Carsten Nickelsen

Continuous acid-base assessment of the human fetus during labour by tissue pH and transcutaneous carbon dioxide monitoring.

Summary. Simultaneous monitoring of fetal tissue pH (t‐pH) and transcutaneous carbon dioxide (Tc‐Pco2) was performed in 30 labours. Both t‐pH and Te‐Pco‐2 at delivery were positively correlated with pH (r= 0·69) and Pco2(r= 0·68) of the umbilical artery blood. A tissue/transcutaneous standard base excess (t‐SBE) was derived from the t‐pH and the Tc‐Pco2 and calculated for 13 fetuses a t delivery; there was a correlation with standard base excess of umbilical artery blood. An analysis of t‐pH and Tc‐Pco2 changes during the last hour of labour revealed that only infants who were born with decreased pH of the umbilical artery blood had decreasing t‐SBE, while all others had a constant t‐SBE.

Peripartum hysterectomy in Denmark 1995–2004

Background. Severe postpartum hemorrhage (PPH) is a potentially life‐threatening situation that sometimes requires a hysterectomy. We examined the national incidence, risk factors, indications, outcomes and complications of peripartum hysterectomy following vaginal and caesarean delivery. Methods. Peripartum hysterectomy was defined as a hysterectomy after birth until 1 month after delivery using the codes for hysterectomy from the NOMESCO classification (1995). National data from the period 1995–2004 were extracted from the Danish Medical Birth Register and linked to the Danish National Hospital Register followed by registration of relevant data from the medical records of all the patients. Results. We found 152 hysterectomies corresponding to an incidence of 0.24/1,000 deliveries. The risk of peripartum hysterectomy increased 11‐fold following caesarean compared to vaginal delivery. Placenta accrete was present in 37% of the cases and 68%. Conclusion. Peripartum hysterectomy has increased significantly during the last 20 years. Optimizing treatment of PPH may decrease the incidence of peripartum hysterectomy in the future.

Acid-base evaluation of umbilical cord blood: relation to delivery mode and Apgar scores

Acid-base status of umbilical artery and vein blood was measured immediately after delivery in 300 cases. A slight acidosis of mixed respiratory/metabolic type was found in newborns delivered following a second stage of 10-30 min duration. After a second stage of more than 30 min the metabolic contribution to the acidosis was predominating. With Apgar scores lower than 10 the pH was found to decrease and carbon dioxide tension to increase. Induction or augmentation of labor by oxytocin did not influence the acid-base status of umbilical cord blood. Delivery by vacuum extraction or low forceps resulted in lower pH and higher carbon dioxide tension in umbilical cord blood, but the changes were associated with the indication for instrumental delivery and not with mode of delivery. A large arterio-venous difference between the acid-base parameters was usually connected to vigorous newborns and a small difference to depressed infants. The carbon dioxide tension was usually increased in newborns with decreased pH, and a close correlation between these parameter was found. No case of acidosis (pH below 7.15) was found in this population at carbon dioxide tensions below 7.2 kPa; at higher Pco2 values only 25% of the newborns were acidotic. A Pco2 level of 7.7 kPa might be used at transcutaneous carbon dioxide monitoring during labor, although the sensitivity and specificity of this parameter will have to be decided in a prospective study.

The current status of intrapartum continuous fetal tissue pH measurements.

Continuous tissue pH monitoring during labor has now been possible for 15 years. Tissue pH is measured in the intercellular fluid, and the value differs in some cases from the blood pH value because of local capillary flow and local metabolism. The fetal scalp seems to be an area where tissue pH and capillary blood pH values are very close, but in acute acidosis there may be a time lag of 10-15 min before tissue pH is equilibrated. Normal values of scalp tissue pH are 7.38 in early labor declining by 0.016 per hour during the first stage of labor and by 0.12 per hour during the second stage of labor. Tissue pH values below 7.15 are defined as pathological. The correlation coefficient to umbilical artery blood pH (0.71), success rate (67%) and electrode drift (below 0.04) from the largest study of tissue pH monitoring using glass pH electrodes (n = 337) are described.

Computer assessment of the intrapartum cardiotocogram. II: The value of computer assessment compared with visual assessment

The chief aim of our work has been to create a computer Cardiotocographic Assessment System (CAS) and thus eliminate the intra‐ and inter‐observer variability of the visual assessment of the cardiotocogram (CTG), and to improve the assessment of the CTGs to the standard of the most experienced obstetricians. The purpose of this paper is to present the accuracy of the prediction of fetal outcome obtained by the CAS and to compare it with 4 experienced obstetricians’ accuracy. Fifty CTGs from the last 30 min. of labor were assessed as normal or pathological by the computer and by the obstetricians. The condition of the newborn was evaluated from the one‐minute Apgar score, the umbilical artery pH and standard base excess, and the need for resuscitation.

