BACKGROUND: Cerebrovascular reactivity (CVR) reflects cerebrovascular reserve capacity, and cerebrovascular reactivity damage prognosticates a very high risk of stroke.OBJECTIVE: To evaluate CVR by detecting the increase rate of blood flow volume of middle cerebral artery (MCA) before and after breathholding in diabetic patients with hypertension, and observe the effects of hypertension on cerebrovascular reserve capacity of diabetic patients. DESIGN: Controlled observation.SETTINGS: Department of Function, Affiliated Hospital of Hebei University; Department of Special Diagnosis, the 202 Hospital of Chinese PLA.PARTICIPANTS: Inpatients or outpatients with type 2 diabetes mellitus (DM) or primary hypertension admitted to Departments of Gastroenterology and Cardiology, Affiliated Hospital of Hebei University and the 202 Hospital of Chinese PLA from April to December 2004 were involved in this experiment. Inclusive criteria: type 2 DM met the criteria of the report on diabetes diagnosis announced in 1999 by WHO expert committee, totally 88 patients were involved. Primary hypertension met the diagnosis criteria announced in 1999 by WHO/1SH, totally 42 patients were involved. Another group of 43 concurrent subjects who received physical examination served as controls. According to the disease condition, the involved patients were assigned into 3 groups: DM group (only diabetic patients), hypertension group (only hypertension patients) and DM complicated with hypertension group (diabetic patients with hypertension). Informed consent for the examination was obtained from all the involved subjects.METHODS: Before MCA of subjects was detected, bilateral carotid artery was routinely detected by high-frequency ultrasonography. Subjects were rejected when stenosis rate of unilateral internal carotid artery or common carotid artery≥70%. Vessels were expanded with transcranial color Duplex Doppler by breath holding test for detecting vascular reactivity. Hypercapnia was created by BHT. The mean velocity and diameter of blood flow were detected under the quiescent condition and 25 s after breath holding with transcranial color-coded duplex sonography. The volume of blood flow of MCA was calculated according to the following formula: Volume of blood flow of MCA (mL/ min) = (the diameter of blood flow /2)2×π×mean blood flow velocity×60. The increase rates of mean blood flow velocity and blood flow volume of patients with hypercapnia were calculated as compared with under the quiescent condition to evaluate cerebrovascular reactivity.MAIN OUTCOME MEASURES: Mean blood flow velocity, blood flow diameter and MCA blood flow volume as well as the increase rates of them.RESULTS: Among the 173 participates, 103 patients and 39 healthy controls were involved in the final analysis, and the other 31 dropped out due to not accomplishing the examination. Flow parameter of MCA under the quiescent condition: The mean blood flow velocity of DM complicated by hypertension group was significantly higher than that of DM group (P ＜ 0.05) and control group (P ＜ 0.05); The blood fjow diameter of DM complicated by hypertension group was significantly smaller than that of control group (P ＜ 0.01). Under the quiescent condition, significant difference was not found in the intergroup comparison of blood flow volume of MCA.②Comparison of increase rate of blood flow parameter: In the DM group, hypertension group, DM complicated by hypertension group and control group, the increase rate of mean blood flow velocity of was (29.34±4.50) %, (29.35±4.35) %, (26.68±4.99) % and (30.99±3.54) %, respectively, the increase rate of blood flow volume of MCA was (35.32±5.08) %, (35.36±6.16) %, (31.78±7.11) % and (37.26±4.17) %, respectively, and the increase rate of blood flow diameterwas (2.29±1.09) %, (2.27±0.95) %, (1.97±1.05) % and (2.36±0.46) %, respectively. The increase rate of mean blood flow velocity and that of blood flow volume of MCA in the DM complicated by hypertension group were significantly lower than those in the other 3 groups (P ＜ 0.05).CONCLUSION: CVR is markedly lowered and cerebrovascular reserve capacity is damaged in diabetic patients with hypertension.