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© 1999 International Anesthesia Research Society
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Abstract |
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We randomized 76 parturients to a double-blinded trial to receive spinal anesthesia with either hyperbaric or plain bupivacaine 9 mg with fentanyl 20 µg for elective cesarean delivery. A combined spinal-epidural technique was used. The onset and duration of anesthesia (absence of pinprick sensation), analgesia (absence of sharp sensation to pinprick), and absence of cold sensation and motor block were measured until recovery from the motor block. No major differences were seen in onset or duration of anesthesia between the groups. Motor block, however, vanished faster when hyperbaric bupivacaine was used (P < 0.05). The level of anesthesia (no pinprick sensation) required for painless operation was at dermatome T5. At this time, the absence of cold sensation ranged from dermatome T1 to C3. The median time for the anesthesia to reach dermatome T5 was 10 min. Cervical spread of pinprick anesthesia was noted in six patients, and five needed supplementary analgesics during surgery (not significant between the groups). Maternal satisfaction was good. Nine milligrams of either plain or hyperbaric bupivacaine with fentanyl intrathecally provided similar onset, depth, and duration of sensory anesthesia for cesarean delivery with good maternal satisfaction. Motor block developed and diminished faster with the hyperbaric solution.
Implications: Nine milligrams of either plain or hyperbaric bupivacaine with fentanyl intrathecally provided similar onset, depth, and duration of sensory anesthesia for cesarean delivery with good maternal satisfaction. Motor block developed and diminished faster with the hyperbaric solution.
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Introduction |
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After introduction of atraumatic pencil point needles with a small incidence of postdural puncture headache, spinal anesthesia has become a popular technique for cesarean delivery. Hyperbaric bupivacaine in 8% glucose is often used. However, it has been suggested that plain bupivacaine offers some advantages over the hyperbaric form, such as better stability of the anesthesia level during positional changes (1) which, however, can be used to control the height of the block when hyperbaric local anesthetics are used.
Controversial results have been presented concerning the predictability of the level of the block, probably a result of the wide differences in the dosage of the drug and in the methods used to measure the level of the block. Total spinal anesthesia has been reported with dosages of 12 mg or more (2), although the problem seems to be rare in practice. However, spinal anesthesia for cesarean delivery has been performed with very small doses of bupivacaine, e.g., 6.6 mg (3). Textbooks of anesthesia still recommend large doses of bupivacaine (4,5), even though clinical experience with opioid local anesthetic combinations and the introduction of the combined spinal epidural technique favors smaller doses.
The aim of the present study was to compare hyperbaric and plain bupivacaine in spinal anesthesia using a small dosage (9 mg) and a strict protocol to measure absence of cold sensation, analgesia, and anesthesia and motor block levels throughout the intraoperative period in elective cesarean delivery. Fentanyl 20 µg was added to bupivacaine because it reduces intraoperative nausea and vomiting and prolongs anesthesia (6,7). A combined spinal-epidural technique was applied to avoid general anesthesia. Transient neurological symptoms (TNS) were also recorded.
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Methods |
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We studied 76 healthy, full-term (gestational age 37 to 42 wk) singleton parturients undergoing elective cesarean delivery. The study was approved by our institutional ethics committee, and the informed, written consent of all patients was obtained.
After overnight fast, the patients received 30 mL of 0.3 M sodium citrate orally 30 min before anesthesia. Each patient received 1 L of acetated Ringer’s solution before initiation of spinal anesthesia. Immediately after inducing spinal anesthesia, an additional 500 mL of Ringer’s acetate solution with 15 mg of ephedrine was infused.
