COMMENT & CONTROVERSY

OPTIMIZING THE USE OF OXYTOCIN ON LABOR AND DELIVERY 

ROBERT L. BARBIERI, MD (EDITORIAL; JANUARY 2021) 

Vigilant labor progress aids in oxytocin optimization 

I read with particular interest Dr. Barbieri's editorial on optimizing oxytocin infusion. This topic is relevant for my practice as I am the kind of physician described and I usually get upset when the oxytocin is not managed as I ordered. 

In my opinion, several things need clarification. On our unit, the most significant point of controversy is the definition of tachysystole, mainly when we are using a tocodynamometer and not an internal transducer. 

I contend that it is quite challenging to ascertain the effectiveness of any given labor pattern based only on the number of contractions. Although we joke about "pit to distress," the truth is that contractions need to be "effective," which to me means strong enough to induce cervical changes. 

In my clinical practice, with a tocodynamometer, having 5 contractions that do not produce cervical changes (unless associated with abnormalities of the fetal heart rate tracing) is not a clinically relevant finding as we do not have a way to gauge the strength of such contractions. 

I usually employ a mid-range oxytocin protocol, starting at 4 mU per minute and increasing by 4 mU every 20 minutes. Through 30 years of practicing obstetrics, I have found that this protocol renders excellent results in achieving an efficient labor pattern without jeopardizing fetal well-being. 

On learning about oxytocin's pharmacokinetics, I still support Dr. Rhonda L. Perry and her colleagues' conclusion that, until we learn better about this aspect of oxytocin pharmacology, each woman is her own bioassay.¹ Furthermore, we see this in our daily practice: some patients go into full efficient labor with oxytocin at 4 mU per minute while others at 30 mU per minute do zilch. 

Based on the above, I think that optimization requires close vigilance of the labor and the fetal status at any given time, not determining an oxytocin rate of infusion or dosage. 
We should be observant on evaluating labor progress, and we should not hesitate to use internal pressure catheters when needed to obtain a more accurate evaluation of the labor pattern. 

By examining the patient's labor progress at regular intervals, we also optimize the oxytocin infusion by determining if the infusion is producing the expected cervical changes. 

Tomas Hernandez-Mejia, MD 

Pasco, Washington 

Reference
 
1. Perry RL, Satin AJ, Barth WH, et al. The pharmacokinetics of oxytocin as they apply to labor induction. Am J Obstet Gynecol. 1996;174:1590-1593. 

Dr. Barbieri responds 

I thank Dr. Tomas Hernandez-Mejia for sharing his expertise in utilizing a higher dose of oxytocin to optimize labor and birth. Dr. Hernandez-Mejia's view is supported by the recent publication of a high-quality clinical trial showing that a high-dose oxytocin protocol (initial and incremental rate of 6 mIU/min) did not cause an increase in adverse perinatal outcomes compared with a standard-dose protocol (initial and incremental rate of 2 mIU/min) but slightly shortened the duration of labor.¹ Based on this clinical trial, my conclusion is that the high-dose protocol, if appropriately monitored for excess uterine contractions and fetal heart rate pattern, is safe. 

Reference 

1. Son M, Roy A, Stetson BT, et al. High-dose compared with standard-dose oxytocin regimens to augment labor in nulliparous women: a randomized controlled trial. Obstet Gynecol. 2021;137:991-998. 

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