0071643192.pdf

Electrolyte Disturbances

HYPERKALEMIA

Hyperkalemia alters membrane polarization. The degree of ECG changes

depends somewhat on the rapidity of onset (slowly developing hyper-

kalemia →ECG findings at higher K+concentrations).

ECG FINDINGS(SEEFIGURE2.7)

■ K+=6.5–7.5 ng/dL: Tall peaked T waves (earliest), PR prolongation

■ K+=7.5–8.0 ng/dL: P wave flattens, QRS widens

■ K+>9.0 ng/dL: Sine wave pattern of QRS

HYPOKALEMIA

Hypokalemia alters membrane polarization.

ECG FINDINGS(SEEFIGURE2.8)

■ Flattening of the T wave (earliest sign)

■ Prominent U waves following T waves

■ ST depression at low levels

HYPERCALCEMIA

ECG FINDINGS(SEEFIGURE2.9)

■ Shortened QT intervals (classic finding)

■ Depressed and shortened ST segments

■ Widened T waves

CARDIOVASCULAR EMERGENCIES

I

II

III

PHYTIM 9TRIP: II

25 mm/sec: 1 cm/mV

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6

FIGURE 2.6. Left ventricular hypertrophy.

Tall, peaked T waves are the

earliest ECG finding in

hyperkalemia.