Ability of Pupillometry to Reduce Sufentanil Consumption in Planned Cardiac Surgery: Randomized, Controlled, Single-center Clinical Superiority Trial

The objective of general anesthesia is to obtain a loss of consciousness, stillness, and sufficient analgesia to allow surgery. Thus, general anesthesia has two components: hypnosis and analgesia. Combining these two components, with parallel use of a hypnotic agent and a morphine agent makes major surgery possible by limiting the stress on the body. In clinical practice, hypnosis can be assessed by a monitor of the depth of BIS®-type anesthesia, based on a simplified measurement of the patient's spontaneous cortical electroencephalographic activity. However, BIS® type monitors do not specifically judge analgesia.

Traditionally, analgesia is assessed on the basis of hemodynamic changes (blood pressure, heart rate) in relation to a nociceptive stimulus. There is an interaction between pain and cardiovascular control that is mediated by the baroreflex system. But not all hemodynamic changes during general anesthesia are necessarily secondary to nociceptive stimulation. For example, hypovolemia may be responsible for tachycardia without causing pain; opening the pericardium during cardiac surgery may increase blood pressure by increasing cardiac output.... On the other hand, a decrease in hemodynamic response can be observed in relation to the depressant effect of anesthetic agents, despite a lack of analgesia. Similarly, patients' disease-modifying treatments may mask hemodynamic responses (e.g. beta blocker). Thus, the appearance of tachycardia or high blood pressure during surgery does not necessarily reflect a nociceptive process. Currently, the available data do not allow the anaesthetist to differentiate between real hemodynamic changes related to nociception and sympathicotonia. This leads to typical management consisting of an increase in the dosage of morphine.

Pupillometry (monitoring the pupillary dilation reflex) is a simple and sensitive clinical approach that can be done during general anesthesia to specifically monitor the nociceptive component. The main objective of monitoring is to achieve a more rational use of opioids. This means optimizing opioid dosing, ensuring safety by monitoring the lowering of opioid dosages intraoperatively without the risk of waking up, and reducing postoperative hyperalgesia. In the context of cardiac surgery, the interpretation of hemodynamic changes could be facilitated by nociception monitoring coupled with anesthesia monitoring (BIS). Reducing opiod doses without changing other clinical parameters could ensure better hemodynamic stability in increasingly fragile patients.