| Abstract: Background and aim
Critical levels of intraabdominal pressure (IAP) concerning v33isceral microcirculation and function are not defined. The breaking points for therapeutic intervention are therefore not fully understood. The aim was to study gastric, intestinal and renal cortex microcirculation parallel with central haemodynamics and respiratory function during stepwise increase of IAP.
Material and methods.The study was performed on 15 anaesthetized pigs, mechanically ventilated via a tracheostomy tube. Airway pressure and lung compliance were continuously registered via the ventilator. Following baseline registrations, CO2 peritoneum was inflated and IAP increased stepwise by 10 mmHg at 10 minute intervals up to 50 mmHg. Arterial pressure, blood temperature, PaO2 and PaCO2 and pH was analysed at each IAP level. Cardiac output (CO) was
measured by thermodilution and mixed venus O2 saturation was measured continouosly using the same monitor.
The microcirculation of gastric mucosa, small bowel mucosa, small bowel seromuscular layer, colon mucosa, colon seromuscular layer and renal cortex were selectively studied using a 4 channel laser Doppler flowmeter (LDF) (Periflex 5000®, PeriMed, fiber diameter 0,125 mm, fiber center separation0,250 mm).
Results. The microcirculation of gastric mucosa, renal cortex and the seromuscular layer of small bowel and colon fell significantly in a linear fashion with each increase of IAP. The microcirculation of the small bowel mucosa was less affected and was reduced in a nonlinear and insignificant pattern. Blood flow of small bowel mucosa remained above 75% of baseline at 40 mmHg of IAP, but was reduced below 40% on the seromuscular side at corresponding IAP.
Cardiac output fell significantly in a linear pattern above 10 mmHg from 4 L/min to 2,5 L/min at the extreme pressure level of 50 mmHg. One animal died at this pressure level. The remaining animals recovered the physiological parameters following evacuation of the CO2 peritoneum.
Conclusion. Renal cortex and gastrointestinal blood flow are significantly and lineary reduced in relation to increased IAP. However small bowel mucosal blood flow seems protected and is not significantly reduced during increased IAP. LDF with adequate probe design allows selective measurement of mucosal blood flow
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