Vasomotion induces regular major oscillations in jejunal mucosal tissue oxygenation

Abstract

The mucosa of the small intestine has some unique microcirculatory features that may result in significant tissue oxygenation changes even under physiological conditions. To prove this hypothesis we investigated mucosal and serosal oxygenation in an autoperfused, innervated jejunal segment in pigs. Eight animals (30-40 kg) were anesthetized, paralyzed, and normoventilated. A small segment of the jejunal mucosa and serosa was exposed by a midline laparotomy and an antimesenteric incision. Mucosal and serosal oxygen tensions were measured using Clark-type surface oxygen electrodes. Mucosal hemoglobin saturation and concentration were determined by tissue reflectance spectrophotometry. Systemic hemodynamics, mesenteric-venous acid base, and blood gas variables, as well as systemic acid-base and blood gas variables and jejunal electromyogenic potentials, were recorded. Measurements were performed after a rest period at 0, 30, 60, and 90 min. All animals remained hemodynamically stable. At time 0 the jejunal oxygen extraction ratio was 0.33 +/- 0.05, the mean serosal PO2 was 60.25 +/- 7.69, the mean mucosal PO2 was 25.47 +/- 4.41 mmHg, and the mean mucosal hemoglobin saturation was 46.36 +/- 6.22%. Mean values did not change with time. In contrast to serosal PO2, mucosal PO2, mucosal hemoglobin oxygen saturation, and hemoglobin concentration showed rhythmic oscillations with a frequency of 3.4-5 cycles/min that were unrelated to systemic hemodynamic parameters, respiratory frequency, and intestinal peristalsis. From this we concluded that the jejunal mucosa demonstrates significant, regular changes in oxygenation parameters that are locally mediated. We speculate that the physiological basis for this phenomenon is the countercurrent arrangement of microvessels in conjunction with vasomotion.(ABSTRACT TRUNCATED AT 250 WORDS)

Jejunal tissue oxygenation and microvascular flow motion during hemorrhage and resuscitation

“…O 2 consumption of multiwire surface electrodes is small. Measurement errors due to diffusion of atmospheric O 2 to the electrode surface can be avoided with the measurement setup used (13). Therefore, multiwire surface electrodes reflect tissue PO 2 present in mucosal epithelial cells underneath the electrode.…”

“…Therefore, multiwire surface electrodes reflect tissue PO 2 present in mucosal epithelial cells underneath the electrode. On the basis of scanning electronic microscopy investigation results of microvasculature of jejunal villi in pigs and taking into account the surface area of 19 mm 2 of a multiwire surface O 2 electrode, the electrode roughly covers a mucosal area containing 380 villi (13).…”

“…Methodology for the measurement of PO2muc and HBjO2 has been described in detail in previous studies (8,13). Briefly, PO2muc was measured by two Clark-type multiwire surface electrodes (Eschweiler; Kiel, Germany), which were calibrated using pure nitrogen and room air in a 37°C warmed water bath.…”

“…The measuring principle is based on the use of one illuminating and six detecting microlight guides (each 250 m in diameter) and a rapidly rotating bandpass interference filter disk for the generation of monochromatic light in 2-nm steps within the spectral range of 502-628 nm representing 64 different wavelengths. Absolute values of HBjO2 were calculated with the use of an algorithm described in detail by Frank et al (6), which has been validated in a previous study (13). All sensors are introduced into the measurement chamber and onto the mucosal surface via small openings at the top of the chamber, which are sealed with small caps after the sensors have been correctly positioned.…”

Prognostic value of intraoperative renal tissue oxygenation measurement on early renal transplant function

“…Of all patients, 54% required at least one postoperative hemodialysis (median 1, range [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Grafts with delayed function had a longer Cit (mean 11 h 36 min) compared with those not requiring any postoperative hemodialysis (mean 7 h 45 min)(P < 0.05).…”