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The Bezold-Jarisch reflex is an eponym for a triad of responses (apnea, bradycardia, and hypotension) following intravenous injection of veratrum alkaloids in experimental animals. The observation was first reported in 1867 by von Bezold and Hirt, and confirmed in 1938-1940 by Jarisch. The triad depends on intact vagi and is mediated through cranial nervous medullary centers controlling respiration, heart rate, and vasomotor tone. The respiratory effects are mediated through pulmonary vagal afferents and the bradycardia and vasodepression through cardiac vagal afferents. The veratrum alkaloids activate all known receptors in the carotid-aortic and cardiopulmonary areas. The cardiopulmonary receptors (baroreceptors, cough receptors, and parenchymal stretch receptors) also respond to other chemical substances: nicotine, capsaicin, venom, antihistaminics, halogenated anesthetics, diguanides, and serotonin (5-hydroxytryptamine). Derivatives of last-mentioned amine activate Type 1, 2, or 3 receptors and have potential therapeutic use. Since several types of cardiopulmonary receptors participate in the Bezold-Jarisch reflex, it has been difficult to develop a blockade to one type of receptor for therapeutic use (cough, bronchospasm, pulmonary hypertension, or coronary vasospasm). Axon reflexes influence pulmonary blood vessels, bronchial blood vessels, and bronchial smooth muscles. These intrapulmonary reflexes need further study as to how they relate to the Bezold-Jarisch reflex in health and disease. The cardiopulmonary and carotid-aortic reflexes can serve as defense mechanisms against chemical hazards that are likely to be inhaled in the workplace and in the environment.

Results of chemical analysis, animal experiments, and human studies are reviewed, criticized, and found not to support claims of an association between workers exposed to environmental tobacco smoke (ETS) and occupational coronary heart disease. This review also recommends refinement of the use of dose surrogates, as presently practiced by the Occupational Safety and Health Administration (OSHA), for regulating indoor emissions from combustion engines, coal furnaces, tobacco leaf processing, rayon viscose manufacturing, and rubber curing. The work standards OSHA uses for regulation of these complex mixtures could also be used in evaluating ETS and relate to the following constituents of ETS: nicotine, carbon monoxide, benzo[a]pyrene, and carbon disulfide. The data indicate that the levels of these substances potentially arising from ETS are many orders of magnitude below their respective PELs. Thus, based on the standards for exposure surrogates for other complex mixtures, the potential worker exposure from ETS does not require further regulation by OSHA, based on cardiovascular disease.

It should be recalled that the seven-center study conducted in the United States was initiated at a time when American physicians had recognized that past attempts to prove efficacy of peripheral vasodilators in treadmill testing had failed. The positive results derived from pentoxifylline treatment are significant because, for the first time, treadmill testing can prove the effectiveness of a hemorheologic drug, such as pentoxifylline, in the treatment of patients with intermittent claudication. Since treadmill testing is regarded as the most objective measurement of therapeutic success in claudicant patients, the positive results can assure us that hemorheologic drugs increasing erythrocyte flexibility are highly desired in treating peripheral vascular insufficiency, such as intermittent claudication.

The acute inhalational toxicity of trichlorofluoromethane (FC 11) is summarized in this paper. There is a striking similarity in threshold concentrations between the mouse and the rat on one hand and the dog and the monkey on the other. The mouse and rat require lower levels of concentration, i.e. (1 to 2.5%) to influence the respiratory system but higher levels (2.5 to 5.0%) to affect the circulatory system. The respiratory systems of the monkey and the dog have about the same sensitivity as those of the other two species in that the threshold level of FC 11 is 2.5 to 5%. The circulatory systems of the monkey and the dog can be influenced by a concentration of 0.5%.

The question as to whether or not the hypotension observed as part of the effect of tricholorofluoromethane (FC11), dichlorofluoromethane (FC 12), dichlorotetrafluoroethane (FC 114) and methyl chloroform was due to a vasodepressor component of action, in addition to the previously documented depression in myocardial contractile force, was answered by testing these agents in an anesthetized dog preparation in which one hind limb was perfused at constant flow through the femoral artery. 5% FC 11, 20% FC 12 and 20% FC 114 decreased vascular resistance of the perfused limb, as reflected by decrease in mean femoral arterial perfusion pressure, in vagotomized but not in intact preparations. Methyl chloroform decreased vascular resistance even in intact preparations. Spontaneous blood flow in the intact femoral artery decreased following FC 11 and methyl chloroform administration in vagotomized preparations and was associated with marked decrease in mean aortic pressure. Blockade of alpha and beta adrenergic receptors with phentolamine and propranolol in the vagotomized preparation had no modifying influence of the effect of FC 11 and methyl chloroform. It may be concluded from this study that FC 11, FC 12 and FC 114 exhibit a vasodepressor activity on skeletal muscle vascular bed which is readily overcome by the hypotension-induced activation of the sympathetic system but which becomes evident when reflex activity is prevented by vagotomy. Methly choloroform exhibits a vasodepressor effect even in intact preparations probably because of concomitant depression of reflex activity through its general anesthetic action. A decrease in spontaneous femoral blood flow following FC 11 and methyl chloroform administration is referable to the accompanying severe hypotension notwithstanding concomitant vascular relaxation. Neither FC 11 nor methly chloroform directly liberate catecholamines from their sites of storage.