According to computer generated random numbers, the patients received either 1.8 mL plain bupivacaine 0.5% (Group P) or 1.8 mL bupivacaine 0.5% in 8% glucose (Group H), both with fentanyl 20 µg (0.4 mL). The final volume of the study drug was 2.2 mL. Neither the anesthesiologist nor the patient was aware of the solution. We used a combined spinal-epidural needle through needle technique with G16 Tuohy epidural needle and Whitacre G26 spinal needle. The epidural needle was inserted in the L2-3 interspace with the opening cranially. Spinal anesthesia was induced with either of the solutions with needle bevel oriented cranially. Thereafter, an epidural catheter was inserted. Initially, the patient lay on her right side with a pillow under her head and was then turned to a supine position. The operation table was tilted 20° to the left, and a urinary catheter was inserted. If, at 16 min, the cold sensation had not decreased at T5 dermatome level, the epidural catheter was tested, and epidural anesthesia was induced as necessary. Paresthesia and bleeding during intrathecal needle insertion and epidural catheterization were recorded. Oxygen 4 L/min was administered via a facial mask. IV boluses of 5–10 mg ephedrine and additional IV fluids were administered to treat hypotension, which was defined as systolic blood pressure below 95 mm Hg or a decrease in systolic pressure of >20% from the baseline value.
Maternal electrocardiogram and oxygen saturation were monitored, and noninvasive blood pressure was measured from the right arm every 2 min until the birth of the child and thereafter every 5 min until the patient was moved to the recovery unit. Bradycardia was defined as a pulse rate 
40 bpm. Absence of cold sensation was tested with an alcohol swab as a change from cold sensation compared with that of the cheek. The level of pinprick analgesia was tested with the short beveled end of a dental needle as a change from a dull sensation to a sharp sensation (using cheek sensation as reference). The level of anesthesia was tested with the dental needle as a loss of sensation. The degree of motor block was assessed using modified Bromage scale (0 = able to lift legs; 1 = ability to flex knees but not the hip; 2 = unable to flex knees, but no problems with ankle movement; and 3 = no movement possible in any lower extremity joint). These assessments were made bilaterally at 4, 7, 10, 13, 16, 19, 22, 25, 30, and 45 min and 1, 1.5, 2, 2.5, and 3 h or until full recovery of motor function. The lower level of the bilateral measurement was used for comparison. Perioperative pain was estimated with a Visual Analog Score (VAS) from 0 (no pain) to 10 (worst possible pain), and the grading was used to assess nausea (0 = none, 1 = nausea, 2 = retching, 3 = vomiting) and pruritus (0 = none, 1 = some pruritus, 2 = disturbing pruritus). IV fentanyl was used during surgery as a rescue analgesic.
The surgical technique was uniform for all patients and included exteriorization of the uterus. At delivery, blood samples were collected from the umbilical vein for blood gas analysis. Five international units of oxytocin was administered IV after delivery. Apgar score was assessed at the ages of 1 and 5 min.
When the mother was able to lift her legs and bend her knees (Bromage grade 0), the epidural catheter was tested with 3 mL of lidocaine 2% with epinephrine 5 µg/mL. After 4 min, 4 mg of morphine was injected epidurally. Ketoprofen 100 mg or paracetamol 1 g was used as a rescue analgesic.
The patients were visited during the first and third postoperative days. During the first visit, postoperative pain, when the patient was lying in bed and coughing, was assessed using the VAS as described above. The side effects of epidural morphine during the first 24 h were monitored by the ward nurse and treated if necessary. During the third postoperative day, patient satisfaction with the anesthesia and postoperative analgesia were also estimated with the VAS (0 = least satisfied, 10 = totally satisfied), and TNS symptoms were evaluated. Back pain before pregnancy, during pregnancy, and after the operation, pain at the place of insertion of anesthesia, other localization and radiation, onset of new symptoms, duration, and neurological dysfunction were asked and examined if present.
For statistical analysis the Mann-Whitney U-test and 
2 test (differences among proportions) for quantitative and categorical data, respectively, were used. The demographic data are expressed as means ± SD and the development of the block as medians and 10% and 90% percentiles. Regression analysis was applied to test correlations. P < 0.05 was considered significant.
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Results |
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The groups were comparable with each other (Table 1). Six patients were excluded from the study because of the inability of the observer to follow the protocol (one patient), premature birth (one patient), no backflow of cerebrospinal fluid after spinal anesthesia and conversion of anesthesia to epidural (four patients). One patient, in the plain bupivacaine group, required epidural supplementation, although backflow of cerebrospinal fluid was seen after spinal anesthesia. She was included in the comparison up to the moment of supplementation. The incidence of failure of spinal block was 5%.
