Low StO2 measurements in surgical intensive care unit patients is associated with poor outcomes

Peripheral tissue oxygenation and the number of organs transplanted per donor

Current donor management practices target macrohaemodynamic parameters, but it is unclear if this leads to improvements in microvascular perfusion and tissue oxygenation; the latter may have more impact on organ status. In a recent preclinical study we determined that brain death impaired tissue perfusion and oxygen utilisation in swine while pharmacologic correction of these deficits improved organ function and reduced markers of tissue injury. As a first step in translating the preclinical findings, we conducted a prospective observational study to determine if there was an association between peripheral tissue oxygenation (measured by near-infrared spectroscopy) in deceased by neurological criteria human donors and the number of organs transplanted. In 60 donors, the mean time-weighted average of tissue oxygenation was 87.5% (standard deviation, SD, 5.2%) and the average number of organs transplanted was 3.5 (SD 2); there was a positive linear relationship between these two parameters. A 5% rise in tissue oxygenation was associated with an increase of 0.47 organs transplanted (95% confidence intervals 0.16 to 0.78) after adjusting for age (<i>P</i>=0.004). No such correlations were observed for the macrohaemodynamic or macro-oxygenation parameters (including arterial blood oxygenation). The results of this clinical trial are consistent with our preclinical work and support the postulate that targeting the microvasculature to improve tissue perfusion and tissue oxygen delivery in human donors has the potential to increase the quantity of organs suitable for transplant.

[Prognostic relevance of tissue oxygen saturation in patients in the early stage of multiple organ dysfunction syndrome]

BACKGROUND

Patients in circulatory shock exhibit insufficient peripheral perfusion to ensure adequate oxygenation of vital organs such as the heart and brain. Early detection of reduced tissue oxygen saturation (S_tO₂) could be used for rapid therapeutic intervention and thus improve the prognosis of patients in the early stage of multiple organ dysfunction syndrome (MODS).

MATERIALS AND METHODS

A total of 60 patients in the early stage of MODS (APACHE [Acute Physiology and Chronic Health Evaluation] II score ≥20) were investigated in a monocentric, prospective, randomized phase II study. S_tO₂ was measured using the InSpectraTM S_tO₂ system and compared with known indicators of hypoxia (peripheral oxygen saturation [S_pO₂], arterial oxygen saturation [S_aO₂], central venous oxygen saturation [S_cvO₂], pH, serum lactate). Clinical endpoints of the study were 28-day and 6‑month mortality as well as the need for invasive mechanical ventilation and renal replacement therapy during the hospital stay, respectively.

RESULTS

An increased 28-day and 6‑month mortality is found for patients with S_tO₂ <75% in contrast to patients with S_tO₂ ≥75%. Correlations of S_tO₂ with S_pO₂, S_cvO₂, and serum lactate are confirmed. Patients with reduced S_tO₂ tend to show a higher disease severity as measured by APACHE II score.

CONCLUSION

S_tO₂ shows prognostic relevance in patients at the early stage of MODS. Thus, the rapid and noninvasive assessment of S_tO₂ could be useful in risk stratification of these patients.

Preliminary Experience in Combined Somatic and Cerebral Oximetry Monitoring in Liver Transplantation

OBJECTIVE

The use of cerebral near-infrared spectroscopy (NIRS) has become widespread in cardiac surgery after research demonstrated an association between perioperative cerebral desaturations and postoperative complications. Somatic NIRS desaturation also is associated with an increased risk of postoperative complications and mortality. The objective of this study was to explore the trends of both somatic and cerebral NIRS during liver transplantation.

DESIGN

A prospective, single-site, observational case series.

SETTING

Tertiary care center.

PARTICIPANTS

The study comprised 10 patients undergoing liver transplantation.

INTERVENTIONS

NIRS sensors were placed on the forehead (cerebral regional oxygen saturation [rSO₂]) and on the right arm and right leg (somatic rSO₂) to measure tissue perfusion. Desaturation was defined as a 20% decrease of baseline values for 15 seconds.

