The impact of autonomic dysfunction on peri-operative cardiovascular complications.

Cardiovascular autonomic neuropathy is frequently observed in patients with diabetes mellitus. As anaesthesia has a marked effect on peri-operative autonomic function, the interplay between diabetic neuropathy and anaesthesia may result in unexpected haemodynamic instability during surgery. The objective of this literature review was to examine the association of cardiovascular autonomic neuropathy with peri-operative cardiovascular complications. We searched PubMed for articles with search elements of autonomic dysfunction [MeSH] AND anaesthesia [MeSH] AND complications [MeSH]. Depending on the type of anaesthesia, the presence of cardiovascular autonomic neuropathy in surgical patients can markedly affect peri-operative haemodynamics and postoperative recovery. Pre-operative testing of the extent of autonomic dysfunction in particular populations, like diabetics, may contribute to a reduction in haemodynamic instability and cardiovascular complications. Non-invasive diagnostic methods assessing autonomic function may be an important tool during pre-operative risk assessment.

Cardiovascular autonomic function testing under non-standardised and standardised conditions in cardiovascular patients with type-2 diabetes mellitus.

Autonomic function tests require standardised test conditions. We compared testing under non-standardised and standardised conditions and investigated the agreement between heart and pulse rate variability in 30 subjects with diabetes mellitus. Deep breathing, Valsalva manoeuvre and quick standing tests showed non-standardised reproducibility intraclass correlations (95% CI) of 0.96 (0.82-0.99), 0.96 (0.81-0.99) and 0.75 (-0.98 to 0.94), respectively. Intraclass correlations for sustained handgrip and quick standing were poor. Heart and pulse rate variability showed high-frequency band intraclass correlations (95% CI) of 0.65 (-0.07 to 0.89) and 0.47 (-0.88 to 0.85) for the very low-frequency band, respectively, 0.68 (0.00-0.90) and 0.70 (-0.09 to 0.91) for the low-frequency band, and 0.86 (0.57-0.95) and 0.82 (0.39-0.95) for the high-frequency band. Reproducibility under standardised conditions was comparable. The mean difference (95% limits of agreement) between heart and pulse rate variability was 0.99 (0.80-1.22) for very low frequency, 1.03 (0.88-1.21) for low frequency and 1.35 (0.84-2.16) for high frequency, with a Spearman's correlation coefficient of 1.00, 0.99 and 0.98, respectively. We demonstrated a high agreement between heart and pulse rate variability and acceptable reproducibility with most autonomic function tests, heart and pulse rate variability.

Reproducibility of non-standardised autonomic function testing in the pre-operative assessment screening clinic*.

By convention, autonomic function tests are undertaken under standard test conditions that limit their implementation during routine pre-operative assessment. We therefore evaluated the comparability of autonomic function tests under both non-standardised and standardised test conditions in 20 healthy male subjects. Autonomic function was assessed using an ECG monitor and a continuous non-invasive blood pressure measurement device. Under non-standardised conditions, intraclass correlation for heart rate variability analysis was good for the low and high frequency bands (0.87; 95% CI 0.58-0.96 and 0.83; 95% CI 0.56-0.94, respectively), but moderate (0.65; 95% CI 0.14-0.86) for the very low frequency band; reproducibility was high for the expiration/inspiration ratio (0.89; 95% CI 0.71-0.96), Valsalva ratio (0.76; 95% CI 0.37-0.91) and handgrip test (0.76; 95% CI 0.35-0.91) (all p<0.05) but was low for the response to quick standing. Reproducibility under standardised conditions was comparable to the above values. We demonstrated that reproducibility for most autonomic tests under non-standardised conditions is acceptable and suggest that implementation of these tests during pre-operative assessment may be feasible.