Echocardiography: a help in the weaning process.
BACKGROUND
To evaluate the ability of transthoracic echocardiography (TTE) to detect the effects of spontaneous breathing trial (SBT) on central hemodynamics and to identify indices predictive of cardiac-related weaning failure.


METHODS
TTE was performed just before and at the end of a 30-min SBT in 117 patients fulfilling weaning criteria. Maximal velocities of mitral E and A waves, deceleration time of E wave (DTE), maximal velocity of E' wave (tissue Doppler at the lateral mitral annulus), and left ventricular (LV) stroke volume were measured. Values of TTE parameters were compared between baseline (pressure support ventilation) and SBT in all patients and according to LV ejection fraction (EF): >50% (n = 58), 35% to 50% (n = 30), and <35% (n = 29). Baseline TTE indices were also compared between patients who were weaned (n = 94) and those who failed (n = 23).


RESULTS
Weaning failure was of cardiac origin in 20/23 patients (87%). SBT resulted in a significant increase in cardiac output and E/A, and a shortened DTE. At baseline, DTE was significantly shorter in patients with LVEF <35% when compared to other subgroups (median [25th-75th percentiles]: 119 ms [90-153]; vs. 187 ms [144-224] vs. 174 ms [152-193]; P < 0.01) and E/E' was greater (7.9 [5.4-9.1] vs. 6.0 [5.3-9.0] vs. 5.2 [4.7-6.0]; P < 0.01). When compared to patients who were successfully weaned, those patients who failed exhibited at baseline a significantly lower LVEF (36% [27-55] vs. 51% [43-55]: P = 0.04) and higher E/E' (7.0 [5.0-9.2] vs. 5.6 [5.2-6.3]: P = 0.04).


CONCLUSIONS
TTE detects SBT-induced changes in central hemodynamics. When performed by an experienced operator prior to SBT, TTE helps in identifying patients at high risk of cardiac-related weaning failure when documenting a depressed LVEF, shortened DTE and increased E/E'. Further studies are needed to evaluate the impact of this screening strategy on the weaning process and patient outcome.
Caille
Vincent
V
Réanimation Médicale, CHU Ambroise Paré, 9 avenue Charles-de-Gaulle, 92104 Boulogne, France. vincent.caille@apr.aphp.fr
Amiel
Jean-Bernard
JB
Charron
Cyril
C
Belliard
Guillaume
G
Vieillard-Baron
Antoine
A
Vignon
Philippe
P
D000368:Aged; D002302:Cardiac Output; D004452:Echocardiography; D005260:Female; D005602:France; D006439:Hemodynamics; D006785:Hospitals, University; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012119:Respiration; D015300:Ventilator Weaning / Q000379:methods*