MEASUREMENTS AND MAIN RESULTS

In all patients, parallel changes in both cerebral and somatic rSO₂ values were observed during phlebotomy, bleeding, transfusion, portal vein clamping, and the use of vasoactive agents. Induction of anesthesia increased cerebral rSO₂ more than it did somatic values. However, ascites removal, abdominal manipulation, and clamping of the inferior vena cava (IVC) were associated with nonparallel changes in cerebral and somatic rSO₂. Ascites removal was associated with increased somatic leg rSO₂, and IVC clamping and abdominal hypertension were associated with a significant reduction in somatic leg rSO₂. Somatic leg desaturation instead of arm or cerebral desaturation was associated with more postoperative complications.

CONCLUSIONS

The use of combined NIRS monitoring allows for the identification of the source of somatic or cerebral desaturation. Compromised venous flow from the IVC from clamping or abdominal compartment syndrome typically is associated with the appearance of more pronounced leg than arm desaturation.

Muscle Oxygenation as an Early Predictor of Shock Severity in Trauma Patients

INTRODUCTION

We evaluated the potential utility of a new prototype noninvasive muscle oxygenation (MOx) measurement for the identification of shock severity in a population of patients admitted to the trauma resuscitation rooms of a Level I regional trauma center. The goal of this project was to correlate MOx with shock severity as defined by standard measures of shock: systolic blood pressure, heart rate, and lactate.

METHODS

Optical spectra were collected from subjects by placement of a custom-designed optical probe over the first dorsal interosseous muscles on the back of the hand. Spectra were acquired from trauma patients as soon as possible upon admission to the trauma resuscitation room. Patients with any injury were eligible for study. MOx was determined from the collected optical spectra with a multiwavelength analysis that used both visible and near-infrared regions of light. Shock severity was determined in each patient by a scoring system based on combined degrees of hypotension, tachycardia, and lactate. MOx values of patients in each shock severity group (mild, moderate, and severe) were compared using two-sample t tests.

RESULTS

In 17 healthy control patients, the mean MOx value was 91.0 ± 5.5%. A total of 69 trauma patients were studied. Patients classified as having mild shock had a mean MOx of 62.5 ± 26.2% (n = 33), those classified as in moderate shock had a mean MOx of 56.9 ± 26.9% (n = 25) and those classified as in severe shock had a MOx of 31.0 ± 17.1% (n = 11). Mean MOx for each of these groups was statistically different from the healthy control group (P < 0.05).Receiver operating characteristic analyses show that MOx and shock index (heart rate/systolic blood pressure) identified shock similarly well (area under the curves [AUC] = 0.857 and 0.828, respectively). However, MOx identified mild shock better than shock index in the same group of patients (AUC = 0.782 and 0.671, respectively).

CONCLUSIONS

The results obtained from this pilot study indicate that MOx correlates with shock severity in a population of trauma patients. Noninvasive and continuous MOx holds promise to aid in patient triage and to evaluate patient condition throughout the course of resuscitation.

Near-infrared spectroscopy for assessing tissue oxygenation and microvascular reactivity in critically ill patients: a prospective observational study

Background

Impaired microcirculatory perfusion and tissue oxygenation during critical illness are associated with adverse outcome. The aim of this study was to detect alterations in tissue oxygenation or microvascular reactivity and their ability to predict outcome in critically ill patients using thenar near-infrared spectroscopy (NIRS) with a vascular occlusion test (VOT).

Methods

Prospective observational study in critically ill adults admitted to a 12-bed intensive care unit (ICU) of a University Hospital. NIRS with a VOT (using a 40 % tissue oxygen saturation (StO₂) target) was applied daily until discharge from the ICU or death. A group of healthy volunteers were evaluated in a single session. During occlusion, StO₂ downslope was measured separately for the first (downslope 1) and last part (downslope 2) of the desaturation curve. The difference between downslope 2 and 1 was calculated (delta-downslope). The upslope and area of the hyperaemic phase (receive operating characteristic (ROC) area under the curve (AUC) of StO₂) were calculated, reflecting microvascular reactivity. Outcomes were ICU and 90-day mortality.

