*2.2.3 Diagnostic approach*

• Net water loss accounts for a majority of cases of hypernatremia [19]. Since sustained hypernatremia can occur only when thirst or access to water is impaired, the groups at highest risk are patients with altered mental status, intubated patients and elderly individuals [20].

Adult Female: 50%; 45% in elderly.

*DOI: http://dx.doi.org/10.5772/intechopen.96957*

accordingly.

*Electrolytes in the ICU*

**3. Potassium homeostasis**

nervous system.

**3.1 Hyperkalemia**

*3.1.1 Introduction*

**143**

hyperkalemia [28].

cardiac arrest or respiratory failure.

*Urine Free Water clearance ml* ð Þ¼ *=hr Urine flow rate*

• Through hospitalization, patients will have ongoing water losses which includes insensible losses (stool, sweat, respirations) and urine free water that should be accounted for. Insensible losses cannot be measured therefore can be approximated

• For acute or chronic hypernatremia, serum sodium should be measured every 4-6 hours and the estimated fluid replacement rate should be adjusted

• Patients is an important electrolyte that has been proven essential for normal functioning of the cardiovascular system, skeletal muscle, internal organs and

• The intracellular proportion of K+ represents 98% of the total body K+. The intracellular potassium concentration is approximately 140 mEq/L (mmol/L) compared to the normal serum potassium of 3.5-5.5 mEq/L (mmol/L). This ratio of potassium concentrations in the cells and extracellular fluid is a major determinant of the resting membrane potential across cell membranes [27].

• An abnormal potassium level predisposes patients to serious complications such as cardiac arrythmias, muscle weakness which could provoke sudden

• Hyperkalemia is defined as serum potassium ≥5.5 mEq/L (mmol/L) which is commonly seen in patients with chronic kidney disease, diabetes or

cardiovascular disease. High potassium intake is rarely sufficient to result in

• Based on the European Resuscitation Council Guidelines classification of

1.Mild Hyperkalemia: - Serum Potassium 5.5-5.9 mEq/L (mmol/L)

3. Severe Hyperkalemia: - Serum Potassium ≥6.5 mEq/L (mmol/L)

• Hyperkalemia is associated with increased mortality in patients with chronic kidney disease and ESRD on dialysis. See **Figure 4** for causes of hyperkalemia.

2.Moderate Hyperkalemia: - Serum Potassium 6.0-6.4 mEq/L (mmol/L)

hyperkalemia based on serum potassium levels [28]:

� *Urine flow rate* � ð*Urine sodium* <sup>þ</sup> *Urine Potassium*<sup>Þ</sup> *Serum Sodium*

(3)

as 30-50 ml/hr [25, 26]. Urine free water can be calculated (see Eq. 3):

• Hypertonic sodium gain usually results from clinical interventions or accidental sodium loading. See **Figure 3** for diagnostic approach.
