[Changes and relations between heart function and organ blood flow in rats at early stage of severe burn]

To investigate the instant changes in heart function and organ blood flow, and their relations in rats at early stage of severe burn.

Thirty-six SD rats were divided into sham injury group (S, n = 6) and burn group (B, n = 30) according to the random number table. Rats in B group were subjected to 30% TBSA full-thickness burn. Five time points for observation: 10 and 30 minutes, and 1, 3, and 6 hour (s) post injury (PIM/H) were set up, with 6 rats at each time point. Rats in S group were sham scalded with 37 degrees C warm water. Hemodynamics indexes including heart rate (HR), mean artery pressure (MAP), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), LV + or - dp/dt max were determined. Blood flow of heart, brain, kidney, spleen, stomach, and ileum was determined respectively with fluorescent microspheres method. The correlation between LV + or - dp/dt max and myocardial blood flow was analyzed.

(1) Compared with those of S group, HR in B group decreased gradually after injury; MAP, LVSP, LV +dp/dt max, LV -dp/dt max and myocardial blood flow in B group decreased obviously at PIM 10 (with F value respectively 12.062, 12.629, 11.066, 18.374, 9.468, and P values all below 0.01). Among them, myocardial blood flow decreased from (6.8 + or - 0.8) mL x min(-1) g(-1) to (2.6 + or - 0.5) mL x min(-1) x g(-1). Above-mentioned indexes increased gradually as the time after injury went on, with the highest values (except for LV +dp/dt max) observed at PIH 1, which decreased again later, with values at PIH 3 and 6 significantly lower than those in S group (the same F values as above, P values all below 0.01). There was no obvious difference in LVEDP between S group and B group at each time point (F = 1.205, with P values all above 0.05). (2) Compared with those of S group, blood flow of kidney, spleen, stomach, and ileum of rats in B group at PIM 10 declined obviously (with F value respectively 22.694, 20.856, 12.653, 7.293, P < 0.05 or P < 0.01), but the decline range was smaller than that in heart. The lowest values of above-mentioned indexes were observed at PIH 1 or PIH 3. Brain blood flow of rats in B group at each time point was close to that in S group (F = 1.812, with P values all above 0.05). (3) The correlation coefficient r between LV +dp/dt max, LV -dp/dt max and myocardial blood flow was respectively 0.651 and 0.617, showing significant positive correlation (with t value respectively 4.456 and 4.222, and P values all below 0.01).

The myocardial ischemia and decrease in cardiac function may occur in a very short time after severe burn (PIM 10). The rapid decrease of heart blood flow plays an important role in the change in cardiac function. Myocardial damage and decrease of cardiac function may be one of the important factors result in the decline of blood flow in other organs.