Volume 166 Number 1, Part 2

584 SHOULDER DYSTOCIA: RELATIONSHIP BETWEEN NEONATAL INJURIES AND ACID BASE STATUS. IA Hoskins, P Ehrlich,' SA Ordorica, BK Young, RF Porges,l Dept. Ob/Gyn, NYU Med. Ctr., New York, NY

Morbidity with shoulder dystocia (SD) may be due to delayed delivery and asphyxia. We reviewed 13,440 deliveries from 1/1/81 to 5/1/91 to identify SD and correlate severity of injuries with acid base status. There were 81 cases with complete followup in 67 (83%). Neonates were grouped according to severity of injuries. Group I (n=30, 45%) no injuries; group II (n=26, 39%) moderate injuries ego bruising, hypotonia; group III (n=ll, 16%) severe injuries ego fractures, palsy. Overall incidence of acidosis (pH < 7.20) was 43%. It was 81% in group II vS. 7% and 55% in groups I and III (p < 0.05). Of the 6 acidotic neonates in group III, 4 (67%) had palsy whereas 2 (33%) had isolated fractures, p < 0.05. Incidences of low (~3) Apgar scores were 7%, 19% and 18% in the 3 groups (NS). There was no correlation between severity of injury and meconium, seizures, hypotonia or apnea. Excessive, prolonged traction on the infant (causing hypotonia, palsy) was associated with neonatal acidosis whereas fractures appeared to expedite delivery and prevent acidosis.

585 FETAL DETERMINANTS OF ASSISTED VAGINAL DELIVERY, M,C, Williams. W,F, O'Brien, Department of Obstetrics and Gynecology. University of South Florida, Tampa, FL

Prior investigations of successful vaginal delivery have identified significant correlations with such factors as fetal weight and maternal pelvic dimensions, while the association with fetal asymmetry, as assessed by the ponderal index (birthweightl length3

). is unknown. Data were compared between 126 control vaginal deliveries, and successful assisted vaginal deliveries for cephalopelvic disproportion (72) and fetal distress (99). Chi-square goodness of fit comparisons between the control group and population norms found them similar for birthweight, crown-heel length. and ponderal index percent for gestational age, while head circumference percent among controls was slightly smaller than expected (mean 47%, P<0.05). The three groups were found similar for maternal height. weight, previous cesarean section, labor induction, meconium, gestational age, and birthweight. Ponderal index percent was significantly associated with assisted delivery (P < 0.004). Logistic regression for need for assisted vaginal delivery found previous successful vaginal delivery (R=0.23, P<O.OOOl), ponderal index % (R=0.16. P<O.OOl). and head circumference % (R =0.13, P<0.004) formed a model which correctly assigned 68% of cases with a non-significant model chi-square goodness of fit (P<0.42). Maternal height, weight, and history of previous cesarean were not significantly associated. Ponderal index % is correlated with assisted delivery.

NSVD CPO DISTRESS SIG. BIRTH WEIGHT % 48 51 42 NS HEAD CIRCUMF % 47 58 51 <0.04 PONDERAL lOX % 49 40 37 <0.004 UMB ARTERY pH 7.28 7.29 7.22 <0.0001 BASE DEFICIT 3.6 4.2 5.4 <0.0001

587

588

SPO Abstracts 431

INDIRECT SONOGRAPHIC GUIDANCE FOR EPIDURAl ANESTHESIA IN OBESE PREGNANT WOMEN DELNERED BY CESAREAN SECTION

D. Wallace, Y.D.'. L Gilstrap. U.D .• J. Currie. W.D.'. and R. Santos. U.D.' Departments of AntstI!esioiogy t Obstetrics/&jnec4logy. UT Southnstem. Dollas. IX

Obesity and edema Ihich obtculld lumbar landmarb resu~ed in technical difficulties and prolo~ our attempts to achieve epidural anesthesia. Holever. indirect sonographic guidance lith use of either the TOlhibo SAL -J28 or RT JOOO GE machine lith SmHz InInlducer (viluol field lidth 5.6 or 8cm) has aUoled UI to identify the midline by soagilal scan of the easily imaged laminae of lumbar vertobroe 2.3.4; to pAdict needie depth (ND) from uhound depth (UD. skin-to-Iamino distance); and knoling UD. the midline. and trunlducer centu lite marked Ihere positiOtied over the 2nd or Jrd interspace before its removal. pertutoneoully advance a 9.5 or 11.4cm Tuohy needle perpendicularly from the lite unbl epidurol puncture (EP). Ie prospectively studied J6 obese lomen scheduled for declive repeot CiS. ND las m_1Id by marker and m_re. and epidural anesthesia las successfully administered to aU patients. Simple finear regressiOti anolysis las performed. lith strong positive results (See figure).

Plot of 0bIIntd ValUII, RtpIIan lilt t m CanfIdencI lnhnaf on PrIcIcfId VafuII "'II ~ 10

00J II

t 8 • 7 c 6 .! 15 'i 4 ~ 3 ! , , !

Equation of fiat of btll fit ie Needl. depth = 0.211 t 1.017 X Ul1raeeund depth

p < 0.0001; R-Iquare = O.H , ! ! , [ ! , !

3 4 5 6 7 8 II 10 11 Ultra.ound Depth (om)

IHiIlCl lid COfttinuoII IGnlflPhic guidanCi studies. desipei to delenaine ff IOftO!'IPhy Iliuces cemp6C1tiou, Ire currutly beill! pllllned.

ADENOSINE INDUCES TACHYCARDIA AND LOWERS BLOOD PRESSURE IN THE PREGNANT EWE. Brian A. Mason. MD', Brian I. Koos, MD, DPhil. Dept. of Obstetrics and Gynecology, Nicholas S. Assali Perinatal Research Laboratory, UCLA School of Medicine, Los Angeles, CA 90024

Adenosine has recently been approved by the FDA for termination of paroxysmal supraventricular tachycardia (PSVT). Due to its very short half life, this purine nucleoside may be particularly useful in pregnant women with PSVT. Because adenosine can cause tachycardia and hypotension, the relative safety of this agent must be established before it can be recommended for general use in pregnancy. We therefore investigated the effects of graded intravenous infusions of adenosine in three chronically catheterized gravid ewes (>0.8 term). Infusions were increased in a stepwise manner from 25 to 400 /Lg/kg/min by doubling the infusion rate at five minute intervals. The same procedure was performed in reverse, beginning at 400 and decreasing to 25 /Lg/kg/min with results being similar in both cases. No significant changes occurred in mean pH, PC02 , or P02 •

Mean heart rate increased from 110 + 3.7 to 173 + 4.3 BPM (P < 0.(01) with statistically significant response -(P < 0.05) noted at infusion rates as low as 50 yg/kg/min. MAP decreased from 85.5 ± 3.4 to 79.4 ± 4.5 mmHg (P<O.OI). Conclusion: While the effects on MAP and HR are statistically significant, they probably pose no clinical risk to gravidas because the effects are within a range which is tolerated physiologically and are transient. Possible fetal effects of maternal adenosine infusions require further investigation. Supported by HD-18478.