Discussion
The main finding of our study was, there was a false increase in PVI and a false decrease in SpHb with abdominal insufflation. Although this situation developed in all patients, it was found statistically significant only in the obese patient group (Group 2). Also, in obese, SpHb was affected by desufflation as well as insufflation.
As a result of advanced medical practices all over the world, the elderly population is increasing all over the world. However, elderly patients need more surgery day by day and the importance of hemodynamic monitoring is increasing at this point. Invasive procedures such as pulmonary artery catheters, central venous catheters, transesophageal echocardiogram require special training, increase complications and cost, and take time to apply (12,13). Assessment of laboratory parameters such as hemoglobin (Hb), lactate and base deficit (BE) is often used in the process of intraoperative evaluation, but operation cost also increases because of these measurements, and the evaluation of these parameters is not very effective as it takes time. Therefore, the use of non-invasive hemodynamic monitoring is increasingly important.
Blood loss estimation and evaluation of the intravascular volume during surgery is still a major problem. Changes in intravascular volume or airway pressures can cause changes in cardiac pumping ability (14). However, as with cardiogenic shock, not all reductions in cardiac output are associated with intravascular volume. There are also a number of recent studies regarding the poor consequences of intraoperative excess fluid overload in patients. It has been reported that the application of each liter of extra fluid added to the intraoperative fluids increases the risk of postoperative symptoms and complications by 16% and 32%, respectively (15). It has been stated that patient admissions are shortened, surgical site infections are reduced and perfusion improves with sufficient but not much fluid administration (16,17). Therefore, the relevance of fluid administration has been studied for many years and it has been reported that dynamic measurements based on cardiopulmonary interactions in mechanically ventilated patients are the best predictors of fluid response (18). Stroke volume variation (SVV), pulse pressure variation (PPV), and PVI are among the most frequently used dynamic parameters in the management of perioperative fluid therapy.
PVI allows clinicians to determine fluid sensitivity in critically ill patients. SpHb allows continuous analysis of hemoglobin concentration and helps in making decisions about blood transfusions. It is especially important for operations where blood loss is high and time loss cannot be tolerated (19). The reliability of these parameters has been confirmed in intensive care patients and open abdominal cases in the operating room (5,20,21). However, the effect of pneumoperitonium on these parameters in obese is not clear.
In fact, studies evaluating the effects of pneumoperitonium on non-invasive hemodynamic monitoring parameters have attracted attention in recent years. Hoiseth et al. (22) showed that PVI increased during pneumoperitonium in their studies in which they investigated the dynamic variables of fluid responsiveness in patients undergoing laparoscopic surgery. Liu et al. (3) showed that PVI increased with pneumoperitonium and that PVI value decreased to pre-pneumoperitonium values ​​after desufflation. However, the number of studies investigating the effects of obesity is very limited. However, determination of intravascular volume is critical in obese patients. Because pneumoperitonium created for adequate visualization of the operative area in laparoscopic surgeries results in a high pressure increase in the abdomen. As with non-obese patients, intraabdominal pressure is adjusted up to 12-15 mm Hg during laparoscopy in obese patients. Normal intra-abdominal pressure of non-obese individuals is 5 mm Hg or less (23). In contrast, obese patients may have a chronically elevated intraabdominal pressure up to 9 to 10 mm Hg. (24). Increased intraabdominal pressure increases venous stasis, reduces portal venous blood flow, increases airway pressure and impairs heart function (25). To minimize these effects, it is necessary to optimize the intravascular volume to make appropriate ventilation adjustments, to use appropriate compression devices to minimize venous stasis, and to minimize the effects of increased intra-abdominal pressure on kidney and heart function. At this point, the importance of hemodynamic monitoring is obvious for intravascular volume optimization.
In this study, in which we examined the effects of pneumoperitoneum on non-invasive hemodynamic monitoring parameters, PVI and SpHb, we observed that PVI increased and SpHb decreased by abdominal insufflation in all patients. However, these changes were only significant in the obese patient group. DeBarros et al. (14) compared open surgery, laparoscopic obesity surgery and laparoscopic surgery in non-obese patients. In this study, they identified an incorrect increase in PVI with insufflation. This finding coincides with our study. In the same study, they observed a change on SpHb with insufflation, but this change was not statistically significant. The difference between our study and this study may be due to inclusion of different types of laparoscopic surgeries into their studies. Since we investigated the effects of obesity and pneumoperitonium in our study, we preferred laparoscopic cholecystectomy surgeries with minimal fluid losses and bleeding that may affect PVI and SpHb measurements, and a short operation duration of laparoscopic cholecystectomy surgeries. We tried to provide standardization by including the single type of surgery in our study. We also tried to minimize the effects of comorbid diseases by including only ASA 1-2 patients in our study. De barros et al. included different types of laparoscopic surgeries without ASA limitation in their studies. As a matter of fact, the average ASA level was stated as 3 in their studies. These situations may be the reason for the differences between the two studies.
This study has some limitations. First of all, our study is an observational study with limited sample size. Second, we included only ASA 1-2 patients in our study. Because we wanted to evaluate only the effects of obesity and pneumoperitoneum in our study, we wanted to rule out PVI and SpHb changes that may occur due to different comorbid diseases. More different studies are needed with ASA3-4 patients. Finally, we preferred laparoscopic cholecystectomy operations to standardize patient groups. The amount of intraoperative bleeding was minimal and the need for blood transfusion did not occur in any patient. Further studies are needed to evaluate the effect of obesity and pneumoperitonium on noninvasive monitoring in large laparoscopic operations such as large oncological resections, thoracic and colorectal surgeries, that blood loss is predicted and require blood transfusion.
As a result, pneumoperitonium in obese can lead to errors in PVI and SpHb monitoring. Although these two parameters are very valuable in intraoperative follow-up, they should be used carefully during laparoscopic procedures in obese patients. If these parameters (PVI and SpHb) are considered to be used in bariatric surgeries, which are the most common surgical procedure with the combination of obesity and pneumoperitonium, this information should be considered. According to our knowledge, this study is the first study with standardized patient groups on the reliability of PVI and SpHb of obesity and pneumoperitoneum. In order to evaluate the usefulness of non-invasive hemodynamic monitoring in laparoscopic procedures in obese, further research is needed in larger laparoscopic procedures.