Can a Therapeutic Strategy for Hypotension Improve Cerebral Perfusion and Oxygenation in an Experimental Model of Hemorrhagic Shock and Severe Traumatic Brain Injury?

BACKGROUND: Restoration of brain tissue perfusion is a determining factor in the neurological evolution of patients with traumatic brain injury (TBI) and hemorrhagic shock (HS). In a porcine model of HS without neurological damage, it was observed that the use of fluids or vasoactive drugs was effective in restoring brain perfusion; however, only terlipressin promoted restoration of cerebral oxygenation and lower expression of edema and apoptosis markers. It is unclear whether the use of vasopressor drugs is effective and beneficial during situations of TBI. The objective of this study is to compare the effects of resuscitation with saline solution and terlipressin on cerebral perfusion and oxygenation in a model of TBI and HS. METHODS: Thirty-two pigs weighing 20-30 kg were randomly allocated into four groups: control (no treatment), saline (60 ml/kg of 0.9% NaCl), terlipressin (2 mg of terlipressin), and saline plus terlipressin (20 ml/kg of 0.9% NaCl + 2 mg of terlipressin). Brain injury was induced by lateral fluid percussion, and HS was induced through pressure-controlled bleeding, aiming at a mean arterial pressure (MAP) of 40 mmHg. After 30 min of circulatory shock, resuscitation strategies were initiated according to the group. The systemic and cerebral hemodynamic and oxygenation parameters, lactate levels, and hemoglobin levels were evaluated. The data were subjected to analysis of variance for repeated measures. The significance level established for statistical analysis was p < 0.05. RESULTS: The terlipressin and saline plus terlipressin groups showed an increase in MAP that lasted until the end of the experiment (p < 0.05). There was a notable increase in intracranial pressure in all groups after starting treatment for shock. Cerebral perfusion pressure and cerebral oximetry showed no improvement after hemodynamic recovery in any group. The groups that received saline at resuscitation had the lowest hemoglobin concentrations after treatment. CONCLUSIONS: The treatment of hypotension in HS with saline and/or terlipressin cannot restore cerebral perfusion or oxygenation in experimental models of HS and severe TBI. Elevated MAP raises intracranial pressure owing to brain autoregulation dysfunction caused by TBI.

Utility of continuous pulse CO-oximetry for hemoglobin monitoring in pediatric patients with solid organ injuries at level 1 trauma centers: A pilot study.

INTRODUCTION: Hemorrhage is a major cause of preventable death in injured children. Monitoring after admission often requires multiple blood draws, which have been shown to be stressful in pediatric patients. The Rainbow-7 device is a continuous pulse CO-oximeter that measures multiple wavelengths of light, permitting continuous estimation of the total hemoglobin (Hb) level. The purpose of this study was to evaluate the utility of the noninvasive Hb measurement for monitoring pediatric trauma patients admitted with solid organ injury. METHODS: This is a prospective, dual-center, observational trial for patients younger than age 18 years admitted to a Level I pediatric trauma center. Following admission, blood was routinely measured as per current solid organ injury protocols. Noninvasive Hb monitoring was initiated after admission. Time-synced data for Hb levels were compared with that taken using blood draws. Data were evaluated using bivariate correlation, linear regression, and Bland-Altman analysis. RESULTS: Over a 1-year period, 39 patients were enrolled. The mean ± SD age was 11 ± 3.8 years. Forty-six percent (n = 18) of patients were male. The mean ± SD Injury Severity Score was 19 ± 13. The average change in Hb levels between laboratory measurements was -0.34 ± 0.95 g/dL, and the average change in noninvasive Hb was -0.12 ± 1.0 g/dL per measurement. Noninvasive Hb values were significantly correlated with laboratory measurements ( p < 0.001). Trends in laboratory Hb measurements were highly correlated with changes in noninvasive levels ( p < 0.001). Bland-Altman analysis demonstrated similar deviation from the mean throughout the range of Hb values, but the differences between measurements were increased by anemia, African American race, and elevated shock index, pediatric age-adjusted score and Injury Severity Score. CONCLUSION: Noninvasive Hb values demonstrated correlation with measured Hb concentration as isolated measurements and trends, although results were affected by skin pigmentation, shock, and injury severity. Given the rapid availability of results and the lack of requirement of venipuncture, noninvasive Hb monitoring may be a valuable adjunct for pediatric solid organ injury protocols. Further study is required to determine its role in management. LEVEL OF EVIDENCE: Dianostic Test or Criteria; Level III.

