A restrictive oxygenation goal in comatose patients resuscitated after out-of-hospital cardiac arrest doesn’t worsen survival or neurological final result compared with a liberal goal, in keeping with late breaking research presented in a Hot Line session today at ESC Congress 2022.
The findings should reassure clinicians that targeting a partial arterial oxygen pressure (PaO2) of 9 to 10 kilopascal (kPa) in post cardiac arrest patients doesn’t cause harm.”
Jacob Moller, Study Creator, Professor, Odense University Hospital, Denmark
Greater than 750,000 Europeans suffer cardiac arrest every yr and most die before reaching hospital. Amongst those surviving to hospital admission, roughly 40% will die and the primary days of intensive care are critical. Hypoxic-ischaemic brain injury is by far the leading reason behind death.
During resuscitation, the brain is exposed to hypoxia and ischaemia, and when circulation is re-established, reperfusion may cause further injury. To attenuate this, guidelines recommend temperature control with sedation and mechanical ventilation. Observational studies have shown that top blood oxygen content is related to high risk of brain injury and mortality. Animal studies have suggested that an excessive amount of oxygen worsens brain damage after cardiac arrest. Nevertheless, too little oxygen also bears risks. Thus, clinical equipoise exists almost about the advantages of various targets for oxygen therapy in patients resuscitated after cardiac arrest.
BOX examined the effect of two oxygen targets during mechanical ventilation on the composite endpoint of death from any cause or discharge from hospital in a poor neurological state in comatose patients resuscitated after out-of-hospital cardiac arrest. The trial had a factorial design which also allocated patients to one in all two goal blood pressures (reported in one other ESC Congress presentation). The blood pressure intervention was double-blinded and the oxygenation intervention was open-label. The study was performed at two Danish high volume cardiac arrest centres.
A complete of 789 comatose adults were randomised 1:1 after out-of-hospital cardiac arrest of presumed cardiac cause to either restrictive oxygenation targeting a PaO2 of 9-10 kPa or liberal oxygenation targeting 13-14 kPa. The common age of participants was 63 years and 81% were men. Patients received standard targeted temperature management for twenty-four hours at 36 °C.
The first endpoint was a composite of all-cause mortality inside 90 days or discharge from hospital in a state of Cerebral Performance Category (CPC) 3 or 4 (defined as depending on others for day by day activities or worse), whichever occurred first. Secondary endpoints comprised all-cause mortality, and three-month CPC, modified Rankin Scale rating to evaluate disability, and Montreal Cognitive Assessment (MoCA) rating to guage mild cognitive impairment.
The first composite endpoint occurred in 126 of 394 patients (32.0%) within the restrictive oxygen goal group and in 134 of 395 patients (33.9%) within the liberal oxygen goal group (hazard ratio 0.91; 95% confidence interval 0.71-1.16; p=0.59). There have been no differences between groups within the modified Rankin Scale, CPC or MoCA scores.
Professor Moller said: “BOX shows that targeting restrictive oxygenation in comatose patients resuscitated after out-of-hospital cardiac arrest doesn’t alter survival or neurological final result compared with targeting liberal oxygenation. The outcomes suggest that oxygenation targets aiming at PaO2 between 9 and 14 kPa balance the risks of high and low oxygenation well.”
Source:
European Society of Cardiology (ESC)