Monitoring trauma and intensive care unit resuscitation with tissue hemoglobin oxygen saturation

Early Fluid Is Less Fluid: Comparing Early Versus Late ICU Resuscitation in Severely Injured Trauma Patients

OBJECTIVES

The temporal trends of crystalloid resuscitation in severely injured trauma patients after ICU admission are not well characterized. We hypothesized early crystalloid resuscitation was associated with less volume and better outcomes than delaying crystalloid.

DESIGN

Retrospective, observational.

SETTING

High-volume level 1 academic trauma center.

PATIENTS

Adult trauma patients admitted to the ICU with emergency department serum lactate greater than or equal to 4 mmol/dL, elevated lactate (≥ 2 mmol/L) at ICU admission, and normal lactate by 48 hours.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For the 333 subjects, we analyzed patient and injury characteristics and the first 48 hours of ICU course. Receipt of greater than or equal to 500 mL/hr of crystalloid in the first 6 hours of ICU admission was used to distinguish early vs. late resuscitation. Outcomes included ICU length of stay (LOS), ventilator days, and acute kidney injury (AKI). Unadjusted and multivariable regression methods were used to compare early resuscitation vs. late resuscitation. Compared with the early resuscitation group, the late resuscitation group received more volume by 48 hours (5.5 vs. 4.1 L; p ≤ 0.001), had longer ICU LOS (9 vs. 5 d; p ≤ 0.001), more ventilator days (5 vs. 2 d; p ≤ 0.001), and higher occurrence rate of AKI (38% vs. 11%; p ≤ 0.001). On multivariable regression, late resuscitation remained associated with longer ICU LOS and ventilator days and higher odds of AKI.

CONCLUSIONS

Delaying resuscitation is associated with both higher volumes of crystalloid by 48 hours and worse outcomes compared with early resuscitation. Judicious crystalloid given early in ICU admission could improve outcomes in the severely injured.

Validation of a Novel Noninvasive Technology to Estimate Blood Oxygen Saturation Using Green Light: Observational Study

BACKGROUND

Pulse oximeters work within the red-infrared wavelengths. Therefore, these oximeters produce erratic results in dark-skinned subjects and in subjects with cold extremities. Pulse oximetry is routinely performed in patients with fever; however, an elevation in body temperature decreases the affinity of hemoglobin for oxygen, causing a drop in oxygen saturation or oxyhemoglobin concentrations.

OBJECTIVE

We aimed to determine whether our new investigational device, the Shani device or SH1 (US Patent 11191460), detects a drop in oxygen saturation or a decrease in oxyhemoglobin concentrations.

METHODS

An observational study (phase 1) was performed in two separate groups to validate measurements of hemoglobin and oxygen concentrations, including 39 participants recruited among current university students and staff aged 20-40 years. All volunteers completed baseline readings using the SH1 device and the commercially available Food and Drug Administration-approved pulse oximeter Masimo. SH1 uses two light-emitting diodes in which the emitted wavelengths match with absorption peaks of oxyhemoglobin (hemoglobin combined with oxygen) and deoxyhemoglobin (hemoglobin without oxygen or reduced hemoglobin). Total hemoglobin was calculated as the sum of oxyhemoglobin and deoxyhemoglobin. Subsequently, 16 subjects completed the "heat jacket study" and the others completed the "blood donation study." Masimo was consistently used on the finger for comparison. The melanin level was accounted for using the von Luschan skin color scale (VLS) and a specifically designed algorithm. We here focus on the results of the heat jacket study, in which the subject wore a double-layered heated jacket and pair of trousers including a network of polythene tubules along with an inlet and outlet. Warm water was circulated to increase the body temperature by 0.5-0.8 °C above the baseline body temperature. We expected a slight drop in oxyhemoglobin concentrations in the heating phase at the tissue level.

RESULTS

The mean age of the participants was 24.1 (SD 0.8) years. The skin tone varied from 12 to 36 on the VLS, representing a uniform distribution with one-third of the participants having fair skin, brown skin, and dark skin, respectively. Using a specific algorithm and software, the reflection ratio for oxyhemoglobin was displayed on the screen of the device along with direct hemoglobin values. The SH1 device picked up more minor changes in oxyhemoglobin levels after a change in body temperature compared to the pulse oximeter, with a maximum drop in oxyhemoglobin concentration detected of 6.5% and 2.54%, respectively.

CONCLUSIONS

Our new investigational device SH1 measures oxygen saturation at the tissue level by reflectance spectroscopy using green wavelengths. This device fared well regardless of skin color. This device can thus eliminate racial disparity in these key biomarker assessments. Moreover, since the light is shone on the wrist, SH1 can be readily miniaturized into a wearable device.

