PCEA in Labor.
Many studies have indicated that use of a background infusion for PCEA during labor is not necessary for most women (1, 2, 3, 4, 5, 6, 7). Indeed, it has been demonstrated that bolus-only PCEA is very effective without a background infusion and is superior, in some aspects, to a continuous epidural infusion or intermittent top-up injections. To date, only one study has suggested that a background infusion would be beneficial with PCEA during labor because a reduced need for supplemental analgesia was demonstrated (8). However, in the original study comparing PCEA with or without a background infusion, Paech (Chapter 60) found no benefit from the addition of a background infusion (9). Many clinicians start PCEA without a background infusion because dose-sparing is associated with a reduction in local anesthetic and opioid side-effects. A reasonable approach to dosing with PCEA is to use 0.125% bupivacaine with 2mcg/ml fentanyl. Satisfactory analgesia can be achieved using a 4 ml bolus dose and a lockout interval of 15 minutes.
Epidural PCA after cesarean birth.
The first study of PCEA following cesarean birth, by Parker and White, described it as a safe, effective alternative to intravenous PCA with less opioid use and more rapid recovery (10). In a follow-up study, the same investigators found that the efficacy of PCEA was not improved by adding a background infusion (11). In fact, a basal infusion of hydromorphone and dilute bupivacaine resulted in leg weakness and a higher incidence of postoperative nausea and pruritus. The use of a 10 ml per hour background infusion of buprenorphine and bupivacaine with PCEA probably contributed to difficulty in ambulation in 43% of patients in another study of post-cesarean analgesia (12). Other studies have confirmed that PCEA without a background infusion can provide adequate analgesia after cesarean birth, using either fentanyl (13) or meperidine (14).
In summary, most studies have indicated that a background infusion is not required for PCEA. The addition of a background infusion introduces a form of drug delivery that is physician-controlled (not patient-controlled). This defeats the purpose of the PCA concept, which acknowledges that it is the patient who knows how much pain is tolerable and conversely how much analgesia is adequate.
It was felt by some that a background infusion for night-time use would overcome the problem of patients sleeping and being unable to keep up with dosing requirements. This is not as big an issue in obstetrics because 1. during labor the parturient is often woken regularly for vital signs and other evaluations, and 2. after cesarean delivery a mother is often disturbed to feed her newborn or by routine vital sign measurements. In both cases she will have ample opportunity to self-administer a PCA bolus as required.
References:
1. Gambling DR, McMorland GH, Yu P, Laszlo C. Comparison of patient controlled epidural analgesia and conventional intermittent "top-up" injections during labor. Anesth Analg 1990; 70: 256-261.
2. Ferrante FM, Lu L, Jamison SB, Datta S. Patient-controlled epidural analgesia: Demand dosing. Anesth Analg 1991; 73: 547-552.
3. Purdie J, Reid J, Thorburn J, Asbury AJ. Continuous extradural analgesia: Comparison of midwife top-ups, continuous infusions and patient-controlled administration. Br J Anaesth 1992; 68: 580-584.
4. Gambling DR, Huber CL Berkowitz J et al. Patient-controlled epidural analgesia in labour: Varying bolus dose and lockout interval. Can J Anaesth 1993; 40: 211-217.
5. Paech ML Patient-controlled epidural analgesia during labor: Choice of solution. Int J Obstet Anesth 1993; 2: 65-71.
6. Tan S, Reid J, Thorburn J. Extradural analgesia in labour: complications of three techniques of administration. Br J Anaesth 1994; 73: 619-6
7. Curry PD, Pacsoo C, Heap DG. Patient-controlled epidural analgesia in obstetric anaesthetic practice. Pain 1994; 57: 125-128.
8. Ferrante FM, Rosinia FA, Gordon C, Datta S. The role of continuous background infusions in patient-controlled epidural analgesia for labor and delivery. Anesth Analg 1994; 79: 80-84.
9. Paech M. Patient-controlled epidural analgesia in labour - is a continuous infusion of benefit? Anaesth Intens Care 1992; 20: 15-20.
10. Parker RK, White PF. Epidural patient-controlled analgesia: An alternative to intravenous patient-controlled analgesia for pain relief after cesarean delivery. Anesth Analg 1992; 75: 245-251.
11. Parker ILK, Sawaki Y, White PF. Epidural patient-controlled analgesia: Influence of bupivacaine and hydromorphone basal infusion on pain control after cesarean delivery. Anesth Analg 1992; 75: 740-746.
12. Cohen S; Amar D; Pantuck CB; Pantuck EJ; Goodman EJ; Widroff JS; Kanas RJ; Brady JA Adverse effects of epidural 0.03% bupivacaine during analgesia after cesarean section. Anesth Analg 1992; 75: 753-756
13. Yu P, Gambling DR A comparative study of patient-controlled epidural fentanyl and single dose epidural morphine for post-cesarean section analgesia. Can J Anaesth 1993; 40: 416-419.
14. Yarnell RW, Polis T, Reid GN et al Patient-controlled analgesia with epidural meperidine after elective cesarean section. Reg Anesth 1992; 17: 329-333.