scholarly journals Evidence for placental-derived iron-nitrosyls in the circulation of the fetal lamb and against a role for nitrite in mediating the cardiovascular transition at birth

2020 ◽  
Vol 319 (4) ◽  
pp. R401-R411
Author(s):  
Arlin B. Blood ◽  
Taiming Liu ◽  
George Mukosera ◽  
Shawn F. Hanson ◽  
Michael H. Terry ◽  
...  
Keyword(s):  
Umbilical Cord ◽  
Plasma Concentrations ◽  
Blood Gases ◽  
Mechanically Ventilated ◽  
Arterial Blood ◽  
Flow Changes ◽  
Near Term ◽  
The Individual ◽  
Carotid Flow

Circulating metabolites of nitric oxide, such as nitrite, iron nitrosyls (FeNO), and nitrosothiols, have vasodilatory bioactivity. In both human and sheep neonates, plasma concentrations of these NO metabolite (NOx) concentrations fall >50% within minutes after birth, raising the possibility that circulating NOx plays a role in maintaining low fetal vascular resistance and in the cardiovascular transition at birth. To test whether the fall in plasma NOx concentrations at birth is due to either ligation of the umbilical cord or oxygenation of the fetus to newborn levels, plasma NOx concentrations were measured during stepwise delivery of near-term fetal lambs. When fetal lambs were intubated and mechanically ventilated with 100% O2 to oxygenate the arterial blood while still in utero with the umbilical circulation still intact, there was no change in plasma NOx levels. In contrast, when the umbilical cord was ligated while fetal lambs were mechanically ventilated with O2 levels that maintained fetal arterial blood gases, plasma NOx levels decreased by nearly 50%. Characterization of the individual NOx species in plasma revealed that the overall fall in NOx at birth was attributable mainly to FeNO compounds. Finally, when the typical fall in NOx after birth was prevented by intravenous nitrite infusion, birth-related changes in blood pressure, heart rate, and carotid flow changes were little affected, suggesting the cardiovascular transition at birth is not dependent on a fall in plasma NOx. In conclusion, this study shows FeNO is released from the placenta and that its decline accounts for most of the measured fall in plasma NOx at birth.

Effect of Thoracentesis on Intubated Patients with Acute Lung Injury

2016 ◽  
Vol 82 (3) ◽  
pp. 266-270
Author(s):  
Matthew B. Bloom ◽  
Derek Serna-Gallegos ◽  
Mark Ault ◽  
Ahsan Khan ◽  
Rex Chung ◽  
...  
Keyword(s):  
Acute Lung Injury ◽  
Lung Injury ◽  
Blood Gases ◽  
Surgical Intensive Care Unit ◽  
Surgical Intensive Care ◽  
Mechanically Ventilated ◽  
Arterial Blood ◽  
Tertiary Center ◽  
Before And After ◽  
The Impact

Pleural effusions occur frequently in mechanically ventilated patients, but no consensus exists regarding the clinical benefit of effusion drainage. We sought to determine the impact of thoracentesis on gas exchange in patients with differing severities of acute lung injury (ALI). A retrospective analysis was conducted on therapeutic thoracenteses performed on intubated patients in an adult surgical intensive care unit of a tertiary center. Effusions judged by ultrasound to be 400 mL or larger were drained. Subjects were divided into groups based on their initial P:F ratios: normal >300, ALI 200 to 300, and acute respiratory distress syndrome (ARDS) <200. Baseline characteristics, physiologic variables, arterial blood gases, and ventilator settings before and after the intervention were analyzed. The primary end point was the change in measures of oxygenation. Significant improvements in P:F ratios (mean ± SD) were seen only in patients with ARDS (50.4 ± 38.5, P = 0.001) and ALI (90.6 ± 161.7, P = 0.022). Statistically significant improvement was observed in the pO2 (31.1, P = 0.005) and O2 saturation (4.1, P < 0.001) of the ARDS group. The volume of effusion removed did not correlate with changes in individual patient's oxygenation. These data support the role of therapeutic thoracentesis for intubated patients with abnormal P:F ratios.