Near-Infrared Spectroscopy for the In Vivo Monitoring of Biodegradable Implants in Rats

Magnesium (Mg) alloys possess unique properties that make them ideal for use as biodegradable implants in clinical applications. However, reports on the in vivo assessment of these alloys are insufficient. Thus, monitoring the degradation of Mg and its alloys in vivo is challenging due to the dynamic process of implant degradation and tissue regeneration. Most current works focus on structural remodeling, but functional assessment is crucial in providing information about physiological changes in tissues, which can be used as an early indicator of healing. Here, we report continuous wave near-infrared spectroscopy (CW NIRS), a non-invasive technique that is potentially helpful in assessing the implant-tissue dynamic interface in a rodent model. The purpose of this study was to investigate the effects on hemoglobin changes and tissue oxygen saturation (StO₂) after the implantation of Mg-alloy (WE43) and titanium (Ti) implants in rats' femurs using a multiwavelength optical probe. Additionally, the effect of changes in the skin on these parameters was evaluated. Lastly, combining NIRS with photoacoustic (PA) imaging provides a more reliable assessment of tissue parameters, which is further correlated with principal component analysis.

Mismatch between Tissue Partial Oxygen Pressure and Near-Infrared Spectroscopy Neuromonitoring of Tissue Respiration in Acute Brain Trauma: The Rationale for Implementing a Multimodal Monitoring Strategy

The brain tissue partial oxygen pressure (PbtO₂) and near-infrared spectroscopy (NIRS) neuromonitoring are frequently compared in the management of acute moderate and severe traumatic brain injury patients; however, the relationship between their respective output parameters flows from the complex pathogenesis of tissue respiration after brain trauma. NIRS neuromonitoring overcomes certain limitations related to the heterogeneity of the pathology across the brain that cannot be adequately addressed by local-sample invasive neuromonitoring (e.g., PbtO₂ neuromonitoring, microdialysis), and it allows clinicians to assess parameters that cannot otherwise be scanned. The anatomical co-registration of an NIRS signal with axial imaging (e.g., computerized tomography scan) enhances the optical signal, which can be changed by the anatomy of the lesions and the significance of the radiological assessment. These arguments led us to conclude that rather than aiming to substitute PbtO₂ with tissue saturation, multiple types of NIRS should be included via multimodal systemic- and neuro-monitoring, whose values then are incorporated into biosignatures linked to patient status and prognosis. Discussion on the abnormalities in tissue respiration due to brain trauma and how they affect the PbtO₂ and NIRS neuromonitoring is given.

Improved haemodynamic stability and cerebral tissue oxygenation after induction of anaesthesia with sufentanil compared to remifentanil: a randomised controlled trial

BACKGROUND

Balanced anaesthesia with propofol and remifentanil, compared to sufentanil, often decreases mean arterial pressure (MAP), heart rate (HR) and cardiac index (CI), raising concerns on tissue-oxygenation. This distinct haemodynamic suppression might be attenuated by atropine. This double blinded RCT, investigates if induction with propofol-sufentanil results in higher CI and tissue-oxygenation than with propofol-remifentanil and if atropine has more pronounced beneficial effects on CI and tissue-oxygenation in a remifentanil-based anaesthesia.

METHODS

In seventy patients scheduled for coronary bypass grafting (CABG), anaesthesia was induced and maintained with propofol target controlled infusion (TCI) with a target effect-site concentration (Cet) of 2.0 μg ml- 1 and either sufentanil (TCI Cet 0.48 ng ml- 1) or remifentanil (TCI Cet 8 ng ml- 1). If HR dropped below 60 bpm, methylatropine (1 mg) was administered intravenously. Relative changes (∆) in MAP, HR, stroke volume (SV), CI and cerebral (SctO2) and peripheral (SptO2) tissue-oxygenation during induction of anaesthesia and after atropine administration were analysed.

RESULTS

The sufentanil group compared to the remifentanil group showed significantly less decrease in MAP (∆ = - 23 ± 13 vs. -36 ± 13 mmHg), HR (∆ = - 5 ± 7 vs. -10 ± 10 bpm), SV (∆ = - 23 ± 18 vs. -35 ± 19 ml) and CI (∆ = - 0.8 (- 1.5 to - 0.5) vs. -1.5 (- 2.0 to - 1.1) l min- 1 m- 2), while SctO2 (∆ = 9 ± 5 vs. 6 ± 4%) showed more increase with no difference in ∆SptO2 (∆ = 8 ± 7 vs. 8 ± 8%). Atropine caused higher ∆HR (13 (9 to 19) vs. 10 ± 6 bpm) and ∆CI (0.4 ± 0.4 vs. 0.2 ± 0.3 l min- 1 m- 2) in sufentanil vs. remifentanil-based anaesthesia, with no difference in ∆MAP, ∆SV and ∆SctO2 and ∆SptO2.