Assessment of Anastomotic Viability With Spectroscopic Real-time Oxygen Saturation Measurement in a Porcine Study.

OBJECTIVE: Anastomotic leakage (AL) is a severe complication following intestinal procedures. Intra.Ox™ by ViOptix Inc (Newark, CA, USA) is a novel, FDA-approved spectroscopic device which enables real-time measurement of mixed tissue oxygen saturation (StO2). Using a porcine model, this study explores the correlation between StO2 measurements and AL formation as well as investigates the applicability of Intra.Ox™ in the clinical setting. METHODS: Eleven female swine were divided into 3 groups to explore AL formation in different ischemic conditions. Group 1: 100% mesenteric-vascular ligation, n = 3; Group 2: 50% ligation, n = 5; Group 3: No mesenteric ligation, n = 3. StO2 at the anastomotic line was measured before and after vessel ligation and anastomosis. Measurements were taken at 6 distinct locations along afferent and efferent loops. AL was evaluated on postoperative day 5 by re-laparotomy. RESULTS: AL rate was 100%, 60% and 0% in groups 1, 2 and 3, respectively. Post-anastomotic StO2 in group 1 (22.9 ± 18.5%) and 2 (39.2 ± 20.1%) were significantly lower than in group 3 (53.1 ± 8.3%, p<.0001). Post-anastomotic StO2 readings ≤40% indicated AL potential with 100% sensitivity,+ 80% specificity, positive predictive value of 85.7% and negative predictive value of 100%. CONCLUSION: This study demonstrates the value of Intra.Ox™ in assessing local perfusion and indicate the association between low StO2 and AL by providing accurate, real-time, noninvasive tissue oxygenation measurements at anastomotic sites. Further studies are required to investigate the clinical application of this novel device in intestinal surgery.

A comprehensive review of cerebral oximetry in cardiac surgery.

BACKGROUND: Patients who undergo cardiac surgery are at increased risk of stroke, postoperative cognitive decline, and delirium. These neurocognitive complications have led to increased costs, intensive care unit stays, morbidity, and mortality. As a result, there is a significant push to mitigate any neurological complications in cardiac surgery patients. Near-infrared spectroscopy to measure regional cerebral oxygen saturations has gained consideration due to its noninvasive and user-friendly nature. Cerebral oximetry desaturations during cardiac surgery have been linked to an array of adverse clinical outcomes. However, the most effective intraoperative interventions to protect this vulnerable patient population have yet to be ascertained. AIM OF STUDY: To provide a comprehensive summary of the intraoperative management for cerebral oximetry desaturations during cardiac surgery. The review highlights clinical outcomes from cerebral oximetry use to quantify the importance of identifying cerebral desaturations during cardiac surgery. The review then interrogates possible interventions for cerebral oximetry desaturations in an effort to determine which interventions are most efficacious and to enlighten possible areas for further research. METHODS: A narrative review of randomized controlled trials, observational studies, and systematic reviews with metanalyses was performed through August 2021. RESULTS: There is significant heterogeneity among patient populations for which cerebral oximetry monitoring has been studied in cardiac surgery. Further, the definition of a clinically significant cerebral desaturation and the assessment of neurocognitive outcomes varied substantially across studies. As a result, metanalysis is challenging and few conclusions can be drawn. Cerebral oximetry use during cardiac surgery has not been associated with improvements in neurocognitive outcomes, morbidity, or mortality to date. The evidence to support a particular intervention for an acute desaturation is equivocal. CONCLUSIONS: Future research is needed to quantify a clinically significant cerebral desaturation and to determine which interventions for an acute desaturation effectively improve clinical outcomes.

