Discussion
Based on the unique data we have obtained from our study, we propose that CA patients’ COHb level can be a predictor for ROSC. To our knowledge, this is the first study investigating the relationship between ROSC and COHb and MetHb levels.
In the study by Neukamm et al. (19) investigating the impact of response time reliability on CPR incidence and resuscitation success, 2330 patients were resuscitated in the seven different emergency medical service (EMS) systems. In 46.7%, spontaneous circulation could be achieved. There were no significant differences between the centers for the ROSC rate (42.6% vs. 53.1%, p = 0.32). However, survival after 24 h varied between centers (15.1% vs 30.3% p < 0.001). Discharge rates were between 13.8% and 16.6% (p = 0.50). The ROSC and survival rates found in the current study are compatible with the literature.
In their study, Rohlin et al. (20) investigated the effect of CPR duration on 30-day survival. These authors concluded that the survival rate increased as the CPR duration period was shortened. Similarly, in the current study, the CPR duration was significantly shorter in the ROSC group than in the non-ROSC group. Similarly, in our study, the CPR duration was considerably shorter in the survivor group compared to the non-survivor group.
Gilje et al. (21) investigated the predictive value of cTn in out-of-hospital cardiac arrest (OHCA) patients, and reported that high cTn was an independent risk factor for mortality. Similarly, in our study, the cTn levels were higher in the non-ROSC and non-survivor groups compared to ROSC and survival groups.
In the systemic review by Sasson et al. (22), the predictors for survival in CA cases were investigated. These authors concluded that the survival rates of patients with VF and VT as the initial rhythm were higher than in other rhythms. Similarly, in our study, the amount of VF and VT in the initial rhythm detected in the ROSC group was higher than in the no ROSC group. Additionally, the amount of VF and VT was higher in the survivor group compared to the nonsurvivor group.
Melley et al. (13) evaluated patients who were hospitalized in ICU after cardiothoracic surgery and reported that minimum COHb levels were higher in patients who stayed in intensive care for a short time and discharged compared to patients who died. Fazekas et al. (18)reported that COHb levels in patients with mortality were significantly lower than those discharged in a non-surgical ICU. Additionally, low COHb levels in intensive care patients were associated with high mortality, regardless of the severity of the disease and organ failure type. Kakavas et al. reported that low COHb level was associated with high mortality in the study in which 159 patients were followed up in chest diseases clinic with the diagnosis of PTE involved (11). Similarly, in the current study, the COHb levels in the ROSC group were significantly higher compared to the non-ROSC group. Additionally, the COHb levels of the survivor group were significantly higher compared to the non-survivor group. CO is synthesized naturally in the body and has a very important role in range of physiological functions including vasodilation, angiogenesis, vascular remodeling, protection against tissue damage, and formation of the inflammatory response (8,9). In this current study, the low CO-Hb level in the non-survivors may have been due to the failure to activate the inflammatory system.
Schuerholz et al. reported that MetHb levels were associated with sepsis severity in the intensive care unit patients (14). Kakavas et al. reported that MetHb levels might increase in high-risk PTE patients (11). Conversely, Uzer et al. reported no correlation between MetHb and COHb levels and the severity of PE (17). According to our results, the MetHb levels did not have a predictive value in terms of ROSC in CA patients.
This was a retrospective and single-center study, subject to the limitations in generalizability with this research design.
Conclusions:
The author concluded that the COHb levels in the blood gas analysis at the time of admission could be used as a predictive marker for ROSC in CA patients. It was also emphasized that COHb levels could be used as a post-CPR prognostic marker for mortality prediction. In this regard, we recommend that resuscitation teams consider the COHb level in their CPR termination decisions. On the other hand, MetHb levels had no value as a predictive marker for ROSC and prognostic marker for patients who achieved ROSC. Further randomized controlled studies are needed to confirm the current study findings.
Financial Disclosure: This research received no specific grant from any funding agency in the public, commercial, or not-forprofit sectors
Conflict of Interest: The Authors declare that there is no conflict of interest.