Thoracic electrical impedance and fluid balance during aortic surgery

Area of Science:

• Cardiovascular Surgery
• Critical Care Medicine
• Physiological Monitoring

Background:

• Aortic surgery requires careful fluid management.
• Traditional hemodynamic monitoring may not accurately reflect fluid balance.
• Pulmonary function can be compromised by fluid overload.

Purpose of the Study:

• To evaluate fluid balance indices during and after aortic surgery.
• To assess the correlation between thoracic electrical impedance (TI) and fluid balance.
• To investigate the impact of fluid balance on hemodynamic and blood gas variables.

Main Methods:

• 16 patients undergoing aortic surgery were monitored.
• Measurements included thoracic electrical impedance (TI), heart rate (HR), central venous pressure (CVP), pulmonary artery mean pressure (PAMP), pulmonary wedge pressure (PWP), mean arterial pressure (MAP), and blood gas variables.
• Fluid balance was calculated, accounting for evaporation.

Main Results:

• A positive fluid balance was observed during and after surgery.
• Thoracic electrical impedance (TI) showed a significant negative correlation with fluid balance (rho = -0.41; P < 0.01).
• Despite stable HR, MAP, and PWP, CVP and PAMP decreased, suggesting a potential volume deficit, which contrasted with the actual positive fluid balance indicated by TI.

Conclusions:

• Thoracic electrical impedance (TI) is a valuable tool for monitoring fluid balance in aortic surgery patients.
• Central venous and pulmonary artery pressures may not accurately reflect fluid status in this population.
• Even minor positive fluid balance can adversely affect pulmonary function and blood gas parameters post-aortic surgery.