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The oxygen concentration (FiO 2 ) and arterial oxygen tension (PaO 2 ) delivered in patients undergoing major surgery is poorly understood. We aimed to assess current practice with regard to the delivered FiO 2 and the resulting PaO 2 in patients undergoing major surgery. We performed a retrospective cohort study in a tertiary hospital. Data were collected prospectively as part of a larger randomised controlled trial but were analysed retrospectively. Patients were included if receiving controlled mandatory ventilation and arterial line monitoring. Anaesthetists determined the FiO 2 and the oxygenation saturation (SpO 2 ) targets. An arterial blood gas (ABG) was obtained 15-20 minutes after induction of anaesthesia, immediately before the emergence phase of anaesthesia and 15 minutes after arrival in the post-anaesthesia care unit (PACU). We defined hyperoxaemia as a PaO 2 of >150 mmHg and included a further threshold of PaO 2 >200 mmHg. We studied 373 patients. The median (interquartile range (IQR)) lowest intraoperative FiO 2 and SpO 2 values were 0.45 (IQR 0.4-0.5) and 97% (IQR 96-98%), respectively, with a median PaO 2 on the first and second ABG of 237 mmHg (IQR 171-291 mmHg) and 189 mmHg (IQR 145-239 mmHg), respectively. In the PACU, the median lowest oxygen flow rate was 6 L/min (IQR 3-6 L/min), and the PaO 2 was 158 mmHg (IQR 120-192 mmHg). Hyperoxaemia occurred in 82%, 73% and 54% of participants on the first and second intraoperative and postoperative ABGs respectively. A PaO 2 of >200 mmHg occurred in 64%, 41% and 21% of these blood gases, respectively. In an Australian tertiary hospital, a liberal approach to FiO 2 and PaO 2 was most common and resulted in a high incidence of perioperative hyperoxaemia.

Many studies have been conducted to investigate the relationship between hyperoxia and mortality in cohorts of intensive care unit (ICU) patients with varied and often contradictory results. The impact of early hyperoxia post ischaemia remains uncertain in various ICU cohorts. We aimed to investigate the association between arterial oxygenation (PaO2) in the first 24 hours in ICU and mortality in patients following cardiac surgery, using a retrospective cohort study of data from the Australian and New Zealand Intensive Care Society adult patient database. Participants were adults admitted to the ICU following cardiac surgery in Australia and New Zealand between 2003 and 2012. Patients were divided according to worst PaO2 level or alveolar-arterial O2 gradient in the 24 hours from admission. We defined 'hyperoxia' as PaO2 ≥300 mmHg, 'hypoxia/poor O2 transfer' as either PaO2 <60 mmHg or ratio of PaO2 to fraction of inspired oxygen <300 and 'normoxia' as between hypoxia and hyperoxia. The primary outcome was mortality at hospital discharge. Secondary outcomes were ICU mortality and ICU and hospital length-of-stay. Of the 83,060 patients, 12,188 (14.7%) had hyperoxia, 54,420 (65.5%) had hypoxia/poor O2 transfer and 16,452 (19.8%) had normoxia. There was no association between hyperoxia and in-hospital or ICU mortality compared to normoxia. There was a small increased hospital and ICU length-of-stay for hyperoxic compared to normoxic patients. We concluded that there was no association between mortality and hyperoxia in the first 24 hours in ICU after cardiac surgery.

The aim of this study was to evaluate the level of pain felt when silicone ring and pneumatic tourniquets were applied to the upper arm and to determine which was more suitable for use in local anaesthetic procedures. Pain was measured using a visual analogue score pain scale on application and at 1, 5, and 10 minutes in 30 volunteers. Volunteers experienced significantly more pain on application and at 1 and 5 minutes with the silicone ring tourniquet. This difference in pain was most marked on application. Two volunteers could not tolerate application of the silicone ring tourniquet. We conclude that the silicone ring tourniquet would not be suitable for local anaesthetic procedures in the upper limb due to the severe pain experienced on application, which may reduce the patients' confidence and adversely affect their experience of the procedure. The pneumatic tourniquet is more suitable for local procedures.