The influence of epinephrine on uterine contractility

Abstract. Pudendal block with 20 ml of 1 per cent lidocaine (200 mg) with and without epinephrine was used in 24 patients for pain relief during the second stage of labour. The addition of epinephrine improved the quality and prolonged the duration of the anasthe‐sia. Measurable amounts of lidocaine were detected in maternal venous And foetal scalp blood within 5 minutes after the injection with peak levels within 10‐20 minutes. Lidocaine with epinephrine gave lower maternal and foetal levels than plain lidocaine. The peak levels were about 30 per cent lower in maternal and about 20 per cent lower in foetal blood when epinephrine was added to the solution injected. The lidocaine levels in foetal blood were lower than the corresponding concentrations in maternal blood. They were always far below levels reported to be toxic. No correlation existed between maternal or foetal blood lidocaine concentrations and acid‐base changes in maternal or foetal blood. A slight but transient decline in the uterine activity was sometimes observed. This tendency was more pronounced when lidocaine with epinephrine was used. The mean duration of the second stage was longer in the anaesthetized patients than in a control group, probably more due to the abolishment of the bearing down reflex than to the slightly affected uterine activity. A prolongation of the second stage of labour was found to give a significantly increased tendency to foetal aci‐dosis in the anaesthetized as well as in the control group. The one minute Apgar scores were, however, normal. Adverse effects on the foetus due to a second stage prolonged by pudenda] block may be minimized by liberal use of episotomy, proper instruction, and coaching.

Section: Discussionsupporting

confidence: 92%

“…Epinephrine has also been reported to interfere with the pattern of uterine contractility (22,28). Intravenous infusion of epinephrine in excess of 4-5 mcg/min is reported to be accompanied by prompt depression of the intensity of spontaneous or induced uterine contractions.…”

Section: Discussionmentioning

confidence: 99%

Pudendal Block in Normal Vaginal Deliveries

Zador

Lindmark

Nilsson

1974

“…pattern, it does not seem to exhibit any unfavourable effect on foetal heart rate pattern. This is in agreement with results from a study in which epinephrine was reported to give no changes in the foetal heart rate (21). Foetal acid-base studies have gained increasing interest since the method of micro-sampling was introduced by Saling (17).…”

Section: Conflicting Opinions Have Been Expressed Aboutsupporting

confidence: 88%

Low Dose Intermittent Epidural Anaesthesia with Lidocaine for Vaginal Delivery

Zador¹,

Englesson²,

Nilsson³

1974

Abstracr.In 190 women with uncomplicated pregnancies, intermittent epidural analgesia was given by means of injections of about 50 mg lidocaine without ( Series I), or with epinephrine 1 :200,000 (series 11) at one hour intervals during the first stage of labour. During the second stage the analgesia was maintained by 100 mg of lidocaine at an average interval of one hour. The mean total dose of lidocaine administered in series I was 409 mg, and 258 mg in series 11. The degree of pain relief in series I1 was most satisfactory according to results obtained by a specially designed scoring system. In series I the method was

“…An alternate one is that the uterine pattern, it does not seem to exhibit any unfavourable effect on foetal heart rate pattern. This is in agreement with results from a study in which epinephrine was reported to give no changes in the foetal heart rate (21). Foetal acid-base studies have gained increasing interest since the method of micro-sampling was introduced by Saling (17).…”

Section: Cord Bloodsupporting

confidence: 76%

Low Dose Intermittent Epidural Anaesthesia with Lidocaine for Vaginal Delivery II

Zador

Nilsson

1974

A bsfruci. Intermittent lumbar epidural block, using lidocaine without (series I), or with epinephrine (series II), for pain relief in.labour was carried out in a total of 190 women with uncomplicated pregnancies. In a number of randomly selected cases in these two series the uterine contractility, the foetal heart rate pattern, and the acid-base balance of the mothers and their foetuses were studied. Transitory decrease in uterine activity, primarily due to depressed intensity of the contractions, was observed after each injection in both series. This phenomenon was, however, much more pronounced in cases where epinephrine was added to the local anaesthetic solution. In both series the effect on the contractions declined with the number of injections. Ominous foetal heart rate patterns were rare and occurred almost exclusively in association with transient maternal hypotension. Good correlation was found between maternal arterial, and arterialized capillary blood with respect to the acid-base components. The acid-base values in foetal scalp blood, maternal capillary blood, and in umbilical cord blood showed a less pronounced tendency to metabolic acidosis in cases where epidural blocks were given than in cases in a non-anaesthetized control group. Prolongation of the second stage was accompanied by the development of metabolic acidosis in anaesthetized, as well as in nonanaesthetized cases. In the epidural series, however, this acidosis tended to appear later and to develop more slowly, indicating an overall good and stable intrauterine foetal condition. In a previous publication by the authors (24) a low dose regimen for lumbar epidural anaesthesia during labour and delivery was evaluated regarding analgetic effect, maternal and foetal blood levels of lidocaine with special reference to the risk of accumulation of the local anaesthetic agent. It was concluded that adequate analgesia could be obtained with hourly injections of 10 ml of 0.5 per cent lidocaine with epinephrine 1:200,000 during the first stage of labour, and with 10 ml doses of 1 per cent lidocaine with epinephrine 1 :200,000 hourly during the second stage. The maternal, foetal and cord blood levels of lidocaine were low, and the risk of accumulation of the drug to the proximity of assumed toxic levels was found to be minimal. When the same lidocaine dose schedule without added epinephrine was tried, the analgesia was often inadequate, maternal and neonatal blood lidocaine levels higher, and the risk of accumulation more evident. It was observed that the mean duration of labour among primiparous women was significantly longer in cases receiving epidural blocks than in a randomly selected group of control patients who had not received regional anaesthesia.Changes in foetal heart rate patterns, decrease in foetal pH, and metabolic acidosis in the neonatal period have been described in connection with lumbar epidural anaesthesia (6,13,19,26). A reduction of the normal beat to beat variations in foetal heart rate recordings which is sometimes observed ...