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Nitric oxide (NO) and carbon monoxide (CO) are synthesized at high levels in asthmatic airways. NO can oxidize hemoglobin (Hb) to methemoglobin (MetHb). CO binds to heme to produce carboxyhemoglobin (COHb). We hypothesized that MetHb and COHb may be increased in asthma. COHb, MetHb, and Hb were measured in venous blood of healthy controls (n=32) and asthmatics (n=31). Arterial COHb and oxyhemoglobin were measured by pulse CO-oximeter. Hb, oxyhemoglobin, and deoxyhemoglobin were similar among groups, but arterial COHb was higher in asthmatics than controls (p=0.04). Venous COHb was similar among groups, and thus arteriovenous COHb (a-v COHb) concentration difference was greater in asthma compared with controls. Venous MetHb was lower in asthma compared to controls (p=0.01) and correlated to venous NO (p=0.009). The greater a-v COHb in asthma suggests CO offloading to tissues, but lower than normal MetHb suggests countermeasures to avoid adverse effects of high NO on gas transfer.

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Context Preoperative imaging is performed routinely to guide surgical management in primary hyperparathyroidism, but the optimal imaging modalities are debated. Objective Our objectives were to evaluate which imaging modalities are associated with improved cure rate and higher concordance rates with intraoperative findings. A secondary aim was to determine whether additive imaging is associated with higher cure rate. Design, Setting, and Patients This is a retrospective cohort review of 1,485 adult patients during a 14-year period (2004-2017) at an academic tertiary referral center that presented for initial parathyroidectomy for de novo primary hyperparathyroidism. Main Outcome Measures Surgical cure rate, concordance of imaging with operative findings, and imaging performance. Results The overall cure rate was 94.1% (95% CI 0.93-0.95). Cure rate was significantly improved if sestamibi/SPECT was concordant with operative findings (95.9% vs. 92.5%, p = 0.010). Adding a third imaging modality did not improve cure rate (1 imaging type 91.8% vs. 2 imaging types 94.4% vs. 3 imaging types 87.2%, p = 0.59). Despite having a low number of cases (n=28), 4-D CT scan outperformed (higher sensitivity, specificity, PPV, NPV) all imaging modalities in multi-glandular disease and double adenomas, and sestamibi/SPECT in single adenomas. Conclusions Preoperative ultrasound combined with sestamibi/SPECT were associated with the highest cure and concordance rates. If pathology was not found on ultrasound and sestamibi/SPECT, additional imaging did not improve the cure rate or concordance. 4-D CT scan outperformed all imaging modalities in multiglandular disease and double adenomas, and sestamibi/SPECT in single adenomas, but these findings were underpowered.

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