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Anaesthesia for caesarean delivery: low-dose epidural bupivacaine plus fentanyl
International Journal of Obstetric Anesthesia (1998) 7,23-26 0 1998 Harcourt Brace & Co Ltd
ORIGINAL ARTICLE
Anaesthesia for caesarean delivery: low-dose epidural bupivacaine plus fentanyl A. Shapiro,B. Fredman, D. Olsfanger,R. Jedeikin Department of Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba, Israel, and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel SUMMARY To determine the acceptability of epidural bupivacaine-induced sixth thoracic (T6) sensory blockade and the analgesic efficacy of epidural fentanyl 50 pg, 24 parturients undergoing elective caesarean section were given a test dose of lidocaine 60 mg plus epinephrine followed by 10 ml of either 0.5 % bupivacaine (control group) or 0.5 % bupivacaine plus 50 ltg fentanyl (fentanyl group) in a randomized double-blind manner. Fifteen minutes later loss of pinprick sensation was determined. Additional local anaesthetic was titrated to achieve T6 sensory blockade. Intraoperative pain intensity was assessed using a 10 cm visual analogue scale (VAS); total dose of bupivacaine and need for i.v. rescue fentanyl were recorded. The incidence of intraoperative respiratory depression, nausea, vomiting and pruritus were documented. Mean (* SD) volume of bupivacaine was 14.1 f 3.05 ml versus 13 + 1.48 ml for the control and fentanyl groups respectively. The most severe intraoperative VAS for pain was significantly (P = 0.023) lower in the fentanyl group (0.4 f 0.08 cm) than in the control group (3.1 + 0.3 cm). Rescue fentanyl was administered in 40% and 0% of patients in the control and fentanyl groups respectively. The incidence of side-effects was unaffected by treatment group. Apgar scores were similar in the two groups. We conclude that following administration of 1615 ml 0.5% bupivacaine plus fentanyl 50 pg, T6 sensory blockade is associated with good intraoperative analgesia without obvious maternal or neonatal respiratory depression.
While opioid-local anaesthetic combinations enhance analgesia and decrease local anaestheticinduced adverse effects, fentanyl may be associated with dose-dependent maternal and neonatal respiratory depression.6J0-12 In our clinical experience, following epidural administration of bupivacaine with fentanyl50 l.tg, T6 sensory blockade is sufficient to provide good intraoperative analgesia and comfort without inducing unwanted maternal or neonatal side-effects. Therefore, to verify this observation, we designed a study to evaluate the acceptability of T6 sensory blockade as well as the analgesic effect of epidural fentanyl 50 l.tg during elective caesarean section.
INTRODUCTION Epidural anaesthesia is commonly administered for caesarean section. However, the volume, dosage and nature of the anaesthetic drugs administered and the optimal level of sensory blockade remain the subject of debate.’ Traditionally, in order to assure adequate analgesia and comfort, T4 sensory blockade is recommended before starting surgery.‘)2 However, despite the administration of 20-30 ml 0.5% bupivacaine and the consequent establishment of T4 sensory blockade, l&50% of parturients experience intraoperative pain and discomfort3s4 Furthermore, on exteriorizing the uterus, visceral pain has been reported in 50% of cases.5*6Finally, high neuraxial block may be associated with excessive vasodilatation and consequent haemodynamic instability, as well as ECG changes.7-9 Arie Shapiro MD, B. Fredman MB BCh, D. Olsfanger R. Jedeikin BSc MBChB FFA(S.A.), Department of
METHODS Twenty-four healthy (ASA physical status I) term parturients undergoing non-urgent caesarean section were enrolled into an institutional review boardapproved, prospective, randomized, double-blind study. Informed written consent was obtained in all cases.
