Effects of dopexamine and positive end-expiratory pressure on intestinal blood flow and oxygenation: the perfusion pressure perspective.
OBJECTIVE
To evaluate the net effects of the concomitant use of positive end-expiratory pressure (PEEP) and dopexamine on intestinal tissue perfusion and oxygenation during predefined artificial reductions in intestinal perfusion pressure (IPP).


METHODS
Prospective, self-controlled, experimental study.


METHODS
University hospital research laboratory.


METHODS
Seven female pigs.


METHODS
In barbiturate-anesthetized pigs, we measured mesenteric blood flow (QMES) [by transit-time ultrasonic flowmetry], jejunal mucosal perfusion (by laser Doppler flowmetry), and tissue PO(2) (by microoximetry). Based on blood sampling, we calculated the intestinal net lactate production and oxygenation.


METHODS
These measurements and calculations were performed at three predefined and controlled IPP levels, which were obtained by an adjustable clamp around the superior mesenteric artery. At each IPP level, measurements were performed prior to and during PEEP (10 cm H(2)O), both with and without simultaneous dopexamine infusions (at 0.5 and 1.0 microg/kg/min).


RESULTS
Within the IPP range of 77 to 33 mm Hg, intestinal perfusion and oxygenation were maintained irrespective of whether PEEP and/or dopexamine were applied or not. At IPP < 33 mm Hg, QMES and intestinal oxygenation deteriorated, resulting in regional net lactate production. At this IPP range, tissue oxygen perfusion was entirely pressure-dependent, and even small reductions in IPP led to prominent increases in intestinal net lactate production. Dopexamine did not modify this pattern.


CONCLUSIONS
We describe maintained intestinal tissue oxygen perfusion within a wide perfusion pressure range. Within this perfusion pressure range, PEEP did not induce any adverse regional circulatory effects. Below the perfusion pressure range for effective autoregulation, intestinal tissue oxygen perfusion deteriorated, and regional ischemia occurred. In this situation, dopexamine was unable to counteract IPP-dependent decreases in intestinal tissue oxygen perfusion. The regional ischemic threshold can be defined either as an IPP of < 33 mm Hg or as an intestinal tissue PO(2) of < 45 mm Hg.
Lehtipalo
Stefan
S
Anesthesiology and Intensive Care Unit, Department of Surgical and Perioperative Sciences, Umeå University Hospital, Umeå, Sweden. lehtipalo@vll.se
Biber
Björn
B
Fröjse
Rolf
R
Arnerlöv
Conny
C
Johansson
Göran
G
Winsö
Ola
O
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D004298:Dopamine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000098:blood supply* / Q000187:drug effects; D007773:Lactates / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D011175:Positive-Pressure Respiration; D011312:Pressure; D013552:Swine
D000318:Adrenergic beta-Agonists; D007773:Lactates; C046318:dopexamine; D010100:Oxygen; D004298:Dopamine