Monitoring of porcine myocardial ischemia and reperfusion by intravasal microdialysis

Prediction of postoperative complications after urgent laparotomy by intraperitoneal microdialysis: A pilot study

OBJECTIVE

The aim of the present study was to investigate the role of intraperitoneal microdialysis (IPM) techniques in monitoring the evolution of postoperative critically ill patients requiring urgent laparotomy.

SUMMARY BACKGROUND DATA

Postoperative intraabdominal sepsis is associated with an important degree of morbidity and mortality in acutely ill patients. Early diagnosis is critical to improve outcomes.

METHODS

: The study included 25 consecutive patients admitted to the intensive care unit (ICU) after urgent laparotomy. Measurements of microdialysate fluid were performed through a microdialysis catheter, positioned intraperitoneally, during the first 5 postoperative days and lactate/pyruvate (L/P) ratios calculated. Patients were followed until hospital discharge.

RESULTS

Ten patients had a complicated postoperative course, including 4 deaths (3 refractory shock, 1 mesenteric ischemia), 3 reinterventions (1 necrotic collection, 1 mesenteric ischemia, 1 biliary leak), 2 secondary peritonitis, and 1 intraabdominal collection. The IPM L/P ratio in these patients was already significantly higher during the first 24 postoperative hours compared with patients who had no complications (35 +/- 21 vs. 18 +/- 6, P < 0.01). An IPM L/P ratio above 22 on postoperative day 1 had a sensitivity of 0.64 and a specificity of 0.79 for complications. There were no significant differences between the two groups in pH, lactate, white blood cell count, or subcutaneous L/P ratio. No complication was associated with the technique.

CONCLUSIONS

IPM is safe and reliable and provides valuable information after urgent laparotomy. Persistently high L/P values should raise the possibility of serious postoperative complications.

Microdialysis of the bowel: the possibility of monitoring intestinal ischemia

Assessment of the intestinal circulation in a clinical setting still presents a significant diagnostic challenge. In patients suspected of having intestinal ischemia pre- or postoperatively, there is no clinically relevant marker which can determine whether the bowel is suffering from lack of oxygen or not. Microdialysis is a microinvasive technique that makes it possible to continuously detect tissue-specific metabolic changes. Recently, it has been demonstrated that intestinal ischemia can be detected and monitored continuously by the use of a microdialysis catheter placed in the proximity of the ischemic bowel. This review summarizes the clinical dilemma of intestinal ischemia and the latest experimental results using the microdialysis technique to detect critical perfusion in the small intestine. The possibility of using microdialysis in a clinical setting is outlined with the perspective of using it as a pre- or postoperative monitoring tool in relevant patients.

Intraperitoneal and intraluminal microdialysis in the detection of experimental regional intestinal ischaemia

BACKGROUND

The aim was to investigate the possibility of using intraluminal or intraperitoneal microdialysis to monitor regional intestinal ischaemia.

METHODS

Microdialysis catheters were inserted in the lumen, in and outside the intestinal wall, and in the peritoneum of each of ten pigs. Regional occlusive ischaemia was induced in 100 cm of jejunum. Levels of glucose, pyruvate, lactate and glycerol in the microdialysate were measured at 20-min intervals before and after induction of ischaemia. Systemic haemodynamics were monitored and laser Doppler flowmetry (LDF) recordings made in each of the intestinal segments.

RESULTS

Ischaemia caused a significant decrease in glucose level, and an increase in lactate and glycerol concentrations and lactate/pyruvate ratio, at all catheters, although glucose could not be detected by the intraluminal catheter. The metabolic changes occurred simultaneously and were statistically significant in almost all catheters after 100 min. LDF revealed a significant decrease in intestinal blood flow, but there was considerable individual variation.

CONCLUSION

Regional occlusive ischaemia in 100 cm of small intestine could be detected and monitored by means of a microdialysis catheter placed in the peritoneal cavity or the bowel lumen.

Intravasal microdialysis is superior to intramyocardial microdialysis in detecting local ischaemia in experimental porcine myocardial infarction

OBJECTIVE

A novel application of microdialysis was studied, where myocardial outflow of energy metabolites was monitored by intravasal microdialysis in the myocardial venous outflow during ischaemia and reperfusion. These levels where related to levels monitored by microdialysis catheters placed intramyocardially.

METHODS

Microdialysis catheters were introduced into the great cardiac vein (GCV), ischaemic myocardium and non-ischaemic myocardium in 10 anaesthetized pigs. The left anterior descending coronary artery was occluded for 60 min in five pigs and five pigs served as controls. Ischaemia was followed by 120 min of reperfusion. Microdialysis samples were analysed for glucose, lactate, pyruvate and glycerol. Venous lactate and glucose levels were measured by blood samples from the femoral vein.

RESULTS

All animals subjected to ischaemia developed myocardial infarction. Lactate, lactate/pyruvate ratio and glycerol increased in the microdialysis samples from the GCV and the catheter placed in ischaemic myocardium while no changes were detected in samples from the catheter placed in the non-ischaemic myocardium.

CONCLUSION

In this study, we have demonstrated that intravasal microdialysis catheters rapidly and reliably detect local myocardial ischaemia, while intramyocardially placed microdialysis catheters will not show these changes if placed in a non-ischaemic area.

Cardiac outflow of amino acids and purines during myocardial ischemia and reperfusion

A novel application of microdialysis was studied, in which myocardial outflow of amino acids and purines was monitored by intravasal microdialysis in the myocardial venous outflow during ischemia and reperfusion. Microdialysis catheters were introduced into the great cardiac vein, pulmonary artery, and external jugular vein in 20 anesthetized pigs. The left anterior descending artery was occluded in four groups of pigs for 0, 10, 15, and 60 min. Ischemia was followed by 120 min of reperfusion. Microdialysis samples were analyzed for taurine, aspartate, glutamate, hypoxanthine, inosine, and guanosine. Myocardial infarction developed when ischemia exceeded 10 min. Taurine, aspartate, inosine, and guanosine increased early in the great cardiac vein during ischemia. We found the outflow patterns of amino acids and purines to be graded in response to different lengths of ischemia. In this study we have demonstrated a graded outflow of amino acids and purines in response to ischemia and a positive correlation between infarct size and myocardial outflow of amino acids and purines. This could be of value in a clinical setting to quantify the extent of myocardial damage.