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Canadian Journal of Anesthesia 48:890-893 (2001)
© Canadian Anesthesiologists' Society, 2001
Obstetrical and Pediatric Anesthesia

The Trendelenburg position increases the spread and accelerates the onset of epidural anesthesia for Cesarean section

[La position de Trendelenburg permet une plus grande distribution de l'anesthésie épidurale et en accélère le début d'action lors de la césarienne]

Ahmad R. Setayesh, MD*, Ali R. Kholdebarin, MD*, Masoud Saber Moghadam, MD* and Hamid R. Setayesh, MD{dagger}

* From the Department of Anesthesiology, School of Medicine, Iran University oof Medical Sciences and Healt Services (iums) and
{dagger} Statistical and Research Consultant, Council for Planning in Therapeutic Affairs, Iranian Ministry of Health & Medical Education, Tehran, Iran.

Address correspondence to: Dr. A.R. Setayesh, Department of Anesthesiology, School of Medicine, Iran University of Medical Sciences, Tehran 14455, Iran. Phone: ++98 21 8083029; Fax: ++98 21 8590054; E-mail: Setayesh{at}iums.ac.ir


   Abstract
TOP
 Abstract
Introduction
 Materials and methods
 Results
 Discussion
 References
 
Purpose: The effect of position on the spread and the onset time of epidural anesthesia has not been well documented. This study was undertaken to assess the effect of modified Trendelenburg position on the spread of epidural anesthesia for Cesarean section.

Methods: Seven hundred thirty-nine parturients underwent epidural anesthesia for elective or emergent Cesarean section. Patients were divided into two groups in a randomized-controlled study. All patients received 20 mL of 2% lidocaine injected through a 19G epidural needle, a standard technique in our institution. During induction of epidural anesthesia, the first group was placed in 15 Trendelenburg with 10 head-up position and the second in the horizontal position. The onset time and the level of anesthesia, patients' vital signs, and Apgar score were recorded in both groups.

Results: There were no significant differences in vital signs, oxygen saturation and Apgar score between the two groups. The results show significant differences in the time of onset (on average four minutes faster in the modified Trendelenburg position group) (P <0.001), and in achieving T5 level sensory blockade (97.5% vs 42.8%) between the modified Trendelenburg and horizontally positioned pregnant women.

Conclusion: This study demonstrates that the modified Trendelenburg position has a significant effect on the spread and the onset time of single shot epidural anesthesia, and can be used safely in term parturients for emergency or elective Cesarean section.


   Introduction
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 Abstract
 Introduction
Materials and methods
 Results
 Discussion
 References
 
EPIDURAL anesthesia is a common and safe technique for Cesarean section. One of the major problems with this technique is the time needed to achieve the desirable level of anesthesia in an emergency situation. There are several reports on the effect of position on the spread of epidural anesthesia. Apostolou and Grundy showed that the position has a significant effect on the spread of epidural anesthesia.1,2 In contrast, Norris and Merry did not obtain the same results.3,4 In this study we compared the onset and the spread of epidural blockade between a modified Trendelenburg and horizontally positioned pregnant women during induction of epidural anesthesia for Cesarean section.


   Materials and methods
TOP
 Abstract
 Introduction
 Materials and methods
Results
 Discussion
 References
 
Over a ten-month period (May 1999–February 2000), we studied term parturients, admitted to Akbarabadi Obstetrics and Gynecology Hospital (Tehran, Iran). Pregnant women requiring Cesarean section for delivery participated in this study after giving written consent to the investigation. Women with morbid obesity, underlying disease, and intra uterine fetal death were not included. The cases were divided into two groups based on a simple random allocation.

Epidural anesthesia was performed in the sitting position. A 19 gauge Tuohy needle, was introduced into the epidural space, using a midline approach at the L3–L4 interspace with loss of resistance to air technique. A test dose (lidocaine 2% 3 mL and 15 µg epinephrine) was injected and after observing no signs of intravascular or intrathecal injection, 20 mL 2% lidocaine with 2 mL 7.5% bicarbonate was injected incrementally through the needle at a rate of approximately 1 mL•sec–1. After induction of epidural anesthesia, patients in group I were placed in 15 Trendelenburg with 10 head-up position (modified Trendelenburg, Figure 1Go), and group II in a horizontal position. Both groups were positioned with left uterine displacement.



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  		FIGURE 1 Modified Trendelenburg position.

 
Monitoring devices in the operating room included an electrocardiograph, a noninvasive automated blood pressure device and a pulse oximeter. Epidural technique, volume and concentration of drugs were the same in both groups, the only difference being the position of patients after epidural anesthesia. All patients were given one litre of lactated Ringer's solution before the administration of epidural anesthesia, then as needed.

Loss of sensation to pinprick was assessed at 30-sec intervals. The highest level of anesthesia was defined as T5 or the level of anesthesia that remained fixed for three minutes. After achieving the T5 level or a fixed level of anesthesia, patients in group I were placed in the horizontal position. After delivery, all patients received midazolam and oxytocin. Evaluation of the newborn was performed using Apgar score at one and five minutes. Data were analyzed by the appropriate statistical tests (means difference test and nonparametric difference tests) using SPSS for Windows package.


