Hemodynamic collapse during thoracoscopy

The role of an ambient pressure oxygen source during one-lung ventilation for thoracoscopic surgery

Video-assisted thoracoscopic surgery is facilitated by prompt collapse of the non-ventilated (‘operated’) lung, and interrupted and impeded if there is a need for oxygen (O2) delivery by continuous positive airways pressure in order to manage hypoxaemia. It has been proposed that connecting an ambient pressure O2 source to the airway of the non-ventilated lung at the time one-lung ventilation is initiated and before the chest is opened will, by avoiding entrainment of ambient nitrogen, serve to facilitate lung collapse. It has also been proposed that leaving the O2 source connected will enable, not only ongoing apnoeic oxygenation before the chest is opened, but also the thoracoscopic procedure to commence with the operated lung fully pre-oxygenated (with an inspired oxygen fraction of 1), and apnoeic oxygenation to continue throughout the operative procedure in those patients who exhibit a degree of small airways patency at ambient pressure. In reality, several factors can influence the speed of collapse of the operated lung, and very many factors can influence the incidence of hypoxaemia during one-lung ventilation. It therefore appears unlikely that the necessary evidence to support these proposals will be forthcoming from randomised clinical studies on large numbers of patients. Rather, the necessary evidence may only be provided by specifically designed within-patient clinical measurement studies. Nevertheless, it is argued that, in the meantime, there is already sufficient rationale for an ambient pressure O2 source to be connected to the airway of the non-ventilated lung, and for it to remain connected for the duration of one-lung ventilation.

Right or left first during bilateral thoracoscopy?

BACKGROUND

Endoscopic thoracic sympathectomy (ETS) is now an established surgical technique for treatment of palmar hyperhidrosis that is performed under general anesthesia with positive pressure ventilation via either an endotracheal tube or a double lumen endobronchial tube. This is a bilateral disease that requires the division of the right and left thoracic sympathetic chain. The aim of this study was to compare the hemodynamic changes using a left capnothorax first versus right a capnothorax first surgical approach using a single lumen endotracheal tube in patients undergoing bilateral ETS. Lung collapse was achieved by carbon dioxide insufflation.

METHODS

Forty patients of both sexes aged 18-30 years and of American Society of Anesthesiologists grade I were randomly assigned to undergo bilateral ETS. Patients were divided into two groups. Group L comprised left capnothorax first, followed by right capnothorax (n = 20). Group R comprised right capnothorax first, followed by left capnothorax (n = 20). The anesthesia technique was standardized for all patients. Cardiovascular variables were determined during the procedure every minute. Statistical analysis was performed by independent-sample t test and Pearson's chi-square test.

RESULTS

There was a significant (P < 0.05) mean percentage decrease in systolic blood pressure in group L compared to group R. Similarly, the mean percentage decrease in diastolic blood pressure in group L was significant compared to group R (P < 0.05). Seven patients in group L developed bradycardia, but this was not found to be statistically significant.

CONCLUSIONS

When the left capnothorax first approach was used, there was significant hypotension, compared to a right capnothorax first thoracoscopy. We thus recommend that right capnothorax should be performed first in cases of bilateral ETS.

Cardiovascular changes during drainage of pericardial effusion by thoracoscopy

BACKGROUND

Cardiovascular changes during drainage of pericardial effusion are not well understood, and most studies are of systemic effects and not of right ventricular performance. Thoracoscopy is not widely used to drain pericardial effusions because of haemodynamic changes in relation to the use of single lung ventilation.

PATIENTS AND METHODS

We studied 16 patients undergoing partial pericardiectomy for pericardial effusion, using videothoracoscopy with a low-pressure pneumothorax (6 mm Hg). Cardiac output was measured by thermodilution with the patient anaesthetized in the supine position before the procedure; in the right lateral position after a low-pressure pneumothorax had been established; and after drainage of the pericardial effusion.

RESULTS

Before the procedure, cardiac output was low and central venous pressure and pulmonary artery occlusion pressure were increased. Systemic vascular resistance and arterial blood pressure were within normal limits. Cardiac filling pressure and pulmonary arterial pressure increased during the pneumothorax. After the drainage cardiac index increased and systemic and pulmonary vascular resistances were reduced.

CONCLUSIONS

Pericardial effusion reduces right ventricular distensibility, right and left systolic ventricular function, and cardiac output. Anaesthesia with mechanical ventilation and a low-pressure pneumothorax do not affect the circulation greatly. Drainage of the pericardial effusion allows cardiac distensibility to increase and cardiac performance changes to allow increased ejection.