CONCLUSION

Induction of anaesthesia with propofol and sufentanil results in improved haemodynamic stability and higher SctO2 compared to propofol and remifentanil in patients having CABG. Administration of atropine might be useful to counteract or prevent the haemodynamic suppression associated with these opioids.

TRIAL REGISTRATION

Clinicaltrials.gov on June 7, 2013 (trial ID: NCT01871935 ).

Handheld Tissue Oximetry for the Prehospital Detection of Shock and Need for Lifesaving Interventions: Technology in Search of an Indication?

Improved prehospital methods for assessing the need for lifesaving interventions (LSIs) are needed to gain critical lead time in the care of the injured. We hypothesized that threshold values using prehospital handheld tissue oximetry would detect occult shock and predict LSI requirements. This was a prospective observational study of adult trauma patients emergently transported by helicopter. Patients were monitored with a handheld tissue oximeter (InSpectra Spot Check; Hutchinson Technology Inc, Hutchinson, MN), continuous vital signs, and 21 laboratory measurements obtained both in the field with a portable analyzer and at the time of admission. Shock was defined as base excess ≥ 4 or lactate > 3 mmol/L. Eighty-eight patients were enrolled with a median Injury Severity Score of 16 (interquartile range, 5-29). The median hemoglobin saturation in the capillaries, venules, and arterioles (StO₂) value for all patients was 82% (interquartile range, 76%-87%; range, 42%-98%). StO₂ was abnormal (< 75%) in 18 patients (20%). Eight were hypotensive (9%) and had laboratory-confirmed evidence of occult shock. StO₂ correlated poorly with shock threshold laboratory values (r = -0.17; 95% confidence interval, -0.33 to 1.0; P = .94). The area under the receiver operating curve was 0.51 (95% confidence interval, 0.39-0.63) for StO₂ < 75% and laboratory-confirmed shock. StO₂ was not associated with LSI need on admission when adjusted for multiple covariates, nor was it independently associated with death. Handheld tissue oximetry was not sensitive or specific for identifying patients with prehospital occult shock. These results do not support prehospital StO₂ monitoring despite its inclusion in several published guidelines.

Recent advances in bedside microcirculation assessment in critically ill patients

Parameters related to macrocirculation, such as the mean arterial pressure, central venous pressure, cardiac output, mixed venous saturation and central oxygen saturation, are commonly used in the hemodynamic assessment of critically ill patients. However, several studies have shown that there is a dissociation between these parameters and the state of microcirculation in this group of patients. Techniques that allow direct viewing of the microcirculation are not completely disseminated, nor are they incorporated into the clinical management of patients in shock. The numerous techniques developed for microcirculation assessment include clinical assessment (e.g., peripheral perfusion index and temperature gradient), laser Doppler flowmetry, tissue oxygen assessment electrodes, videomicroscopy (orthogonal polarization spectral imaging, sidestream dark field imaging or incident dark field illumination) and near infrared spectroscopy. In the near future, the monitoring and optimization of tissue perfusion by direct viewing and microcirculation assessment may become a goal to be achieved in the hemodynamic resuscitation of critically ill patients.

Assessment of hand superficial oxygenation during ischemia/reperfusion in healthy subjects versus systemic sclerosis patients by 2D near infrared spectroscopic imaging

BACKGROUND AND OBJECTIVE

Patients affected by systemic sclerosis (SSc) develop functional and structural microcirculatory dysfunction, which progressively evolves towards systemic tissue fibrosis (sclerosis). Disease initially affects distal extremities, which become preferential sites of diagnostic scrutiny. This pilot investigation tested the hypothesis that peripheral microcirculatory dysfunction in SSc could be non-invasively assessed by 2D Near Infrared Spectroscopic (NIRS) imaging of the hand associated with Vascular Occlusion Testing (VOT). NIRS allows measurement of hemoglobin oxygen saturation (StO₂) in the blood perfusing the volume tissue under scrutiny.

METHODS

In five normal volunteers and five SSc patients we applied a multispectral oximetry imaging device (Kent camera, Kent Imaging, Calgary, Canada) to acquire StO₂ 2D maps of the whole hand palm during baseline, ischemia and reperfusion phase.

RESULTS

We found significant differences between controls and SSc patients in basal StO₂ (82.80 ± 2.51 vs 65.44 ± 7.96%, p = 0.0016), minimum StO₂ (59.35 ± 4.29 vs 40.73 ± 6.47%, p = 0.0007), final StO₂ (83.83 ± 4.09 vs 68.84 ± 11.41%, p = 0.02) and time to maximum StO₂ (40 ± 12.25 vs 62 ± 4.47 s, p = 0.005).

CONCLUSIONS

This is, to our knowledge, the first application of 2D NIRS imaging of the whole hand to the investigation of microvascular dysfunction in systemic sclerosis. The image processing presented here considered the StO₂ in the entire hand allowing a comprehensive view of the spatial heterogeneity of microvascular dysfunction.

