Discussion
hypoxia, Left-sided regional cerebral oxygen, Kupisiak
HYPOXIA, SECONDARY
The purpose of the study to evaluate the impact of MF inhaled anesthesia coupled with PP on cerebral oxygenation and hemodynamic parameters. The major findings of the present study can be summarized as follows: 1) Anesthetic gas consumption was significantly lower in the MF anesthesia group; 2) PP decreased pulse rate irrespective of the flow type of anesthesia. However, pulse rates were mostly comparable between MF and NF anesthesia groups; 3) Although significantly lower before anesthesia induction in the MF group, pulse rate decreased in both MF and NF groups after PP and usually remained significantly higher in the MF group compared to the NF group throughout the rest of the procedures; 4) Left-sided regional cerebral oxygen saturations were consistently and significantly higher in the MF group compared to the NF group. PP decreased RCO on the right side, but not on the left side, in both anesthesia groups; 5) There was no discernable effect of anesthesia flow or PP on peripheral oxygen saturation in any of the groups; 6) Anesthesia depth (assessed by MAC) was comparable between the MF and NF groups at all measurement points during anesthesia induction and surgery.Surgical procedures dealing with the spine usually require PP of the patients. This unfamiliar position might lead to some alteration in the respiratory and hemodynamic functioning of the body. First, when the thorax and abdomen are positioned in the prone position, intraabdominal and intrathoracic pressures increase with a resultant reduction in venous return to the heart. Arterial blood pressure and cardiac output decrease. Increased intrathoracic pressure also leads to a secondary increase in intracranial pressure through increased central venous pressureSeveral studies sought to find answers to whether these hemodynamic changes can lead to clişnically important hemodynamic and oxygenation alterations in the cerebral circulation. Bombardieri et al. performed a study in which they investigated the impact of PP on cerebral perfusion in patients undergoing posterior lumbar surgery. The authors evaluated cerebral blood flow velocity with transcranial Doppler ultrasonography. They found an insignificant increase in mean arterial blood pressure after PP. Cerebral perfusion was not affected significantly by PP , eitherDespite several enticing advantages mentioned in the introduction section, MF anesthesia has several concerns, as well. Two of them are inadequate anesthesia depth and hypoxia. Some studies evaluated LF anesthesia in these regards in various surgical settings. Kupisiak et al.Some limitations of the current study are worthy of mention. First, the bispectral index was not included to evaluate anesthesia depth. Instead, minimum alveolar concentration has been used. Second, some studies follow patients after general anesthesia and evaluate mental state before and after the operation to unravel the effects of alterations of cerebral oxygenation on cognitive functions. Cognitive functions were not evaluated in the study. However, no cerebral oxygen desaturation was observed in the MF group compared to the NF group. Lastly, the right and left regional cerebral oxygen saturation values at baseline were significantly different between the LF and NF groups, significantly higher in the lef hand side. Thus, this might have led to the discrepant results we attained.