A simple safe method for continuous infusion epidural analgesia in obstetrics

Comparison of intermittent epidural bolus, continuous epidural infusion and patient controlled-epidural analgesia during labor

The aim of the study was to compare efficacy and side-effects produced by three techniques of epidural analgesia during labor: intermittent bolus (1B), continuous epidural infusion (CEI) and patient-controlled epidural analgesia (PCEA). One hundred and fifty parturients allocated randomly to three groups received the same epidural solution of bupivacaine 0.125% with sufentanil 0.5 microg/mL. In the first group (IB: n=50) boluses were administered by the anesthesiologist and titrated to achieve adequate analgesia. In the second group (CEI: n=50) an 8 mL/h continuous infusion was delivered. In the third group (PCEA: n=50) parturients self-administered 5 mL boluses, with a lock-out interval of 10 min and a 4 h maximum dose of 50 mL. Insufficient analgesia in the CEI and PCEA groups was treated by extra boluses of the same solution. Quality of analgesia measured by visual analog scale (VAS), and maternal satisfaction were comparable in the three groups. Hourly consumption of bupivacaine was lower in the 113 group compared to the PCEA and CEI groups (p<0.05). The number of extra boluses was significantly higher in the CEI group compared to the PCEA group (32% vs. 12.5%). Motor block was significantly more frequent in the CEI group compared to the 113 group. The other side-effects were equally distributed in the three groups. We concluded that PCEA with bupivacaine and sufentanil is a valuable technique and a good alternative to the IB method. Compared to the CEI technique, PCEA allows a decrease in local anesthetic consumption without impairing the quality of anesthesia.

Continuous versus intermittent epidural analgesia. A randomised trial to observe obstetric outcome

A randomised study of 381 women was carried out to compare the obstetric outcome after epidural analgesia maintained by an intermittent top-up regimen or with a continuous infusion. The two groups were well matched with respect to age, parity, mode of onset of labour and indication for epidural. Maintenance of epidural analgesia by continuous infusion resulted in a significantly decreased need for top-up doses. A reduction in the incidence of hypotension, cardiotocographic evidence of intrapartum fetal hypoxia and Caesarean section was associated with this. It is concluded that the maintenance of epidural analgesia by continuous infusion is a safe and reliable method and may be more advantageous and less labour intensive than the traditional intermittent regimen.

Continuous epidural infusion of 0.075% bupivacaine for pain relief in labour. A comparison with intermittent top-ups of 0.5% bupivacaine

Seventy-three women who requested epidural analgesia during labour were randomly allocated in a prospective study to receive either a continuous epidural infusion of 0.075% bupivacaine at a rate of 12-18 ml/hour (38 mothers) or intermittent top-ups of 0.5% bupivacaine (35 mothers). Both groups received an initial dose of 6-8 ml bupivacaine 0.5%. Patients were asked to score their pain using a 10-cm linear scale prior to insertion of the epidural, 30 minutes after its insertion and hourly thereafter. The quality of analgesia in the continuous infusion group was significantly better than in the intermittent top-up group (p less than 0.025). There was no significant difference in the total dose of bupivacaine given to the two groups.

Epidural analgesia with a bupivacaine-fentanyl mixture in obstetrics: comparison of repeated injections and continuous infusion

We compared the efficacy and side-effects of continuous infusion versus repeated injections of epidural bupivacaine-fentanyl during labour. Forty-four parturients were randomly distributed into two groups balanced for population size, morphology and parity. Analgesia was begun at the same stage of labour with a mixture of 20 ml 0.25 per cent plain bupivacaine and 2 ml (100 micrograms) fentanyl. In Group I the initial dose ranged from 8-12 ml as a function of height; an injection of the same dose was repeated immediately upon recurrence of pain. In Group II, after an initial dose of 5-7 ml, a continuous infusion of 3 ml.h-1 was begun, and continued until full dilatation. Analgesia was rated using a pain scale; effects on maternal blood pressure, respiratory rate and neonatal status were noted. Bupivacaine and fentanyl assays were carried out on maternal venous blood in 30 parturients during the course of labour. There was a longer latency to onset of analgesia in Group II (approximately five minutes), followed by a more constant degree of analgesia. This better analgesia cannot be accounted for by a difference in dosage; doses were significantly lower in Group II, despite the fact that labour was of the same duration. The course of labour, and maternal and neonatal status were comparable in the two groups. Assays showed no difference in bupivacaine blood concentrations between the two groups nor signs of drug accumulation. The constant infusion technique is advantageous since it provides a more regular degree of analgesia with lower doses than those required for patients having repeated injections.

