Response to: Carbon monoxide poisoning cases presenting with non-specific symptoms by Deniz. Accuracy of triage with RAD-57 pulse CO-oximeter in suspected collective intoxication of a pediatric population

The diagnostic value of neurogranin in patients with carbon monoxide poisoning: Can it show early neurological damage?

BACKGROUND AND AIM

Carbon monoxide poisoning is a toxicological emergency that causes neurological complications. High serum neurogranin can be detected in acute or chronic conditions where brain tissue is damaged. This study aimed to investigate the diagnostic value of serum neurogranin level and its role in demonstrating neurological damage in patients admitted to the emergency department with carbon monoxide poisoning.

MATERIALS AND METHODS

The study was conducted prospectively on patients with carbon monoxide poisoning (patient group) and healthy volunteers (control group). Demographic characteristics and serum neurogranin level of all participants and symptoms at admission, neurological examination findings, laboratory results, and Diffusion-Weighted Magnetic Resonance Imaging results of the patient group were recorded. We used an independent sample t-test to compare neurogranin levels and bivariate correlation analysis to compare the relationship between serum neurogranin levels and data belonging to the patient group.

RESULTS

Sixty eight participants (patient group, n = 36; control group, n = 32) were included in the study. Serum neurogranin level was significantly higher in patients with carbon monoxide poisoning (0.31 ± 0.16 ng/ml) compared to control group (0.22 ± 0.10 ng/ml) (p = 0.015). The mean Glasgow Coma Scale of the patients with carbon monoxide poisoning was 14.59 ± 0.23, and of Diffusion Weighted Magnetic Resonance Imaging results were completely normal in 94.4% (n = 34). There was no correlation between serum neurogranin level and Diffusion Weighted Magnetic Resonance Imaging results (r = -0.011; p = 0.953).

CONCLUSION

Serum neurogranin level may be a new diagnostic biomarker in patients admitted to the emergency department with carbon monoxide poisoning. The high serum neurogranin levels detected in patients with normal diffusion-weighted imaging after carbon monoxide poisoning suggest that there is neurological damage in these patients, even if imaging methods cannot detect it.

Multi-analyte calibration and verification of a multi-parameter laser-based pulse oximeter

Almost since its introduction pulse oximetry was known to overestimate oxygen saturation in cases of carbon monoxide poisoning or elevated methemoglobin (metHb) levels. To eliminate this dangerous behavior some manufacturers have added additional LED emitters to try to increase the number of measured hemoglobin species and to improve measurement accuracy, but have not been very successful. We hypothesized that the use of narrow-band laser light sources would make accurate and precise measurement of the four primary species of hemoglobin possible, even in cases of elevated levels of carboxyhemoglobin (COHb). Calibration and verification studies were performed on a tissue simulator that employed an artificial finger pulsating with whole human blood. This simulator allowed safe generation of 165 different combinations of the levels of oxyhemoglobin (O₂Hb), COHb, metHb, and reduced hemoglobin (RHb) for calibration of the laser-based pulse oximeter. A follow-on study used 56 mixed hemoglobin levels for verification and statistical analysis of the performance of this device. This laser-based pulse oximeter measured all four species of hemoglobin accurately and precisely (A_RMS ≤ 1.8%) for metHb levels in the clinically normal range. At elevated metHb levels the device continued to provide accurate and precise measurements of metHb and RHb (A_RMS ≤ 1.7%). The use of monochromatic laser light sources can create a new generation of highly accurate, multi-parameter, pulse oximeters.