The spread of either a plain or hyperbaric substance during the first minutes after their administration may theoretically be of crucial importance. During cesarean delivery the position of the patient may be particularly important because a different spread of the block may affect the incidence and degree of hypotension, whereas differences in the degree of motor block may influence patient satisfaction and discharge times from the postanesthetic care unit.
However, there are few studies evaluating the influence of patient posture during the performance of neuraxial anesthetic techniques. Although all studies agree that right or left lateral decubitus positions can be used equally well (1–3), the results with respect to the success rate and hemodynamic effects between the lateral and sitting position during spinal anesthetic techniques are more conflicting (4,5).
We previously reported that intravascular fluid administration with hydroxyethyl starch, the use of small-dose combinations of spinal drugs, and the preventive administration of ephedrine may decrease the incidence and severity of hypotension and nausea/vomiting associated with combined spinal-epidural anesthesia (CSE) (6,7). In these studies we used plain or hyperbaric bupivacaine 6.6 mg and sufentanil 3.3 μg and the incidence of systolic blood pressure decreased to less than 100 mm Hg and nausea decreases from 50% to 30%. Using the same protocol in the present study, our aim was to evaluate whether the anesthetic quality and hemodynamics would favor the sitting position during spinal injection as part of a CSE technique.
After approval by the Hospital Ethics Committee and written informed patient consent, 60 ASA physical status I parturients at full-term gestation and presenting for elective cesarean delivery were enrolled in this prospective, randomized study. Women suffering from preeclampsia, hypertension, diabetes, obesity, or multiple pregnancies were excluded.
Patients were positioned either in the sitting position or the right lateral decubitus position for placement of CSE. Before initiation the of the block, each patient received 1000 mL of lactated Ringer's solution and 500 mL of Hetastarch 6% (Voluven®, Fresenius, France).
A skin wheal was raised with 1% lidocaine at the L3-4 or L4-5 interspace and, using the Durasafe Adjustable BD needle combination, the epidural space was identified with the loss-of-resistance to air technique. After identification, a 27-gauge spinal Whitacre needle was introduced. After appearance of cerebrospinal fluid, hyperbaric bupivacaine (Marcaine®; AstraZeneca, Sweden) 6.6 mg and sufentanil 3.3 μg were slowly injected with the orifice of the spinal needle directed cephalad. To obtain this combination, which has been used in our department for approximately 10 yr, 2 mL hyperbaric bupivacaine is mixed with 1 mL sufentanil 5 μg/mL and 2 mL of this mixture is injected intrathecally. After spinal injection the epidural catheter was inserted 3 cm into the epidural space. After securing the catheter and prophylactic administration of 5 mg IV ephedrine, patients were placed in the supine position with a 15° left lateral tilt. Patients remained in the sitting or lateral position for a maximum of 3 min after the subarachnoid injection. If, because of technical problems with epidural catheter insertion, this interval needed to be exceeded, patients were excluded. The anesthesiologist responsible for the further evaluation of the patient was unaware of the position selected for block placement and replaced the colleague who had performed the CSE.
The height of sensory block measured with ether swabs and the degree of motor impairment using the modified Bromage scale were evaluated every 2 min. Surgery was allowed to start when at least the T6 dermatome was anesthetized. The extent and degree of sensory and motor block obtained at incision were considered to be the maximal score, as further follow-up was considered to be impractical once surgery commenced.
In the case of insufficient initial cephalad spread, or when pain sensations reappeared intraoperatively, incremental epidural supplements consisting of ropivacaine 0.75% were injected, starting with 4 mL. When necessary, additional 2-mL boluses were given no earlier than 5 min after the preceding top-up.
Intraoperative hemodynamics were recorded every 2 min. Ephedrine in increments of 5 mg was given IV to treat hypotension, defined in this study as a decrease in systolic blood pressure 25% below baseline values or to less than 95 mm Hg. In addition, as per our routine praxis, when patients felt nauseated the same treatment was initiated regardless of the arterial blood pressure values obtained at that time. Other side effects such as nausea, vomiting, and pruritus were recorded throughout the intraoperative period.
