Delirium in patients with hip fracture is associated with increased heart rate variability

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ORIGINAL ARTICLE

Delirium in patients with hip fracture is associated with increased heart rate variability Gernot Ernst1,2   · Leiv Otto Watne3   · Morten Rostrup4,5 · Bjørn Erik Neerland3  Received: 23 September 2019 / Accepted: 11 December 2019 © Springer Nature Switzerland AG 2020

Abstract Background  Heart rate variability (HRV) is a method to assess the autonomic nervous system and reflects possibly central brain states. HRV has previously not been examined in patients with hip fracture and delirium. Aims  To explore HRV parameters in hip fracture patients with and without delirium. Methods  Patients admitted to Oslo University Hospital with hip fracture and sinus rhythm in electrocardiogram (ECG) were included. Delirium was diagnosed using the confusion assessment method. HRV was assessed preoperatively after a relaxing period of five minutes, by measuring an ECG signal over 5 min. Parameters in time domain (the standard deviation of the QRS distances—SDNN) and frequency domain (total power (TP), low frequency (LF), high frequency (HF) and LF/ HF ratio) were calculated. Results  Seventy-five patients were included in the study, and 21 of them had subsyndromal delirium and were excluded from the analysis. Fifty-four patients with a mean age of 83.5 years (SD 8.6, 78% females) were included. Twenty-six patients (48%) had preoperative delirium, 11 (20%) developed delirium postoperatively, whereas 17 (31%) never developed delirium. SDNN, TP and HF values were significantly higher in patients with delirium compared to patients without delirium, and LF and LF/HF were lower. Patients developing postoperative delirium had decreased LF and increased HF before symptom onset. Discussion  Increased SDNN, TP and HF and decreased LF values might reflect an abnormal stress response in delirium. Conclusion  HRV measurements in patients with hip fractures provide additional information beyond heart rate and might be used to identify relevant pathophysiological factors in delirium. Keywords  Hip fracture · Delirium · Heart rate variability · Autonomic nervous system

Background Older patients admitted to hospitals often develop symptoms of acute cognitive and attentional deterioration, diagnosed as delirium [1]. Delirium is diagnosed based on a formal * Gernot Ernst [email protected] 1



Vestre Viken Hospital Trust, Kongsberg Hospital, Kongsberg, Norway

2



Psychological Institute, University of Oslo, Oslo, Norway

3

Oslo Delirium Research Group, Department of Geriatric Medicine, Oslo University Hospital, Oslo, Norway

4

Section of Cardiovascular and Renal Research, Oslo University Hospital, Oslo, Norway

5

Department of Behavioral Sciences in Medicine, Institute for Basic Medical Sciences, University of Oslo, Oslo, Norway



cognitive assessment and history of acute onset of symptoms, and it has to be distinguished from other syndromes sharing some of the same symptoms, like dementia [2]. Up to 50% of patients with hip fracture experience delirium during their hospital stay [3]. Delirium is preventable in 30–4