Calcium Management in Thyroidectomy Patients - Hypocalcemia

last modified on: Mon, 09/11/2017 - 13:26

Calcium Management in Thyroidectomy Patients - Hypocalcemia

 (return to: Thyroidectomy and Thyroid Lobectomy)

 see also: PTH and vitamin D protocol

 

Introduction:

Hypocalcemia: varies from asymptomatic to life-threatening

  • Most common cause = Hypoparathyroidism which develops status post total thyroidectomy or completion thyroidectomy
    • Occurs 0% to 46% of patients after total thyroidectomy depending on definition1
    •  May be temporary or permanent
  • Cost-utility analysis shows favors routine over selective supplementation of calcium in these cases. 2
     

Prevention:

·        When evaluating the patient prior to surgery, make sure to keep in mind risk factors for postop hypocalcemia.

o       Hyperthyroidism

o       Large goiters

o       Preoperative low serum vitamin D (low sunlight, alcoholism etc)

o       Planned level 6 neck dissection, extensive cancer

 

Symptoms of hypocalcemia:

Acute hypocalcemia causes increased neuromuscular irritability

  • Paresthesias and numbness of the fingertips and perioral area
  • Chvostek's sign: Twitching of the ipsilateral facial musculature (perioral, nasal, and eye muscles) by tapping over cranial nerve VII at the ear
    • Chvostek's sign is neither sensitive nor specific for hypocalcemia: it is absent in 30% of patients with hypocalcemia and is present in roughly 10-15% of normocalcemic patients
  • Trousseau's sign of latent tetany: carpopedal spasm induced by inflation of the blood pressure cuff around the arm
    • More sensitive and specific than Chvostek's sign: present in 94% of hypocalcemic patients and only observed in 1% of normocalcemic patients.
  • Spontaneous muscle cramps
    • Tetany is seen in severe hypocalcemia (ionized Ca level lower than 1.1 mmol/L)

 

Laboratory evaluation: (UIHC Ranges)

·        Serum calcium level lower than 8.5 mg/dL[*|http://wiki.uiowa.edu/#_ftn1]  (critical value < 6.0 mg/dL)

·        Ionized calcium level lower than 3.8 mg/dL  (critical value < 3.2 mg/dL)

  • Biologic effect of calcium is determined by the amount of ionized calcium
    • Not affected by albumin level

 

 

 

Management protocol:

  1. Every total thyroidectomy patient or completion thyroidectomy patient is started on 3 grams of elemental calcium, p.o., per day. This should begin as soon as the patient can take p.o. unless there is a specific contraindication to oral calcium in the patient.
  2. Check ionized calcium q8 hours post-op.
  3. If two consecutive calcium values (within the normal range) are stable or increasing, discontinue checking and patient is tapered off calcium supplementation. Regimen as follows: 1g elemental calcium TID for 1 week, 1g elemental calcium BID for 1 week, 1g elemental calcium Q-day until RTC attending. Of note 2.5g of TUMS (Calcium carbonate) is equivalent to 1g of elemental calcium.
  4. If calcium is decreasing, increase oral calcium to 4 gm elemental per day. If this stabilizes the calcium, arrangements for the above taper regimen beginning at 1 gm QID and tapering down by one gm per week are made at discharge.  Check and correct abnormal magnesium. The patient should have calcium checked 1 week after discharge (locally or at UIHC follow-up). 
  5. If calcium continues to decrease to below 3.8 or the patient becomes symptomatic, add 0.5mcg of 1,25-dihydroxy vitamin D per day, first dose given immediately. If continued decrease in calcium or symptoms, increase to 0.5 mcg BID and consult the Endocrinologist involved.
  6. If the patient requires 1,25-dihydroxy vitamin D, the patient should be sent home on the dose of oral calcium and vitamin D that stabilized the ionized calcium. The patient should have calcium checked 1 week after discharge (locally or at UIHC follow-up). Taper of oral calcium and vitamin D coordinated with the Endocrinologist.  
  7. For patients that are severely symptomatic with last evaluated ionized calcium below 3.8 or for those with a calcium below 3.2, IV calcium may be administered
    1. 1 amp of calcium gluconate [10ml calcium gluconate 10% contains 1g calcium gluconate] in 500 ml of D5W is given IV over 5 hours. Be sure that the IV is functioning well before administration of the calcium. This infusion will usually stop the symptoms. Recheck calcium after the administration. If necessary, this may be repeated. Recheck or check the magnesium level and correct if needed. Maximize oral 1,25-dihydroxy vitamin D and oral elemental calcium in consultation with the Endocrinology service.  Discharge as in #6 above.    

Albumin-Corrected Calcium Management Protocol (as of 9/9/14):

  1. Albumin Corrected Calcium Equation: Corrected Calcium = (0.8 * (Normal Albumin - Pt's Albumin)) + Serum Ca
    1. Normal Albumin is generally 4 
  2. Every total thyroidectomy/completion thyroidectomy patient started on Os - Cal with Vit D (500mg CaCO3 - 200IU VitD3 per tab), 2 tabs (total of 1000mg CaCO3) TID 
    1. Taper over 3 weeks - 2 tabs TID for one week, then 2 tabs BID for one week, then 2 tabs daily for one week, then off
  3. Immediately post op, check a total calcium (and an albumin if none available fro pre-op workup)
    1. If corrected Ca is >8, then no change = continue on 2 tabs Os - Cal with Vit D (500mg CaCO3 - 200IU VitD3 per tab)
    2. If corrected Ca is 7.5 - 8, then add 0.25 calcitriol BID
    3. If corrected Ca is <7.5, add 0.25 calcitriol BID and additional CaCO3 1.5g TID
    4. If <7 or any symptoms develop at any time, treat for acute hypocalcemia with consideration for ionized calcium, EKG, telemetry, endocrine consult, IV calcium -- as clinically indicated (do not discharge!)
  4. Check another Calcium in the morning to see if stable, decreasing, or increasing
    1. follow the above algorithm – as long as not significantly continuing to decline (necessitating a change of the dose of calcium/calcitriol), then discharge
  5. Educate all patients and family the morning of discharge on the signs and symptoms of hypocalcemia; if these symptoms develop at home, they should take an extra dose of 1g of calcium tablets, call the office or hospital, and proceed to a nearby lab/clinic for a serum calcium measurement 
  6. For patients on calcitriol, they should have a serum calcium ordered for 1 week, before beginning to taper

Hazards of IV calcium administration:

  • Too rapid IV: cardiotoxicity, hypotension, local thrombophlebitis, tingling sensation, calcium taste, flushing, nausea, vomiting, sweating
  • Irritation on extravasation
  • SC, IM routes are NOT USED because of severe sloughing and necrosis
  • If overdose - IV Magnesium sulfate
  • CAUTION in dialysis patients and those with kidney disease
  • Serum calcium/Ionized calcium levels should be closely monitored

Above protocol does NOT apply to patients with kidney failure/on dialysis

 

References:

1. Mehanna HM, Jain A, Randeva H, Watkinson J, Shaha A. Postoperative hypocalcemia-The difference a definition makes. Head & neck 2009.

----[*|http://wiki.uiowa.edu/#_ftnref1]  Serum calcium level varies with level of serum albumin (calcium binding protein)

One must correct for calcium level when albumin is abnormal

Corrected calcium (mg/dL) = measured total Ca (mg/dL) + 0.8 (4.0 - serum albumin [g/dL]), where 4.0 represents the average albumin level

2. Wang TS, Roman SA, Sosa JA. Postoperative calcium supplementation in patients undergoing thyroidectomy. Curr Opin Oncol. 2011 Nov 9.