At birth neonates were evaluated by Apgar score (at 1 and 5 min) and umbilical venous (UV) and arterial (UA) pH values.
The degree of motor block was evaluated at the end of surgery. Patients were discharged to the ward when the motor block had regressed bilaterally to a degree of Bromage-1 or less. Finally, time intervals from completion of the spinal injection until the supine position, incision, delivery, and skin closure were recorded.
The difference in lowest systolic blood pressure before delivery was used as a primary outcome parameter. For an intergroup difference of 10 mm Hg with a standard deviation of 15–20 mm Hg, it was calculated that to obtain a power of 0.8 the 2 groups had to include 25 patients. Statistical analysis was performed using the unpaired two-tailed Student-t-test and Fisher's exact test as appropriate. A P < 0.05 value was considered to be significant.
Two patients of each group were excluded because of major technical complications, i.e., protocol violation (1 patient in each group), an unintentional dural tap in the sitting group and blood in the epidural catheter in the lateral group. There were no differences in patient demographics with respect to age, weight, height, parity, and the duration of pregnancy (Table 1). Baseline arterial blood pressures were similar in both groups (126 ± 12 mm Hg versus 130 ± 12 mm Hg in the lateral and sitting group, respectively; P = 0.23).
In the lateral group, 11 (40%) patients became hypotensive as compared with 5 (18%) in the sitting group. This difference did not achieve statistical significance (P = 0.1). The lowest systolic blood pressure values achieved, however, were significantly higher in those patients who underwent CSE in the sitting position (Table 2). Hypotension was also noticed later than in the lateral group. Although the number of patients receiving additional ephedrine did not differ between groups, the total ephedrine doses administered were significantly less in the sitting group (8 ± 4.4 mg versus 14.5 ± 12.4 mg; P = 0.012). There was no difference in the incidence of nausea/vomiting, and four patients in each group were given ephedrine because of nausea without evidence of hypotension.
There were fewer technical difficulties in identification of the epidural or intrathecal space on the first attempt with patients in the sitting position (Table 3). The time interval from the spinal injection until turning the patient to the supine position was 129 ± 10 s in the lateral group which was not different from the sitting group (137 ± 11 s, NS). All patients had a sensory block reaching at least T6, but the maximal spread of the sensory block was more cephalad with the lateral position (P = 0.014) and this group also had more sensory blocks that reached higher than the T3 dermatome (50% versus 18%, P = 0.04). There were no differences in the degree of motor block at incision. More than half of the patients in both groups did not obtain a bilateral Bromage-3 motor block at incision. Because of the lower maximal height of sensory block in patients who received the block in the sitting position, more patients in this group required epidural supplementation or extension of the block (10 patients [35%] compared to 1 patient [3.5%] in the lateral group [P = 0.007]). One patient in each group received lidocaine 2% instead of ropivacaine, but was not excluded.
The interval between the spinal injection and termination of surgery was longer in the sitting group as epidural supplementation was mostly (70%) required after delivery. At the end of surgery no differences were noticed in the incidence of pruritus (12 patients in each group) or motor impairment.
Neonates had similar Apgar scores; except for 2 neonates in the lateral group all achieved a score of 9 or more at 5 min (Table 4). Whereas UV pH was equal in the two groups, the UA pH was significantly lower in those patients receiving the CSE in the lateral position.
In this study of healthy women receiving a very small-dose anesthetic solution of hyperbaric bupivacaine and sufentanil as part of a CSE technique, those in the sitting position received less ephedrine but required more epidural supplementation, whereas the neonates had higher UA pH values as compared with those whose mothers had received the block in the lateral decubitus position.
There is a lack of information regarding advantages and disadvantages of different patient positions during the initiation of spinal and CSE anesthesia. The choice of patient position usually depends on the preference of the anesthesiologist or patient, the physical characteristics of the patient, or the baricity of the drugs used. In fact, the position of the patient and baricity of the solutions injected as determinants of distribution are closely related (8).
