Anatomy4 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+ |
Calcium50% 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 TreatmentNormal 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+) |
HypocalcemiaAirway | 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 | | | Psychosis | | | Seizures |
| | HyperparathyroidismHYPERCALCEMIA | 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 considerationsArms 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 |
| | HypoparathyroidismHYPOCALCEMIA, 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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