The 15 propellants are grouped into four classes on the basis of results of investigation reported in this series of publications. Class 1 low-pressure propellants of high toxicity; Class 2 low-pressure propellants of intermediate toxicity; Class 3 high-pressure propellants of intermediate toxicity; and Class 4 high-pressure propellants of low toxicity.

For many years, Inosine was considered to be a simple metabolite of adenosine which was devoid of any cardiovascular effects. This theoretical ineffectiveness can be explained in the light of recent studies by the use of inadequate doses. In fact, higher doses of inosine, a non-toxic nucleoside, have demonstrated, experimentally, a cardiovascular activity and the pharmacological profile of this naturally occurring substance has been defined. Like adenosine, inosine is a potent coronary vasodilator. The vasodilatation induced by inosine is only partly due to increased metabolic demands. Inosine has a direct action on coronary artery relaxation independent of the inotropic effect. It alters the balance between oxygen supply and demand which is reflected by an intramyocardial redistribution of oxygen in favour of the sub-endocardial zones. Inosine acts on the coronary circulation like a "regulator of myocardial nutrition", unlike adenosine, which can be thought of as a "coronary vasoregulator". This dissociation between the two nucleosides is apparently due to different vascular sites of action. The positive inotropic action of inosine, which has been demonstrated in both healthy and pathological myocardium in all of the experimental animal species studied, is not due to stimulation of the cardiac beta-adrenergic receptors, as beta-blockers do not antagonize the positive inotropic effect of inosine. This increase in myocardial contractile dynamics is evident in infarcted as well as healthy areas of myocardium. The inotropic and coronary vasodilator effects of inosine are not associated with any modification of the chronotropic function. Inosine is not arrhythmogenic, even at high doses. Furthermore, it does not affect atrioventricular conduction. It has been demonstrated that inosine is capable of antagonizing ouabain induced arrhythmias. Various clinical studies confirm the positive inotropic action of inosine, without any alteration in the post-load, the pre-load or the heart rate. The positive inotropic action of inosine can therefore be considered to be selective. Together with these haemodynamic effects, it has been shown that the addition of inosine to cardioplegic solutions improves the functional recovery of the myocardium, by increasing the quantity of energy-rich phosphates. Similar beneficial results have been obtained in renal transplantation, both experimentally and in clinical studies. The mechanism of action of inosine remains unknown. Are the haemodynamic effects of this compound due to its metabolic effects? Are there specific myocardial purinergic receptors? (ABSTRACT TRUNCATED AT 400 WORDS)

Unlike codeine, dextromethorphan does not cause pulmonary vasoconstiction in the anesthetized dog. The other effects of dextromethorphan are as follwos: a rise in pulmonary resistance indicating bronchoconstriction, and increase in pulmonary blood flow relating to a positive inotropic action, and a decrease in aortic blood pressure resulting from systemic vasodilation. These effects are blocked by previous injections of doxylamine, an antihistaminic drug. This interaction suggests a rationale for the combined use of dextromethorphan and doxylamine in the treatment of upper respiratory infection.

The low-pressure propellants influence predominantly the circulation, whereas the high pressure propellants affect the respiration in anesthetized monkeys. There are four groups according to the level of toxicity: Class 1, low-pressure propellants of high toxicity that cause tachycardia and hypotension; Class 2, low-pressure propellants of intermediate toxicity that influence either circulation or respiration or both; Class 3, high-pressure propellants of intermediate toxicity that cause bronchoconstriction; and Class 4, high-pressure propellants of low toxicity that do not influence respiration or circulation even when inhaled at levels of up to 20 percent concentration.

Three propellants were selected for investigation in rats because of their non-uniform effect in mice and monkeys. Trichlorofluoromethane (FC 11) provoked arrhythmia in all three animal species, dichlorodifluoromethane (FC 12) in monkeys and rats but not in mice, and difluoroethane (FC 152a) only in rats. In rats the alterations in heart rate and electrocardiographic pattern during inhalation of these propellants are largely brought about by release of catecholamines from the adrenal gland, because adrenalectomy or prior injection of beta-adrenergic blocking drugs decreased the incidence of cardiac effects. Rats that have pulmonary vascular thrombosis or cardiac necrosis become more sensitive to proarrhythmic activity of these propellants.