Studies comparing the left and right lateral position were unable to find a final preference (1–3). The first investigators evaluating the sitting versus the lateral position during induction of spinal anesthesia placed patients back in the supine position immediately after a single-dose intrathecal injection (9,10). Because of the extremely short interval between injection and resuming the supine position, it is not surprising that the block characteristics did not differ significantly and that preferences in favor of the sitting position were mostly “technical” and mainly based on failure rate and ease of identification of the subarachnoid space (11).
With a CSE technique, however, substantial time may pass after the spinal injection because of the time required to place and secure the epidural catheter. Wildsmith et al. (12) demonstrated that maintaining the seated position for only 2 minutes may significantly affect the spread of the block as compared with immediately turning the patient to the supine position. Kohler et al. (13) injected 14 mg hyperbaric bupivacaine in mothers maintaining the sitting position for either 0 or 3 minutes, thus mimicking a CSE situation. They found that the longer interval was associated with a delay of the first occurrence of hypotension as well as a smaller number of blocks extending to dermatomal levels higher than T1. This is in accordance with our results.
The results of two previously published studies using CSE anesthesia were conflicting (4,5). Patel et al. (4) used the sitting position during the injection of 10 mg bupivacaine and found a longer interval for reaching the T4 dermatome and complete motor block, which required epidural supplementation in more patients as compared with the lateral position. The incidence of hypotension in that study was also noticed more often in the lateral position. In contrast, a more recent study in 22 patients by Yun et al. (5) found more severe and longer-lasting hypotension associated with larger ephedrine requirements in the sitting position. These authors used 12 mg bupivacaine and 10 μg fentanyl; all blocks were successful and did not require epidural rescuing. The conflicting findings between these studies may be explained by the different, rather large, doses of bupivacaine, some combined with an opioid, suggesting that in the lateral position decreasing the dose may in fact cause a better spread. Although many anesthesiologists still use bupivacaine doses of 10-15 mg, after having started with CSE we used much smaller doses based on our 10 years of experience during which there was no need for epidural supplementation in the majority of patients (6,7). This changing practice was highlighted and supported by Crowhurst and Birnbach (14).
Although not entirely comparable to our study design, Loke et al. (15) compared the supine position with a 10° head-up tilt after spinal injection and found increased arterial blood pressure values after 5 minutes and a lower upper sensory level in the tilted mothers. The authors explained the hemodynamic benefit of tilted patients by assuming that there were less cephalad spread of the sensory block, which was apparently more important than a possible orthostatic effect.
It is difficult to compare the various studies that have evaluated hypotension during cesarean delivery, as different end-points and definitions are used. Some studies have focused on the incidence of hypotension, nausea, or ephedrine supplementation; others have been interested in more measurable values, such as the lowest systolic or mean arterial blood pressure, ephedrine doses, and the degree and/or duration of hypotension. In addition, the definitions of hypotension differ considerably among studies. For example, using a fixed reduction of the arterial blood pressure as the definition for hypotension may not identify patients experiencing nausea despite normotensive arterial blood pressure or those starting with low baseline values and requiring ephedrine before the hypotensive criteria are met.
Regardless of the outcome variables used, our results are consistent with those of Patel et al. (4). The slower and more limited cephalad spread of sensory block may explain the reduced incidence and/or severity of hypotension. However, the reduced spread may have increased the need for epidural supplementation or extension of the subarachnoid block, mostly after delivery. Although the ability to extend or prolong the effect of the intrathecal injection has always been considered as one of the most important advantages of the CSE technique (16), others may find it unacceptable that epidural supplementation is required in 35% of the patients, as it may cause patient discomfort and significant lost time while waiting for the epidural supplementation to take effect. In addition, the epidural supplements may possibly prolong motor block at the end of the procedure. It is possible that one could use a larger intrathecal dose in sitting patients as compared with the lateral position but the risk of hypotension might increase.
Our finding of lower UA pH values in the neonates of patients who received blocks in the lateral decubitus position may be explained by the larger ephedrine dose administered to these patients. Although the dose used was moderate compared with other study protocols, and although all UA pH values were more than 7.20, this result requires further investigation to determine whether smaller pH-value differences may be obtained if phenylephrine were used as a vasopressor drug (17).
