Predictive Role of Central Venous Oxygen Saturation in Patients With Acute Type I Respiratory Failure

Background :Tissue hypoperfusion is reflected by metabolic parameters suchas lactate, and central venous oxygen saturation . The objective of the present study was to estimate the value of SvO2 to predict outcome in patients with type 1 ARF admitted to ICU and to assess its potential association with mortality.
METHODS: Sixty-two patients with acute type 1 respiratory failure admitted to respiratory ICU with a clinical indication for a central venous catheter were included in the study. ScvO2 was assessed at ICU arrival and 3rd day and 7th day from the central venous blood samples from the right atrium, also arterial blood gas was measured simultaneously at the enrollment. ScvO2 levels were stratified into 3groups as follows: a low ScvO2 <65% in19 patients; normal SCVO2 (65% to 75%) in 34 patients; and highSCVO2 more than 75% in 9 patients. Moreover, the critical value of SCVO2was defined as the best cutoff value related to the mortality in the study population. LOSICU and LOS hospital, severity of APACHE II score and 7-day mortality were recorded.
RESULTS: Of the 62 patients (32 (51.61%) males) with type 1 ARF, aged (60.02
17.44) years were included. 49 (79%) patients had pneumonia & 34 (54.8%) had septic shock. 48 patients (77.4%) were ventilated (6
3.6 days). The duration of hospitalization was 6.8
4 days and hospital mortality 72.6%. ScvO2 was 67.7
8.1 at admission, 66
11 3rd day and 69.3
9.3 7th day later. Svo2 significantly increased over time with a greater [ in survivors than non survivors (7.2, 5.3, vs -1.7, -3.P < 0.001 & 0.005). The Overall mortality was 17 (37.8%) in Group 1, 20 (44.4%) in Group 2, and 8 (17.8%) in Group 3. Abnormal ScvO2 (low and high) was strongly associated with higher mortality [p < 0.0001]. Regarding ScvO2 on admission, the cutoff point for predicting mortality was #65%. It has a P value = 0.0008, sensitivity 49, specificity 100, PPV 100 and NPV 42.5. APACHE II score >27,septic shock, M.ventilation , ARDS, initial low PO2 & SaO2, the cutoff point of ScvO2 #65% at day 0, #70% at day3, at day 7 #66% & Male were strongly associated with higher mortality(0.0003, 0.0001, 0.0001, 0.006, 0.03, 0.01, 0.0008, 0.04, 0.04) &0.03, respectively).

CONCLUSIONS: Oxygenation category, as represented by initial ScvO2 , was significantly associated with 7-day mortality in patients with ARF. Abnormal ScvO2 (Low and highScvO2) Initially, in the 3rd day, & 7th day later, percentage of changes in ScvO2 in day 3, 7, and high APACHE II are significantly associated with increased mortality in patients with type 1 ARF.
CLINICAL IMPLICATIONS: ScvO2 was valuable in assessing tissue oxygination in critically ill patients and may be substituted for the need of SvO2.