   Results
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 Abstract
 Introduction
 Materials and methods
 Results
Discussion
 References
 
Seven hundred thirty-nine patients were studied; 363 were in group I and 364 were in group II. Twelve patients were excluded from the study because of technical failure. There were no differences in maternal age, weight, parity, and Apgar score between the groups (TableGo). Ninety-seven percent of patients in group I had an adequate level of sensory block (T5); 31.7% of patients achieved this level in less than six minutes, 77.4% in less than eight minutes and 97.4% in less than ten minutes (Figure 2Go). In group II only 47.4% achieved an acceptable sensory block (T5–T6) in less than ten minutes (between eight and ten minutes) (P <0.001 vs group I). Globally, 42.8% achieved a T5 sensory block, 40.8% a T6 sensory block while the remainder had an upper level of sensory block between T6 and T8. A decrease in blood pressure requiring treatment with ephedrine occured in 5% of mothers.


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  		TABLE Brief comparison of selected variables between subjects in each group
 


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  		FIGURE 2 Percentage of subjects in each group achieving T5 sensory block over time.

 

   Discussion
TOP
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
References
 
The Akbarabadi Obstetrics and Gynecology Center performs more than 2800 Cesarean sections annually and the usual anesthetic technique for Cesarean section is epidural injection of anesthetic solution through a Tuohy needle. Although slow and incremental injection of local anesthetic through a catheter is generally accepted and safer, we use a single dose technique for Cesarean sections because, in our center, there are not enough epidural catheters available. The major problems with this technique are hypotension and a delay in achieving adequate sensory block level in an emergency situation. Several investigations have assessed the effects of posture on the spread of epidural anesthesia in the lateral and head-up position but their results are conflicting. In two different studies Grundy et al. compared the effect of pregnancy and lateral position on the spread of epidural anesthesia and found no difference on the spread of epidural anesthesia in pregnant and non-pregnant women,5 but showed that the lateral position has a significant effect.2 This latter finding was subsequently confirmed by Husmeyer and White, and Apostolou.1,6 Ponhold showed head-up position not only decreases the maximum cephalad spread of local anesthetic but also provides better anesthesia in lower segments during epidural anesthesia.7 In contrast, Norris studied term pregnant women and reported that gravity does not augment the spread of epidural anesthesia for Cesarean section.3,8 In these studies, Norris used 3% chlorprocaine, a local anesthetic drug with rapid onset and anesthetic levels were checked every five minutes. This may influence the conclusion of his results. Whalley et al. observed no significant difference in the final level of cephalad spread and the degree of motor block, but found that the time to maximum cephalad spread was shorter in the sitting position, implying that the local anesthetic spreads faster against the gravity.9 In 1999, White mentioned the possibility of cephalad spread of the epidural block.10 In our study, we used a modified Trendelenburg position, which has not been evaluated before, and found significant differences in the time of onset and to achieve a T5 level of sensory blockade when compared to the horizontal position. Theoretically, the Trendelenburg position can increase the possibility of regurgitation, although this was not a problem clinically. In this study the maximum cephalad spread of epidural blockade was not measured. However, on average, the upper level of anesthesia in group I was higher than in group II.

Our results indicate that the patient's position not only has a significant effect on the time of onset, but also augments the spread of anesthesia in term pregnant women who receive a single injection of local anesthetic solution in the epidural space for Cesarean section.



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  		FIGURE Lunenburg - Nova Scotia

 

   Acknowledgments
 
We wish to thank the medical and nursing staff of Akbar-Abadi Maternity Hospital. Appreciation is also expressed to Mrs. Mahasti Nadertabar for drawing the figure and Dr. Katayoun Rahnavardi for her useful suggestions and translating the abstract to French.


   Footnotes
 
This work should be attributed to the Department of Anesthesiology, Iran University of Medical Sciences & Health Services (IUMS).

Revision received July 5, 2001. Accepted for publication November 24, 2000.


   References
TOP
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
1 Apostolou GA, Zarmakoupis PK, Mastrokostopoulos GT. Spread of epidural anesthesia in the lateral position. Anesth Analg 1981; 60: 584–6.[Abstract/Free Full Text]

2 Grundy EM, Rao LN, Winnie AP. Epidural anesthesia and the lateral position. Anesth Analg 1978; 57: 95–7.[Abstract/Free Full Text]

3 Norris MC, Leighton BL, DeSimone CA, Larijani GE. Lateral position and epidural anesthesia for cesarean section . Anesth Analg 1988; 67: 788–90.[Free Full Text]

4 Merry AF, Cross JA, Mayadeo SV, Wild CJ. Posture and the spread of extradural analgesia in labour. Br J Anaesth 1983; 55: 303–6.[Abstract/Free Full Text]

5 Grundy EM, Zamora AM, Winnie AP. Comparison of spread of epidural anesthesia in pregnant and nonpregnant women. Anesth Analg 1978; 57: 544–6.[Medline]

6 Husemeyer RP, White DC. Lumbar extradural injection pressures in pregnant women. An investigation of relationships between rate of injection, injection pressures and extent of analgesia. Br J Anaesth 1980; 52: 55–60.[Abstract/Free Full Text]

7 Ponhold H, Kulier AH, Rehak PH. 30 trunk elevation of the patient and quality of epidural anesthesia. Effects of elevation in operations on the lower extremities (German). Anaesthesist 1993; 42: 788–92.[Medline]

8 Norris MC, Dewan DM. Effect of gravity on the spread of extradural anaesthesia for cesarean section. Br J Anaesth 1987; 59: 338–41.[Abstract/Free Full Text]

9 Whalley DG, D'Amico JA, Rybicki LA, et al. The effect of posture on the induction of epidural anesthesia for peripheral vascular surgery. Reg Anesth 1995; 20: 407–11.[Medline]

10 White N. Cephalad spread of epidural blockade in a 15-degree head-down position (Letter). Anesthesia 1999; 54: 1019–20.[Medline]




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