Ultrasound estimation of volume of pleural fluid in mechanically ventilated patients.
OBJECTIVE
The aim was to develop a practical method for estimation of the volume of pleural effusion using ultrasonography in mechanically ventilated patients.


METHODS
Prospective observational study.


METHODS
20-bed general intensive care unit in the university hospital.


METHODS
81 patients were included after initial suspicion of pleural fluid on chest supine X-ray and pre-puncture ultrasound confirming effusion. Patients with thoracic deformities, post-lung surgery, with diaphragm pathology, haemothorax, empyema and with incomplete aspiration of pleural fluid on post-puncture ultrasound were excluded.


METHODS
Patients were supine with mild trunk elevation at 15 degrees . Probe was moved upwards in posterior axillary line, and transverse section perpendicular to the body axis was obtained with pleural separation visible at lung base. The maximal distance between parietal and visceral pleura (Sep) in end-expiration was recorded. Thoracentesis was performed at previous probe position and volume of pleural fluid (V) recorded.


RESULTS
92 effusions were evaluated and drained; 11 (12%) were excluded for incomplete aspiration. Success rate of obtaining fluid under ultrasound guidance was 100%; the incidence of pneumothorax or bleeding was zero. Mean Sep was 35+/-13 mm. Mean V was 658+/-320 ml. Significant positive correlation between both Sep and V was found: r=0.72; r(2)=0.52; p<0.001. The amount of pleural fluid volume can be estimated with the simplified formula: V (ml)=20 x Sep (mm). Mean prediction error of V using Sep was 158.4+/-160.6 ml.


CONCLUSIONS
Easy quantification of pleural fluid may help to decide about performing thoracentesis in high-risk patients, although thoracentesis under ultrasound guidance appears to be a safe procedure.
Balik
M
M
Department of Anaesthesiology and Intensive Care, University Hospital Kralovske Vinohrady, Šrobárova 50, 10034, Prague 10, Czech Republic. balik@fnkv.cz.|Department of Intensive Care, Westmead Hospital, NSW 2145, Westmead, Australia. balik@fnkv.cz.
Plasil
P
P
Department of Anaesthesiology and Intensive Care, University Hospital Kralovske Vinohrady, Šrobárova 50, 10034, Prague 10, Czech Republic.
Waldauf
P
P
Department of Anaesthesiology and Intensive Care, University Hospital Kralovske Vinohrady, Šrobárova 50, 10034, Prague 10, Czech Republic.
Pazout
J
J
Department of Anaesthesiology and Intensive Care, University Hospital Kralovske Vinohrady, Šrobárova 50, 10034, Prague 10, Czech Republic.
Fric
M
M
Department of Anaesthesiology and Intensive Care, University Hospital Kralovske Vinohrady, Šrobárova 50, 10034, Prague 10, Czech Republic.
Otahal
M
M
Department of Anaesthesiology and Intensive Care, University Hospital Kralovske Vinohrady, Šrobárova 50, 10034, Prague 10, Czech Republic.
Pachl
J
J
Department of Anaesthesiology and Intensive Care, University Hospital Kralovske Vinohrady, Šrobárova 50, 10034, Prague 10, Czech Republic.
D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010996:Pleural Effusion / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D012121:Respiration, Artificial; D014463:Ultrasonography; D012122:Ventilators, Mechanical