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Background

Prolonged mechanical ventilation can create heterogeneous ventilation patterns, which increase the risk of lung injury in infants. However, little is understood about the risk of brief exposure to mechanical ventilation during anaesthesia. The aim of this prospective observational study was to describe the regional pattern of lung ventilation during general anaesthesia in healthy neonates and infants, using electrical impedance tomography.

Methods

Twenty infants (age 3 days to 12 months), without known lung disease and receiving general anaesthesia with endotracheal intubation for supine positioned surgery, were included in the study. Anaesthesia and ventilation management was at the discretion of the treating clinician. Standardised lung imaging using electrical impedance tomography was made at six time points during anaesthesia from induction to post-extubation. At each time point, the gravity-dependent and right–left lung centre of ventilation was calculated.

Results

Tidal ventilation favoured the dorsal lung regions at induction, with a median (inter-quartile range) centre of ventilation (CoV) of 58.2 (53.9–59.3)%. After intubation, there was a redistribution of ventilation to the ventral lung, with the greatest change occurring early in surgery: CoV of 53.8 (52.3–55.2)%. After extubation, CoV returned to pre-intubation values: 56.5 (54.7–58)%. Across all time points, the pattern of ventilation favoured the right lung.

Conclusions

General anaesthesia creates heterogenous patterns of ventilation similar to those reported during prolonged mechanical ventilation. This potentially poses a risk for lung injury that may not be recognised clinically. These results suggest the need to better understand the impact of general anaesthesia on the developing lung.

Clinical trial registration

Australian New Zealand Clinical Trials Registry (ACTRN 12616000818437, 22 June 2016).

Background

Introducing variability in tidal volume, ventilatory frequency, or both is beneficial during mechanical ventilation in acute respiratory distress syndrome (ARDS). We investigated whether applying cycle-by-cycle variability in the positive end-expiratory pressure (PEEP) exerts beneficial effect on lung function in a model of ARDS.

Methods

Rabbits with lung injury were randomly allocated to receive mechanical ventilation for 6 h by applying a pressure-controlled mode with constant PEEP of 7 cm H₂O (PC group: n=6) or variable PEEP (VEEP) with a coefficient of variation of 21.4%, range 4–10 cm H₂O (PC-VEEP group; n=6). Lung oxygenation index (Pao₂/FiO₂) after 6 h of ventilation (H6) was the primary outcome and respiratory mechanics, lung volume, intrapulmonary shunt, and lung inflammatory markers were secondary outcomes.

Results

After lung injury, both groups presented moderate-to-severe ARDS (Pao₂/FiO₂ <27 kPa). The Pao₂/FiO₂ was significantly higher in the PC-VEEP group than in the PC group at H6 (12.3 [sd 3.5] vs 19.2 [7.2] kPa, P=0.013) and a lower arterial partial pressure of CO₂ at 1–3 h (P<0.02). The ventilation-induced increases in airway resistance and tissue elastance were prevented by PC-VEEP. There was no evidence for a difference in minute volume, driving pressure, end-tidal CO₂, lung volumes, intrapulmonary shunt fraction, and cytokines between the ventilation modes.

Conclusions

Prolonged mechanical ventilation with cycle-by-cycle VEEP prevents deterioration in gas exchange and respiratory mechanics in a model of ARDS, suggesting the benefit of this novel ventilation strategy to optimise gas exchange without increasing driving pressure and lung overdistension.

In an era of ‘big data’, we propose that a collaborative network approach will drive a better understanding of the mechanisms of delirium, and more rapid development of therapies. We have formed the International Delirium Pathophysiology & Electrophysiology Network for Data sharing (iDEPEND) group with a key aim to ‘facilitate the study of delirium pathogenesis with electrophysiology, imaging, and biomarkers including data acquisition, analysis, and interpretation’. Our initial focus is on studies of electrophysiology as we anticipate this methodology has great potential to enhance our understanding of delirium. Our article describes this principle and is used to highlight the endeavour to the wider community as we establish key stakeholders and partnerships.

Background

Iron-deficiency anaemia, occurring in 30–40% of patients undergoing cardiac surgery, is an independent risk factor for adverse outcomes. Our long-term goal is to assess if postoperative i.v. iron therapy improves clinical outcomes in patients with preoperative iron-deficiency anaemia undergoing cardiac surgery. Before conducting a definitive RCT, we first propose a multicentre pilot trial to establish the feasibility of the definitive trial.

Methods

This internal pilot, double-blinded, RCT will include three centres. Sixty adults with preoperative iron-deficiency anaemia undergoing non-emergency cardiac surgery will be randomised on postoperative day 2 or 3 to receive either blinded i.v. iron (1000 mg ferric derisomaltose) or placebo. Six weeks after surgery, patients who remain iron deficient will receive a second blinded dose of i.v. iron according to their assigned treatment arm. Patients will be followed for 12 months. Clinical practice will not be otherwise modified. For the pilot study, feasibility will be assessed through rates of enrolment, protocol deviations, and loss to follow up. For the definitive study, the primary outcome will be the number of days alive and out of hospital at 90 days after surgery.

Ethics and dissemination

The trial has been approved by the University Health Network Research Ethics Board (REB # 22-5685; approved by Clinical Trials Ontario funding on 22 December 2023) and will be conducted in accordance with the Declaration of Helsinki, Good Clinical Practices guidelines, and regulatory requirements.

Clinical trial registration

NCT06287619.

Background

The damage that may be caused to the operating table and patients under general anaesthesia when a large earthquake occurs is unclear. We aimed to evaluate the movement and damage to operating tables and patients under general anaesthesia during an earthquake.

Methods

An operating table with a manikin resembling a patient on it was placed on a shaking table, and seismic waves were input into the shaking table. The effects of seismic waves were evaluated by altering surgical positions (supine and head-down positions), operating tables, flooring material, seismic waves, and output. We observed the movement of the operating table and measured the acceleration of the operating table and manikin head.

Results

Under 90% output of long-period seismic waves, the operating table with the supine manikin was overturned. Under experimental conditions that did not cause rocking, shaking such as tilting of the operating table caused stronger acceleration in the manikin's head than in the operating table. There was no clear relationship between operating table rocking and maximum acceleration as a result of programmed seismic waves. In long-period earthquakes, rocking and overturning occurred >60 s after the onset of shaking, whereas in direct earthquakes, rocking occurred within 10 s.

Conclusions

An earthquake could cause strong acceleration of the patient's head under general anaesthesia, and operating tables may overturn or shake violently. Regarding patient safety, further measures to prevent overturning should be considered.