Identification of the epidural space in children. The application of a micro-drip infusion set

Epidural space "ballooning" during local anaesthetic injection in infants and children: An ultrasound observational study

BACKGROUND

Infants and children require a larger dose of a local anaesthetic (LA) to establish epidural analgesia than adults, but the reason for this remains unclear. We hypothesised that prominent ventro-dorsal expansion of the epidural space limits cranio-caudal spread of LA in infants. Accordingly, we studied the dimensions of the epidural space with real-time ultrasound (US) before and after epidural injection.

METHODS

Ninety-six infants and children aged 0-12 years who underwent abdominal surgery under combined epidural and general anaesthesia were examined in this prospective observational study. Using a micro-convex probe, US recordings of the posterior epidural space were performed while a LA (0.5 ml kg^-1 ) was infused at 0.54 ml s^-1 . The width in the ventro-dorsal dimension (VDD) of the posterior epidural space before and after injection was recorded; the change in VDD was defined as "ballooning". Correlations between "ballooning" and patient age, body mass index, and volume and rate of LA administration were analysed.

RESULTS

"Ballooning" correlated positively but weakly with age (R²  = 0.25; p < .001) and the infused LA volume (R²  = 0.32; p < .001). The "magnitude of ballooning" ("ballooning" per ml of injected LA) correlated negatively but weakly with age (R²  = 0.27; p < .001).

CONCLUSIONS

"Magnitude of ballooning" of the epidural space become inconspicuous with growing during epidural injection. This effect may slow the cranio-caudal spread of LA and explain partially why larger volumes of LA are required to effect a block in children.

From the Journal archives: Epidural anesthesia in young children: what have we learned in the past 60 years?

Francis G. Ruston MD CITATION: Ruston FG. Epidural anaesthesia in infants and children. Can Anaesth Soc J 1954: 1: 37-44.

PURPOSE

The author describes the use of single-shot epidural anesthesia in a series of 44 infants and children. The patients were anesthetized in hospitals in Hamilton, Ontario from 1949 until the time of publication in 1954. The study aimed to describe the indications and efficacy of this technique as well as any apparent complications. A detailed description of the management of these patients was given, including many tips and suggestions that are still applicable in 2013.

PRINCIPAL FINDINGS

Seventy-seven infants and children received epidural anesthesia for a variety of procedures, particularly for pyloric stenosis. Forty-four of the procedures were carried out by the author. All patients survived, apart from one child who died of recurrent intestinal obstruction unrelated to the anesthetic. It was found, after some experience, that the sitting position was preferable for epidural needle insertion. Use of the hanging drop technique for identification of the epidural space proved to be simple and reliable. Surgical conditions were found to be excellent and relaxation was profound; however, some sedation was often required to obtain optimal conditions for surgery. The surgeons became sold on the technique and began to request an epidural on a regular basis.

CONCLUSIONS

Epidural anesthesia in infants and young children is effective for a variety of procedures below the diaphragm, even in moribund patients.

Pro con debate: the use of regional vs systemic analgesia for neonatal surgery

In recent years the inclusion of regional techniques to pediatric anesthesia has transformed practice. Simple procedures such as caudal anesthesia with local anaesthetics can reduce the amounts of general anesthesia required and provide complete analgesia in the postoperative period while avoiding large amounts of opioid analgesia with potential side effects that can impair recovery. However, the application of central blocks (epidural and spinal local anesthesia) via catheters in the younger infant, neonate and even preterm neonate remains more controversial. The potential for such invasive maneuvers themselves to augment risk, can be argued to outweigh the benefits, others would argue that epidural analgesia can reduce the need for postoperative ventilation and that this not only facilitates surgery when intensive care facilities are limited, but also reduces cost in terms of PICU stay and recovery profile. Currently, opinions are divided and strongly held with some major units adopting this approach widely and others maintaining a more conservative stance to anesthesia for major neonatal surgery. In this pro-con debate the evidence base is examined, supplemented with expert opinion to try to provide a balanced overall view.

