakthrough pain: the Recurrent Breakthrough Pain (RBP) group experienced three or more episodes. Univariate and multivariate regression analyses were used to evaluate factors associated with the RBP group. By multivariate analysis, nulliparity, heavier fetal weight, and epidural catheter placement at an earlier cervical dilation were found to be independently associated with the RBP group. These factors may predict which parturients' analgesia may be complicated by breakthrough pain. Parturients who received a combined spinal/epidural technique were less likely to be associated with the RBP group. The combined spinal/epidural technique may be superior to conventional epidural anesthesia, because breakthrough pain occurred less often. It is interesting to note that the characteristics that are associated with the RBP group are similar to those that have been associated with increased severity of maternal pain.

IMPLICATIONS

Nulliparity, heavier fetal weight, and epidural catheter placement at an early cervical dilation are predictors of breakthrough pain during epidural labor analgesia. The combined spinal/epidural technique may be associated with a decreased incidence of breakthrough pain.

Improved epidural analgesia in the parturient in the 30 degree tilt position

PURPOSE

To compare the incidence of incomplete analgesia when epidural local anesthetic is administered with the parturient supine in a 30 degree leftward tilt or in the left lateral decubitus position.

METHODS

After placement of a multiorifice catheter 5 cm into the epidural space, 293 women in active labour were randomly positioned either to the left lateral decubitus position (lateral group) or supine with a 30 degree leftward tilt (tilt group) and then received 13 mL bupivacaine 0.25%. The success of the epidural block was determined by asking the patient if she required additional medication 15 min later. The incidence of complications (fetal heart rate decelerations, hypotension, and ephedrine usage) was noted.

RESULTS

In the lateral group, 38% required additional medication compared with 24% in the tilt group (P = 0.006). There were no differences between groups in the incidence of maternal hypotension or fetal heart rate decelerations, but more women (10%) received ephedrine in the lateral than in the tilt group (4%), P = 0.035.

CONCLUSIONS

Placing the parturient supine with a 30 degree leftward tilt is associated with a greater success rate of labour epidural analgesia without an increase in complications than in women in the left lateral decubitus position. This advantage should be considered when positioning the parturient after epidural catheter placement.

New developments in epidural anesthesia and analgesia

Several recent advances in epidural anesthesia and analgesia have been reviewed. Perhaps the most exciting area of anticipated future developments relates to the continued development of novel analgesic agents and new epidural delivery systems. There appears to be some movement toward an increased use of intrathecal or peripheral neural blockade techniques for some clinical situations where epidural anesthesia and analgesia have been previously used; however, the ability to provide anesthesia and analgesia to relatively large areas of the body with a single injection or continuous catheter technique without the associated risks of dural puncture and intrathecal catheter placement will continue to assure epidural anesthesia and analgesia techniques a prominent role in anesthesia and pain management.

Uniport soft-tip, open-ended catheters versus multiport firm-tipped close-ended catheters for epidural labor analgesia: a quality assurance study

STUDY OBJECTIVE

To compare a multiport, firm-tipped, close-ended, epidural catheter (Portex catheter) with a uniport, open-ended, soft-tipped, wire-reinforced catheter (Arrow catheter) in obstetric patients.

STUDY DESIGN

Prospective data collection for intradepartmental quality assurance.

SETTING

Obstetric unit in a tertiary care maternity hospital.

PATIENTS

2612 patients requesting labor analgesia.

INTERVENTIONS

The Arrow catheter was used in 1,352 women and the Portex catheter in 1,260 women.

MEASUREMENTS AND MAIN RESULTS

The incidence of unsatisfactory block were 3.3% and 4.4% with the Arrow and Portex catheters, respectively (p = 0.2). The catheter perforated the dura matter in 0.4% of cases with both catheters. The incidence of epidural venipuncture was 1.1% with the Arrow catheter and 5.7% with the Portex catheter (p = 0.0001). Paresthesias occurred in 6% of cases with the Arrow catheter and 11. 2 % of cases with the Portex catheter (p = 0.0001). Epidural catheter reinsertion was required in fewer patients in the Arrow group than in the Portex group (4.8% vs. 7.1%; p = 0.01).