Potentiation of hypoxic pulmonary vasoconstriction by ethyl alcohol in dogs

1978 ◽  
Vol 44 (1) ◽  
pp. 76-80 ◽  
Author(s):  
R. C. Doekel ◽  
E. K. Weir ◽  
R. Looga ◽  
R. F. Grover ◽  
J. T. Reeves
Keyword(s):  
Pressor Response ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Blood Gases ◽  
Adrenergic Blockade ◽  
Mechanically Ventilated ◽  
Pulmonary Vasoconstriction ◽  
Arterial Blood ◽  
Before And After ◽  
Pressor Activity ◽  
Inhibition Of Prostaglandin Synthesis

Pulmonary and systemic hemodynamics and arterial blood gases were measured in anesthetized and mechanically ventilated dogs before and after oral or intravenous administration of ethanol. Increases in mean pulmonary artery pressure and pulmonary vascular resistance occurred. Platelet antiserum-induced thrombocytopenia inhibition of prostaglandin synthesis with meclofenamate, or alpha-adrenergic blockade did not alter the pulmonary pressor response to ethanol. However, the increase in resistance following ethanol was abolished by hyperoxia and potentiated by hypoxia. Thus, it appears that the effect of ethanol is to augment hypoxic pulmonary vasoconstriction, whereas ethanol per se has no independent pulmonary pressor activity.

Umbilical cord occlusion stimulates breathing independent of blood gases and pH

1991 ◽  
Vol 70 (4) ◽  
pp. 1796-1809 ◽  
Author(s):  
S. L. Adamson ◽  
I. M. Kuipers ◽  
D. M. Olson
Keyword(s):  
Prostaglandin E2 ◽  
Umbilical Cord ◽  
Blood Gases ◽  
High Frequency Oscillation ◽  
Breathing Rate ◽  
Fetal Sheep ◽  
Arterial Pco2 ◽  
Arterial Blood Gas ◽  
Arterial Blood

The role of umbilical cord occlusion in the initiation of breathing at birth was investigated by use of 16 unanesthetized fetal sheep near full term. Artificial ventilation with high-frequency oscillation was used to control fetal arterial blood gas tensions. At baseline, PCO2 was maintained at control fetal values and PO2 was elevated to between 25 and 50 Torr. In the first study on six intact and four vagotomized fetuses, arterial PCO2 and PO2 were maintained constant during two 30-min periods of umbilical cord occlusion. Nevertheless, the mean fetal breathing rate increased significantly when the umbilical cord was occluded. In the second study on six intact fetuses, hypercapnia (68 Torr) was imposed by adding CO2 to the ventilation gas. When the umbilical cord was occluded, there was a significantly greater stimulation of breathing (rate, incidence, and amplitude) in response to hypercapnia than in response to hypercapnia alone. During cord occlusion, plasma prostaglandin E2 concentration decreased significantly. Results indicate that cord occlusion stimulates breathing possibly by causing the removal of a placentally produced respiratory inhibitor such as prostaglandin E2 from the circulation.

Fetal Plasma Concentrations after Intraamniotic Sufentanil in Chronically Instrumented Pregnant Sheep

2003 ◽  
Vol 98 (6) ◽  
pp. 1400-1406 ◽  
Author(s):  
Danja Strümper ◽  
Marcel E. Durieux ◽  
Wiebke Gogarten ◽  
Hugo Van Aken ◽  
Kristian Hartleb ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pain Perception ◽  
Plasma Concentrations ◽  
Vital Signs ◽  
Fetal Surgery ◽  
Blood Gases ◽  
Uterine Blood Flow ◽  
Arterial Blood Gases ◽  
Arterial Blood ◽  
Pregnant Sheep

Background Rapid progress is being made in fetal surgery. Because the fetus is capable of pain perception after the 26th week of gestation, adequate postoperative fetal pain management is essential. The preferred approach would provide fetal analgesia without affecting the mother. Intraamniotically administered sufentanil may be an interesting option if it achieves therapeutic plasma concentrations (PCs) in the fetus but not the mother. Methods After approval of the study, 25 or 50 microg sufentanil was administered intraamniotically in 10 chronically instrumented pregnant ewes. Maternal and fetal vital signs, arterial blood gases, and uterine blood flow were recorded over 120 min. Sufentanil PCs were determined before and 1, 3, 5, 10, 15, 30, 45, 60, 90, and 120 min after injection. Statistical analysis was performed using one- or two-way analysis of variance followed by Dunnett or Tukey test, as appropriate (P &lt; 0.05; data presented as median [95% confidence interval]). Results After 25 microg sufentanil, fetal PC stabilized at 134 +/- 89 pg/ml (after 10 min), and maternal PCs stabilized at 44 +/- 11 pg/ml (after 15 min). After 50 microg sufentanil, fetal PCs stabilized at 134 +/- 35 pg/ml (after 15 min), and maternal PCs reached 80 +/- 25 pg/ml (at 30 min). Injection of 25 microg sufentanil intraamniotically did not affect maternal or fetal hemodynamics, uterine blood flow, or arterial blood gases. Fetal heart rate increased after administration of 50 microg sufentanil (maximum change at 10 min: +16 +/- 12%). Conclusion The sheep fetus absorbs sufentanil after intraamniotic instillation. Significantly greater PCs were obtained in the fetal lamb as compared with the ewe. This suggests that investigation of intraamniotic opioids for fetal analgesia might be worthwhile.

