A forest environment in cardiac intensive care: feasibility studied, not proven effectiveness

Time cues as the starting hypothesis

Postoperative delirium, or acute confusional state, is a serious complication after cardiac surgery. It is associated with disrupted sleep and circadian rhythms. Intensive care units often lack natural time cues, which could worsen this disruption.

The researchers’ hypothesis is therefore to modify the environment to support these rhythms. This biological rationale does not, however, demonstrate that a forest setting or light exposure prevents delirium.

A study designed primarily to test implementation

The study was conducted in an Austrian intensive care unit specializing in cardiac surgery. It included 77 adults undergoing elective surgery, of whom 64 were included in the final analysis. Three groups were planned: forest environment, light exposure and usual care.

The interventions were applied for 12 hours a day. The abstract specifies neither the exact characteristics of the forest environment nor those of the light. Delirium was assessed at three postoperative time points using two tools, the CAM-ICU and the ICDSC.

The primary objective concerned recruitment, the feasibility of integrating the interventions into care and their safety. Delirium assessment was a descriptive secondary objective, not a demonstration of effectiveness.

Too few positive assessments to compare groups

Across all groups, delirium was detected in 5 of the 130 assessments performed with the CAM-ICU and in 8 of the 115 assessments performed with the ICDSC. These denominators refer to assessments, not patients: they cannot be used to directly calculate the proportion of people affected.

The authors state that these results did not allow a statistical comparison between groups. Several assessments were missing because of sedation, early discharge from intensive care or transfer. Operational constraints also led to deviations from randomized allocation.

Evidence of feasibility, not a guarantee of safety

No intervention-related adverse events were reported, and neither patients nor care staff reported concerns about the interventions. This finding remains limited to this small sample and the study conditions.

The useful finding therefore mainly concerns how care is organized: these interventions can be implemented, despite logistical difficulties. To establish any potential benefit against delirium, the authors propose larger trials in high-risk populations.

What we can take away

This study supports the feasibility of testing environmental interventions in cardiac intensive care. It does not demonstrate that a forest environment or light exposure reduces delirium.