Tissue Oxygenation Monitoring as a Guide for Trauma Resuscitation

Hypoperfusion is the most common event preceding the onset of multiple organ dysfunction syndrome during trauma resuscitation. Detecting subtle changes in perfusion is crucial to ensure adequate tissue oxygenation and perfusion. Traditional methods of detecting physiological changes include measurements of blood pressure, heart rate, urine output, serum levels of lactate, mixed venous oxygen saturation, and central venous oxygen saturation. Continuous noninvasive monitoring of tissue oxygen saturation in muscle has the potential to indicate severity of shock, detect occult hypoperfusion, guide resuscitation, and be predictive of the need for interventions to prevent multiple organ dysfunction syndrome. Tissue oxygen saturation is being used in emergency departments, trauma rooms, operating rooms, and emergency medical services. Tissue oxygen saturation technology is just as effective as mixed venous oxygen saturation, central venous oxygen saturation, serum lactate, and Stewart approach with strong ion gap, yet tissue oxygen saturation assessment is also a direct, noninvasive microcirculatory measurement of oxygen saturation.

Monitoring End Points of Burn Resuscitation

This article discusses commonly used methods of monitoring and determining the end points of resuscitation. Each end point of resuscitation is examined as it relates to use in critically ill burn patients. Published medical literature, clinical trials, consensus trials, and expert opinion regarding end points of resuscitation were gathered and reviewed. Specific goals were a detailed examination of each method in the critical care population and how this methodology can be used in the burn patient. Although burn resuscitation is monitored and administered using the methodology as seen in medical/surgical intensive care settings, special consideration for excessive edema formation, metabolic derangements, and frequent operative interventions must be considered.

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.

A systematic review of human and veterinary applications of noninvasive tissue oxygen monitoring

OBJECTIVE

To describe the methodology for and utilization of tissue oxygen monitoring by near infrared spectroscopy, and to review the current literature on the use of this monitoring modality in human and veterinary settings.

DATA SOURCES

Scientific reviews and original research found using the PubMed and CAB Abstract search engines with the following keywords: "tissue oxygen monitoring," "near-infrared tissue spectroscopy," and "tissue oxygen saturation (StO2 )."

HUMAN DATA SYNTHESIS

Tissue oxygen monitors have been evaluated in a wide variety of human clinical applications including trauma and triage, surgery, sepsis, and septic shock, and early goal-directed therapy. StO2 more rapidly identifies occult shock in human patients compared to traditional methods, which can lead to earlier intervention in these patients.

VETERINARY DATA SYNTHESIS

Veterinary studies involving tissue oxygen monitoring are limited, but the technology may have utility for identification of hemorrhagic shock earlier than changes in base excess, blood lactate concentration, or other traditional perfusion parameters.

CONCLUSION

Tissue oxygen monitoring is most commonly performed utilizing a noninvasive, portable monitor, which provides real-time, continuous, repeatable StO2 measurements. A decline in StO2 is an early indicator of shock in both human and veterinary patients. Low StO2 values in human patients are associated with increased morbidity, mortality, and length of hospitalization, as well as the development of multiple organ system dysfunction and surgical site infections.

Low tissue oxygen saturation is associated with requirements for transfusion in the rural trauma population

BACKGROUND

Tissue O2 saturation (StO2) is a measure of tissue perfusion and should decrease during active hemorrhage. An initial StO2 value upon trauma center arrival measured concurrently with or prior to vitals, may predict hemorrhagic shock, requiring early blood product transfusion. Our aim was to identify the early StO2 threshold associated with a greater volume of packed red blood cell (PRBC) transfusion 24 h after injury.

METHODS

All highest tier triage trauma patients from January 2011 to July 2012 were included in this study. The initial StO2 value upon arrival was used for comparison.

RESULTS

A total of 632 patients were considered, 74% of them male with a mean age of 46 years. Initial StO2 values were available for 325 patients. An StO2 value of 65% was determined as the cutoff due to the marked increase in PRBC consumption in 24 h. There were 23 patients (7%) with an StO2 reading <65% compared to 302 patients with values ≥65%. Both groups had similar systolic blood pressure (118 vs. 126) and heart rate (99 vs. 95) in the trauma bay. In addition, there was no difference in the initial hemoglobin, pH, or base deficit. An early StO2 value <65% also led to a greater number of PRBC transfused in 24 h (6.4 vs. 1.7). Regression analysis demonstrated that an StO2 <65% was the only variable associated with a higher PRBC transfusion volume in 24 h (p = 0.01).

CONCLUSIONS

An StO2 value <65% correlates with greater requirement for PRBC transfusion 24 h after injury. This suggests that StO2 can be used as an early marker of hemorrhage which may be superior to traditional vital signs in the trauma population.

