Epidural anesthesia in infants

Evaluation of a continuous epidural analgesia program for postoperative pain in children

A continuous epidural analgesia (CEA) program was developed for pediatric patients cared for outside of a critical care environment. Stable patients can be successfully monitored in the inpatient areas provided sufficient education and support is offered to allow for safe administration, monitoring, and evaluation of patient outcomes. The CEA program was developed in collaboration with the departments of nursing, anesthesiology, and pharmacy and was introduced on a 1-year trial basis on the surgical patient service unit. A retrospective record review was conducted of patients offered CEA over the first 2 years of the program to determine the safety and efficacy of the program. This article describes the development, implementation, and evaluation of the CEA program for surgical patients in a tertiary pediatric hospital. The safety and efficacy of the program as well as the benefits, challenges, and lessons learned are discussed.

Innovative approaches to neuraxial blockade in children: the introduction of epidural nerve root stimulation and ultrasound guidance for epidural catheter placement

Continuous epidural blockade remains the cornerstone of pediatric regional anesthesia. However, the risk of catastrophic trauma to the spinal cord when inserting direct thoracic and high lumbar epidural needles in anesthetized or heavily sedated pediatric patients is a concern. To reduce this risk, research has focused on low lumbar or caudal blocks (ie, avoiding the spinal cord) and threading catheters from distal puncture sites in a cephalad direction. However, with conventional epidural techniques, including loss-of-resistance for localization of the needle, optimal catheter tip placement is difficult to assess because considerable distances are required during threading. Novel approaches include electrical epidural stimulation for physiological confirmation and segmental localization of epidural catheters, and ultrasound guidance for assessing related neuroanatomy and real-time observation of the needle puncture and, potentially, catheter advancement. The present article provides a brief and focused review of these two advances, and outlines recent clinical experiences relevant to pediatric epidural anesthesia.

The Use of Electrical Stimulation to Monitor Epidural Needle Advancement in a Porcine Model

Muscle twitches elicited with electrical stimulation (ES) during epidural insertion may indicate epidural needle location. We examined the potential application of ES at 5 mA as a continuous method of monitoring the response to epidural needle advancement in a porcine model. Five 20-kg pigs were used in this study. A needle with a stimulating current of 5 mA was inserted at 20 separate levels in each pig. The needle was advanced until a muscle twitch was observed without loss-of-resistance (LOR). The needle position was then assessed using LOR. At the end of the experiment, an autopsy was performed to assess the spinal cord for injury. A total of 100 needle insertions were performed in the 5 pigs. The threshold current in the epidural space was 3.6 +/- 0.6 mA. In 59 of the needle insertions, LOR was not obtained at the depth at which a muscle twitch was initially observed. However, after advancing these 59 needles another 1-2 mm, LOR was obtained. In the other 41 insertions, LOR was observed without further advancement of the needle. Autopsies indicated there were no dural punctures or spinal cord damage in any of the pigs. These observations suggest that ES can be used to signal that the epidural needle is in or approaching the epidural space. However, the high false positive predictive value (59%) makes it impractical and unreliable to detect the precise entry of a needle into the epidural space in pigs.

The threshold current in the intrathecal space to elicit motor response is lower and does not overlap that in the epidural space: a porcine model

PURPOSE

Using electrical epidural stimulation, a current of 1 to 10 mA is required to confirm the presence of the tip of an epidural catheter in the epidural space. The purpose of this study was to examine the hypothesis that the threshold current required to elicit a motor response in the intrathecal space is significantly lower than that in the epidural space in a porcine model.

METHODS

Four 20-kg pigs were used in this experiment. Eighteen gauge, insulated, Tuohy needles were advanced into the epidural space using the loss of resistance technique at five different spinal levels in each pig. When the epidural space was entered, an electrical current was applied to the needle and increased progressively until a motor response was elicited. The needle was then further advanced until cerebrospinal fluid (CSF) was observed or until the needle had been advanced a maximum of 1 cm. At this point, the current was reapplied and increased until motor activity was evident.

RESULTS

A total of 20 needles were inserted in four pigs. The current required to produce a motor response in the epidural space was 3.45 +/- 0.73 mA (mean +/- SD). The current required to produce a motor response in the intrathecal space (entry confirmed by the presence of CSF) was 0.38 +/- 0.19 mA (mean +/- SD). Two needles were advanced 1 cm without obtaining CSF but the current thresholds were similar to those obtained when CSF was evident (0.4 mA and 0.3 mA, respectively).

CONCLUSION

The threshold current of an insulated needle required to elicit a motor response in the intrathecal space, was significantly (P < 0.01) lower than that in the epidural space in a porcine model.