Transplacental Neonatal Transfer of Lidocaine During Urgent Caesarean Delivery (Lidocaine TNT)

The Lidocaine TNT study was a prospective observational pharmacokinetic cohort study conducted in two tertiary maternity units of the Hospices Civils de Lyon, France.

Women undergoing Lucas category 1 cesarean delivery, defined by an immediate threat to the life of the woman or fetus, or Lucas category 3 cesarean delivery, defined by the need for early delivery without immediate maternal or fetal compromise, were eligible when surgical anesthesia was obtained by extending a pre-existing labor epidural catheter with 2% lidocaine and epinephrine.

The urgency category was assigned by the attending obstetric team before delivery. In the local color-code system, Lucas category 1 corresponded to red-code cesarean delivery, with a target decision-to-delivery interval below 15 minutes, and Lucas category 3 corresponded to green-code cesarean delivery, with a target interval below 60 minutes.

Epidural extension was performed according to routine clinical practice using lidocaine 2% with epinephrine 1:200,000. The lidocaine dose, timing of administration, use of adjuncts, and need for additional anesthetic supplementation were determined by the attending anesthesia team and were not assigned by the study protocol.

Paired umbilical arterial and venous blood samples were collected immediately after delivery in blood-gas syringes containing dry heparin. After routine blood-gas analysis, residual plasma was stored and subsequently analyzed using liquid chromatography-tandem mass spectrometry.

The primary objective was to compare umbilical arterial and venous plasma lidocaine concentrations between Lucas category 1 and category 3 cesarean deliveries. Secondary objectives were to examine the associations between umbilical pH and the corresponding lidocaine concentrations and to assess whether the relationship between arterial pH and arterial lidocaine concentration differed according to cesarean urgency category.

Arterial and venous lidocaine concentrations were analyzed separately after natural-log transformation. Bayesian Gaussian linear regression models included Lucas category, the corresponding umbilical pH, birth weight, gestational age, and maternal epidural lidocaine dose. A secondary model included an interaction between Lucas category and umbilical arterial pH. Complete-case analyses were performed without imputation of missing data.