Evaluation of pain during high-intensity focused ultrasound ablation of benign thyroid nodules.

OBJECTIVE: To assess severity and factors of pain during high-intensity focused ultrasound (HIFU) ablation of benign thyroid nodules.

METHODS: 128 patients who underwent a HIFU ablation for a benign thyroid nodule were analysed. All patients received a bolus of intravenous pethidine and diazepam before treatment. After treatment, patients were asked to rate their overall pain experience on a visual analogue scale (0-100) (0 = no pain; 100 = worse possible pain) during treatment, 2 h after treatment and the following morning. Binary logistic regression was performed to evaluate associated factors for pain including patient demographics, nodule size, body mass index (BMI) and treatment parameters.

RESULTS: At T1, median (range) pain score was 65.0 (0.00-100.00). Only 16 (12.5 %) patients had a pain score of zero. In multivariate analysis, only lower BMI (OR 1.265, 95 % CI 1.102-1.452, p=0.001) and longer nodule diameter (OR 1.462, 95 % CI 1.071-1.996, p=0.017) were independent factors for pain score at T1 ≤ 65.0.

CONCLUSIONS: A moderate to severe amount of pain was reported during ablation of benign thyroid nodules in over 50 % of patients. Patients' BMI and length of nodule diameter were independent variables for pain during HIFU ablation.

KEY POINTS: • Pain was moderate to severe during HIFU ablation of thyroid nodules. • Only one in eight patients reported no pain during ablation. • Level of energy per pulse did not affect pain. • Patients with lower BMI and larger nodules had less pain.