The relationship of postocclusive reactive hyperemia assessed by the plethysmographic perfusion index to lactate clearance: a new piece in the unsolved puzzle of tissue perfusion and oxygenation in septic shock - Critical Care Science (CCS)

The relationship of postocclusive reactive hyperemia assessed by the plethysmographic perfusion index to lactate clearance: a new piece in the unsolved puzzle of tissue perfusion and oxygenation in septic shock |

Septic shock is commonly characterized by the lack of coherence between systemic hemodynamics and microcirculation.⁽⁾ The optimization of systemic cardiovascular variables frequently fails to improve the outcome of septic patients. Since the final goal of resuscitation should be the normalization of tissue perfusion and oxygenation, there is a growing interest in the monitoring of microvascular flow. Unfortunately, few tools for this goal are available in the clinical arena.

Alterations in cutaneous perfusion are typical manifestations of every type of shock. Although sophisticated methods might be used for the study of skin microcirculatory disorders, clinical evaluation is still a key approach.⁽⁾ The presence of mottling and its severity are strongly associated with mortality in patients with shock.⁽⁾ The capillary refill time is also a useful, inexpensive, and universally accessible method. It provides relevant prognostic information and can successfully guide the resuscitation of patients with septic shock.⁽⁾ The problem is that measurement of capillary refill time is poorly reproducible. Even after careful standardization and training, the interand intraobserver variability of the method is wide.⁽⁾ The capillary refill time changes according to the environmental temperature, age, sex, and skin characteristics.⁽⁾ Another valuable tool for the evaluation of cutaneous perfusion is the perfusion index (PI), which is derived from the analysis of the plethysmograph waveform of the pulse oximeter.⁽⁾ The PI is the ratio between the pulsatile component (arterial compartment) and the nonpulsatile component (venous and capillary blood) of the light reaching the detector of the pulse oximeter. Thus, the reduction in the pulsatile component by peripheral vasoconstriction decreases the ratio and thus the PI. In healthy volunteers, the values of PI have a highly skewed distribution, and they range from 0.3 to 10.0. Nevertheless, PI correlates with the core-to-toe temperature difference. In critically ill patients, a PI value below1.4 reflects the presence of poor peripheral perfusion.⁽⁾ Perfusion index can be used for the assessment of fluid responsiveness during a maneuver of passive leg raising.⁽⁾ Moreover, the dynamic response of the PI to a vascular occlusion test (VOT) allows the study of reactive hyperemia, which is the ability to recruit the microcirculation after an ischemic challenge.

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