MBChB,
Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba 4428 1, Israel, and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. Correspondence to: Arie Shapiro at Meir Hospital. 23
24 International Journal of Obstetric Anesthesia Patients with a history of bleeding disorder, renal or cardiac disease and those suffering from morbid obesity or sleep apnoea were excluded from the study. Preoperatively, all parturients were educated in the use of a visual analogue scale (VAS) and instructed to request i.v. rescue fentanyl for the treatment of intraoperative pain. In the pre-anaesthetic holding area, oral sodium citrate (30 ml) and intravenous lactated Ringer’s solution (10-l 5 ml/kg) were administered. Thereafter, monitoring equipment was applied and maternal electrocardiogram (ECG) and peripheral oxygen saturation (SpO,) were recorded continuously throughout the perioperative period. Arterial blood pressure (NIBP) was monitored non-invasively at 1 to 5 min intervals throughout the perioperative period. All patients received 35% supplemental oxygen via a face mask. With the patient in the right lateral position, an epidural catheter was inserted 3 cm cephalad through an 18 gauge Tuohy needle placed in the L3-4 interspace using an air loss of resistance technique. A test dose of epinephrine (15 l&ml) in 2 % lidocaine (3 ml) was given down the catheter. Thereafter, patients were placed supine with a 15-20” left lateral tilt. According to a computer generated randomization schedule, patients received an equal volume (10 ml) of either bupivacaine 45 mg (control) or bupivacaine 45 mg and fentanyl.50 yg (fentanyl group). The anaesthesiologist and research assistant were blinded to the medication used. Loss of pinprick sensation was determined 15 min after injection and at 5 min intervals throughout the perioperative period. If after two such intervals the block was found to stabilize below T6, additional epidural bupivacaine (5 mg per segment) was administered. Surgery proceeded when T6 sensory blockade was achieved. If sensory block above T6 was recorded the patient was excluded from further analysis. In all cases the surgical technique involved a lower transverse abdominal incision and uterine exteriorization. Using a 10 cm VAS (0 = no pain, 10 = worst pain imaginable), intraoperative pain intensity was assessed on incision, upon exteriorization of the uterus and if the patient requested i.v. fentanyl. The worst intraoperative VAS pain scores were submitted for statistical analysis. Intraoperative hypotension (decrease in systolic arterial pressure >20% of the preoperative value), respiratory depression (respiratory rate cl0 breaths per minute), nausea and pruritus were documented at 5 min intervals. The occurrence of vomiting was recorded. Induction time (time from epidural injection to skin incision), surgical time (time from skin incision to skin closure), total dose of bupivacaine and the need for i.v. fentanyl were recorded.
Immediately after delivery the respiration of all babies was assessed by a neonatologist and Apgar scores were recorded at 1 and 5 min. Data are expressed as mean (k SD) or range values. Parturient characteristics, induction time, surgical time and bupivacaine dose were analysed with the Student’s t-test. The highest intraoperative VAS scores for pain were compared with the Mann-Whitney U-test. A P value of 0.05 or less was considered to be significant.
RESULTS
Twenty-four patients were recruited to the study. Three patients in the control group and one in the fentanyl group were excluded from further statistical analysis because sensory blockade extended above the T6 dermatome. In the remaining 20 patients the level of sensory blockade was stable at T6 throughout the surgical procedure. The two treatment groups were similar for age, weight, height, parity, and incidence of previous caesarean sections (Table 1). Similarly, anaesthetic induction time, surgical time and bupivacaine dose were unaffected by treatment group (Table 2). The most severe intraoperative VAS score (mean f SD) was, however, significantly lower (P = 0.023) in the fentanyl group than in the control group (0.4 f 0.08 cm
Table
1. Demographic
data
Control (n = 10)
Fentanyl (n = 10)
34.1 f 3.5 162.2 f 6.1 80.3 + 8.9 0 7
31.6 f 4.1 161.8 + 5.7 80.5 f 2.7 0 4
Age W Height (cm) Weight (kg) Primiparous (n) Previous caesarean section (n) Data are mean f SD or number.
