Study objective: To assess the influence of fiberbronchoscopic alveolar lavage on hemodynamics, right ventricular function, and plasma atrial natriuretic peptide (ANP) concentrations in critically ill, mechanically ventilated patients.
Design: Prospective investigation.
Setting: Eight-bed ICU of a university hospital.
Patients: Fourteen patients with cardiovascular instability due to a systemic inflammatory response syndrome who were mechanically ventilated.
Interventions: Fiberbronchoscopic alveolar lavage after fluid replacement, deep sedation, and paralyzation. Intervention time: 10 min. After inspection of the endobronchial system, one lavage of 40 mL sterile saline solution was instilled in each lung and recovered.
Measurements and results: The fiberbronchoscopic procedure induced a prompt increase in mean pulmonary arterial pressure after 3 min (median[range]: 25 [13 to 39] to 30 [19 to 45] mm Hg, p < 0.05), which increased further after 6 min (34 [17 to 46] mm Hg, p < 0.01). Cardiac index increased simultaneously (4.25 [3.1 to 5.7] to 4.85 [4.3 to 6.9] L/min.m2 after 6 min, p < 0.01), whereas mean arterial pressure and heart rate remained unchanged. Central venous pressure rose from 12 (3 to 18) mm Hg before procedure to 14 (4 to 20) mm Hg after 6 min (p < 0.01). The right ventricular function was measured using a "fast response" ejection fraction thermodilution catheter: end-diastolic volume increased (238 [137 to 358] to 280 [150 to 4ll] mL after 9 min, p < 0.05), as well as stroke volume (88 [54 to 113] to 103 [67 to 153] mL after 9 min, p < 0.01). Right ventricular ejection fraction (37 [25 to 50] %) did not change significantly during the procedure, but the stroke work index was reinforced (8.2 [4.7 to 15.7] to 13.3 [2.4 to 41.3] gm.M/M2 after 6 min, p < 0.01). Plasma c-ANP concentration rose from 135 (24 to 350) to 196.5 (44 to 830 pg/ml after 20 min (p < 0.05). Systemic vascular resistance decreased from 533 (390 to 1,042) to 429 (281 to 684) dynes.s/cm5 after removal of the bronchoscope (p < 0.01).
Conclusions: Although acute pulmonary hypertension was observed during the fiberbronchoscopic procedure, the right ventricular performance did not deteriorate in hemodynamically unstable patients. To maintain a "hyperdynamic cardiovascular state," the right ventricular stroke work was reinforced, presumably by the "Frank-Starling mechanism." We assume that the acute distention of the right side of the heart resulted in elevated ANP concentrations. The marked decrease in systemic vascular resistance might be due to high ANP levels.