Conventional cardiovascular monitoring may not detect tissue hypoxia, and conventional cardiovascular support aiming at global hemodynamics may not restore tissue oxygenation. NIRS offers non-invasive online monitoring of tissue oxygenation in a wide range of clinical scenarios. NIRS monitoring is commonly used to measure cerebral oxygenation (rSO(2)), e.g. during cardiac surgery. In this review, we will show that tissue hypoxia occurs frequently in the perioperative setting, particularly in cardiac surgery. Therefore, measuring and obtaining adequate tissue oxygenation may prevent (postoperative) complications and may thus be cost-effective. NIRS monitoring may also be used to detect tissue hypoxia in (prehospital) emergency settings, where it has prognostic significance and enables monitoring of therapeutic interventions, particularly in patients with trauma. However, optimal therapeutic agents and strategies for augmenting tissue oxygenation have yet to be determined.

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Monitoring tissue oxygenation by near infrared spectroscopy (NIRS): background and current applications

Cerebral and tissue oximetry

Near-infrared spectroscopy (NIRS) has been used to measure regional tissue oxygen saturation (StO2) in skeletal muscle as an indicator of perfusion in trauma patients. In an effort to prospectively examine the usefulness of StO2 in identifying trauma patients in hemorrhagic shock, we evaluated the need for blood transfusion within 24 hours of injury as a marker of significant hemorrhage. A 6-month prospective, observational study was conducted at a university-affiliated, urban Level I trauma center using a convenience sample of 26 trauma patients thought to be at high risk for hemorrhagic shock. Baseline demographic data, vital signs, laboratory values, and amounts of fluid and blood products administered were collected. NIRS-derived StO2 values were measured for 1 hour after arrival to the trauma bay and the minimum value noted. A minimum StO2 less than 70 per cent correlated with the need for blood transfusion with a sensitivity of 88 per cent and a specificity of 78 per cent. The positive predictive value was 64 per cent and the negative predictive value was 93 per cent. The need for blood transfusion within 24 hours of arrival was not predicted by hypotension, tachycardia, arterial lactate, base deficit, or hemoglobin. StO2 may represent an important screening tool for identifying trauma patients who require blood transfusion or other limited medical resources.

Tissue oxygen saturation predicts the need for early blood transfusion in trauma patients.

ACADEMIC EMERGENCY MEDICINE 2010; 17:729–735 © 2010 by the Society for Academic Emergency Medicine



Abstract

Objectives:  Fatty acid–binding proteins (FABPs) have relatively high tissue concentrations and low plasma concentrations and are released into the circulation following organ injury. We explored the utility of intestinal-(I)-FABP and liver-(L)-FABP for the diagnosis of abdominal injury in patients with multiple trauma.



Methods:  This prospective study included 102 trauma patients and 30 healthy volunteers. Plasma I-FABP and L-FABP levels were measured in the emergency department (ED) by enzyme-linked immunosorbent assay (ELISA). Forty-one patients suffered from serious or severe abdominal trauma (Abbreviated Injury Score [AIS] code “ai” for abdominal injury, AISai ≥ 3) and nine were moderately abdominally injured (AISai < 3). Fifty-two had no abdominal injury.



Results:  Median I-FABP and L-FABP levels in the AISai ≥ 3 group (516 pg/mL and 135 ng/mL, respectively) were significantly higher compared to the AISai < 3 group (154 pg/mL and 13 ng/mL, respectively) or those without abdominal injury (207 pg/mL and 21 ng/mL, respectively) or normal controls (108 pg/mL and 13 ng/mL, respectively). The cutoff to distinguish the ai ≥ 3 is 359 pg/mL for I-FABP and 54 ng/mL for L-FABP, with 93% specificity and 75% sensitivity for I-FABP and 93% and 82% for L-FABP, respectively.



Conclusions:  High I-FABP and L-FABP levels correlate with relevant severity of abdominal tissue damage in patients with multiple trauma. I-FABP and L-FABP could be useful as markers for the early detection of significant abdominal injury in acute multiple trauma and identify patients who require rapid intervention.