Fetal transcutaneous carbon dioxide monitoring – the effect of different fixation methods

Summary. Fetal transcutaneous carbon dioxide tension (tc‐Pco2) was monitored simultaneously by two electrodes fixed with glue or suction during 10 deliveries. There were no differences in success rate, tc‐Pco2 readings or stabilization time between the two fixation methods, but the glue fixation method was more time consuming, caused more discomfort to the patient and generally did not permit reapplication of the electrode.

Fetal and maternal transcutaneous Pco2 levels during labour and the influence of epidural analgesia

The Departments of Obstetrics and Gynaecology of the Hvidovre University of Copenhagen and the Free University of Amsterdam collaborated in a study on the relationship of maternal and fetal acid-base state in the intrapartum period. Transcutaneous PCO2 levels of mother (tcPCO2m) and fetus (tcPCO2f) were continuously recorded in 52 patients during labour. TcPCO2f and tcPCO2m correlated significantly (r = 0.42, P < 0.002). During the first stage of labour, a rather stable level was found for tcPCO2f (7.7 +/- 1.6 kPa) and tcPCO2m (4.4 +/- 0.8 kPa). TcPCO2m decreased significantly to 3.8 +/- 0.7 kPa (P < 0.01) in the hour before full cervical dilatation, probably due to maternal hyperventilation as a reaction to painful uterine contractions. TcPCO2f likewise showed a tendency to a decrease to a mean value of 7.4 +/- 1.5 kPa. In eight cases epidural analgesia was applied because of painful uterine contractions. Prior to the epidural analgesia, tcPCO2m (3.8 +/- 0.8 kPa) and tcPCO2f (6.7 +/- 1.7 KPa) were significantly lower in this subgroup compared to the total population. After pain relief by application of epidural analgesia, tcPCO2m and tcPCO2f returned to the population mean.

Fetal carbon dioxide tension during human labour.

Fetal carbon dioxide tension during labour is elevated in both metabolic and respiratory acidosis, but intermittent fetal blood analyses often fail to detect PCO2 changes during acute complications. Transcutaneous carbon dioxide monitoring is continuous and the possibility of diagnosing PCO2 changes is therefore better. The theoretical background for transcutaneous measurements and methods for clinical monitoring are described. Close correlations with capillary and arterial blood values have been found, and the atraumatic principle with a simple electrode application indicates a promising new method for acid-base assessment during human labour.

Predictive value of pelvic scores for induction of labor by local PGE2

The predictive value of pelvic scores, parity, age and gestational age for induction of labor by local prostaglandin-E2 (PGE2) was examined in 336 women attempting induction of labor by intracervical or vaginal PGE2. The patient characteristics were correlated to: (1) vaginal delivery within 48 h, (2) the period from induction to onset of labor (latency period), and (3) the duration of labor. The Bishop score (P < 0.01) and even more the Lange score (P < 0.0001) were significantly inversely correlated to both latency period and induction-delivery period. This was caused by cervical dilatation (P < 0.001), fetal station (P < 0.05) and cervical length (P < 0.05), whereas position and consistency of the cervix were of no importance. All three periods studied were significantly (P < 0.0001) shorter in parous women. In primiparous women, gestational age was of no importance for the latency period; however, higher gestational age was associated with longer labor (P < 0.001). We conclude that the predictive value of pelvic scores on induction hardly differs using local PGE2 compared to conventional methods; furthermore, the Bishop score should be substituted, disregarding position and consistency of the cervix, but putting more weight to cervical dilatation. A new pelvic score is proposed.

Computer Assessment of the Intrapartum Cardiotocogram

To solve the problem of low predictive values in the visual assessment of the CTG, several computer programs have been designed. Only a few of those programs describe the CTG automatically and thus consistently. The aim of this study was to construct a diagnostic procedure for computer‐aided automatic assessment of the CTG. A computer program quantified 17 variables of the CTG. Within a window of user‐defined length, a second program calculated the number of measurements, the mean, the trend, and the coefficient of variation of each of the 17 variables, and produced a total of 56 distinct subvariables. A discriminant procedure was set up which could use any number and combination of the 56 subvariables to calculate the probability of a CTG derived from a compromised infant. The diagnostic procedure was optimized by “direct forward search” for the combination of subvariables discriminating best between normal and compromised infants. Using the last half hour of the first stage of labor, 50 CTGs entered the optimizing procedure. A combination of nine subvariables was found. In a separate paper its performance is compared with that of clinicians.