CONCLUSIONS

In obstetric patients, the softer uniport Arrow catheter produces paresthesias and venipunctures less frequently than the firm multiport Portex catheter.

An in vitro evaluation of flow from multihole epidural catheters during continuous infusion with four different infusion pumps

We have observed in vitro the distribution of flow from 10 identical multihole epidural catheters during continuous infusion with four different infusion pumps. The pumps chosen were the B Braun Perfusor Secura FT syringe driver and three volumetric infusion pumps utilising different pumping mechanisms (Dekra 3000 BL, Graseby 500 and CADD-Prizm). These pumps infused 0.9% saline through each catheter at 5 ml.h-1, 15 ml.h-1, 50 ml.h-1 and 99 ml.h-1 for 3 min. The number of holes through which flow occurred and the catheter hole where flow predominated during each test were recorded. The pressure waveform generated during each infusion was displayed and the peak pressure recorded. In 38 of the 160 tests (24%) the largest proportion of flow was seen at the hole closest to the catheter tip. The CADD pump generated multihole flow during significantly more tests (p < 0.0001) than the other pumps and produced significantly higher driving pressures (p < 0.001) at all infusion rates compared with the Graseby and Perfusor pumps. The CADD was the only pump to produce flow from all three holes of the catheter at 5 ml.h-1.

Spinal clonidine prolongs labor analgesia from spinal sufentanil and bupivacaine

We sought to determine whether spinal clonidine 50 microg prolongs the analgesia from the spinal administration of sufentanil 7.5 microg and bupivacaine 2.5 mg early in the first stage of labor. Thirty patients were randomized to receive a 2-mL spinal injection of sufentanil 7.5 microg + bupivacaine 2.5 mg with or without clonidine 50 microg using a combined spinal-epidural (CSE) technique. Pain, nausea, pruritus, sedation, motor block, blood pressure, and heart rate were assessed until the patient requested additional analgesia. Analgesia was significantly prolonged in patients who received spinal sufentanil + bupivacaine + clonidine (197 +/- 70 vs 132 +/- 39 min; P = 0.004). Pain scores and side effects, including motor block, sedation, and hypotension, were similar between groups. Spinal clonidine significantly prolongs labor analgesia from spinal sufentanil and bupivacaine without producing serious adverse side effects.

IMPLICATIONS

We studied the effects of spinal clonidine administered with spinal sufentanil and bupivacaine on labor analgesia using a combined spinal-epidural technique and conclude that spinal clonidine significantly prolongs labor analgesia from spinal sufentanil and bupivacaine without producing serious adverse effects.

Risk factors of inadequate pain relief during epidural analgesia for labour and delivery

PURPOSE

To determine the causes of failure of epidural analgesia during labour and delivery.

METHODS

During six months, pregnant patients receiving epidural analgesia and delivering vaginally were studied prospectively. Bupivacaine 0.125% was used for the initial bolus dose and subsequent continuous infusion. Top-ups of the same solution were used for inadequate pain relief assessed using a visual analogue pain score (VAPS) and/or by clinical examination. Inadequate pain relief was defined as the need for > or = 2 top-ups in addition to epidural infusion and failure during delivery as VAPS > or = 30 mm during the expulsion phase.

RESULTS

1009 patients delivered during this period, 596 had epidural analgesia for vaginal delivery of a live infant and data were complete in 456. Inadequate pain relief during labour and during delivery were found in 5.3% and 19.7% of patients. Risk factors of inadequate pain relief included: inadequate analgesic efficacy of the first dose (Odds ratio: 3.5, P = 0.001) and posterior presentation (Odds ratio: 5.6, P = 0.001). Radicular pain during epidural placement was associated with failure during labour (Odds ratio: 3.9, P = 0.05). Duration of epidural analgesia > six hours (Odds ratio: 9.1, P = 0.001) was a risk factor for insufficient pain relief during labour whereas duration of epidural analgesia < one hour was associated with pain during delivery (Odds ratio: 18.3, P = 0.001).

CONCLUSION

Several obstetrical and epidural-related factors increase the risk of inadequate epidural analgesia. For some, simple changes of practice pattern may lead to improved pain relief.