Experimental post-traumatic lung insufficiency in dogs. Gross and light microscopic lung lesions

Post-traumatic lung insufficiency in dogs was induced by a combination of haemorrhagic hypotension and liver trauma. In one experimental group, lung biopsies were sampled every 4 h. This paper describes the development of gross and light microscopic lunig changes in these dogs, and the lung lesions 12 h after initiation of the trauma in another experimental group. Incipient changes were recognized as early as 4 h after initiation of the trauma. Perivascular and intraseptal oedema, scattered microthrombi, and trapping of leucocytes in lung microvessels were the most conspicuous morphological findings. These changes grew gradually more pronounced towards collapse, when also areas with interstitial haemorrhages, intra-alveolar protein-rich oedema fluid with strands of a fibrinoid material, and an increased number of partly degenerated leucocytes were found in addition to atelectasis.

The morphological lung lesions in this experimental model are similar to post-traumatic shock lungs in human patients.

Plasma hypoxanthine in exteriorized, acutely asphyxiated fetal lambs

Plasma hypoxanthine (HX) concentrations were measured in 16 acutely exteriorized fetal lambs during induced, graded hypoxia, and the values found were compared to established indicators of poor oxygenation in the fetus, such as oxygen saturation, blood gases, pH, base excess, and lactate. Highly significant correlations were found to all parameters of hypoxia except PaO2. When the duration of hypoxia was taken into account, the HX concentrations showed highly significant correlation to constructed variables of oxygen debt. In multiple correlation analysis, pH turned out as the strongest single variable, explaining 80% of the variance in HX concentration with the remaining parameters increasing the value to 87%. The highest concentrations of HX were obtained when hypoxemia was combined with acidemia or with a large fetomaternal PaCO2-gradient which correlated to a reduced cardiac output in the fetus. These findings appear to corroborate the conclusion that plasma HX concentration reflects tissue hypoxia in the fetal lamb.

Plasma hypoxanthine concentrations in pigs. A prognostic aid in hypoxia

Hypoxemia was induced in pigs by artificial ventilation with 7% oxygen. Death occurred after 21--99 min (mean 48 min). The plasma hypoxanthine and base deficit concentrations increased linearly during hypoxemia and were significantly elevated after 5 min compared to initial values. The correlation between hypoxanthine and base deficit was good (p < 0.001, r = 0.68). The rate of increase of plasma hypoxanthine concentration was correlated with survival time and a significant correlation was found between the negative slope of hypoxanthine increased and survival. Death occurred in all animals when the hypoxanthine concentrations exceeded about 125 mumol/l. These findings indicate that the plasma concentration and the rate of increase of hypoxanthine specifically and sensitively reflect tissue hypoxia.

Hypoxanthine in cerebrospinal fluid in children

In forty-five children the hypoxanthine concentration in cerebrospinal fluid (CSF) was measured (fifty-two samples). In newborn infants (nineteen patients) the hypoxanthine levels were higher in patients with clinical conditions associated with hypoxia (idiopathic respiratory distress syndrome, asphyxia, apneic attacks) than in patients without clinical hypoxia (P less than 0.01). In hypoxic patients the hypoxanthine concentration varied between 5 and 28 mu mol/l. In children outside the neonatal period the hypoxanthine concentration in CSF varied considerably in different diseases. High levels were registered in meningitis prior to treatment, febrile convulsions and in lymphoblastic leukaemia, probably reflecting tissue hypoxia and an increased tissue catabolism.

Post-mortem hypoxanthine levels in the vitreous humour. An introductory report

Post-mortem hypoxanthine levels in vitreous humour were determined in 86 consecutive legal autopsy cases. In cases of sudden death caused by trauma or by myocardial infarction, levels ranging from 0 to 540 mumol/l were found. The mean value was about ten times higher than normal in vivo plasma levels. The hypoxanthine levels seem to be independent of time post-mortem, at least during the first 48 hours. It is known that augmentation of the hypoxanthine plasma, cerebrospinal fluid, and urine levels reflects tissue hypoxia. In the present material no elevation of hypoxanthine levels in the vitreous humour was found in cases of strangulation or suspension, while statistically significant elevation was found in cases of drug intoxication. It is concluded that this may reflect the effect of drug-induced prolonged tissue hypoxia caused by respiratory depression.

Plasma hypoxanthine levels in pigs during acute hypoxemia. A correlation between lactate and base deficit concentrations

Tissue hypoxia was induced in pigs by artificial ventilation with 6% O2 in N2 for 18 min. Base deficit, lactate and hypoxanthine increased linearily during this period, and were significantly higher than initial values in the course of 6 min of hypoxemia. High correlation coefficients between hypoxanthine and lactate (mean 0.98) and between hypoxanthine and base deficit (mean 0.98) were found. During the recovery period when the animals were ventilated with air, high correlation coefficients between lactate and hypoxanthine (mean 0.75) and between base deficit and hypoxanthine (mean 0.83) were also found. It is concluded that plasma hypoxanthine concentrations should be used to assess tissue hypoxia also in clinical situations.

