Table Tilt Versus Pelvic Tilt Position for Intrauterine Resuscitation during Spinal Anaesthesia for Caesarian Section

Abstract

Background:

This study was undertaken to compare the effects on intrauterine resuscitation by table tilt versus pelvic tilt position after spinal anaesthesia for Caesarian Section.

Patients & Methods:

Fifty ASA I and II patients who fulfilled the eligibility criteria were enrolled in the study and were divided into two groups: group W (Pelvic tilt with wedge under right hip and group L- (15⁰left lateral table tilt) and received spinal anaesthesia. The following parameters were recorded. Heart rate (HR), mean arterial pressure (MAP) at baseline, 2mins, 5 min and then 5 min thereafter. Mean height of block, Total no. of segments blocked, Onset Time of sensory block (in Minutes), ephedrine doses, incidence of hypotension & bradycardia, APGAR score at 1& 5 Minutes.

Results:

The decrease in MAP was much more in wedged position as compared to table tilt position also the incidence of hypotension was 40% in wedged position as compared to 12% in table tilt position. Mean height of block, Total no. of segments blocked, and boluses of inj. ephedrine used were more in the wedged position than in table tilt position.

Conclusion:

Wedge placement caused increased incidence of hypotension and higher blockade after spinal anaesthesia as compared to left lateral table tilt position, there was no adverse effects on foetus and patients tolerated wedge better than left lateral table tilt position. Also surgery was easier to perform after wedge placement.

Recently the role of intrauterine resuscitation (IUR) to improve O2 delivery to the placenta and umbilical blood flow, for reversal of foetal hypoxia and acidosis has been recognized.¹ However, fewer studies have evaluated the role of IUR by maneuvers and drugs for improvement of foetal wellbeing.

Aortocaval compression is an important cause of reduced foetal oxygenation. The syndrome of “Supine hypotension” presents an enigmatic challenge to an obstetric anesthesiologist. Mostly parturients don't t experience any symptoms, but in about 10 % of cases venous return of heart may get seriously impaired assuming supine position¹. Hypotension, tachycardia, nausea, dizziness, syncope and decreased uteroplacental perfusion² may occur due to aortocaval compression.

Anaesthetic drugs (vasodilating) and or techniques (neuraxial) that cause sympathectomy may exacerbate the impact of aortocaval compression³. These changes in blood volume and cardiac output may become more critical for parturients who have concomitant cardiac disease (complain of shortness of breath, palpitations, dizziness, oedema, and poor exercise tolerance⁴), may also have an impact on healthy parturients.

Decreased cardiac output secondary to vena-cava obstruction by the gravid uterus can be prevented by lateral tilt position⁵. To alleviate this, conventionally, a small pillow or “wedge” is used to provide left uterine displacement of 15 to 20 degrees. This angle can be increased as necessary by increasing the wedge or tilting the table. Cardiac output did not significantly improved when the patient was placed supine or with tilt < 15 degree.⁶,⁷ So the recommendation of tilt is at least 15° or more. Crawford (1972)⁸, advocated the use of a wedge shaped cushion (10 cms of height), arbitrarily angled at 15°.

The anaesthesiologists are actively involved in IUR especially during establishment of regional anaesthesia for delivery of foetus. Therefore, we designed a randomized prospective study to compare the role of two different maternal positions table tilt versus pelvic tilt position on intrauterine resuscitation in pregnant patients following caesarian section under spinal anaesthesia.

PATIENTS & METHODS

After obtaining approval from ethical committee we recruited 50 ASA grade I / II patients who were scheduled to undergo non emergent lower segment caesarian section. Females of age between 20-35 yrs having a height of 145-165 cm and weight of 45-70 kg were included after written informed consent. Patients with diagnosed fetal distress, signs and symptoms of labor, prematurity (<37 wks of gestation), multiple pregnancies, hypertension, preeclampsia, obesity, intrauterine growth retardation (IUGR) or any other factors contraindicating a standard spinal anesthetic technique were excluded from the study. All patients were randomly allocated into two groups of 25 patients in each by computer generated numbers.