Sulfohemoglobinemia secundaria a zopiclona. Casos clínicos / Sulfhemoglobinemia secondary to the use of zopiclone. Report of two cases

Sulfhemoglobin (SulfHb) is formed by hemoglobin (Hb) oxidation by sulfur compounds. Sulfhemoglobinemia is mainly associated with drugs or intestinal bacterial overgrowth. Patients present with central cyanosis, an abnormal pulse oximetry and normal arterial oxygen partial pressure. These features are shared with methemoglobinemia (MetHb) whose diagnosis requires an arterial co-oximetry. Depending on the device used, SulfHb may produce interference with this technique. We report two females aged 31 and 43 years, consulting at the emergency room with cyanosis. Both had a history of acute and chronic, high dose zopiclone ingestion. Pulse oximetry showed desaturation but with normal arterial oxygen partial pressure. Cardiac and pulmonary diseases were ruled out. Co-oximetry in two different analyzers showed interference or normal MetHb percentages. No other complications ensued, and cyanosis decreased over days. Since MetHb was discarded among other causes of cyanosis in a compatible clinical context, the diagnosis of sulfhemoglobinemia was made. The confirmatory method is not available in Chile. The presence of SulfHb is difficult to diagnose, confirmatory tests are not readily available, and it frequently interferes with arterial co-oximetry. This is attributed to a similar absorbance peak of both pigments in arterial blood. Venous co-oximetry can be useful in this context. SulfHb is a self-limited condition in most cases, however it must be differentiated from methemoglobinemia to avoid inappropriate treatments like methylene blue.

The outcomes of using high oxygen concentration in pediatric patients.

Oxygen reserve index, available as part of Masimo Rainbow SET pulse oximetry, is a noninvasive and continuous variable intended to provide insight into a patient's oxygen status in the moderate hyperoxic range (PaO2 > 100 and ≤ 200 mm Hg), defined as a patient's oxygen "reserve". When used in conjunction with pulse oximetry, ORi extends the knowledge on a patient's oxygen status providing clinically important information helping to prevent hyperoxemia and hypoxemia. There are limited data on patients undergoing craniosynostosis surgery. Our primary goal was to evaluate the effects of different concentrations of inspiratory oxygen (FiO2) on patient oxygenation status by monitoring ORi. Thirty patients scheduled for craniosynostosis were included in this observational cohort study. Patients were randomized into two equal groups: Group 1 received a fraction of inspired oxygen of 0.8 and group 2 received a FiO2 of 0.6 during induction of anaesthesia. In addition to standard haemodynamic variables with ORi were recorded at baseline 1 min, 5 min, 60 min, and 120 min after intubation. Postoperative complications, length of stay in the intensive care unit and hospital were recorded. In total, 14 patients were evaluated in each group. Gender, age, BMI, ASA scores were similar between groups (p > 0.05). In Group 1, ORi values were significantly higher when compared to group 2 at baseline (0.86 ± 0.21 vs 0.45 ± 0.32, p = 0.001), one minute (0.61 ± 0.24 vs 0.27 ± 0.21, p = 0.001), and 5 min (0.34 ± 0.31 vs 0.10 ± 0.13, p = 0.033). High inspired oxygen concentration during induction of anesthesia in pediatric patients is associated with higher levels of ORi. Therefore, ORi may provide the means to safely reduce the inspired oxygen fraction during inhalational induction in paediatric patients.

Using India Ink as a Sensor for Oximetry: Evidence of its Safety as a Medical Device.