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The development and duration of anesthesia and absence of cold sensation are shown in Figure 1. No differences in the speed of onset, duration and the spread of anesthesia, analgesia, and absence of cold sensation were seen between plain and hyperbaric bupivacaine. We observed a wide range of results. Motor block, however, developed and vanished significantly faster (P < 0.05) among the patients anesthetized with hyperbaric bupivacaine (Tables 2 and 3).
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In both groups, the median onset time of anesthesia at dermatome T5 was 10 min with 10 and 90 percentiles for plain bupivacaine, 7 and 22 min, and for hyperbaric bupivacaine, 10 and 30 min. Anesthesia remained at that level for approximately 1 h from the induction of spinal anesthesia. Cervical spread of anesthesia (loss of sensation to pinprick needle) occurred in six patients. Five of these patients had received hyperbaric bupivacaine, and one received plain bupivacaine (no statistical difference). The highest level of anesthesia occurred at the third cervical dermatome. None of these patients had bradycardia or phonation problems as a sign of high block. The highest level of absence of cold sensation (C4, median) was reached at 19 min in both groups. However, this interval also showed considerable variation in both groups ranging from 7 to 30 min (Table 3).
During the early fast spread of anesthesia and the concomitant hypotension, several patients were nauseated. After the skin incision, three patients in Group H and four patients in Group P had nausea or vomiting. In four of these seven patients, nausea was clearly related to the continuing spread of anesthesia and hypotension, the anesthesia level was above T4. In two patients, nausea and unpleasant feelings occurred at the end of exteriorization of the uterus and manipulation of the peritoneum. At that time, the level of anesthesia was below T5.
Additional ephedrine was given to 55% and 61% of the patients receiving plain and hyperbaric bupivacaine, respectively. In the hyperbaric group, one patient complained of disturbing itching during surgery, and three complained during the visit in the recovery unit.
Five patients felt pain during short periods of the operation and were treated with IV fentanyl. Four of these five patients had pinprick anesthesia level at T6 or lower during pain sensation (Table 3) that was associated either with the birth or manipulation of the uterus back into the abdominal cavity or peritoneal closure. None of the patients required general anesthesia.
Paresthesia during insertion of the spinal needle was noted in 27% of the patients. There were no cases of TNS syndrome. No more back pain was recorded after surgery than before pregnancy, and there were no differences between the groups in the incidence of back pain before, during, or after surgery. No postoperative neurologic sequelae were seen on the third postoperative day (Table 4). There were no dural taps with the epidural needle or complaints of postoperative headache.
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No correlations were found between body mass index, height, or weight and the maximal spread of anesthesia among all patients.
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Discussion |
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There were no differences between plain and hyperbaric bupivacaine in the three qualities of sensory block we tested (Fig. 1). Although motor block developed statistically faster with hyperbaric bupivacaine, this is of minor clinical importance. Motor block also vanished faster when hyperbaric bupivacaine was used and was brief, less than one hour, in 17% of the patients (Table 2). A similar difference has been reported by Russell et al. (8) but not by Richardson et al. 1998 (9). The clinical significance of the short duration of motor block can be questioned. In short operations, fast recovery is an advantage, but may complicate the surgery of less experienced obstetricians or complicated cesarean deliveries if there is no possibility of epidural extension.
In nonobstetric studies, higher cephalad spread of the block has been induced with hyperbaric solutions when compared with plain solutions (10–12). Our study supports previous findings in obstetric patients, namely, that baricity of bupivacaine does not influence the rate of onset or duration of the sensory block (8,9). However, this is not in agreement with a recent study suggesting that the block level is more predictable when hyperbaric bupivacaine is used (3). Unfortunately, in that study, the height of the block was tested using solely ether swabs up to the moment of skin preparation, and the sensation of pain during surgery was not reported. Our study showed that the block level could still spread cephalad up to 30 min from the injection of the local anesthetic. In addition, the level of absence of cold sensation or analgesia level does not necessarily predict the level of anesthesia and can thus be misleading when used as the only measure of the level of the block (13).
