|
Hypocalcaemia or hypocalcemia is the presence of low serum calcium levels in the blood. Physiologically, blood calcium is tightly regulated within a narrow range for proper cellular processes. Calcium in the blood exists in three primary states: bound to proteins (mainly albumin), bound to anions such as phosphate and citrate, and as free (unbound) ionized calcium. Only the ionized calcium is physiologically active. Normal blood calcium level is between 8.5 to 10.5 mg/dL (2.12 to 2.62 mmol/L) and that of ionized calcium is 4.65 to 5.25 mg/dL (1.16 to 1.31 mmol/L). Common causes of hypocalcemia include hypoparathyroidism, vitamin D deficiency, and chronic kidney disease. Symptoms of hypocalcemia include neuromuscular irritability (including tetany as manifested by Chvostek's sign or Trousseau's sign, bronchospasm), electrocardiographic changes, and seizures. Treatment is dependent upon the cause, but most commonly includes supplementation of calcium and some form of vitamin D or its analogues. ==Signs and symptoms== The neuromuscular symptoms of hypocalcemia are caused by a positive bathmotropic effect due to the decreased interaction of calcium with sodium channels. Since calcium blocks sodium channels and inhibits depolarization of nerve and muscle fibers, diminished calcium lowers the threshold for depolarization. The symptoms can be recalled by the mnemonic "CATS go numb"- Convulsions, Arrhythmias, Tetany and numbness/parasthesias in hands, feet, around mouth and lips. * Petechiae which appear as on-off spots, then later become confluent, and appear as purpura (larger bruised areas, usually in dependent regions of the body). * Oral, perioral and acral paresthesias, tingling or 'pins and needles' sensation in and around the mouth and lips, and in the extremities of the hands and feet. This is often the earliest symptom of hypocalcaemia. * Carpopedal and generalized tetany (unrelieved and strong contractions of the hands, and in the large muscles of the rest of the body) are seen. * Latent tetany * * Trousseau sign of latent tetany (eliciting carpal spasm by inflating the blood pressure cuff and maintaining the cuff pressure above systolic) * * Chvostek's sign (tapping of the inferior portion of the cheekbone will produce facial spasms) * Tendon reflexes are hyperactive * Life-threatening complications * * Laryngospasm * * Cardiac arrhythmias * Effects on cardiac output * * Positive chronotropic effect, or an increase in heart rate * * Negative inotropic effect, or a decrease in contractility * * * ECG changes include the following: * * Intermittent QT prolongation, or intermittent prolongation of the QTc (corrected QT interval) on the EKG (electrocardiogram) is noted. The implications of intermittent QTc prolongation predisposes to life-threatening cardiac electrical instability (and this is therefore a more critical condition than constant QTc prolongation). This type of electrical instability puts the patient at high risk of torsades de pointes, a specific type of ventricular tachycardia which appears on an EKG (or ECG) as something which looks a bit like a sine wave with a regularly increasing and decreasing amplitude. (Torsades de pointes can cause death, unless the patient can be medically or electrically cardioverted and returned to a normal cardiac rhythm.) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「hypocalcaemia」の詳細全文を読む スポンサード リンク
|