Índice de perfusão periférica como ferramenta de detecção de choque oculto em pacientes críticos: um estudo observacional prospectivo

Abstract

The state of shock is a critical clinical syndrome resulting from the imbalance between oxygen delivery (DO2) and tissue metabolic demand (VO2), leading to tissue hypoxia and organ dysfunction. Changes in macro hemodynamics, such as tachycardia (HR > 100 bpm) and hypotension (MAP less than 65 mmHg), guide initial resuscitation. However, hemodynamic incoherence frequently occurs, characterized by the dissociation between macro and microcirculation. The persistence of tissue dysfunction even with compensated macro-hemodynamics characterizes occult shock. Laboratory markers of tissue hypoperfusion, such as lactate (greater than 2mmol/L) and central venous oxygen saturation (SVO2 less than 65%), are the gold standard for diagnosis. The assessment of peripheral perfusion, which reflects microcirculation, is essential for suspecting and detecting this hemodynamic incoherence. Traditionally, clinical variables such as capillary refill time (CRT) and mottling score (MS) have been used, which, although accessible, are intermittent and subjective. In contrast, the perfusion index (PI), obtained continuously by pulse oximetry through the ratio between the pulsatile and non-pulsatile portions of the plethysmographic signal, emerges as a promising tool for objective, real-time monitoring. The performance of the perfusion index was compared to other clinical perfusion variables in detecting occult shock. A prospective observational study was conducted in the general ICU of HUCFF/UFRJ. Adult patients admitted for clinical or surgical causes, with a compensated hemodynamic status, were included. Demographic data, macro and micro-hemodynamic variables, and paired central venous and arterial blood gas analyses were collected. The diagnosis of occult shock was defined by the presence of SVO2 less than 65 percent and/or arterial lactate greater than two mmol/L in blood gas samples, associated with compensated hemodynamics (MAP greater than 65 mmHg and HR less than 100 bpm). The AUC-ROC determined the shock detection capacity for the perfusion variables: capillary refill time (CRT), mottling score (MS), and perfusion index (PI). Fifty measurements were performed, of which 9 were excluded, and 41 were analyzed. Measurements involved 20 patients, 11 females, with a mean age of 59 years (52-69), SOFA score of 5.66 (2-9), SAPS3 score of 65.29 (57-72), and a time to ICU admission of 6.59 days (6-9). Norepinephrine was present in 17 measurements, with a mean MAP of 86 (74-96) mmHg and HR of 91 (85-99) bpm. Occult shock was detected in 22 (53 percent) measurements, associated with lower PI (median 1.48, range 0.12 to 2.84) versus (median 2.56, range 0.78 to 4.34), with p equals 0.03, and higher CRT (median 3.5 seconds, range 1.59 to 5.59) versus (median 2.42 seconds, range 0.85 to 3.99), with p equals 0.04, and higher MS (p greater than 0.05). The AUC for occult shock detection was higher for PI (0.70) compared to the other clinical perfusion variables (CRT 0.69, and MS 0.58). PI values less than or equal to 1.63 showed a sensitivity of 70%, specificity of 79%, and accuracy of 74%. Compared to traditional clinical perfusion variables, such as capillary refill time and mottling score, the perfusion index demonstrated slightly superior performance in the detection of occult shock in critically ill patients in the analyzed sample.