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.