Fibrinogen plasma concentration before delivery is not associated with postpartum haemorrhage: a prospective observational study.

BACKGROUND: Low plasma fibrinogen concentration has been linked to postpartum haemorrhage. The primary aim of this study was to assess whether fibrinogen concentration at admission before labour is associated with severe postpartum haemorrhage. Secondary aims were to describe fibrinogen concentration before and after labour and to identify predictors for severe postpartum haemorrhage. METHODS: 1951 healthy women were included in a prospective observational study. Fibrinogen concentration was determined at admission to the labour ward and in a subgroup of women (n=80) also after the placenta was delivered. Bleeding volume postpartum was estimated by weighing surgical sponges and pads and by measuring collected blood. Predictors for severe postpartum haemorrhage (>1000 ml) were identified with bivariate and multivariate regression analyses. RESULTS: Mean fibrinogen concentration was 5.3 (SD 0.8) g litre(-) (1). Median estimated blood loss was 450 (range 70-4400) ml and 250 (12.8%) women bled >1000 ml. Fibrinogen concentration was not correlated with postpartum haemorrhage in the entire cohort (r(s)=0.003, P=0.90) or in any subgroup. Fibrinogen concentration was not associated with bleeding >1000 ml (odds ratio 1.01 (CI 95% 0.85-1.19), P=0.93) and did not differ significantly before and after delivery. Oxytocin stimulation, instrumental delivery, Caesarean section and exploration of uterus were identified as independent predictors of haemorrhage >1000 ml. CONCLUSIONS: Fibrinogen plasma concentration at admission before labour does not predict severe postpartum haemorrhage in a general obstetric population. Fibrinogen concentration does not decrease significantly during normal labour. Excessive postpartum bleeding is mainly as a result of obstetric complications.

Respiratory effects of the kneeling prone position for low back surgery.

BACKGROUND AND OBJECTIVE: The kneeling prone position is often used for low back surgery in order to decrease intraoperative bleeding and increase the surgical exposure of the vertebral canal. The aim of this study was to assess effects of the kneeling prone position on respiratory gas exchange focusing on oxygen consumption and early changes in oxygenation. METHODS: Thirty ASA I-II patients scheduled for low back surgery in the kneeling prone position were studied. Anaesthesia was maintained with isoflurane, 1.2% end-tidal concentration. Respiratory gas exchange was measured with indirect calorimetry. RESULTS: When the patients were turned into the kneeling prone position their oxygenation was immediately improved--measured by arterial oxygen tension and arterial oxygen saturation. The oxygen uptake rate did not change from a baseline supine level of 76 mL min(-1) m(-2), but the carbon dioxide excretion rate decreased from a baseline supine value of 71 mL min(-1) m(-2) to 66 mL min(-1) m(-2) at 5 and 10 min after the kneeling prone position was adopted. Alveolar ventilation decreased in the kneeling prone position. CONCLUSIONS: The present study demonstrates that the kneeling prone position improves oxygenation and that the mechanisms involved are fast in onset. Furthermore, the prone position does not change oxygen consumption although alveolar ventilation is significantly reduced. The changes in alveolar ventilation could possibly be the result of circulatory changes caused by the prone position, but further studies are needed to clarify that hypothesis.

Effects of ephedrine on oxygen consumption and cardiac output.

Bolus doses of ephedrine are often used by anaesthesiologists for intraoperative hypotension. This randomized single-blind cross-over study was designed to simultaneously evaluate circulatory, respiratory and metabolic effects of intravenously given ephedrine in 12 healthy male volunteers. Oxygen uptake and carbon dioxide excretion were measured with indirect calorimetry and non-invasive transthoracic electrical bioimpedance was used for cardiac output measurements. The maximum effect on most variables was reached at 4-5 min. At 5 min after the administration of ephedrine 0.1 mg per kilogram body weight, there were significant increases in cardiac index, systolic and mean arterial blood pressure, expired minute volume, oxygen uptake and carbon dioxide excretion rates. There were no significant changes in the quotient between oxygen uptake rate and cardiac index, VO2/CI during the 30 min study period. The O2 saturation was not altered. The present study indicates that ephedrine increases oxygen demand and supply in a similar magnitude.