High pre-operative urinary norepinephrine is an independent determinant of peri-operative hemodynamic instability in unilateral pheochromocytoma/paraganglioma removal.

Background: Peri-operative hemodynamic instability (HDI) may increase peri-operative morbidity in pheochromocytoma/paraganglioma (PPGL) patients.

Objective: This study aimed to determine which tumor-related risk factors could lead to peri-operative HDI in unilateral or single PPGL removal.

Methods: Before surgery, 66 PPGL patients had at least two sets of 24 h urine collected for fractionated catecholamine analysis. At surgery, an arterial line was inserted to record systolic blood pressure (SBP), diastolic BP, and mean arterial BP (MAP). Peri-operative HDI was defined as hypertension (SBP > 160 mmHg) and/or hypotension (SBP < 90 mmHg and/or MAP < 60 mmHg) for >10 consecutive minutes either intra-operatively or within the first 12 h after surgery. Urinary fractionated catecholamines and other variables were compared between those with peri-operative HDI (group I) and those without (group II).

Results: A total of 15 (22.7 %) patients belonged to group I, while 51 patients belonged to group II. One (1.5 %) patient died 9 days after surgery. Relative to group II, group I had significantly higher urinary norepinephrine (NE) (5,488.0 vs. 1,980.0 nmol/L, p < 0.001), urinary normetanephrine (5,130.9 vs. 3,853.4 nmol/L, p = 0.045), maximum SBP at operation (188.2 vs. 167.4 mmHg, p = 0.037), but lower MAP after operation (78.9 vs. 91.8 mmHg, p = 0.026). Urinary NE (OD 1.02, 95 % confidence interval [CI] 1.01-1.03, p = 0.046) was an independent risk factor for peri-operative HDI. The urinary NE level significantly correlated with maximum intra-operative SBP and MAP (r 0.692, p < 0.001; and r 0.669, p < 0.001, respectively) and inversely correlated with maximum post-operative MAP (r -0.305, p = 0.040).

Conclusions: High pre-operative urinary NE was an independent tumor-related factor for peri-operative HDI and significantly correlated with sustained intra-operative hypertension and post-operative hypotension.