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.