Electrolyte and pH dependence of heart rate during hemodialysis: a computer model analysis.
The influence of hemodialysis-induced modifications in extracellular fluid characteristics on heart rate was investigated by using a detailed computer model of sinus-node electrical activity. Changes similar to those occurring in the course of hemodialysis in extracellular concentrations of sodium (from 138 to 140 mM), potassium (from 6 to 3.3 mM), and calcium (from 1.2 to 1.5 mM) ions as well as in pH (from 7.31 to 7.4) and intracellular volume were simulated. The model predicted that such changes may largely influence the rhythm of the sinoatrial node pacemaker, causing the heart rate to range from 69 to 86 bpm. Heart rate increases after removing potassium (up to 7 bpm) and also after calcium perfusion (up to 11 bpm) whereas restoring pH slows heart beat (up to 6 bpm). Extracellular sodium has no significant influence, but the heart rate strictly depends on intracellular sodium concentration (5 bpm/mM). A complex dependence of heart rate on electrolytes and pH was also recognized. Providing extracellular potassium concentration is maintained above 5 mM, heart rate exhibits low sensitivity to changes in calcium and potassium. When potassium concentration is reduced below 4.5 mM, heart rate sensitivity to calcium and potassium increases significantly to 10 and 30 bpm/mM, respectively. A sustained increase in heart rate always corresponds to an increase in intracellular sodium concentration.
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Biomedical Engineering Laboratory, DEIS, University of Bologna, Italy.
Cavalcanti
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D000109:Acetylcholine / Q000378:metabolism; D000200:Action Potentials / Q000502:physiology; D000465:Algorithms; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D003198:Computer Simulation; D005110:Extracellular Space / Q000378:metabolism; D005544:Forecasting; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008954:Models, Biological; D017711:Nonlinear Dynamics; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D006435:Renal Dialysis; D012680:Sensitivity and Specificity; D012849:Sinoatrial Node / Q000378:metabolism / Q000502:physiology; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D015220:Calcium Channels; D015221:Potassium Channels; D015222:Sodium Channels; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium