Peripheral Tissue Oxygenation Research Articles

Reference ranges of peripheral-muscle oxygenation in term neonates delivered by Caesarean section during immediate transition after birth.

To establish reference ranges of peripheral-muscle regional oxygen saturation (prSO2) and peripheral fractional tissue oxygen extraction (pFTOE) during the first 15 min after birth in stable term neonates. Secondary outcome parameters of prospective observational studies in healthy term neonates delivered by Caesarean section were analysed. prSO2 was measured on the right forearm using the INVOS 5100C monitor. pFTOE was calculated out of prSO2 and arterial oxygen saturation (SpO2). Centile charts (10th-90th) of prSO2 and pFTOE were defined during the first 15 min after birth. Three-hundred-five term neonates with a mean gestational age and birth weight of 39.0 ± 0.9 weeks and 3321 ± 454 g, respectively, were included. The 50th centiles of prSO2 were 39% (minute two), 52% (minute five), 71% (minute 10), and 73% (minute 15). The 50th centiles of pFTOE were 0.529 (minute two), 0.378 (minute five), 0.237 (minute 10), and 0.231 (minute 15). Reference ranges of prSO2 and pFTOE were established for term neonates delivered by Caesarean section during the immediate transition after birth. These reference ranges increase knowledge of physiological processes taking place immediately after birth and are necessary for possible future clinical applications.

Red Blood Cell Adenylate Energetics Is Related to Endothelial and Microvascular Function in Long COVID.

Adenine nucleotides play a critical role in maintaining essential functions of red blood cells (RBCs), including energy metabolism, redox status, shape fluctuations and RBC-dependent endothelial and microvascular functions. Recently, it has been shown that infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) might lead to morphological and metabolic alterations in erythrocytes in both mild and severe cases of coronavirus disease (COVID-19). However, little is known about the effects of COVID-19 on the nucleotide energetics of RBCs nor about the potential contribution of nucleotide metabolism to the long COVID syndrome. This study aimed to analyze the levels of adenine nucleotides in RBCs isolated from patients 12 weeks after mild SARS-CoV-2 infection who suffered from long COVID symptoms and to relate them with the endothelial and microvascular function parameters as well as the rate of peripheral tissue oxygen supply. Although the absolute quantities of adenine nucleotides in RBCs were rather slightly changed in long COVID individuals, many parameters related to the endothelial and microcirculatory function showed significant correlations with RBC adenosine triphosphate (ATP) and total adenine nucleotide (TAN) concentration. A particularly strong relationship was observed between ATP in RBCs and the serum ratio of arginine to asymmetric dimethylarginine-an indicator of endothelial function. Consistently, a positive correlation was also observed between the ATP/ADP ratio and diminished reactive hyperemic response in long COVID patients, assessed by the flow-mediated skin fluorescence (FMSF) technique, which reflected decreased vascular nitric oxide bioavailability. In addition, we have shown that patients after COVID-19 have significantly impaired ischemic response parameters (IR max and IR index), examined by FMSF, which revealed diminished residual bioavailability of oxygen in epidermal keratinocytes after brachial artery occlusion. These ischemic response parameters revealed a strong positive correlation with the RBC ATP/ADP ratio, confirming a key role of RBC bioenergetics in peripheral tissue oxygen supply. Taken together, the outcomes of this study indicate that dysregulation of metabolic processes in erythrocytes with the co-occurring endothelial and microvascular dysfunction is associated with diminished intracellular oxygen delivery, which may partly explain long COVID-specific symptoms such as physical impairment and fatigue.

Peripheral muscle fractional tissue oxygen extraction in stable term and preterm neonates during the first 24 h after birth.

