To the Editor:
We would like to congratulate Lee et al.1 on their excellent study, which challenged medical dogma and demonstrated that with appropriate management of the blood pressure during a spinal anesthetic for a cesarean delivery, left uterine displacement does not affect the acid-base status of the neonate. The study was well-designed and executed; however, we strongly disagree with the authors’ interpretation of the data such that “…findings do not support the historical practice and current recommendations for LUD [left uterine displacement] as being essential during elective cesarean delivery to support maternal hemodynamics, prevent spinal-induced maternal hypotension, and maintain neonatal acid–base status in healthy nonlaboring women with uncomplicated pregnancies.”1
Lee et al.1 found that the lack of left uterine displacement did not impact neonatal acid-base status; however, maternal hemodynamics were negatively affected in the group not receiving left uterine displacement. Maternal blood pressure and cardiac output were both significantly lower in the supine compared to left uterine displacement group, despite the supine group receiving 29% more phenylephrine.1 Therefore, rather than concluding that left uterine displacement is not necessary, the study actually demonstrates that left uterine displacement is beneficial and does improve maternal hemodynamics significantly.
In addition to the mean outcome differences between groups in the study cohort, it is critically important to consider the relatively rare, but serious adverse events that occur in some individuals after the induction of spinal anesthesia. The study was not adequately powered to detect the influence of the supine position on the incidence of events such as reflex bradycardia and cardiovascular collapse. Even in this small cohort, however, there were some women in whom the lack of left uterine displacement appeared to have a profound impact. One subject in the supine group had a clinically significant drop in blood pressure to 44/22 mmHg, and the lowest base excess was in the supine group. There was also the one patient in the left uterine displacement group who became symptomatic with a systolic blood pressure decrease from 122 to 75 mmHg while lying supine before her anesthetic. Supine hypotensive syndrome occurs in approximately 8% of women at term; and even if left uterine displacement does not benefit the entire study cohort, these individuals may benefit from left uterine displacement.2 Consistent with this concern, Lee et al. previously showed that although cardiac output only decreased 5% on average in the patients tilted less than 15° compared to when tilted at 15° or greater, cardiac output decreased by 20% in a subset of patients in the less tilted group.3
On the surface, the data from Lee et al.1 suggests that left uterine displacement may not be essential; however, a deeper look at their data demonstrates that left uterine displacement does have a positive effect on maternal hemodynamics, that a significant subset of patients are adversely affected when not tilted, and that we cannot predict which patients can safely be positioned supine. We, therefore, would strongly advocate for the continued use of left uterine displacement during cesarean delivery. The use of left uterine displacement should be considered for any pregnant woman in whom the uterus is palpable above the umbilicus.4 Left uterine displacement is a simple, cost-free intervention with proven efficacy, and the data from Lee et al.1 demonstrates the utility of this practice. If left uterine displacement distorts the anatomy enough to make surgery difficult, it can be reduced immediately prior to surgery, as most of the hemodynamic benefit of left uterine displacement is realized in the early post-spinal anesthesia period while surgical preparations are being made.
The authors declare no competing interests.