The classical idea that selenium is toxic to the heart at levels higher than available in a balanced diet is not supported by experimental work. In mice, treatment with sodium selenite increased the LD50 of ouabain and 2,4-dinitrophenol, and increased the tolerance to nitrogen inhalation. Although sodium selenite had no effect on the dog heart with circulation intact, there was a reduction in coronary vascular resistance in the heart-lung preparation. In the isolated ventricular segment perfused with blood, the administration of sodium selenite caused a positive inotropic effect which appeared even after blockade of beta-adrenergic receptors and in segments perfused with a Krebs-bicarbonate solution that was deficient in oxygen. These results cannot be explained merely as the correction of a selenium deficiency but rather as a positive influence of sodium selenite on the heart that has been acutely stressed by oxygen lack, ouabain, or 2,4-dinitrophenol.

The inhalation of fluorocarbons caused a depression of myocardial contractility, aortic hypotension, a decrease in cardiac output and an increase in pulmonary vascular resistance. The minimal concentrations that elicited these changes are as follows: 1% trichlorofluoromethane (FC11); 2.5% dichlorotetrafluoroethane (FC114); and 10% dichlorodifluoromethane (FC12). Inhalation of 20% octafluorocyclobutane (FC318) and difluoroethane (FC152a) did not influence these hemodynamic parameters. As in previous comparisons, the most widely used aerosol propellants are potentially cardiotoxic in the anesthetized dog.

Physiological and pathophysiological aspects of systemic and cardiac haemodynamics are reviewed with appraisal of Carl J. Wiggers merits and contributions to the research and developments in this field and his early recognition of the significance of the flow properties of blood in impaired circulation. Pharmacological agents involved in treatment of peripheral vascular diseases are discussed with special regard to the haemorheologically active xanthine derivative pentoxifylline. The profile of pentoxifylline as it emerges from experimental pharmacological and clinical studies is presented paying special attention to the haemorheological properties of the drug. Pharmacokinetic features of pentoxifylline are surveyed touching absorption, blood levels, metabolism and excretion aspects. Basing on the available data pentoxifylline is regarded as a promising drug in the treatment of circulatory ischemic disorders, especially in intermittent claudication.

The effects of fluorocarbons and chlorinated solvents on the cardiopulmonary system are reviewed. The new information, not hitherto reported, relates to the antagonistic action of inosine, a naturally occurring nucleoside formed in the body by deamination of adenosine. The effect of inosine on methylene chloride toxicity was investigated in open chest dogs anesthetized with pentobarbital sodium. Methylene chloride (5% in air or 50,000 ppm) elicited a decrease of ventricular contractility represented by the diminished left ventricular (dp/dt)(max) and myocardial contractile force measured directly with a Walton-Brodie strain gauge arch. Coronary blood flow decreased slightly after exposure to methylene chloride. Arterial blood pressure and heart rate did not change. The negative inotropic effect of methylene chloride was reversed or prevented to a substantial extent by intravenous infusion of inosine (5 mg/kg-min). The effect of the latter compound was also characterized by significant coronary vasodilation. It was shown by the experiments that the cardiostimulatory action of inosine was associated with improved hypoxic adaptability of the coronary blood vessels. In contrast, the effect of catecholamines (epinephrine and isoproterenol) was not accompanied by such a beneficial coronary vascular effect. On the basis of these results, the conclusion has been arrived at that inosine might be recommended as a useful antidote in methylene chloride poisoning in particular, and of poisoning by chlorinated solvents and fluorocarbons in general.

The exposure of the upper respiratory tract to aerosol propellants produces apnea, bradycardia, and biphasic fall and rise in aortic blood pressure in anesthetized dogs. This response represents the irritation of sensory receptors in the nasal and nasopharyngeal mucosa and is not elicited with aerosol propellants administered via a tracheal cannula bypassing the upper respiratory tract. When this is done, a different reflex is elicited, consisting of tachycardia that is mediated by the thoracic sympathetic nerves. There is either bronchodilation or bronchoconstriction depending on the type of propellant. The three propellants (11, 12, and 114) widely used in aerosols, when inspired in large doses, elicit both bradycardia and tachycardia and induce bronchoconstriction or bronchodilation. Two additional propellants (115 and C318), which are not ordinarily used to dispense bronchodilator drugs, do not elicit any change in heart rate and produce only bronchodilation. It is suggested that these two propellants merit further investigation and may replace the three widely used ones if these prove the use and abuse of aerosols.

