A new simple tool for tonometric determination of the PCO2 in the gastrointestinal tract: in vitro and in vivo validation studies.

BACKGROUND AND OBJECTIVE: Following the discovery of the feasibility of assessing the adequacy of the splanchnic perfusion by means of gastrotonometry, this technique became extensively used in clinical practice and in research. At present, high-technology instruments are available for the purpose. However, there is still a need for a simple, cheap tool that is easily applicable for patients of all ages. The present article describes such a tool and presents the results of in vitro and in vivo validation measurements with it. METHODS: Balloon-free tonometric probes consisting of silicone rubber tubes were developed. In vitro measurements of the uptake of CO2 inside the probes and for comparison in a conventional ballooned intestinal tonometer were made in a closed container maintained at 37 degrees C. In in vivo studies in anaesthetized dogs, the tonometric PCO2 values were determined with a tonometric probe and catheter introduced simultaneously into the ileum of the animals and the results were analysed by the Bland-Altman method. RESULTS: The in vitro equilibration studies revealed that the filling media inside the probes equilibrated rapidly with the PCO2 content of the chamber. The data obtained from the in vivo investigations with the two different methods demonstrated a statistically significant linear association (correlation coefficient: 0.778, significance: P < 0.001). CONCLUSION: The new simple tonometric probe described appears to be a reliable tool with certain advantages for gastric tonometry. However, further studies are warranted before its general clinical use.

Inhibitory effects of methylxanthines on the pre-eclamptic-like symptoms in ewes.

OBJECTIVE: Our objective was to determine whether two methylxanthines, pentoxifylline (PTX) and allopurinol, would have beneficial effects on experimental pregnancy-induced pre-eclampsia- like disease in ewes. STUDY DESIGN: 20 animals at the gestational age of 130-135 days were divided into four groups (control; fasting; fasting, pentoxifylline-treated; and fasting, allopurinol-treated). The illness was provoked with a 4-day fasting period. Electrolytes, glucose, conventional parameters, plasma haem content, indirect bilirubin concentration and free thiol levels were measured. RESULTS: Unlike in the fasting group, conventional signs of the disease, such as hypertension, kidney and liver injury and platelet count decrease, were all mitigated in the fasting, drug-treated animals. In the treated animals plasma haem content increased by a less significant level, while indirect bilirubin concentration showed a more rapid rise. CONCLUSIONS: Both methylxanthines partly inhibited the pre-eclamptic-like symptoms in ewes. We speculate that the better induction of haem oxygenase might play an important role in this inhibitory effect on this particular animal model.

Renal injury in perinatal hypoxia: ultrasonography and changes in renal function.

UNLABELLED: We studied 12 hypoxaemic neonates (5 mature newborns, birth weight 2850-4200 g, gestational age 37-41 weeks; and 7 premature newborns, birth weight 770-1850 g, gestational age 27-34 weeks;) with repeated urine and blood chemistry on the 1st and 3rd days of life. Nephrosonographical examinations on the 1st, 3rd and 5-7th days of life were also performed. As controls, 12 healthy infants were examined (gestational age 36-42 weeks; birth weight 24504200 g). Hypoxic neonates had higher serum creatinine and blood urea nitrogen levels. Tubular markers also demonstrated renal tubular damage. Neonates in both hypoxic groups were hyperuricaemic and hyperuricosuric, and had higher urinary protein concentrations. All these infants exhibited an increased echogenicity of the renal cortex, and 11/12 showed the same finding in the medullary area. These findings disappeared within 1 week in all infants. Among the 12 healthy control infants, no cortical hyperechogenicity was found and only three of these infants displayed transient medullary renal hyperechogenicity. CONCLUSION: Since the hypoxaemic infants demonstrated greatly increased urinary concentrations of uric acid and protein, we suggest that a temporary precipitation of these two agents may be responsible for the ultrasonographic findings. Circulatory redistribution might play a role in the phenomenon of cortical hyperechogenicity.

The pathogenetic role of heme in pregnancy-induced hypertension-like disease in ewes.

Toxicosis syndrome of fasting pregnant ewes has a close similarity to human preeclampsia (hypertension, albuminuria). The common etiological factor might be oxidative hemolysis and heme-induced endothelial damage. Ewes (5 starving, 5 control) at 130-135 gestational days with a 96-h fasting period followed by refeeding were used. Blood pressure, platelet count, electrolytes, kidney and liver function parameters, as well as plasma glucose, hemoglobin/heme, free thiol groups and Trolox equivalent antioxidant capacity, and plasma iron and ferritin levels were measured. Statistical significance was assessed using Student's t test (P < 0.05). Besides hypertension and renal disturbances, hemolysis, elevated liver enzymes and low platelet count, characteristic of human HELLP syndrome, were also present. In the first 24 h of glucose deprivation there was a significant rise in both the plasma hemoglobin/heme and indirect bilirubin concentrations. The antioxidant free thiol levels decreased significantly the next day, without any change in the total antioxidant capacity of the plasma. While the loss of calcium and magnesium levels related to the similarity to preeclampsia, reduced plasma iron concentrations referred to species differences in iron homeostasis. An oxidative stress causing hemolysis in a glucose-6-phosphate dehydrogenase-deficient animal model was proven by the loss of free thiols after glucose deprivation. The activation of the oxidative stress protein heme oxygenase was a signal of endothelial cell injury, the primary cause of pregnancy-induced hypertension.

The possible role of uric acid in renal hyper-echogenicity in neonatal hypoxic acute shock.

Sonographic examinations as well as blood and urine chemistry tests were carried out in 4 neonates (3 mature, 1 premature) with transient renal failure, who were suffering from the effects of neonatal asphyxia of varying etiology. The first ultrasound examinations of the kidneys were performed within 24 hours after the hypoxic event. Simultaneously, blood and urine tests for parameters of renal function and purine metabolites were also carried out. Transient insufficiency of renal function could be detected in all cases with hyper-uricemia and hyper-uricosuria with no hypercalciuria. Ultrasonographic examinations showed hyper-echogenicity of the renal pyramids in all of the cases and hyper-reflectivity of the renal cortex in cases 2 and 4. In 3 cases, hyper-echogenicity appeared within 24 hours and disappeared in a short time, while in case 3 it could be detected from day 4 until day 14. These findings demonstrate, that the neonatal kidney is very sensitive to hypoxia and that hypoxic renal failure is accompanied by hyper-echogenicity of the kidneys. Uric acid is a possible cause of the renal hyper-echogenicity.