Responses of fetal sheep to simulated no-decompression dives

1980 ◽  
Vol 48 (5) ◽  
pp. 776-780 ◽  
Author(s):  
M. K. Stock ◽  
E. H. Lanphier ◽  
D. F. Anderson ◽  
L. C. Anderson ◽  
T. M. Phernetton ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Maternal Blood ◽  
Arterial System ◽  
Fetal Sheep ◽  
Monitoring Result ◽  
Placental Blood ◽  
Near Term ◽  
Placental Blood Flow ◽  
Maternal Blood Pressure

The effect of simulated standard no-decompression dives to 60 and 100 ft of seawater was tested in 12 near term sheep carrying 16 fetuses. In the immediate postdive period there were no significant changes in fetal blood pressure or fetal placental or renal blood flow, but the maternal blood pressure was elevated and the maternal placental blood flow was depressed. Six surgically prepared fetuses were dived to 100 ft. Five died within 20 min of ascent and the sixth suffered severe cardiac arrhythmia and hypotension. At autopsy all fetuses were observed to have massive bubbling in the arterial system and heart. Five fetuses were dived to 100 ft without surgery. Two were alive 3 h later and no bubbles were present at autopsy, and three were born alive at term. With the 60-ft dives, three fetuses were subjected to surgery and all suffered massive bubbling. Two fetuses were dived to 60 ft without surgery; one was alive after 3 h and the other was born alive at term. We conclude that surgery and monitoring result in the formation of postdive gas bubbles that would not otherwise appear.

Norepinephrine versus Ephedrine Boluses To Treat Spinal-Induced Hypotension in Cesarean Deliveries

QJM ◽  
2021 ◽  
Vol 114 (Supplement_1) ◽  
Author(s):  
Mohamed M Abo Kamar ◽  
Manal M Shams ◽  
Mai M AbdelAziz ◽  
Wessam Z Selima
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Spinal Anesthesia ◽  
Cesarean Delivery ◽  
Hypotensive Effect ◽  
Maternal Blood ◽  
Neurological Injury ◽  
Maternal Complications ◽  
Placental Blood ◽  
Maternal Blood Pressure

Abstract Corresponding Background Cesarean sections normally require an anesthetic block at T4 level, so hypotension is reported to occur in up to 80% of spinal anesthesia cases. When maternal hypotension associated with spinal anesthesia for cesarean section is severe and sustained, it can lead to serious maternal complications as well as impairment of the uterine and placental blood flow with consecutive fetal hypoxia, acidosis, and neurological injury. Aim of the Work to compare the administration of intermittent i.v. boluses of norepinephrine and ephedrine to counterbalance the hypotensive effect of spinal anesthesia during cesarean delivery. The results of the study showed that compared with ephedrine, norepinephrine maintained maternal blood pressure and uterine artery blood flow. Further, it was associated with lower numbers of hypotension and hypertension episodes and less frequency of bradycardia and tachycardia during cesarean delivery. Furthermore, the numbers of boluses of vasopressors used during spinal anesthesia were lower in norepinephrine compared with the use of ephedrine. Conclusion Norepinephrine can be used as an alternative vasopressor to maintain maternal blood pressure during spinal anesthesia for cesarean delivery, with no adverse effect on neonatal outcome.

Peripheral chemoreflex activation and cardiac function during hypoxemia in near term fetal sheep without placental compromise

2021 ◽  
Author(s):  
Juulia Lantto ◽  
Tiina Erkinaro ◽  
Mervi Haapsamo ◽  
Heikki Huhta ◽  
Leena Alanne ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Carotid Artery ◽  
Arterial Oxygen ◽  
Sheep Model ◽  
Fetal Sheep ◽  
Descending Aorta ◽  
Arterial Blood ◽  
Near Term ◽  
Peripheral Chemoreflex

