Thomas Spillman

Barorefiex function in normal pregnancy

The sinoaortic baroreflex is one of the primary mechanisms that regulates blood pressure. Decreased baroreflex sensitivity has been reported in preeclampsia. We sought to determine whether pregnancy altered baroreflex sensitivity. From a radial artery catheter, heart rate and mean arterial pressure were recorded continuously onto a polygraph. The ratio of change in heart rate produced per unit of change in mean arterial pressure was calculated as an index of baroreflex sensitivity. Mean arterial pressure responses to incremental infusions of phenylephrine (0.4 to 2.0 micrograms/kg/min) were measured in the same patients at term (n = 9, 38.0 +/- 0.3 weeks) and again 6 to 8 weeks postpartum (n = 7). The results indicated (1) higher baroreflex sensitivity in pregnancy than in the postpartum period (0.9 vs 0.5 beats/min/mm Hg) (p less than 0.007); (2) attenuated vascular responsiveness to alpha-adrenergic stimulation in pregnancy (p less than 0.05); (3) a relationship between vascular responsiveness and baroreflex sensitivity. We conclude that pregnancy is associated with an increase in baroreflex sensitivity and that the attenuated response to phenylephrine is, at least in part, a result of increased baroreflex sensitivity.

Intrapartum to postpartum changes in colloid osmotic pressure

A study was undertaken to determine the effect of route of delivery on plasma colloid osmotic pressure. Plasma colloid osmotic pressure was measured on admission to the hospital and 8 to 24 hours post partum in 72 patients at term with uncomplicated prenatal histories. Thirty-six patients underwent uncomplicated vaginal deliveries (local anesthesia, 18; conduction anesthesia, 18) and 36 patients had cesarean sections (conduction anesthesia, 18; general anesthesia, 18). The mean (+/- SD) intrapartum colloid osmotic pressure of the overall group was 21.0 +/- 2.1 mm Hg, and it declined significantly (p less than 0.01) to 15.4 +/- 2.1 mm Hg post partum. A comparison of the intrapartum and postpartum reductions in colloid osmotic pressure between patients who underwent vaginal delivery and those who underwent cesarean section revealed no significant differences. Furthermore, the mean reductions in colloid osmotic pressure when all four groups were compared by type of anesthesia were not significantly different. Fifteen patients (20.8%) in the study had a postpartum colloid osmotic pressure of less than 13.6 mm Hg, and five (6.9%) had a postpartum colloid pressure of less than 12.5 mm Hg. Our results indicate that, for normal pregnancy, colloid osmotic pressure is uniformly lowered in the post partum and, in some cases, to levels that have been reported to be dangerously low.

Maternal respiration and blood gases during aerobic exercise performed at moderate altitude

We studied whether maternal acid-base status during aerobic exercise performed at moderate altitude is affected by pregnancy. Seven primiparus women were tested at 37 wk gestation and 12 wk postpartum. Subjects were studied at rest, and during two cycle (50 W, 75 W) and two treadmill (67 m.min-1; 2.5% grade, 67 m.min-1; 12% grade) protocols. Exercise bouts lasted 6 min with a 10-min rest between sessions. Minute (VE) and alveolar (VA) ventilation, tidal volume (VT), and ventilatory equivalent for carbon dioxide (VE/VCO2) were significantly (P less than 0.01) greater when exercise was performed during pregnancy. Physiological dead space (VD) was not affected by pregnancy status and did not differ between rest and exercise. Decreases (P less than 0.01) in arterial pH during exercise averaged 0.04 units in both pregnancy and postpartum. Despite similar change in maternal pH, carbon dioxide tension (PaCO2) remained unchanged during exercise at 37 wk gestation but decreased at 12 wk postpartum. Decreases in arterial bicarbonate [HCO3-] associated with exercise were smaller during pregnancy. Our findings indicate that pregnancy did not compromise maternal acid-base status during aerobic exercise.

Monoclonal antibody-based immunoenzymetric assays for quantification of human igg and its four subclasses

