Alterations in circulating vasoactive substances in the critically ill —a comparison between survivors and non-survivors

ObjectiveRegulation of circulatory homeostasis is based on several factors including various circulating vasoactive substances. Whether these regulators differ between survivors and non-survivors was investigated in critically ill patients.DesignProspective study.SettingClinical investigation on a surgical intensive care unit of an university hospital.Patients60 consecutive patients suffering from trauma (n=21) or postoperative complications (n=39) were studied prospectively. The patients were divided into survivors (n=27) and non-survivors (n=33). Therapy was adjusted to the standards of modern intensive care management by physicians who were not involved in the study.Measurements and resultsEndothelin-1, atrial natriuretic peptide (ANP), vasopressin, renin, and catecholamine (epinephrine, norepinephrine) plasma levels were measured from arterial blood samples using radioimmunoassay (RIA) or high-pressure liquid chromatography (HPLC) technique on the day of admission to ICU and during the following 5 days. Various hemodynamic parameters were also monitored during that period. The non-survivors showed elevated pulmonary artery pressure (PAP: 34.1±5.4 mmHg) and pulmonary capillary wedge pressure (PCWP: 20.3±7.3 mmHg) already at the beginning of the study. Cardiac index (CI) did not differ among the groups, whereas right ventricular ejection fraction (RVEF) decreased in the non-survivors. PaO2/FIO2 decreased only in the non-survivors, whereas VO2 increased in the survivors (from 246±48 to 331±43 ml/min). Plasma levels of renin (from 206±40 to 595±81 pg/ml) and vasopressin (from 5.78±0.82 to 7.97±0.69 pg/ml) increased significantly in the non-survivors. Epinephrine and norepinephrine plasma concentrations were elevated in the non-survivors already at baseline and tremendously increased in these patients during the following days. ANP plasma levels significantly increased also only in the non-survivors (from 188±63 to 339±55 pg/ml) (p<0.05). Endothelin-1 decreased in the survivors, whereas it significantly increased in the non-survivors (from 3.62±0.68 to 9.37±0.94 pg/ml) during the study period (p<0.05). Analyses of co-variance revealed overall no significant correlation between circulating vasoactive substances and hemodynamics.ConclusionsSystemic and regional regulators of the circulation were markedly changed by critical illness. In survivors, these regulators almost normalized within the study period of 5 days, whereas in non-survivors these alterations were even aggravated. It can only be speculated whether these regulator systems were influenced by activation of various mediator systems or whether they themselves influenced the negative outcome in the non-survivors.