Intestinal-FABP and liver-FABP: Novel markers for severe abdominal injury

BACKGROUND Phenylephrine and norepinephrine are two vasopressors commonly used to counteract anaesthesia-induced hypotension. Their dissimilar working mechanisms may differentially affect the macro and microcirculation, and ultimately tissue oxygenation. OBJECTIVES We investigated the differential effect of phenylephrine and norepinephrine on the heart rate (HR), stroke volume (SV), cardiac index (CI), cerebral tissue oxygenation (SctO(2)) and peripheral tissue oxygenation (SptO(2)), and rate-pressure product (RPP). DESIGN A randomised controlled study. SETTING Single-centre, University Medical Center Groningen, The Netherlands. PATIENTS Sixty normovolaemic patients under balanced propofol/remifentanil anaesthesia. INTERVENTIONS If the mean arterial pressure (MAP) dropped below 80% of the awake state value, phenylephrine (100 mu g + 0.5 mu g kg(-1) min(-1)) or norepinephrine (10 mu g + 0.05 mu g kg(-1) min(-1)) was administered in a randomised fashion. MAIN OUTCOME MEASURES MAP, HR, SV, CI, SctO(2), SptO(2) and rate-pressure product (RPP) analysed from 30 s before drug administration until 240 s thereafter. RESULTS Phenylephrine and norepinephrine caused an equivalent increase in MAP [Delta = 13 (8 to 22) and Delta = 13 (9 to 19) mmHg, respectively] and SV [Delta = 6 +/- 6 and Delta = 5 +/- 7 ml, respectively], combined with a significant equivalent decrease in HR (both Delta = -8 +/- 6 bpm), CI (both Delta = -0.2 +/- 0.3 l min(-1) m(-2)) and SctO(2) and an unchanged RPP (Delta = 345 +/- 876 and Delta = 537 +/- 1076 mmHg min(-1)). However, SptO(2) was slightly but statistically significantly (P <0.05) decreased after norepinephrine [Delta = -3 (-6 to 0)%] but not after phenylephrine administration [Delta = 0 (-1 to 1)%]. In both groups, SptO(2) after vasopressor was still higher than the awake value. CONCLUSION In normovolaemic patients under balanced propofol/remifentanil anaesthesia, phenylephrine and norepinephrine produced similar clinical effects when used to counteract anaesthesia-induced hypotension. After norepinephrine, a fall in peripheral tissue oxygenation was statistically significant, but its magnitude was not clinically relevant.

Differential effects of phenylephrine and norepinephrine on peripheral tissue oxygenation during general anaesthesia: A randomised controlled trial.

Alterations in regional tissue perfusion may precede global indications of shock. This study compared regional tissue oxygenation saturation (StO2) using near-infrared spectroscopy with standard he...

The correlation of near-infrared spectroscopy with changes in oxygen delivery in a controlled model of altered perfusion.

Mesenteric injuries after blunt abdominal trauma are infrequent and difficult to diagnose. We investigated whether a delay in diagnosis of more than 6 hours had a significant impact on morbidity, mortality, and length of stay at our Level I trauma center. A retrospective chart review spanning the period from January 1995 to September 2005 identified 85 patients with laparotomy-confirmed mesenteric injuries, 81 of whom survived to hospital discharge. Nineteen (23%) of the 81 patients had a delay in diagnosis of greater than 6 hours. After controlling for identified confounders, we found that the delayed diagnosis group experienced 30 per cent longer hospital stays (P = 0.03), 55 per cent longer intensive care unit stays (P = 0.006), and 38 per cent longer duration of mechanical ventilation (P = 0.05). Patients in the delayed group also had significantly higher odds of developing acute respiratory distress syndrome, as well as trends toward higher odds of wound infection, pneumonia, multiple organ dysfunction syndrome, abdominal compartment syndrome, renal failure, and ileus. No significant difference in mortality was observed among all 85 patients (P = 0.67). Thus, in contradiction to some previous studies, our review indicates that a delay in the diagnosis of mesenteric injuries results in significantly increased morbidity and hospital and intensive care unit lengths of stay.

Juliette Zelada

Papers

The correlation of near-infrared spectroscopy with changes in oxygen delivery in a controlled model of altered perfusion.

Mesenteric injuries after blunt abdominal trauma: delay in diagnosis and increased morbidity.