Anatomy
4 total |
Posterior aspect of thyroid gland |
Produce and release PTH |
iCal determines level of PTH secretion in body indirectly. Decreased Ca+ = increased PTH |
PTH causes bone resorption, kidney absorption and GI absorption of Ca+ |
Prinicipal cells secrete PTH |
Half-life of PTH is 4-5 minutes |
Alkalosis = decreased Ca+ |
Calcium
50% bound to albumin |
40-45% free/ionized |
5-10% bound/unionized |
ionized levels are regulated and affected by pH and temperature |
low pH (acidotic) = increased ionized Ca+ |
high pH (alkalosis) = decreased ionized Ca+ |
Normal iCal = 4.4-5.4mg/dL |
Normal total calcium = 8.9-10.1mg/dL |
Small changes in iCal leads to large changes in PTH secretion |
Hypercalcemia Lab Values and Treatment
Normal serum Ca+ levels = 8.9-10.1mg/dL |
Normal iCal = 4.75-5.7mg/dL; 1.19-1.33mmol/L |
Mild = <3mmol/L; 12mg/dL |
hydration |
Moderate to severe = 3.2-3.7 mmol/L; 13-15 mg/dL |
NS and lasix |
Other treatments |
Ethacrynic acid - Na+/Ca+ diuresis |
Biphosphonates - inhibit bone resorption |
Calcitonin - hormone to oppose PTH (decrease Ca+) |
Hypocalcemia
Airway |
Neuromuscular & CNS |
ECG |
Recurrent laryngeal nerve damage. Unilateral (hoarseness) Bilateral (stridor, obstruction) |
Muscle cramps |
negative inotropy |
Bleeding - tracheal compression and edema |
Chovstek's sign and Trousseau's Sign |
prolonged QT |
Hypocalcemic tetany - laryngospasm |
Parasthesias |
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Psychosis |
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Seizures |
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Hyperparathyroidism
HYPERCALCEMIA |
Hypercalemia = >10.4 mg/dL |
Primary - most common - due to malignancy or parathyroid malfunction. 30-40 year olds. Single gland is usually benign - 80% prevalence. Secondary - 15% - Hereditary and associated with MEN1 and MEN2A. |
Signs and Symptoms: Renal - Ca+ deposits with recurrent stones. Skeletal - pathologic fractures, skeletal demineralization. CNS - confusion, depression. Neuromuscular - weakness, fatigue. GI - nausea, vomiting, constipation, PUD, anorexia. Cardiac - prolonged PR, short QT, HTN and Osborne J waves. |
Diagnosis: PTH assay with Ca+ level. Will show increased levels of PTH and hypercalcemia. |
Treatment: Mithramycin - inhibits osteoclasts, respiratory alkalosis, Calcitonin (stimulates osteoblasts; inhibits osteoclasts. i.e. Ca + is removed from the blood and used to build bone) |
Most common cause of hypercalcemia is cancer. 25-50% of the time it is breast cancer |
Anesthetic Considerations: Pts will be sensitive to succinylcholine and antagonize non-depolarizing NMBs |
Surgical considerations
Arms will be tucked - IV access |
NIM endotracheal tube to access nerve integrity |
Consider a deep extubation |
Intraop serum PTH. PTH levels should drop 20 minutes after removal |
Post-op hypocalcemia |
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Hypoparathyroidism
HYPOCALCEMIA, HYPOMAGNESEMIA and HYPERPHOSPHATEMIA |
Absence of deficiency of PTH secretion or resistance of peripheral tissues to PTH |
Cause: Iatrogencic (i.e. inadvertent removal during thyroid surgery) |
Signs and Symptoms: neuronal irritability, muscle spasms, tetany, seizures, fatigue, stridor, apnea, CHF, hypotension, prolonged QT, decreased response to beta agonists, fatigue, Chvostek's sign, Trousseau's sign and mental status changes |
Treatment: electrolyte replacement, avoid respiratory alkalosis (decreases Ca+ further), phosphate binders (Sevalamir). Severe hypocalcemia: 10-20 mL (90mg; 0.46mEq/L) of 10% Calcium Gluconate or 3-5 mL (270mg; 1.36 mEq) of Calcium Chloride followed by 1-2mg/kg/hr or Calcium infusion. Calcium is incompatible with sodium bicarbonate |
Anesthetic Management: be mindful that laryngospasm can occur, seizures, prolonged QT (zofran) |
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