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.

Examination of tissue oxygen saturation (StO2) changes associated with vascular pedicle occlusion in a rat Island flap model using near-Infrared spectroscopy

PURPOSE

The purpose of this study was to perform continuous StO(2) monitoring of rat island flaps during pedicle vessel occlusion using near-infrared spectroscopy (NIRS) in order to collect experimental data for StO(2) flap monitoring under optimized conditions.

MATERIALS AND METHODS

Twenty rats were used in this study. The 3 × 3 cm(2) epigastric skin island flaps were elevated on either side. The animals were randomly assigned to two groups; an arterial occlusion group (n = 10) and a venous occlusion group (n = 10). The StO(2) values of the flaps were observed for over 30 min for the pedicle artery or venous occlusion, followed by an additional 30 min release.

RESULTS

The baseline StO(2) value was 78.4% ± 3.2% in the arterial occlusion group, compared to 78.5% ± 5.8% in the venous occlusion group, with no significant differences (P > 0.05). The StO(2) values decreased immediately after arterial occlusion, whereas a temporal StO(2) increase was initially observed after venous occlusion, followed by a StO(2) decrease. The StO(2) values decreased 27.3% ± 7.1% after arterial occlusion and 28.4% ± 19.1% after venous occlusion at 30 min after pedicle vessel clamping (P > 0.05). The StO(2) values were 0.4% ± 5.8% lower than baseline 30 min after arterial release (P > 0.05), while 18.9% ± 11.3% lower than baseline 30 min after venous release (P < 0.01).

CONCLUSION

NIRS can be used to indicate StO(2) changes in flaps with the pedicle vessel occlusion and differentiate between pedicle artery and vein occlusion. Further investigations are needed to obtain definitive evidence associated with predicting the degree of flap viability and determine the practical use of this technique.

Endpoints of resuscitation

Despite the multiple causes of the shock state, all causes possess the common abnormality of oxygen supply not meeting tissue metabolic demands. Compensatory mechanisms may mask the severity of hypoxemia and hypoperfusion, since catecholamines and extracellular fluid shifts initially compensate for the physiologic derangements associated with patients in shock. Despite the achievement of normal physiologic parameters after resuscitation, significant metabolic acidosis may continue to be present in the tissues, as evidenced by increased lactate levels and metabolic acidosis. This review discusses the major endpoints of resuscitation in clinical use.

Non invasive monitoring in mechanically ventilated pediatric patients

Cardiopulmonary monitoring is a key component in the evaluation and management of critically ill patients. Clinicians typically rely on a combination of invasive and non-invasive monitoring to assess cardiac output and adequacy of ventilation. Recent technological advances have led to the introduction: of continuous non-invasive monitors that allow for data to be obtained at the bedside of critically ill patients. These advances help to identify hemodynamic changes and allow for interventions before complications occur. In this manuscript, we highlight several important methods of non-invasive cardiopulmonary monitoring, including capnography, transcutaneous monitoring, pulse oximetry, and near infrared spectroscopy.

Bedside assessment of tissue oxygen saturation monitoring in critically ill adults: an integrative review of the literature

Objective. Tissue oxygen saturation (StO2) monitoring is a noninvasive technology with the purpose of alerting the clinician of peripheral hypoperfusion and the onset of tissue hypoxia. This integrative review examines the rigor and quality of studies focusing on StO2 monitoring in adult critically ill patients. Background. Clinicians must rapidly assess adverse changes in tissue perfusion while minimizing potential complications associated with invasive monitoring. The noninvasive measurement of tissue oxygen saturation is based on near-infrared spectroscopy (NIRS), an optical method of illuminating chemical compounds which absorb, reflect, and scatter light directed at that compound. Methods. An integrative review was conducted to develop a context of greater understanding about complex topics. An Integrative review draws on multiple experimental and nonexperimental research methodologies. Results. Fourteen studies were graded at the C category. None reported the use of probability sampling or demonstrated a cause-and-effect relationship between StO2 values and patient outcomes. Conclusions. Future research should be based on rigorous methods of sampling and design in order to enhance the internal and external validity of the findings.

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

BACKGROUND

Near-infrared spectroscopy-derived tissue hemoglobin saturation (StO2) is a noninvasive measurement that reflects changes in microcirculatory tissue perfusion. Previous studies in trauma patients have shown a correlation between low StO2 levels and mortality, organ failure, and severity of injury. The goals of this study were to identify the incidence of low StO2 in the critically ill patient population of a surgical intensive care unit (SICU) and evaluate the relationship of low StO2 and clinical outcomes.