A panel of 5 immunoenzymetric assays (IEMAs) has been developed for quantification of the total and four subclasses of immunoglobulin G (IgG) in human serum using IUIS/WHO documented monoclonal antibodies (MoAb). Human IgG specific MoAb was adsorbed to microtiter plates and used to capture IgG from serum. Peroxidase conjugated forms of polyclonal mouse anti-human IgG Fc or a mixture of 4 MoAb (anti-kappa, anti-lambda, anti-IgG Fc PAN and anti-IgG Fd PAN) were used as detection antibodies. Use of monoclonal antibody in chromatographically purified form was required for acceptable assay sensitivity (S) and working ranges (WR). All 5 IEMAs displayed good precision (intra-assay %CV less than 5%, inter-assay %CV less than 12%) and parallelism (inter-dilutional CV less than 20%). Both HP6069 or HP6070 (anti-IgG1 Fc) worked well alone or together as capture antibodies in the IgG1 IEMA: WR = 20-1250 ng/ml, S = 15 ng/ml. HP6002 (anti-gG2 Fc) alone or in combination with HP6014 (anti-IgG2 Fd) produced an IgG2 IEMA with a WR of 5-200 ng/ml and S of 5 ng/ml. HP6047 (anti-IgG3 hinge) alone generated a sensitive IgG3 IEMA with a narrow working range: WR = 2-50 ng/ml, S = 1.6 ng/ml. Both HP6025 and HP6023 (anti-IgG4 Fc) worked equally well alone and together to produce a useful IgG4 IEMA: WR = 8-250 ng/ml, S = 7.8 ng/ml. HP6017 (anti-IgG PAN Fc) was combined in an equal molar ratio with HP6046 (anti-IgG PAN Fd) to produce a total IgG PAN IEMA with a WR of 5-530 ng/ml and a sensitivity of 5 ng/ml. All 5 IEMAs fulfilled requirements for robust clinical immunoassays that permit the quantitation of human IgG and its 4 subclasses.

Peripartum colloid osmotic pressure changes: Effects of controlled fluid management

A prospective, fluid-controlled study of serially measured colloid osmotic pressure changes in the peripartum period was undertaken. Seventeen patients with uncomplicated pregnancies undergoing elective cesarean section at term were administered a predelivery bolus of 15 ml/kg of lactated Ringers solution prior to operation. Maintenance crystalloid fluids were infused at 125 to 150 ml/hr both intraoperatively and post partum without the addition of blood or other colloid solutions. Serial colloid osmotic pressure measurements were obtained before hydration, after hydration, after delivery, and at 6 and 24 hours post partum. The results demonstrated a 15.9% decline in colloid osmotic pressure immediately following the hydration bolus (20.7 +/- 1.5 to 17.4 +/- 1.8 mm Hg) (p less than 0.01). A further decline in colloid osmotic pressure to 16.6 +/- 1.7 mm Hg occurred after delivery and represented an overall 22% decrease from the baseline value (p less than 0.05). The lowest mean colloid osmotic pressure value occurred at 6 hours post partum (16.1 +/- 1.1 mm Hg). These data support previous observations that colloid osmotic pressure is uniformly lowered in the immediate postpartum period with peak reductions identified at 6 hours following delivery. In addition, intravenous crystalloid administration during the peripartum interval can substantially influence this decline in colloid osmotic pressure. Although no clinical evidence of cardiopulmonary compromise was observed in this set of normal gravid women, these data may be useful in the management of the parturient patient with established risk factors for pulmonary edema where alterations in the pulmonary capillary wedge pressure-colloid osmotic pressure gradient have been shown to correlate with the development of this complication.

Effect of blood contamination on lecithin to sphingomyelin ratio in amniotic fluid by different detection methods

Amniotic phospholipid detection methods such as cupric acetate measure unsaturated lecithin whereas others such as phosphomolybdate detect both unsaturated and saturated lecithin. Because of the extreme unsaturation in serum and red blood cell lecithin, we compared lecithin (L) and sphingomyelin (S) content of maternal blood as well as the effect of blood contamination on amniotic fluid L/S ratios. L/S ratios were obtained by thin-layer chromatography utilizing both cupric acetate and phosphomolybdate for phospholipid detection. The L/S value (mean +/- SD) of maternal serum obtained by cupric acetate was 1.90 +/- 0.19 and that for phosphomolybdate 1.78 +/- 0.17. The results of increasing serum concentrations in amniotic fluid prior to analysis suggest that as little as 0.5% contamination alter results and by 2% contamination values approach the L/S ratio of actual serum whether the amniotic fluid was initially mature or immature by either method. The serum L/S ratio by cupric acetate equaled its maturity threshold of 2.0 while the serum L/S ratio by phosphomolybdate was below its threshold of 3.0. Whereas both methods would have falsely immature values in the presence of blood only phosphomolybdate would assure against false maturity.

Effect of differences in saturation sensitivity of phospholipid stains on clinical predictivity of L/S ratios

Owing to the importance of the degree of fatty acid side chain saturation in the ability of lecithin molecules to function as surfactant, we assessed the clinical effectiveness of analytical methods which differ with respect to methodologic influences by saturated and unsaturated phospholipids. The lecithin/sphingomyelin ratios, determined with either cupric acetate or phosphomolybdate as the detection reagent, are compared for their abilities to predict respiratory distress syndrome (RDS), transient tachypnea (TTN), or the absence of respiratory difficulty in neonates. A group of 47 amniotic fluids were analyzed from 25 non-problem cases, 13 cases of TTN and 9 cases of RDS. Receiver operating characteristic analysis shows that in our sample population, the measurement of total lecithin for the prediction of neonatal respiratory distress failed to demonstrate an advantage over the measurement of unsaturated lecithin alone.