Acute poisoning with Anthio is associated with a gradual drop of blood pressure in the greater circulation and the development of intensive metabolic acidosis, despite normoxia still observed in the arterial blood and a somewhat increased oxygen capacity of the blood, this indicating mitochondrial injury and disordered tissue respiration.

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We studied the effects of acute hypoxia on hemodynamics and respiration in cats. The animals were divided into high-, low-and medium-resistant to hypoxia by the time of respiratory arrest after breathing with 3% 02 gas mixture. In high-resistant animals, hemodynamic indices remained at a high level throughout the hypoxic episode, while in low-resistant cats they decreased shortly after the onset of hypoxia. It is suggested that the peculiarities of hemodynamic regulation play an important role in individual resistance to acute hypoxia. Key Words: acute hypoxia; hemodynamics; respiration; individual resistance to hypoxia, ultrasound techniquesRecent studies have confirmed the existence of individual, apart from species-specific sensitivity to hypoxia. Special normobaric and hypobaric tests make it possible to classify the animals as high-(HR), medium-(MR) and low-resistant (LR) to hypoxia [1][2][3]6,9]. Biochemical studies showed that animals with different resistance to hypoxia differ not only in parameters of energy, lipid, and carbohydrate metabolism [2,6], but also in the functional characteristics of hemodynamic regulation. However, complex analyses of cardiovascular resistance to different variants of hypoxia have not yet been performed.The aim of this study was to investigate the effect of acute hypoxic hypoxia on hemodynamics and respiration in HR, MR, and LR animals. MATERIALS AND METHODSAcute experiments were carried out on 35 male and female cats (1.8-4.4 kg) anesthetized with Nembutal with an ultrasound technique. Blood pressure in the femoral and pulmonary arteries (BP) was measured with an electric manometer [7]. Ultrasonic transducers were placed on the corresponding vessels during open thorax surgery under conditions of artificial ventilation (AV), then the tissues were sutured, and the animal was switched to natural ventilation. Respiratory movements were recorded with a strain transducer. The recorded indices were analyzed on line with a microcomputer to calculate total peripheral and pulmonary vascular resistance, heart rate (HR), stroke volume, and cardiac index. Changes in the cerebral blood supply were analyzed in 8 experiments. The linear and volume blood flow velocities in the common carotid and internal maxillary arteries were studied using miniature ultrasonic transducers with an inner diameter of 1.5 and 0.5 ram. In some experiments the arterial gasses were analyzed according to the method of Astroup--Ziggard--Andersen.Individual resistance to hypoxia was measured by the time from the onset of respiration with 3% O z in nitrogen to respiratory arrest (apnea). Then the gas flow was stopped for 2-3 rain. was discontinued and the recovery of respiration was awaited for the following 2-3 min. If spontaneous respiration did not recover, the animals were ventilated artificially until the appearance of spontaneous inspirations.0007 -4888/99/0009-0906522.00 ~ Kluwer Academic/Plenum Publishers

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It is shown that general anesthesia strongly influences the resistance of animals to poisoning with organophosphorus compounds (OPC) such as Anthio, weakens compensatory/adaptive responses, and possibly acts synergistically with OPC in impairing tissue respiration. One to three days after peroral administration of Anthio, reduced oxygen tension in arterial blood and increased heart and respiratory rates were recorded in cats, although the arterial blood pressure tended to drop markedly. Anthio poisoning led to profound changes in the autonomic regulation of functions, which was manifested in sharply decreased parasympathetic influences. The function of the brain's GABA-ergic system did not change appreciably. Key Words: cats; anesthesia; organophosphorus compounds; acute poisoning; Anthio pesticideWe found previously that almost all cats die 2-3 h after their acute experimental poisoning in the pentobarbital-anesthetized state with the organophosphorus pesticide Anthio given per os in a dose equal to 20% of its LDs0 value [15]. Such an effect of Anthio is not consistent with what is known about the systemic toxicity displayed by it at this dose level and raises the question of the role pentobarbital anesthesia might play in aggravating the adverse effects of acute experimental poisoning.The present study was designed to examine the impact of pentobarbital anesthesia on major parameters of respiration and systemic circulation several days after peroral administration of Anthio to alert cats in the dose indicated above. In such cats we also evaluated the effect of atropine, which is usually employed in cases of poisoning with cholinestInstitute of General Pathology and Pathological Physiology, Russian Academy of Medical Sciences, Moscow. {Presented by I. P. Ashmarin, Member of the Russian Academy of Medical Sciences) erase blockers, as well as the effect from the activation of the GABA-ergic system, which is closely associated with the cholinergic system [12]. MATERIALS AND METHODSThe experiments were conducted on 7 random-bred adult cats of both sexes weighing 2.2-2.8 kg. Under mild ether anesthesia, the animals were administered intragastrically, via a catheter, the organophosphorus pesticide Anthio (Formothion, Sandoz) in the form of an emulsion in a dose of 1/5 of the LDs0, after which the ether supply was discontinued. Several days later, the cats were anesthetized with sodium pentobarbital (40 mg/kg intraperitoneally) and prepared for examination. Details of this preparation and of the procedures used to measure parameters of respiration, systemic hemodynamics, and arterial blood are described in our previous article [15]. Five cats were injected intravenously with atropine (0.5 mg/kg) and with