Abstract
The aim of this study was to determine whether there is a relationship between changes in PR-RR correlation of the fetal ECG and progressive changes in fetal acid-base status and blood pressure (BP) during repeated umbilical occlusion. Chronically instrumented fetal sheep at 126.8 ± 0.6 d (mean± SEM) were randomized to receive 1 min of total umbilical cord occlusion either every 5 min for 4 h (1:5 group; n = 8), or every 2.5 min until BP fell <2.7 kPa (20 mm Hg) on two successive occlusions (1:2.5 group; n = 8). The PR-RR correlation was determined in 5- or 2.5-min intervals. Umbilical cord occlusion caused variable decelerations with initial sustained hypertension. In the 1:5 group BP remained elevated throughout, and there was little change in acid-base status (pH = 7.34 ± 0.07, base deficit = 1.3 ± 3.9 after 4 h). In contrast, after the third occlusion the 1:2.5 group showed progressive hypotension during occlusions, and severe progressive metabolic acidemia (pH 6.92 ± 0.1, base deficit 17.0 ± 4.7 mmol/L after the last occlusion). In both groups, the PR-RR relationship switched from positive to negative with the onset of occlusions, then reverted to positive after a variable interval. In the 1:2.5 group later reversion of the PR-RR to positive was associated with earlier and more prolonged hypotension during the middle and end of the occlusion series (p < 0.001). We conclude that the initial switch to a negative PR-RR relationship during repetitive umbilical occlusion was due to a reflex-mediated response unrelated to fetal acidosis or hypotension. Both stable well compensated fetuses and severely hypoxic, hypotensive fetuses subsequently showed a positive PR-RR correlation.
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Abbreviations
- BD :
-
base deficit
- MAP :
-
mean arterial blood pressure
- MWU :
-
Mann-Whitney U test
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Supported by the Health Research Council of New Zealand, the Auckland Medical Research Foundation, the New Zealand Lotteries Board, and U.S. Public Health Service Grant RO1-HD-32752.
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Westgate, J., Gunn, A., Bennet, L. et al. Do Fetal Electrocardiogram PR-RR Changes Reflect Progressive Asphyxia after Repeated Umbilical Cord Occlusion in Fetal Sheep?. Pediatr Res 44, 297–303 (1998). https://doi.org/10.1203/00006450-199809000-00006
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DOI: https://doi.org/10.1203/00006450-199809000-00006
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