Hemodynamic changes induced by positive pressure capnothorax during thoracoscopic thymectomy

Low-flow insufflation of CO2 into the thorax helps the surgeon by increasing the surgical field during thoracoscopy, but older studies performed on animals (pigs and dogs) showed that positive pressure capnothorax had negative hemodynamic impact on animals and strongly recommended against using it on humans. We included in our study 24 ASA I-II myasthenic patients (20 females and 4 males) age 29 yo (+/- 10.2) weight 62.8 kg (+/- 10.6) whose thymuses were surgically removed by thoracoscopy. Using thoracic electrical bioimpedance (TEB) we assessed noninvasively cardiac index (CI) stroke index (SI) systemic stroke vascular resistance index (SSVRI) and end diastolic index (EDI). Well known for its hemodynamic stability we chose sevoflurane for induction and maintenance of anesthesia (VIMA). According to Copenhagen scale, adding minimal iv dose of fentanyl (3 mcg/kg) to sevoflurane induction, allowed us to endobronchial intubate in good and excellent conditions. During anesthesia almost all measured parameters (CI, SI, MAP, EDI) recorded statistically significant decrease but with minimal clinical significance. Thus, the maximal drop was measured during application of 10 mm Hg capnothorax: CI and SI dropped by 1.16 1/min/m2 (19%) (p = 0.02) and respectively 16.58 ml/m2 (21%) (p = 0.001). Thereby we are applying low-flow positive pressure insufflation of CO2 into the thorax, to almost all thoracoscopies performed in our clinic.