Peripheral muscle fractional tissue oxygen extraction (pFTOE) represents the relative extraction of oxygen from the arterial to venous compartment, providing information about dynamic changes of oxygen delivery and oxygen consumption. The aim of the present study was to establish reference values of pFTOE during the first 24 h after birth in stable term and late preterm neonates. The present study is a post-hoc analysis of secondary outcome parameters of prospective observational studies. Only stable neonates without infection, asphyxia and any medical support were eligible for our analysis to obtain normal values. For measurements of peripheral muscle tissue oxygenation index (pTOI) during the first 24 h after birth in term and preterm neonates, the NIRO200/NIRO200NX was used. Arterial oxygen saturation (SpO2) was obtained by pulse oximetry. pFTOE was calculated out of pTOI and SpO2: pFTOE = (SpO2-pTOI)/SpO2. Measurements of neonates were stratified into four groups according to their respective measurement time point (6 h periods) after birth. Term and preterm neonates were analyzed separately. Mean values of measurements during the first time period (0-6 h after birth) were compared to measurements of the following time periods (second = 7-12 h, third = 13-18 h, fourth = 19-24 h after birth). Two-hundred-fourty neonates (55 term and 185 late preterm neonates) had at least one peripheral muscle NIRS measurements within the first 24 h after birth. Mean gestational age and birth weight were 39.4 ± 1.1 weeks and 3360 (2860-3680)g in term neonates and 34.0 ± 1.4 weeks and 2060 (1750-2350)g in preterm neonates, respectively. In term neonates pFTOE was 0.264 (0.229-0.300), 0.228 (0.192-0.264), 0.237 (0.200-0.274) and 0.220 (0.186-0.254) in the first, second, third and fourth time period. In preterm neonates pFTOE was 0.229 (0.213-0.246), 0.225 (0.209-0.240), 0.226 (0.210-0.242) and 0.238 (0.222-0.255) in the first, second, third and fourth time period. pFTOE did not show any significant changes between the time periods, neither in term nor in preterm neonates. We provide reference values of pFTOE for stable term and late preterm neonates within the first 24 h after birth, which were stable when comparing four 6-h periods. These normal values are of great need for interpreting pFTOE in scientific context as well as for potential future clinical applications.

The Roles of Renal Oxygen Saturation in Septic Shock Children.

Septic shock, the most severe form of sepsis, has high morbidity and mortality rates among children. In patients with septic shock, impaired microcirculatory perfusion is associated with the severity of organ failure and the likelihood of death. Because near-infrared spectroscopy (NIRS) can assess microcirculation status and peripheral tissue oxygenation directly and noninvasively, provides real-time results, and can be performed at the patient's bedside. This study aimed to determine the prognostic value of renal oxygen saturation (rRSO2) measured by NIRS in septic shock among children. This prospective observational study enrolled children aged 1 month to 18 years with septic shock who were treated in a pediatric intensive care unit from August 2020 to January 2021. NIRS was used to measure rRSO2 in patients diagnosed with septic shock according to the Third International Consensus Definition of Sepsis and Septic Shock. The baseline rRSO2 value (%) formed a receiver operating characteristic curve and was used to calculate the optimal cutoff value, sensitivity, specificity, and odds ratio (OR). We enrolled 24 patients, 13 nonsurvivors and 11 survivors, whose mean baseline rRSO2 values were 67.27 ± 12.95 versus 48.69 ± 16.17, respectively (P = 0.006). The optimal cutoff value for baseline rRSO2 was <60.5%, with a sensitivity of 76.9%, a specificity of 81.8%, and an area under curve 0.804 (95% confidence interval [CI]: 59.2%-98.1%, P = 0.012; OR = 15; 95 CI: 2.04-111.74). Measured by NIRS, rRSO2 values are a good predictor of mortality among children with septic shock.

Prehospital end-tidal carbon dioxide measurement

The prehospital environment presents numerous challenges regarding the diagnosis and subsequent management of critically ill patients—diagnostic aids are limited; point-of-care testing is almost universally unavailable and senior medical advice can be beyond timely reach. Pulse oximetry provides real-time assessment of peripheral tissue oxygen saturation, but not of ventilation adequacy. The past decade has seen the gradual introduction of end-tidal carbon dioxide monitoring or capnography into routine resuscitation practice following successive national audit reports, coronial reports and subsequent guidance regarding safe airway management. However, capnography alone does not prevent adverse outcomes, particularly if it is not properly interpreted. Capnography is now regarded as essential monitoring whenever airway management or ventilation is required. The increasing availability of capnography in the prehospital setting can provide dynamic, real-time information that can aid assessment and treatment of pathology at the first point of contact and direct onward management. This article reviews the pathophysiology associated with the production, transport and excretion of carbon dioxide and suggests a number of ways in which accurate measurement and interpretation can potentially be a useful diagnostic tool and inform management choices in the prehospital setting.

Chronic PCSK9 inhibitor therapy leads to sustained improvements in endothelial function, arterial stiffness, and microvascular function.

Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) effectively decrease low-density lipoprotein cholesterol (LDL-C) and reduce cardiovascular events in patients at very high cardiovascular risk. Recent short-term studies suggest a partially LDL-C independent beneficial effect of PCSK9 inhibitor (PCSK9i) therapy on endothelial function and arterial stiffness, whereas it is unknown if this effect persists and what the effect is on microcirculation. To investigate the effects of PCSK9i therapy on vascular parameters beyond its lipid lowering effect. In this prospective trial, 32 patients at very high cardiovascular risk and indication for PCSK9i therapy were included. Measurements were performed at baseline and after 6 months of PCSK9i treatment. Endothelial function was assessed as flow-mediated dilation (FMD). Arterial stiffness was measured as pulse wave velocity (PWV) and aortic augmentation index (AIx). Peripheral tissue oxygenation (StO2) as a marker of microvascular function was assessed at the distal extremities using near-infrared spectroscopy camera. Six months of PCSK9i therapy decreased LDL-C levels from 141 ± 54 to 60 ± 30 mg/dl (-56 ± 21 %, p < 0.001), FMD significantly increased from 5.4 ± 1.7 % to 6.4 ± 1.9 % (+19 ± 10 %, p < 0.001), PWV decreased in male patients significantly from 8.9 ± 2.1 to 7.9 ± 1.5 m/s (-12 ± 9 %, p = 0.025). AIx decreased from 27.1 ± 10.4 % to 23.0 ± 9.7 % (-16 ± 14 %, p < 0.001), StO2 significantly increased from 67 ± 12 % to 71 ± 11 % (+7 ± 6 %, p = 0.012). Brachial and aortic blood pressure showed no significant changes after six months. There was no correlation between LDL-C reduction and changes in vascular parameters. Chronic PCSK9i therapy is associated with sustained improvements in endothelial function, arterial stiffness, and microvascular function independent from lipid lowering.

Spatial-Temporal Oxygenation Mapping Using a Near-Infrared Optical Scanner: Towards Peripheral Vascular Imaging.

Near-infrared spectroscopy (NIRS)-based peripheral perfusion, or microcirculation, can be used to assess the severity of peripheral vascular dysfunction. A low-cost, portable non-contact near-infrared optical scanner (NIROS) was developed for spatio-temporal mapping of tissue oxygenation and perfusion in tissues. In vivo validation studies were carried out on control subjects (n = 3) to assess the ability of NIROS to measure real-time oxygenation changes in response to an occlusion paradigm on the dorsum of the hand. NIROS captured real-time tissue oxygenation changes with 95% correlation when compared to a commercial device. A feasibility peripheral imaging study was performed in a mouse model (n = 5) of chronic kidney disease (CKD) induced vascular calcification to assess differences in microcirculatory peripheral tissue oxygenation. The tissue oxygenation (in terms of oxy-, deoxy-, and total hemoglobin changes) due to the occlusion paradigm was distinctly different prior to (week-6) and after the onset of vascular calcification (week-12) in the murine tails. Future work will involve extensive studies to correlate these microcirculatory tissue oxygenation changes in the peripheral tail to the vascular calcification in the heart.

Effective Monitoring for Early Detection of Hypoxia in Fighter Pilots

ABSTRACT Objective This study evaluated various biological parameters in subjects exposed to hypoxia, to verify effective monitoring for early hypoxia detection. Background Hypoxic-hypoxia is a life-threatening condition, but no method of early detection in flight has been established. Method Six healthy male subjects underwent 2 experiments at different oxygen concentrations (O2) during hypoxic exposure on different days. Subjects inhaled approximately 21% O2 for 3 minutes, hypoxia using approximately 14% O2 in Experiment 1 and 7% O2 in Experiment 2 for 3.5 minutes using a reduced oxygen breathing device. During the experiments, pupil diameter (PD), cerebral oxygenated hemoglobin (O2Hb), peripheral tissue oxygen saturation (SpO2), heart rate (HR), and blood pressure (BP) were measured. Results All 6 subjects completed both Experiments 1 and 2. ΔO2Hb showed significant correlations with %HR (r = −0.6005, P < .0001), %PD (r = −0.5227, P = .0001), and %SpO2 (r = 0.8281, P < .0001) in Experiment 1. ΔO2Hb also showed significant correlations with %HR (r = −0.7904, P < .0001), %PD (r = −0.7933, P < .0001), and %SpO2 (r = 0.7240, P < .0001) in Experiment 2. Rapid hypoxic exposure caused increase in %PD and decrease in ΔO2Hb, followed by immediate increase in %HR, and then decrease in %SpO2. Conclusion The present study suggested that monitoring of HR, PD, and O2Hb were earlier parameters to detect hypoxia than SpO2.