Table 2. Intraoperative
anaesthetic
data and complications
Control (n = 10) Bupivacaine (mg) Induction time (min) Surgical time (min) Most severe intraoperative VAS score* Rescue iv. fentanyl (n) Rescue i.v. fentanyl (pg) Hypotension (n) Ephedrine (mg) Nausea (n) Vomiting (n) Pruritus (n) Data are mean f SD or number. *P= 0.023.
70.5 2 41.8 + 39.2 + 3.1 +
15.25 11.35 3.33 3.03
4 250-100 5 5-20 7 3 0
Fentanyl (n = 10) 65 f 43.6 f 40 f 0.4 f
1.4 5.66 3.74 0.84
0 0 3 lo-30 4 1 0
Low-dose bupivacaine for caesarean delivery Table 3. The most severe intraoperative VAS pain scores VAS Scale (cm) Control(n) Fentanyl (n)*
0 3 8
1 1
2 2 2
3
4
5
6 2t
I 2t
8
9
10
Scale: IO-cm visual analogue (VAS) (0 = no pain, 10 = worst pain imaginable). * P = 0.023. TNumber of parturients requesting i.v. fentanyl.
versus 3.1 Ic_0.3 cm, respectively). No i.v. fentanyl was needed in the fentanyl group. By contrast, on uterine exteriorization, rescue fentanyl was administered in 40% of patients in the control group (Tables 2 and 3). Following i.v. fentanyl, VAS for pain was ~3 cm in all cases. Intraoperative hypotension, ephedrine administration, pruritus and emetic sequelae were not significantly affected by treatment group (Table 2). No maternal respiratory depression was observed. All babies had Apgar scores of 9 and 10, except for one in the control group who had Apgar scores of 7 and 9 at 1 and 5 min respectively.
DISCUSSION
This study suggests that a fentanyl-bupivacaine combination enhances intraoperative analgesia when compared to bupivacaine alone. While T6 sensory blockade was achieved in both study groups, patients in the fentanyl group recorded improved intraoperative VAS pain scores and required no rescue fentanyl. Furthermore, on exteriorizing the uterus, they experienced minimal pain and discomfort. By contrast, in the control group the most severe intraoperative VAS pain scores were significantly higher than those recorded in the fentanyl group and 40% of patients received rescue fentanyl. Previous studies have demonstrated the potential analgesic benefits of epidural fentanyl. However, epidural fentanyl administration is not without associated problems. While high blood levels of progesterone have been shown to increase the sensitivity of the respiratory centre to CO, and therefore protect against opioid-induced respiratory depression,13 following the epidural administration of fentanyl 100 ug, maternal and neonatal respiratory depression have been reported. ‘I, l2 However, the potentially life-threatening side-effect of delayed respiratory depression reported in non-pregnant surgical patients does not appear to have the same incidence or severity in parturients.14 Our study suggests that the addition of fentanyl50 pg to low-dose bupivacaine for caesarean section enhances analgesia without inducing maternal or neonatal respiratory depression.