For cesarean delivery, an anesthesia level of dermatome T4 has been generally proposed to achieve a pain free operation (4,14). In our study the level of anesthesia in four of the five patients experiencing pain during surgery was at that moment below dermatome T5. Pain was felt at the time of birth (one patient, anesthesia level at T7) and during manipulation of the uterus back into the abdominal cavity or peritoneal closure (three patients, anesthesia levels at T6 or T7). The respective analgesia and absence of cold sensation levels at that moment were considerably higher, at dermatomes ranging from T7 to T4, and from T1 to C3, respectively. Our finding that the adequate level of pinprick anesthesia lies up to and including T5 is in agreement with the study of Russell (13).
There is disagreement about whether nausea and vomiting during surgery or visceral pain is linked to the level of anesthesia (14,15). Seven of our patients had nausea and/or vomiting during the operative period. In four of these patients, nausea was clearly associated with the hypotensive period during the rapid spread of the spinal anesthesia before surgery. Three patients had nausea/vomiting during surgery. Two of these patients had nausea and/or unpleasant feelings during delivery and/or manipulation of the uterus back into the abdominal cavity. The anesthesia level of these patients lay also at dermatomes T6 or T7 at that time. Although other symptoms, such as heaviness, pressure, or unpleasant feelings, can be considered visceral in origin, they were not observed, with the exception of one patient. This patient also felt very mild pain (VAS score: 1 and 2) and had nausea during surgery despite the anesthesia level of T1. It may be difficult to distinguish between anxiety-related feelings and visceral pain in the patients who do not receive any premedication (15). According to this study, visceral pain/nausea and vomiting can largely be avoided by reaching an anesthesia level of dermatome T5.
An unexpectedly large proportion of the patients had hypotension (58%), although a small amount of the local anesthetic, prophylactic ephedrine, preloading with crystalloids, and 20 degrees of left lateral tilt of the operating table were used. The infusion of ephedrine we used was chosen to be more dilute than that suggested by Kang et al. (16) in order to make it possible to see differences in its requirements between the groups. Four newborns had umbilical pH under 7.20. According to some studies, adding colloids to the preloading protocol may counteract hypotension (17,18). Although intrathecal fentanyl has been considered rather inactive hemodynamically in cesarean deliveries (7), it is possible that the large dose of fentanyl, 20 µg, contributed to the high incidence of hypotension as reported in a study in male patients undergoing lower extremity or genitourinary surgery under spinal anesthesia (19).
The popularity of spinal anesthesia for cesarean delivery is increasing; the appropriate dosage of bupivacaine thus seems to be under reevaluation (1). Often, doses up to 15 mg of hyperbaric bupivacaine are recommended (4,5). Total spinal anesthesia has been reported with doses larger than 12 mg of hyperbaric bupivacaine in patients undergoing cesarean delivery (1,2), although the problem seems to be rare. Because of the pooling of the anesthetic in the thoracic spinal curvature, the block levels of different doses have been reported to lie at dermatome T2-3, despite the dosage of the local anesthetic (20,21). Although the amount of bupivacaine we used was only 9 mg, the median level of anesthesia lay at level T2 with both preparations. Cervical spread of pinprick anesthesia was observed in as many as six patients but bradycardia, breathing difficulties, or decrease of oxygen saturation as a sign of truly high block were not seen. However, only five patients experienced a short period of pain during surgery, and only one patient needed epidural extension of the block as a consequence of too low cephalad spread of anesthesia. Thus, it seems that no more than 9 mg of bupivacaine is necessary for spinal anesthesia in cesarean delivery when combined spinal-epidural anesthesia technique is used. In longer lasting operations, spinal anesthesia can rapidly be extended by injection of lidocaine 2% with 2.5 µg/mL epinephrine epidurally.
In conclusion, 9 mg of bupivacaine with fentanyl, regardless of the baricity, induced satisfactory anesthesia for cesarean delivery lasting less than an hour without any difference in the speed of onset or maximal level of sensory block between plain and hyperbaric bupivacaine. When compared with plain bupivacaine, however, motor block vanished faster with hyperbaric bupivacaine. The pain-free anesthesia level was at dermatome T5. It was reached within 10 minutes and lasted for 1 hour, making it preferable to use the combined spinal-epidural technique. The wide interindividual variability in the spread of anesthesia requires close and systematic follow-up of the block and psychological preparation of the patient to an anesthesia level sometimes reaching cervical dermatomes.
