title: Pleth variability index is a weak predictor of fluid responsiveness in patients receiving norepinephrine.
abstract: BACKGROUND
  In patients receiving an infusion of norepinephrine, the relationship between the amplitude of the oximeter plethysmographic waveform and stroke volume may be variable and quality of the waveform might be reduced, compared with patients not receiving norepinephrine. We assessed the reliability of the pleth variability index (PVI), an automatic measurement of the respiratory variation of the plethysmographic waveform, for predicting fluid responsiveness in patients receiving norepinephrine infusions.
  
  
  METHODS
  We measured the response of cardiac index (transpulmonary thermodilution) to i.v. fluid administration in 42 critically ill patients receiving norepinephrine. Patients with arrhythmias, spontaneous breathing, tidal volume <8 ml kg(-1), and respiratory system compliance <30 ml cm H(2)O(-1) were excluded. Before fluid administration, we recorded the arterial pulse pressure variation (PPV) and pulse contour analysis-derived stroke volume variation (SVV, PiCCO2) and PVI (Masimo Radical-7).
  
  
  RESULTS
  In seven patients, the plethysmographic signal could not be obtained. Among the 35 remaining patients [mean SAPS II score=77 (sd=17)], i.v. fluid increased cardiac index ≥15% in 15 'responders'. A baseline PVI ≥16% predicted fluid responsiveness with a sensitivity of 47 (inter-quartile range=21-73)% and a specificity of 90 (68-99)%. The area under the receiver operating characteristic curve was significantly lower for PVI [0.68 (0.09)] than for PPV and SVV [0.93 (0.06) and 0.89 (0.07), respectively]. Considering all pairs of measurements, PVI was correlated with PPV (r(2)=0.27). The fluid-induced changes in PVI and PPV were not significantly correlated.
  
  
  CONCLUSIONS
  PVI was less reliable than PPV and SVV for predicting fluid responsiveness in critically ill patients receiving norepinephrine. In addition, PVI could not be measured in a significant proportion of patients. This suggests that PVI is not useful in patients receiving norepinephrine.
authors.affiliation: Hôpitaux universitaires Paris-Sud, Hôpital de Bicêtre, service de réanimation médicale, 78, rue du Général Leclerc, Le Kremlin-Bicêtre F-94270, France. xavier.monnet@bct.aphp.fr
authors.forename: X
authors.initials: X
authors.lastname: Monnet
authors.forename: L
authors.initials: L
authors.lastname: Guérin
authors.forename: M
authors.initials: M
authors.lastname: Jozwiak
authors.forename: A
authors.initials: A
authors.lastname: Bataille
authors.forename: F
authors.initials: F
authors.lastname: Julien
authors.forename: C
authors.initials: C
authors.lastname: Richard
authors.forename: J-L
authors.initials: JL
authors.lastname: Teboul
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D005440:Fluid Therapy; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009638:Norepinephrine / Q000627:therapeutic use*; D010991:Plethysmography / Q000706:statistics & numerical data*; D011237:Predictive Value of Tests; D011379:Prognosis; D012372:ROC Curve; D012129:Respiratory Function Tests; D012769:Shock / Q000175:diagnosis; D013318:Stroke Volume / Q000502:physiology; D013815:Thermodilution; D014662:Vasoconstrictor Agents / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D014662:Vasoconstrictor Agents; D009638:Norepinephrine