25
It is of interest that in our study, in order to establish T6 sensory blockade, 13.5 ml 0.5% bupivacaine was administered compared to the 20-30 ml recommended for a T4 sensory blockade.‘5-18 We postulate that low-dose epidural bupivacaine was effective because adequate time was allowed for drug penetration and fixation, Furthermore, in the fentanyl group this reduced bupivacaine requirement may be explained by possible synergism between bupivacaine and fentanyl.19 This study can be criticized for the small size of the two groups. However, power analysis reveals that this study is associated with a 0.8 power (a = 0.05) to detect at least a 2.6 cm difference in patient-generated VAS for intraoperative pain. Therefore, it is unlikely that a type II statistical error occurred. A second criticism relates to the high incidence of intraoperative nausea. The aetiology of this complication is likely to be multi-factorial. While intraoperative nausea may be the result of visceral pain (i.e., stretching of the peritoneum), in our clinical experience local anaesthetic-induced neuraxial blockade with consequent hypotension is .a more common cause of this unwanted side-effect. Since patients in the fentanyl group recorded lower VAS pain scores and required no i.v. fentanyl, while nausea was associated with hypotension, visceral pain as a cause of nausea is unlikely. Therefore, in the fentanyl group, we suggest that sympathetic denervation resulted in vasodilatation with hypotension and consequent nausea. It is of interest to note that in the control group a marginal increase in the incidence of nausea was demonstrated. We postulate that, in addition to hypotension, visceral discomfort due to the lack of fentanyl-induced analgesia may have contributed to this increased incidence of nausea. However, due to the small sample size statistical significance was not reached. We conclude that following the administration of lo-15 ml 0.5% bupivacaine plus fentanyl 50 pg, T6 sensory blockade is sufficient to provide good intraoperative analgesia. Furthermore, in our patient population, the addition of fentanyl 50 ug enhances bupivacaine-induced analgesia without associated maternal or neonatal respiratory depression. REFERENCES 1. Capogna G, Celleno D. Improving epidural anaesthesia during caesarean section: causes of maternal discomfort or pain during surgery. International Journal of Obstetric Anesthesia 1994; 3: 149-152. 2. Craft J B, Roizen M F, Dao S D, et al. A comparison of T4 and T7 dermatomal levels of analgesia for caesarean section using the lumber epidural technique. Can Anaesth Sot J 1982; 29: 264269. 3. Crawford J S, Davies P, Lewis M. Some aspects of epidural block provided for elective caesarean section. Anaesthesia 1976; 41: 103991046.
26
International Journal of Obstetric Anesthesia
4. Shnider S M, Levinson G. Anesthesia for cesarean section. In: Shnider S M, Levinson G (Eds). Anesthesia for Obstetrics 3rd edn. Baltimore: William & Wilkins, 1993: 215. 5. Alahuhta S, Kangas-Saarela T, Hollmen A I, et al. Visceral pain during caesarean section under spinal and epidural anaesthesia with bupivacaine. Acta Anaesthesiol Stand 1990; 34: 95-98. 6. Gaffud M P, Bansal P, Lawton C, et al. Surgical analgesia for cesarean delivery with epidural bupivacaine and fentanyl. Anesthesiology 1986; 65: 331-334: 7. Palmer C M. Norris M C. Guidici M C. et al. Incidence of cardiographic changes during cesarean helivery under regional anesthesia. Anesth Analg 1990; 70: 3643. 8. Zakowski M I, Ramanathan S, Baratta J B, et al. Electrocardiographic changes during cesarean section: A cause of concern? Anesth Analg 1993; 76: 162-167. 9. Eisenach J C, Tuttle R, Stein A. Is ST segment depression of the electrocardiogram during cesarean section merely due to cardiac svmnathetic block? Anesth Anala 1994: 78: 2877292. 10. King M Jl Bbwden M I, Cooper G M. Epidural fentanyl and 0.5% buptvacaine for elective caesarean section. Anaesthesia 1990; 45: 285-288. 11. Noble D W, Morrison L M, Brockway M S, et al. Adrenaline, fentanyl or adrenaline and fentanyl as adjuncts to bupivacaine
12. 13. 14. 15. 16. 17. 18. 19.