Despite technical, hemodynamic, and potential neonatal welfare, arguments against the lateral position (our position of preference for several decades), it may be unwise to recommend that the sitting position should be used in patients undergoing cesarean delivery. We concur with Russell (11), in that we believe that the sitting position is usually advantageous although there are times in which the lateral position is beneficial.
Most studies evaluating patient position have used hyperbaric local anesthetics. It is unclear how plain substances would behave, but opposite results (i.e., a more pronounced or more rapid cephalad spread) may be expected when keeping the patient in the sitting position.
In conclusion, when using a small-dose CSE technique with hyperbaric bupivacaine, the sitting position during induction of spinal anesthesia for cesarean delivery may be more beneficial.
1. Russell IF. Effect of posture during the induction of subarachnoid analgesia for caesarean section: right v. left lateral. Br J Anaesth 1987;59:342–6.
2. Kapur D, Grimsehl K. A comparison of cerebrospinal fluid pressure and block height after spinal anaesthesia in the right and left lateral position in pregnant women undergoing Caesarean section. Eur J Anaesthesiol 2001;18:668–72.
3. Law AC, Lam KL, Irwin MG. The effect of right versus left lateral decubitus positions on induction of spinal anesthesia for Cesarean delivery. Anesth Analg 2003;97:1795–9.
4. Patel M, Samsoon G, Swami A, Morgan B. Posture and the spread of hyperbaric bupivacaine in parturients using the combined spinal-epidural technique. Can J Anaesth 1993;40:943–6.
5. Yun EM, Marx GF, Santos AL. The effect of maternal position during induction of combined spinal-epidural anesthesia for cesarean delivery. Anesth Analg 1998;87:614–8.
6. Vercauteren M, Hoffmann V, Coppejans H, et al. Hydroxyethyl starch compared with modified gelatin as volume preload spinal anaesthesia for caesarean section. Br J Anaesth 1996;76:731–3.
7. Vercauteren M, Coppejans H, Hoffmann V, et al. Prevention of hypotension by a single 5 mg dose of ephedrine during small dose spinal anesthesia in prehydrated cesarean section patients. Anesth Analg 2000;90:324–7.
8. Greene NM. Distribution of local anesthetic solutions within the subarachnoid space. Anesth Analg 1985;64:715–30.
9. Bembridge M, Macdonald R, Lyons G. Spinal anaesthesia with hyperbaric lignocaine for elective caesarean section. Anaesthesia 1986;41:906–9.
10. Inglis A, Daniel M, McGrady E. Maternal position during induction of spinal anaesthesia for Caesarean section: a comparison of right lateral and sitting positions. Anaesthesia 1995;50:363–5.
11. Russell IF. Spinal anaesthesia: sitting or lateral positions? Anaesthesia 1996;51:189–90.
12. Wildsmith JAW, McClure JH, Brown DT, Scott DB. Effects of posture on the spread of isobaric and hyperbaric amethocaine. Br J Anaesth 1981;53:273–8.
13. Kohler F, Sorensen JF, Helbo-Hansen H. Effect of delayed supine positioning after induction of spinal anaesthesia for Caesarean section. Acta Anaesthesiol Scand 2002;46:441–6.
14. Crowhurst JA, Birnbach DJ. Small-dose neuraxial block: heading toward the new millennium. Anesth Analg 2000;90:241–2.
15. Loke GP, Chan EH, Sia AT. The effect of 10° head-up tilt in the right lateral position on the systemic blood pressure after subarachnoidal block for Caesarean section. Anaesthesia 2002;57:169–82.
16. Rawal N, Schollin J, Wesstrom G. Epidural versus combined spinal epidural block for cesarean section. Acta Anaesthesiol Scand 1988;32:61–6.
17. Lee A, Ngan Kee WD, Gin T. A quantitative, systematic review of randomized controlled trials of ephedrine versus phenylephrine for the management of hypotension during spinal anesthesia for cesarean delivery. Anesth Analg 2002;94:920–6.