QUANtification of Cardiovascular Autonomic Neuropathy (CAN) and the Effects of Anaesthesia on Haemodynamics and Cerebral Perfusion

Rationale: Complications of chronic hyperglycaemia associated with Diabetes Mellitus type 2 (DM2) include macro- and microvascular angiopathy. Cerebral Autoregulation (CA), the capability of the brain to maintain constant cerebral blood flow (CBF) despite changes in blood pressure, is impaired early in DM2 implicating that CBF becomes dependent on blood pressure. In addition, 20-60% of all patients with DM2 suffers from cardiovascular autonomic neuropathy (CAN) resulting in more unstable blood pressure regulation. In patients without DM2 or CAN, induction of anaesthesia results in slightly decreased blood pressure, but cerebral perfusion is maintained through CA. In contrast, patients with DM2 and CAN may display greater reductions in blood pressure and cerebral perfusion may become jeopardized due to impaired CA. This could be an explanation for the increased incidence of stroke in patients with DM2.

Objective:

1. To study whether peri-operative haemodynamics fluctuate more in patients with DM2 and CAN. 2. To study whether CAN further worsens cerebral perfusion in addition to impaired CA.

Study design: Prospective, observational cohort trial. Study population: A total of 45 patients, 30 with DM2 and 15 healthy controls scheduled for elective, non-cardiothoracic surgery under general anesthesia and age 18 years and above will be included in the study. After inclusion, DM2-patients will be categorized in two groups (both 15 patients): patients with and patients without CAN. Given the prevalence of 20-60% CAN, we plan to screen at most 100 patients and include 15 patients in each study group.

Intervention (if applicable):

1. PRE-operative: chart review, short physical examination, autonomic function tests to determine the presence of CAN. These tests are simple physiological tests that can be performed on a regular ward and involve a Vasalva manoeuvre, 3 minute paced breathing with a frequency of 6·min-1 and tests for orthostatic hypotension. Also, we test the sensitivity of the cerebral vasculature to CO2 by measuring during one-minute hyperventilation and one minute CO2-rebreathing. Continuous blood pressure monitoring will be obtained using ccNexfin, a non-invasive monitor that comprises a single inflatable finger cuff. Cerebral perfusion will be assessed non-invasively using transcranial Doppler attached with a headband to the temporal skin area and (non-invasive) measurement of cerebral oxygenation using near-infrared spectroscopy (NIRS). 2. INTRA-operative: we repeat the 3 minute paced breathing test and the CO2-reactivity test.

Main study parameters/endpoints: Between group difference in haemodynamic parameters and cerebral perfusion parameters.