Comparison Of Peripheral Tissue Oxygen Saturation Between Patients With Heart Failure And Controls During A Submaximal Exercise Test: A Pilot Study

Comparison Of Peripheral Tissue Oxygen Saturation Between Patients With Heart Failure And Controls During A Submaximal Exercise Test: A Pilot Study

Зміни варіабельності серцевого ритму та периферичної гемодинаміки під час впливу об’ємного пневмопресингу в осіб з різним типом регуляції автономної нервової системи

Intermittent pneumatic compression (IPC) widely used in the therapy of preventing the formation of blood clots, improving the oxygenation of peripheral tissues. IPC is an established method in the therapy of post-operative recovery and in geriatrics and sports medicine. The purpose of our study was to determine functional changes in heart rate variability (HRV) and peripheral hemodynamics during exposure to lowintensity IPC depending on different types of regulation of the autonomic nervous system. We investigated 62 participants in age of 18-22 years. Testing sessions that included pressure of 40 mmHg and 20-minute period of temporary occlusion of the lower extremities was performed by intermittent pneumatic compression with Recovery Pump PRX device (“Mego Aftek AC Ltd”, Israel). During the procedure exposure and recovery period, arterial blood pressure was recorded with Korotkov’s auscultative method by mercury tonometer (“Dr. Frei”A-10, Switzerland). Heart Rate was monitored using a Cardio Trainer Polar H9 (“Polar Electro Oy”, Finland). For monitoring hemodynamic changes, impedance cardiography (ICG) method (“ХАІ-medica”, Kharkiv, Ukraine) was applied by 15 s. Based on the spectrum power values in the range of 0.15–0.4 (HFnorm), 3 groups of volunteers were determined using sigma deviations. Group 1 included 29 volunteers with an advantage of the sympathetic link of regulation of the autonomic nervous system (the background HFnorm was less than 40 nu). Group 2 included 19 persons with a normotonic type of autonomic nervous system regulation (HFnorm from 40 to 60 nu). Group 3 included 14 individuals with predominance of the parasympathetic link of the autonomic nervous system (HFnorm above 60 nu). In conclusion, IPC treatment in groups 1 and 2 inhibited the sympathetic activation, increased the blood flow in the large femoral arteries and tone of small arteries. In group 3, the blood outflow from the lower extremities was predominance, the blood flow volume and speed decreased. Therefore, we conclude effectivity of the low intensity IPC using. Also, HRV and peripheral hemodynamics depend on the types of regulation of the autonomic nervous system.

Five Days of Tart Cherry Supplementation Improves Exercise Performance in Normobaric Hypoxia.

Previous studies have shown tart cherry (TC) to improve exercise performance in normoxia. The effect of TC on hypoxic exercise performance is unknown. This study investigated the effects of 5 days of tart cherry (TC) or placebo (PL) supplementation on hypoxic exercise performance. Thirteen healthy participants completed an incremental cycle exercise test to exhaustion (TTE) under two conditions: (i) hypoxia (13% O2) with PL and (ii) hypoxia with TC (200 mg anthocyanin per day for 4 days and 100 mg on day 5). Pulmonary gas exchange variables, peripheral arterial oxygen saturation (SpO2), deoxygenated hemoglobin (HHb), and tissue oxygen saturation (StO2) assessed by near-infrared spectroscopy in the vastus lateralis muscle were measured at rest and during exercise. Urinary 8-hydro-2' deoxyguanosine (8-OHdG) excretion was evaluated pre-exercise and 1 and 5 h post-exercise. The TTE after TC (940 ± 84 s, mean ± standard deviation) was longer than after PL (912 ± 63 s, p &lt; 0.05). During submaximal hypoxic exercise, HHb was lower and StO2 and SpO2 were higher after TC than PL. Moreover, a significant interaction (supplements × time) in urinary 8-OHdG excretion was found (p &lt; 0.05), whereby 1 h post-exercise increases in urinary 8-OHdG excretion tended to be attenuated after TC. These findings indicate that short-term dietary TC supplementation improved hypoxic exercise tolerance, perhaps due to lower HHb and higher StO2 in the working muscles during submaximal exercise.

Near infrared spectroscopy in monitoring of head and neck microvascular free flaps.

