Figure 319

Electrocardiographic changes associated with hypokalemia. A, The U wave may be a normal finding and is not specific for hypokalemia. B, When the amplitude of the U wave exceeds that of the T wave, hypokalemia may be present. The QT interval may appear to be prolonged; however, this is often due to mistaking the QU interval for the QT interval, as the latter does not change in duration with hypokalemia. C, Sagging of the ST segment, flattening of the T wave, and a prominent U wave are seen with progressive hypokalemia. D, The QRS complex may widen slightly, and the PR interval is often prolonged with severe hypokalemia. Hypokalemia promotes the appearance of supraventricular and ventricular ectopic rhythms, especially in patients taking digitalis [16].

FIGURE 3-20

Renal lesions associated with hypokalemia. The predominant pathologic finding accompanying potassium depletion in humans is vacuolization of the epithelium of the proximal convoluted tubules. The vacoules are large and coarse, and staining for lipids is usually negative. The tubular vacuolation is reversible with sustained correction of the hypokalemia; however, in patients with long-standing hypokalemia, lymphocytic infiltration, interstitial scarring, and tubule atrophy have been described. Increased renal ammonia production may promote complement activation via the alternate pathway and can contribute to the interstitial nephritis [17,18].

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