Can transient increasing breath volume to normal in patients on artificial breathing machine getting low breath volume can measuring blood pressure change, volume of blood pumped from heart per beat and changes in this volume help in identifying which patients will get benefited from giving fluids

Recruiting

• Conditions: Patient undergoing surgeries under general anaesthesia and •Receiving protective lung ventilation less than or equal to 6 ml perkg IBW using Volume Assist Control mode.

• Registration Number: CTRI/2017/04/008380
• Lead Sponsor: Dept of Anaesthesia Critical care and Pain

Brief Summary

**Introduction**

Hypovolemia and hypotension are commonest perioperative hemodynamic disturbance.Fluid administration is the first line of treatment in these patients. Majority of anaesthetized patients undergoing surgery have functional intravascular volume deficit even before surgery that may be due to fasting and bowel preparations. Pre-emptive hemodynamic monitoring and therapy has shown to reduce postoperative morbidity and mortality. Major surgeries causes significant tissue trauma and are associated with systemic inflammatory response leading to vasodilatation, capillary leakage and may be associated with severe haemorrhage, major fluid shifts with third space fluid loss and variable insensible losses that are difficult to estimate leading to inadequately corrected hypovolemia and inappropriate use of vasopressors  even though the blood pressure may be normal. In addition anaesthetic drugs may cause variable degree of vasodilatory and myocardial depressing effects leading to reduced effective intravascular circulating volume and hypotension. All these factors leave patients undergoing surgery at risk of hemodynamic instability and tissue hypoperfusion.

Fluids are commonly administered to prevent and treat hypovolemia. The practice of intraoperative fluid therapy has changed from routine standard therapy measuring and replacing estimated various losses to restrictive fluid strategy which is becoming routine during perioperative period where third space losses are not replaced.  Perioperative fluid approach and goal directed therapy also aim to keep neutral balance has shown to improve patient outcome.Perioperative hypovolemia affects tissue oxygenation leading to organ dysfunction and on the other hand excessive fluid loading is associated with poor wound healing, postoperative wound infection, anastomotic leakage and cardiopulmonary complications. Avoiding fluid overload by restricting fluids has shown early return of bowel function, less length of stay and with fewer complications.Thus the major goal is to maintain adequate volume status and perfusion pressure, avoiding hypovolemia and hypervolemia since both inadequate and excess fluid during intraoperative period affects patient outcome. However, how much fluid to give the patient is unclear and arbitrary fluid therapy may eventually lead to fluid excess or deficit.

Optimizing the fluid balance is of great concern before, during and after surgery. Fluid optimization is effective in preventing subsequent mortality and morbidity only when it is given at an early stage, before organ failure has developed. Delayed circulatory optimization after the establishment of organ failure is probably ineffective and may be harmful6. It is recommended that fluid therapy should be considered only when there is both need to increase cardiac output and patients are fluid responsive.Therefore good hemodynamic assessment is required to identify fluid responders i.e. patients who will benefit by giving fluids. Traditionally used static hemodynamic parameters like central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP) are of limited value in predicting fluid responsiveness.Various dynamic indices which depend on cardiopulmonary interactions like stroke volume variation (SVV) and pulse pressure variation (PPV) are superior to static indices and shown to accurately predict fluid responsiveness in both ICUand surgical patients. Dynamic goal directed therapy (GDTdyn) that used dynamic indices to guide fluid therapy in surgical patients has shown reduced length of stay and post surgical morbidity.

Dynamic indices have their limitations for use with low tidal ventilation i.e. Vt ≤6 mL/kg predicted body weight (PBW) as major limitation precluding its routine use.Low tidal volume ventilation is commonly used in ICU today, it is recommended not only in patients with adult respiratory distress syndrome (ARDS) but also in patients at risk of ARDS, with septic shock, potential organ donors, and patients undergoing high risk intra- abdominal and thoracic surgerie. The traditional use of standard high tidal volume (10mL/kg PBW) during surgery to prevent hypoxia and atelectasis has shown to cause lung injury and more postoperative pulmonary complications leading to worse outcomes. Reducing tidal volume to 6ml/kg PBW during major surgery has shown to reduce postoperative pulmonary complications.Thus low tidal volume ventilation during intraoperative period is currently recommended and commonly practiced.