Microvascular free‑flap monitoring is crucial to the early detection of flap failure and increases the chance of early intervention in case of disruption of perfusion to a flap. Many clinical alternatives to classical clinical flap monitoring have been proposed, such as color duplex ultrasonography, handheld Doppler, flap thermometry, or implantable Doppler flowmetry. Early detection of critical changes in tissue oxygenation can lead to successful surgical intervention when problems with flap nutrition arise. Our clinical study seeks to investigate dynamic monitoring of free flaps with near‑infrared spectroscopy (NIRS). NIRS is a non-invasive instrumental technique used for continuous monitoring of peripheral tissue oxygenation (StO2) and microcirculation. All patients were included prospectively from one clinical center. During the clinical research period, 18 patients underwent extraoral head and neck reconstruction with one of three types of free flap, namely with radial forearm free flap (RFFF), anterolateral thigh flap (ALT) or fibula free flap (FFF). Measurements of flap perfusion were taken using NIRS during intraoperative and postoperative phases for 71 hours on average. A total of 6 perfusion disorders were recorded, of which three originated from microanastomoses and three from postoperative bleeding and compression of pedicle. NIRS showed characteristic changes in all 6 cases that were returned to the operating theatre owing to pedicle compromise. In these cases, NIRS had detected the pedicle compromise before it was clinically identified. A single StO2 monitoring was able to detect the vascular compromise with 100% sensitivity and 95.65% specificity. None of the cases were falsely positive. In our study, all compromised flaps were accurately identified by means of NIRS. In most cases, the changes in oxygen saturation became evident on NIRS prior to being clinically observed. In our study, the continuous NIRS monitoring securely detected the early stages of arterial and venous thromboses or pedicle compression. The most important aspects of monitoring the flaps´ microvascular perfusion and vitality by means of NIRS lie in its function of recording the dynamics of changes in the values ​​of absolute oxygen saturation (StO2> 50%) alongside with detecting a 30% decrease in tissue saturation over a 60‑minute interval (60 min StO2 >30%) before the clinical changes in the microvascular flap become observable. In cases of pedicle compression, the average time of appearance of signs of StO2 values dropping below the reference interval (as detected by NIRS) was 1:29:02 hour (SD= 0:58:42 h) prior to the occurrence of any clinical signs, while in cases of microvascular anastomosis complications, it was 0:35:23 hour (SD=0:08:30 h) (SD = 0:08:30 h) (Tab. 3, Fig. 7, Ref. 42).

Abdominal and Peripheral Tissue Oxygen Supply during Selective Lower Body Perfusion for the Surgical Repair of Congenital Heart Disease: A Pilot Study.

Lower body perfusion (LBP) may be a strategy for maintaining organ perfusion during congenital heart disease surgery. It is hypothesized that renal and lower limb oxygen supply during LBP is superior to off-pump surgery and comparable to that of a standard cardiopulmonary bypass (CPB). in this prospective single-center study, patients aged &lt;1 year were recruited if they were scheduled for a correction of aortic arch anomalies using antegrade cerebral perfusion and LBP (group 1), a repair of coarctation during aortic cross-clamping (group 2), or surgery under whole-body CPB (group 3). Renal (prefix "r") and peripheral (prefix "p") oxygen saturation (SO2), hemoglobin amount (Hb), blood velocity (Velo), and blood flow (Flow) were measured noninvasively. A total of 23 patients were included (group 1, n = 9; group 2, n = 5; group 3, n = 9). Compared to the baseline values, rSO2 and pSO2 decreased significantly in group 2 compared to groups 1 and 3. Conversely, rHB significantly increased in group 2 compared to groups 1 and 3, reflecting abdominal venous stasis. Compared to group 3, group 1 showed a significantly lower pFlow during CPB; however, rFlow, pFlow, and pVelo did not differ. according to these observations, LBP results in an improved renal oxygen supply compared to off-pump surgery and may prove to be a promising alternative to conventional CPB.

Use of combined cerebral and somatic renal near infrared spectroscopy during noncardiac surgery in children: a proposed algorithm.

Cerebral near infrared spectroscopy (NIRS) monitoring has been extensively applied in neonatology and in cardiac surgery, becoming a standard in many pediatric cardiac centers. However, compensatory physiological mechanisms favor cerebral perfusion to the detriment of peripheral tissue oxygenation. Therefore, simultaneous measurement of cerebral and somatic oxygen saturation has been advocated to ease the differential diagnosis between central and peripheral sources of hypoperfusion, which may go undetected by standard monitoring and not mirrored by cerebral NIRS alone. A clinical algorithm already exists in cardiac surgery, aimed to correct intraoperative cerebral oxygen desaturations. A similar algorithm still lacks in noncardiac pediatric surgery. The goal of this paper is to propose a clinical algorithm for the combined use of cerebral and somatic NIRS monitoring during anesthesia in the pediatric population undergoing noncardiac surgery. A panel of experienced pediatric anesthetists developed the algorithm that is based on the clinical experience and intraoperative observations. It aims to lessen the current variability in interpreting NIRS measurement. Multisite NIRS monitoring was achieved applying one pediatric sensor to the forehead for cerebral tissue perfusion reading and a second one to the decumbent lumbar region for recording somatic renal tissue perfusion. The algorithm describes a sequence of acts aimed to identify the putative cause of intraoperative organ tissue desaturation and suggests clinical interventions expected to restore adequate tissue perfusion. It is composed of two arms: the main arm includes patients with an observed decrease in cerebral perfusion (CrO2), the second one includes those with a stable CrSO2 with declining RrSO2. Described also are five clinical cases of infants and neonates in whom pathological alterations of organ perfusion were detected using intraoperative multisite NIRS monitoring, portrayed in the accompanying figures (Annex).

