Hemodynamic Management in the Adult Respiratory Distress Syndrome

Analytic Reviews : Hemodynamic Management of the Adult Respiratory Distress Syndrome

Hemodynamic management is an essential aspect of the care of patients with adult respiratory distress syn drome (ARDS). On the basis of current knowledge, our proposed goals of management are to maximize pe ripheral oxygen delivery while attempting to minimize further lung damage or dysfunction. The major patho physiologic abnormalities of ARDS are an increased lung vascular permeability, right-to-left intrapulmonary shunting, and pulmonary vascular resistance. These abnormalities must be understood to select the proper therapy. Although all patients with ARDS share these abnormalities, they differ in their associated clinical conditions and underlying cardiovascular status. Be cause each ARDS patient may respond differently to therapy, hemodynamic management must be selected empirically with the goal of therapy as a guide. We have considered available therapeutic options including posi tive end-expiratory pressure, volume depletion, volume expansion, vasopressors, and vasodilators. In the future hemodynamic management of patients with ARDS will likely change as better methods of patient assessment and treatment are developed.

Acute respiratory distress syndrome: diagnosis and management

This review will attempt to put together the voluminous studies and concepts that have been published during the past 25 years following the description of the acute respiratory distress syndrome (ARDS) regarding diagnosis and management. The initial discussion will focus on how to clinically diagnose ARDS based recommendations. This also gives the current definition of acute lung injury and when to call it ARDS. The radiographic and hemodynamic characteristics are discussed including oxygenation parameters. The management outlines the conventional as well as new therapies intended to improve survival of this devastating disease.

The pulmonary circulation in acute lung injury: a review of some recent advances

1. According to the Starling resistor model of the pulmonary circulation, the pulmonary hypertension of oleic acid lung injury, an experimental model close to the early stage of clinical ARDS, primarily results from an increased vascular closing pressure which exceeds Pla and becomes the effective outflow pressure of the pulmonary circulation. Therefore, calculated pulmonary vascular resistance should be interpreted cautiously during haemodynamic investigations in patients with ARDS. 2. Part of this increased vascular closing pressure is functional. During acute lung injury pulmonary vasomotor tone can be reduced by vasodilators, or increased by cyclooxygenase inhibitors and almitrine. 3. Pulmonary vasodilation due to infused vasodilators usually impairs gas exchange in ARDS. 4. There is evidence that HPV is altered during ARDS. Drugs capable of enhancing the efficacy of HPV could improve gas exchange. If proven safe in the future, cyclooxygenase inhibitors and almitrine are interesting compounds to be tested in ARDS.

Increased survival of ARDS patients with severe hypoxemia (ECMO criteria)

The adult respiratory distress syndrome (ARDS) is a form of diffuse lung injury associated with multiple risk factors. Patients with severe hypoxemia who meet blood gas criteria defined by the extracorporeal membrane oxygenation trial (ECMO) of 1974 to 1977 have a reported survival of 11 percent. The reported survival has remained unchanged for 15 years despite numerous technologic advances. We prospectively studied ARDS patients who met ECMO blood gas criteria. One hundred seventy-eight ARDS patients were prospectively screened over a 30-month period. Fifty-one of these patients met ECMO blood gas criteria and 23 (45 percent) survived (p less than 0.001 vs ECMO trial). No obvious differences in etiology, APACHE II score, organ system failure, or the incidence of sepsis was found between survivors and nonsurvivors. We conclude that survival of ARDS patients who met ECMO blood gas criteria in our institution is higher than that previously reported from both other centers and our own hospital.

A retrospective survey of treatment and mortality in aspiration pneumonia

A retrospective survey was conducted of all patients with severe aspiration pneumonitis requiring artificial ventilation in our Intensive Care Unit from 1982-1986 inclusive. Of 38 patients, 8 (21%) died. Five of these deaths were due to severe primary intracranial pathology, and occurred after complete or almost complete resolution of the pneumonitis. One death (2.5%) due to myocardial infarction was possibly related to aspiration, and 2 deaths (5%) were definitely related to aspiration. The 7.5% mortality related to aspiration is considerably lower than in previous clinical studies of severe aspiration pneumonia. There was only one death due to aspiration in patients under the age of 70. The mean arterial to alveolar oxygen tension ratio was 0.221, and the mean predicted mortality by apache II was 43%. Patients were managed with rapid intravascular volume restoration using crystalloid fluids, early ventilation, no steroids, and no immediate antibiotics. We conclude that with such management it is possible to achieve a low hospital mortality in severe aspiration pneumonia, particularly in young patients.