Results

Patients (n = 89) had altered downslopes and upslopes compared to healthy volunteers (n = 27). Mean delta-downslope was higher in ICU non-survivors (2.8 (0.4, 3.8) %/minute versus 0.4 (−0.8, 1.8) in survivors, p = 0.004) and discriminated 90-day mortality (ROC AUC 0.72 (95 % confidence interval 0.59, 0.84)). ICU non-survivors had lower mean upslope (141 (75, 193) %/minute versus 185 (143, 217) in survivors, p = 0.016) and AUC StO₂ (7.9 (4.3, 12.6) versus 14.5 (11.2, 21.3), p = 0.001). Upslope and AUC StO₂ on admission were significant although weak predictors of 90-day mortality (ROC AUC = 0.68 (0.54, 0.82) and 0.70 (0.58, 0.82), respectively). AUC StO₂ ≤ 6.65 (1st quartile) on admission was independently associated with higher 90-day mortality (hazard ratio 7.964 (95 % CI 2.211, 28.686)). The lowest upslope in the ICU was independently associated with survival after ICU discharge (odds ratio 0.970 (95 % CI 0.945, 0.996)).

Conclusions

In critically ill patients, NIRS with a VOT enables identification of alterations in tissue oxygen extraction capacity and microvascular reactivity that can predict mortality.

Trial registration

NCT02649088, www.clinicaltrials.gov, date of registration 23rd December 2015, retrospectively registered.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1500-5) contains supplementary material, which is available to authorized users.

Rapid assessment of shock in a nonhuman primate model of uncontrolled hemorrhage: Association of traditional and nontraditional vital signs to mortality risk

BACKGROUND

Heart rate (HR), systolic blood pressure (SBP) and mean arterial pressure (MAP) are traditionally used to guide patient triage and resuscitation; however, they correlate poorly to shock severity. Therefore, improved acute diagnostic capabilities are needed. Here, we correlated acute alterations in tissue oxygen saturation (StO2) and end-tidal carbon dioxide (ETCO2) to mortality in a rhesus macaque model of uncontrolled hemorrhage.

METHODS

Uncontrolled hemorrhage was induced in anesthetized rhesus macaques by a laparoscopic 60% left-lobe hepatectomy (T = 0 minute). StO2, ETCO2, HR, as well as invasive SBP and MAP were continuously monitored through T = 480 minutes. At T = 120 minutes, bleeding was surgically controlled, and blood loss was quantified. Data analyses compared nonsurvivors (expired before T = 480 minutes, n = 5) with survivors (survived to T = 480 minutes, n = 11) using repeated-measures analysis of variance with Bonferroni correction. All p < 0.05 was considered statistically significant. Results were reported as mean ± SEM.

RESULTS

Baseline values were equivalent between groups for each parameter. In nonsurvivors versus survivors at T = 5 minutes, StO2 (55% ± 10% vs. 78% ± 3%, p = 0.02) and ETCO2 (15 ± 2 vs. 25 ± 2 mm Hg, p = 0.0005) were lower, while MAP (18 ± 1 vs. 23 ± 2 mm Hg, p = 0.2), SBP (26 ± 2 vs. 34 ± 3 mm Hg, p = 0.4), and HR (104 ± 13 vs. 105 ± 6 beats/min, p = 0.3) were similar. Association of values over T = 5-30 minutes to mortality demonstrated StO2 and ETCO2 equivalency with a significant group effect (p ≤ 0.009 for each parameter; R(2) = 0.92 and R(2) = 0.90, respectively). MAP and SBP associated with mortality later into the shock period (p < 0.04 for each parameter; R(2) = 0.91 and R(2) = 0.89, respectively), while HR yielded the lowest association (p = 0.8, R(2) = 0.83).

