1. Following the intravenous infusion of at least 1 to 2 litres of crystalloid solution, the mother is placed in the left lateral position, and a 16G 105mm length Tuohy needle is inserted into the epidural space at the L2 - L3 or L3 - L4 interspace, using loss of resistance to air or saline (Figure E.2).
2. A spinal needle of 26G or 27G and approximately 118 mm in length and with a Whitacre or pencil point (Figure E.1) (Chapter 59) is introduced through the Tuohy needle into the subarachnoid space (Figure 54.2). Slight resistance is detected as the spinal needle emerges through the tip of the Tuohy needle, and stronger resistance as the dura is pierced with a slight "pop".
3. After 5 to 10 secs, CSF appears at the needle hub and appropriate subarachnoid injection is made, taking care to stabilize the spinal needle. For labour ward analgesia, 25mcg (0.5ml) fentanyl may be added to 0.5ml bupivacaine 0.5% and made up to a volume of 2.0ml with normal saline. For caesarean section, 2.0 to 2.8mls bupivacaine 0.5% may be suitable. A similar dose of fentanyl (25mcg, 0.5ml) may be added if desired (Chapter 61).
4. The spinal needle is then removed and an epidural catheter is inserted to leave 3 to 4cms in the epidural space. Following secure fixation of the catheter, the patient is assisted into the right lateral position.
5. Careful patient monitoring is required as CSE can produce a more extensive block than either block alone (1).
6. The epidural catheter is available if extension of the block is required. Injection may be performed following negative aspiration and a negative test dose. It has been suggested that between 1.5 and 3ml of epidural local anaesthetic is required to extend the subarachnoid block by one segment; less volume than that required for a standard epidural block (1).
References:
1. RAWAL N, SCHOLLIN J, WESTROM G. Epidural versus combined spinal epidural block for cesarean section. Acta Anaesthesiol Scand 1988 32:61-66.