Anesthesia Induction with the Target-controlled Infusion of Propofol in High-risk Patients

The purpose of this study is to compare the risk of hypotension following induction of anesthesia in high-risk patients (American Society of Anesthesiologists risk scores III and IV) using target-controlled infusion (TCI) of propofol versus standard manual induction of anesthesia. Our previously published study compared TCI and manual induction of anesthesia in a general patient population and found that hypotension developed less with TCI induction. This study is a continuation of the other study and will be conducted in high-risk patients.

Hypotension after induction of anesthesia is a very common condition. Despite well-known risk factors and advanced monitoring techniques, hypotension after induction of anesthesia occurs in approximately 30% of patients. The risk of hypotension increases in patients with comorbidities such as hypertension, heart failure, renal failure, diabetes mellitus, patients with high ASA (American Society of Anesthesiologists ) risk scores, geriatric patients, patients undergoing major surgery, and patients with prolonged fasting periods. In order to prevent post-induction hypotension, the risk factors of the patient (such as comorbidities, and surgery) cannot be changed, but this risk can be reduced with different anesthesia induction techniques.

Since anesthetic agents are administered at a fixed dose and rate adjusted according to the patient's weight in standard anesthesia induction, it may cause hypotension in patients with low cardiovascular performance.

The fall in blood pressure is due to a decrease in systemic vascular resistance or cardiac output and may be increased by the concomitant use of other drugs such as remifentanil. Target-controlled infusions (TCI) have been developed to overcome these drawbacks of standard anesthesia induction and maintenance. TCI systems enable titration of anesthetic agents according to the needs of each patient by using pharmacokinetic models through perfusers with special microprocessors. With these features, TCI can provide better control of hemodynamic variations during induction and maintenance of anesthesia. Patients will undergo hemodynamic monitoring using the pressure analytic recording method (PRAM). The functional hemodynamic data provided by this monitoring technique will allow us to better analyze the causes and consequences of hypotension. In this study, investigators aimed to monitor and compare the hemodynamic effects of TCI induction and manual anesthesia induction through PRAM parameters by monitoring patients with high ASA scores before and after induction. Investigators anticipate that these 2 technologies (TCI and PRAM) can provide a better hemodynamic profile in the high-risk patient group with high ASA scores thanks to the advanced monitoring provided to the patient in our anesthesia practice.

Eligibility Criteria:
Inclusion Criteria:

* Patients with the American Society of Anesthesiology physical status 3-4
* Underwent major elective surgery
* Required intra-arterial blood pressure monitoring before induction.

Exclusion Criteria:

* Under 18 years of age
* Patients with the American Society of Anesthesiology physical status 1-2
* Arrhythmia (atrial fibrillation, frequent premature beat)
* Severe valvular heart disease
* Morbid obesity
* Intubation difficulty
* Drug addiction
* Treatment with opiates
* Pregnancy
* Emergency surgery