Effect of CPAP during cardiopulmonary bypass on postoperative lung function. An experimental study

BACKGROUND

Respiratory failure secondary to cardiopulmonary bypass (CPB) remains a major complication after cardiac surgery. We tested the hypothesis that post-CPB lung function impairment can be prevented by continuous positive airway pressure (CPAP) applied during the CPB.

METHODS

In 6 pigs, CPAP with 5 cmH2O pressure was applied during CPB. Six other pigs served as control, i.e. the lungs were open to the atmosphere during CPB. After median sternotomy, the right atrial appendage as well as the ascending aorta were cannulated. The total CPB duration was 90 min with 45 min cardioplegic arrest. Ventilation-perfusion distribution was measured with the multiple inert gas elimination technique and atelectasis by CT-scanning.

RESULTS

Large atelectasis appeared after CPB, corresponding to 14.5% +/- 5.5 (percent of the total lung area) in the CPAP group and 18.7% +/- 5.2 in the controls (P = 0.20). Intrapulmonary shunt increased and PaO2 decreased after the CPB in both groups.

CONCLUSIONS

We conclude that in this pig model post-CPB atelectasis is not effectively prevented by CPAP applied during CPB.

[Value of 3D CT in diagnosis and treatment of fractures of the tibial plateau]

A precise classification and an optimal understanding of tibial plateau fractures are the basis of a conservative treatment or adequate surgery. The aim of this prospective study is to determine the contribution of 3D CT to the classification of fractures (comparison with standard X-rays) and as an aid to the surgeon in preoperative planning and surgical reconstruction. Between November 1994 and July 1996, 20 patients presenting 22 tibial plateau fractures were considered in this study. They all underwent surgical treatment. The fractures were classified according to the Müller AO classification. They were all investigated by means of standard X-rays (AP, profile, oblique) and the 3D CT. Analysis of the results has shown the superiority of 3D CT in the planning (easier and more acute), in the classification (more precise), and in the exact assessment of the lesions (quantity of fragments); thereby proving to be of undeniable value of the surgeon.

CT-guided methylene-blue labelling before thoracoscopic resection of pulmonary nodules

OBJECTIVE

Evaluation of the efficiency of our technique of methylene-blue labelling of pulmonary nodules to facilitate thoracoscopic recognition and excision.

DESIGN

Patients with a peripheral pulmonary nodule smaller than 2.5 cm and not in contact with the visceral pleura were included. Under tomodensitometric guidance, the nodules were labelled with methylene-blue within hours before thoracoscopic wedge resection. If frozen section revealed a primary bronchial carcinoma, thoracotomy and classical resection were performed during the same anesthesia.

RESULTS

Between July 1992 and August 1996, 54 nodules were removed in 51 patients. Labelling was performed between 75 and 270 min before surgery and was complicated in 13 patients (25.4%) by a small pneumothorax without any clinical consequence. Labelling allowed successful thoracoscopic recognition of 50 nodules (92%) and thoracoscopic wedge resection was possible in all but one cases (91%). Five patients (9%) required thoracotomy. Histology showed a benign lesion in 22 cases, a primary lung carcinoma in 17 and a metastases in 15. Twenty of the 22 benign nodules (91%) were removed without thoracotomy. According to the protocol, 13 patients with a primary lung tumour underwent lobectomy during the same session. There was no mortality nor morbidity amongst patients who had thoracoscopy only.

CONCLUSIONS

Our technique of labelling peripheral pulmonary nodules with methylene-blue is very effective and is not associated with any relevant complication. Thoracoscopic excision and diagnosis is possible in more than 90% of the cases. We therefore recommend this simple, low-cost and reliable technique for nodules not in contact with the visceral pleura before thoracoscopic wedge resection.

Spiral CT aortography: an efficient technique for the diagnosis of traumatic aortic injury

The objective of this study was to assess the efficiency of spiral CT (SCT) aortography for diagnosing acute aortic lesions in blunt thoracic trauma patients. Between October 1992 and June 1997, 487 SCT scans of the chest were performed on blunt thoracic trauma patients. To assess aortic injury, the following SCT criteria were considered: hemomediastinum, peri-aortic hematoma, irregular aspect of the aortic wall, aortic pseudodiverticulum, intimal flap and traumatic dissection. Aortic injury was diagnosed on 14 SCT examinations (2.9 %), five of the patients having had an additional digital aortography that confirmed the aortic trauma. Twelve subjects underwent surgical repair of the thoracic aorta, which in all but one case confirmed the aortic injury. Two patients died before surgery from severe brain lesions. The aortic blunt lesions were confirmed at autopsy. According to the follow-up of the other 473 patients, we are aware of no false-negative SCT examination. Our limited series shows a sensitivity of 100 % and specificity of 99.8 % of SCT aortography in the diagnosis of aortic injury. It is concluded that SCT aortagraphy is an accurate diagnostic method for the assessment of aortic injury in blunt thoracic trauma patients.

