Anaesthesiological considerations on tocolytic and uterotonic therapy in obstetrics

Abstract

Aim: Significant side effects of tocolytic and uterotonic substances may be of concern to the anaesthesiologist. Recently, new drugs have been introduced having less side effects for both the mother and the neonate. Methods: A literature search was undertaken mainly focusing on meta-analyses, to review the possible side effects that might affect the course of anaesthesia and to suggest which precautions should be considered to prevent the occurrence of significant interactions with anaesthetic manipulations and drugs. Results: Magnesium sulphate has a proven benefit in lowering systolic blood pressure and preventing the occurrence of eclampsia, but not as a tocolytic. b-adrenergic agonists are being abandoned due to the availability of tocolytic agents causing less side effects. Calcium channel blockers (CCB) are frequently used but can cause major maternal cardiovascular complications. Nitroglycerin seems to be appreciated as an acute tocolytic rather than a routine substance during pre-term labour. Cyclo-oxygenase-2 inhibitors are still under investigation but their tocolytic benefit is questionable mainly due to foetal side effects. Atosiban is considered the first-choice tocolytic. With respect to oxytocic drugs, oxytocine, prostaglandines and methylergometrine may all cause serious side effects especially when combined. The cardiovascular side effects of prostaglandins and methylergometrine can be lifethreatening. Both oxytocin and carbetocin have a rather low risk for maternal complications. Conclusion: Atosiban and CCB are at least as effective tocolytic agents as b-mimetics but have significantly less side effects. Magnesium sulphate can cause neuromuscular blockade, especially when combined with CCB. Concerning oxytocic agents, short-acting oxyctocin and long-acting carbetocin have the least side effects as compared with prostaglandins and methylergometrine.

The use of uterotonic drugs during caesarean section

“…Preeclampsia remains a contraindication to its use, for reasons which are unclear. 41 The issue of receptor desensitisation is as yet unstudied, and further work on the efficacy of carbetocin is awaited.…”

What’s new in obstetric anesthesia?

“…Atosiban has similar efficacy to calcium channel blocking agents 86 and beta-mimetics, 87,88 and a significantly lower frequency of hypotension when compared with nifedipine, 86,89 and lower frequency of tachycardia, dyspnea, chest pain, pulmonary edema, hyperglycemia, hypocalcemia, rebound hyperkalemia, and fetal tachycardia when compared with betamimetics. [87][88][89][90] To date, no oxytocin antagonist has been approved by the US Food and Drug Administration. A meta-analysis of 58 randomized controlled trials of tocolysis concluded that prostaglandin inhibitors provide the greatest efficacy relative to side effects for delaying delivery at least 48 h and up to seven days, 84 however premature closure of the ductus arteriosus and oligohydramnios limit its use after 32 weeks of gestation.…”

Modern Views on Oxytocics in Obstetrics Practice

“…It is discouraged in pre-eclampsia, renal and liver disease. [2,9,13] Methyl-Ergometrine It is a powerful vasoconstrictor (Alpha-adrenergic receptor mediated) and also induces sustained uterine contraction. Because of the risk of hypertension (Pulmonary and systemic), coronary artery spasm and bronchospasm, it should not be used in pre-existing cardiopulmonary diseases, pre-eclampsia and concomitantly with other vasopressors.…”