Day: April 5, 2024

Overview Rhabdomyolysis refers to a clinical syndrome characterised by skeletal muscle necrosis. Rhabdomyolysis is a condition that develops due to skeletal muscle necrosis and the release of toxic intracellular contents including myoglobin and electrolytes. It is characterised by markedly elevated levels of creatinine kinase (CK). Rhabdomyolysis is a potentially life-threatening condition. The full clinical syndrome is characterised by evidence of myoglobinuria from muscle breakdown and acute tubular necrosis (ATN) causing acute kidney injury (AKI). It is a common condition in the adult population that occurs from a variety of causes including trauma and prolonged immobilisation (e.g. following a fall in the

Overview Refeeding syndrome is an adverse clinical and biochemical response to feeding in severely malnourished patients. Refeeding syndrome (RFS) is generally defined as potentially fatal shifts in fluids and electrolytes that can occur in severely malnourished patients undergoing feeding. Throughout human history, it has been described following famines or in prisoners of war who start eating again after long periods of starvation. The overzealous reintroduction of diet leads to profound electrolyte and fluid derangements that can cause cardiac arrhythmias or cardiac and respiratory failure. Epidemiology It is difficult to estimate the true incidence of RFS due to varied definitions and at times lack of

Introduction Potassium is an essential body cation, which has a normal plasma concentration of 3.5-5.5 mmol/L. Hypokalaemia is one of the most common electrolyte abnormalities within the hospital setting. It is defined as a plasma potassium concentration < 3.5 mmol/L. Hypokalaemia can be a potentially life-threatening condition leading to dangerous cardiac arrhythmias, although most cases are mild and patients are asymptomatic. Hypokalaemia can be further divided as follows: Mild: 3.0-3.4 mmol/L Moderate: 2.5-2.9 mmol/L Severe: < 2.5 mmol/L or symptomatic Epidemiology Hypokalaemia is a common electrolyte abnormality in secondary care affecting up to 20% of inpatients. Potassium concentration is highly variable depending on age, sex,

Overview Hypophosphataemia is defined as a serum phosphate concentration < 0.8 mmol/L. The normal serum concentration of phosphate is 0.8-1.5 mmol/L. Hypophosphataemia is a common electrolyte abnormality that is estimated to affect up to 5% of patients admitted to hospital. In certain populations, hypophosphataemia is common such as those who are malnourished or suffering from refeeding syndrome. In alcoholics, it may be seen in up to 50%. In patients with paracetamol overdose, it is a good prognostic marker that signifies hepatic recovery. Phosphate physiology The human body contains approximately 1000 g of phosphate of which 80-90% is found in bone. Phosphate is

Definition & classification Hyponatraemia is a common medical problem defined as a low plasma sodium (Na+) concentration less than 135 mmol/L. The normal range for serum sodium is 135-145 mmol/L. Hyponatraemia can be classified according to the severity of the biochemical value or the rate of onset. Biochemical severity Mild hyponatraemia: serum Na+ 130-135 mmol/L. Moderate hyponatraemia: serum Na+ 125-129 mmol/L. Severe hyponatraemia: serum Na+ < 125 mmol/L. Rate of onset Acute: duration < 48 hours. Chronic: duration > 48 hours Epidemiology Hyponatraemia is a common electrolyte disturbance encountered in primary and secondary care. The incidence and prevalence of hyponatraemia is variable and dependent on the population studied.

Overview Hypomagnesaemia is defined as a serum magnesium concentration < 0.7 mmol/L. Hypomagnesaemia is a very common electrolyte disturbance that can be seen in up to 65% of intensive care unit patients. Magnesium is commonly lost in the gastrointestinal tract and kidneys. Even small deficits in the net magnesium balance will lead to hypomagnesaemia. This is due to an inability to rapidly exchange between serum magnesium and the bony reserve. The normal range of serum magnesium is 0.7-1.1 mmol/L. Hypomagnesaemia is defined as a serum concentration < 0.7 mmol/L, it is commonly found with other electrolyte derangement including hypokalaemia and hypocalcaemia.