METHODS

We conducted a prospective cohort study at the University of Minnesota Medical Center. After institutional review board approval, 620 patients admitted to the SICU between July 2010 and July 2011 were screened for enrollment. Patients with an expected ICU length of stay of less than 24 hours were excluded. In the 490 patients who met inclusion criteria, StO2 measurements were obtained from the thenar eminence one to three times daily for the length of the ICU stay, up to 14 days. Outcome data included 28-day hospital mortality; ICU readmission; ventilator-free, ICU-free, and hospital-free days; and the need for lifesaving interventions.

RESULTS

The overall incidence of low StO2 (<70%) was 11% of the patients per day. Patients with at least 1 day in the SICU with an StO2 measurement of less than 70% had higher rates of ICU readmission and fewer ventilator-free, ICU-free, and hospital-free days compared with those who did not. Mortality (28-day in-hospital) trended higher for these patients but was not statistically significant. An increase in the number of days with StO2 less than 70% was also associated with fewer ventilator-free, ICU-free, and hospital-free days.

CONCLUSION

Low StO2 (<70%) is common and associated with poor outcomes in SICU patients. Near-infrared spectroscopy represents a potentially useful, noninvasive adjunct to monitoring of critically ill patients.

LEVEL OF EVIDENCE

Prognostic study, level II.

Association between static and dynamic thenar near-infrared spectroscopy and mortality in patients with sepsis: a systematic review and meta-analysis

BACKGROUND

Oxygen delivery and consumption disturbances are frequently seen with critically illness, potentially leading to pathologic changes in tissue oxygenation (StO2). Near-infrared spectroscopy (NIRS) is a potentially useful method to monitor StO2, but the role of NIRS in prognostication of septic patients is uncertain. The aim of this study was to systematically review the literature and evaluate static and dynamic NIRS in patients with sepsis.

METHODS

This is a systematic review and meta-analysis of publications between 1966 and 2013. The MEDLINE and EMBASE databases were searched for studies on StO2 in patients with severe sepsis or septic shock. Meta-analysis was limited to studies about static and dynamic variables derived from NIRS in patients with sepsis. The association between StO2, reperfusion slope (Rres), occlusion slope, and maximum StO2 minus basal StO2 (ΔStO2) and prognosis in septic patients was evaluated.

RESULTS

The search identified 20 articles (962 participants; 717 with severe sepsis or septic shock, and 245 healthy controls). Compared with healthy controls, septic patients had lower levels of StO2 (78.27% [4.91%] vs. 82.02% [3.57%], p = 0.012), Rres (2.75% [0.63%] vs. 5.19% [2.86%] per second, p = 0.003), and ΔStO2 (7.86% [0.11%] vs. 12.53% [2.65%], p = 0.011). Survivors from sepsis presents higher levels of StO2 (81.68% [4.68%] vs. 74.54% [5.31%], p = 0.02) and Rres (3.37% [0.44%] vs. 2.16% [0.51%] per second, p = 0.016).

CONCLUSION

Septic patients have lower levels of StO2, Rres and ΔStO2, and survivors from sepsis present higher levels of StO2 and Rres compared with nonsurvivors.

LEVEL OF EVIDENCE

Systematic review/meta-analysis, level III.

[Mitochondrial and microcirculatory distress syndrome in the critical patient. Therapeutic implications]

Mitochondrial and microcirculatory distress syndrome (MMDS) can occur during systemic inflammatory response syndrome (SIRS), and is characterized by cytopathic tissue hypoxia uncorrected by oxygen transport optimization, and associated with an acquired defect in the use of oxygen and energy production in mitochondria, leading to multiple organ dysfunction (MOD). We examine the pathogenesis of MMDS, new diagnostic methods, and recent therapeutic approaches adapted to each of the three phases in the evolution of the syndrome. In the initial phase, the aim is prevention and early reversal of mitochondrial dysfunction. Once the latter is established, the aim is to restore flow of the electron chain, mitochondrial respiration, and to avoid cellular energy collapse. Finally, in the third (resolution) stage, treatment should focus on stimulating mitochondrial biogenesis and the repair or replacement of damaged mitochondria.

Relationship between red cell storage duration and outcomes in adults receiving red cell transfusions: a systematic review

INTRODUCTION

The duration of red blood cell (RBC) storage before transfusion may alter RBC function and supernatant and, therefore, influence the incidence of complications or even mortality.

METHODS

A MEDLINE search from 1983 to December 2012 was performed to identify studies reporting age of transfused RBCs and mortality or morbidity in adult patients.

