Abstract
Although cerebrovascular interventions aim to improve long-term neurologic outcome, these procedures are accompanied by a risk of perioperative cerebral hypoperfusion and ischemia. This thesis explored several approaches to improve (neurological) outcome from an anesthetic point of view.
In Part I, perioperative respiratory management was studied by assessing the trends in
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end-tidal carbon dioxide (ETCO2) as seen in clinical practice. In Chapter 2, we found a very large inter-hospital and inter-provider variability in ETCO2 after adjustment for confounders, suggesting that there might still be a lack of evidence to support a specific targeted range. Postoperative pulmonary complications are frequent in neurosurgical patients and can have adverse effects on (neurological) outcome. In Chapter 3, the association between ETCO2 (studying several thresholds) and postoperative pulmonary complications was assessed. Both hypercapnia (ETCO2 >45 mmHg) and severe hypocapnia (ETCO2 <28 mmHg) were associated with an increased risk of pulmonary complications. The latter was also associated with mortality and an increased length of stay. A median ETCO2 around 38 mmHg showed the smallest association with pulmonary complications, but further prospective studies are required to confirm this target.
Part II focused on the effect of ETCO2, blood pressure and cardiac output on cerebral perfusion and neurologic outcome in patients presenting for cerebrovascular interventions. In Chapter 4 we studied the association between several ETCO2 and mean arterial pressure (MAP) thresholds and neurologic outcome in patients presenting for clipping or coiling of a ruptured cerebral aneurysm. We retrospectively included 1,099 patients and found that none of the studied thresholds were associated with a poor neurologic outcome. This study does not show that we can abandon strict ETCO2 and blood pressure regulation; it merely shows that no further subgroups of preferred ETCO2 and MAP values could be identified. In Chapter 5 we conducted a randomized crossover study in ten patients presenting for cerebral bypass surgery to explore the effect of cardiac output on graft flow, as a proxy for cerebral perfusion. Patients randomly and sequentially received dobutamine – to increase cardiac index – and phenylephrine – to increase MAP. Both drugs increased graft flow without a preference for one drug over the other. Dobutamine should be considered when targeted flows are not reached or only at the cost of (severe) systemic hypertension, when using phenylephrine.
The role of the anesthesiologist as “perioperativist” was further explored in Part III, as survivors of an aneurysmal subarachnoid hemorrhage have an increased long-term incidence of cardiovascular events. In Chapter 6, we found that perioperative myocardial injury, reflected in an increased troponin I level after occlusion of a ruptured aneurysm, was associated with future major adverse cardiac events (Chapter 6). In Chapter 7, we studied the effect of routine follow-up visits by specialized anesthesiologists in patients with an elevated postoperative troponin. We included 811 non-cardiac surgery patients with elevated troponins; anesthesiologists were involved in the early detection of 59% of all myocardial infarctions and in 12% of all complications within one week after surgery.
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