The Effect of Anthropometrics on Desflurane Rise Time

Study Overview
=================
Brief Summary
-----------------
Desflurane is increasingly used in general anesthesia. Its pharmacokinetic properties are known and its distribution is easily modeled. Yet these models fail in practice. In order to increase accuracy, any model should include cardiac output, alveolar ventilation and alveolar dead space, all of which are either hard to measure or impractical, at least. A previous study performed by the same investigator showed that time to target endtidal concentration of sevoflurane is prolonged with increased cardiac output, but only if the patient has increased muscle mass. Although desflurane has lower muscle and fat solubility, our observations suggest a similar prolongation in case of increased muscle mass. The investigators aim to investigate if patient characteristics such as gender, age, height, weight, body type prolongs time to reach target endtidal desflurane concentration in low flow anesthesia.

Detailed Description
-----------------
Low flow anesthesia is a frequently used application in anesthesiology practice. With the widespread use of modern anesthesia devices, the implementation of this application has become easier and its complications have been greatly reduced. It is routinely applied in our clinic, accompanied by both the protocols in the literature and the protocols the investigators have created. Desflurane is the most recently developed inhaler anesthetic agent, and it has advantages such as faster recovery from anesthesia and less metabolism compared to sevoflurane. Although the physicochemical properties of desflurane are known, computer models for its use with low-flow anesthesia are based on desflurane's physicochemical properties, and not on the pharmacokinetic properties of patients. The inhaled induction times obtained with these models do not agree with our observations in practice. In a study conducted in 2021, it was shown that parameters such as cardiac output and alveolar ventilation can increase the accuracy of these models. Among these models, the most frequently used one in the literature is included in the Gas Man simulator, which is also used in anesthesia specialty training. It allows one to perform studies that compare simulation-based and in vivo values are carried out. A similar study was conducted by us with sevoflurane in 2018; A significant difference was found in the rate of increase in alveolar sevoflurane concentration according to cardiac output and muscle mass. Based on this study, the investigators aimed to investigate the effect of the patient's muscle mass evaluated by pragmatic measures such as height, body weight and body type on the rate of increase in the alveolar concentration of desflurane. For this purpose, the investigators aimed to investigate the relationship between the time to reach the targeted alveolar desflurane gas concentration and patient characteristics. The investigators believe that the results of the study will be useful in explaining the factors affecting the induction of general anesthesia with desflurane.

Official Title
-----------------
Does Desflurane Take Longer to Reach Target Endtidal Concentration in Patients With Higher Body Muscle Content: a Pragmatic Study

Conditions
-----------------
Desflurane, Anesthesia, General

Intervention / Treatment
-----------------
* Drug: Desflurane induction


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: age > 18 years planned elective surgery planned inhalational anesthesia planned use of desflurane Exclusion Criteria: emergency surgery use of other inhalational anesthetic agent (sevoflurane, isoflurane, nitrous oxide) disclosed or recognized pregnancy

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Patients scheduled for general anesthesia<br>Patients scheduled for elective general anesthesia will be included, if accepts and signs the informed consent. The inhalational anesthetic should be desflurane. No other inhalational agent should be used during the induction of anesthesia. The inspiratory and expiratory concentration of any inhalational agent should be zero before the induction of anesthesia. | Drug: Desflurane induction<br>* Following tracheal intubation, the fresh gas flow will be set to 1 liters/minute, desflurane vaporizer will be set to maximum.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Rate of rise in expiratory desflurane concentration | Correlation between the time required for the endtidal expiratory desflurane concentration to reach 8% and patient characteristics | intraoperative | 
| Rate of rise in inspiratory desflurane concentration | Correlation between the time required for the endtidal inspiratory desflurane concentration to reach 6% and patient characteristics | intraoperative | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation between occurrence of hypertension and patient characteristics | Correlation between occurrence of hypertension defined as any measurement of systolic arterial blood pressure > 160 mmHg and patient characteristics | intraoperative | 
| Correlation between occurrence of tachycardia and patient characteristics | Correlation between occurrence of tachycardia defined as any measurement of heart rate > 100/minute and patient characteristics | intraoperative | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Anesthetics, Inhalation, Anesthesia, General, Desflurane