GROUP (W) - Pelvic tilt with wedge under right hip.

GROUP (L) - 15° left lateral table tilt.

All patients were preloaded with Ringer's s lactate solution (10 ml kg^-1) along with premedication of metoclopromide (10 mg) i.v., ranitidine (50) mg i.v., 15 mins prior to surgery.

Spinal anaesthesia was given at L3-4 interspace using 26 G Quincke's needle. Bupivacaine heavy (12.5 mg) was injected over 15 sec. In subarachnoid space. Patients were put in the position according to the group assigned.

In group W, patients were made to lie supine with a wedge beneath the right hip of the patients which was made by rolling of three drape towel together, placed below the hip, to tilt the pelvis to 15°. By this way the pelvis lift at right side was approximately 10 cms.

In group L, the table was tilted to left side by 15 degrees. Each complete turn of the lateral tilting screw tilted the patient by 3.5-4 degrees. Four complete turns were required to tilt the patient left laterally by 15 degrees. If the patient felt intimidated by the tilted position, an assistant was kept to support the patient.

Sensory block was assessed at one minute interval by using loss of sensation to touch using tooth pick. Motor block was assessed by modified Bromage scale (0-No paralysis, 1-Inability to raise extended leg, 2-additional inability to flex the knee, 3-additional inability to flex ankle). Time of onset of sensory blockade at T10 and maximum height of dermatomal block at 15 min. or when there was no change in three consecutive reading, were assessed. Recordings of blood pressure were done by an automated sphygmomanometer at baseline, 2 mins, 5min then every 5 mins. At the similar time interval, pulse rate and SpO2 were also noted. 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. Unpaired two-tailed Student-t-test and Chi Square test were used for evaluating inter group parametric & nonparametric data respectively. For intragroup comparison of blood pressure (SBP, DBP and MAP) and heart rate, paired T test was used, p value < 0.05 was considered to be significant.

RESULTS

Demographic profile was comparable with respect to age, weight, and height in both the groups. The effect of two different positions on heart rate (HR) in the two groups (Group L: left sided table tilt and Group W: left sided pelvic tilt) were statistically similar (p>0.05) at varying time interval (Table-2). However, significant difference in mean arterial blood pressure (MAP) was noted after 2 minutes of spinal blockade between two groups {p= 0.035 (p<0.05)} (table-2). The decrease in MAP was much more in wedged position as compared to table tilt position and the incidence of hypotension was 40% in wedged position as compared to 12 % in table tilt position. Hence, more doses of vasopressor were required to treat hypotension in group W as compared to group L patients (table-3).

Table 2.

Heart Rate (HR) & Mean Arterial Pressure (MAP) in 2 groups

Table 3.

Comparative Block characteristics & Haemodynamics

Table 1.

Patients' demographic profile

The final mean height of block achieved was higher in group W (T3.72±1.27) as compared to group L (T5.56±1.30) (p<0.05). Total numbers of segments blocked (counted from T12) were significantly higher in group W as compared to group L (8.16± 1.34 and 6.44±1.29 in group W and L respectively) p value < 0.05 (Table-3). None of the patient required any additional analgesics.

The effect of intrauterine resuscitation on neonatal well being was assessed by APGAR Scoring at 1minutes and 5 minutes interval which was found statistically similar ( p= 0.327 and p= 0.691 at 1& 5minutes respectively (Table-4).

Table 4.

