Profound hypotension and associated electrocardiographic changes during prolonged cord occlusion in the near term fetal sheep

Objective To determine whether the onset of fetal hypotension during profound asphyxia is reflected by alterations in the ratio between the T height, measured from the level of the PQ interval, and the QRS amplitude (T/QRS ratio) and ST waveform. Study design Chronically instrumented near-term fetal sheep received complete occlusion of the umbilical cord for either 8 (n = 6) or 15-min (n = 9). Results Cord occlusion led to sustained bradycardia and severe acidosis. Mean arterial blood pressure initially rose and then fell to a nadir of 32.6 ± 2.6 mm Hg in the 8-min group and 9.3 ± 1.0 mm Hg in the 15-min group ( P P Conclusion Elevation of the T/QRS ratio does not identify fetal hypotension during severe hypoxia, but abnormal waveforms in the recovery phase may indicate developing cardiac injury.