Hypernatremia Lecture 5

Definition Serum Na concentration above reference range. (135-145 mmol/L). Water loss decreased intake or excessive loss Sodium gain food, drinks etc.

Water loss Pure water loss Water and sodium loss Decreased intake (elderly, unconscious) Excessive loss (decreased AVP secretion lead to diabetes insipidus, while nephrogenic if the renal tubule don’t respond to AVP) Water and sodium loss Water loss exceeds sodium loss Osmotic diuresis (Diabetes mellitus, excessive sweating or diarrhoea can sometime lead to hypernatremia but in most cases lead to hyponatramia)

Sodium gain (salt poisoning) Sodium bicarbonate (for correction of acidosis) Acidosis is excessive blood acidity caused by an overabundance of acid in the blood or a loss of bicarbonate from the blood (metabolic acidosis), or by a buildup of carbon dioxide in the blood that results from poor lung function or slow breathing (respiratory acidosis). Near drowning in salt water Infants fed on high salt diet (1 tbs of salt raises upto 70 mmol/L of sodium. Primary hyperaldosteronism or Con’s syndrome (excessive aldorsteron secretion lead to Na retention in the renal tubule) Cushing’s disease. (excess cortisol production which has weak mineralocorticoid activity)

Mineralocorticoids are a class of corticosteroids, which are a class of steroid hormones. Mineralocorticoids influence salt and water balances (electrolyte balance and fluid balance). The primary mineralocorticoid is aldosterone. Aldosterone acts on the kidneys to provide active reabsorption of sodium and an associated passive reabsorption of water, as well as the active secretion of potassium in the collecting tubule. Cushing disease is caused by a tumor or excess growth (hyperplasia) of the pituitary gland. 

Clinical Manifestations Confusion Neuromuscular excitability Hyperreflexia (difficulty in reading, understanding etc Seizures (epileptic fits) coma

Other osmolality diordres Increased urea in renal diseases Hyperglycemia Ethanol Osmolal gap Common cause is presence of ethanol Comatosed patients

Hyperkalemia Important IC electrolyte Maintain resting membrane potential of the cells like nerve and muscle cells. Resting membrane potential can be defined as a relatively stable, ground value of transmembrane voltage in animal and plant cells. Or it can also be defined as the relatively static membrane potential of quiescent cells is called the resting membrane potential (or resting voltage). Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. With respect to the exterior of the cell, typical values of membrane potential range from –40 mV to –80 mV. The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.

Heart arrythmias Serum potassium concentration 3.5- 5.5 mmol/L Daily intake is 30 -100 mmol/L loss through GIT 5 mmol Loss through kidneys 20-100 mmol/L

˃ 7 mmol/L is life threatening Cardiac arrest ECG changes Tented of T-waves and Widening of the QRS complex Muscle weakness Paraesthesiae

ECG readings

Causes of hyperkalemia Increased intake Redistribution Decreased excretion

Increased intake Patients with impaired renal functions Drugs as potassium salts Intra venous (not more than 20 mmol/hr) Blood products should be fresh old RBCs releases K+

Redistribution out of cell Metabolic acidosis There lies a reciprocal relationship between K+ and H+ level inside the cell. Due to acidosis, K+ inside the cell are replaced by H+ and thus causing hyperkalemia in serum Potassium release from damaged cells (140 mmol/L is K+ conc. Insdie the cell, so a breakdown of the cell will lead to hyperkalemia e.g. in rhobdomylosis (skeletal muscle breakdown), trauma, tumor lysis etc. Insulin deficiency (insulin stimulates cellular uptake of potassium) So hyperkalemia is an associated feature in insulin deficient patients Hyperkalemic periodic paralysis Rare familial disorder autosomal dominance Recurrent attacks of muscle weakness or paralysis Rest after exercise Pseudohyperkalemis

Decreased excretion Renal failure Hypoaldosteronism Glomerular filtration rate (GFR) is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the glomeruli each minute. Glomeruli are the tiny filters in the kidneys that filter waste from the blood. Renal failure Potassium can not be excreted out when GFR is low Hypoaldosteronism is seen mainly with the use of ACE inhibitors (ACE stands for angiotensin-converting enzyme) for hypertension Potassium sparing diuretics (medicine) also antagonize effect of aldosterone

Pseudohyperkalemia Sampling errors Hemolysis (rbc, wbc and platlets) Check potassium in serum and plasma Chilled samples

Treatment Insulin infused along with glucose to enhance muscular K+ uptake Calcium gluconate/chloride be given to counteract the hyperkalemia Cation exchage resins orally Dialysis in refractory hyperkalemia