Do surgeons obtain intra‑operative parathyroid hormone (PTH) measurements from the subclavian vein during parathyroidectomy?

Intraoperative PTH Sampling During Parathyroidectomy

Surgeons do not routinely draw blood from the subclavian vein for intraoperative PTH monitoring during parathyroidectomy; peripheral venous sampling (typically from the arm) is the standard approach, though central venous sampling from the internal jugular vein may be used in some centers.

Standard Sampling Sites for Intraoperative PTH Monitoring

Peripheral Venous Sampling (Most Common)

• Peripheral venous sampling from the arm is the most widely used approach for intraoperative PTH monitoring during parathyroidectomy 1, 2.
• This method is technically simpler, less invasive, and provides reliable results for confirming successful removal of hyperfunctioning parathyroid tissue 1.
• The rapid PTH assay allows surgeons to assess completeness of parathyroid resection without visualizing all parathyroid glands, facilitating minimally invasive approaches 3.

Central Venous Sampling (Alternative Approach)

• Some centers use central venous sampling from the internal jugular vein (not subclavian) during parathyroidectomy 1.
• Central venous samples yield higher baseline PTH values compared to peripheral samples (median 268 pg/mL vs 191 pg/mL, P = 0.003) 1.
• The kinetics of PTH decay are essentially identical between peripheral and central sampling sites, with mean decay slopes of -0.75 (peripheral) versus -0.76 (central) 1.
• Central samples may require extending the sampling period to 15 minutes rather than 10 minutes to achieve equivalent diagnostic accuracy 1.

Clinical Interpretation and Timing

Standard Criteria for Surgical Success

• A >50% decrease in PTH from baseline is the widely accepted criterion (Miami criterion) for confirming biochemical cure during surgery 2, 4.
• This criterion has a sensitivity of 99.3%, specificity of 92.8%, and positive predictive value of 99.3% when properly applied 2.
• PTH drops instantly after successful parathyroid gland removal due to its half-life of only several minutes 5, 6.

Timing Considerations by Sample Site

• With peripheral sampling, 136 of 147 patients (92.5%) achieved >50% PTH decrease by 10 minutes 2.
• With central venous sampling, 94% of patients showed >50% drop at 10 minutes, increasing to 98% by 15 minutes 1.
• Third-generation PTH assays show more rapid decline after parathyroidectomy compared to second-generation assays, particularly in secondary hyperparathyroidism (10 minutes vs 30 minutes to reach 50% decline) 5.

Selective Venous Sampling (Different Context)

Preoperative Localization Tool

• Selective parathyroid venous sampling from multiple neck and mediastinal veins is a completely different procedure used for preoperative localization, not intraoperative monitoring 5.
• This invasive catheterization technique samples PTH levels from various veins to infer laterality and regional location of parathyroid lesions 5.
• It is reserved for reoperative surgical candidates with recurrent or persistent hyperparathyroidism when noninvasive imaging (ultrasound, sestamibi, CT) yields nonlocalizing or discordant results 5.
• Sensitivities range from 40% to 93% in small retrospective studies 5.

Critical Technical Considerations

Assay Consistency

• The same PTH assay must be used for all serial measurements in the same patient to ensure accurate trend evaluation, as different assay generations can vary by up to 47% 5, 6, 7.
• Second-generation assays measure C-terminal fragments with longer half-lives, potentially overestimating functional parathyroid tissue 5, 6.
• Third-generation assays measure only full-length biologically active PTH and may better reflect parathyroid function in early postoperative hours 5, 6, 7.

Specimen Handling

• Delays in collecting and processing PTH blood samples can complicate intraoperative decision-making and prolong procedures 8.
• Quality improvement initiatives have reduced average total time for transit and assay from 31.36 minutes to 22.06 minutes 8.
• Modern ultrafast systems can measure whole-blood PTH in 5 minutes with 98.6% overall accuracy 4.

Common Pitfalls to Avoid

• Do not confuse intraoperative PTH monitoring (peripheral or central venous sampling during surgery) with selective venous sampling (preoperative invasive localization procedure) 5, 1.
• Avoid switching between central and peripheral sampling sites during the same procedure, as baseline values differ significantly 1.
• Do not rely on absolute PTH cutoff values from guidelines without knowing which assay generation was used, as this can lead to misinterpretation 5, 7.
• Be aware that congenitally variant venous anatomy or prior surgery can cause false regionalization with selective venous sampling 5.