Changes in intrathoracic fluid volumes during weaning from mechanical ventilation in patients after coronary artery bypass grafting.
OBJECTIVE
Although it is known that weaning from mechanical ventilation is associated with alterations in intrathoracic pressure, lung volume, and venous return, changes in intrathoracic fluid volumes during weaning are not reported. Especially in patients with impaired cardiac function, the development of pulmonary edema during weaning has been described. Thus, we investigated changes in intrathoracic fluid volumes in patients after coronary artery bypass grafting after changing the ventilatory pattern from mechanical to spontaneous ventilation.


METHODS
Intrathoracic blood volume index (ITBVI), pulmonary blood volume index (PBVI), and extravascular lung water (EVLW) were calculated during mechanical ventilation (T1), T-piece breathing (T2), and spontaneous breathing after extubation of the trachea (T3) in 72 consecutive patients after coronary artery bypass grafting using a combined dye-thermal dilution method.


RESULTS
Changing from mechanical ventilation to T-piece breathing resulted in an increase in ITBVI from 880 +/- 22 mL/m2 to 970 +/- 22 mL/m2 (P < .01), and in PBVI from 162 +/- 6 mL/m2 to 173 +/- 6 mL/m2 (P < .01). After extubation of the trachea, both parameters decreased again (ITBVI, 879 +/- 20 mL/m2; PBVI, 160 +/- 7 mL/m2). EVLW remained unchanged after transition to T-piece breathing (T1, 5.8 +/- 0.3 mL/kg; T2, 6.0 +/- 0.3 mL/kg), but increased to 6.6 +/- 0.5 mL/kg (P < .01) after extubation of the trachea. However, pathological values of EVLW were not observed.


CONCLUSIONS
In patients after coronary artery bypass grafting, changes in intrathoracic intravascular fluid volumes during weaning are restricted to the period of T-piece breathing and reflect an increased venous return. The maintenance of EVLW in the normal range during weaning indicates that cardiac function was matched to this elevated preload.
Schmidt
H
H
Department of Anesthesiology, University of Heidelberg, Germany.
Rohr
D
D
Bauer
H
H
Böhrer
H
H
Motsch
J
J
Martin
E
E
D001810:Blood Volume; D001026:Coronary Artery Bypass; D015633:Extravascular Lung Water; D005260:Female; D018495:Fluid Shifts; D006439:Hemodynamics; D006801:Humans; D008168:Lung / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011654:Pulmonary Edema / Q000209:etiology; D013815:Thermodilution; D015300:Ventilator Weaning / Q000009:adverse effects*