RESULTS

Fifty-five studies were identified; most were single-center (93%) and retrospective (64%), with only a few, small randomized studies (eight studies, 14.5%). The numbers of subjects included ranged from eight to 364,037. Morbidity outcomes included hospital and intensive care unit (ICU) length of stay (LOS), infections, multiple organ failure, microcirculatory alterations, cancer recurrence, thrombosis, bleeding, vasospasm after subarachnoid hemorrhage, and cognitive dysfunction. Overall, half of the studies showed no deleterious effects of aged compared to fresh blood on any endpoint. Eleven of twenty-two (50%) studies reported no increased mortality, three of nine (33%) showed no increased LOS with older RBCs and eight of twelve (66%) studies showed no increased risks of organ failure. Ten of eighteen (55%) studies showed increased infections with transfusion of older RBCs. The considerable heterogeneity among studies and numerous methodological flaws precluded a formal meta-analysis.

CONCLUSIONS

In this systematic review, we could find no definitive argument to support the superiority of fresh over older RBCs for transfusion.

Monitoring devices in the intensive care unit

Monitors in the intensive care unit are imperative to taking adequate care of these critically ill patients. Cardiovascular, pulmonary, and neurologic monitors are key to performing these tasks. This article gives an overview of the most common monitors that are used in the intensive care unit.

Monitoring in the intensive care

In critical care, the monitoring is essential to the daily care of ICU patients, as the optimization of patient's hemodynamic, ventilation, temperature, nutrition, and metabolism is the key to improve patients' survival. Indeed, the decisive endpoint is the supply of oxygen to tissues according to their metabolic needs in order to fuel mitochondrial respiration and, therefore, life. In this sense, both oxygenation and perfusion must be monitored in the implementation of any resuscitation strategy. The emerging concept has been the enhancement of macrocirculation through sequential optimization of heart function and then judging the adequacy of perfusion/oxygenation on specific parameters in a strategy which was aptly coined “goal directed therapy.” On the other hand, the maintenance of normal temperature is critical and should be regularly monitored. Regarding respiratory monitoring of ventilated ICU patients, it includes serial assessment of gas exchange, of respiratory system mechanics, and of patients' readiness for liberation from invasive positive pressure ventilation. Also, the monitoring of nutritional and metabolic care should allow controlling nutrients delivery, adequation between energy needs and delivery, and blood glucose. The present paper will describe the physiological basis, interpretation of, and clinical use of the major endpoints of perfusion/oxygenation adequacy and of temperature, respiratory, nutritional, and metabolic monitorings.

Near infrared spectroscopy (NIRS) of the thenar eminence in anesthesia and intensive care

Near infrared spectroscopy of the thenar eminence (NIRS_th) is a noninvasive bedside method for assessing tissue oxygenation. The NIRS probe emits light with several wavelengths in the 700- to 850-nm interval and measures the reflected light mainly from a predefined depth. Complex physical models then allow the measurement of the relative concentrations of oxy and deoxyhemoglobin, and thus tissue saturation (StO₂), as well as an approximation of the tissue hemoglobin, given as tissue hemoglobin index.

Here we review of current knowledge of the application of NIRS_th in anesthesia and intensive care.

We performed an analytical and descriptive review of the literature using the terms “near-infrared spectroscopy” combined with “anesthesia,” “anesthesiology,” “intensive care,” “critical care,” “sepsis,” “bleeding,” “hemorrhage,” “surgery,” and “trauma” with particular focus on all NIRS studies involving measurement at the thenar eminence.

We found that NIRS_th has been applied as clinical research tool to perform both static and dynamic assessment of StO₂. Specifically, a vascular occlusion test (VOT) with a pressure cuff can be used to provide a dynamic assessment of the tissue oxygenation response to ischemia. StO₂ changes during such induced ischemia-reperfusion yield information on oxygen consumption and microvasculatory reactivity. Some evidence suggests that StO₂ during VOT can detect fluid responsiveness during surgery. In hypovolemic shock, StO₂ can help to predict outcome, but not in septic shock. In contrast, NIRS parameters during VOT increase the diagnostic and prognostic accuracy in both hypovolemic and septic shock. Minimal data are available on static or dynamic StO₂ used to guide therapy.

Although the available data are promising, further studies are necessary before NIRS_th can become part of routine clinical practice.

Review article: Part two: Goal-directed resuscitation--which goals? Perfusion targets

Haemodynamic targets, such as cardiac output, mean arterial blood pressure and central venous oxygen saturations, remain crude predictors of tissue perfusion and oxygen supply at a cellular level. Shocked patients may appear adequately resuscitated based on normalization of global vital signs, yet they are still experiencing occult hypoperfusion. If targeted resuscitation is employed, appropriate use of end-points is critical. In this review, we consider the value of directing resuscitation at the microcirculation or cellular level. Current technologies available include sublingual capnometry, video microscopy of the microcirculation and near-infrared spectroscopy providing a measure of tissue oxygenation, whereas base deficit and lactate potentially provide a surrogate measure of the adequacy of global perfusion. The methodology and evidence for these technologies guiding resuscitation are considered in this narrative review.

