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Biomedical subjects

R Tenbrinck

Publications and source records attributed to R Tenbrinck.

32 records · Page 2Linked to original sources
PubMed1990

Acute hypervolaemic haemodilution to avoid blood transfusion during major surgery.

16 patients underwent acute hypervolaemic haemodilution with dextran 40 and Ringers lactate, to see whether this procedure could avoid preoperative blood transfusion. Packed cell volume (PCV) and oxygen extraction decreased, and cardiac index and pulmonary wedge pressure increased, although end-systolic area was unchanged. PCV was not significantly different between patients who lost less than or greater than 20% of their initial blood volume. This preoperative manoeuvre, which reduces loss of red blood cells, allowed major surgery to be completed safely without blood transfusion.

Adult↗
PubMed1990

Cardiovascular responses, hemodynamics and oxygen transport to tissue during moderate isovolemic hemodilution in pigs.

In conclusion, in contrast to many reports obtained from dogs, in pigs the rise in CO during moderate isovolemic hemodilution is, besides the increased venous return, more induced by increased work performance of the heart and less by a decreased SVR. The rise in CO did not compensate for the decrease in oxygen transport capacity. Our results confirm most of the reported findings in humans at the same stage of hemodilution. Besides changes in hemodynamics, in our study a gradual decreased oxygen affinity of hemoglobin could be observed. That the pig animal model for studying hemodilution and oxygen transport to the tissue is more appropriate than the dog model is open to discussion.

Animals↗
PubMed1990

Nitrofen-induced diaphragmatic hernias in rats: an animal model.

In embryological terms, pathogenesis of congenital diaphragmatic hernia (CDH) associated with pulmonary hypoplasia is still unclear. However, it is known since 1971 that Nitrofen (2,4-dichloro-phenyl-p-nitrophenyl ether) can induce anatomical malformations in rats including diaphragmatic hernias. On order to establish an animal model of the embryogenesis of CDH, the effect of Nitrofen on the developing diaphragm was studied. Thirty-three pregnant female rats were exposed to Nitrofen. Five unexposed pregnant rats served as controls. In the first set of experiments, single doses of Nitrofen were given between the 9th and 13th day of pregnancy. In the second set of experiments, dosages of 50, 100, and 150 mg per animal were given on day 11 of pregnancy only. Postnatally the litters (469 newborn rats) were dissected to record the incidence of diaphragmatic malformations. The results were: (1) most hernias occurred after administration of 100 mg Nitrofen on day 9 (42%) and 11 (59%); (2) left-sided hernias were observed only after exposure to Nitrofen on day 9; (3) after exposure on day 10 or later all hernias were on the right side; and (4) Fifty-nine percent of the newborn rats exposed on day 11 had CDH. These results show that this model is suitable for further embryological investigations on the development of CDH.

Animals↗
PubMed1990

Experimentally induced congenital diaphragmatic hernia in rats.

Experiments to induce congenital diaphragmatic hernia (CDH) in rats, by means of administering a single dose of 2,4-dichlorophenyl-P-nitrophenyl (Nitrofen) on the 10th day of gestation, are reported here. Previously, congenital diaphragmatic hernia has been induced in sheep late in fetal development, and in mice early in gestation. The rat model, including a control group, was used to evaluate lung development and the presence of lung hypoplasia by morphometrical analysis. It was found that the single dose of Nitrofen, given 5 days before the normal closure of the diaphragm in the rat, leads to a high incidence of diaphragmatic hernia, mainly on the right side, and highly abnormal lung development (hypoplasia) comparable to the human situation. Both the lung weight/body weight index as well as the radial alveolar count were significantly lower in animals with CDH (P less than .05). This animal model offers a good opportunity to study abnormal lung development in relation to ventilatory capacity and pulmonary vascular reactivity.

Animals↗
PubMed1990

Oral immunization with bacterial lysate against infection with Streptococcus pneumoniae in mice.

The protective effect of oral immunization against infection with Streptococcus pneumoniae was investigated in mice. Two bacterial lysates, one with an additional lysate of Candida albicans, were investigated. Intranasal inoculation of adult Balb-C mice with a S. pneumoniae type I strain resulted in a lethal infection, with deaths occurring from the 2nd until the 6th day after infection. Oral immunization resulted in a significant decrease in mortality rate (18-48% reduction). No significant difference in mortality rates was observed between the groups immunized with different lysates in the same concentrations.

Adjuvants, Immunologic↗
PubMed1990

Blood gas analysis of mixed venous blood during normoxic acute isovolemic hemodilution in pigs.

