Abstract
Multiple nerve excitability measurements have been proposed for clinical testing of nerve function, and an important determinant of excitability is membrane potential. We report a patient with acquired hypokalemic paralysis in whom multiple excitability indices (stimulus -response curve, strength-duration properties, threshold electrotonus, recovery cycle) were measured during and after an acute hypokalemic attack (serum K+ level, 2.1 mEq/L and 4.5 mEq/L, respectively). During hypokalemia, there was a shift of the stimulus-response curve to the right, a decrease in strength-duration time constant, a "fanning-out" of responses during threshold electrotonus, a reduction in relative refractory period, and an increase in superexcitability; all of these indicate axonal hyperpolarization, presumably due to the K+ equilibrium potential being more negative. These indices returned to normal 20 h later, associated with normalization of the serum K+ level. These results demonstrate that the changes associated with hypokalemic paralysis are not confined to muscle and that axons undergo hyperpolarization in vivo. Multiple excitability measurements can be used as a tool to identify changes in membrane potential of human axons.
Original language | English |
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Pages (from-to) | 283-287 |
Number of pages | 5 |
Journal | Muscle and Nerve |
Volume | 26 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2002 |
Externally published | Yes |
Keywords
- Hypokalemia
- Membrane potential
- Multiple excitability measurements
- Refractory period
- Superexcitability
- Threshold of electrotonus
ASJC Scopus subject areas
- Clinical Neurology
- Physiology (medical)
- Cellular and Molecular Neuroscience
- Physiology