Cardiovascular collapse caused by carbon dioxide insufflation during one-lung anaesthesia for thoracoscopic dorsal sympathectomy

Carbon dioxide insufflation into the pleural space during one-lung anaesthesia for thoracoscopic surgery is used in some centres to improve surgical access, even though this practice has been associated with well-described cardiovascular compromise. The present report is of a 35-year-old woman undergoing thoracoscopic left dorsal sympathectomy for hyperhidrosis. During one-lung anaesthesia the insufflation of carbon dioxide into the non-ventilated hemithorax for approximately 60 seconds, using a pressure-limited gas inflow, was accompanied by profound bradycardia and hypotension that resolved promptly with the release of the gas. Possible mechanisms for the cardiovascular collapse are discussed, and the role of carbon dioxide insufflation as a means of expediting lung collapse for procedures performed using single-lung ventilation is questioned.

Physiologic changes during thoracoscopy

Despite the obvious benefits of minimally invasive surgery, the physiologic changes associated with thoracoscopic procedures present multiple challenges. The lung is the site of gaseous exchange, but during thoracoscopic surgery it is simultaneously either the surgical target organ or responsible for obscuring surgical exposure. Thus, there is a conflict of interests between the need to provide ideal surgical conditions and the need to maintain normal pulmonary and cardiovascular physiology. In an attempt to minimize the physiologic insult associated with thoracoscopic surgery, multiple anesthetic and surgical techniques have therefore been developed. None are entirely problem free, however. Because the physiologic changes are technique specific, a clear understanding of the dynamic interaction between the anesthetic-surgical technique and patient physiology is essential.

Hemodynamic effects of carbon dioxide insufflation under single-lung ventilation during thoracoscopy

BACKGROUND

The hemodynamic effects of carbon dioxide insufflation under single-lung ventilation were studied in 22 consecutive thoracoscopic harvests of the left internal mammary artery, which was used for minimally invasive coronary artery bypass grafting.

METHODS

An electrocardiograph, arterial catheter, Swan-Ganz catheter, and transesophageal echocardiograph were used to monitor seven hemodynamic variables. Baseline data were obtained during ventilation of both lungs and the measurements were repeated after the left lung was collapsed and at 5 and 30 minutes after hemithorax insufflation with low-flow (2 to 3 L/minute) carbon dioxide gas was begun. The intrapleural pressure was maintained at 8 to 10 mm Hg.

RESULTS

Thoracoscopic harvest of the internal mammary artery was completed in all cases with a mean insufflation time of 44+/-12 minutes. There were no significant changes in the mean arterial pressure, heart rate, cardiac index, and left ventricular ejection fraction throughout the procedure, whereas the central venous pressure, mean pulmonary arterial pressure, and pulmonary capillary wedge pressure (p < 0.05 for each variable) during insufflation.

CONCLUSIONS

Low-flow carbon dioxide insufflation into the left hemithorax with an intrapleural pressure of 8 to 10 mm Hg under selective right-lung ventilation does not compromise the human heart with normal to moderately depressed function and can be an efficacious adjunct in specific thoracoscopic procedures.

Selective lung ventilation during thoracoscopy: effects of insufflation on hemodynamics

BACKGROUND

Positive-pressure insufflation during thoracoscopy has been advocated by some authors to facilitate exposure of the intrathoracic structures by expediting collapse of the lung. We hypothesized that insufflation during thoracoscopy may result in hemodynamic compromise despite selective lung ventilation.

METHODS

After placement of invasive monitoring lines, six adult swine underwent selective lung ventilation and thoracoscopy. Baseline measurements of hemodynamic indices were taken before selective lung ventilation. The right lung then was collapsed; data were obtained at insufflation pressures up to 10 mm Hg and were compared with baseline values using Student's t test.

RESULTS

Cardiac index, mean arterial pressure, and left ventricular stroke work index decreased, whereas pulmonary artery and central venous pressures increased (p < 0.05) at insufflation pressures of 5 mm Hg and greater.

CONCLUSIONS

Positive-pressure insufflation during thoracoscopy resulted in significant hemodynamic compromise despite the use of selective lung ventilation. Conversion to thoracotomy may be an alternative if positive-pressure insufflation is necessary to perform the thoracoscopic procedure.