CÔNG THỨC TÍNH THỂ TÍCH TRÀN DỊCH MÀNG PHỔI: V (ml)=[16 (mm)x D ]

Abstract

The aim of this study was to establish a practical simplified formula to facilitate the management of a frequently occurring postoperative complication, pleural effusion. Chest ultrasonography with better sensitivity and reliability in the diagnosis of pleural effusions than chest X-ray can be repeated serially at the bedside without any radiation risk. One hundred and fifty patients after cardiac surgery with basal pleural opacity on chest X-ray have been included in our prospective observational study during a two-year period. Effusion was confirmed on postoperative day (POD) 5.9±3.2 per chest ultrasound sonography. Inclusion criteria for subsequent thoracentesis based on clinical grounds alone and were not protocol-driven. Major inclusion criteria were: dyspnea and peripheral oxygen saturation (SpO ) levels ≤92%  and the maximal distance between mid-height of the diaphragm and visceral pleura (DG30 mm). One hundred and thirty-five patients (90%) were drained with a 14-G needle if according to the simplified formula: V (ml)=[16 (mm)x D ] the volume of the pleural effusion was around 500 ml. The success rate of obtaining fluid was 100% without any complications. There is a high accuracy between the estimated and drained pleural effusion. Simple quantification of pleural effusion enables time and cost-effective decision-making for thoracentesis in postoperative patients.

 2010 Published by European Association for Cardio-Thoracic Surgery. All rights reserved.

For ultrasound examination patients were in a sitting position. The ultrasound probe (S5–1, 2.5 MHz, iE33 Philips, Philips, Germany) was moved in a cranial direction in the mid-scapular line. The visceral layer moved during each respiratory cycle with a decrease in interpleural separation during inspiration. The lung behind the pleural effusion appeared either ventilated or consolidated. The maximal distance between mid-height of the diaphragm and visceral pleura (D) was measured after freezing the image in end-expiration (Fig. 2). The diaphragm, liver and spleen had to be clearly visualised before tapping to avoid accidental puncture. An interpleural distance DG30 mm was required to include the patient into the study (Fig. 1). Thoracentesis was performed in the mid-scapular line after previous determination with the probe. All thoracenteses were therapeutic, i.e. aimed at draining the pleural space to a large extent, but to the determined maximum of 2000 ml just to prevent pulmonary oedema. We performed the thoracentesis with a syringe pump system mounted onto the 14 G catheter-over-needle enabling aspiration of the pleural effusion. The volume of fluid (V) was recorded and the tap was terminated when no more fluid could be aspirated. All patients with incomplete aspiration of pleural fluid who had separation of pleural layers of 20 mm on post-puncture ultrasound were excluded from the study. A chest X-ray was performed in all patients after thoracentesis.

Discussion

In the presented study our goal was to establish a practical algorithm by formulating a simplified calculation to facilitate the management of a frequently occurring postoperative complication, pleural effusion. It is generally accepted that chest ultrasonography shows better sensitivity and reliability in the diagnosis of pleural effusions than chest X-ray w1, 2x. Chest ultrasonography can be repeated serially at the bedside without any radiation risk. Modern miniaturized advanced ultrasound systems are portable, allowing physicians to quickly perform rapid diagnostics and thoracentesis right at a patient’s bedside, ideal for emergency situations. The advantage of ultrasound evaluation of pleural effusion is obvious w3, 6, 7x: it helps to quantify the pleural fluid volume using our simplified formula V(ml)sw16=D (mm)x and hence helps in deciding whether or not thoracentesis should be performed. The complication rate in this study was zero, specifically no pneumothorax was noted. The major advantage of thoracentesis per tapping with a 14-G needle is in its minimal invasiveness without a need of skin incision, as being required by aformal chest tube or Seldinger Chest Drainage Kit Portex[1]type. On the other hand, patients are not immobilized after thoracentesis with the method presented in this study.

The authors excluded small pleural collections by excluding patients with pleural separation -30 mm on initial ultrasound examination. It was also suggested that the relationship may not be as linear and clinically important for pleural separations below 20 mm w8–10x. One potential source of error for volume underestimation was lower lobe atelectasis with large effusions over 1000 ml, which may lead to different volume ‘morphology’ not amenable to quantification w2x. Sonographic measurement is also influenced by the size of thoracic cavity. In large thoraces in tall people, the layer measured by ultrasound may cause underestimation of the actual volume of pleural fluid. The results could also be influenced by the examination technique: the transducer must not be angled or tilted, which may result in a scan that is oblique to the transverse plane.

Such measurement may produce overestimation of the effusion width. Finally, few limitations of this study should be mentioned. The small number of the patients could be one of them but on the other side the derived formula is highly accurate, justifying the chosen patient collective. Of course a high intra- and interobserver variability of the performed ultrasonographic measurement may exist accentuating the need for some expertise in ultrasonography.

