Circulatory Recovery Is as Fast With Air Ventilation as With 100% Oxygen After Asphyxia-Induced Cardiac Arrest in Piglets

Abstract

ABSTRACT:We investigated return of spontaneous circulation and of cerebral oxygenation after asphyxia-induced cardiac arrest, using ventilation with air, throughout, or with 100% oxygen for a shorter or longer period. Arterial pressure, heart rate, regional cerebral oxygen saturation (CrS O2 ), and brain tissue oxygen tension (Pbt O2 ) were measured in 1-d-old piglets that were hypoventilated with air and left in apnea until cardiac arrest. They were randomly assigned to be resuscitated with air (n ϭ 13), or with oxygen for 3 (n ϭ 12) or 30 min (n ϭ 13) and then with air. Nine, 10, and 10 animals, respectively, needed closed chest cardiac massage. One, none, and one, respectively, died. Median (quartile range) times from start of ventilation until heart rate reached 150 bpm were 67 (60 -76), 88 (76 -126), and 68 (56 -81) s. They were not significantly different, nor were the arterial pressure responses, times until CrS O2 reached 30%, or times until Pbt O2 had increased by 0.1 kPa from its nadir. Peak Pbt O2 values during resuscitation T he optimal fraction of inspired O 2 (FiO 2 ) for resuscitation of asphyxiated neonates is still not settled, although clinical and experimental evidences indicate that 21% is superior to 100% (1-4). In most of these studies, the time of exposure to pure oxygen exceeded 5 min, and it is unknown whether a very brief exposure to high FiO 2 at the start of resuscitation might improve myocardial oxygenation and hasten the return of adequate heart function without causing an organ damage.In three studies of experimental asphyxia (5-7), arterial pressure was restored as quickly by air ventilation as with 100% oxygen. However, few of the animals in these studies needed closed chest cardiac massage (CCCM), and the possibility remains that subjects with asphyxia, so severe that CCCM is needed, might be easier to resuscitate with a high FiO 2 . We tested this in 1-d-old piglets in cardiac arrest caused by severe asphyxia and hypothesized that ventilation with 100% oxygen would restore heart rate (HR) and arterial pressure faster than would ventilation with air. In addition, return of cerebral oxygenation was analyzed, by measuring regional oxygen saturation (CrS O2 ) and brain tissue oxygen tension (Pbt O2 ). The asphyxia was induced by hypoventilation followed by apnea to achieve the high blood PCO 2 levels that are characteristic of severe clinical perinatal asphyxia (8).Because the Pbt O2 is relevant to the question whether a high FiO 2 after asphyxia might cause brain damage, we extended the recording of brain oxygenation beyond the immediate resuscitation phase. Ventilation with 100% oxygen was limited to 3 min in some animals to see whether this could avoid cerebral hyperoxia. METHODSThis study was approved by the Animal Ethics Research Committee of Lund University. The animals were cared for and handled in accordance with European Guidelines for Use of Experimental Animals.Animal preparation. Thirty-eight domestic piglets (12-to 36-h old) were premedicated with intramuscular ketamin...

Part 7: Neonatal Resuscitation

“…[216][217][218][219][220][221][222][223] 222 One demonstrated more rapid restoration of cerebral blood flow but no difference in histologic brain injury scores. 224 For the critical outcome of oxidative injury, we found 10 animal studies reported on oxidative injury with varying results 212,213,216,[219][220][221][222][223][225][226][227] (very-low-quality evidence, downgraded for potential bias, inconsistency, and indirectness).…”

“…For the critical outcome of ROSC, we found 8 animal studies (lambs/pigs/ rats) [216][217][218][219][220][221][222][223] all demonstrating no advantage to 100% over 21% during CPR (very-low-quality evidence, downgraded for bias and indirectness).…”

Part 13: Neonatal Resuscitation

“…Animal evidence shows no advantage to 100% oxygen during CPR. [179][180][181][182][183][184][185][186] However, by the time resuscitation of a newborn infant has reached the stage of chest compressions, efforts to achieve return of spontaneous circulation using effective ventilation with low-concentration oxygen should have been attempted. Thus, it would appear sensible to try increasing the supplementary oxygen concentration.…”

Resuscitation with 100% oxygen increases injury and counteracts the neuroprotective effect of therapeutic hypothermia in the neonatal rat

“…Evidence from animal studies shows that supplemental oxygen during resuscitation causes significant hyperoxia in the newborn brain (16,17), with increased generation of reactive oxygen species (18), oxidative stress (19), inflammation (20), and cerebral injury (19,21,22). Clinical studies have shown that resuscitation with 100% oxygen has no advantage over air but causes increased mortality (23) and increased time to first breath and/ or cry (24)(25)(26).…”