Repeated vital capacity manoeuvres after cardiopulmonary bypass: effects on lung function in a pig model

Respiratory failure following cardiopulmonary bypass (CPB) is a major complication after cardiac surgery. A vital capacity inflation of the lungs, performed before the end of CPB, may improve gas exchange, but the necessity to repeat it is unclear. Therefore, we studied 18 pigs undergoing hypothermic CPB. A vital capacity manoeuvre (VCM) was performed in two groups and consisted of inflating the lungs for 15 s to 40 cm H2O at the end of CPB. In one group, VCM was repeated every hour. The third group served as controls. Atelectasis was studied by CT scan. Intrapulmonary shunt increased after bypass in the controls and improved spontaneously 3 h later without returning to baseline values. From 3 to 6 h after CPB, there was no more improvement and more than 10% atelectasis remained at 6 h. In contrast, the two groups treated before termination of CPB with VCM showed only minor atelectasis and no abnormal changes in gas exchange directly after bypass or later. We conclude that the protective effect of VCM remained for 6 h after bypass, and there was no extra benefit on gas exchange by repeating the VCM.

Atelectasis is a major cause of hypoxemia and shunt after cardiopulmonary bypass: an experimental study

BACKGROUND

Respiratory failure after cardiopulmonary bypass (CPB) remains a major complication after cardiac surgery. The authors tested the hypothesis that atelectasis is an important factor responsible for the increase in intrapulmonary shunt after CPB.

METHODS

Six pigs received standard CPB (bypass group). Six other pigs had the same surgery but without CPB (sternotomy group). Another six pigs were anesthetized for the same duration but without any surgery (control group). The ventilation-perfusion distribution was measured with the inert gases technique, extravascular lung water was quantified by the double-indicator distribution technique, and atelectasis was analyzed by computed tomography.

RESULTS

Intrapulmonary shunt increased markedly after bypass but was unchanged over time in the control group (17.9 +/- 6.2% vs. 3.5 +/- 1.2%; P < 0.0001). Shunt also increased in the sternotomy group (10 +/- 2.6%; P < 0.01 compared with baseline) but was significantly lower than in the bypass group (P < 0.01). Extravascular lung water was not significantly altered in any group. The pigs in the bypass group showed extensive atelectasis (32.3 +/- 28.7%), which was significantly larger than in the two other groups. The pigs in the sternotomy group showed less atelectasis (4.1 +/- 1.9%) but still more (P < 0.05) than the controls (1.1 +/- 1.6%). There was good correlation between shunt and atelectasis when all data were pooled (R2 = 0.67; P < 0.0001).

CONCLUSIONS

Atelectasis is produced to a much larger extent after CPB than after anesthesia alone or with sternotomy and it explains most of the marked post-CPB increase in shunt and hypoxemia. Surgery per se contributes to a lesser extent to postoperative atelectasis and gas exchange impairment.

Methylene blue localizations of pulmonary nodules under CT-guidance: a new procedure used before thoracoscopic resections

With the expending use of video-assisted thoracoscopy for a wide range of indications, we present our experience of CT-guided localizations of pulmonary nodules with methylene blue injections before their thoracoscopic resections. This technique was developed for deep non-palpable nodules of small size. Forty seven nodules in 44 patients were preoperatively localized under CT guidance and marked with methylene blue injections. The localizations under CT guidance of the 47 nodules were successful in all cases. The surgeon confirmed accurate localization of 46 nodules. In one case, the injected methylene blue could not be identified during thoracoscopy. Complications of this technique included 7 cases of asymptomatic pneumothorax, 5 cases of local and asymptomatic pulmonary hemorrhage, and 2 cases of fits of coughing. Because of this technique, 46 diagnostic thoracotomies could be avoided. CT guided localization with methylene blue injection is a simple and rapid technique enabling good thoracoscopic surgery results.

Radiological findings in nine AIDS patients with Rhodococcus equi pneumonia

Rhodococcus equi (R. equi) infections have been incidentally reported as a cause of pulmonary infection in severely immunocompromised hosts, including AIDS patients. Our purpose is to describe the radiological findings in nine AIDS patients with R. equi pneumonia assessed by bronchoalveolar lavage (BAL), biopsies, cultures of sputum, and hemocultures. All patients were examined by chest radiographs and contrast-medium-enhanced chest CT. Dense pulmonary consolidations with or without cavitations accounted for the most striking radiological patterns. Chest CT also revealed six mediastinal involvements, strongly mimicking a lymphoma. Two of them had multiple bilateral pulmonary nodular opacities. Pleural effusion was not identified. Although intensive therapies were administered, seven among nine patients died within few months. In an AIDS patient living in a rural area or exposed to horses and presenting these radiological patterns, the possibility of R. equi pneumonia should be considered in the differential diagnosis along with other infectious diseases or lymphomas.