Epidural catheter malposition in a failed epidural anesthesia confirmed by computed tomography

We report a case of failed epidural anesthesia despite successful identification of the epidural space, loss of resistance technique, hanging drop method and drip infusion. This case evaluated the use of computed tomography to confirm epidural catheter position, which showed the catheter accidentally positioned at the T2 lamina. Because epidural anesthesia can even after successful procedure using standardized techniques such as loss of resistance, we recommend performing the procedure under fluoroscopic guidance to improve success rate and patient safety.

Epidural loss-of-resistance biomechanics: an open pilot cadaver study

Purpose

We measured dynamic biomechanics of loss-of-resistance (LOR) epidural placement in prone cadavers, focussing on the period immediately following LOR, to estimate forces acting on the tissue of the epidural space.

Methods

An epidural syringe with 17G Hustead needle was instrumented to track force on the plunger, pressure in the chamber, and movement of barrel and plunger. Insertions were attempted in five formalin-preserved cadavers from T2–3 to L4–5, using LOR with saline or air, and confirmed with X-ray.

Results

Sixteen insertions were successful. Soft tissues in formalin-preserved cadavers are much harder than in living humans. With continuous pressure on the plunger, fluid thrust through the needle at the point of LOR was significantly greater (P = 0.005) with saline (mean ± standard deviation [95% confidence intervals]: 19.3 ± 14.9 [8.3 to 30.3] N); than with air (0.17 ± 0.25 [0 to 0.39] N). Stress exerted on epidural tissue was similar (air = 7792 ± 920 [6986 to 8598] Pa; saline = 7378 ± 3019 [5141 to 9614] Pa); and in both cases was greater than the stress exerted by cerebrospinal fluid pushing outwardly on the dura (4800 Pa).

Conclusion

Formalin-preserved cadavers are too stiff to make them an experimental model from which we can generalize to live humans, although we were successful in entering the epidural space and testing the instrumentation for further studies on live animals or humans. Continuous pressure on the plunger while advancing the epidural needle may “blow” the dura away from the needle tip and help prevent dural puncture. Better results are seen with saline rather than air.

Accuracy of the epidural catheter position during the lumbar approach in infants and children: a comparison among L2-3, L3-4, and L4-5 approaches

Background

The aim of this study was to compare the accuracy of the position of the epidural catheter inserted from three different lumbar intervertebral spaces, L2-3, L3-4, and L4-5, in infants and children.

Methods

Seventy-five children were randomly allocated to 3 groups according to the epidural catheter insertion site (L2-3, L3-4, and L4-5). The epidural catheter tip was identified using 50% diluted Iohexol and fluoroscopy. The incidence of correct position was compared among the groups and between infants and children.

Results

The incidence of correct position was significantly higher in the L2-3 group as compared to the L3-4 and L4-5 groups (P = 0.023 and P = 0.046 respectively). The incidence of correct position was higher in infants compared to children (P = 0.017).

Conclusions

The L2-3 intervertebral space is preferable during epidural catheter insertion in children older than 1 year, but a low lumbar level should be considered in infants because they have a higher risk of neural damage.

Drip infusion method as a useful indicator for identification of the epidural space

BACKGROUND

Cervical epidural anesthesia (CEA) is used for pain control and surgical procedures of the head and neck or upper arm areas. However, the failure rate of CEA is reported to be high, is the failure rate being quite higher than other sites, because of the anatomical differences of the cervical spine. We hypothesized that the loss of resistance (LOR) method combined with the drip infusion method for confirmation of the cervical epidural space can reduce the failure rate. This study investigated the usefulness of the drip infusion method.

METHODS

One hundred chronic renal failure patients undergoing arteriovenous bridge graft for hemodialysis at the upper arm under cervical epidural anesthesia were recruited for this study. In the cervical epidural puncture, we identified the cervical epidural space using a combination of the LOR method with the drip infusion method. After confirmation of the epidural space with LOR method, we decided it was the true epidural space when fluid dripping to the space was present. Otherwise, if fluid dripping was not present, we designated it was pseudo LOR, and we found the true epidural space using the drip infusion method only.

