hypocalcemic tetany
DESCRIPTION
hypocalcemic tetanyTRANSCRIPT
HYPOCALCEMIC TETANY
by G.NAGARJUNA GOUD
CALCIUM O
BJEC
TIVE
S Sources and RDA
Metabolism of calcium
Functions of calcium
Regulation of plasma calcium
Disorders of calcium metabolism
CALCIUM
Calcium is the most abundant mineral in the body
Human body contain about 1-1.5 kg of calcium
SOURCES OF CALCIUM
DAILY REQUIREMENTS OF CALCIUM
Children 1000mg/day
Adults 500mg/day
Pregnancy and lactation1500mg/day
METABOLISM OF CALCIUM
Absorption Factors
affecting absorption
Mechanism of absorption
Excretion of calcium
Distribution and storage
METABOLISM OF CALCIUM - ABSORPTION
Site
Efficiency
Upper small
intestine
20-30% of dietary Ca
FACTORS AFFECTING CALCIUM ABSORPTION
Calcium absorption is increased by
CalcitriolPTHHigh protein dietOptimum Ca:P ratioAcidic pHBile salts
Absorption is decreased by
Alkaline pHPhytates and oxalatesSteatorrheaVitamin D deficiencyExcess phosphate in diet
MECHANISM OF CALCIUM
ABSORPTIONCalcium
absorption occurs by 1,25(OH)2D3
mediated mechanism.
EXCRETION OF CALCIUM
Stools
Unabsorbed calcium in
the diet60 – 70%
Urine
50-200mg/day
Sweat
15mg/day
DISTRIBUTION AND STORAGE OF CALCIUM
Human body contain
about 1-1.5 kg of calcium
99% present in bone and teeth
1% in soft tissue and extracellular fluid
Plasma calcium : 9-11mg/100mlIonized calcium: 4.65-5.25mg/100ml
FUNCTIONS OF CALCIUM
Formation of bone and teeth
Nerve conduction
Muscle contraction
Activation of enzymes
Blood coagulation Secretion of hormones
As a second messenger
Action on myocardium
REGULATION OF ENZYME ACTIVITY
Ca++ activates • Glycogen
phosphorylase kinase
• Amylase • PDH, IDH and α-
KGDH
Ca++ Inhibits • Pyruvate kinase• Trypsin
REGULATION OF PLASMA CALCIUM
50%40%
10%
%
Free or ionized calcium
Protein bound(mainly albumin) 40
complex with anions-citrates,bicarbonates,lactates,phosphates
REGULATION OF PLASMA CALCIUM
3 Organs
Gut
Bone
Kidney
3 Hormones
Calcitriol
PTH
Calcitonin
DISORDERS OF CALCIUM METABOLISM
HypocalcemiaHypercalcemia
HYPOCALCEMIA
Causes Features Treatment
HYPOCALCEMIA CAUSES Inadequate intake
Impaired absorption
Increased excretion
Magnesium deficiency
Acute pancreatitis
Causes of hypocalcemiaCauses of hypocalcemiaI. Factitious hypocalcemia:
Is the reduction of the total , not the ionized fraction of serum calcium with reduction of serum albumin, the patient don't have any symptoms or signs of hypocalcaemia If the serum albumin levels fall to < 4 g/dl., the usual correction is to add 0.8 mg/dl to the measured total serum calcium for every 1.0 gm/dl reduction of serum albumin.
II. Hypoparathyroidism
Hypoparathyroidism is the state of decreased secretion or decreased activity of PTH
Manifestations that occur result from associated hypocalcemia and hyperphosphatemia.
Three categories of hypoparathyroidismThree categories of hypoparathyroidism
Deficient PTH secretion(> 99% of all cases
Deficient PTH secretion(> 99% of all cases
In ability to make an active form of PTH care.
In ability to make an active form of PTH care.
Inability of kidneys and bones to respond to parathyroid hormone being produced by normal parathyroid .
Inability of kidneys and bones to respond to parathyroid hormone being produced by normal parathyroid .
III. Magnesium depletion and hypocalcemia: Normal mg serum level is 1.6-2.1 mEq/L Mg metabolism has a close association with
that of calcium: Are competitive for renal tubular reabsorption Are physiological antagonists in CNS Mg is necessary for PTH release and for its action
Patients with hypocalcemia due to Mg deficiency should be treated with IV mg at a dose of 48 mEq over 24 hours.
IV. Hypocalcemia and hyper phosphatemia: 85% is free and only 15% is protein bound Hypocalcemia and tetany may occur if
serum phosphorus rises rapidly Hyperphosphatemia alters calcium and
phosphate ion solubility products, and calcium deposition in soft tissue may occur.
V. Medications and toxins causing hypocalcemia:
Mithramycin, bisphosphonates, calcitionin, oral or parentral phosphate preparation, anticonvulsants manly (phenytoin or phenobarbital)
Plasmapheresis with citrated blood Radiographic contrast dyes Chemotherapeutic agents. During surgical procedures, hypocalcemia may
occur in the absence of citrated bl. Infusion, may be due to acute hemodilution by physiological saline.
