Resolution and outcome of acute circulatory failure does not correlate with hemodynamics

The prognostic value of muscle regional oxygen saturation index in severe community-acquired pneumonia: a prospective observational study

Background

Community-acquired pneumonia (CAP) mortality exceeds 20 % in critical care patients despite appropriate antibiotic therapy. Regional tissue oxygen saturation index (rSO2) measured with near-infrared spectroscopy (NIRS) might facilitate early detection for patients at risk of serious complications. Our objectives were to determine the relationship between early determination of rSO2 and mortality and to compare discrimination power for mortality of rSO2 and other resuscitation variables in critically ill CAP patients.

Methods

This is a prospective observational study. Patients with CAP were enrolled within 6 h to intensive care admission. Demographics and clinical variables were recorded. rSO2 was determined using NIRS in brachioradialis muscle. All variables were determined at baseline and 24 h after admission.

Results

Forty patients were enrolled. Fourteen patients (35 %) had a baseline rSO2 < 60 % and 7 of them died (50 %). Only 1 of 26 (3.8 %) patients with rSO2 ≥ 60 % died (p = 0.007). The area under ROC curve (AUROC) showed consistent mortality discrimination at baseline (0.84, p = 0.03) and at 24 h (0.86, p = 0.006) for rSO2 values. Cox regression analysis showed that “low” rSO2 at ICU admission (hazard ratio (HR) = 8.99; 95 % confidence interval (CI) 1.05–76.8; p = 0.045) and “low” rSO2 at 24 h (HR = 13.18; 95 % CI 1.52–113.6; p = 0.019) were variables independently associated with mortality. In contrast, other variables such as Acute Physiology and Chronic Health Evaluation (APACHE II) score (HR = 1.09; 95 % CI 0.99–1.19; p = 0.052) were not associated with mortality.

Conclusions

Our findings suggest that forearm skeletal muscle rSO2 differs in patients with severe CAP according to outcome and might be an early prognosis tool.

Tissue ischemia microdialysis assessments following severe traumatic haemorrhagic shock: lactate/pyruvate ratio as a new resuscitation end point?

BACKGROUND

Intensive care of severe trauma patients focuses on the treatment of haemorrhagic shock. Tissues should be perfused sufficiently with blood and with sufficient oxygen content to ensure adequate tissue oxygen delivery. Tissue metabolism can be monitored by microdialysis, and the lactate/pyruvate ratio (LPR) may be used as a tissue ischemia marker. The aim of this study was to determine the adequate cardiac output and haemoglobin levels that avoid tissue ischemia.

METHODS

Adult patients with serious traumatic haemorrhagic shock were enrolled in this prospective observational study. The primary observed parameters included haemoglobin, cardiac output, central venous saturation, arterial lactate and the tissue lactate/pyruvate ratio.

RESULTS

Forty-eight patients were analysed. The average age of the patients was 39.8 ± 16.7, and the average ISS was 43.4 ± 12.2. Hb < 70 g/l was associated with pathologic arterial lactate, ScvO2 and LPR. Tissue ischemia (i.e., LPR over 25) developed when CI ≤ 3.2 l/min/m(2) and Hb between 70 and 90 g/l were observed. Severe tissue ischemia events were recorded when the Hb dropped below 70 g/l and CI was 3.2-4.8 l/min/m(2). CI ≥ 4.8 l/min/m(2) was not found to be connected with tissue ischemia, even when Hb ≤ 70 g/l.

CONCLUSION

LPR could be a useful marker to manage traumatic haemorrhagic shock therapies. In initial traumatic haemorrhagic shock treatments, it may be better to maintain CI ≥ 3.2 l/min/m(2) and Hb ≥ 70 g/l to avoid tissue ischemia. LPR could also be a useful transfusion trigger when it may demonstrate ischemia onset due to low local DO2 and early reveal low/no tissue perfusion.

