How Would You Place an Epidural Catheter in a Small Child?

Epidural catheters can be placed via an interlaminar (lumbar/thoracic) or caudal approach after induction of general anesthesia. For interlaminar placement, the child is typically placed in lateral position with hips and knees flexed and spine arched to open the interlaminar space. Loss of resistance to saline as opposed to air is considered to be safer in neonates and infants, as even a small volume of intravascular air can cause a clinically significant air embolus in an infant or small child.

What Is the Depth to the Epidural Space in Children?

The epidural space is extremely superficial in small children, with several guidelines used to estimate the distance.

The mean depth to the epidural space is 1 cm in neonates, ranging from 0.3 to 1.5 cm.

Between 6 months and 10 years of age, the epidural space is estimated to be 1 mm/kg body weight of depth.

For a caudal approach, an 18-gauge intravenous catheter is first inserted into the caudal space via the usual technique and a wire-reinforced epidural catheter is threaded into the desired space/level. The level of the catheter tip can be confirmed via ultrasound, and/or fluoroscopy.

Should a Test Dose Be Performed in Children under General Anesthesia?

Regardless of technique, careful aspiration for blood followed by a test dose using local anesthetic and epinephrine should be considered to exclude inadvertent subarachnoid or intravascular injection. Typically, a test dose is conducted with 0.5 mcg/kg of epinephrine or 0.1–0.2 mL/kg of lidocaine 1:200,000 solution.

The most suggestive sign of intravascular injection (100% sensitivity) is an EKG T-wave amplitude increase of >25%. Other signs include a systolic blood pressure increase of >15 mmHg or heart rate increase of >10 beats per minute with a sensitivity of 95% and 71% respectively.