Mark Wefers Bettink

Chapter 8 158 4). Fluid balance was 900 ml positive. Apart from 400ml withdrawal for autologous transfusion, 200ml blood was lost during surgery. Under this controlled hypovolemic circumstance, mitoPO 2 dropped from 83 mmHg to values around 20 mmHg. Lactate levels rose from 9.0 mg/dL to 19.8 mg/dL. After the tumor was removed and volume status was restored to a normovolemic state, mitoPO 2 showed recovery. Discussion The results of this study show that it is feasible to measure mitoPO 2 with the COMET ® during surgery in a real-world situation. It is important to note that covering the measurement surface and protecting it against ambient light is essential for getting a good signal quality. In hemodynamically stable patients a mean mitoPO 2 between 60-40 mmHg was found and baseline mitoPO 2 was 60 ± 17 mmHg. Previously published results in healthy volunteers showed mean mitoPO 2 (± SD) values of 44 ± 17 mmHg. Higher values were expected in this study, as a higher inspiratory oxygen fraction was used during surgery. Since mitochondrial oxygen tension reflects the oxygen balance between oxygen supply and oxygen demand 13,14 , a decreased metabolism during general anaesthesia may also cause increased mitochondrial oxygen levels 15 . Not only during general anesthesia, but also with various lifestyle-related diseases like neurodegenerative disease 16 , cardio- vascular disease 17 and obesity 18,19 a reduced oxygen metabolism and mitochondrial dysfunction are described. Septic patients are another example in whom a reduced oxygen metabolism and mitochondrial failure have been described 20 . Recently a study in patients with severe sepsis showed a relatively high mitoPO 2 (61 ± 10 mmHg) 21 . Despite the intention tomeasuremitoPO 2 in the operation theatre under stable conditions this was not achieved for all parameters in all patients. In some patients, skin temperature increased after the warm air blanket was applied. We hypothesize that this played a role in the small, probably not clinically relevant, drop in mitoPO 2 (figure 2). Theoretically, this drop can be explained by an increase in cellular metabolism due to a higher temperature resulting in a higher oxygen demand and lower mitoPO 2 values. As a result of this higher rate in energy consumption cells rapidly break ATP down to adenosine diphosphate (ADP) an inorganic phosphate group (Pi). In this process adenosine monophosphate (AMP) and [H + ] are released which are both strong vasodilators and blood flow and tissue oxygen saturation increases 22,23 . Our data is supporting this theory, as a rise in temperature gives a drop in intracellular PO 2 (mitoPO 2 ) while cutaneous microvascular blood flow and