Conclusion

For bedside decisions practical algorithms, like our presented management of postoperative pleural effusions are beneficial. With our simplified formula we could easily quantify pleural effusion and could decide cost and time effectively whether or not to perform a thoracentesis.

Thoracentesis of pleural effusions G500 ml in patients following cardiac surgery under ultrasound guidance proved to be a safe procedure, and improved postoperative respiration and recovery, and shortened the postoperative stay.

E. Usta et al. / Interactive CardioVascular and Thoracic Surgery 10 (2010) 204–207

CLOTBUST-HF: Hands-Free Ultrasound and tPA in Acute Stroke

Sue Hughes

October 25, 2013

 

Intracranial ultrasound treatment using an operator-independent device together with tissue plasminogen activator (tPA) in stroke patients appears to be safe and produced promising recanalization rates, a new study has shown.

The study, published online in Stroke on October 24, was led by Andrew D. Barreto, MD, University of Texas Health Science Center at Houston.

He explained to Medscape Medical Newsthat ultrasound therapy causes the meshwork of fibrin strands within the clot to disperse, thereby allowing better access of tPA to the clot. "We are particularly targeting patients who have clots that are not likely to lyse completely with tPA — those with moderate to severe strokes," Dr. Barreto noted.

"Many smaller studies have been performed with transcranial ultrasound and it does seem to have efficacy in helping to dissolve the clot," he said.
The most cited study is the original CLOTBUST (Combined Lysis of Thrombus in Brain Ischemia With Transcranial Ultrasound and Systemic TPA) study published in 2004 in the New England Journal of Medicine, which showed a recanalization rate of 38% with the combination of ultrasound and tPA vs 13% for those given tPA alone.

However, Dr. Barreto noted that delivery of ultrasound via cranial bone windows requires training for both anatomic localization and waveform recognition, which is considered impractical for large-scale use. "As you have to hold the ultrasound device at the same time as identifying the clot, it is too difficult to train enough people to perform the procedure as an emergency bedside therapeutic," he said.

"Mass expansion of properly trained technicians or clinicians to provide 24/7 stroke coverage to complete a pivotal clinical trial of sonothrombolysis represents a major hurdle," the researchers write in the Strokepaper.

Operator-independent transcranial stroke treatment device. Source: The investigators.

"To that end, the development of an operator-independent device that can target the proximal intracranial arteries without specialized neurovascular ultrasound training would make a large-scale, phase 3 clinical trial feasible," they add.

Hands-Free Device

Such a "hands-free" device has now been manufactured by Cerevast Therapeutics, and the current study represents the first-ever exposure of patients with acute stroke to a combination of tPA and this hands-free ultrasound device. "This device has been manufactured so that it can be used without special training and be applied to all stroke patients by just placing it on their heads," Dr. Barreto said.

"It is battery powered and easy to fit. One size fits all, with an adjustable head size and ear position," he explained. "It has been designed so that the probes are positioned in the areas of thinnest bone of the skull: 6 probes on the left and 6 on the right. The device rotates and sequentially fires each probe, thus targeting all the areas of the brain where a large blood clot would be."

For the current study, known as CLOTBUST-Hands Free (CLOTBUST-HF), 20 stroke patients with a median National Institutes of Health Stroke Scale score of 15 received standard-dose intravenous tPA, along with 2-MHz pulsed-wave ultrasound therapy delivered by the CLOTBUST-HF device used for 2 hours.

Sites of occlusion were middle cerebral artery in 14 patients, terminal internal carotid artery in 3 patients, and vertebral artery in 3 patients. All patients tolerated the entire 2 hours of ultrasound treatment, and none developed symptomatic intracerebral hemorrhage. No serious adverse events were related to the study device.

40% Recanalization Rate

At 2 hours, 40% of patients had complete recanalization and 10% had partial recanalization. Middle cerebral artery occlusions demonstrated the greatest complete recanalization rate at 57%. At 90 days, 5 patients (25%) had an excellent outcome, defined as a modified Rankin scale score of 0 to 1.

"The recanalization rate of 40% is in line with that shown in the NEJM paper. But we did not have a control group in this study," Dr. Barreto commented. "At day 90 we had a lower percentage of patients with an excellent outcome than in the previous study, but we only had 20 patients so it is difficult to say much about a clinical outcome."

"This is just a pilot study looking at safety of delivering ultrasound treatment to different areas of the brain. We didn't see any safety issues and the results definitely suggest the approach is feasible," he added.

A phase 3 trial — CLOTBUST-ER — is now underway with the hands-free device. The trial is being conducted in 830 patients from 14 countries, with results expected in 2 to 3 years.