Abstract
High-risk surgery represents 12.5% of cases but contributes 80% of deaths in the elderly population. Reduction in morbidity and mortality by the use of intervention strategies could result in thousands of lives being saved and savings of up to £400m per annum in the UK. This has resulted in the drive towards goal-directed therapy and intraoperative flow optimization of high-risk surgical patients being advocated by authorities such as the National Institute of Health and Care Excellence and the Association of Anaesthetists of Great Britain and Ireland.Conventional intraoperative monitoring gives little insight into the profound physiological changes occurring as a result of anesthesia and surgery. The build-up of an oxygen debt is associated with a poor outcome and strategies have been developed in the postoperative period to improve outcomes by repayment of this debt. New monitoring technologies such as minimally invasive cardiac output, depth of anesthesia and cerebral oximetry can minimize oxygen debt build-up. This has the potential to reduce complications and lessen the need for postoperative optimization in high-dependency areas.Flow monitoring has thus emerged as essential during intraoperative monitoring in high-risk surgery. However, evidence suggests that current optimization strategies of deliberately increasing flow to meet predefined targets may not reduce mortality.Could the addition of depth of anesthesia and cerebral and tissue oximetry monitoring produce a further improvement in outcomes?Retrospective studies indicate a combination of excessive depth of anesthesia hypotension and low anesthesia requirement results in increased mortality and length of hospital stay.Near infrared technology allows assessment and maintenance of cerebral and tissue oxygenation, a strategy, which has been associated with improved outcomes. The suggestion that the brain is an index organ for tissue oxygenation, especially in the elderly, indicates a role for this technology in the intraoperative period to assess the adequacy of oxygen delivery and reduce the build-up of an oxygen debt.The aim of this article is to make the case for depth of anesthesia and cerebral oximetry alongside flow monitoring as a strategy for reducing oxygen debt during high-risk surgery and further improve outcomes in high-risk surgical patients.
Highlights
Intraoperative hemodynamic optimization in high-risk surgical patients is becoming a gold standard in anesthetic practice in the UK [1]
It is clear that the monitoring standards set by the Association of Anaesthetists of Great Britain and Ireland, that is, electrocardiography (ECG), pulse oximetry, end tidal carbon dioxide and non-invasive blood pressure, give little indication of the adequacy of oxygen delivery (DO2) to the patient during surgery [2]
Repayment of the oxygen debt early in the postoperative period by goal-directed therapy (GDT) guided by sophisticated hemodynamic monitoring achieves beneficial outcomes [5,6], little emphasis has been placed on the potential role of maintaining Oxygen delivery (DO2) intraoperatively and limiting build-up of the oxygen debt
Summary
Intraoperative hemodynamic optimization in high-risk surgical patients is becoming a gold standard in anesthetic practice in the UK [1]. Low MAP and BIS values in those receiving low anesthetic MAC may identify patients who are ‘unusually sensitive to anesthesia and at risk for complications’ confirmed Their suggestion that ‘Inadequate cerebral perfusion is perhaps the most interesting putative cause of low BIS because it is potentially amenable to hemodynamic intervention, such as giving vasopressors or fluids to improve MAP and brain perfusion’ highlights the potential role of cerebral oximetry and flow monitoring alongside BIS in these patients [40]. During surgery nominal nCO and nominal DO2 (nDO2) are maintained within 10% of preinduction values This is achieved by the judicious use of vasopressors such as phenylephrine, commenced preinduction, to maintain venous tone and venous return combined with fluid challenges, based on stroke volume variation (SVV) whilst ensuring optimal depth of anesthesia [66]. Some further work is needed to monitor the specific organs during assessment of volume status
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