The loading dose for continuous infusion epidural analgesia. A technique to reduce the incidence of hypotension

The effects of 0.08% and 0.5% bupivacaine, given in equal volumes as the loading dose prior to continuous infusion epidural analgesia, were compared. The incidence of hypotension, as well as the height of sensory blockade, was markedly lowered by reducing the loading dose of bupivacaine. However, the efficacy of the epidural analgesia was maintained by using the same volume for the loading dose. The mean onset of analgesia was delayed from 9.1 to 13.6 minutes. There were fewer calls for intervention consequent upon the reduction in adverse effects. The use of 8 ml 0.08% bupivacaine for the loading dose or for subsequent top-ups is recommended. The concept of a liquid sleeve of local anaesthetic in the epidural space is further supported.

Continuous infusion epidural analgesia in obstetrics. A comparison of 0.08% and 0.25% bupivacaine

The effects of 0.08% (Group A) and 0.25% (Group B) solutions of bupivacaine were compared in a random manner, to assess continuous pump infusion epidural analgesia in labour. Both solutions were infused at a dose rate of 20 mg bupivacaine/hour. The results in all the mothers who had received infusions lasting more than 4 hours were studied. There were 25 in Group A and 28 in Group B. Any treatment during the infusion epidural for inadequate analgesia, hypotension, etc., was recorded as an intervention. The mean of the intervention-free intervals was significantly greater in Group A than in Group B, and significantly fewer top-up injections were required in Group A. The results show that the administration of a 0.08% solution of bupivacaine into the epidural space by continuous pump infusion is more labour saving than the infusion of a 0.25% solution. The concept that a greater volume infusion rate maintains a more extended liquid sleeve of local anaesthetic in the epidural space is supported.

[Maintenance of obstetrical analgesia by continuous perfusion into the peridural space]

Two methods of epidural analgesia were compared in two randomized groups each of 16 normal women in labour, using bolus or continuous infusion. Analgesia was provided by a mixture of bupivacaine 0.25% and fentanyl. Patients did not differ in age, weight, term as well as in parity and neonatal weight. Group A received a total dose of 34 +/- 7.5 mg bupivacaine and 87 +/- 23.8 micrograms fentanyl as a bolus and group B a total dose 40.6 +/- 11.5 mg bupivacaine and 131 +/- 43.5 micrograms fentanyl as a starter dose followed by constant infusion. There was no statistical difference between the two groups concerning length of labour, number of forceps, Apgar score and patient, obstetrician and anaesthetist satisfaction score. Although continuous epidural infusion was greatly appreciated by the obstetrical team, it would seem to be of interest only when labour is long enough to require larger doses, especially when labour is induced.

A comparison of continuous flush devices

Six different makes of continuous flush device were compared for reliability of flow rate and ease of use. All of the devices tested were considered suitable for flushing of vascular pressure monitoring catheters. However, flow rates were considered too variable for control of drug infusions or flushing of intracranial pressure monitoring systems.

A multiple-purpose automatic pressure regulator

The Gairdner Hospital Automatic Pressure Regulator was developed to deliver a constant pre-set gas pressure for the continuous inflation of infusion pump cuffs or pneumatic tourniquets. It has been found to be economical, safe, reliable and easy to use. The device facilitates both continuous flushing of catheters and rapid intravenous infusions especially during emergency situations. It may also be used in other clinical situations where a continuous gas supply at a pre-set constant pressure is required.

Clinical experience with continuous epidural infusion of bupivacaine at 6 ml per hour in obstetrics

Maintenance of continuous epidural analgesia for obstetrics by slow infusion is a feasible alternative to maintenance by intermittent injection. The method described by Davies and Fettes using 0.25 per cent bupivacaine through a 6 ml/hr capillary flow device (Intraflo), with the fast-flush cut-off, is simple and convenient. However, failure of the fast-flush valve, resulting in a high flow rate, has been reported. It is therefore imperative that, prior to connecting the pressurized system to the epidural catheter, correct function of the device be verified by observing the flow rate in the microdrip chamber. We have used this method for the past year and found the equipment reliable, but in order to achieve more satisfactory analgesia the concentration of the infusion was increased initially to 0.375 per cent, and then reduced to 0.30 per cent. The records of the first 187 patients were reviewed retrospectively. Group I (n = 99) received an infusion of 0.25 per cent bupivacaine, Group II (n = 49) received 0.30 per cent and Group II (n = 39) received 0.375 per cent. Significantly more patients in Group I (30 per cent) required supplementary top-ups (in addition to the infusion) for the first stage of labour than in either Group II (10 per cent), or Group III (13 per cent). Top-ups for delivery were given to 55 per cent of patients in Group I, 64 per cent in Group II and 48 per cent in Group III. The incidence of motor block was significantly higher in Group III (21 per cent) than in either Group I (1 per cent) or Group II (2 per cent). For continuous epidural infusion at 6 ml/hr, 0.30 per cent bupivacaine combines optimum analgesia with minimal side-effects.