Epidural Analgesia vs. Other Anaesthetic Techniques

Abstract:
This study compared the maternal blood and fetal outcome in women with pregnancy-induced hypertension who received epidural and other anaesthesia. Spanning a period of three years, 234 pregnant women were analyzed in the study. All had pregnancy-induced hypertension with diastolic blood pressure readings of > 95 mmHg and proteinuria > 300 mg. Epidural analgesia was given to 160 patients, 46 received general anesthesia, and 28 had local anesthesia. The maternal blood pressure was assessed before and after anesthesia was administered, and the fetal outcome was assessed by Apgar Score and Cord pH.


Introduction:
Pre-eclampsia is the most common life-threatening complication in pregnant women, although the safety of general anesthesia for delivery of patients with pregnancy-induced hypertension (PIH) has been established (Clark & Cotton, 1988).

The use of epidural anesthesia for pain relief in such patients has remained controversial. Large numbers of trained and practicing obstetricians believe that regional anesthesia is dangerous for patients with PIH because severe hypotension, necessitating the use of vasopressors and large infusion of intravenous fluids can often lead to increased fetal and maternal morbidity and mortality (Lindheimer et al., 1985). Experience, however, has proven that continuous lumber epidural analgesia is acceptable, as long as: the coagulation profile is acceptable; circulating volume is adequately maintained; maternal arterial blood pressure is pharmacologically controlled; and aorta cavil compression is avoided (Moore et al., 1985).

This controversy motivated us to study the effect of epidural anesthesia on PIH patients


Aim of this Work:
Our aim was to elucidate the effect of epidural anesthesia in patients with PIH, and also to compare the fetal and maternal outcome among patients delivered with either epidural, general or local anesthesia.


Patients and Methods:
This study was carried out from March, 1992, to June, 1995. The 234 patients chosen for the study were suffering from PIH. 160 patients were admitted early in labor and were given epidural analgesia. The 28 patients who went into labor and arrived at the hospital too late for regional anesthesia served as the control group to vaginally delivered patients. 46 patients had elective Caesarean section (C.S.) deliveries under general anesthesia, and out of the 160 patients who received epidural anesthesia, 20 cases delivered by C.S. Out of 234 patients overall, a total of 66 patients delivered by C.S..

Four groups of patients were identified:

• Group (I): Patients and infants delivered vaginally with epidural analgesia (140 patients).
• Group (II): Patients and infants delivered vaginally with local anesthesia (28 patients).
• Group (III): Patients and infants delivered by C.S. with epidural anesthesia (20 patients).
• Group (IV): Patients and infants delivered by C.S. with general anesthesia (46 patients).

Epidural Anesthesia:
Before an epidural was given, the procedure was explained to each patient and consent was obtained. An intravenous infusion was sited before insertion of the epidural, and the circulation was preloaded with 500 ml of crystalloid to decrease incidence of hypotension. A 17-gauge epidural needle was inserted into the second or third lumber epidural space by loss of resistance to saline technique under complete asepsis. A 20-gauge teflon catheter was then threaded to 5 cm cephalad while ensuring the absence of blood, C.S.F. or paraesthesia. Following careful inspection of the catheter after aspiration failed to reveal C.S.F. or blood, a test dose of 3 ml 0.25% bupivacaine was injected between contractions to decrease false negative. This was done to exclude intrathecal or intravenous placement Following assessment of the test dose, 10 ml 0.25% of bupivicaine was profressively injected with careful haemodynamic and fetal monitoring.

Each patient was instructed to lie on her side to prevent supine hypotension. Arterial blood pressure was monitored every 2 min. for the first 10 min, and then every 10 min. When unilateral analgesia occurred, the patient was turned on her other side and more local anesthesia (5-10 ml) was injected.

General Anesthesia:
This group received general anesthesia with labetalol pretreatment as 20 mg, initially followed by of 10 mg increments every 3 min., but not exceeding 1 mg/kgm of body weight.


Results:
The age of patients who received epidural analgesia ranged from 20-31 years, with a mean of 26.9 +/- 5.4. The mean age of patients who received the local anesthesia was 24.61 +/- 4.6 years, and those who received general anesthesia for C.S. had a mean age of 23.6 +/- 3.9 years.