Oxygen Saturation in Primary Teeth of Individuals With Sickle Cell Disease and Sickle Cell Trait.

PurposeTo determine oxygen saturation in the pulp of primary teeth in children with sickle cell disease (SCD) and sickle cell trait (SCT) for establishing the usefulness of pulse oximetry in screening and monitoring of SCD or therapy.Materials and MethodsA cross-sectional study among 30–60 months children with sickle cell disease (SCD) and sickle cell trait (SCT) compared with healthy children (HbAA). A pulse oximeter (BCI 3301) recorded oxygen saturation on six anterior primary maxillary teeth and on index fingers. Data were analyzed using SPSS version 20.0. Mean oxygen saturation for teeth and fingers was calculated. Comparison of Mean across groups was done using post hoc analysis in one-way ANOVA (Bonferroni test). Pearson correlation coefficient was calculated for mean oxygen saturation on fingers and teeth. Level of significance was set at 0.05.ResultsAltogether 360, 102, and 96 teeth were examined from children with SCD, SCT, and HbAA respectively. 53% of participants were girls. The mean age of participants was 46.3 months ± 9.4 SD. Low mean oxygen saturation (77.5%) was recorded from teeth of children with SCD relative to those with SCT and HbAA (>86%; P = 0.00). There was no statistically significant difference in oxygen saturation on teeth between children with SCT and HbAA. The mean oxygen saturation on fingers was found to be above 97.2% regardless of sickle cell status. There was no correlation between oxygen saturation on teeth and fingers.ConclusionPulse oximeter detected a lower oxygen saturation in dental pulp of primary teeth of participants with SCD (HbSS) relative to those with SCT (HbAS) and HbAA. Oxygen saturation on fingers remained unaffected regardless of sickle cell disease status. Although more studies are needed, our study shows that when other conditions affecting peripheral tissue oxygen delivery are ruled out, the low pulse oximetry in primary teeth may be indicative of SCD. The oximeter may also be useful in monitoring response to SCD therapy targeted at improving oxygen carrying capacity and delivery.

The effects of total intravenous and inhalation anesthesia maintenance on tissue oxygenation in coronary artery bypass graft surgery.

The aim of this study is to evaluate the effect of total intravenous anesthesia (TIVA) and inhalational anesthesia techniques on tissue oxygenation in cardiac surgery. We compared the effects of midazolam-based TIVA and sevoflurane-based (SEVO) inhalation anesthesia maintenance on intraoperative central and regional tissue oxygenation parameters. A total of 104 adult patients who were scheduled for elective isolated coronary bypass surgery were included in the study. All patients were divided into two groups: the TIVA group consisted of total intravenous anesthesia maintenance patients (n=52) and the SEVO group consisted of patients with inhalation anesthesia with sevoflurane maintenance (n=52). Tissue oxygenation values were observed with left-right cerebral and somatic left forearm Near-Infrared Spectroscopy (NIRS) sensors. The hemodynamic parameters, NIRS StO2, central (ScvO2) and peripheral venous oxygen saturations of the patients were recorded at six intraoperative time points. The effects of midazolam-based TIVA and sevoflurane-based inhalation anesthesia maintenance on intraoperative central and peripheral tissue oxygenation parameters were compared and it was found that in the left forearm NIRS StO2 and ScvO2 values were higher in the SEVO group than the TIVA group. Although not significantly different, forearm regional venous oxygen saturation was also higher in the SEVO group. The effects of anesthetic drugs on regional tissue oxygenation can become important in critical patients and challenging surgeries. Sevoflurane-based anesthesia provides better tissue oxygenation than TIVA in patients undergoing coronary bypass surgery.

Laser Doppler Flowmetry Combined with Spectroscopy to Determine Peripheral Tissue Perfusion and Oxygen Saturation: A Pilot Study in Healthy Volunteers and Patients with Peripheral Arterial Disease.