VI.Hungry Bone syndrome
VII.Hypocalcemia and pancreatitis
VIII. Hypocalcemia associated with critical
illness.
IX.Vitamin D disorders resulting in hypocalcemia:
Both inherited and aquired disorders of vit D and its metabolites may be associated with hypocalcemic disorder.
Decreased synthesis of vit D3 in the skin may be due to lack of sun exposure
Fat malabsorption Extensive liver disease Drugs, mainly anticonvulsant. Nephrotic syndrome, may be due to excretion of vit D
binding protein. Ch. R.F. with reduction of GFR to <30% may present
with production of 1-25 dihydroxy vit D.
Hypocalcemia - Features Muscle cramps
and tetany
Laryngospasm
Convulsion
Cardiac arrhythmias
Prolongation of QT interval
Cataract
Chronic hypocalcemia
HYPOCALCEMIA – SIGNS OF TETANY
Contraction of facial muscle in response to tapping the facial nerve, (insensitive test)
Chvostek’s sign
Carpal spasm occurring after occlusion of the brachial artery with BP cuff with pressure 20 mm of Hg above systolic BP for 3-5min.
Trousseau’s sign
Differential diagnosis• Hyperventilation syndrome in hystericals due
to respiratory alkalosis. Rx- simple mask with rebreathing exercises and tranquilisers.
Management1. Dependent on the underlying cause and severity2. Administration of calcium alone is only transiently
effective3. Mild asymptomatic cases: Often adequate to
increase dietary calcium by 1000 mg/day4. Symptomatic: Treat immediately
Investigations• Serum calcium • Ionic calcium• Serum magnesium• Blood urea• Serum creatinine• Serum amylase & serum lipase• Serum proteins;- total proteins,albumin,globulin• Serum electrolytes• PTH hormone immunoassay.• Tests for vitamin D metabolites.• Measurements of the urinary cyclic AMP response to exogenous PTH.• 25(OH)D assays.
HYPOCALCEMIA - TREATMENTSevere symptomatic
cases
Intravenous Calcium gluconate
Asymptomatic cases
Calcium carbonate
Vitamin D
Rx for factitious hypocalcemia• Low serum albumin levels can cause a reduction in
the total, but not the ionized ,fraction of serum calcium.
• Each 1g/dL reduction in the serum albumin concentration will lower the total calcium concentration by approximately 0.8mg/dL without affecting the ionized calcium concentration.
-:Formula:-• Thus ,calcium level should be corrected in patients with low
serum albumin levels ,using the formula :• Corrected calcium(mg/dL)= measured total
Ca(mg/dL)+0.8(4.0-serum albumin <g/dL>),• Where 4 respresents the average albumin
level.
i. Acute hypocalcaemia:
Calcium gluconate is the preferred IV calcium.Calcium gluconate contains 90 mg of elemental calcium/ 10 ml ampoule.Usually 1-2 ampoule (180 mg of elemental calcium) diluted in 50-100 ml of 5% dextrose, is infused over 10 minutes. This can be repeated until the patient's symptoms have cleared. The goals should be to raise serum calcium by 2-3 mg/dl with the administration of 15mg/kg of elemental calcium over 4-6 hours.Calcium should be maintained in the low normal range. If possible oral calcium supplementation should be initiated together with vit D.
ii- Chronic hypocalcemia• Patients who are asymptomatic or with mild
symptomatic hypocalcaemia can be treated with oral calcium and vit D.
• The overall goal of therapy is to maintain serum calcium in the low normal, range, serum calcium should be tested every 3-6 months.
Hypocalcemia with concurrent hypomagnesemia
• Often cannot correct the Ca unless the Mg is corrected• Give 2 gm of Mg (16 meq) of MgSO4 as a 10% solution over
10 to 20 minutes• Followed by 1 gm MgSO4 (8 meq) at 100 mL/hr• Continue intravenous MgSO4 as long as Mg < 1 mg/dL• Careful monitoring if patient has impaired renal function
Calcium saltsDrug preparation: Ca= elemental calcium• Calcium chloride (27.2% cal) 10% solution
(100 mg/ml) given IV but cause local irritation.• Calcium gluconate.• Calcium carbonate: 40% calcium e.g oscal,
titralac.• Calcium citrate 21% cal (citracal).• Calcium lacate 13% calcium.
Vit D preparation: Ergocalciferol: (calciferol) Calcifediol (25-hydoxy vit. ) Calcitriol: (1,25 dihydroxy vit D )
Vitamin D dosage in Rx of chronic hypocalcemia
Simple dietary deficiency - can be corrected by the use of ergocalciferol 400-2000 IU/day
• However in conjunction with other hypocalcemic disorders (e.g., underlying impairments in vitamin D metabolism or renal insufficiency) larger doses may be needed e.g., a 6 to 8 week regimen of 50,000 units, dosed weekly
• Severe malnutrition or malabsorption – may require even higher doses