CONCLUSION

Acute alterations in StO2 and ETCO2 strongly associated with mortality and preceded those of traditional vital signs. The continuous, noninvasive aspects of Food and Drug Administration-approved StO2 and ETCO2 monitoring devices provide logistical benefits over other methodologies and thus warrant further investigation.

Effect of Prewarming during Induction of Anesthesia on Microvascular Reactivity in Patients Undergoing Off-Pump Coronary Artery Bypass Surgery: A Randomized Clinical Trial

Background

General anesthesia may induce inadvertent hypothermia and this may be related to perioperative cardiovascular complications. Microvascular reactivity, measured by the recovery slope during a vascular occlusion test, is decreased during surgery and is also related to postoperative clinical outcomes. We hypothesized that microvascular changes during surgery may be related to intraoperative hypothermia. To evaluate this, we conducted a randomized study in patients undergoing off-pump coronary artery bypass surgery, in which the effect of prewarming on microvascular reactivity was evaluated.

Methods

Patients scheduled for off-pump coronary artery bypass surgery were screened. Enrolled patients were randomized to the prewarming group to receive forced-air warming during induction of anesthesia or to the control group. Measurement of core and skin temperatures and vascular occlusion test were conducted before anesthesia induction, 1, 2, and 3 h after induction, and at the end of surgery.

Results

In total, 40 patients were enrolled and finished the study (n = 20 in the prewarming group and n = 20 in the control group). During the first 3 h of anesthesia, core temperature was higher in the prewarming group than the control group (p < 0.001). The number of patients developing hypothermia was lower in the prewarming group than the control group (4/20 vs. 13/20, p = 0.004). However, tissue oxygen saturation and changes in recovery slope following a vascular occlusion test at 3 h after anesthesia induction did not differ between the groups. There was no difference in clinical outcome, including perioperative transfusion, wound infection, or hospital stay, between the groups.

Conclusions

Prewarming during induction of anesthesia decreased intraoperative hypothermia, but did not reduce the deterioration in microvascular reactivity in patients undergoing off-pump coronary artery bypass surgery.

Trial Registration

ClinicalTrials.gov NCT02186210

Using Near Infrared Spectroscopy for Tissue Oxygenation Monitoring During Procedural Sedation: The Occurrence of Peripheral Tissue Oxygenation Changes With Respiratory Depression and Supportive Airway Measures

OBJECTIVES

The objective was to assess whether respiratory depression and supportive airway measures occurring during procedural sedation are associated with changes in peripheral tissue oxygen saturation (StO2 ).

METHODS

This was a prospective observational study of adult patients undergoing procedural sedation in the emergency department (ED). Patients undergoing sedation with propofol, 1:1 propofol and ketamine, and 4:1 propofol and ketamine were included. Clinical interventions, sedative medication doses, vital signs, end-tidal capnography (ETCO2 ), pulse oximetry (SpO2 ), and peripheral tissue oxygen saturation (StO2 ) were recorded. Respiratory depression was defined as the occurrence of a recorded SpO2  < 92%, an increase in ETCO2  > 10 mm Hg from baseline, or loss of capnography waveform. Supportive airway measures documented during the procedure included bag-valve mask ventilation, airway repositioning maneuvers, increase in supplemental oxygen, and stimulation to induce respiration. Relative changes in StO2 between baseline and nadir were compared among patients who met respiratory depression criteria or required a supportive airway measure and those who did not.

RESULTS

Ninety-three patients were enrolled. Thirty-two patients (34.4%) met criteria for respiratory depression, and 31 (33.3%) required intervention in the form of a supportive airway measure. The median percent change in StO2 from procedure baseline to nadir in patients meeting criteria for respiratory depression was 13.6%, compared to 4.2% in those who did not. The change in StO2 in patients who required a supportive airway measure was 12.5% versus 5.4% in those who did not.