for extradural anaesthesia in elective caesarean section. Br J Anaesth 1991; 66: 645-650. Brockway M S, Noble D W, Sharwood-Smith G H, et al. Profound respiratory depression after extradural fentanyl. Br J Anaesth 1990; 64: 243-245. Milne J A. The respiratory response to pregnancy. Postgrad Med J 1979; 55: 318-324. Fuller J G, McMorland G H, Douglas J M, et al. Epidural morphine for analgesia after Caesarean section: a report of 4886 patients. Can-Anaesth Sot J 1990; 37: 636640: Tunstall M E. Ostheimer G W. Obstetrics. In: Nunn J F. Utting J E, Brown Bumell R Jr (Eds). General Anaesthesia 5th edn. London: Butterworth & Co Ltd, 1989: 993. Shnider S M, Levinson G. Anesthesia for Obstetrics. In: Miller R D (Ed). Anesthesia 3rd edn. New York: Churchill Livingstone, 1990: 1855. Ostheimer G W, Leavitt K A. Lumber epidural anesthesia. In: Ostheimer G W (Ed). Manual of Obstetric Anesthesia 2nd edn. New York: Churchill Livingstone Inc, 1992: 174. Crawford J S. Experiences with lumbar extradural analgesia for caesarean section. Br J Anaesth 1980; 52: 821-825. Solomon R E, Gebhart G F. Synergistic antinociceptive interactions among drugs administered to the spinal cord. Anesth Analg 1994; 78: 1164-l 172.
ORIGINAL ARTICLE
Anaesthesia for caesarean delivery: low-dose epidural bupivacaine plus fentanyl A. Shapiro,B. Fredman, D. Olsfanger,R. Jedeikin Department of Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba, Israel, and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel SUMMARY To determine the acceptability of epidural bupivacaine-induced sixth thoracic (T6) sensory blockade and the analgesic efficacy of epidural fentanyl 50 pg, 24 parturients undergoing elective caesarean section were given a test dose of lidocaine 60 mg plus epinephrine followed by 10 ml of either 0.5 % bupivacaine (control group) or 0.5 % bupivacaine plus 50 ltg fentanyl (fentanyl group) in a randomized double-blind manner. Fifteen minutes later loss of pinprick sensation was determined. Additional local anaesthetic was titrated to achieve T6 sensory blockade. Intraoperative pain intensity was assessed using a 10 cm visual analogue scale (VAS); total dose of bupivacaine and need for i.v. rescue fentanyl were recorded. The incidence of intraoperative respiratory depression, nausea, vomiting and pruritus were documented. Mean (* SD) volume of bupivacaine was 14.1 f 3.05 ml versus 13 + 1.48 ml for the control and fentanyl groups respectively. The most severe intraoperative VAS for pain was significantly (P = 0.023) lower in the fentanyl group (0.4 f 0.08 cm) than in the control group (3.1 + 0.3 cm). Rescue fentanyl was administered in 40% and 0% of patients in the control and fentanyl groups respectively. The incidence of side-effects was unaffected by treatment group. Apgar scores were similar in the two groups. We conclude that following administration of 1615 ml 0.5% bupivacaine plus fentanyl 50 pg, T6 sensory blockade is associated with good intraoperative analgesia without obvious maternal or neonatal respiratory depression.
While opioid-local anaesthetic combinations enhance analgesia and decrease local anaestheticinduced adverse effects, fentanyl may be associated with dose-dependent maternal and neonatal respiratory depression.6J0-12 In our clinical experience, following epidural administration of bupivacaine with fentanyl50 l.tg, T6 sensory blockade is sufficient to provide good intraoperative analgesia and comfort without inducing unwanted maternal or neonatal side-effects. Therefore, to verify this observation, we designed a study to evaluate the acceptability of T6 sensory blockade as well as the analgesic effect of epidural fentanyl 50 l.tg during elective caesarean section.
INTRODUCTION Epidural anaesthesia is commonly administered for caesarean section. However, the volume, dosage and nature of the anaesthetic drugs administered and the optimal level of sensory blockade remain the subject of debate.’ Traditionally, in order to assure adequate analgesia and comfort, T4 sensory blockade is recommended before starting surgery.‘)2 However, despite the administration of 20-30 ml 0.5% bupivacaine and the consequent establishment of T4 sensory blockade, l&50% of parturients experience intraoperative pain and discomfort3s4 Furthermore, on exteriorizing the uterus, visceral pain has been reported in 50% of cases.5*6Finally, high neuraxial block may be associated with excessive vasodilatation and consequent haemodynamic instability, as well as ECG changes.7-9 Arie Shapiro MD, B. Fredman MB BCh, D. Olsfanger R. Jedeikin BSc MBChB FFA(S.A.), Department of
METHODS Twenty-four healthy (ASA physical status I) term parturients undergoing non-urgent caesarean section were enrolled into an institutional review boardapproved, prospective, randomized, double-blind study. Informed written consent was obtained in all cases.
