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Biomedical subjects

S M Shnider

Publications and source records attributed to S M Shnider.

At least 55 records · Page 3Linked to original sources
PubMed1978

Placental transfer of lidocaine: effects of fetal acidosis.

To investigate whether fetal acidosis increases the placental transfer of lidocaine, resulting in higher fetal blood levels of the drug, lidocaine was infused intravenously into ten pregnant ewes to maintain plasma levels of 2-4 microgram/ml. After maternal-fetal equilibrium was reached, the fetus was made acidotic by infusing lactic acid intravenously. Fetal blood pH decreased from 7.35 to 7.10. With fetal acidemia, fetal blood lidocaine levels increased significantly from 1.60 +/- 0.11 microgram/ml to 2.72 +/- 0.26 microgram/ml. The fetal-maternal lidocaine ratio increased from 0.76 to 1.21. Correction of the acidosis by bicarbonate infusion returned the fetal-maternal ratios to control values. It is concluded that acidosis in the fetus may result in trapping of ionized lidocaine in the fetal circulation and increase the transfer of lidocaine across the placenta.

Acidosis↗
PubMed1978

Dopamine administration in the normotensive pregnant ewe.

Dopamine was administered to pregnant ewes at randomly selected rates of 1, 3, 5, 10, 20, 30, or 40 microgram/kg/min. Doses less than 10 microgram/kg/min produced no significant change in maternal areterial blood pressure, cardiac output, or renal or uterine blood flow. Higher doses increased maternal cardiac output and blood pressure, did not change renal blood flow, but decreased uterine blood flow. Dopamine consistently caused mild maternal and fetal respiratory acidosis.

Animals↗
PubMed1977

A comparison of methods for quantitating fetal heart rate variability.

Fetal heart rate (FHR) variability is thought to be an important index of fetal health. In the presence of normal variability, the fetus is vigorous, but lack of beat-to-beat variability may be associated with fetal compromise. A distinction between short-term variability (STV) (beat-to-beat changes between successive beats) and long-term variability (LTV) (rhythmic fluctuations in FHR) has not been made to date. We have utilized computer programs to compare three pairs of mathematical indices and one visual index of FHR variability. Among the three pairs of indices designed for detection of STV and LTV, de Haan's short-term and long-term indices exhibited the least interdependence, and the long-term index was completely insensitive to artifically generated pure STV. Yeh's short-term and long-term indices exhibited substantial positive interdependence. Hon's visual index appears to detect LTV primarily rather than STV. When the effect of progression of labor on FHR variability was examined, no conclusions were possible because of inconsistencies between patients. Ultimately, the clinical value of any one of these indices awaits testing of their ability to define fetal well-being or fetal distress.

Analog-Digital Conversion↗
PubMed1977

The direct effects of circulating lidocaine on uterine blood flow and foetal well-being in the pregnant ewe.

We infused lidocaine intravenously into 13 pregnant ewes at a rate sufficient to maintain plasma levels between 2-4 mugm/ml, which are those commonly seen with regional anaesthesia. These levels did not change maternal blood pressure, pulse rate, cardiac output, stroke volume, total peripheral resistance, uterine blood flow or intra-amniotic pressure. Foetal blood pressure and pulse rate remained stable as did both maternal and foetal blood gases and acid-base values.

Animals↗
PubMed1977

Comparison of nitroprusside and hydralazine in hypertensive pregnant ewes.

During phenylephrine-induced hypertension in 6 near-term pregnant ewes, nitroprusside rapidly lowered the blood pressure to control values with no accompanying change in uterine blood flow. Hydralazine slowly lowered the blood pressure to control values. This change was accompanied by a statistically significant (15%) increase in uterine blood flow. Hydralazine also had a more pronounced effect than nitroprusside on cardiac output, heart rate, and total peripheral resistance. There were no significant acid-base changes in mother or fetus throughout the study.

Animals↗
PubMed1976

Epidural anesthesia in the normotensive pregnant ewe: Effects on uterine blood flow and fetal acid-base status.

Lumbar epidural anesthesia was administered to 12 normotensive pregnant ewes. Blood pressure was maintained by intravenous fluid infusion. Six ewes received anesthesia with 1.5 per cent 2-chloroprocaine with 1:100,000 epinephrine and the remaining six received 1.5 per cent 2-chloroprocaine without epinephrine. The sensory level of anesthesia was between the umbilicus and xiphisternum. Except for a transient 14 per cent decrease in uterine blood flow in the ewes receiving 2-chloroprocaine with epinephrine, uterine blood flow remained near control values and was sufficient at all times to maintain stable fetal acid-base and blood gas values. Provided blood pressure and uterine blood flow were stable, the percentage of uterine blood flow distributed to the placenta in the absence of uterine contractions was not altered by epidural anesthesia or by addition of epinephrine to the anesthetic solution.

Acid-Base Equilibrium↗