the regional circulatory changes that occur during laparoscopy?
Laparoscopy causes an increase in intracranial
pressure (ICP). Firstly, the absorption of CO2 and the resultant
hypercarbia cause an increase in cerebral blood flow and consequently ICP.
Secondly, the pneumoperitoneum increases ICP, with or without an increase in
PaCO2. The increase in IAP determines the extent of increase in ICP.
High IAP compresses the inferior vena cava causing an increase in lumbar spinal
pressure, which decreases drainage of cerebrospinal fluid from the lumbar
plexus. In turn, there is decreased cerebrospinal fluid drainage and increased
ICP. This increase is unresponsive to hyper-ventilation, yet ICP is higher when
ventilation is inadequate. High IAP also causes a cephalad shift of the
diaphragm, increasing intrathoracic pressure, also increasing ICP.
There is controversy in the literature
regarding the effects of increased IAP on splanchnic perfusion. Some believe
that the CO2 pneumoperitoneum causes vasodilat-ing effects that
counteract the effects of increased IAP on perfusion. Others believe that there
is a decrease in splanchnic flow that results both from mechanical com-pression
of the mesenteric vasculature and from humoral factors, i.e., antidiuretic
hormone causing superior mesen-teric artery constriction.
There is a decrease in renal blood flow when
IAP >15 mmHg. There is a decline in glomerular filtration rate (GFR), urine
output, creatinine clearance, sodium excretion, and the potential for volume
overload in the face of excessive fluid administration. Patients with
pre-existing renal dys-function should have optimization of their hemodynamics
during pneumoperitoneum and the use of nephrotoxic drugs should be avoided.
The development of pneumoperitoneum causes a
decrease in femoral venous flow increasing the risk of deep vein thrombosis.
This is especially problematic if the patient is placed in the reverse
Trendelenburg position because of blood pooling in the lower extremities.
Intermittent sequential compression stockings should be used.