Resuscitation and monitoring in gastrointestinal bleeding

INTRODUCTION

Gastrointestinal bleeding is a common life-threatening problem, causing significant mortality, costs and resource allocation. Its management requires a dynamic multidisciplinary approach that directs diagnostic and therapeutic priorities appropriately.

MATERIALS AND METHODS

Articles published within the past 15 years, related to gastrointestinal bleeding, were reviewed through MEDLINE search, in addition to current guidelines and standards.

RESULTS

Decisions of ICU admission and blood transfusion must be individualized based on the extent of bleeding, hemodynamic profile and comorbidities of the patient and the risk of rebleeding. A secure airway may be required to optimize oxygenation and to prevent aspiration. Doses of induction agents must be reduced due to the changes in volume of distribution. Volume replacement is the cornerstone of resuscitation in profuse bleeding, but nontargeted aggressive fluid resuscitation must be avoided to allow clot formation and to prevent increased bleeding. Decision to give blood transfusion must be based on physiologic triggers rather than a fixed level of hemoglobin. Coagulopathy must be corrected and hypothermia avoided. Need for massive transfusion must be recognized as early as possible, and a 1:1:1 ratio of packed red blood cells, fresh frozen plasma and platelets is recommended to prevent dilutional coagulopathy. Tromboelastography can be used to direct hemostatic resuscitation. Transfusion related lung injury (TRALI) is a significant problem with a mortality rate approaching 40%. Prevention of TRALI is important in patients with gastrointestinal bleeding, especially among patients having end-stage liver disease. Preventive strategies include prestorage leukoreduction, use of male-only or never-pregnant donors and avoidance of long storage times. Management of gastrointestinal bleeding requires delicately tailoring resuscitation to patient needs to avoid nonspecific aggressive resuscitation. "Functional hemodynamic monitoring" requires recognition of indications and limitations of hemodynamic measurements. Dynamic indices like systolic pressure variation are more reliable predictors of volume responsiveness. Noninvasive methods of hemodynamic monitoring and cardiac output measurement need further verification in patients with gastrointestinal bleeding.

CONCLUSIONS

Management of gastrointestinal bleeding requires a dynamic multidisciplinary approach. The mentioned advances in management of hemorrhagic shock must be considered in resuscitation and monitoring of patients with GI bleeding.

Near-infrared spectroscopy in the critical setting

Near-infrared spectroscopy is a noninvasive means of determining real-time changes in regional oxygen saturation of cerebral and somatic tissues. Hypoxic neurologic injuries not only involve devastating effects on patients and their families but also increase health care costs to the society. At present, monitors of cerebral function such as electroencephalograms, transcranial Doppler, jugular bulb mixed venous oximetry, and brain tissue oxygenation monitoring involve an invasive procedure, are operator-dependent, and/or lack the sensitivity required to identify patients at risk for cerebral hypoxia. Although 20th century advances in the understanding and management of resuscitation of critically ill and injured children have focused on global parameters (ie, pulse oximetry, capnography, base deficit, lactate, etc), a growing body of evidence now points to regional disturbances in microcirculation that will lead us in a new direction of adjunctive tissue monitoring and response to resuscitation. In the coming years, near-infrared spectroscopy will be accepted as a way for clinicians to more quickly and noninvasively identify patients with altered levels of cerebral and/or somatic tissue oxygenation and, in conjunction with global physiologic parameters, guide efficient and effective resuscitation to improve outcomes for critically ill and injured pediatric patients.

Clinical and cellular effects of hypothermia, acidosis and coagulopathy in major injury

BACKGROUND

Hypothermia, acidosis and coagulopathy have long been considered critical combinations after severe injury. The aim of this review was to give a clinical update on this triad in severely injured patients.

METHODS

A non-systematic literature search on hypothermia, acidosis and coagulopathy after major injury was undertaken, with a focus on clinical data from the past 5 years.

RESULTS

Hypothermia (less than 35 °C) is reported in 1·6-13·3 per cent of injured patients. The occurrence of acidosis is difficult to estimate, but usually follows other physiological disturbances. Trauma-induced coagulopathy (TIC) has both endogenous and exogenous components. Endogenous acute traumatic coagulopathy is associated with shock and hypoperfusion. Exogenous effects of dilution from fluid resuscitation and consumption through bleeding and loss of coagulation factors further add to TIC. TIC is present in 10-34 per cent of injured patients, depending on injury severity, acidosis, hypothermia and hypoperfusion. More expedient detection of coagulopathy is needed. Thromboelastography may be a useful point-of-care measurement. Management of TIC is controversial, with conflicting reports on blood component therapy in terms of both outcome and ratios of blood products to other fluids, particularly in the context of civilian trauma.

CONCLUSION

The triad of hypothermia, acidosis and coagulopathy after severe trauma appears to be fairly rare but does carry a poor prognosis. Future research should define modes of early detection and targeted therapy.