Case Series: A Description of the Pleth Variability Index in Patients with Septic Shock
Ray, Todd D.
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Pulse variability index (PVI) is a new functional hemodynamic measurement value that is noninvasive and has been shown to predict fluid responsiveness in critically ill patients. Few studies have examined the use of PVI in patients with severe sepsis or septic shock. This prospective case series described the pattern of PVI and continuous hemoglobin measurements during the initial resuscitation phase of newly diagnosed septic shock. PVI and PI were described in four patients with severe sepsis and/or septic shock (three men, age 52 ± 7; and one female, age 73). Therapies varied for each patient, including tidal volume, positive end expiratory pressure, vasopressor dose, and fluid boluses. Three patients received high dose norepinephrine. In these three patients norepinephrine influenced the PI, causing the PVI to increase but not because the patient was a fluid responder. In the patient not on high dose vasopressors the PVI increase did indicate fluid responsiveness.Three patients had a tidal volume less than 8 ml/kg; thus, the PVI may not adequately reflect if they will respond as these patients may not demonstrate as large a PVI due to the small changes in the intrathoracic pressure. This case series suggests that PVI does not assist in identifying fluid response status in patients receiving vasopressor therapy and tidal volumes less than 8 ml/kg. There were not enough data to evaluate agreement in SpHb and lab hemoglobin. One patient showed perfect agreement with laboratory Hgb and the other patient had a clinically significant difference. Continued studies with larger sample sizes are needed in populations of severe sepsis and septic shock to determine the utility of this technology to guide fluid resuscitation. The PVI and PI may be useful to determine hypoperfusion in septic shock patients, but further studies are needed.
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