Repeat epidural analgesia and unilateral block

Risk factors for epidural anesthesia blockade failure in cesarean section: a retrospective study

BACKGROUND

Epidural anesthesia (EA) is the regional anesthesia technique preferred over spinal anesthesia for pregnant women requiring cesarean section and post-operative pain control. EA failure requires additional sedation or conversion to general anesthesia (GA). This may be hazardous during sedation or GA conversion because of potentially difficult airways. Therefore, this retrospective study aimed to determine the risk factors for epidural failure during cesarean section anesthesia.

METHODS

We retrospectively analyzed parturients who underwent cesarean section under EA and catheterization at the Chang Gung Memorial Hospital in Taiwan between January 1 and December 31, 2018. Patient data were collected from the medical records. EA failure was defined as the administration of any intravenous anesthetic at any time during a cesarean section, converting it into GA.

RESULTS

A total of 534 parturients who underwent cesarean section were recruited for this study. Of them, 94 (17.6%) experienced EA failure during cesarean section. Compared to the patients with successful EA, those with EA failure were younger (33.0 years vs. 34.7 years), had received EA previously (60.6% vs. 37%), were parous (72.3% vs. 55%), and had a shorter waiting time (14.9 min vs. 16.5 min) (p < 0.05). Younger age (OR 0.91, 95% CI 0.86-0.95), history of epidural analgesia (OR 2.61, 95% CI 1.38-4.94), and shorter waiting time (OR 0.91, 95% CI 0.87-0.97) were estimated to be significantly associated with a higher risk of epidural anesthesia failure.

CONCLUSION

The retrospective study found that parturients of younger age, previous epidural catheterization history, and inadequate waiting time may have a higher risk of EA failure. Previous epidural catheterization increased the risk of EA failure by 2.6-fold compared to patient with no history of catheterization.

Analysis of Epidural Waveform to Determine Correct Epidural Catheter Placement After CSE Labor Analgesia

Background

The epidural pressure is pulsatile and synchronized with arterial pulsations. Monitoring the epidural waveform has been suggested as a technique to reliably confirm the appropriate localization of the epidural catheter.

Objective

The aim of this study was to evaluate the sensitivity and specificity of the Computer Controlled Drug Delivery System with continuous pressure and waveform sensing technology (CCDDS) (CompuFlo^® CathCheck™) as an instrument to assess the correct placement of the catheter in the epidural space in parturients who have received combined spinal-epidural technique (CSE) for labor analgesia.

Methods

We enrolled 40 consecutive healthy patients undergoing CSE labor analgesia with successful analgesia. All the cases in which pulsatile waveforms in synchrony with heart rate were detected were considered to be true positives; all the cases in which there was the absence of pulsatile waves were followed up. If these patients had to eventually relocate or manipulate the epidural catheter, they were considered to be true negative. If the absence of pulse waves was observed in the presence of successful analgesia during labor, the patients were considered to be false negatives.

Results

Pulsatile waveforms synchronous with heart rate were observed in 33 cases associated with adequate analgesia. In 5 cases, the pulsatile waveforms were absent due to unilateral analgesia or catheter occlusion (true negatives). In 2 cases, the patients had effective analgesia but we were not able to observe a distinct pulsatile waveform. The pressure waveform analysis through the epidural catheter had a sensitivity of 95%, a positive predictive value of 100%, a specificity of 100% and a negative predictive value of 60%.

Conclusion

Pulsatile pressure waveform recording with CCDDS through the epidural catheter resulted in high sensitivity and positive predictive value which can help the proper placement of the epidural catheter.

Epinephrine adjuvant reduced epidural blood vessel penetration incidence in a randomized, double-blinded trial

BACKGROUND

Accidental intravascular injection is a significant and potentially devastating risk of epidural block, particularly in parturients whose epidural veins are engorged and hence more easily pierced. This prospective randomized, double-blinded study determined whether the addition of epinephrine to epidural ropivacaine administered by gravity before catheter insertion was associated with fewer epidural catheter blood vessel penetrations.

METHOD

Four hundred and two parturient patients receiving epidural block for elective C/S were randomly allocated to two groups; group I (n = 201) received only ropivacaine 0.75% with fentanyl 5 μg/mL, whereas group II (n = 200) also received epinephrine 5 μg/mL. Both groups received a total of 21 mL anesthetic solution in four increment doses of 3,5,5,5 mL by gravity into the needle through a 22 inch extension tubing before insertion of the closed-end tip catheter. An additional 3 mL of the anesthetic solution was then administered through the catheter.