Background: In this study, we assessed the ability of the EPOS system (Perimed AB, Järfälla, Stockholm, Sweden) to detect differences in tissue perfusion between healthy volunteers and patients with peripheral arterial disease (PAD) with different severity of disease. Methods: This single-center prospective pilot study included 10 healthy volunteers and 20 patients with PAD scheduled for endovascular therapy (EVT). EPOS measurements were performed at rest at 32 °C and 44 °C, followed by transcutaneous oxygen pressure (TcPo2) measurements. The measurements were performed on the dorsal and medial side of the foot, as well as the lateral side of the calf. EPOS parameters included hemoglobin oxygen saturation (HbSo2) and speed-resolved red blood cell (RBC) perfusion. Results: HbSo2 at 44 °C was significantly different between the three groups for all measurement locations. The overall speed-resolved RBC perfusion at 44 °C was statistically significant between the groups on the dorsal and medial side of the foot but not on the calf. TcPo2 values were not significantly different between the three groups. Conclusions: This study demonstrates that the EPOS system can depict differences in tissue perfusion between healthy volunteers, patients with Fontaine class IIb PAD, and those with Fontaine class III or IV PAD but only after heating to 44 °C.

Polyethylene glycol‐20 ameliorates tissue ischemia and improves renal function following traumatic shock

The “Golden Hour” policy used for US Troops in Iraq and Afghanistan has contributed to the highest survival rates for combat injury in history. Anticipated future combat operations require more options to optimize combat casualty care by extending “the Golden Hour” to “the Golden Day.” Low volume resuscitation with polyethylene glycol‐20K (PEG) has been shown to decrease mortality following hemorrhagic shock, however, the effect of PEG on tissue perfusion and renal function has not been determined. We hypothesized that PEG can ameliorate ischemia and prevent renal injury during prolonged traumatic shock. Anesthetized rats received extremity trauma (soft tissue injury and fracture in one hindlimb) and pressure‐controlled hemorrhage, with mean arterial pressure (MAP) maintained at 55mmHg. MAP, heart rate, renal blood flow (RBF, perivascular ultrasonic transit time flow probe), peripheral skeletal muscle microcirculatory flow and tissue oxygen partial pressure (OxyLite needle probes), blood gases, and electrolytes were monitored throughout the experiment. Glomerular filtration rate (GFR) was recorded using a non‐invasive Fluorescein isothiocyanate‐sinistrin transcutaneous technique. After 45 minutes of shock with MAP at 55mmHg, rats were randomly treated with an intravenous bolus of either 7.5% PEG or saline (1.3 ml/kg, n = 5/group). Measurements were continued from the 45th to the 165th minute without MAP control or any other treatment. Compared with saline, PEG markedly improved MAP recovery (P &lt; 0.001) and survival (P &lt; 0.01) (Figures 1A and 1B). Microcirculatory perfusion and oxygen partial pressure were markedly decreased after hemorrhage and saline treatment elicited no additional effect. However, with PEG, the decreases in capillary flow and tissue oxygen levels were significantly attenuated (P = 0.04 and 0.03, respectively) (Figure 2A). Moreover, blood lactate levels continuously increased in the saline group but returned to levels comparable to baseline within 30 minutes after PEG treatment (P &lt; 0.001) (Figure 2B). In the saline group, RBF markedly decreased concomitantly with a sustained increase in renal vascular resistance (RVR) during the shock period. PEG treatment rapidly restored RBF (P &lt; 0.001) to levels comparable to baseline along with a normalized RVR. GFR was diminished in the saline‐treated rats but was improved in the PEG‐treated group (0.07 ± 0.05 vs. 0.67 ± 0.06 ml/min/100g, respectively; P &lt; 0.001). These results provide strong evidence that PEG rapidly improves macro‐ and microcirculatory hemodynamics ameliorates tissue ischemia, and minimize renal injury and mortality following prolonged traumatic shock.

Non-invasively Measured Venous Oxygen Saturation as Early Marker of Impaired Oxygen Delivery in Preterm Neonates.