Clinical EPR spectroscopy is emerging as an important modality, with the potential to be used in standard clinical practice to determine the extent of hypoxia in tissues and whether hypoxic tissues respond to breathing enriched oxygen during therapy. Oximetry can provide important information useful for prognosis and to improve patient outcomes. EPR oximetry has many potential advantages over other ways to measure oxygen in tissues, including directly measuring oxygen in tissues and being particularly sensitive to low oxygen, repeatable, and non-invasive after an initial injection of the EPR-sensing material is placed in the tumor. The most immediately available oxygen sensor is India ink, where two classes of carbon (carbon black and charcoal) have been identified as having acceptable paramagnetic properties for oximetry. While India ink has a long history of safe use in tattoos, a systematic research search regarding its safety for marking tissues for medical uses and an examination of the evidence that differentiates between ink based on charcoal or carbon black has not been conducted. METHODS: Using systematic literature search techniques, we searched the PubMed and Food and Drug Administration databases, finding ~1000 publications reporting on adverse events associated with India/carbon based inks. The detailed review of outcomes was based on studies involving >16 patients, where the ink was identifiable as carbon black or charcoal. RESULTS: Fifty-six studies met these criteria. There were few reports of complications other than transient and usually mild discomfort and bleeding at injection, and there was no difference in charcoal vs. carbon black India ink. CONCLUSIONS: India ink was generally well tolerated by patients and physicians reported that it was easy to use in practice and used few resources. The risk is low enough to justify its use as an oxygen sensor in clinical practice.

Methylene blue and parathyroid adenoma localization: Three new cases of a rare cutaneous complication.

Methylene blue has been safely used for the localization of parathyroid glands during parathyroidectomy, and only a few adverse effects have been documented. Methylene blue administration as a cause of pulse-oximetry-related skin injury is extremely rare. We describe 2 such cases in patients who developed a blister on the second digit at the pulse oximetry site after an uncomplicated excision of a parathyroid adenoma. In another case, a patient became bradycardic intraoperatively; she was successfully resuscitated, but she incurred a second-degree burn at the pulse oximetry site. In all 3 cases, the burns resolved with local wound care. We publish this report to alert surgeons and anesthesiologists to the risk of skin complications with the use of high-dose intraoperative methylene blue.

Management of pulse oximeter probe-induced finger injuries in children: report of two consecutive cases and review of the literature.

Pulse oximetry is a standard noninvasive procedure for monitoring arterial oxygen saturation. Finger injuries related to pulse oximeter use have been reported as chemical or thermal burns, sun-tanning, pressure erosion, sensory loss, and gangrene. The mechanisms of these complications have not been definitively explained; but pressure ischemia, prolonged use, overheating of the probe, inappropriate use of the probe, and short circuiting are considered to be the main factors. We describe 2 cases of pulse oximeter probe-induced finger injuries, propose the possible mechanisms and factors related to the injury, and discuss the management.

[Experimental study of the effects of transesophageal oxygen saturation monitoring on the safety of esophageal mucosa].

The present paper was aimed to study the security of burning during the continuous monitoring of transesophageal arterial oxygen saturation. 20 rabbits were randomly divided into two groups: control group and high-frequency electrotome group. All rabbits were implanted with the oxygen saturation detection probes into the lower esophageal after anesthesia. The probes were made up with two light-emitting diode (LED) and then connected with oxygen saturation sensor to monitoring for 2h and 6h, respectively. We then intercepted two luminous points as esophageal specimens and dist the esophageal tissue detection device headend 1cm gastric side esophageal specimens (self-contr01) after monitoring, and carried out pathological examination. The pathological results of the LED-1, LED-2 esophageal biopsy and self-control section were mucous integrity, submucosal mildedema, hyperemia, a small number of lymphocytes and mononuclear cell infiltration. All the score of the esophageal tissue histologic was 2. The results showed that montioring the SteO2 not more than 6h was safe with montiored using a matching of oxygen saturation sensor and monitoring esophageal arterial oxygen saturation.

Effective standards and regulatory tools for respiratory gas monitors and pulse oximeters: the role of the engineer and clinician.

Developing safe and effective medical devices involves understanding the hazardous situations that can arise in clinical practice and implementing appropriate risk control measures. The hazardous situations may have their roots in the design or in the use of the device. Risk control measures may be engineering or clinically based. A multidisciplinary team of engineers and clinicians is needed to fully identify and assess the risks and implement and evaluate the effectiveness of the control measures. In this paper, I use three issues, calibration/accuracy, response time, and protective measures/alarms, to highlight the contributions of these groups. This important information is captured in standards and regulatory tools to control risk for respiratory gas monitors and pulse oximeters. This paper begins with a discussion of the framework of safety, explaining how voluntary standards and regulatory tools work. The discussion is followed by an examination of how engineering and clinical knowledge are used to support the assurance of safety.

