Electrolyte Disturbances

**Chapter 9**

**Abstract**

patients.

**137**

**1. Introduction**

Electrolytes in the ICU

*Syed Zaidi, Rahul Bollam and Kainat Saleem*

**Keywords:** Electrolytes, Sodium, Potassium, critically ill, ICU

important ICU scenarios which could affect electrolytes.

**2. Disorders of sodium homeostasis**

Electrolyte disorders is an imbalance of certain ionized salts (sodium, potassium, calcium, bicarbonate, chloride) in the blood. Healthcare providers should be familiar with the principles of electrolyte physiology and pathophysiology. Disturbances in sodium homeostasis are primarily caused by volume abnormalities leading to primarily neurologic symptoms. Dyskalemias frequently present with cardiac manifestations therefore should be treated promptly before evaluating its cause. Ion deficiencies such as hypocalcemia, hypomagnesemia and hypophosphatemia should be corrected as they are associated with increased adverse events in critically ill

Electrolytes are elements that naturally occur in the human body and help balance pH, facilitate passage of fluid through osmosis and regulate the function of neuromuscular, endocrine and excretory systems. Disturbances in these electrolytes are common clinical problems encountered in the intensive care unit with serious complications when they are depleted. Recent studies report that electrolyte imbalances are associated with increased morbidity and mortality. Possible mechanisms include damage to the kidney, activation of hormonal systems (such as RAAS) or the myriad of medication given in a critically ill patient. This chapter will focus on various electrolyte abnormalities seen in the critical care setting then touch on

• Serum sodium reflects the plasma tonicity and is inversely related to total body water. Changes in sodium are generally due to changes in total body water, not serum sodium, which regulates plasma tonicity and effective arterial volume. The body normally prevents plasma sodium to stray outside normal range (135

to 145 mEq/L or mmol/L) by controlling water intake and excretion.

• Sodium crosses systemic capillary membranes through clefts between endothelial cells therefore sodium concentration is identical in plasma and interstitial fluid [1]. Brain capillaries have tight endothelial junctions lined by astrocytic foot processes creating the blood–brain barrier which sodium cannot cross [2]. Consequently, an abnormal plasma sodium causes water movement across the blood brain barrier leading to either brain swelling or shrinkage.
