Postoperative hypocalcemia is the most common complication after total thyroidectomy, but severe and symptomatic hypocalcemia is rare. Although symptoms usually develop in the first 24-48h post-op, there are cases of symptoms arising in the fourth post-operative day. With the increasing need of early discharge to reduce health care costs, surgeons need to decide who require calcium and vitamin D supplementation after total thyroidectomy, even if asymptomatic. How to decide who are those patients is not a simple task. Supplementation of all patients is not a valid option since it will increase health care cost with unnecessary treatment of patients who are not at risk of hypocalcemia. Additionally, although absolute post-operative PTH may predict hypocalcemia, this complication can develop in patients with normal post-operative PTH. So... How can we decide?
Every month I receive from hospital's library some international surgical journals. Last month one article got my full attention:
Raffaelli M, De Crea C, D'Amato G, Moscato U, Bellantone C, Carrozza C, et al. Post-thyroidectomy hypocalcemia is related to parathyroid disfunction even in patients with normal parathyroid hormone concentrations early after surgery. Surgery 2016; 159: 78-85.
This study from Università Cattolica del Sacro Cuore of Rome, presents which factors are associated to post-thyroidectomy hypocalcemia in patients with normal postoperative PTH. Secondarily the authors present a protocol for selective calcium/vitamin D supplementation after total thyroidectomy.
From the study of 1504 consecutive patients submitted to total thyroidectomy between January 2012 and December 2013, Raffaelli et al. found some interesting data. PTH was collected preoperatively and 4-hour after surgery. 333 (22,1%) patients had 4-hour PTH bellow normal range and received oral supplementation (most of them for 6 months). From 1171 patients with normal 4-hour PTH 211 (18 % of euparathyroid patients, 14% of total) had symptomatic hypocalcemia and received oral supplementation for 3 months.
From data analysis, risk factors for post-operative hypocalcemia in patients with normal 4-hour PTH were two: preoperative serum calcium; percentage of PTH decline [(preoperative PTH - 4 hour PTH) / preoperative PTH x 100]. A percentage of PTH decline (ΔPTH) ≥ 50% is presented as the cut-off value of maximum accuracy.
The authors concluded that in patients with 4-hour PTH in normal range, a ΔPTH ≥ 50% is an independent risk factor for post-total thyroidectomy hypocalcemia, confirming that normal PTH after total thyroidectomy does not exclude parathyroid insufficiency, which usually occurs because of intraoperative gland trauma. Additionally they give emphasis to the fact that surgeons must not talk about hypocalcemia, but parathyroid insufficiency.
For practical proposes a supplementation protocol is presented in the paper. Since I believe this will be of good help for residents and surgeons, I leave you with a summary of it:
1. Absolute parathyroid insufficiency (hypoparathyroid patients): 4-hour PTH below normal range - oral calcium and vitamin D supplementation (risk of significant hypocalcemia)
2. Relative parathyroid insufficiency: 4-hour PTH in normal range but with a ΔPTH ≥ 50% - discharge with oral calcium supplementation
3. Normal 4-hour PTH with a ΔPTH < 50%: discharge early without supplementation
Now it looks easy...
I hope this post will be of good help in your clinical practice. Please complete your knowledge reading the full manuscript.
Link to PubMed:
Dr. Carlos Eduardo Costa Almeida
Cirurgião Geral