Cerebrovascular autoregulation during fetal development in sheep

1994 ◽  
Vol 266 (3) ◽  
pp. H1069-H1074 ◽  
Author(s):  
S. Helou ◽  
R. C. Koehler ◽  
C. A. Gleason ◽  
M. D. Jones ◽  
R. J. Traystman
Keyword(s):  
Perfusion Pressure ◽  
Fetal Brain ◽  
Blood Gases ◽  
Fetal Sheep ◽  
Cerebrovascular Autoregulation ◽  
Cerebrovascular Resistance ◽  
Arterial Blood ◽  
Artificial Cerebrospinal Fluid ◽  
Near Term

There are scant data regarding the development of cerebrovascular autoregulation in fetuses. We tested the hypothesis that a decrease in cerebrovascular resistance (CVR) at reduced cerebral perfusion pressure (CPP) is absent in midgestation and near-term fetal sheep. Catheters were chronically implanted for microsphere determination of cerebral blood flow (CBF) in 9 fetuses at 92 days and in 10 fetuses at 132 days gestation (full term = 145 days). CPP was reduced by ventricular infusion of artificial cerebrospinal fluid. In 92-day fetuses, CPP was reduced stepwise from 35 to 25 and 18 mmHg and CBF decreased from 52 +/- 5 to 43 +/- 4 and 27 +/- 5 (SE) ml.min-1 x 100 g-1, respectively. Half of the immature fetuses showed some reduction in CVR at moderate reduction in CPP; however, there was no significant change in CVR in the group as a whole (from 0.72 +/- 0.06 to 0.61 +/- 0.04 and 0.89 +/- 0.20 mmHg.ml-1.min.100 g). In 132-day fetuses, CPP was reduced from 45 to 33 and 28 mmHg and CBF was unchanged (from 105 +/- 7 to 97 +/- 11 and 89 +/- 8 ml.min-1 x 100 g-1). CVR decreased from 0.45 +/- 0.05 to 0.41 +/- 0.08 and 0.33 +/- 0.03 mmHg.ml-1.min.100 g. There were no significant changes in arterial blood gases at reduced CPP in either age group. We conclude that cerebrovascular autoregulation at reduced CPP is not well developed at 92 days (0.63 gestation) in fetal sheep but that autoregulatory capacity is evident near term. We speculate that poor autoregulation may place the premature fetal brain at risk for injury.

Systemic acidosis after controlled hypotension activates catechol activity in the vasomotor center

1994 ◽  
Vol 76 (6) ◽  
pp. 2594-2601 ◽  
Author(s):  
N. Bruandet ◽  
L. Quintin
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Recovery Period ◽  
Blood Gases ◽  
Controlled Hypotension ◽  
Mechanically Ventilated ◽  
Vasomotor Center ◽  
Arterial Blood ◽  
Phenylephrine Infusion

Activation of the catechol metabolism, assessed with in vivo voltammetry, in the vasopressor area of the vasomotor center was investigated during systemic acidosis occurring after controlled hypotension. Rats anesthetized with halothane were mechanically ventilated. Sodium nitroprusside lowered mean arterial pressure to 55 mmHg for > or = 20 min. Arterial blood gases allowed us to group rats according to whether they showed symptoms of metabolic acidosis (pH < or = 7.34) immediately after controlled hypotension. To assess the effect of systemic acidosis independently of the progressive decline in pressure observed during the recovery period after controlled hypotension, we used phenylephrine infusion to maintain mean arterial pressure at baseline pressure during the recovery period after controlled hypotension in two groups of animals. Systemic acidosis increased the catechol signal in a prolonged manner [nitroprusside with acidosis (n = 7) vs. nitroprusside without acidosis (n = 5); P < 0.0001]. This catechol activation was greater when pressure was restored after hypotension [nitroprusside with acidosis plus phenylephrine (n = 5) vs. nitroprusside with acidosis over the whole interval (from -30 to +150 min); P < 0.05]. When the nitroprusside with acidosis group and nitroprusside with acidosis plus phenylephrine group were compared, hypercapnia had an involvement in the larger increase of the catechol signal observed in the nitroprusside with acidosis plus phenylephrine group [arterial PCO2: nitroprusside with acidosis vs. nitroprusside with acidosis plus phenylephrine over the whole interval (from -30 to +150 min) and at +30 and +60 min; all P < 0.05].(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax

