Comparing Fluid Responsiveness Assessment Methods in Patients With Impaired Consciousness

Summary

Hypotension is a significant precursor to unfavorable clinical outcomes. To determine whether infusion therapy can positively impact the management of hypotension, several evaluative tests can be utilized. These include assessing the collapsibility and distensibility indices of the inferior vena cava, conducting a passive leg raising (PLR) test, and performing a fluid challenge (FC).

Technologically advanced methods leveraging dynamic testing are capable of real-time prediction of a patient's response to infusion therapy. Nonetheless, the use of systolic pressure variability (SPV), pulse pressure variability (PPV), and stroke volume variability (SVV) is often limited by the prohibitive costs of the necessary equipment. In contrast, the PLR test and FC are not subject to this limitation.

Despite being deemed unreliable by numerous clinical protocols, static measurements of central venous pressure (CVP) or pulmonary capillary wedge pressure (PCWP) persist in usage among certain traditionalists within the medical community. It must be noted that the patient's baseline state and the unique clinical context are pivotal in determining the precision of these methodologies. For example, the PLR test may yield limited information in fully conscious patients, and the prognostic value of CVP measurements is significantly diminished in cases of pneumothorax and hydrothorax.

Regrettably, there is a paucity of data on the prognostic utility of these tests in patients with altered levels of consciousness, despite their growing presence in intensive care units. This gap underscores the necessity for comprehensive studies that evaluate the predictive efficacy of infusion therapy responsiveness in patients with concurrent hypotension and impaired consciousness.

Purpose of the study: to investigate the sensitivity and specificity of methods for assessing fluid responsiveness in patients with hypotension and decreased level of consciousness.

Conditions

• Hypotension
• Cognitive Impairment

Interventions

DIAGNOSTIC_TEST

Inferior vena cava's diameter ratio

In mechanical ventilation, the Inferior Vena Cava's maximum diameter (IVCmax) is measured at peak inspiration, and minimum diameter (IVCmin) at expiration's end. The Distensibility Index (IVCDI) is calculated as \[(IVCmax - IVCmin) / IVCmin\] × 100%. In spontaneous breathing, IVCmax is the diameter at expiration's end, and IVCmin at inspiration's end. The Collapse Index (IVCCI) is \[(IVCmax - IVCmin) / IVCmax\] × 100%. Clinically, an IVCDI/IVCCI ≥ 18% indicates a 'responder'. Values \< 18% denote 'non-responders'.

DIAGNOSTIC_TEST

Central venous pressure

In our protocol, patients lie flat, connected to a saline-filled system for intravenous infusion via a central venous catheter. The system, starting from the subclavian catheter, extends to the 2nd to 3rd intercostal space at the mid-axillary line. The tube's end is raised perpendicular to the bed until saline flow stops, marking the liquid level. The height from the mid-axillary line to this point is measured in millimeters. If the liquid column falls below the mid-axillary line, indicating continuous flow, the CVP is negative, and the catheter is closed to block air entry. CVP readings are taken at exhalation's end. CVP interpretation: * CVP ≤ 12 mmHg (16.3 cm H2O) indicates a responder. * CVP \> 12 mmHg (16.3 cm H2O) indicates a non-responder.

DIAGNOSTIC_TEST

Passive leg raising test

In our protocol, the patient starts flat for initial CVP measurement. Then, the bed is tilted to 45 degrees for the first measurements: Systolic/Diastolic Blood Pressure, Mean Arterial Pressure, and Pulse Pressure (Systolic - Diastolic). Next, the bed is adjusted to elevate the feet, creating a 135-degree angle between torso and legs. After 90 seconds, the second set of measurements, including CVP, is taken. The patient is then returned to the initial position. Interpreting results: A responder is indicated by: * Over 10% Pulse Pressure (PP) increase in the second measurement; * The ratio of PP change to CVP change (∆PP / ∆CVP) \> 1; * Second measurement CVP ≤ 12 mmHg (16.3 cm H2O). A non-responder is indicated by the presence at least one of the following: * Less than 10% PP increase in the second measurement; * The ratio of PP change to CVP change (∆PP / ∆CVP) ≤ 1; * Second measurement CVP \> 12 mmHg (16.3 cm H2O).

DIAGNOSTIC_TEST

Fluid challenge

In our clinical procedure, patients start horizontally for initial measurements: Systolic, Diastolic, Mean Arterial, Pulse Blood Pressures, and Central Venous Pressure (CVP). Then, they receive a balanced crystalloid solution at 4 ml/kg body weight at maximum permissible infusion rate. After infusion, a second measurement set identical to the first is taken. Interpretation: A responder is indicated by: * Pulse Pressure (PP) increase \> 10% in second measurement; * Ratio of PP change to CVP change (∆PP / ∆CVP) \> 1; * Second CVP measurement ≤ 12 mmHg (16.3 cm H2O). A non-responder is indicated by the presence at least one of the following: * PP increase \< 10% in second measurement; * Ratio of PP change to CVP change (∆PP / ∆CVP) ≤ 1; * Second CVP measurement \> 12 mmHg (16.3 cm H2O).

PROCEDURE

Fluid infusion

After assessing infusion therapy responsiveness, patients receive balanced crystalloid solutions at 1000 ml, infused at 15 ml/kg/hour, accounting for any prior infusions. Effectiveness evaluation follows, involving cardiac output reassessment (initially measured upon study enrollment). Effectiveness is determined by a ≥10% increase in cardiac output in the second measurement compared to the first. This is quantified as: \[(CO(after) - CO(before)) / CO(before)\] × 100% ≥ 10%, where CO(after) is the post-infusion cardiac output and CO(before) the pre-infusion output.

Sponsors & Collaborators

• Federal Research and Clinical Centre of Intensive Care Medicine and Rehabilitology

  lead OTHER

Principal Investigators

• Valery Likhvantsev, PhD · Federal Research and Clinical Center of Intensive Care Medicine and Rehabilitology

Study Design

Allocation

NA

Purpose

DIAGNOSTIC

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2024-01-16

Primary Completion

2026-05-20

Completion

2026-05-20

Countries

• Russia

Study Locations