RESULTS

Epidural epinephrine adjuvant was associated with fewer epidural vessel penetrations (4% vs. 16.5%, P < 0.0001). The addition of epinephrine also significantly reduced catheter insertion problems (12% vs. 23.5%, P-value 0.0024) including the need for catheter readjustment (4.5% vs. 16%, P-value 0.0002) or reinsertion (2.5% vs. 9%, P-value 0.0054). The addition of epinephrine significantly reduced incidence and severity of sedation and had faster onset of surgical block. Sensory level and overall satisfaction did not differ significantly among the groups.

CONCLUSION

The addition of epinephrine to ropivacaine improves the safety and quality of epidural anesthesia when administered by gravity flow via the Hustead needle for cesarean sections.

Effects of epidural needle rotation and different speeds of injection on the distribution of epidural block

BACKGROUND AND OBJECTIVES

This prospective, randomised study examined the effect of injection speeds for unilateral epidural anesthesia on block characteristics, hemodynamic parameters, and discharge criteria in 60 patients. Levobupivacaine 5% was administered to Group F over 1 min (fast) and to Group S over 3 min (slow) (n=30 each) with the needle angulated at 5°-10° from the midline. Unilateral epidural block was significantly more successful in Group S than in Group F (70.3% vs. 16%; p<0.001). On the non-operated sides in group S, the maximal sensorial block time was shorter and the regression time for 2 segments was longer (p<0.05). And the walk-out time was longer in group F (p<0.05). We consider that the slow administration of local anesthetic in unilateral epidural anesthesia is more effective than rapid administration.

[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.

Prediction of the Distance from the Skin to the Lumbar Epidural Space in the Greek Population, Using Mathematical Models

BACKGROUND AND OBJECTIVES

The skin to lumbar epidural space distance (SLED) is variable, and therefore the ability to clinically predict the SLED may help increase the success of epidural anesthesia/analgesia. The goal of this study was to determine the relationship between the SLED and demographic/anthropometric variables in the Greek population, and develop a mathematical model for its prediction.

METHODS

This prospective randomized study enrolled 406 male and female Greek patients who required an epidural block as part of their anesthetic management. With patients placed in the left lateral and knee-chest position, the lumbar epidural space was located by the loss of resistance to normal saline technique. Statistical analysis was used to identify the relationship between SLED, and the following variables were evaluated: age, weight, height, body mass index, body surface area, intervertebral space used, pregnancy, and geographic origin within Greece.

RESULTS

No adverse events or dural punctures occurred. Mean SLED in the general population was 4.98 +/- 0.95 cm, with values significantly higher in males (5.37 +/- 0.88 cm) compared with females (4.83 +/- 0.93 cm). SLED was best associated with weight, body surface area, and body mass index. Mathematical formulae for prediction of SLED in the general population and the female population were derived from linear regression analysis. These formulae were able to predict approximately half of the observed variability in SLED.

CONCLUSIONS

While mathematical models of SLED can be a useful tool, they should not be exclusively relied on in the clinical setting, but rather should be used as an adjunct to standardized techniques to improve the safety and efficacy of epidural anesthesia/analgesia.

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.

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.

The influence of epidural needle bevel orientation on spread of sensory blockade in the laboring parturient

Both asymmetrical sensory blockade and dural puncture are undesirable outcomes of epidural analgesia. Identifying the epidural space with the needle bevel oriented parallel to the longitudinal axis of the patient's back limits the risk of headache in the event of dural puncture. However, rotating the bevel to direct a catheter cephalad may risk dural puncture. We prospectively studied the effects of needle rotation on the success of labor epidural analgesia and on the incidence of dural puncture. One hundred sixty ASA physical status I or II laboring parturients were randomly assigned to one of four groups. The epidural space was identified with the bevel of an 18-gauge Hustead needle directed to the patient's left. It was then rotated as follows: Group 0 = no rotation, final bevel orientation left (n = 39); Group 90 = rotation 90 degrees clockwise, bevel cephalad (n = 43); Group 180 = rotation 180 degrees clockwise, bevel right (n = 36); Group 270 = rotation 270 degrees clockwise, bevel caudad (n = 42). A single-orifice catheter was inserted 3 cm, and analgesia was induced in a standardized fashion. Dural puncture was evenly distributed among the groups (4.4%). There were more dermatomal segments blocked, fewer one-sided blocks, and more patients comfortable at 30 min with the needle bevel directed cephalad. Using a catheter inserted through a needle oriented in the cephalad direction increases the success of epidural analgesia.

IMPLICATIONS

This prospective study shows that an epidural catheter inserted through a needle oriented in the cephalad direction increases the success of labor analgesia in the parturient. Carefully rotating the needle cephalad does not increase the risk of dural puncture, intravascular catheters, or failed blocks.

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.