Plasma kallikrein activity and prekallikrein levels during endotoxin shock in dogs

Endotoxin shock (ES) was induced in Labrador retriever dogs by infusion of a lethal dose of Escherichia coli endotoxin. Spontaneous plasma kallikrein activity and prekallikrein levels were determined during subsequent stages of the shock both by an esterolytic assay (BAEe) and a new amidolytic assay utilizing a chromogenic tripeptide derivative (Chromozym PK, Prntapharm AG, Basel Switzerland). During the late stages of shock characterized by a substantial decline of blood pressure, plasma prekallikrein levels determined by the amidolytic assay were considerably reduced. In this phase of the shock both the esterolytic and the amidolytic assays revealed a significant elevation of spontaneous activity. Plasma prekallikrein determined by the esterolytic assay was found to be elevated vs. control values for the whole duration of ES. The findings made seem to associate activation of the plasma kallikrein-kinin system to the circulatory collapse of endotoxin shock in dogs.

Alteration of plasma hypoxanthine concentration during ischaemia in the forelimb of the pig

Ischaemia in the forelimb of pigs was induced by clamping the main artery of an 'isolated leg' preparation. In plasma from the brachial vein the hypoxanthine concentration increased linearly between 10 and 25 min of ischaemia. The average increase in plasma hypoxanthine concentration in ten experiments was 25-0 micromol/1 after 30 min of ischaemia. It is concluded that the plasma hypoxanthine level might be a useful indicator of tissue hypoxia caused by impairment of peripheral blood flow.

Hypoxanthine and urate levels of plasma during and after hemorrhagic hypotension in dogs

The plasma hypoxanthine concentrations increased during hemorrhagic hypotension in dogs. A venous-arterial hypoxanthine difference was found indicating metabolism of hypoxanthine in the lungs. A maximal hypoxanthine level was found during the hypotension, then the level decreased. This probably reflects peripheral vasoconstriction. During reinfusion of the blood, a new hypoxanthine peak was observed. The urate levels also increased during the hypotension. An arterial venous difference was found. This probably illustrates that hypoxanthine is metabolized to urate in the lungs. It is concluded that the increase of plasma hypoxanthine concentrations might reflect tissue hypoxia.

Hypoxanthine levels of plasma during hypoxemia in dogs

Tissue hypoxia was induced in one group of dogs by clamping of the endotracheal tube and in another group by artificial ventilation with a mixture of nitrogen and air. The hypoxanthine concentration of venous and arterial plasma increased significantly during severe hypoxemia. When the hypoxemia was relieved, an increased venous-arterial hypoxanthine difference appeared indicating that the lung metabolism of hypoxanthine was slowed down during alveolar hypoxia. It is concluded that the level of plasma hypoxanthine in dogs during hypoxemia is dependent on the degree of tissue hypoxia, peripheral vasoregulation, and lung metabolism.

The determination of hypoxanthine and xanthine with a PO2 electrode

A simple and rapid method for determination of the hypoxanthine and xanthine concentration in plasma and urine is described. The method is based on the principle that oxygen is consumed quantitatively when hypoxanthine and xanthine are oxidized to urate by xanthine oxidase. By using Henry's law a direct measure of the hypoxanthine and xanthine concentration is obtained. The method determines these oxypurines in volumes of 200 mul in concentrations less than 5 mumol/liter in about 5 min. The average precision in the range of 0-50 mumol/liter is 2.6 mumol/liter. Of the added hypoxanthine, 99-102% is recovered in plasma. Even though xanthine oxidase is a rather nonspecific enzyme, experiments show that this method is highly specific during physiologic conditions.

Hypoxanthine as a measurement of hypoxia

The hypoxanthine concentration in plasma was found to be a sensitive parameter of hypoxia of the fetus and the newborn infant. The plasma level of hypoxanthine in the umbilical cord in 29 newborn infants with normal delivery varied between 0 and 11.0 mumol/liter with a mean of 5.8 mumol/liter, SD 3.0 mumol/liter. Compared with this reference group the hypoxanthine concentration in plasma of the umbilical cord in 10 newborn infants with clinical signs of intrauterine hypoxia during labor was found to be significantly higher, with a range of 11.0-61.5 mumol/liter, with a mean of 25.0 mumol/liter, SD 18.0 mumol/liter. The plasma level of hypoxanthine in two premature babies developing an idiopathic respiratory distress syndrome was monitored. The metabolite was found to be considerably increased, in one of them more than 24 hr after a period of hypoxia necessitating artificial ventilation. The hypoxanthine level in plasma of umbilical arterial blood was followed about 2 hr postpartum in three newborn infants with clinical signs of intrauterine hypoxia. The decrease of the plasma concentration of the metabolite seemed to be with a constant velocity, as it was about 10 mumol/liter/hr in these cases. A new method was used for the determination of hypoxanthine in plasma, based on the principle that PO2 decreased when hypoxanthine is oxidized to uric acid.