Overview Hypocalcaemia is defined as a serum corrected calcium concentration < 2.2 mmol/L. Hypocalcaemia can lead to dangerous cardiac arrhythmias and requires urgent identification and treatment. The normal serum calcium concentration is 2.2-2.6 mmol/L and this should be corrected for albumin. Hypocalcaemia is a common electrolyte abnormality with a wide range of causes. It is commonly seen in chronic kidney disease (CKD) and vitamin D deficiency. Acute symptomatic hypocalcaemia is most often seen following thyroidectomy (removal of the thyroid gland) which can disrupt the parathyroid glands that are needed for in parathyroid hormone (PTH) secretion. Acute hypocalcaemia can be further divided

Overview Hyperphosphataemia is defined as a serum phosphate concentration > 1.5 mmol/L. Hyperphosphataemia is commonly observed in patients with chronic kidney disease (CKD) because regulation of dietary phosphate is primarily by renal excretion. The normal plasma concentration of phosphate is 0.8-1.5 mmol/L. Hyperphosphataemia is defined by an elevated phosphate level > 1.5 mmol/L. It typically occurs when dietary intake of phosphate exceeds renal excretion but may also occur with massive cell lysis (as phosphate is predominantly an intracellular ion). Phosphate physiology The human body contains approximately 1000 g of phosphate of which 80-90% is found in bone. Phosphate is an essential ion

Overview Hypernatraemia is defined as a serum sodium concentration > 145 mmol/L. Hypernatraemia is commonly encountered in clinical practice. Normal serum sodium concentration is 135-145 mmol/L. Elevations above 145 mmol/L are consistent with hypernatraemia. Hypernatraemia should be considered a problem with total body water (TBW), rather than a problem with sodium homeostasis. There is typically a fall in TBW relative to sodium with failure of normal adaptive mechanisms including thirst and anti-diuretic hormone (ADH). Acute vs chronic When the differentiation between acute and chronic is unknown, patients should always be assumed to have chronic hypernatraemia due to the risk of cerebral

Overview Hypermagnesaemia is defined as a serum magnesium concentration > 1.1 mmol/L. Hypermagnesaemia is an uncommon condition. It is usually only seen in the context of renal impairment and excess administration of magnesium. The normal range of serum magnesium is 0.7-1.1 mmol/L. Hypermagnesaemia is defined as a serum concentration > 1.1 mmol/L, but clinical symptoms usually only develop when the level rises > 2.0 mmol/L. Magnesium physiology Magnesium is principally absorbed from the intestines and excreted by the kidneys. Magnesium is absorbed in the intestines and excreted by the kidney in urine. Bone is the main reservoir of magnesium in the body, but exchange

Overview Hyperlipidaemia broadly refers to having too many lipids (i.e. fats) in the blood. Hyperlipidaemia is a broad term that refers to high levels of one or more of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG). Hyperlipidaemia is very common and a major risk factor in the development of atherosclerosis and cardiovascular disease. Importantly, high levels of high-density lipoprotein cholesterol (HDL-C), commonly referred to as ‘good’ cholesterol, actually confers cardiovascular protection. Various terms for excess serum lipids including hypercholesterolaemia, dyslipidaemia and hyperlipidaemia are often used interchangeably in clinical practice but refer to specific problems with lipid levels and

Overview Potassium is the most abundant intracellular cation, with a normal plasma concentration of 3.5-5.5 mmol/L. Hyperkalaemia may be defined as a blood potassium level ≥ 5.5 mmol/L. It can represent a life-threatening emergency requiring urgent management. Hyperkalaemia can be further divided as follows: Mild: 5.5-5.9 mmol/L Moderate: 6.0-6.4 mmol/L Severe: ≥ 6.5 mmol/L Physiology Potassium is primarily an intracellular cation. Approximately 98% of potassium within the body is found within cells.  An adult has approximately 3,500 mmol of potassium. In the normal individual, a daily intake of 90 mmol/day is recommended by the World Health Organisation.  Cellular uptake of potassium is controlled by sodium-potassium adenosine

Overview Hypercalcaemia is defined as a serum corrected calcium concentration > 2.6 mmol/L. Hypercalcaemia is a common electrolyte abnormality. It occurs when the serum calcium concentration exceeds the amount by which calcium can be deposited in bone or excreted by the kidneys. Normal serum calcium levels range from 2.2-2.6 mmol/L. Corrected calcium levels > 2.6 mmol/L are defined as hypercalcaemia. Depending on the level of serum calcium, hypercalcaemia can be graded: Mild: 2.6-3.0 mmol/L Moderate: 3.0-3.5 mmol/L Severe: > 3.5 mmol/L The most common causes of hypercalcaemia are Malignant hypercalcaemia and Primary hyperparathyroidism. Calcium physiology Calcium is distributed between bone and the intra- and extra-cellular compartments.

Overview Familial hyperlipidaemia refers to the inheritance of a single (or multiple) genetic variant(s) that lead to elevated lipid levels. Familial hyperlipidaemia is also known as primary hyperlipidaemia. It refers to the inheritance of single or multiple genetic variants that cause an abnormal elevation in serum lipids. These lipids include total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG). If there is a single genetic variant (i.e. mutation) this is known as a monogenic disease. If there are multiple genetic variants that all contribute to the development of the condition this is known as a polygenic disease. The pattern of