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A4082
October 14, 2014
3:00 PM - 4:30 PM
Room Room 244
Effect of Vitamin D Levels on Intrapartum Epidural Consumption
Steven Ropers, M.D., Quy Tran, M.D., Andrew W. Geller, M.D., Amy Lamb, M.S.N., C.N.M., Ph.D., Calvin Hobel, M.D., Mark I. Zakowski, M.D.
Cedars-Sinai Medical Center, Los Angeles, California, United States
Introduction:

Vitamin D plays a vital role in many important physiologic functions, and its deficiency has been linked to both depression [1] and pain.[2] An estimated 41 % of pregnant women in the United States have deficient vitamin D levels, with an additional 41% having insufficient levels.[3] The American Congress of Obstetrics and Gynecology recommends vitamin D supplementation during pregnancy when deficiency is identified for maternal and fetal bone metabolism.[4] Currently no studies have established a link between low vitamin D levels and intrapartum pain. We hypothesized that parturients with lower vitamin D levels will have increased intrapartum pain.

Methods:

After IRB approval, pregnant women >18 years old were enrolled on routine OB visits at <25 weeks gestational age as part of a nested cohort of a larger study assessing vitamin D and depression. Patients admitted to labor and delivery in spontaneous labor or for labor induction had vitamin D levels measured at time of delivery. At our hospital, labor analgesia is obtained using ropivacaine 0.2% infusion without narcotic. Epidural analgesic consumption was quantified as area under the curve (AUC) and converted into ropivacaine equivalents per hour to normalize for duration of epidural infusion.[5] The AUC and narcotic consumption were compared in the high and low (above and below median) vitamin D levels and the two groups were compared using an unpaired t-test.

Results:

At the time of writing, serum vitamin D results (N=93) have been analyzed, but scheduled cesareans (N=22) were excluded from analysis. Demographics were similar for each group except the lower vitamin D group had a statistically significant higher BMI 31.7 ±5.7 vs 29 ± 4.0 kg/m2 (P=0.03). Mean vitamin D levels were 25.84 ±6.3 ng/ml for the low vitamin D group and 43.1 ± 5.9 ng/ml for the high vitamin D group. The lower vitamin D group had a significantly higher epidural ropivacaine equivalents per hour than those in the higher vitamin D group, 18.25±14.3mg and 12.4±8.8mg, respectively (p=0.046).

Conclusion:

Our study is the first to demonstrate that lower vitamin D levels are associated with higher intrapartum epidural consumption. This finding is consistent with emerging research associating hypovitaminosis D with pain. Vitamin D is thought to activate descending inhibitory and modulatory pain pathways.[6] However, one hypothesis proposes that once ascending pain pathways are activated, simple vitamin D repletion may not be enough to silence those pathways.[7] Thus the mechanisms underlying the association between hypovitaminosis D intrapartum and intrapartum pain as well as potentially postpartum pain warrant further investigation. Given the high prevalence of vitamin D deficiency and insufficiency in US parturients, effective prevention and treatment may have significant impact on decreasing labor pain in millions of women every year. Recommendations regarding vitamin D supplementation during pregnancy may need to be revisited. We conclude that vitamin D deficiency is an important risk factor for increased intrapartum pain.

References:

1) Br J Psychiatry. 2013 Feb;202:100-7

2) Ann Rheum Dis. 2009 Jun;68(6):817-22

3) Am J Perinatol 2011; 28:7-12

4) ACOG Committee Opinion 495, 2011.

5) Br J Anaesth. 1999 Mar;82(3):371-3.

6) J Bone Miner Res 2008;23:S223

7) Letters to the Editor / PAIN 143 (2009) 159-160

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