During low Vt ventilation the magnitude of change in airway driving pressure may not be enough to produce an adequate change in intra-cardiac pressure. Thus PPV and SVV may be low even in fluid responders. This may preclude the use of PPV and SVV during low tidal volume ventilation. To overcome this limitation with the use of PPV and SVV during low tidal volume in critically ill patients we developed a new test called the “tidal volume challenge" This test involves transiently increasing the tidal volume from 6mL/kg predicted body weight (PBW) to 8mL /kg PBW for one minute and thereafter reducing the tidal volume back to 6mL/kg PBW. The change in PPV and SVV following the “tidal volume challenge†(i.e. ΔPPV6-8 and ΔSVV6-8) reliably predicts fluid responsiveness in patients ventilated at low Vt with cut off values of 3.5% and 2.5 % respectively.

Other tests proposed to overcome the limitation of low tidal volume are passive leg raise test (PLRT) and end expiratory occlusion test (EEOT) and lung recruitment maneuver. EEOT is performed by interrupting the tidal ventilation at end expiration for 15 seconds using automatic button in ventilator. This test is not feasible on the anesthesia machines. PLRT requires passive movement of limbs and torso which is not feasible during surgery. Another recent test that used lung recruitment manoeuvre (30 cmH2O Positive end expiratory pressure - PEEP for 30seconds) in operating room patients showed that a 30% decrease in stroke volume (SV) after recruitment manoeuvre reliably predicted fluid responsiveness. Tidal volume challenge is an easy bedside test that can be done at any part during surgery procedure and may work in a similar way when used with SV.Thus, we would like to test the utility of “tidal volume challenge†test in improving the reliability of changes in PPV, SVV and SV in predicting fluid responsiveness in patients ventilated using low tidal volume during intraoperative period, which is a major limitation for the reliable use of these tests during surgery.

**OBJECTIVE:**

To determine whether “tidal volume challenge†can improve the reliability of changes in PPV, SVV and SV in predicting fluid responsiveness in patients receiving low tidal ventilation during intraoperative period.

**MATERIAL AND METHODS**:

All patients enrolled will have a continuous cardiac output monitoring device (The Volume View set from Edwards Life Sciences in combination with EV1000 clinical platform or Flotrac from Edwards Life Sciences).In all patients informed consent will be taken day prior to surgery. During intraoperative period if treating anesthesiologist decides to do continuous cardiac output monitoring that patient will be included in our study. All necessary data will be recorded. Delayed consent will be taken from patient once he/she is conscious. If patient give consent then only his/her data will be included otherwise it will be excluded. The PPV will be recorded using the Philips Intel View Monitor (MP 70) and SVV, SV and cardiac index (CI) will be recorded from cardiac output monitor. The arterial pressure transducer will be attached to the patient’s upper arm at the level of the cardiac cavities. Demographic data of patients including age, sex, height, weight, predicted body weight (PBW), primary diagnosis and details of surgery will be recorded. Patient will be ventilated at tidal volume of 6mL/kg PBW. Dose of vasopressors used if any, will be recorded. The vasoactive medications, anesthetics agents and PEEP would be kept constant during the study period. Indication for the fluid challenge will be noted. Various Respiratory and hemodynamic parameters will be recorded at various intervals as per study design below.

**Study Design**

An arterial blood gas (from the existing arterial line) and a venous blood gas (from the central line if available) will be sampled **ONLY** before performing the test (0.5 ml blood for each will be collected). Lactates, central venous oxygen saturation and partial pressure of carbon dioxide values are noted from the blood gas reports.