Mixed venous oxygen saturation of hemoglobin (SvO2) and mixed venous oxygen tension (PvO2) may reflect the overall balance between oxygen consumption and delivery. Because of the potential value of monitoring SvO2 and PvO2 as indications of the state of tissue oxygenation, the aim of this study was to determine, during normoxic acute isovolemic hemodilution in pigs, the critical PvO2, critical SvO2, and critical oxygen extraction ratio (ER) at which oxygen uptake starts to decline during further induced hemodilution. During stepwise induced isovolemic hemodilution, a gradual decline in SvO2 and PvO2 was observed in all animals. The mean +/- SD of the critical PvO2 of six animals was 32.3 +/- 3.1 mm Hg. The mean +/- SD of the critical SvO2 was 44.2% +/- 7.9%. The ER increased gradually. At an ER of 0.57 +/- 0.08, oxygen uptake started to decline. A significant correlation was found between changes in SvO2 and changes in ER. These degrees of hemodilution were accompanied by an increase in cardiac index, pulmonary wedge pressure, heart rate, and left ventricular stroke work index. Only a slight decrease in systemic vascular resistance was observed. We conclude that measurements of PvO2 and SvO2 can be used as indicators of the critical point of hemodilution and that the SvO2 during hemodilution reflects the overall balance between oxygen uptake and oxygen delivery, confirmed by the strong correlation found between SvO2 and oxygen extraction ratio.

Animals↗
PubMed1990

S35: a new parameter in blood gas analysis for monitoring the systemic oxygenation.

In the estimation of oxygen transport the term oxygen availability is used as the product of cardiac output and the arterial oxygen content (CaO2). Attempts can be made to modify the concept of oxygen availability by subtracting from the CaO2 the venous content at a critical PO2 as measured in mixed venous blood (Pv-O2), where oxygen diffusion into tissue becomes compromised and oxygen uptake (VO2) may decrease. The real arterial available oxygen content (CavlO2) can be calculated by estimating the saturation at the critical Pv-O2. For our concept S35 was chosen as such a dynamic baseline. Similar modification of oxygen extraction ratio (ERav) defined as VO2 divided by the real oxygen availability (O2av) should give, more than the classic ER, a realistic indices of oxygen availability in relation to oxygen consumption. It can be hypothesized that VO2 starts to decline when ERav is around 1.0. During isovolemic hemodilution VO2 started to drop when ERav reached 1.08 +/- 0.09. The S35 changed from 55.0 +/- 2.1% to 41.5 +/- 4.1%, correlated with changes in Pv-O2. A direct correlation was also found between the increase of the classic ER and the change in S35. We conclude that the S35, the CavlO2 and the ERav can be of value in monitoring the systemic oxygenation and that the concept also includes the effect of changes in oxyhemoglobin characteristics on oxygen delivery.

Arteries↗
PubMed1989

Effects of high frequency jet ventilation on the pulmonary clearance of 99mTc-DTPA in respiratory failure in rabbits.

The effects of high frequency jet ventilation (HFJV) at 2 and 15 Hz on the pulmonary clearance of technetium 99m diethylene triamine pentaacetate (99mTc-DTPA) were compared with conventional volume-controlled (VC) ventilation with positive end-expiratory pressure (PEEP), in a model of respiratory failure induced by two lung lavages in adult rabbits. In group 1 the lungs were ventilated with HFJV at 2 Hz, and in group 2 ventilation was with HFJV at 15 Hz; group 3 underwent conventional VC ventilation. Group 4 also had conventional ventilation, but without previous lung lavage and functioned as a control group. In all groups, mean airway pressure was maintained at a value to ensure PaO2 greater than 25 kPa. The measured half-life time (T1/2) of the 99mTc-DTPA (mean (SD] was: group 1, 28 (7.8) min; group 2, 73.5 (7.9) min; group 3, 56.5 (12.4) min and group 4, 92.6 (13.2) min. Assuming that conventional VC with PEEP ventilation causes no additional harm to surfactant depleted lungs, it is concluded that HFJV at 2 Hz leads to further damage of the lungs, whereas HFJV at 15 Hz improves reparative processes, by keeping the lungs constantly inflated.

Anesthesia, Intravenous↗
PubMedDate not supplied

Angiotensin-converting enzyme activity is increased in lungs of rats with pulmonary hypoplasia and congenital diaphragmatic hernia.

Lung hypoplasia (LH) and pulmonary hypertension are responsible for the high mortality rate in congenital diaphragmatic hernia (CDH) patients. Angiotensin-converting enzyme (ACE) plays a role in the regulation of pulmonary vascular resistance in the postnatal period and might be involved in the development of pulmonary hypertension of the newborn. A study was made of the development of ACE activity spectrophotometrically in a rat model of LH and CDH. It was previously shown that the lungs in this model are hypoplastic and the muscularization of the pulmonary vascular bed is increased. CDH was induced in fetal rats by oral administration of 115 mg/kg Nitrofen to the mother on day 10.5 of pregnancy. Fetuses were delivered by hysterotomy on days 19, 20, 21, and 22. Nitrofen-exposed rats showed significantly lower lung weights and not statistically significant lower total ACE activities than in controls. ACE activity expressed per milligram lung wet weight and per milligram protein was significantly increased compared to controls. ACE converts angiotensin I to the vasoconstrictor angiotensin II, and it inactivates the vasodilator bradykinin. Increased ACE activity may therefore contribute to pulmonary hypertension. Whether ACE and angiotensin II levels are increased in human newborns with a diaphragmatic defect and whether they contribute to the development of persistent pulmonary hypertension has not been studied up till now.

Animals↗