Cerebral metabolic alterations in rats with diabetic ketoacidosis: effects of treatment with insulin and intravenous fluids and effects of bumetanide

Abstract

Objective: Cerebral edema is a life-threatening complication of diabetic ketoacidosis (DKA) in children. Recent data suggest that cerebral hypoperfusion and activation of cerebral ion transporters may be involved, but data describing cerebral metabolic alterations during DKA are lacking.

Research design and methods: We evaluated 50 juvenile rats with DKA and 21 normal control rats using proton and phosphorus magnetic resonance spectroscopy (MRS). MRS measured cerebral intracellular pH and ratios of metabolites including ATP/inorganic phosphate (Pi), phosphocreatine (PCr)/Pi, N-acetyl aspartate (NAA)/creatine (Cr), and lactate/Cr before and during DKA treatment. We determined the effects of treatment with insulin and intravenous saline with or without bumetanide, an inhibitor of Na-K-2Cl cotransport, using ANCOVA with a 2 x 2 factorial study design.

Results: Cerebral intracellular pH was decreased during DKA compared with control (mean +/- SE difference -0.13 +/- 0.03; P < 0.001), and lactate/Cr was elevated (0.09 +/- 0.02; P < 0.001). DKA rats had lower ATP/Pi and NAA/Cr (-0.32 +/- 0.10, P = 0.003, and -0.14 +/- 0.04, P < 0.001, respectively) compared with controls, but PCr/Pi was not significantly decreased. During 2-h treatment with insulin/saline, ATP/Pi, PCr/Pi, and NAA/Cr declined significantly despite an increase in intracellular pH. Bumetanide treatment increased ATP/Pi and PCr/Pi and ameliorated the declines in these values with insulin/saline treatment.

Conclusions: These data demonstrate that cerebral metabolism is significantly compromised during DKA and that further deterioration occurs during early DKA treatment--consistent with possible effects of cerebral hypoperfusion and reperfusion injury. Treatment with bumetanide may help diminish the adverse effects of initial treatment with insulin/saline.

FIG. 1.

Cerebral metabolites measured by ¹H- and ³¹P-MRS in DKA and control rats. A: ATP-to-Pi ratios. B: PCr-to-Pi ratios. C: NAA-to-Cr ratios. D: Intracellular pH. E: Lactate-to-Cr ratios. All values are means (95% CI). A and B are geometric means; C, D, and E are arithmetic means. n = 20 for control and 41 for DKA rats in C and D; n = 20 for control and 44 for DKA rats in A, B, and E. *Values are significantly different from those of the control group; P values <0.005.

FIG. 2.

¹H-MR spectra obtained before DKA treatment and at the end of 2-h treatment with insulin and saline. Lact, lactate.

FIG. 3.

³¹P-MR spectra obtained before DKA treatment and at the end of 2-h treatment with insulin and saline. α−, αATP; γ−, γATP.

FIG. 4.

A: ATP-to-Pi ratios in DKA rats before and after saline and insulin infusion with and without bumetanide. ATP-to-Pi ratios were measured by ³¹P-MRS as described in research design and methods. Bumetanide alone and saline plus insulin with and without bumetanide treatments were started immediately after baseline measurements (0 h). All values are geometric means (95% CI); n = 12, 10, 10, and 12 for no treatment, bumetanide alone, saline and insulin, and saline and insulin with bumetanide treatment groups, respectively. *Within-group comparisons: P < 0.02 for comparison of pre-/posttreatment values in the bumetanide-alone group and the insulin-and-fluid group. Refer to Table 2 for the overall effects of insulin plus saline and bumetanide. Data were analyzed with log-transformed values. B: PCr-to-Pi ratios in DKA rats before and after saline and insulin infusion with and without bumetanide. PCr-to-Pi ratios were measured by ³¹P-MRS as described in research design and methods. Bumetanide alone and saline and insulin with and without bumetanide treatments were started immediately after baseline measurements (0 h). All values are geometric means (95% CI); n = 12, 10, 10, and 12 for no treatment, bumetanide alone, saline and insulin, and saline and insulin with bumetanide treatment groups, respectively. *Within-group comparisons: P = 0.01 for comparison of pre- and posttreatment values in the insulin-and-fluid group. P = 0.051 for comparison of pre- and posttreatment values in the bumetanide-alone group. Refer to Table 2 for the overall effects of insulin plus saline and bumetanide. Data were analyzed with log-transformed values. C: NAA-to-Cr ratios in DKA rats before and after saline and insulin infusion with and without bumetanide. NAA-to-Cr ratios were measured by ¹H-MRS as described in research design and methods. Bumetanide alone and saline and insulin with and without bumetanide treatments started immediately after baseline measurements (0 h). All values are arithmetic means (95% CI); n = 13, 9, 9, and 10 for no treatment, bumetanide alone, saline and insulin, and saline and insulin with bumetanide treatment groups, respectively. *Within-group comparisons: P = 0.03 for comparison of pre- and posttreatment values in the insulin-and-fluid group. Refer to Table 2 for the overall effects of insulin plus saline and bumetanide. D: Intracellular pH in DKA rats before and after saline and insulin infusion with and without bumetanide. Intracellular pH values were determined by ³¹P-MRS as described in research design and methods. Bumetanide alone and saline and insulin with and without bumetanide treatments were started immediately after baseline measurements (0 h). All values are arithmetic means (95% CI); n = 12, 10, 10, and 12 for no treatment, bumetanide alone, saline and insulin, and saline and insulin with bumetanide treatment groups, respectively. *Within-group comparisons: P < 0.05 for comparison of pre- and posttreatment values in the insulin-and-fluid group and the insulin-and-fluid plus bumetanide group. Refer to Table 2 for the overall effects of insulin plus saline and bumetanide.