Anaerobic metabolism associated with traumatic hemorrhagic shock monitored by microdialysis of muscle tissue is dependent on the levels of hemoglobin and central venous oxygen saturation: a prospective, observational study

Background

Traumatic hemorrhagic shock resulting in tissue hypoxia is a significant cause of morbidity and mortality in polytraumatized patients. Early identification of tissue hypoxia is possible with microdialysis. The aim of this study was to determine the correlation between a marker of tissue hypoxia (L/P; lactate to pyruvate ratio) and selected parameters of systemic oxygen delivery (Hb; hemoglobin) and oxygen extraction (ScvO₂; central venous oxygen saturation). We also investigated the severity of tissue hypoxia over the course of care.

Methods

Adult patients with traumatic hemorrhagic shock were enrolled in this prospective, observational study. Microdialysis of the peripheral muscle tissue was performed. Demographic data and timeline of care were collected. Tissue lactate, pyruvate, glycerol, glucose levels, hemoglobin, serum lactate and oxygen saturation of the central venous blood (ScvO₂) levels were also measured.

Results

The L/P ratio trend may react to changes in systemic hemoglobin levels with a delay of 7 to 10 hours, particularly when systemic hemoglobin levels are increased by transfusion. Decrease in tissue L/P ratio may react to increase in ScvO₂ with a delay of up to 10 hours, and such a decrease may signify elimination of tissue hypoxia after transfusion. We also observed changes in the L/P trend in the 13 hours preceding a change in the hemoglobin level. Fluid administration, which is routinely used as a first-line treatment of hypovolemic shock, can cause hemodilution and decreased hemoglobin. When ScvO₂ decreases, increase in L/P ratio may precede the ScvO₂ trend by 10 or 11 hours. An increase in the L/P ratio is an early warning sign of insufficient tissue oxygenation and should lead to intensive observation of hemoglobin levels, ScvO₂ and other hemodynamic parameters. Patients who were treated more rapidly had lower maximal L/P values and a lower degree of tissue ischemia.

Conclusion

The L/P ratio is useful to identify tissue ischemia and can estimate the effectiveness of fluid resuscitation. An increase in the L/P ratio is an early warning sign of inadequate tissue oxygenation and should lead to more detailed hemodynamic and laboratory monitoring. This information cannot usually be obtained from global markers.

Mortality and regional oxygen saturation index in septic shock patients: a pilot study

BACKGROUND

Peripheral muscle tissue oxygenation determined noninvasively using near-infrared spectroscopy may help to identify tissue hypoperfusion in septic patients. The aim of this study was to investigate regional oxygen saturation index (rSO2) in the brachioradialis (forearm) muscle by comparing measurements in healthy subjects and in intensive care unit (ICU) septic shock patients, and determine whether brachioradialis muscle rSO2 is associated with poor outcome in ICU septic shock patients.

METHODS

We conducted a prospective observational study in healthy volunteers (n = 50) and ICU septic shock patients (n=19). Brachioradialis (forearm) rSO2 measurements in healthy volunteers at rest and in ICU septic shock patients were compared. Pulmonary artery catheter monitoring was used in ICU patients.

RESULTS

Significant differences in rSO2 were observed between healthy volunteers and ICU septic shock patients at ICU admission (68.7±4.9 vs. 55.0±13.0; p<0.001). When comparing septic shock survivors and nonsurvivors, significant differences were observed in rSO2 at baseline (64.5±8.9 vs. 47.5±10.7; p<0.01), 12 hours (67.3±9.6 vs. 45.0±14.9; p<0.01), and 24 hours (65.7±7.0 vs. 50.1±10.3; p<0.01). Lactate concentration was lower in survivors than nonsurvivors at 24 hours (12.0±7.5 mmol/L vs. 23.2±12.5 mmol/L; p<0.04). Cardiac index was greater in nonsurvivors than survivors at baseline (4.6+1.9 L/min/m vs. 3.0+0.9 L/min/m; p<0.05) and 12 h (3.9+0.5 L/min/m vs. 3.1+0.3 L/min/m; p<0.05).

CONCLUSIONS

We observed that septic shock patients with forearm skeletal muscle rSO2≤60% throughout first 24 hours after ICU admission had significantly greater mortality rate than patients with forearm skeletal muscle rSO2>60% throughout this critical time.