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Arslan et al. Mini-invasive Surg 2018;2:4 I http://dx.doi.org/10.20517/2574-1225.2017.31 Page 3 of 10

preferred, and both techniques have advantages and disadvantages. CO insufflation to abdominal cavity
2
creates pneumoperitoneum. CO insufflation makes considerable pathophysiological affects by causing
2
hypercarbia and acidosis. Apart from that pneumoperitoneum increases intra-abdominal pressure (IAP)
which may cause serious cardiovascular, respiratory and neurological effects [5-7,11-13] . Trendelenburg position
also effects negatively by decreasing pulmonary compliance and functional residual capacity [14-16] .

Effects on cardiovascular system
The effects of pneumoperitoneum on hemodynamics is highly depended on the level of IAP, and patient
[12]
position . With the initiation of pneumoperitoneum mean arterial pressure (MAP) and systemic
vascular resistance (SVR) increase > 25% and 20% respectively, however SVR returns to basal after
[17]
providing Trendelenburg position . Increased IAP decreases the venous return and cardiac output but
[18]
Trendelenburg position reversely increases the venous return and it may neutralize this effect . But
of course these effects alter with the level of IAP. IAP lower than 15 mmHg causes increase in cardiac
output by applying pressure to splanchnic venous bed and sympathetic stimulation caused by hypercarbia
contributes by providing peripheral vasoconstriction and increasing cardiac motility. On the other hand
[18]
IAP > 15 mmHg applies compression over inferior vena cava and preload decreases causing hypotension .
Another significant factor in laparoscopy that has effect on hemodynamics is vagal stimulation. Vagal
stimulation may be initiated by peritoneal expansion caused by pneumoperitoneum, by direct stimulation
[19]
of peritoneum with Veress needle or trocars or as a result of gas embolism (CO embolism) . Vagal
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stimulation may cause bradyarrhythmia (in a range from bradycardia to asystole) and hypotension [7,20] .
[8]
Tachyarrhythmia may also be experienced as a result of sympathetic activation caused by hypercarbia . The
effects of pneumoperitoneum and Trendelenburg position on hemodynamics are usually well tolerated in
patients with normal cardiac function, but it has been reported that even in elderly patients with ASA 2-3
risk or even in patients with underlying heart conditions such as aortic stenosis, laparoscopic operations
may still be safely performed with adequate monitoring and being aware of possible complications [21,22] . High
insufflation pressures and hypercarbia caused by long operative times or CO venous embolism increases the
2
risk of cardiovascular complications.

Effects on respiratory system
During laparoscopy insufflation increases IAP which causes an increase in peak airway pressures and a
[23]
decrease in lung volumes and pulmonary compliance . Particularly in operations such as RALRP or
robotic cystectomy cephalad shift of diaphragm related to high IAP gets more severe by the addition of
[23]
Trendelenburg position, because the abdominal contents push the diaphragm . Eventually atelectasis may
occur and functional residual capacity may decrease and a ventilation-perfusion mismatch may develop.
These changes may lead to hypercarbia and hypoxemia. Moreover, high IAP increases the risk of barotrauma
which may lead to pneumothorax or pneumomediastinum. These effects on respiratory system do not
immediately return to normal postoperatively. Studies show that regaining full function of lungs may take
5 days postoperatively in patients without pulmonary disease, while it may take more than 5 days in patients
[16]
with chronic obstructive pulmonary disease (COPD) . Therefore patients with COPD should be advised to
continue pulmonary rehabilitation even after being discharged.

Effects on neurological system
Pneumoperitoneum and Trendelenburg position are both found to increase the intracranial pressure
(ICP) [5,13,24,25] . During pneumoperitoneum increased IAP prevents the venous return from lumbar venous
plexus thus causing ICP to increase. Cerebral venous drainage is hindered and cerebral intravascular volume
is increased. Due to these reasons ICP increases. Also combining pneumoperitoneum with Trendelenburg
[26]
increases the ICP further and this may hinder cerebral oxygenation . Kalmar et al. [27] examined
patients undergoing RALRP which were exposed to prolonged steep Trendelenburg position and CO
2
pneumoperitoneum and suggested that it does not compromise cerebral perfusion. Though, it is advised to
keep the patient in normocapnic range because regional cerebral oxygen saturation (rSO ) is correlated with
2