A drop in arterial oxygen content activates fetal chemoreflex including an increase in sympathetic activity leading to peripheral vasoconstriction and redistribution of blood flow to protect the brain, myocardium, and adrenal glands. By using a chronically instrumented fetal sheep model with intact placental circulation at near-term gestation, we investigated the relationship between peripheral chemoreflex activation induced by hypoxemia and central hemodynamics. 17 Åland landrace sheep fetuses at 115-128/145 gestational days were instrumented. Carotid artery was catheterised in 10 fetuses and descending aorta in 7 fetuses. After a 4-day recovery, baseline measurements of fetal arterial blood pressures, blood gas values, and fetal cardiovascular hemodynamics by pulsed Doppler ultrasonography were obtained under isoflurane-anesthesia. Comparable data to baseline was collected 10 (acute hypoxemia) and 60 minutes (prolonged hypoxemia) after maternal hypo-oxygenation to saturation level of 70-80% was achieved. During prolonged hypoxemia, pH and base excess (BE) were lower, and lactate levels higher in the descending aorta than in the carotid artery. During hypoxemia mean arterial blood pressure (MAP) in the descending aorta increased, while in the carotid artery MAP decreased. In addition, right pulmonary artery pulsatility index values increased, and the diastolic component in the aortic isthmus blood flow velocity waveform became more retrograde. Both fetal ventricular cardiac outputs were maintained even during prolonged hypoxemia when significant fetal metabolic acidemia developed. Fetal chemoreflex activation induced by hypoxemia decreased the perfusion pressure in the cerebral circulation. Fetal weight-indexed LVCO or AoI Net Flow-ratio did not correlate with a drop in carotid artery blood pressure.

scholarly journals Effect of transdermal nitroglycerin patch on severe preeclamptic women with abnormal Doppler indices

2019 ◽  
Vol 8 (2) ◽  
pp. 597
Author(s):  
El-Sayed S. El-Ebshehy ◽  
Ahmed M. Hagras ◽  
Amr T. Elbadry ◽  
Ahmed M. Awara
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Maternal Blood ◽  
Placental Insufficiency ◽  
University Hospitals ◽  
Singleton Pregnancy ◽  
Arterial Blood ◽  
Risk Pregnancy ◽  
Doppler Indices ◽  
Maternal Blood Pressure

Background: The aim is to evaluate the effect of maternal transdermal nitro-glycerine patch administration on blood flow resistance on maternal uterine artery, fetal umbilical and middle cerebral arteries in patients with severe pre-eclampsia in early gestational age (24 weeks to 33 weeks) associated with abnormal Doppler indices (placental insufficiency) and also its effect on maternal mean arterial blood pressure.Methods: This is a prospective interventional clinical trial conducted on (50) pregnant women with singleton pregnancy diagnosed with severe pre-eclampsia admitted in high-risk pregnancy unit at the Department of Obstetrics  in Tanta University Hospitals, A 50-mg transdermal GTN patch (Novartis Pharma) was applied to the abdominal skin, releasing nitroglycerin at a rate of 0.4 mg/h. Doppler ultrasonography and measurement of maternal blood pressure were performed before application of transdermal GTN patch, after 4 hours of application, after 24 hours and after 48 hours.Results: the application of a 50-mg transdermal GTN patch to the maternal abdomen was associated with a significant decline in the PI of the uteroplacental and fetoplacental blood flow. No change was observed in the PI of the cerebral circulation. And also, there was a significant decrease in maternal blood pressure (MAP).Conclusions: Nitroderm patch (nitric oxide donors) may be used as initial therapy in cases of severe preeclampsia complicated by placental insufficiency in the form of abnormal Doppler indices.

Fetal sheep endocrine responses to sustained hypoxemic stress after chronic fetal placental embolization

1997 ◽  
Vol 272 (5) ◽  
pp. E817-E823 ◽  
Author(s):  
R. Gagnon ◽  
J. Murotsuki ◽  
J. R. Challis ◽  
L. Fraher ◽  
B. S. Richardson
Keyword(s):  
Blood Flow ◽  
Oxygen Content ◽  
Regional Distribution ◽  
Arterial Oxygen ◽  
Control Group ◽  
Fetal Sheep ◽  
Arterial Oxygen Content ◽  
Placental Blood ◽  
Chronic Hypoxemia ◽  
Placental Blood Flow

The purpose of this study was to determine the endocrine and circulatory responses of the ovine fetus, near term, to sustained hypoxemic stress superimposed on chronic hypoxemia. Fetal sheep were chronically embolized (n = 7) for 10 days between 0.84 and 0.91 of gestation via the descending aorta until arterial oxygen content was decreased by approximately 30%. Control animals (n = 8) received saline only. On experimental day 10, both groups were embolized over a 6-h period until fetal arterial pH decreased to approximately 7.00. Regional distribution of lower body blood flows was measured on day 10, before and at the end of acute embolization. On day 10, the chronically embolized group had lower arterial oxygen content (P < 0.05), Po2 (P < 0.01), and placental blood flow (P < 0.05) than controls and higher prostaglandin E2 (PGE2) and norepinephrine plasma concentrations (both P < 0.05). In response to a superimposed sustained hypoxemic stress, there was a twofold greater increase in PGE2 in the chronically embolized group than in the control group (P < 0.05). However, the increase in fetal plasma cortisol in response to superimposed hypoxemic stress was similar in both groups, despite significantly lower adrenocorticotropic hormone and adrenal cortex blood flow responses in the chronically hypoxemic group (both P < 0.05). We conclude that PGE2 response to a sustained superimposed reduction in placental blood flow, leading to metabolic acidosis, is enhanced under conditions of chronic hypoxemia and may play an important role for the maintenance of the fetal cortisol response to an episode of superimposed acute stress.

