The Influence of Preoperative Anxiety on Heart Rate Variability

Abstract

Introduction: Heart rate variability (HRV) is influenced by anesthesia and intraoperative stress response (1). The effects of preoperative stress are hardly investigated - in fact there is only one study regarding HRV and preoperative anxiety (2). Comparing the results with those described for trait anxiety patients, statements are contradictory: is there a vagal predominance (2) or a reduction of vagal tone (3) caused by anxiety? Methods: After approval by the local ethics committee and written informed consent a total of 50 subjects was investigated. 25 male patients (ASA 1-2, minor elective ENT-surgery) (PAT) were examined on the preoperative day. Additionally 25 male control subjects with no surgical intervention were included (CON). The HRV was recorded for ten minutes and analysed in intervals of 256 beats (acquisition rate 1000 Hz; VariaCardioTF4, Sima Media, Olomouk, Czechoslovakia). For each period a power spectrum was calculated: very low frequency (VLF: 0.02-0.04 Hz), low frequency (LF: 0.04-0.15 Hz), high frequency (HF: 0.15-0.4 Hz), LF/HF-ratio and total power (TP: 0.02-0.4 Hz). Preoperative anxiety was determined by three well established scoring systems: hospital anxiety and depression scale (HADS: divided in anxiety, HADSA, and depression, HADSD, scale), self-rating anxiety scale (SAS) and a visual analogue scale (VAS; 0-100mm). Statistical analysis was performed using t-test, Mann-Whitney-U-test, Chi-Square-test and Pearsons correlation coefficient (r). Data is presented as median. Level of significance was set at a p value of 0.05. Results: A total of 50 persons was analysed. Though there were no differences regarding body mass index, height and weight, CON were significantly younger (25 vs. 32 years, p < 0.05). TP, LF and HF were significantly lower in PAT (TP: 1489 vs. 2581 ms2; LF: 656 vs. 1186 ms2; HF: 491 vs. 964 ms2, p < 0.01), whereas the LF/HF-ratio showed no significant difference. The TP and PCHE did not correlate with the age. PAT had higher HADS (HADSD: 2 vs. 0 points, p < 0.01; HADSA 6 vs. 4 points, n.s.) and VAS scores (10 vs. 2 mm, p < 0.01). The SAS showed no significant differences. The VAS showed a significant negative correlation with the TP (r = - 0.293, p < 0.05). The HADS correlated significantly with the LF/HF-ratio (HADSD r = 0.415, p < 0.01; HADSA r = 0.324, p < 0.05). Conclusions: HRV decreases with preoperative anxiety. The HADS and VAS scale strongly correlate with these findings. In contradiction to Sleigh and Henderson (2) we demonstrated an increase of LF/HF-ratio with increasing anxiety levels, suggesting a reduction of vagal tone due to preoperative anxiety.