Monitor-Guided Analgesia During General Anesthesia - Part I (MOGADA)

Investigation of the Effect of Opioid Titration Guided by Analgesia Indices During General Anesthesia

This prospective randomized clinical trial evaluates the effects of a monitor-guided opioid analgesia during general anesthesia. To date no standard-monitoring device exists to specifically reflect the analgesic component of general anesthesia. Quality and safety of general anesthesia are of major clinical importance and should be improved by limiting the opioid analgesic's dosage to the minimum amount needed. The study compares the effects of monitoring nociception during general anesthesia with different innovative techniques in comparison to routine clinical practice.

This prospective randomized clinical study aims to investigate the effects of a monitor-guided opioid analgesia during general anesthesia by different monitoring systems in comparison to routine clinical practice. Many surgical procedures require general anesthesia. The main components of general anesthesia are hypnosis and analgesia, and anesthesiologists usually combine a hypnotic drug with an opioid analgesic. Until today, however, there is no standard-monitoring of nociception to specifically reflect the analgesic component of general anesthesia. In clinical practice the opioid dosage is chosen by clinical judgment of the attending anesthesiologist based upon changes of heart rate, blood pressure, pupil size, lacrimation and sweating of the patient. On the one hand, underdosage of opioids can cause nociception leading to an increased sympathetic tone, increase of plasma levels of stress hormones, nociceptive movements as well as increase postoperative pain. On the other hand, overdosage of opioids can lead to drug side effects such as nausea and vomiting, hemodynamic instability, an increase in recovery times, immunosuppression and an increase in postoperative pain by opioid-induced-hyperalgesia. Quality and safety of general anesthesia are of major clinical importance and can be improved by limiting the administration of opioid analgesics to the optimal individual dose needed. In the last years, different analgesia monitoring devices have been developed for monitoring nociception. The present study evaluates the effects of the administration of opioids during general anesthesia guided by three different monitoring systems in comparison to routine clinical practice. After institutional approval by the Ethics committee of the Medical Board of the City of Hamburg, Germany and obtaining patients' written informed consent the investigators randomize elective patients with major abdominal surgery for open radical prostatectomy into one of four treatment groups.

Participants are not informed about the group assignement (intervention takes place in general anesthesia). Outcome assessors are persons without knowledge on former treatment in intervention/control group.

Opioid administration guided by Pain Pupillary Index (PPI) derived from Videopupillometry performed with the device AlgiScan manufactured by IDMed, Marseille, France. The device measures the degree of pupillary reflex dilation (PRD) following an electric nociceptive stimulation. It automatically increases the intensity of the electric stimulation from 10 to 60 milliampere depending on the degree of PRD and afterwards displays the PPI. The numerical index ranges from 0 to 10. A low PPI score indicates a deep analgesia, a high PPI score indicates an insufficient or light analgesia. A PPI score of 2 or 3 is supposed to represent an optimal level of analgesia according to the manufacturer. 5 µg sufentanil will be administered every 5 minutes if PPI score is calculated more than 3.

Opioid administration (sufentanil) guided by by Surgical Pleth Index (SPI) derived from photoplethysmography performed by the device CARESCAPE B650 Patient Monitor from the manufacturer GE (General Electrics) Healthcare, Helsinki, Finland. Included in the monitoring system is a software that continuously calculates the SPI from normalized heart rate and pulse wave amplitude derived from finger plethysmography. The numerical index ranges between 0 (low sympathetic tone) and 100 (high sympathetic tone). A SPI score between 20 and 50 has been proposed as the target range to guide analgesics (15 - 17). 5 µg Sufentanil will be administered every 5 minutes if SPI score is calculated more than 50.

Opioid administration (sufentanil) guided by Nociception Level (NOL) derived from finger photoplethysmography performed with the analgesia monitoring device PMD200 manufactured by Medasense, Ramat Gan, Israel. The device continuously calculates the NOL with a multi-parametric approach from pulse rate, pulse rate variability, pulse wave amplitude, skin conductance level, skin conductance fluctuations, skin temperature and finger motion. The composite algorithm of the device analyses the data and the numerical index NOL is presented on a scale from 0 (no pain) to 100 (extreme pain) (18). A NOL score between 10 and 25 has been proposed as the target range to guide analgesics. 5 µg Sufentanil will be administered every 5 minutes if NOL score is calculated more than 25.

Opioid administration (sufentanil) guided according to standard clinical practice of the attending anesthesiologist based upon changes of heart rate, blood pressure, lacrimation and sweating of the patient.

Elective surgery in radical open abdominal prostatectomy. Opioid titration is guided by analgesia indices during general anesthesia in the experimental arms.

Elective surgery in radical open abdominal prostatectomy. Opioid titration is guided by clinical signs in the control group.

Compares the amount of intraoperative opioid administration (sufentanil) per minute of general anesthesia and per kg bodyweight between groups.

Postoperative recovery time: Time interval between end of operation and tracheal extubation of the patient.

Postoperative recovery time: Time interval between postoperative tracheal extubation and the patient reaching fit-for-discharge criteria from the PACU to the ward.

Amount of postoperative opioid administration (piritramid) in the postanesthesia care unit (PACU). Piritramid is given if NRS score is > 3.

Patient satisfaction with the general anesthesia and pain management evaluated by a numeric rating scale.

Inclusion Criteria: Radical open abdominal prostatectomy scheduled in the operation theater where the study is conducted > 18 years Exclusion Criteria: Chronic pain therapy, e.g. out-of-hospital opioid therapy Beta blocker and digitalis therapy Eye disease with affection of pupil reactivity Pacemaker therapy Higher degrees of cardiac arrhythmias, e.g. atrial fibrillation Pre-operative medication with steroids

Department of Anesthesiology; Center of Anesthesiology and Intensive Care Medicine, Hamburg Eppendorf University Medical Center

Department of Anesthesiology; Center of Anesthesiology and Intensive Care Medicine, Hamburg Eppendorf University Medical Center

Department of Anesthesiology; Center of Anesthesiology and Intensive Care Medicine, Hamburg Eppendorf University Medical Center