Regional adrenal blood flow responses to adrenocorticotropic hormone after chronic embolization of the fetal placental circulation in sheep

1996 ◽  
Vol 148 (3) ◽  
pp. 517-522 ◽  
Author(s):  
A M Carter ◽  
J R G Challis ◽  
P Svendsen
Keyword(s):  
Blood Flow ◽  
Adrenal Cortex ◽  
Adrenocorticotropic Hormone ◽  
Maternal Blood ◽  
Arterial Oxygen ◽  
Fetal Sheep ◽  
Cortical Blood Flow ◽  
Arterial Oxygen Content ◽  
Blood Flows ◽  
Placental Blood

Abstract To ascertain whether repeated hypoxic stress would alter the response of the adrenal cortex to adrenocorticotropic hormone (ACTH), by premature activation of the hypothalamic–pituitary–adrenal axis, we studied fetal sheep subjected to daily reduction of arterial oxygen content by embolization of the fetal placental circulation with 15 μm microspheres for 8 days from about day 124 of gestation (term ∼147 days) and sham-embolized controls. Starting before the final embolization (or shamembolization) on day 8, and continuing for 24 h, the fetus was given an intravenous infusion of ACTH1–24 (0·5 μg/h) or vehicle. Fetal and maternal blood samples were taken for determination of immunoreactive cortisol, and regional adrenal and fetal placental blood flows were measured by the microsphere technique at three time points: 1 h before infusion, 3 h after the start of the infusion (1 h after embolization), and after 24 h of infusion. Prior to infusion of ACTH or vehicle, fetal placental blood flow was lower in microsphere-embolized fetuses than in sham-embolized controls (199 ± 15 vs 292 ± 25 ml/min per 100 g tissue; mean ± s.e.; P<0·01). However, plasma cortisol and adrenal cortical blood flow did not differ between embolized fetuses and controls. Adrenal vascular responses to the 24-h infusion of ACTH were similar in embolized and shamembolized fetuses. Adrenal cortical blood flow increased 3-fold (P<0·05) due to decreased vascular resistance (P<0·01), with no change in adrenal medullary blood flow. Thus, while daily embolization of the fetal placental circulation caused a sustained decrease in cotyledonary blood flow, no evidence of altered responsiveness of the adrenal cortex to ACTH was found in these experiments. Journal of Endocrinology (1996) 148, 517–522

Regulation of fetal placental blood flow in the lamb

1984 ◽  
Vol 247 (3) ◽  
pp. R567-R574 ◽  
Author(s):  
D. F. Anderson ◽  
J. J. Faber
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Arterial Blood Pressure ◽  
Fetal Growth ◽  
Control Value ◽  
Flow Restriction ◽  
Arterial Blood ◽  
Placental Blood ◽  
Carotid Arterial ◽  
Placental Blood Flow

Inflatable occluders were placed on the distal aorta of 11 fetal lambs. After 1 wk of control measurements, fetal placental blood flow was reduced to about two-thirds of its control value for an average period of 2 wk. No allowance was made for fetal growth. During the period of flow restriction, fetal growth was 2%/day. Femoral arterial blood pressure was reduced from a control value of 41 to 27 mmHg (P less than 0.001). There was an insignificant increase in carotid arterial blood pressure from 48 to 50 mmHg. Placental resistance to flow did not decrease more than could be accounted for by the increase in gestational age in the course of the experiment. It is concluded that fetal placental blood flow is not under feedback control, since neither of the determinants of flow (i.e., driving pressure and resistance) responded to its chronic reduction.

Magnesium Sulfate Decreases Maternal Blood Pressure but Not Uterine Blood Flow during Epidural Anesthesia in Gravid Ewes

1991 ◽  
Vol 74 (1) ◽  
pp. 77-82 ◽  
Author(s):  
Robert D. Vincent ◽  
David H. Chestnut ◽  
Susan L. Sipes ◽  
Carl P. Weiner ◽  
Craig S. DeBruyn ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Magnesium Sulfate ◽  
Epidural Anesthesia ◽  
Maternal Blood ◽  
Uterine Blood Flow ◽  
Maternal Blood Pressure
Sign in / Sign up

Export Citation Format

Share Document