All patients will be monitored for any variability in vital parameters at tidal volume of 6 ml/kg PBW. The following set of hemodynamic variables, i.e. heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), cardiac index (CI), PPV, SVV, SV and CVP will be recorded. This set of readings will be recorded at baseline and repeated at various intervals (refer to flowchart). The “tidal volume challenge†will be performed and after one minute a set of readings will be recorded. We will conduct the test and note the various reading only in supine position. The tidal volume will be decreased back to 6 ml/kg IBW. After one minute a set of readings will be recorded. Maximum of two tidal volume challenges will be performed per patient and second tidal volume challenge will be done at least two hours apart.

A fluid challenge of 7 ml/kg actual body weight of Ringer lactate will be given over 10 minutes. Following this a set of readings will be recorded. The ratio of the heart rate and respiratory rate (HR/RR) and difference between Pplat and PEEP will be calculated for each interval. Patients will be divided into two groups Responders and Non-Responders based on increase in Cardiac index >15% after giving the fluid bolus.

**STATISTICS**

Demographic, clinical and disease related variable will be presented as frequency (Percentage) and mean (S.D), Median as appropriate. Change in continuous variable from base line 6ml/ kg to TV 8 ml/kg will be compared using paired t test or Wilcoxon signed rank sum test as per distribution of data. Group comparisons will be made using independent t-test or Man Whitney U test as per the distribution of the data for continuous variables. Categorical variables will be analyzed using Chi-square test or Fisher’s exact test (for binary variable).Correlations between the different scales will be compared with Pearson correlation and Crammers V correlation for categorical. ROC Curve will be used to determine the ability of various preload responsiveness indicators to discriminate between responders and non-responders. p value < 0.05 will be considered statistical significant.

Our study 29has shown that the AUC forPPVis 0.69 in patients ventilated at low tidal volume. Using the Statstodo computer program to calculate the sample size requirement for comparing two receiver-operating characteristic (ROC) curves with expected areas under the curves of 0.69 (PPV6) and 0.90(ΔPPV6–8) for PPV in patients ventilated at low tidal volume assuming an *α* error of 0.05 and power of 80% a sample size of 26 patients/ reading respectively are required. A total of 30consecutive patients/readings will be taken in the study to account for a few dropouts.

Detailed Description

Not available

Study Timeline

• Study Start: 2017-01-05
• Last Update Posted: 2018-06-03

Recruitment & Eligibility

• Status: Open to Recruitment
• Sex: All
• Target Recruitment: 30

Inclusion Criteria

• 1.Adult patients (Age > 18 yrs ) 2.Elective surgeries under general anaesthesia 3.Receiving protective lung ventilation ≤ 6ml/kg IBW using Volume Assist Control mode.
• 4.With cardiac output monitoring using Flotrac/ Volume View with Phillips Intel View monitor (MP70).

Exclusion Criteria

1.Cardiac arrhythmias 2.Previously known significant valvular disease or intracardiac shunt 3.Air leakage through chest drains 4.Right ventricular dysfunction 5.Acute hemorrhage 6.Sudden hemodynamic instability 7.Left ventricular ejection fraction < 40% 8.Abdominal compartment syndrome, and pregnancy.

Study & Design

• Study Type: Interventional
• Study Design: Not specified

Primary Outcome Measures

Name	Time	Method
To determine whether “tidal volume challenge†can improve the reliability of changes in PPV, SVV and SV in predicting fluid responsiveness in patients receiving low tidal ventilation during intraoperative period.	1 year

Trial Locations

Locations (1)

Tata Memorial Hospital; 🇮🇳 Mumbai, MAHARASHTRA, India

Tata Memorial Hospital

🇮🇳Mumbai, MAHARASHTRA, India

Dr Sheila Nainan Myatra

Principal investigator

02224177050

sheila150@hotmail.com