Limitations of ST analysis in clinical practice: three cases of intrapartum metabolic acidosis.

OBJECTIVE To examine detailed intrapartum events in cases of neonatal metabolic acidosis despite monitoring using STAN (cardiotocography [CTG] plus ST waveform analysis of fetal electrocardiogram [ECG]). DESIGN Retrospective case review. SETTING High-risk pregnancies monitored by STAN. METHODS Case note review was performed in newborns with metabolic acidosis where no significant ST changes in the fetal ECG occurred prior to birth. MAIN OUTCOME MEASURES Metabolic acidosis. RESULTS Detailed review of three cases identified poor signal quality, difficulties in CTG interpretation, failure to comply with STAN clinical guidelines and deterioration of the CTG without ECG alert as the leading causes of these adverse outcomes. CONCLUSIONS The cases illustrate some of the pitfalls associated with the clinical application of the STAN technology which prevent severe metabolic acidosis being eradicated completely. It may be useful to expand the STAN guidelines protocol towards the identification of exceptional clinical situations, such as in our cases, and towards appropriate additional interventions, as this may lead to a further reduction in adverse neonatal outcomes.