ABSTRACT. Group B streptococcal (GBS) sepsis produces arterial hypoxemia in newborns. In piglets we previously found that hypoxemia develops because of increased ventilation perfusion heterogeneity, and reduced mixed venous p 0 2 occurring in association with decreased pulmonary blood flow. We hypothesize that increased thromboxane A2 (TxA2) synthesis mediates the immediate alterations in gas exchange found in GBS sepsis. We studied 18 anesthetized, ventilated piglets before, during, and after a 30-min infusion of 2 x lo9 colony forming units/kg of GBS. Nine piglets were pretreated with 8 mg/ kg of dazmegrel (DAZ), a TxA2 synthetase inhibitor, and nine animals received GBS without DAZ pretreatment. Pulmonary and systemic arterial pressures, pulmonary vascular resistance, pulmonary blood flow, respiratory gas tensions, intrapulmonary shunt, and S D of pulmonary blood flow, an index of ventilation perfusion mismatching, were measured. Systemic and pulmonary arterial levels of thromboxane B2 and 6-keto-PGF,, were also measured. The sham-treated animals showed the expected rise in pulmonary arterial pressure from 12 f 3 to 29 + 7 torr, (p < 0.02). By comparison, the animals pretreated with DAZ did not demonstrate pulmonary arterial hypertension and had a delay in the fall in pulmonary blood flow until 2 h postinfusion. Arterial PO2 did not decline significantly after the GBS infusion in the DAZ-pretreated animals; the untreated animals showed a significant fall in p 0 2 from baseline. There was no significant change in intrapulmonary shunt or SD of pulmonary blood flow compared to baseline in the DAZ-pretreated animals. The elevation in thromboxane B2 occurring with GBS sepsis did not occur in the DAZ-pretreated animals. We conclude that TxA2 in part mediates the immediate gas exchange and pulmonary hemodynamic abnormalities during GBS sepsis. Inhibition of TxA2 synthetase results in preservation of normal pulmonary gas exchange and a delay in the fall in Q,following GBS infusion. (Pediatr Res 20: 481-486, 1986) Abbreviations GBS, group B streptococci Qs, systemic blood flow SDQ, SD of pulmonary blood flow TxB2, thromboxane B2 PG12, prostacyclin RIA, radioimmunoassay PGE,, prostaglandin El PGFI,, prostaglandin F,, PGE2, prostaglandin E2 DAZ, dazmegrel Hypoxemia develops during an intravenous infusion of GBS in experimental animals (1, 2), indicating a direct or indirect alteration in pulmonary gas exchange as a result of the bacterial sepsis. Mechanisms that might contribute to hypoxemia under these conditions include a reduction in mixed venous pOZ associated with reduced Qs, assuming unchanging tissue oxygen extraction and the presence of some degree of ventilation-perfusion mismatching, or an alteration in the distribution of Q,.Altered distribution of Q, may result in substantial perfusion of lung areas receiving no ventilation (shunt), orJung areas receiving little ventilation, i.e. areas with low VA/Q ratios. Both can contribute to hypoxemia depending on extent of diversion of Q, to these areas. We have sho...

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Blood pressure measurement using pulse oximeter waveform change was compared with an oscillometric measurement and the gold standard, intra-arterial measurement, in children after cardiac surgery. Forty six patients were enrolled and divided into groups according to weight. Simultaneous blood pressure measurements were obtained from the arterial catheter, the oscillometric device, and the pulse oximeter. Pulse oximeter measurements were obtained with a blood pressure cuV proximal to the oximeter probe. The blood pressure measurements from the pulse oximeter method correlated better with intra-arterial measurements than those from the oscillometric device (0.77-0.96 v 0.42-0.83). The absolute diVerences between the pulse oximeter and intra-arterial measurements were significantly smaller than between the oscillometric and intra-arterial measurements in children less than 15.0 kg. The pulse oximeter waveform change is an accurate and reliable way to measure blood pressure in children non-invasively, and is superior to the oscillometric method for small patients. (Arch Dis Child 1998;78:457-460)