Patholphysiology of asthmatic bronchoconstriction

Future directions in asthma therapy. Is a cure possible?

Asthma correctly is characterized as a syndrome rather than a disease, because a single causative mechanism has not yet been defined. This lack of definition makes the search for a cure extremely complex. Until a common pathogenetic link is identified, the possibility of a cure is remote. The precise nature of the inflammatory response in asthma has not been defined, and current concepts of the pathogenesis of asthma represent, to some extent, a reductionistic approach to a process that has been seen variously as an allergic reaction, autonomic hyperresponsiveness, or both. Additional evidence of the polygenomic nature of the disease and the inability to define a specific pathogenetic process linked to a final common pathway suggest that gene therapies probably will not be feasible, at least for the near future. As expected, most approaches now being developed are directed toward improved therapies, and optimal treatment may obviate the need to develop complex therapies effecting a cure. Under any circumstance, the notion of a cure will have to await a more comprehensive understanding of the syndrome known as human asthma. This article is intended to provide provocative insights into the reasons why a cure remains elusive.

Care of the asthmatic oral and maxillofacial surgery patient

It is estimated that asthma affects 6 to 9 million people in the United States. The nature of this disease makes it a special concern to the oral and maxillofacial surgeon. Appropriate management of the asthmatic patient with regard to anesthesia and surgical procedures of the oral and maxillofacial region is discussed.

Intravenous magnesium sulfate in the management of acute respiratory failure complicating asthma

IV magnesium sulfate was administered to a 72-year-old man with acute respiratory failure secondary to a severe asthma attack. The patient had clinically deteriorated despite aggressive standard treatment and evidenced acidosis and hypercarbia by arterial blood gas determination. An IV dose of 1 g MgSO4 produced rapid clinical and arterial blood gas improvement and enabled management of the patient without endotracheal intubation and mechanical ventilation. This is the first reported case of the use of IV MgSO4 to prevent intubation and assisted ventilation in a patient with acute respiratory failure complicating asthma.

Endogenous regulation of bronchomotor tone

Airway smooth muscle responses are elicited in a complex manner through a large variety of endogenous mediators. Mediators augment or inhibit bronchomotor tone at a variety of sites through numerous different mechanisms. Interactions occur among mediators and nerves, muscle, and circulating blood elements or respiratory mast cells. Airway smooth muscle tone further is regulated by postsynaptic mediator-mediator interactions. Substances may circulate through the blood from distal sites to reach their target organ, as with epinephrine in its effects on airway smooth muscle, or may be secreted directly onto airway smooth muscle, as with the secretory products of respiratory mast cells. Recent observations have indicated that some mediators elicit airway contraction at least in part by activating efferent parasympathetic nerves and/or platelets. Direct secretion of minute quantities of mediators from adjacent epithelium or from infiltrating leukocytes may be an essential component of airway hyperreactivity. Complex interactions between the complement and kallikrein cascades have been cited as possible mechanisms of airway hyperresponsiveness. Ultimately, bronchomotor tone is mediated postsynaptically by the availability of calcium to the contractile apparatus of the smooth muscle cell. A role for the phosphoinositide system in membrane transduction and for cyclic adenosine monophosphate in regulating calcium distribution for smooth muscle contraction has been implicated. Mediator-mediator interactions distal to the synaptic cleft have been shown to augment both force and duration of airway smooth muscle contraction in a synergistic fashion. The stimuli eliciting mediator and neurotransmitter secretion, their physiologic significance, and the homeostatic infrastructure of these interactions are areas of promising investigation that require further definition.