Lower preoperative HRV tied to increased postoperative complications
Lower preoperative heart rate variability (HRV) measures, such as total power (TP) and root mean square successive differences (rMSSD), are significantly associated with more overall postoperative complications, according to a new study.
Moreover, decreased preoperative very low frequency power (VLF) and low- to high-frequency power ratio (LF/HF) are associated with postoperative infections.
The study included 150 hip fracture patients (mean age 80.9±0.8 years; 74.5 percent female) undergoing surgery. HRV measures included rMSSD, standard deviation of NN intervals (SDNN), TP, HF, LF, VLF and LF/HF. Patients who had undergone surgery in the previous month, with cancer, who were moribund and who were haemodynamically unstable were excluded.
Patients who experienced postoperative complications had significantly lower preoperative rMSSD (14.9±1.3 vs 18.2±0.9; p=0.043) and TP (2,525±740 vs 1,082±282; p=0.03) compared with patients without complications.
Preoperative VLF was significantly lower in patients who suffered from postoperative infections in general compared with those who did not (44.8±18.6 vs 110.0±12.3; p=0.04). Patients with postoperative urinary tract infections (UTI) also had significantly lower VLF (17.4±7.7 vs 110.0±12.3; p=0.02).
In contrast, while VLF was only marginally lower in patients with postoperative pneumonia (58.5±26.8 vs 110.0±12.3; p=0.091), preoperative LF/VF was significantly reduced in patients with postoperative pneumonia (0.77±0.38 vs 1.98±0.19; p<0.05).
Moreover, an LF/HF <1 was significantly associated with postoperative pneumonia (p=0.017).
The cumulative incidence rate of all complications was 33 percent (n=55). The most common was UTI (n=16; 9.8 percent) followed by pneumonia (n=14; 8.5 percent), death (n=4; 2.4 percent), myocardial infarction (n=3; 1.8 percent) and stroke (n=2; 1.2 percent).