hypocalcaemia

موضوع: hypocalcaemia السبت أغسطس 27, 2011 2:25 pm

In medicine, hypocalcaemia (or hypocalcemia) is the presence of low serum calcium levels in the blood, usually taken as less than 2.1 mmol/L or 9 mg/dl or an ionized calcium level of less than 1.1 mmol/L or 4.5 mg/dL. It is a type of electrolyte disturbance. In the blood, about half of all calcium is bound to proteins such as serum albumin, but it is the unbound, or ionized, calcium that the body regulates. If a person has abnormal levels of blood proteins, then the plasma calcium may be inaccurate. The ionized calcium level is considered more clinically accurate in this case. In the setting of low serum albumin (frequently seen in patients with chronic diseases, hepatic disease or even long term hospitalization), the formula for corrected calcium is: CorrCa = Measured serum Ca + [(4.0 - measured serum albumin) * 0.8]. Thus, if the albumin is low, the measured calcium may appear low when in fact it is physiologically within normal limits.

Cause

It manifests as a symptom of a parathyroid hormone [PTH] deficiency/malfunction, a Vitamin D deficiency, or unusually high magnesium levels hypermagnesaemia, or low magnesium levels hypomagnesaemia.

More specifically, hypocalcaemia may be associated with low PTH levels as seen in hereditary hypoparathyroidism, acquired hypoparathyroidism (surgical removal MCC of hypoparathyroidism), and hypomagnesaemia. Hypocalcaemia may be associated with high PTH levels when the parathyroid hormone is ineffective; in chronic renal failure, the hydroxylation of vitamin D is ineffective, calcium levels in the blood fall, and high PTH levels are produced in response to the low calcium, but fail to return calcium levels to normal.
Eating disorders
Exposure to mercury, including infantile acrodynia
Excessive dietary magnesium, as with supplementation.
Prolonged use of medications/laxatives containing magnesium
Chelation Therapy for metal exposure, particularly EDTA
Absent parathyroid hormone (PTH)
Hereditary hypoparathyroidism
Acquired hypoparathyroidism
Hypomagnesaemia
Following parathyroidectomy, "Hungry Bone Syndrome"
Following thyroidectomy, the parathyroid glands are located very close to the thyroid and are easily injured or even accidentally removed during thyroidectomy
In DiGeorge Syndrome, a disease characterized by the failure of the third and fourth pharyngeal pouches to develop, the parathyroid glands do not form and there is thus a lack of PTH.
Ineffective PTH
Chronic renal failure
Absent active vitamin D
Decreased dietary intake
Decreased sun exposure
Defective Vitamin D metabolism
Anticonvulsant therapy
Vitamin-D dependent rickets, type I
Ineffective active vitamin D
Intestinal malabsorption
Vitamin-D dependent rickets, type II
Pseudohypoparathyroidism
Deficient PTH
Severe acute hyperphosphataemia
Tumour lysis syndrome
Acute renal failure
Rhabdomyolysis (initial stage)
Exposure to hydrofluoric acid
As a complication of pancreatitis
As a result of hyperventilation
Alkalosis, often caused by hyperventilation
Chelation Therapy
Neonatal hypocalcaemia
Very low birth weight (less than 1500 grams)
Gestational age less than 32 weeks

Symptoms
Petechia 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 (medical sign), (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 zygoma will produce facial spasms)
Tendon reflexes are hyperactive
Life threatening complications
Laryngospasm
Cardiac arrhythmias
ECG changes include:
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 fibrillation 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, as with any type of ventricular fibrillation, causes death, unless the patient can be electrically cardioverted, and returned to a normal cardiac rhythm.)

Management
Two ampoules of intravenous calcium gluconate 10% is given slowly in a period of 10 minutes, or if the hypocalcaemia is severe, calcium chloride is given instead. **This is only appropriate if the hypocalcemia is acute and has occurred over a relatively short time frame. But if the hypocalcemia has been severe and chronic, then this regimen can be fatal, because there is a degree of acclimatization that occurs. The neuromuscular excitability, cardiac electrical instability, and associated symptoms are then not cured or relieved by prompt administration of corrective doses of calcium, but rather exacerbated. Such rapid administration of calcium would result in effective over correction - symptoms of hypercalcemia would follow.
However, in either circumstance, maintenance doses of both calcium and vitamin-D (often as 1,25-(OH)2-D3, i.e. calcitriol) are often necessary to prevent further decline.

موضوع: رد: hypocalcaemia السبت أغسطس 27, 2011 2:30 pm

thaaanks gawhara

great subiect

موضوع: رد: hypocalcaemia السبت أغسطس 27, 2011 8:37 pm

u r welcome

thanx alot