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.

Hypotension often precedes adverse clinical outcomes, prompting an investigation into the efficacy of infusion therapy in its management. The study employs a variety of tests for assessment, including evaluation of the inferior vena cava's collapsibility and distensibility indices, passive leg raise (PLR) tests, and fluid challenge (FC) procedures.

Dynamic testing methods, including systolic pressure variability (SPV), pulse pressure variability (PPV), and stroke volume variability (SVV), offer predictions of real-time responses to infusion therapy. However, the high costs of the necessary equipment restrict widespread application. In contrast, passive leg raise (PLR) and fluid challenge (FC) tests are more accessible due to lower costs.

Despite skepticism in various clinical protocols regarding reliability, traditional measures such as central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) continue to be favored in certain medical circles. Considering the patient's baseline condition and specific clinical context is critical when applying such methods. For instance, the PLR test may be less informative in fully conscious patients, and the value of CVP measurements decreases in cases like pneumothorax and hydrothorax.

A notable deficiency exists in data concerning the prognostic value of tests in patients with altered consciousness levels, a scenario frequently encountered in intensive care settings. This situation underscores the urgent need for comprehensive research into the predictive accuracy of infusion therapy response in patients who have coexisting hypotension and impaired consciousness.

The study aims to examine the sensitivity and specificity of fluid responsiveness assessment methods in hypotensive patients with reduced consciousness. The protocol begins by measuring the diameter of the inferior vena cava, followed by an evaluation of central venous pressure. After a brief interval, the passive leg raise (PLR) test is performed, succeeded by a 15-minute waiting period. Subsequently, an infusion load test is carried out. Next, a balanced crystalloid solution of 1000 ml at a rate of 15 ml/kg/h is administered, taking into account any previous infusions during the fluid challenge.

In the study, adherence to the intention-to-treat principle is planned for all analyses. Data distribution will be assessed using the Kolmogorov-Smirnov test with Lilliefors correction or the Shapiro-Wilk test. Descriptive data will be presented as percentages, means ± SD for normally distributed variables, or medians ± interquartile ranges for non-normally distributed variables. Qualitative characteristics will be reported as frequencies. P-values and confidence intervals will be provided for all comparative outcomes between two groups. All statistical tests will be two-tailed, with a significance threshold set at p < 0.05.

Outcomes for all binary variables, including primary and secondary outcomes, will be compared using the Chi-square test or Fisher's exact test, accounting for stratification variables. Comparative intergroup analysis of quantitative variables will be based on the Mann-Whitney U test or Student's t-test, depending on data distribution characteristics. Baseline data will include diagnostic test results such as true positives, true negatives, false positives, and false negatives. Diagnostic accuracy will be assessed using Area Under the Receiver Operating Characteristic curve (AUROC) and Area Under the Precision-Recall curve (AUPC). AUROC comparisons will be made using the DeLong method, with the optimal cutoff in ROC analysis determined according to Youden's index. Sensitivity, specificity, and predictive values of positive and negative results will also be evaluated. Cohen's Kappa will be used to assess test consistency.

Inclusion Criteria:

• Age ≥ 18 years.
• Hospitalization in an intensive care unit
• Level of consciousness on the FOUR scale ≤ 12 points
• Planned infusion therapy
• Presence of a central venous catheter or direct indication for catheterization
• The decision of the medical council to include the patient in the study

Exclusion Criteria:

• Pulmonary edema
• Absence of one or both lower extremities
• Chronic kidney disease according to KDIGO classification ≥ stage 3b
• Acute kidney injury grade 3
• Documented or suspected increased intracranial pressure (cerebral edema, brain compression, hydrocephalus, etc.).
• Presence of mitral valve regurgitation > grade 1
• Presence of aortic valve regurgitation > grade 1
• Patients previously enrolled in the "COMPASS" study in the period of 12 preceding hours