Target-controlled Infusion Anesthesia and Post-induction Hypotension

Hemodynamic changes during induction of anesthesia may have adverse outcomes and should therefore be avoided. The decrease in blood pressure during induction of anesthesia with propofol 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 infusion (TCI) system aims to reach the theoretically targeted blood or brain concentration of anesthetic agents based on the patient's age, weight, and height, with computer-assisted algorithms. In manual anesthesia induction, anesthetic agents are administered at a fixed dose and rate adjusted according to the patient's weight, which may cause hypotension in patients with low cardiovascular performance. As target-controlled infusion (TCI) obviates the need to calculate the infusion rate manually, the use of TCI may provide a better hemodynamic profile during anesthesia induction This study was designed to test the hypothesis that propofol by TCI anesthesia induction is associated with a lower hypotension rate when compared with manual anesthesia induction

Maintaining normotension is one of the top priorities for anesthesiologists due to its negative effects. Although there are a lot of studies and knowledge on the topic approximately 20-30% of patients develop post-induction hypotension. Mostly it occurs due to the adverse effects of anesthetics such as a decrease in systemic vascular resistance or cardiac output and the interplay between them. The risk can be minimized in two steps: first by identifying high-risk patients, and second with tight control of hemodynamic parameters. As a second step, tight hemodynamic control during induction may be done using target-controlled infusion (TCI) systems, which systems help to adjust the dosage to the needs of each patient by measuring hypnotic effects through the bispectral index (BIS). TCI models for propofol have been previously compared with manual infusions, however, it is not clear whether it still contributes to or triggers hemodynamic deterioration. Therefore in this study, the investigators' aim is to determine the effect of two different anesthesia techniques on the development of postinduction hypotension through hemodynamic parameters monitored by the pressure recording analytical method (PRAM). The secondary aim is to identify risk factors that can predict postinduction hypotension

Single-center, prospective, non-blinded, randomized controlled trial, Patients were allocated to 2 groups: Group 1 Patients who underwent anesthesia induction with target-controlled infusion, Group 2: Patients who underwent manual anesthesia induction

Patients who were assigned to have a manual anesthesia induction group, propofol was administered 2-3 mg/kg in 1-2 minutes to achieve a level of hypnosis measured by bispectral index ( BIS ) of 35-60.

Patients who were assigned to have TCI induction had the target effect site concentration (Ce) of propofol (Ce) set at 3 μg ml-1 using the Schneider model and subsequently modified to achieve and maintain a level of hypnosis measured by BIS of 35-55

In manual anesthesia induction, anesthetic agents are administered at a fixed dose and rate adjusted according to the patient's weight

Target controlled infusion (TCI) system aims to reach the theoretically targeted blood or brain concentration of anesthetic agents based on the patient's age, weight, and height, with computer-assisted algorithms.

Systolic arterial pressure (SAP), measured before and after anesthesia induction was assessed to determine of post-induction hypotension in patients undergoing general anesthesia induction with TCI (target controlled infusion) or manual

Systolic arterial pressure (SAP- mm/Hg) was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). SAP is a parameter used to assess the pressure of the arterial system during cardiac systole

Diastolic arterial pressure (DAP), measured before and after anesthesia induction was assessed to determine of post-induction hypotension in patients undergoing general anesthesia induction with TCI (target controlled infusion) or manual

Diastolic arterial pressure (DAP, mm/Hg) was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). DAP is a parameter used to assess the pressure of the arterial system during cardiac diastole.

Mean arterial pressure (MAP), measured before and after anesthesia induction was assessed to determine of post-induction hypotension in patients undergoing general anesthesia induction with TCI (target controlled infusion) or manual

Mean arterial pressure (MAP, mm/Hg) was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). MAP is a parameter used to assess organ perfusion

Arterial elastance (Ea) measured before anesthesia induction was investigated whether is a predictive parameter for post-induction hypotension in patients undergoing general anesthesia with TCI or manual

Ea ((mmHg m-2ml-1)is an indicator of cardiac afterload and arterial tone and can be calculated by the ratio of the end-systolic pressure (ESP) and stroke volume (SV) obtained from arterial wave analysis. Ea was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy) before the anesthesia induction

Stroke volume variation (SVV), measured before anesthesia induction were assessed for prediction of post-induction hypotension in patients undergoing general anesthesia induction with TCI and manual

Stroke volume variation (SVV,%), was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). SVV is a parameter used to asses cardiac preload and fluid responsiveness

The duration of the study was defined from one minute before induction to 10 minutes after induction]

Pulse pressure variation (PPV), measured before anesthesia induction were assessed for prediction of post-induction hypotension in patients undergoing general anesthesia induction with TCI or manual

Pulse pressure variation (PPV,%) was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). PPV is a parameter used to asses cardiac preload and fluid responsiveness.

Cardiac power output (CPO), measured before anesthesia induction were assessed for prediction of post-induction hypotension in patients undergoing general anesthesia induction with TCI or manual

Cardiac power output (CPO, Watt) was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). CPO is a parameter used to asses cardiac reserve

Cardiac index (CI), measured before anesthesia induction were assessed for prediction of post-induction hypotension in patients undergoing general anesthesia induction with TCI or manual

Cardiac index (CI, L/min/m2), was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). CI is a parameter used to asses cardiac stroke volume

Dp/Dt, measured before anesthesia induction were assessed for prediction of post-induction hypotension in patients undergoing general anesthesia induction with TCI or manual

Dp/Dt(mmHg/msn), was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). Dp/Dt is a parameter used to asses cardiac contractility.

Heart rate (HR), measured before anesthesia induction were assessed for prediction of post-induction hypotension in patients undergoing general anesthesia induction with TCI or manual

Heart rate (HR/bpm) was monitored using the uncalibrated pulse contour device MostCare (Vytech, Vygon, Padova, Italy). HR is a parameter used to assess the cardiac rate.

Inclusion Criteria: Patients with the American Society of Anesthesiology physical status 1-3 Underwent major elective surgery Required intra-arterial blood pressure monitoring before induction. Exclusion Criteria: Under 18 years of age Arrhythmia (atrial fibrillation, frequent premature beat) Severe valvular heart disease Morbid obesity Intubation difficulty Drug addiction Treatment with opiates Pregnancy Emergency surgery

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