MBChB,
Anesthesiology and Intensive Care, Meir Hospital, Kfar Saba 4428 1, Israel, and the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. Correspondence to: Arie Shapiro at Meir Hospital. 23
24 International Journal of Obstetric Anesthesia Patients with a history of bleeding disorder, renal or cardiac disease and those suffering from morbid obesity or sleep apnoea were excluded from the study. Preoperatively, all parturients were educated in the use of a visual analogue scale (VAS) and instructed to request i.v. rescue fentanyl for the treatment of intraoperative pain. In the pre-anaesthetic holding area, oral sodium citrate (30 ml) and intravenous lactated Ringer’s solution (10-l 5 ml/kg) were administered. Thereafter, monitoring equipment was applied and maternal electrocardiogram (ECG) and peripheral oxygen saturation (SpO,) were recorded continuously throughout the perioperative period. Arterial blood pressure (NIBP) was monitored non-invasively at 1 to 5 min intervals throughout the perioperative period. All patients received 35% supplemental oxygen via a face mask. With the patient in the right lateral position, an epidural catheter was inserted 3 cm cephalad through an 18 gauge Tuohy needle placed in the L3-4 interspace using an air loss of resistance technique. A test dose of epinephrine (15 l&ml) in 2 % lidocaine (3 ml) was given down the catheter. Thereafter, patients were placed supine with a 15-20” left lateral tilt. According to a computer generated randomization schedule, patients received an equal volume (10 ml) of either bupivacaine 45 mg (control) or bupivacaine 45 mg and fentanyl.50 yg (fentanyl group). The anaesthesiologist and research assistant were blinded to the medication used. Loss of pinprick sensation was determined 15 min after injection and at 5 min intervals throughout the perioperative period. If after two such intervals the block was found to stabilize below T6, additional epidural bupivacaine (5 mg per segment) was administered. Surgery proceeded when T6 sensory blockade was achieved. If sensory block above T6 was recorded the patient was excluded from further analysis. In all cases the surgical technique involved a lower transverse abdominal incision and uterine exteriorization. Using a 10 cm VAS (0 = no pain, 10 = worst pain imaginable), intraoperative pain intensity was assessed on incision, upon exteriorization of the uterus and if the patient requested i.v. fentanyl. The worst intraoperative VAS pain scores were submitted for statistical analysis. Intraoperative hypotension (decrease in systolic arterial pressure >20% of the preoperative value), respiratory depression (respiratory rate cl0 breaths per minute), nausea and pruritus were documented at 5 min intervals. The occurrence of vomiting was recorded. Induction time (time from epidural injection to skin incision), surgical time (time from skin incision to skin closure), total dose of bupivacaine and the need for i.v. fentanyl were recorded.
Immediately after delivery the respiration of all babies was assessed by a neonatologist and Apgar scores were recorded at 1 and 5 min. Data are expressed as mean (k SD) or range values. Parturient characteristics, induction time, surgical time and bupivacaine dose were analysed with the Student’s t-test. The highest intraoperative VAS scores for pain were compared with the Mann-Whitney U-test. A P value of 0.05 or less was considered to be significant.