The parity for group I was 70% primigravida, 80% primigravida for group II, 60% primigravida for group III and 70% primigravida for group IV. The duration of second-stage labor was 1.2 hours in group I and 0.7 hours for group II, with statistical significance (P. 0.001). [Table 1] The maternal blood pressure was 170/95 +/- 18/13 mmHg in group I, and 175/110 +/- 22/12 mmHg in group II. There was significant statistical difference, as the blood pressure of group I was greatly reduced to level 130/85 +/- 20/18 mmHg, with P. Value of 0.01. [Table 2]

The neonatal outcome for group I and group II regarding the Apgar Score, the birth weight and abnormal heart rate was not statistically significant. [Table 2] The maternal blood pressure before anesthesia was 160/95 +/- 17/12 mmHg in group III, and 170/110 +/- 24/13 mmHg in group IV. There was significant statistical difference. The blood pressure of group III was greatly lowered to the level of 130/90 +/- 20/16 mmHg (p value < 0.01). [Table 3] The neonatal outcome for group III and group IV regarding Apgar Score after 1 min was statistically significant, but not significant after 5 min. [Table 3]

Table (1): Maternal Outcome with Group I & II

Table (2): Maternal and Neonatal Outcome with Vaginal Delivery Group I & II

Table (3): Maternal and Neonatal Outcome with Group III & IV (deliveries C.S.)

Discussion:
Patients with mild PIH generally only require caution during anesthesia. However, patients with severe PIH are critically ill and require stabilization prior to any anaesthetic.

We studied maternal and fetal outcome following delivery with continuous epidural anesthesia in patients with PIH. It was found that epidural anesthesia is an effective and safe method for pain relief during labor. The elimination of labor pain and allaying of anxiety in patients during labor subsequently reduces the sympathetic activity, causing vasodilatation and dropping of the blood pressure

In our study, the drop in blood pressure was significant in the group that delivered vaginally with epidural analgesia and the maternal and fetal outcomes were similar to the deliveries with local perineal infiltration. Therefore, the maternal and fetal morbidity were not increased when epidural analgesia was administrated to patients with PIH. Graham and Goldstein (1980) said that with epidural analgesia, the maternal and fetal outcomes were similar to deliveries with local perineal infiltration; thus, the maternal and fetal morbidity are not increased when epidural analgesia is administrated to patients with PIH. Giraham and Goldstein (1980) also said that epidural analgesia does not alter the cardiac output of pre-eclamptic, as long as the patient is adequately hydrated. After adequate intravascular volume expansion and maintenance of uterine displacement, lumber epidural analgesia actually increases uterine artery (Ramos-Santos et al., 1991) and mean intervillous blood flow (Joupilla et al., 1982). Furthermore, there were no cases of fetal heart abnormalities nor material hypertension when the above regiment was followed.

In group IV, we found that there was a significant increase in blood pressure and maternal heart rate in comparison with group III, in which patients were well hydrated and aorto-caval compression was avoided.Hodgkinson et al. (1980) said that induction of general anesthesia and tracheal intubation carry the risk of sudden maternal hypertension, perhaps beyond the limits of cerebral blood autoregulation. Although this is a danger of general anesthesia, some centres will not use epidural block for Caesarean delivery of pre-eclamptic parturients for fear of sudden and refractory hypotension, leading to profound uteroplacental insufficiency in an already-compressed gestation (Andrew and Malinow 1991).

Others confirm that in cases of epidural anesthesia without hypotension, the conditions of newborns at birth are better, even if uterine delivery time is prolonged (Stoeling & Millar 1984).

In our study there was a prolongation of the second stage of labor in patients receiving epidural analgesia. The possible cause of this prolongation could be lumbosacral neuromotor blockade with epidural analgesia, which may reduce the effectiveness of uterine contractions, plus abolish bearing power.
Miller et al. (1993) said that the second stage of labor may be prolonged during epidural analgesia as a result of the loss of the bearing down reflex and reduce the efficacy of maternal explosive effort. It is no longer considered necessary to terminate the second stage of labor after a set time (1-2 hours), provided there is no evidence of fetal distress.

CONCLUSION:
Continued lumber epidural anesthesia is the best technique for managing patients with PIH. Epidural anesthesia should not be used to correct hypertension, but it has many advantages over other anaesthetic techniques, as it produces complete pain relief and negates the need for maternal narcotics which depress ventilation and have adverse effects on preterm babies. On the other hand, it prevents the increase in blood pressure associated with bearing down, avoiding increased cerebral spinal pressure, and it is also more effective than general anesthesia in controlling the blood pressure and avoiding the swings in blood pressure due to tracheal intubation in C.S. deliveries. It is also abolishes the neurally imposed vasoconstrictor and reduces the circulating catecholamines that occur with anxiety and labor pains.

Thus, in the absence of coagulopathy, continuous epidural anesthesia is the anesthetic of choice for most patients with PIH during labor, regardless of vaginal or Caesarean section delivery.

References:

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