Plasma Vasopressin and Norepinephrine Profiles Predict Outcome in Septic Patients with Impaired Compensatory Mechanisms

Objective: The objective of this study is to evaluate the role of plasma vasopressin/norepinephrine ratios in disclosing masked septic shock. Methods: A prospective sample of consecutive patients visiting the emergent department of a university teaching hospital and meeting the criteria of sepsis was enrolled. Besides sepsis work-up, we measured plasma vasopressin and norepinephrine concentrations and their ratios to detect the occurrence of septic shock in those with impaired compensatory mechanisms. Results: Of 284 patients with sepsis, forty-five aged from 45 to 92 years old met the inclusive criteria during a 12-month period (from January 2007 to December 2007). Three categories were classified as those with septic shock (n=12), those with severe sepsis (n=22) and those with only sepsis (n=11) according to 6-hour outcome. Plasma vasopressin and norepinephrine concentrations were measured. The plasma vasopressin level measured before the final outcome was significantly lower for those with septic shock (septic shock group, 3.8±0.9 pg/mL [95% CI 3.2-4.4 pg/mL]; severe sepsis group, 19.3±3.5 pg/mL [95% CI 17.5-20.8 pg/mL]; sepsis group 10.2±3.2 pg/mL [95% CI 8.2-12.2 pg/mL], P＜0.001) whereas the norepinephrine level highest for the same group (septic shock group, 3,490±410 pg/mL [95% CI 3,215-3,765 pg/mL]; severe sepsis group, 3,290±558 pg/mL [95% CI 3,043-3, 537 pg/mL]; and sepsis group, 1,854±427 pg/mL [95% CI 1,562-2,146 pg/mL]). At a cut-off value of 5 pg/mL, the sensitivity and specificity of plasma vasopressin in diagnosing septic shock are 100% (95% CI [71%-100%]) and 97 (95% CI [85%-99%])%, respectively. At a cut-off value of 2,750 pg/mL, the sensitivity and specificity of plasma norepinephrine in diagnosing septic shock are 100% (95% CI [71%-100%]) and 47% (95% CI [30%-65%]), respectively. The vasopressin/norepinephrine ratio had a sensitivity of 97% (95% CI [91%-100%]) and a specificity of 82% (95% CI [76%-88%]) at a cut-off value of vasopressin / norepinephrine of 1.0×10^(-3). Conclusions: Plasma vasopressin/norepinephrine profiles can provide accurate prediction of impending septic shock and outcome for the patients with impaired compensatory mechanisms.