| Research Abstract |
Pharmacological openers of mitochondrial ATP-sensitive potassium (mitoKATP) channels have been shown to mimic ischemic preconditioning (IPC) in both the brain and myocardium. Power spectrum of heart rate variability (HRV) decreased after abdominal aortic surgery (AAS). We hypothesized that nicorandil, a mitoKATP opener, and adenosine could improve HRV and hemodynamics and reduce renal dysfunction after aortic cross-clamping in patients undergoing aortic surgery.
With informed consent and institutional approval, patients undergoing elective AAS were studied. Nicorandil was given continiously during surgery. RR intervals were measured for 24 hourx on the preoperative day (C) and on 1 (POD1), 3 (POD3), and 7 (POD7) postoperative day. An instantaneous heart rate (IHR) time series was constructed from RR intervals. Phase-space attractors were created by using a time delay technique to produce a n-dimensional vector from a one-dimensional time series..A point in n-dimensional phase space , n=
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2 to 20, was formed by n successive time-delayed values of the IHR. Correlation dimensions and embedding dimensions of attractors were determined by means of the method of Grassberger and Procaccia. Spectral analysis of an instantaneous heart rate time series was performed on 512-s segments of RR intervals. The areas of the spectral peaks within-each measurement were calculated as follows : low (LF, 0.04-0.15 Hz), and high-frequency area (HF, 0.15-0.5 Hz), and total power (TP, 0.04-0.5Hz).
LF, HF, and TP were decreased until 7th postoperative day as compared to C. The embedding dimension decreased on the first and the third postoperative days after AAS, returning to Control level on the 7th postoperative day. The correlation dimension decreased on the first postoperative day after AAS, returning to Control level on the 3rd postoperative day, The renal function did not changed as compared with those before surgery.
Simultaneous analysis of nonlinear and linear measures of HRV revealed different patterns of alterations in status of dynamic cardiovascular homeostasis and autonomic nervous system after AAS. Using dimensional analysis, we have shown that significant reduction occurred both the embedding and correlation of dimensions in HRV only during immediate postoperative period in patients without nicorandil. Patients recieved with nicorandil improved HRV, hemodynamics after aortic cross clamping as compared patients without nicorandil after aortic cross clamping. Less
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