RESULTS
Twenty-four patients were recruited to the study. Three patients in the control group and one in the fentanyl group were excluded from further statistical analysis because sensory blockade extended above the T6 dermatome. In the remaining 20 patients the level of sensory blockade was stable at T6 throughout the surgical procedure. The two treatment groups were similar for age, weight, height, parity, and incidence of previous caesarean sections (Table 1). Similarly, anaesthetic induction time, surgical time and bupivacaine dose were unaffected by treatment group (Table 2). The most severe intraoperative VAS score (mean f SD) was, however, significantly lower (P = 0.023) in the fentanyl group than in the control group (0.4 f 0.08 cm
Table
1. Demographic
data
Control (n = 10)
Fentanyl (n = 10)
34.1 f 3.5 162.2 f 6.1 80.3 + 8.9 0 7
31.6 f 4.1 161.8 + 5.7 80.5 f 2.7 0 4
Age W Height (cm) Weight (kg) Primiparous (n) Previous caesarean section (n) Data are mean f SD or number.
Table 2. Intraoperative
anaesthetic
data and complications
Control (n = 10) Bupivacaine (mg) Induction time (min) Surgical time (min) Most severe intraoperative VAS score* Rescue iv. fentanyl (n) Rescue i.v. fentanyl (pg) Hypotension (n) Ephedrine (mg) Nausea (n) Vomiting (n) Pruritus (n) Data are mean f SD or number. *P= 0.023.
70.5 2 41.8 + 39.2 + 3.1 +
15.25 11.35 3.33 3.03
4 250-100 5 5-20 7 3 0
Fentanyl (n = 10) 65 f 43.6 f 40 f 0.4 f
1.4 5.66 3.74 0.84
0 0 3 lo-30 4 1 0
Low-dose bupivacaine for caesarean delivery Table 3. The most severe intraoperative VAS pain scores VAS Scale (cm) Control(n) Fentanyl (n)*
0 3 8
1 1
2 2 2
3
4
5
6 2t
I 2t
8
9
10
Scale: IO-cm visual analogue (VAS) (0 = no pain, 10 = worst pain imaginable). * P = 0.023. TNumber of parturients requesting i.v. fentanyl.
versus 3.1 Ic_0.3 cm, respectively). No i.v. fentanyl was needed in the fentanyl group. By contrast, on uterine exteriorization, rescue fentanyl was administered in 40% of patients in the control group (Tables 2 and 3). Following i.v. fentanyl, VAS for pain was ~3 cm in all cases. Intraoperative hypotension, ephedrine administration, pruritus and emetic sequelae were not significantly affected by treatment group (Table 2). No maternal respiratory depression was observed. All babies had Apgar scores of 9 and 10, except for one in the control group who had Apgar scores of 7 and 9 at 1 and 5 min respectively.
DISCUSSION
This study suggests that a fentanyl-bupivacaine combination enhances intraoperative analgesia when compared to bupivacaine alone. While T6 sensory blockade was achieved in both study groups, patients in the fentanyl group recorded improved intraoperative VAS pain scores and required no rescue fentanyl. Furthermore, on exteriorizing the uterus, they experienced minimal pain and discomfort. By contrast, in the control group the most severe intraoperative VAS pain scores were significantly higher than those recorded in the fentanyl group and 40% of patients received rescue fentanyl. Previous studies have demonstrated the potential analgesic benefits of epidural fentanyl. However, epidural fentanyl administration is not without associated problems. While high blood levels of progesterone have been shown to increase the sensitivity of the respiratory centre to CO, and therefore protect against opioid-induced respiratory depression,13 following the epidural administration of fentanyl 100 ug, maternal and neonatal respiratory depression have been reported. ‘I, l2 However, the potentially life-threatening side-effect of delayed respiratory depression reported in non-pregnant surgical patients does not appear to have the same incidence or severity in parturients.14 Our study suggests that the addition of fentanyl50 pg to low-dose bupivacaine for caesarean section enhances analgesia without inducing maternal or neonatal respiratory depression.
