Contrast harmonic imaging improves the evaluation of left ventricular function in ventilated patients: comparison with transesophageal echocardiography.

AIMS: The study examined the value of contrast echocardiography (CE) in the assessment of left ventricular (LV) wall motion in ventilated patients in comparison with transesophageal (TOE) and standard fundamental transthoracic imaging (SE). METHODS: Transthoracic echocardiograms were done in 40 ventilated patients. Wall motion was evaluated using the recommendations of the American Society of Echocardiography on SE, CE and TOE. A visualization score was assigned on a scale of 2-0 for each of 16 segments. The segment was assigned a value of 2 if the segment was seen in both systole and diastole, 1 if seen only in systole or diastole, and 0 if not seen at all. A confidence score was also given for each segment with each technique (unable to evaluate; not sure; sure). The ejection fraction (EF) was estimated visually for each technique, and a confidence score was also applied to the EF. RESULTS: Visualization score 0 was present in 6.2 segments/patient on SE, 1.2 on CE (P<0.0001) and 1.1 on TOE (P<0.0001). An average of 6.5 segments were read with surety on SE, 11.5 on CE (P<0.0001) and 12.3 on TOE ( P<0.0001 ). There was no significant difference for CE vs TOE. EF was uninterpretable in 32% on SE, 0% on CE (P<0.001 and 0% on TOE (P<0.001). The EF was read with surety in 53% of patients on SE, 88% on CE (P < 0.0001) and 93% with TOE (P<0.0001) with no difference for CE vs TOE. Thus, wall motion was seen with more confidence on CE and TOE. CONCLUSIONS: In the ventilated patients with suboptimal transthoracic echocardiograms for the evaluation of the LV function, CE provides image quality of regional and global LV function similar to that achieved with TOE echocardiography.

Hemodynamic responses to successful weaning from mechanical ventilation after cardiovascular surgery.

Weaning from mechanical ventilation is usually associated with an increase in oxygen consumption (VO2), which may stress the cardiovascular system. We studied relative changes in the cardiac index and oxygen extraction ratio (EO2) during successful weaning in patients after cardiac surgery (n = 52), cardiac transplantation (n = 17), or abdominal aortic surgery (n = 11). Cardiac index was determined by the thermodilution technique and arterial and mixed venous blood gases were obtained before and 30 min after the start of weaning through a T-piece. The cardiovascular changes were evaluated in 42 patients in whom VO2 (calculated by Fick's equation) increased by more than 10%. Cardiac index increased more after abdominal aortic surgery (from 3.27 +/- 0.77 to 4.44 +/- 0.581 min(-1) m(-2), p < 0.01) than after cardiac surgery (from 2.53 +/- 0.59 to 2.87 +/- 0.46 1 min(-1) m(-2), p < 0.01) or cardiac transplantation (from 2.99 +/- 0.64 to 3.33 +/- 0.741 min(-1) m(-2), p < 0.05). EO2 remained stable in patients after aortic surgery (from 25.9 +/- 7.1 to 25.2 +/- 5.6 %, NS) but increased slightly after cardiac surgery (from 33.3 +/- 6.1 to 37.3 +/- 6.4%, NS) and significantly after cardiac transplantation (from 25.8 +/- 4.1 to 28.2 +/- 4.0%, p < 0.05). Hence the cardiovascular response to weaning from mechanical ventilation may vary according to the type of surgery.