CONCLUSIONS

Patients with respiratory depression and the use of supportive airway measures had greater changes in StO2 during procedural sedation than in patients who did not. Peripheral tissue oxygen saturation monitoring may be a useful tool for assessing respiratory adverse events in patients undergoing procedural sedation in the ED.

Association of low non-invasive near-infrared spectroscopic measurements during initial trauma resuscitation with future development of multiple organ dysfunction

BACKGROUND

Near-infrared spectroscopy (NIRS) non-invasively monitors muscle tissue oxygen saturation (StO2). It may provide a continuous noninvasive measurement to identify occult hypoperfusion, guide resuscitation, and predict the development of multiple organ dysfunction (MOD) after severe trauma. We evaluated the correlation between initial StO2 and the development of MOD in multi-trauma patients.

METHODS

Patients presenting to our urban, academic, Level I Trauma Center/Emergency Department and meeting standardized trauma-team activation criteria were enrolled in this prospective trial. NIRS monitoring was initiated immediately on arrival with collection of StO2 at the thenar eminence and continued up to 24 hours for those admitted to the Trauma Intensive Care Unit (TICU). Standardized resuscitation laboratory measures and clinical evaluation tools were collected. The primary outcome was the association between initial StO2 and the development of MOD within the first 24 hours based on a MOD score of 6 or greater. Descriptive statistical analyses were performed; numeric means, multivariate regression and rank sum comparisons were utilized. Clinicians were blinded from the StO2 values.

RESULTS

Over a 14 month period, 78 patients were enrolled. Mean age was 40.9 years (SD 18.2), 84.4% were male, 76.9% had a blunt trauma mechanism and mean injury severity score (ISS) was 18.5 (SD 12.9). Of the 78 patients, 26 (33.3%) developed MOD within the first 24 hours. The MOD patients had mean initial StO2 values of 53.3 (SD 10.3), significantly lower than those of non-MOD patients 61.1 (SD 10.0); P=0.002. The mean ISS among MOD patients was 29.9 (SD 11.5), significantly higher than that of non-MODS patients, 12.1 (SD 9.1) (P<0.0001). The mean shock index (SI) among MOD patients was 0.92 (SD 0.28), also significantly higher than that of non-MODS patients, 0.73 (SD 0.19) (P=0.0007). Lactate values were not significantly different between groups.

CONCLUSION

Non-invasive, continuous StO2 near-infrared spectroscopy values during initial trauma resuscitation correlate with the later development of multiple organ dysfunction in this patient population.

Soft tissue oxygenation and risk of mortality (STORM): an early marker of critical illness?

PURPOSE

Tissue oxygen saturation (StO2) is a noninvasive measure that reflects changes in tissue perfusion. Rapid response teams (RRTs) assess sick inpatients to determine need for intensive care unit (ICU) admission. This determination is subjective based on parameters such as systolic blood pressure, heart rate, and pulse oximetry. Our objective was to determine if parameters readily available at RRT bedside assessment (vital signs and StO2) can predict ICU admission and inhospital mortality.

MATERIALS AND METHODS

All inpatients assessed by RRT at a tertiary Canadian hospital were consecutively sampled for 3 months. After clinical assessment, the RRT physician (blinded to StO2) made the ultimate ICU admission decision.

RESULTS

In 134 included patients, mean age was 65.5 ± 15.2 years, and 53% (n = 71) were males. There were 49 ICU admissions (36.6%) and 31 mortalities (23.1%). Two multivariable models significantly predicted ICU admission and inhospital mortality. The only independent predictor of ICU admission was pulse oximetry (adjusted odds ratio, 0.88; 95% confidence interval, 0.80-0.96; P = .007). Tissue oxygen saturation did not predict ICU admission but was the only independent predictor of mortality (adjusted odds ratio, 1.06; 95% confidence interval, 1.01-1.12; P = .04).

CONCLUSIONS

Tissue oxygen saturation may identify critical illness in patients who would not traditionally meet ICU admission criteria and thus may identify patients who benefit from closer monitoring.