RESULTS

In all cases, the combined LOR with drip infusion method, identify the epidural space.

CONCLUSIONS

Combined LOR with drip infusion method is an efficacious method for the confirmation of the cervical epidural space.

Loss of resistance to normal saline is preferred to identify the epidural space: a survey of Canadian pediatric anesthesiologists

PURPOSE

Several methods have been described to locate the epidural space, but the loss-of-resistance (LOR) technique is the most commonly used. Expert opinion states that LOR to air is the best medium for neonates and infants. We conducted a Canada-wide postal survey to determine the current state of practice for placement of epidural catheters in pediatric patients.

METHODS

Two hundred and nine surveys were distributed to academic pediatric anesthesiologists across Canada. The survey was limited to six questions and was anonymous.

RESULTS

The response rate was 62.2%. LOR was the method of choice for 124/130 anesthesiologists (95.4%). LOR to normal saline was the medium of choice for all age groups, although LOR to air and LOR to air/saline gained in popularity with increasing patient age. The majority of anesthesiologists do not change their LOR technique for different patient ages or level of epidural insertion. Most responders ranked 'training' as the most important determinant of practice, whereas 'departmental guidelines' were considered the least important. No complication attributable to the LOR technique used was reported.

CONCLUSION

LOR to normal saline is the preferred method for identification of the epidural space in children of all age groups. The suggestion by experts that LOR to air should be used in neonates and infants was not supported by the practice of pediatric anesthesiologists across Canada.

Skin-epidural distance in children

The skin-epidural distance was measured in 274 children to assess the usefulness of 1 mm.kg-1 as a guideline. Children aged between 2 days and 16 years, weighing between 2 and 43 kg were investigated. Lumbar epidurals were performed under general anaesthesia using a midline approach in the L3-4 interspace with the patient in the lateral position. Good correlation between skin-epidural distance and age and weight was demonstrated. No statistical difference was shown when plotting the best fit regression line: skin-epidural distance (mm) = 0.8 weight (kg) + 3.93 (R2 = 0.74) and its 95% confidence limits and skin-epidural distance (mm) = weight (kg) for children between 6 months and 10 years. Poor correlation was noted below 6 months (n = 22) and over 10 years (n = 19). No dural puncture or bloody tap occurred. One mm.kg-1 body weight was shown to be a useful guideline for children between 6 months and 10 years of age.

Sacral intervertebral approach for epidural anaesthesia in infants and children: application of "drip and tube" method

Sacral intervertebral approach to the epidural space was introduced as an alternative to the caudal approach in infants and children in 1987. We performed single-shot epidural anaesthesia in 200 infants and children with this approach using the "drip and tube" method for identification of the epidural space. Identification of the epidural space was marked by commencement of dripping in the chamber of a micro-drip infusion set which was connected to the epidural needle. With the i.v. extension tube, local anaesthetic solution was injected by the "immobile needle" technique. Overall success rate of the block was 96%. This approach to the epidural space is anatomically easy in infants and children, and application of our "drip and tube" method might make the paediatric single-shot epidural anaesthesia safer and more successful.

Continuous epidural analgesia in newborn infants undergoing major surgery

Providing safe, effective analgesia for newborn infants undergoing major surgery remains a challenge to pediatric anesthetists and surgeons. Continuous epidural analgesia (CEA) has been shown to provide safe and effective analgesia in infants and children; however, there is little reported use in neonates. We review our experience of CEA in 14 newborn infants (32 to 40 weeks gestation) aged 4 hours to 35 days undergoing major surgery, as well as a further 6 ex-preterm (25 to 29 weeks gestation) infants aged 2 to 5 months at time of surgery. In all cases effective analgesia was achieved for up to 69 hours without complication. All infants were awake and extubated uneventfully at the completion of surgery, which lasted 5 hours in one case. None of the infants developed respiratory depression or prolonged apnea. The technique has been widely accepted by surgeons, neonatal nursing staff, and neonatologists.