Parathyroid gland Flashcards
Patients have ______ parathyroid glands
4
Parathyroid glands produce
parathyroid (PTH) also called parathormone)
-released into the bloodstream by negative feedback mechanism
dependent on plasma calcium concentration
The half life of parathyroid hormone levels is________ and the average PTH level is:
4 minutes
average PTH level*****: 8-51 pg/mL
Hypocalcemia causes
release of parathormone
Hypercalcemia causes
suppression of synthesis and release of parathormone
Parathyroid hormone maintains
normal plasma calcium concentration*****
Calcium moves across these three interfaces:
GI tract, renal tubules, and bone
Calcitonin
opposes the effects of PTH
Calcitonin is secreted by
the parafollicular cells in the thyroid****
Calcitonin secretion is stimulated by
increased serum calcium (hypercalcemia)
Calcitonin lowers
blood calcium ***** in 3 ways:
inhibits osteoclast activity in bones (promotes bone storage of calcium)
inhibits renal tubular cell reabsorption of Ca2+
inhibits Ca2+ absorption in the intestines
The osteoclasts are found on the surface of bones and work by
breaking down bone tissue by digestion and degradation
Resorption is the
absorption into the circulation– osteoclasts break down the bone tissue and release minerals, resulting in the transfer of calcium from bone tissue to the blood
Vitamin D is ______ soluble
fat
Vitamin D increases
intestinal absorption of calcium, magnesium, and phosphate
Vitamin D maintains
calcium homeostasis and metabolism
Vitamin D receptors are found in
intestines, kidneys, bone, and parathyroid gland
- helps transport proteins absorb calcium in the intestine
- bone resorption
- Reabsorption of calcium in the distal nephron
Vitamin D can be found from
the diet- Vitamin D2 (cholecalciferol) and Vitamin D3 (ergocalciferol)
The synthesis of D2 is dependent on
sun exposure
Both Vitamin D2 & D3 get hydrolyzed in
the liver to 25-hydroxyvitamin
then in the kidney it gets hydrolyzed again to 1,25-hydroxyvitamin D*****
The normal total (bound and free) serum calcium concentration is
9.5-10.5 mg/dL
Normal ionized calcium is
****4.75-5.7 mg/dL
Describe how acidosis and alkalosis affect calcium levels.*****
acidosis increases serum calcium
alkalosis decreases serum calcium
Approximately _____ of serum calcium is bound to albumin, ______ is ionized, and _____ is bound to chelating agents (phosphate, citrate, and sulfate)
50%; 40%; 10%
Ionized calcium fraction depends on
pH
Protein binding
decreases as pH decreases
Alkalosis (& calcium)
increases calcium binding to protein; decreases ionized fraction
Acidosis (& calcium)
decreases calcium binding to protein; & increased ionized fraction
Each 0.1 decrease in pH increases
ionized calcium by 0.05 mmol/L
Biological functions of calcium include
bone formation, reservoir for ECF, blood clotting, excitability of nerve and muscle, metabolic regulation for action of hormones & enzyme activation
Reduced production of PTH can be the result of
DiGeorge syndrome
CATCH 22 syndrome
autoimmune
Disorders related to PTH include:
impaired PTH due to peripheral resistance
parathyroid gland adenomas**
reduced production of PTH
Hyperparathyroidism is the
excess production of PTH***
The most common cause of hyperparathyroidism is
hypercalcemia, defined as total serum calcium above 10.4 mg/dL
Hyperparathyroidism can be classified as ****
primary (parathyroid gland destruction), secondary (appropriate response to hypocalcemia as seen in CKD), or ectopic
Primary hyperparathyroidism can be due to
excessive secretion of parathormone due to:
benign adenoma (80-90%)****
hyperplasia (15%)
carcinoma (<1-5%)
With primary hyperparathyroidism, over
50% of patients are asymptomatic
Symptoms are more common at
calcium levels above 11.5-12 mg/dL
Manifestations of hypercalcemia involve primarily the
kidneys and skeletal system- calcium deposits in renal parenchyma or recurrent nephrolithiasis and skeletal pathology
Diagnosis of hyperparathyroidism
PTH assay calcium levels vitamin D levels renal function CT scans has anything happened to the neck? albumin?
Medical management of hyperparathyroidism includes
used for mild, asymptomatic disease
mild hypercalcemia–>hydration
moderate to severe hypercalcemia (13-15)- IV saline hydration and furosemide to promote a Na/Ca diuresis
Surgical management of hyperparathyroidism includes
definitive treatment
intraoperative PTH assay is measured before and at a 5-minute intervals after adenoma removal to confirm a rapid fall to normal
With multiple-gland hyperplasia, all glands must be identified and either
- three are removed, with partial excision of the fourth (leaving a good blood supply)
- total parathyroidectomy is performed, with immediate transplantation of a removed, minced parathyroid gland into the forearm muscles
Hypoparathyroidism is the
absence or deficiency in PTH secretion
resistance of peripheral tissues to the effects of the hormone
Hypoparathyroidism results in
hypocalcemia
Hypoparathyroidism tends to be
iatrogenic (removed surgically with thyroidectomy)
Clinical signs of hypocalcemia include
neuronal irritability skeletal muscle spasms tetany seizures fatigue and mental status changes prolonged QT interval Congestive heart failure (chronic) hypotension (acute)
Acute hypocalcemia can present with
stridor, laryngospasm, and apnea
Tetany occurs because
normally calcium blocks sodium channels and inhibits depolarization of nerve and muscle fibers, reduced calcium lowers the threshold for depolarization
Treatment for hypocalcemia includes
electrolyte replacement
calcium and vitamin D
hypomagnesemia is managed with oral or IV replacement
Severe symptomatic hypocalcemia requires
10-20 mL of 10% calcium gluconate or 3-5 mL of 10% calcium chloride followed by a continuous infusion of calcium (1-2 mg/kg/hr)
For anesthesia and hypocalcemia,
treat hypocalcemia prior to surgery
Major anesthetic risks of hypocalcemia include
decreased cardiac contractility and dysrhythmias
tetany
altered response to muscle relaxants
risk for laryngospasm
The treatment for overactive parathyroid gland is
surgical removal of the benign tumor
Without treatment for overactive parathyroid gland,
problems of fatigue, bad memory, kidney stones, and osteoporosis will result
Parathyroid surgery is performed
supine, arms tucked, gel head ring, 2 PIVs, antiemetic coverage, GA with NIMS monitoring ETT, inhalation agent, remifentanil infusion, no abx, ether screen and 2 clicks down on bed for neck extension
The anesthetic management of parathyroidectomy includes:
concern for cardiac dysrhythmias secondary to elevated calcium–> hypercalcemia decreases the refractory period and increases ventricular excitability
NIMs ETT–> assess RLN
Careful positioning–> risk for fractures
Postoperative complications of parathyroidectomy
are similar to thyroid surgery- recurrent laryngeal nerve injury, hematoma, hypocalcemia
-acute hypocalcemia- only if severe deficit preop or injury to all parathyroid glands
The effects of neuromuscular blocking agents with parathyroidectomy are
unpredictable secondary to hypercalcemia- consider qualitative NMB monitoring
Parathyroid surgery uses
large IV for PTH sampling
if it is impossible to site a peripheral IV that will drawback then an arterial line may be needed
consider saphenous IV
position NIBP cuff (above PTH sample IV) to function as a tourniquet
PTH sampling during surgery involves
- baseline PTH sample
- scheduled PTH samples in OR are at:
- -> time 0 (at removal of parathyroid as alerted by surgeon)
- -> time 5, 10, and 15 min post parathyroid removal