Mean APGAR Score

DISCUSSION

The importance of supine hypotension syndrome was understood since early days when various authors reported cases of hypotension, syncope, palpitation and shock occurring in the third trimester of pregnancy. In routine obstetric practice for the sake of intrauterine resuscitation (IUR) parturients are usually kept in the lateral position but they have to be placed supine for caesarean section. Therefore a need for uterine displacement device was felt. Various devices were tried such as a 15° wedge⁸, inflatable wedge⁹,¹⁰ and left lateral table tilt positions¹³,¹⁴,⁶ of various angles. It was noted that initial position of the patient just after placement of spinal block affect the maximum height of block attained and thus degree of hypotension.¹¹,¹²

In the present study the relative efficacy of two different maneuvers were compared in a prospective randomised manner following spinal anaesthesia. The left uterine displacement was done by either table tilt or pelvic method for prevention of aortocaval compression and intra uterine resuscitation. The changes in haemodynamic parameters and block characteristics in two different positions were assessed and compared at varying time interval. The heart rate was found to be similar at different time point in both the groups. However, it was noted that in the group W, hypotension occurred within 2 minutes of spinal anaesthesia and 5 minutes in the lateral tilt group. Hence more number of boluses of vasopressor were required in wedge group (n=12) as compared to boluses in left lateral table tilt group (n=3). The explanation for the higher block and subsequent hypotension in the wedge group could be the increased cephalad spread of hyperbaric bupivacaine in the wedged group. When a wedge of nearly 10 cm height was placed under the right hip of patients the pelvis became higher as compared to shoulder, thus with gravitational drag hyperbaric bupivacaine might have spread more cephalad in group W as compared to group L, where pelvis was almost at the same height as the shoulder. The increased cephalad spread of bupivacaine was higher in the wedge group (more thoracic dermatome was blocked) resulting in increased incidence of hypotension requiring treatment with vasopressor. Many investigators have also suggested an increased incidence of hypotension in the wedge positioN.¹¹,¹²

Other studies have also considered these similar end-points for evaluating the incidence of hypotension that is, the lowest systolic or mean arterial blood pressure recorded, degree and/or duration of hypotension, ephedrine supplementation, vasopressor doses, and incidence of nausea during regional anaesthesia.¹¹,¹²,¹³,¹⁵ However, the definition of hypotension differed considerably among different studies.

The incidence of bradycardia was similar in both the groups, where 1 out of 25 patients recorded heart rate of <50 bpm. In the present study it was noted that APGAR scores at 1min and 5 mins after birth were similar in both the groups (p>0.05). Despite increased incidence of hypotension and increased inj. ephedrine usage in wedge group, the APGAR scores were similar. Various authors have also found no difference in APGAR scores even if increased doses of vasopressor were used.¹⁵

It is suggested that APGAR score is not a sensitive parameter to judge foetal effects of hypotension or aortocaval compression as suggested by other studies where APGAR scores failed to follow trends of foetal acidosis following maternal hypotension intraoperatively.¹⁵ Cord blood pH¹⁶,¹⁷ and foetal tochography would have been a better indicator of foetal effects of aortocaval compression which was not recorded in the present study.

In the present study it was noted that patients felt uncomfortable in the table tilt position. Patients in table tilt position had to be assured constantly that they will not fall off the table. Many times an assistant was required to stand by the patient. Other authors have also experienced similar fear in their patients.¹⁹,⁶ It was noted that patient would slide off the table when the tilt is > 28 degrees.¹⁹ In this study the maximum table tilt was only 15°, half that is needed for the patient to slide off the table. With the use of wedge, patients were more relaxed with no such fears of falling off.

In the group W, the surgeons were able to perform caesarean section easily but were not comfortable and requested shifting the table back to horizontal or at least reducing the lateral tilt. The table tilt < 15° was found to be inefficient in relieving the aortocaval compression.⁶

In conclusion we found that although wedge placement caused increased incidence of hypotension and higher blockade after spinal anaesthesia as compared to left lateral table tilt position, there was no adverse effects on foetus and patients tolerated wedge better than left lateral table tilt position. Also surgery was easier to perform after wedge placement than with left lateral table tilt. Still further studies are required for evaluation of optimal dose of local anaesthetic whenever wedge is used.