IntroductionAdequate oxygen supply for preterm neonates may be defined through non-invasive measurement of venous oxygen saturation (SvO2) and fractional oxygen extraction using near-infrared spectroscopy (NIRS). We investigated whether there was a difference in peripheral muscle SvO2 (pSvO2) and peripheral fractional oxygen extraction (pFOE) in preterm neonates with early inflammation/infection compared to healthy subjects during the first 72 h after birth.Materials and MethodsWe retrospectively analyzed secondary outcome parameters of prospective observational studies, including preterm neonates at risk of infection in whom peripheral NIRS measurements were performed in combination with venous occlusions. Early neonatal inflammation/infection was diagnosed by clinical signs and laboratory parameters. Peripheral muscle tissue oxygenation index (pTOI) was measured using either NIRO 300 or NIRO 200-NX (both Hamamatsu Photonics, Japan) on the patients' lower legs. Using 20-s venous occlusions, pSvO2 and pFOE were calculated incorporating simultaneous measurements of arterial oxygen saturation (SpO2).ResultsWe analyzed measurements from 226 preterm neonates (median gestational age 33.9 weeks), 64 (28.3%) of whom were diagnosed with early neonatal inflammation/infection. During the first 24 h after birth, pSvO2 (66.9% [62.6–69.2] vs. 69.4% [64.6–72.0]; p = 0.04) and pTOI (68.6% [65.3–71.9] vs. 71.7% [67.3–75.1]; p = 0.02) were lower in those neonates with inflammation/infection, while there was no such difference for measurements between 24–48 and 48–72 h.DiscussionNIRS measurement of pSvO2 and pFOE is feasible and may be utilized for early detection of impaired peripheral oxygen delivery. As pTOI was also significantly lower, this parameter may serve as substitute for diminished regional oxygen supply.

Orthostatic Resiliency During Successive Hypoxic, Hypoxic Orthostatic Challenge: Successful vs. Unsuccessful Cardiovascular and Oxygenation Strategies.

Introduction: Rapid environmental changes, such as successive hypoxic-hypoxic orthostatic challenges (SHHOC) occur in the aerospace environment, and the ability to remain orthostatically resilient (OR) relies upon orchestration of physiological counter-responses. Counter-responses adjusting for hypoxia may conflict with orthostatic responses, and a misorchestration can lead to orthostatic intolerance (OI). The goal of this study was to pinpoint specific cardiovascular and oxygenation factors associated with OR during a simulated SHHOC.Methods: Thirty one men underwent a simulated SHHOC consisting of baseline (P0), normobaric hypoxia (Fi02 = 12%, P1), and max 60 s of hypoxic lower body negative pressure (LBNP, P2). Alongside anthropometric variables, non-invasive cardiovascular, central and peripheral tissue oxygenation parameters, were recorded. OI was defined as hemodynamic collapse during SHHOC. Comparison of anthropometric, cardiovascular, and oxygenation parameters between OR and OI was performed via Student’s t-test. Within groups, a repeated measures ANOVA test with Holm-Sidak post hoc test was performed. Performance diagnostics were performed to assess factors associated with OR/OI (sensitivity, specificity, positive predictive value PPV, and odd’s ratio OR).Results: Only 9/31 were OR, and 22/31 were OI. OR had significantly greater body mass index (BMI), weight, peripheral Sp02, longer R-R Interval (RRI) and lower heart rate (HR) at P0. During P1 OR exhibited significantly higher cardiac index (CI), stroke volume index (SVI), and lower systemic vascular resistance index (SVRI) than OI. Both groups exhibited a significant decrease in cerebral oxygenation (TOIc) with an increase in cerebral deoxygenated hemoglobin (dHbc), while the OI group showed a significant decrease in cerebral oxygenated hemoglobin (02Hbc) and peripheral oxygenation (TOIp) with an increase in peripheral deoxygenated hemoglobin (dHbp). During P2, OR maintained significantly greater CI, systolic, mean, and diastolic pressure (SAP, MAP, DAP), with a shortened RRI compared to the OI group, while central and peripheral oxygenation were not different. Body weight and BMI both showed high sensitivity (0.95), low specificity (0.33), a PPV of 0.78, with an OR of 0.92, and 0.61. P0 RRI showed a sensitivity of 0.95, specificity of 0.22, PPV 0.75, and OR of 0.99. Delta SVI had the highest performance diagnostics during P1 (sensitivity 0.91, specificity 0.44, PPV 0.79, and OR 0.8). Delta SAP had the highest overall performance diagnostics for P2 (sensitivity 0.95, specificity 0.67, PPV 0.87, and OR 0.9).Discussion: Maintaining OR during SHHOC is reliant upon greater BMI, body weight, longer RRI, and lower HR at baseline, while increasing CI and SVI, minimizing peripheral 02 utilization and decreasing SVRI during hypoxia. During hypoxic LBNP, the ability to remain OR is dependent upon maintaining SAP, via CI increases rather than SVRI. Cerebral oxygenation parameters, beyond 02Hbc during P1 did not differ between groups, suggesting that the during acute hypoxia, an increase in cerebral 02 consumption, coupled with increased peripheral 02 utilization does seem to play a role in OI risk during SHHOC. However, cardiovascular factors such as SVI are of more value in assessing OR/OI risk. The results can be used to implement effective aerospace crew physiological monitoring strategies.