STUDY JUSTIFICATION:

Central venous pressure (CVP) and pulse pressure variations (PPV) are widely recognized as standard measures of a patient’s volume status, particularly in perioperative  settings. These parameters are routinely monitored during coronary artery bypass graft (CABG) surgeries to ensure optimal fluid management and hemodynamic stability.

In the context of cardiac surgeries, particularly CABG, both CVP and PPV can be influenced by a variety of factors such as cardiac function, myocardial contractility, and the surgical manipulation of the heart. Given the complexity of these procedures, the accuracy of these parameters in reflecting true intravascular volume and tissue perfusion can be variable.

One of the critical markers of tissue oxygenation during surgery is the level of lactate in arterial blood gas (ABG) measurements. Elevated lactate levels are indicative of tissue hypoperfusion and anaerobic metabolism, often signaling inadequate oxygen delivery to tissues. This makes lactate a crucial parameter to monitor, as it provides direct insight into the adequacy of tissue oxygenation.

The objective of this study is to determine which of the two hemodynamic parameters—central venous pressure (CVP) or pulse pressure variations (PPV)—has a stronger correlation with lactate levels during CABG surgeries. By identifying the parameter that more accurately reflects tissue oxygenation, we aim to improve intraoperative monitoring and patient outcomes.

Study Hypothesis & Research Question:

HYPOTHESIS:  Given its dynamic nature, we hypothesize that pulse pressure variations (PPV) may serve as a more reliable indicator of volume status during coronary artery bypass graft (CABG) surgeries compared to central venous pressure (CVP). Unlike CVP, which is a static measure, PPV reflects real-time changes in preload and cardiac output, making it potentially more sensitive to fluctuations in intravascular volume.

We postulate that because PPV is more responsive to changes in cardiac preload and contractility, it may correlate more closely with serum lactate levels than CVP. If our hypothesis is correct, PPV could provide a better real-time assessment of the patient’s volume status and tissue perfusion during CABG surgeries, leading to more informed clinical decisions and improved patient care.

METHODOLOGY:

SITE OF THE STUDY: Study conducted inside sterile in operation theatres SRM Medical College Hospital and Research centre.

STUDY POPULATION: All adult patients who were undergoing surgery under OFF-PUMP CABG surgeries a patient who meets inclusion criteria.

SAMPLE SIZE: 88

TYPE OF STUDY: Prospective Observational Study

STUDY TOOLS: Hemodynamic parameters MULTIPARAMETER – PHILLIPS INTELLIVUE MX 550 SYSTEMS.

MATERIALS AND METHOD:

Patients admitted for surgical procedures under general anaesthesia will be included in the study after getting informed consent from them. Patients particulars like Age, Sex, Height, Weight, BMI, ASA status and surgical procedure to be recorded.

The following data surgery related characteristics will be recorded for the all patients

The patients who qualify as per the selection criteria will be given a clear explanation regarding the anaesthesia procedure in their vernacular language.

Demographic data: Age, Sex, Height, Weight, BMI, ASA status Including preop investigations (EF, Serum creatinine, Hb% and urea levels)

Informed consent will be obtained from the patients for elective surgery will be kept fasting  for 8 to 10 hours prior to General anaesthesia surgery and premedicated with Tab. Alprazolam 0.25 mg HS in the night prior to the day of surgery accordingly.

The following data will be collect from the case record before patient shift to the operation theatre. On arrival in the operating theatre, Patients will be Placed supine, start a cannulisation will be done on nondominant hand 18-G and arterial line on Left hand radial artery with BD cannula 16-G and cannula to be secure properly.

An intravenous line will be secure, IV fluid volume Drugs and doses determined by the anaesthesiologist preference.

ECG, pulse oximetry and blood pressure measurement, invasive BP, PPV baseline monitoring initiate and to be monitor.

After application of the routine hemodynamic monitoring according to institutional standards (pulse oximetry, five-lead ECG, and invasive BP monitoring [Multiparameter- Philips IntelliVue MX550 Systems) prior to the induction

Pre-oxygenation will be conduct for a minimum of 3 minutes.

100% oxygen via a tight-fitting facemask with a fresh gas flow of 6 l/min delivery of via a circle system.

All patients included in the study had a standardized anaesthesia technique as per cardiac anaesthesia unit protocol. A balanced anaesthesia technique with midazolam (0.1mg/kg), etomidate (0.1–0.3 mg/kg), with fentanyl (3 mcg/kg) and nondepolarizing muscle relaxants (vecuronium-0.1mg/kg) and Sevoflurane were used for induction of anaesthesia. Anaesthesia was maintain with air, oxygen, and with incremental doses of fentanyl and muscle relaxant.

After induction of the patient under aseptic technique CVP line inserted through the Internal jugular vein site with using of [7 Fr 16 cm with triple lumen is secure] and Base line CVP monitoring to be start and documentation of the intraoperative recording measurements.

Following endotracheal intubation, mechanical ventilation was perform without positive end-expiratory pressure using an inspired oxygen concentration of 50% and tidal volumes of 10 mL/kg to maintain an end expiratory Pco2 at 4 to 4.5 kPa during the study period.

Effectively apply mean tidal volumes, and positive end expiratoryendsexpiratory positive pressures ranged from 4 to 8cm H2O.

Surgical data: Duration of surgery, Arterial BP, MAP, PPV, lactate levels, CVP, Inotropic requirements, IV fluids & Blood products, Urine output, Temperature and Blood loss.

Continuous monitoring: Every 1/2 half hour intraoperatively monitoring and recording the patients’ vital parameters IBP, Central venous pressure, Pulse pressure variations, Systolic BP, Diastolic BP, Mean arterial pressure, Urine output, Temperature.

Monitoring of Serum lactate level before induction and intraoperatively and Blood loss, urine output, Input (Blood products, colloids & crystalloids), duration of the surgery and inotropic requirements. Post operatively: Duration of the mechanical ventilation, Creatinine and Urea levels,  POSTOP - Serum lactate levels up to patient Extubating period, Any mortality and morbidity is noted.