[Microcirculatory monitoring of sepsis]

Prognostic value of intraoperative measurements of renal tissue oxygenation and microcirculation on renal function in partial nephrectomy

BACKGROUND

Partial nephrectomy (PNx) can be associated with macrocirculatory and microcirculatory alterations, ultimately leading to acute kidney injury (AKI). Measuring kidney tissue oxygenation (μHbO2) and microcirculation during open PNx might be feasible to early detect these alterations and prevent postoperative AKI.

METHODS

μHbO2 and microcirculation were measured in 45 patients undergoing PNx by reflectance spectrophotometry and laser Doppler flowmetry (O2C™, Lea, Germany), related to ischemia time and tumour size. Pre- and postoperative creatinine levels were determined.

RESULTS

μHbO2 was lower after reperfusion than before clamping (72 vs. 75%), while microcirculation and regional haemoglobin did not differ. Ischemia time was 15.7 min on average. μHbO2 was higher without ischemia (80 vs. 70%, p = 0.109) and in T1a- than T1b-tumours, independent of ischemia time and reperfusion. The renal collecting system (RCS) was opened in 19/45 patients with μHbO2 of 68% after reperfusion compared to 74% with intact RCS. Postoperative complications occurred in 6/45 patients (13%). μHbO2 was 68% before clamping vs. 75% without complications. Serum creatinine of patients with T1b was higher compared to T1a (103 vs. 87 µmol/L). Patients with larger tumours had higher postoperative creatinine levels (173 vs. 124 µmol/L; p = 0.052).

CONCLUSION

We showed for the first time that the method is feasible to monitor renal tissue oxygenation at the level of microcirculation non-invasively and reproducibly during PNx. Tumour size seems to have a decisive influence on oxygenation and postoperative renal function. Our results imply that postoperative complications may be predicted by low intraoperative renal oxygenation and microcirculatory flow measurements.

Impaired microvascular perfusion improves with increased incubator temperature in preterm infants

The optimal thermal environment for sick preterm infants is unknown. Incubator temperature can be regulated to an abdominal wall temperature of 36.5 degrees C [neutral temperature (NT)] or to a minimal temperature difference (<2 degrees C) between abdominal wall and extremities [comfort temperature (CT)]. This could affect the microcirculation, particularly in infants with impaired perfusion. We assessed the microvascular perfusion with near-infrared photoplethysmography (NIRP) at these two target temperatures between d 1 and 4 of life in preterm infants with normal (NL group) or impaired (RED group) microcirculation as determined by a clinical score. Signal strength variables such as area under the curve (AUC) and the first derivate of the amplitude (FLUX) were calculated. Starting temperature was randomized to NT or to CT and then followed by the other temperature. A significant increase of FLUX and AUC in the RED group was found with NT as starting temperature (FLUX: 282 +/- 76 at NT versus 627 +/- 211 at CT; p = 0.025; AUC: 73 +/- 47 at NT versus 234 +/- 112 at CT; p = 0.009), but not with CT. In NL infants, both parameters did not change significantly. Increasing the incubator temperature to CT changes thermoregulatory flow to the extremities in preterm infants with impaired microvascular perfusion and might improve tissue flow.

An evaluation of the effect of a gastric ischemia-reperfusion model with laser Doppler blood perfusion imaging

The objectives of this study are to establish a gastric ischemia-reperfusion model and test it using the laser Doppler blood perfusion imaging (LDPI) method and to evaluate the role of the LDPI technique in the measure of gastric blood circulation. The right gastric artery of the rat was clamped for 30 min and then reperfused. The LDPI was used to display the blood circulation of the whole gastric surface during this process. The blood flow perfusion image of the gastric surface was displayed clearly. After the right gastric artery was clamped, the blood flow perfusion on the gastric surface decreased very significantly until the clamp was loosened. Following reperfusion, the blood flow suddenly increased. Within the first 10 min, the blood-flow perfusion exceeded the level before the clamping and then gradually became smooth and steady. The right gastric artery is a main pathway for gastric blood supply. LDPI can display successfully the blood circulation state of the stomach and the course of ischemia-reperfusion of a large area with an image.