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References |
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- Finucane BT. Spinal anesthesia for cesarean delivery the dosage dilemma. Anesth 1995;20:87–9.
- de Simone CA, Leighton BL, Norris MC. Spinal anesthesia for cesarean delivery: a comparison of two doses of hyperbaric bupivacaine. Reg Anesth 1995;20:90–4.[Web of Science][Medline]
- Vercauteren MP, Coppejans HC, Hoffmann VL, et al. Small-dose hyperbaric versus plain bupivacaine during spinal anesthesia for cesarean section. Anesth Analg 1998;86:989–93.[Abstract]
- Reisner LS, Lin D. Anesthesia for cesarean section. In: Chestnut DH, ed. Obstetric anesthesia: principles and practice. St. Louis:Mosby, 1994:467–9.
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- Dahlgren G, Hultstrand C, Jakobsson J, et al. Intrathecal sufentanil, fentanyl, or placebo added to bupivacaine for cesarean section. Anesth Analg 1997;85:1288–93.[Abstract]
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Belzarena SD. Clinical effects of intrathecally administered fentanyl in patients undergoing cesarean section. Anesth Analg 1992;74:653–7.
[Abstract/Free Full Text] - Russell IF, Holmqvist EL. Subarachnoid analgesia for caesarean section: a double-blind comparison of plain and hyperbaric 0.5% bupivacaine. Anaesth 1987;59:347–453.
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Richardson MG, Collins HV, Wissler RN. Intrathecal hypobaric versus hyperbaric bupivacaine with morphine for cesarean section. Anesth Analg 1998;87:336–40.
[Abstract/Free Full Text] - Chambers WA, Edstrom HH, Scott DB. Effect of baricity on spinal anaesthesia with bupivacaine. Anaesth 1981;53:279–82.
- Liu SS. Optimizing spinal anesthesia for ambulatory surgery. Reg Anesth 1997;22:500–10.[Web of Science][Medline]
- Tetzlaff JE, O’Hara J, Bell G, et al. Influence of baricity on the outcome of spinal anesthesia with bupivacaine for lumbar spine surgery. Reg Anesth 1995;20:533–7.[Web of Science][Medline]
- Russell IF. Levels of anaesthesia and intraoperative pain at caesarean section under regional block. Int J Obst Anesth 1995;4:71–7.
- Lussos SA, Datta S. Anesthesia for cesarean delivery. Part 1. General considerations and spinal anesthesia. Int J Obst Anesth 1992;1:79–91.
- Alahuhta S, Kangas-Saarela T, Hollmén AI, Edström HH. Visceral pain during caesarean section under spinal and epidural anaesthesia with bupivacaine. Acta Anaesthesiol Scand 1990;34:95–8.[Web of Science][Medline]
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Kang YG, Abouleish E, Caritis S. Prophylactic intravenous ephedrine infusion during spinal anesthesia for cesarean section. Anesth Analg 1982;61:839–42.
[Abstract/Free Full Text] - Riley ET, Cohen SE, Rubenstein AJ, Flanagan B. Prevention of hypotension after spinal anesthesia for cesarean section: six percent hetastarch versus lactated Ringer’s solution. Anesth Analg 1995;81:838–42.[Abstract]
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Vercauteren MP, Hoffmann V, Coppejans HC, et al. Hydroxyethystarch compared with modified gelatin as volume preload before spinal anaesthesia for Caesarean section. Br J Anaesth 1996;76:731–3.
[Abstract/Free Full Text] - Singh H, Yang J, Thornton K, Giesecke AH. Intrathecal fentanyl prolongs sensory bupivacaine spinal block. J Anaesth 1995;42:987–91.
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Abouleish EI. Postpartum tubal ligation requires more bupivacaine for spinal anesthesia than does cesarean section. Anesth Analg 1986;65:897–900.
[Abstract/Free Full Text] - Norris MC. Height, weight, and the spread of subarachnoid hyperbaric bupivacaine in the term parturient. Anesth Analg 1988;67:355–8.
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