Of particular relevance in the history is the presence of cardiac disease (Chapter 83), pre-eclampsia (Chapter 39), coagulopathy, or any maternal condition which may present a relative contraindication to neuraxial blockade. The presence of any of these conditions may preclude the selection of the spinal and/or epidural route for analgesia or anaesthesia.
Informed consent must be obtained (Chapter 55).
Fasting (Chapter 26) and acid-aspiration prophylaxis (Chapter 80) should be observed in patients undergoing caesarean section.
The presence of a skilled assistant is essential (Document P14).
During the performance of the block and subsequently, careful attention to positioning will increase the likelihood of a succesful block (Chapter 30).
Large bore intravenous access and adequate prehydration will be required to minimise hypotension.
All equipment used for the insertion of an epidural must be sterile. The necessary equipment for the performance of epidural and spinal blockade is outlined in Table 44.1 and Table 44.2.
Either reusable or disposable Tuohy needles and syringes may be used. Tuohy needles feature blunt cutting tips whose ends are curved. This assists in identification of the epidural space without dural puncture. The commonly used sizes for obstetric analgesia are 16g and 18g. These needles accept 18 and 20 gauge catheters respectively.
Epidural catheters are typically made from PVC. The tip features either three helically-arranged lateral injection holes, or a single end hole (Figure 9.3). Three holed designs have been criticised for their potential to result in a malpositioned catheter such that individual holes may lie between different meningeal layers or in an epidural vein. This can result in a multi-compartment block (Figure 11.1) (Chapter 11) or inadvertent intravascular injection of local anaesthetic (Chapter 36). Single ended catheters have a higher incidence of false negative aspiration for blood and missed segments (1, 2, 3, 4).
Appropriate monitoring should be instituted. This should include monitoring of:
1. The maternal circulation (pulse rate and blood pressure).
Hypotension may complicate neuraxial blockade despite careful attention to prehydration (Chapter 6) and avoidance of aortocaval compression (Chapter 28). A baseline pulse rate and blood pressure must be obtained before initiating the block. Blood pressure should be measured at intervals of not more than 5 minutes during establishment of the block and thereafter hourly whilst the block is being maintained. During caesarean section the blood pressure should be measured at 5 minute intervals. A qualified person should be responsible for hemodynamic monitoring. Appropriate management of hypotension should be instituted early.
2. The level of the block.
The level of the block should be monitored as outlined in Chapter 8.
3. The fetus.
Methods of monitoring fetal wellbeing include:
a. Auscultation of heart rate with pinnards or doppler.
b. Graphical display of the cardiotocograph (Table 3.1).
c. The use of scalp electrodes.
d. Measurement of fetal scalp pH.
The fetus should be monitored whenever an epidural is being utilised. In uncomplicated labours this is usually accomplished with a cardiotocograph. Scalp electrodes are used when the cardiotocograph fails to generate a reliable trace or when fetal distress is present. This requires a sufficiently dilated cervix. Scalp pH is used to gain more information on fetal wellbeing when other signs of fetal distress are present.
4. Bladder function.
Painless bladder distension as the result of neural blockade may contribute to postpartum stress incontinence. This has been observed to occur in association with concentrations of bupivacaine of 0.5% (5). The bladder should be emptied intermittently.
References:
1. Beck H, Brassow F, Doehn M, et al: Epidural catheters of the multiorifice type: dangers and complications. Acta Anaesthesiol Scand. 1986; 30: 549
2. Morrison LMM, Buchan AS: Comparison of complications associated with single holed and multiholed extradural catheters. Br. J. Anaesth. 1990; 64:183.
3. Michael S, Richmond MN, Birks RJS: A comparison between open ended (single holed) and closed ended ( three lateral holes ) epidural catheters. Complications and quality of sensory blockade. Anaesthsia 1989; 44:578
4. Reynolds F; Epidural catheter migration during labour (letter). Anaesthesia 1988;43:69.
5. Thorburn J, Moir DD Extradural analgesia: the influence of volume and concentration of bupivacaine on the mode of delivery, analgesic efficacy, and motor block. Br.J. Anaesth. 1981; 53:933