25
It is of interest that in our study, in order to establish T6 sensory blockade, 13.5 ml 0.5% bupivacaine was administered compared to the 20-30 ml recommended for a T4 sensory blockade.‘5-18 We postulate that low-dose epidural bupivacaine was effective because adequate time was allowed for drug penetration and fixation, Furthermore, in the fentanyl group this reduced bupivacaine requirement may be explained by possible synergism between bupivacaine and fentanyl.19 This study can be criticized for the small size of the two groups. However, power analysis reveals that this study is associated with a 0.8 power (a = 0.05) to detect at least a 2.6 cm difference in patient-generated VAS for intraoperative pain. Therefore, it is unlikely that a type II statistical error occurred. A second criticism relates to the high incidence of intraoperative nausea. The aetiology of this complication is likely to be multi-factorial. While intraoperative nausea may be the result of visceral pain (i.e., stretching of the peritoneum), in our clinical experience local anaesthetic-induced neuraxial blockade with consequent hypotension is .a more common cause of this unwanted side-effect. Since patients in the fentanyl group recorded lower VAS pain scores and required no i.v. fentanyl, while nausea was associated with hypotension, visceral pain as a cause of nausea is unlikely. Therefore, in the fentanyl group, we suggest that sympathetic denervation resulted in vasodilatation with hypotension and consequent nausea. It is of interest to note that in the control group a marginal increase in the incidence of nausea was demonstrated. We postulate that, in addition to hypotension, visceral discomfort due to the lack of fentanyl-induced analgesia may have contributed to this increased incidence of nausea. However, due to the small sample size statistical significance was not reached. We conclude that following the administration of lo-15 ml 0.5% bupivacaine plus fentanyl 50 pg, T6 sensory blockade is sufficient to provide good intraoperative analgesia. Furthermore, in our patient population, the addition of fentanyl 50 ug enhances bupivacaine-induced analgesia without associated maternal or neonatal respiratory depression. REFERENCES 1. Capogna G, Celleno D. Improving epidural anaesthesia during caesarean section: causes of maternal discomfort or pain during surgery. International Journal of Obstetric Anesthesia 1994; 3: 149-152. 2. Craft J B, Roizen M F, Dao S D, et al. A comparison of T4 and T7 dermatomal levels of analgesia for caesarean section using the lumber epidural technique. Can Anaesth Sot J 1982; 29: 264269. 3. Crawford J S, Davies P, Lewis M. Some aspects of epidural block provided for elective caesarean section. Anaesthesia 1976; 41: 103991046.
26
International Journal of Obstetric Anesthesia
4. Shnider S M, Levinson G. Anesthesia for cesarean section. In: Shnider S M, Levinson G (Eds). Anesthesia for Obstetrics 3rd edn. Baltimore: William & Wilkins, 1993: 215. 5. Alahuhta S, Kangas-Saarela T, Hollmen A I, et al. Visceral pain during caesarean section under spinal and epidural anaesthesia with bupivacaine. Acta Anaesthesiol Stand 1990; 34: 95-98. 6. Gaffud M P, Bansal P, Lawton C, et al. Surgical analgesia for cesarean delivery with epidural bupivacaine and fentanyl. Anesthesiology 1986; 65: 331-334: 7. Palmer C M. Norris M C. Guidici M C. et al. Incidence of cardiographic changes during cesarean helivery under regional anesthesia. Anesth Analg 1990; 70: 3643. 8. Zakowski M I, Ramanathan S, Baratta J B, et al. Electrocardiographic changes during cesarean section: A cause of concern? Anesth Analg 1993; 76: 162-167. 9. Eisenach J C, Tuttle R, Stein A. Is ST segment depression of the electrocardiogram during cesarean section merely due to cardiac svmnathetic block? Anesth Anala 1994: 78: 2877292. 10. King M Jl Bbwden M I, Cooper G M. Epidural fentanyl and 0.5% buptvacaine for elective caesarean section. Anaesthesia 1990; 45: 285-288. 11. Noble D W, Morrison L M, Brockway M S, et al. Adrenaline, fentanyl or adrenaline and fentanyl as adjuncts to bupivacaine
12. 13. 14. 15. 16. 17. 18. 19.
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