Objective: To determine the frequency and prognosis of the various causes of low systemic vascular resistance (SVR).

      Design:
      Analysis of consecutive patients over a 5-year period;
            retrospective review.


      Setting:
      Medical intensive care unit of a large university hospital.


      Patients:
      Fifty-five patients with unexplained hypotension and a SVR less
            than 800 dynes × s/cm5.


      Background:
      There are minimal data in the medical literature determining the
            frequency or outcome of patients with a low SVR that is unrelated to sepsis or
            the sepsis syndrome. We retrospectively reviewed and analyzed all hemodynamic
            data in a large university hospital over a 5-year period to determine the
            frequency and prognosis of the various causes of low SVR. Fifty-five patients
            with unexplained hypotension and a SVR less than
            800dynes×s/cm5were identified.


      Main results:
      Twenty-two patients (Groups 1 and 2) met the criteria for sepsis
            syndrome. The mean SVR for this group was 445 ±
            168 dynes×s/cm5 with an associated mortality of 50%. Group 3
            contained 20 patients with possible sepsis. Thirteen patients (Group 4) were
            nonseptic. The mean SVR of this group was 435 ±
            180 dynes × s/cm5 with an associated mortality of 46%. Extremely
            low SVR (below 450 dynes × s/cm5) was associated with a
            significantly higher mortality regardless of the etiology.


      Conclusions:
      At least a quarter of patients with hypotension and a low SVR have
            nonseptic etiologies. The patients with nonseptic etiologies have a similar
            mortality to septic patients. Clinicians should be aware of the wide spectrum
            of conditions that induce a low SVR.