Discussion
Severe and prolonged ischemia or hypoxia of any organ causes cell death and tissue damage. The extent of the cerebral injury after the hypoxic-ischemic event, the mechanism of the irreversible damage such as neuronal necrosis or permanent inflammation, and acute phase response, depend on the recovery and the neuronal repair balance. Hypoxia-ischemia-reperfusion injury has been reported to cause a pro-inflammatory chain of events.9,17 In cases of brain damage caused by asphyxia, both microvascular damage and cell injury are vital factors.18 In a study by Wassink et al.19 it was concluded that the hypoxia-ischemia-reperfusion damage in the central nervous system activates a chain of events characterized by leukocyte flow, including polymorphous nuclear cells and monocytes and microglial activation. In an experimental animal study by Hudome S. et al.20 it was reported that neutrophils and lymphocytes increased in the period following ischaemic injury and this increase is usually related to the severity of the injury and long-term neurological results. Shah V. et al.21 reported that despite no correlation between lymphocyte count and outcome, high peripheral neutrophil count was related to worse neurological outcomes. Jenkins DD et al.22 determined a significant increase in leukocyte, neutrophil and lymphocyte levels examined at 0-9 hours in NE cases. In the current study, the first 6-hour laboratory results of the NE and control groups were compared. Mean leukocyte, neutrophil and lymphocyte values were found to be significantly higher in the NE group than in the control group. The leukocyte increase was thought to be due to polymorphonuclear cell activation secondary to hypoxia-ischemia-reperfusion injury.
Therapeutic hypothermia, or TBC, is a treatment method with proven beneficial effects on the outcomes of moderate and severe NE. Low leukocyte levels in the circulation following NE in a newborn have been associated with hypothermia treatment. A greater decrease in leukocyte, neutrophil, and lymphocyte counts has been observed in cases applied with hypothermia treatment. The possible mechanisms for the hypothermia effect include bone marrow suppression and decreased leukocyte expression.23,24 Jenkins DD et al.22compared NE cases applied and not applied with hypothermia treatment and determined that the leukocyte count in the hypothermia treatment group showed a more rapid decrease and reached a significantly lower level within 24 hours compared to the normothermic group. Hypothermia treatment was reported to be related to significantly lower leukocyte and neutrophil values compared to the normothermic cases. Furthermore, the lymphocyte count in the hypothermia group was significantly lower after 36 hours compared to the normothermia group. In the current study, laboratory analyses performed at 0-6, 24 and 72 hours after birth were compared. The mean leukocyte and neutrophil values of the NE group cases measured during therapeutic hypothermia treatment at 24 and 72 hours postpartum showed a significant decrease compared to those measured during the first 0-6 hours of life without therapeutic hypothermia treatment. However, lymphocyte values did not change significantly.
Mean platelet volume is an indicator of thrombocyte function and activation. Large thrombocytes are hemostatic and more active. As young thrombocytes are larger than older ones, thrombocyte counts and MPV are inversely related. MPV appears to be an indicator of thrombocyte production and consumption, in addition to some serious diseases related to hypoxia, perinatal infections, and bone marrow.25,26 In a study of 106 patients stained with meconium amniotic fluid, Tekin et al.27 found the MPV level during the first 2 hours of life to be significantly lower than that of the control group. However, no significant difference was observed in the thrombocyte levels. The low level of MPV was considered to be secondary to hypoxia.27 In a study of 55 cases diagnosed with perinatal asphyxia, Kannar et al. found that the MPV level during the first 24 hours after birth was significantly higher than that of the control group, while the thrombocyte level was considerably lower.28 In the current study, mean thrombocyte and MPV values in the first 6 hours did not differ significantly from those of the control group. The mean thrombocyte values of the NE group at 24 and 72 hours showed a significant decrease compared to the first 6 hours, while the mean MPV levels increased significantly.