In a patient under general anesthesia, the occurrence of bronchospasm can be readily treated provided the cause is diagnosed early. The corrective drugs to dilate are readily available: atropine, epinephrine and theophylline. In the choice of preanesthetics, anesthetics and adjuvants, it is important to remember that there are differences in the bronchomotor effects; most curareform drugs constrict except pancuronium; most inhalational anesthetics dilate in contrast to intravenous anesthetics. In the event that bronchospasm cannot be re relieved by drugs, intubation and assisted breating can be applied to maintain adequate gas exchange in the alveoli.

The cardiovascular effects of progressively increasing infusions of papaverine hydrochloride, aminophylline and cetiedil, a new vasodilator, were studied and compared in the anesthetized intact dog preparations. Papaverine and aminophylline had qualitatively the same effects on the various parameters, but in general the maximal effects of papaverine were of a greater order of magnitude. Cetiedil exhibited a different pattern of cardiovascular activity characterized by initial decrease in mean pulmonary arterial flow of 16% accompanied by an increase in systemic vascular resistance of 28% and in pulmonary vascular resistance of 19%, a stage of restoration of mean pulmonary arterial flow to control level accompanied by decrease in dp/dt of 25% and increase in pulmonary vascular resistance of 27% and a final stage of decrease in mean pulmonary arterial flow, representing toxic effects and accompanied by decrease in mean aortic pressure of 26%, dp/dt of 54% and heart rate of 27%, and an increase in pulmonary vascular resistance of 84%. These results indicate that cetiedil is devoid of cardiac stimulant activity. In another group of experiments devoted to measurement of vascular resistance of the hind limb, the results indicate that cetiedil, like papaverine and aminophylline, increased femoral blood flow through a decrease in resistance of the hind limb vasculature. This increase in flow could have been brought about only by redistribution of the cardiac output through differential effects on different vascular beds, since unlike papaverine and aminophylline, cetiedil does not increase cardiac output. The lesser maximal increase in femoral blood flow following cetiedil as compared to that following papaverine is probably referable to the relatively limited capacity of redistribution of the cardiac output to augment femoral blood flow. Superimposition of cetiedil and aminophylline on maximal effects of papaverine led to an additional decrease in mean femoral perfusion pressure, probably implying differences in basic mechanisms by which the three agents bring about their smooth muscle relaxant action.

The inhalation of trichlorofluoromethane (FC11), dichlorotetrafluoroethane (FC114) and dichlorodifluoromethane (FC12) caused a reduction in mean aortic blood pressure but only FC11 and FC114 caused a reduction in mean pulmonary arterial pressure. The primary cause of the fall is a decrease in pulmonary blood flow. When blood flow to a lobe is kept constant and the adrenergic alpha receptors are blocked by injection of phentolamine, the inhalation of FC11 caused vasodilation. In the intact circulation, the vasodilation is masked by release of catecholamines which constrict the pulmonary blood vessels.

During the past decade, the effectiveness of peripheral vasodilator drugs in the treatment of chronic occlusive arterial disease has been questioned. Pentoxifylline is a hemorheologic agent with primary actions that include increasing erythrocyte flexibility, reducing blood viscosity and increasing microcirculatory flow and tissue perfusion. The result is improved supply of oxygen to ischemic muscles of the limbs. In several double-blind studies, pentoxifylline increased walking distance of patients with intermittent claudication in comparison to placebo or vasodilators. Like other methylxanthines, pentoxifylline is well absorbed in the gastrointestinal tract, almost completely metabolized in the body and excreted in the urine. The most significant difference in its pharmacokinetics is that, unlike other methylxanthines, it is bound to the erythrocytic membrane where it is initially metabolized. Although pentoxifylline has been shown to be effective in the treatment of intermittent claudication, additional research is needed to determine its use as adjunctive therapy in patients with concurrent coronary or cerebrovascular disease.

In the anesthetized dog, codeine causes a combination of pulmonary vasoconstriction and systemic vasodilation. Pulmonary blood flow is either increased or decreased, relating to a primary stimulation or depression of myocardial contractility. The overall effect is an elevation in pulmonary arterial pressure largely due to vasoconstriction of the pulmonary blood vessels.

Experimental induction of pulmonary emphysema caused an increase in sensitivity of the rat to toxicity from inhalation of propellants. The emphysematous rat showed an exaggerated reduction in pulmonary compliance in response to inhalation of trichlorofluoromethane (FC 11). In emphysematous and non emphysematous rats without anesthesia the inhalation of FC 11 caused tachycardia, arrhythmias and other abnormalities in the electrocardiogram. The tachycardiac response was eliminated by induction of barbiturate anesthesia, which increased the sensitivity of the heart to occurrence of abnormalities in the electrocardiogram in response to inhalation of FC 11 as well as of dichlorodifluoromethane (FC 12) and difluoroethane (FC 152a). The acceleration in heart rate in response to inhalation of FC 11, hypoxia or hypercapnea was prevented by prior treatment with a beta-blocking drug.