[Endoscopic thyroidectomy with filling the neck of rabbits with carbon dioxide and saline]

The study was aimed to investigate the effects of different levels of pressure and duration of carbon dioxide and saline in the neck of rabbits on metabolic, hemodynamic, serum sodium concentrations and hematocrit changes.

Twenty-one New Zealand rabbits were randomly divided into 7 groups according to the following pressure of CO2 or saline: 0 kPa, 0.67 kPa CO2, 1.33 kPa CO2, 2.00 kPa CO2, 0.67 kPa saline, 1.33 kPa saline, and 2.00 kPa saline. In order to make a space for the endoscopic thyroidectomy, we filled the neck of rabbits with carbon dioxide and saline. Arterial partial pressure of CO2 (PaCO2), pH, heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), serum sodium concentration and hematocrit were measured at baseline, 45 min and 90 min after filling with gas or saline and 30 min post-filling.

Insufflation of CO2 at 0.67 kPa did not have any significant effect on the parameters, PaCO2 increased significantly 45 min and 90 min after insufflation of 1.33 kPa CO2 (P < 0.01). Marked changes in PaCO2, pH and CVP occurred 45 min and 90 min after insufflation of 2.00 kPa CO2 (P < 0.01), and the parameters did not return to baseline in 30 min after desufflation (P < 0.05). In animals receiving saline irrigation no significant changes occurred in PaCO2, pH and serum sodium concentrations at any time point. There was a tendency of decrease in HCT, but no statistically significant changes were found (P > 0.05). CVP increased significantly 90 min after saline irrigation at 1.33 kPa (P < 0.05). A significant increase in CVP occurred 45 min and 90 min after saline irrigation at 2.00 kPa (P < 0.05). No significant changes in HR and MAP occurred in all animals.

Filling with saline which does not cause hypercapnia, acidosis or dilutional hyponatremia can be used in endoscopic neck surgery to create and maintain a working space.