Download Calcium Amr Sobhy

Calcium
Ca2+
Objectives
Physiological importance of
Calcium
Calcium Homeostasis
Calcium & Anesthesia
Physiological importance of
Calcium
• Calcium salts in bone provide structural integrity of
the skeleton
• Calcium ions in extracellular and cellular fluids is
essential to normal function of a host of biochemical
processes
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Neuoromuscular excitability
Blood coagulation
Hormonal secretion
Enzymatic regulation
Plasma Calcium Regulation
• Plasma calcium totals 9.4 mg/dl.
– Free calcium is 1.2 mmol/L
Plasma Calcium Regulation
Fig. 2
Only this fraction can
affect physiological
functions
Calcium turnover
Plasma Calcium Regulation
• Ca++ ion concentration in body fluid depend on
activities of three organs:
1. Intestine
2. Kidney
3. Bone
• By two mechanism:
1- Buffering functions of exchangeable Ca++in
bone.
2-Hormonal control of Ca++
PTH
 Calcitonin
Vitamin D
Buffering functions of exchangeable
Ca++in bone
First line of defense
Exchangeable reservoir of bone.
Bone remodeling
Hormonal control of Ca++
2nd line of defense
Negative feedback of PTH& Calcitonin
Target organs:
Bone(storage), intestine(absorption)and
Kidney(excretion)
PTH
PTH
Negative
feedback
system
Fig. 5
Actions of
vitamin D
Fig. 13
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Actions of
vitamin D
Fig. 13
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Actions of CT
Fig. 15
Calcium & Anesthesia
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Dysfunctional states
Neuromuscular transmission
Massive blood transfusion
Malignant hyperthermia
cardiopulmonary resuscitation (CPR)
Dysfunctional states
Hypocalemia
 causes
• rapid administration of citrated blood or larage
volumes of albumin
• in alkalosis caused by hyperventilation
• following removal of the thyroid or parathyroid glands.
 manifestation:
– tetany, carpopedal spasm and laryngeal stridor
– decreased cardiac contractility, hypotension, heart failure
or both. prolongation of the QT interval.
– laryngospasm
Dysfunctional states
Hypercalcaemia
 causes
• hyperparathyroidism, malignancy, drug therapy
such as thiazides and lithium, and immobilisation.
 manifestation:
– renal problems, polyuria and polydipsia,
neuropsychiatric disorders, nausea, vomiting and
peptic ulceration.
– raised blood pressure, a shortened Q-T interval and
dysrhythmias
Neuromuscular transmission
• Magnesium sulphate
• Many antibiotics such as aminoglycosides
Massive blood transfusion
• citrate preservative in the stored blood.
• the transfusion rate exceeds one unit every
five minutes
• Patients with hepatic dysfunction or
hypothermia may require calcium infusion
during massive transfusion.
Malignant hyperthermia
• Dantrolene sodium is the drug of choice in the
treatment of malignant hyperthermia and it
acts by inhibiting calcium ion release from the
sarcoplasmic reticulum
Ccardiopulmonary Resuscitation (CPR)
– Severe hypocalcaemia
– Hyperkalaemia
– Myocardial depression resulting from calcium
channel blocking drugs
Any questions
Summary
• The free, ionised calcium concentration is
physiologically important for the functions
of excitable tissues such as nerve and
muscle.
• Calcium homeostasis is regulated by three
hormones, parathyroid hormone, vitamin D
and calcitonin.
• calcium has an important physiological role
in the conduct of anaesthesia.
Thank you