1996 ◽  
Vol 81 (4) ◽  
pp. 1664-1669 ◽  
Author(s):  
Paula Carvalho ◽  
Jacob Hildebrandt ◽  
Nirmal B. Charan
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Tension Pneumothorax ◽  
Blood Gases ◽  
Left Pulmonary Artery ◽  
Arterial Blood Flow ◽  
Mechanically Ventilated ◽  
Arterial Blood ◽  
Flow Through ◽  
Pulmonary Arterial

Carvalho, Paula, Jacob Hildebrandt, and Nirmal B. Charan.Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax. J. Appl. Physiol. 81(4): 1664–1669, 1996.—We studied the effects of unilateral tension pneumothorax and its release on bronchial and pulmonary arterial blood flow and gas exchange in 10 adult anesthetized and mechanically ventilated sheep with chronically implanted ultrasonic flow probes. Right pleural pressure (Ppl) was increased in two steps from −5 to 10 and 25 cmH2O and then decreased to 10 and −5 cmH2O. Each level of Ppl was maintained for 5 min. Bronchial blood flow, right and left pulmonary arterial flows, cardiac output (Q˙t), hemodynamic measurements, and arterial blood gases were obtained at the end of each period. Pneumothorax resulted in a 66% decrease inQ˙t, bronchial blood flow decreased by 84%, and right pulmonary arterial flow decreased by 80% at Ppl of 25 cmH2O ( P < 0.001). At peak Ppl, the majority ofQ˙t was due to blood flow through the left pulmonary artery. With resolution of pneumothorax, hemodynamic parameters normalized, although abnormalities in gas exchange persisted for 60–90 min after recovery and were associated with a decrease in total respiratory compliance.

Fetal acidosis and hypotension during repeated umbilical cord occlusions are associated with enhanced chemoreflex responses in near-term fetal sheep

2005 ◽  
Vol 99 (4) ◽  
pp. 1477-1482 ◽  
Author(s):  
Laura Bennet ◽  
Jenny A. Westgate ◽  
Yung-Chi (“Jack”) Liu ◽  
Guido Wassink ◽  
Alistair J. Gunn
Keyword(s):  
Umbilical Cord ◽  
Fetal Heart ◽  
Severe Hypoxia ◽  
Acid Base ◽  
Fetal Sheep ◽  
Arterial Blood ◽  
Acid Base Status ◽  
Near Term ◽  
Fetal Acidosis ◽  
Fetal Compromise

This study examined the hypothesis that repeated episodes of brief but severe hypoxia would not attenuate the chemoreflex-mediated rapid initial fall in fetal heart rate (FHR) and, further, that greater hypoxic stress, as shown by hypotension and metabolic acidosis, would be associated with an enhanced chemoreflex response. Chronically instrumented, near-term fetal sheep received 1 min total umbilical cord occlusion either every 5 min for 4 h (1:5 group; n = 8) or every 2.5 min (1:2.5 group; n = 8) until mean arterial blood pressure fell to <20 mmHg on two successive occlusions. Umbilical cord occlusion caused variable decelerations, with sustained hypertension in the 1:5 group and little change in acid-base status (pH 7.34 ± 0.03 after 4 h). In contrast, the 1:2.5 group showed progressive hypotension and metabolic acidemia (pH 6.92 ± 0.04 after the last occlusion). The 1:2.5 group showed a significant increase in the rate of initial fall in FHR during the occlusion series, which was greater than the 1:5 group in the last 30 min of the occlusion series (9.4 ± 1.4 vs. 3.5 ± 0.3 beats·min−1·s−1; P < 0.01), with a greater fall in FHR (71.9 ± 6.5 vs. 47.0 ± 8.7 beats/min; P < 0.05). In summary, this study demonstrated that repetitive laborlike cord occlusions, which led to severe fetal compromise, were associated with an increase in the slope and magnitude of the initial FHR deceleration. These findings support the concept of the chemoreflex as a central, robust component of fetal adaptation to severe hypoxia.

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