Estimation of cerebral blood flow and cerebral energy metabolism during asphyxia and post resuscitation in a newborn piglet model of neonatal asphyxia during delayed energy failure

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 12671065
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Embryonic/Neonatal medicine
• Research Institution: Kagawa Medical University
• Principal Investigator: IMAI tadashi Kagawa Medical University Instructor, 医学部附属病院, 講師 (60176477)
• Co-Investigator(Kenkyū-buntansha): OKUBO kensuke Kagawa Medical University Instructor, 医学部, 助手 (80335851) ; KUSAKA takashi Kagawa Medical University Instructor, 医学部附属病院, 講師 (50274288)
• Project Period (FY): 2000 – 2001
• Keywords: delayed energy failure / neonatal asphyxia / 31P-MRS / secondary energy failure / CBF / indocyanine green / multichannel near-infrared spectroscopy

Research Abstract

[Object] It is thought that there exists a "therapeutic time window" for treatment of brain damage caused by neonatal asphyxia during delayed energy failure. Elucidation of the energy dynamics and blood flow dynamics in the brain during asphyxia and post resuscitation is thought to be important for determination of the optimal time for treatment and for reducing the severity of sequela.
[Materials and methods] Newborn piglets were used at less than 24 hours after birth. Hypoxic ischemic loading was carried out by reducing inhaled oxygen concentration to 10% for 30 min and to 8% for 45 min (75 min in total) and by arterial occlusion achieved by applying a pressure of 300 mmHg to the neck of the piglet by the use of a cuff for blood pressure measurement. Cerebral blood flow was measured by multichannel near-infrared spectroscopy using indocyanine green (ICG) and by pulse dye densitometry before loading and at 3, 6, 18 and 24 hours after resuscitation. Cerebral energy status (PCr/Pi was me asured using 31P-MRS before loading and at 3, 18 and 24 hours after resuscitation. The level of pHi in cerebral tissue was calculated by the chemical shift in inorganic phosphorus (Pi) and PCr. EEG was continuously measured.
[Results and discussion] The following results were obtained: 1) values of PCr/Pi at 3 hours after resuscitation were divided into two groups, one group in which PCr/Pi had recovered to almost 80% of the level just before hypoxic-ischemic loading and one group in which PCr/Pi had recovered to only about 15% of the level just before hypoxic-ischemic loading; 2) values of PCr/Pi in the brain at 24 hours after resuscitation were divided into two groups, one group in which PCr/Pi had partially recovered and one group in which PCr/Pi showed almost no recovery; 3) there was almost no cerebral blood flow from 6 hours after resuscitation in the group in which PCr/Pi in the brain at 24 hours after resuscitation was almost zero; and 4) EEG after resuscitation gradually became flat in the group in which PCr/Pi in the brain at 24 hours after resuscitation was almost zero. The results suggest that cerebral blood flow from 6 hours after resuscitation and EEG could be indices of delayed energy failure. Further studies on hypothermia therapy and drug therapy are being planned.