Helical CT angiography for traumatic aortic rupture: correlation with aortography and surgery in five cases

Dynamic computed tomography (CT) is frequently performed to assess the mediastinum in trauma patients with a suspected thoracic aortic rupture. Its usefulness lies in demonstrating a mediastinal hematoma. However, many patients still undergo conventional aortography despite a normal chest. CT, because of a perceived insensitivity of this technique for diagnosing aortic rupture. One application of helical CT is CT angiography, in which multiple thin sections are acquired through a blood vessel during the injection of iodinated contrast. Good demonstration of vascular pathology can be achieved, especially with 3-D reconstructions. This article reviews a series of four surgically proven thoracic aortic ruptures studied using helical CT, and one case proven to be false-positive by both helical CT angiography and conventional angiography. Correlation between conventional and helical CT angiography was excellent, with similar findings and the same interpretation pitfalls. Helical CT is fast and noninvasive. Combined examination of other anatomical areas can be performed in the same procedure in major trauma patients. Helical CT may potentially decrease the need for aortography in these acutely injured patients.

Three-dimensional image reconstruction of partial anomalous pulmonary venous return to the superior vena cava

A case of a rare partial anomalous pulmonary venous return of the right upper lobe into the superior vena cava is reported. Multiple three-dimensional image reconstructions in association with spiral CT are used in the aim of clarifying this abnormality of pulmonary venous drainage.

Radiologic findings in two AIDS patients with Rhodococcus equi pneumonia

Rhodococcus equi (R. equi) has been reported as an occasional cause of pulmonary infection in severely immunocompromised hosts, including AIDS patients. Our purpose is to describe the radiologic findings in two AIDS patients with R. equi pneumonia. Chest radiographs showed right-upper-lobe consolidation and cavitation in both patients. Chest CT confirmed upper mediastinal involvement and precarinal lymphadenopathy in both cases. Multiple lung nodules related to the bronchi were also identified in one patient. In an AIDS patient from a rural area or with exposure to horses, the possibility of R. equi infection should be considered when cavitary pneumonia is present, even if there is mediastinal involvement and/or lymphadenopathy, or if multiple lung nodules are also present.

Imaging evaluation of blunt renal trauma in children: diagnostic accuracy of intravenous pyelography and ultrasonography

Forty-six consecutive children with blunt renal injury were evaluated retrospectively to assess the diagnostic accuracy of the different imaging methods, including ultrasonography (US), intravenous pyelography (IVP), and computed tomography (CT), and to determine the optimal radiologic management. Doppler ultrasonography was never performed in an emergency. Classification of the 46 renal injuries was as follows: 25 contusions, 4 lacerations, 11 ruptures, and 6 pedicle injuries. The diagnostic accuracy of IVP (80.8%) was superior to the diagnostic accuracy of US (41%) in all types of renal injuries. IVP should be performed as an emergency procedure when macroscopic hematuria is present, or when an isolated renal injury is clinically suspected. Microscopic hematuria alone is no longer an indication to perform IVP. Asymptomatic patients with microscopic hematuria should have US examination and should be observed with performance of serial urine analyses. Multiply injured and hemodynamically stable children should be evaluated by contrast-enhanced CT. Hemodynamically unstable children should undergo immediate exploratory laparotomy, if it is indicated after assessment by imaging.

CT-guided localizations of pulmonary nodules with methylene blue injections for thoracoscopic resections

As only peripheral subpleural lesions can be visualized at thoracoscopy, deep nonpalpable pulmonary nodules have to be identified before performing wedge resections. We evaluate the efficiency of computed tomographic (CT) guided methylene blue injections to localize these nodules before their thoracoscopic resection. Twenty-three nodules in 21 patients were preoperatively localized under CT guidance and marked with methylene blue injections. The localizations under CT guidance of the 23 nodules were successful in all cases. The surgeon confirmed accurate localization of 22 nodules. In one case, the injected methylene blue could not be identified during thoracoscopy. Complications of this technique included six cases of asymptomatic pneumothorax, four cases of local and asymptomatic pulmonary hemorrhage, and two cases of fit of coughing. Because of this technique, 22 thoracotomies could be avoided and the duration of the hospital stay was then reduced. Computed tomographic-guided localization with methylene blue injection is a simple, effective, and rapid technique enabling good thoracoscopic surgery results.