Continuous SvO2 measurement in infants undergoing congenital heart surgery--first clinical experiences with a new fiberoptic probe.

BACKGROUND: SvO2-guided therapy, using fiberoptic oximetric catheters can help to improve the outcome after complex congenital heart surgery especially in infants undergoing the Stage 1-Norwood-Procedure. So far, fiberoptic catheters have to be placed transthoracically by the surgeon into the vena cava or the pulmonary artery putting the infant at an additional risk of bleeding at the time of catheter removal. METHODS: We used a new percutaneously applicable fiberoptic probe for continuous monitoring of central venous saturation in three infants undergoing modifications of the Stage 1-Norwood-Procedure (reconstruction of the aortic arch), two in combination with a bidirectional cavopulmonary connection (Glenn shunt), the third with reconstruction of the pulmonary arteries (biventricular repair). The approved clinical monitoring system consisted of a small (2 F) fiberoptic probe and a bed-side-monitor. The probe was inserted via the routine central venous access for such a case. RESULTS: Continuous SvO2 measurement is feasible in infants using the CeVOX system in combination with routine central venous access, and the advantages of continuous monitoring are discussed. CONCLUSIONS: We believe that compared with transthoracically inserted oximetric catheter, the presented percutaneous technique avoids additional risks at the time of catheter removal (i.e. bleeding) and has become part of our standard management.

Temperature threshold for burn injury: an oximeter safety study.

Pulse oximeters have become essential devices for evaluating and monitoring patient oxygenation. The probe emits a small amount of heat into the skin in the process of signal detection. Regulations set by the Food and Drug Administration currently limit the maximum allowable temperature of an oximeter probe to 41 degrees C. As a result of the prolonged exposure of extremities to these devices, we sought to determine the actual temperature threshold for burn injury in patients. Eighteen patients undergoing surgery for removal of redundant skin (abdominoplasty, breast reduction) consented to the application of a temperature-controlled custom probe with four light-emitting diodes that had temperatures set randomly at the expected threshold for burn injury (42.5 degrees C, 43 degrees C, 43.5 degrees C, and 44 degrees C). The probe was left in place for 8 hours (or less if significant pain was noted). The sites covered by the probes were then checked for signs of injury. On the next day, the redundant skin was removed as a scheduled procedure, and histopathology was performed to detect the extent of burn injury. The study was approved by the local institutional research board. Two patients were excluded because of technical problems with the probe, one of whom had the probe turned off because of pain. The only observed sign of injury was either erythema or a superficial blister that was usually unobservable or slightly red at operation. These subtle signs of a burn were noted in one patient at 43 degrees C, four at 43.5 degrees C, and nine at 44 degrees C. No burns were noted in two patients. Minimal or no signs of injury frequently were noted by histopathology. Pulse oximeter probes are safe up to a temperature of 43 degrees C for at least 8 hours in well-perfused skin. Above that temperature, there is a risk of burn injury. Performing temperature threshold tests in redundant skin that is planned for excision is a potential method for testing the safety of devices or materials.

Retinopathy of prematurity and pulse oximetry: a national survey of recent practices.

OBJECTIVE: To determine if practices related to the use of pulse oximetry in the first 2 weeks following birth and after 2 weeks of age have a relationship to the rate of retinopathy of prematurity (ROP) and retinal ablation surgery in infants < or =1500 g. STUDY DESIGN: A questionnaire was mailed in July 2001 to 318 neonatal intensive care units (NICUs) in the United States and information was collected regarding SpO2 guidelines and the rate of both severe ROP and retinal ablation surgery. RESULTS: A total of 142 surveys were returned (45%). In all, 87% of the NICUs had SpO2 guidelines, and 60% of these centers maintained a different range of SpO2 for infants < or = or >2 weeks of age. The range of SpO2 was 82 to 100% with an average minimum (min) and maximum (max) of 89 and 95%, respectively. In the NICUs with an SpO2 max of >98% in the first 2 weeks following birth, the rate of retinal ablation surgery was 5.5 vs 3% in those units with a max SpO2 >98% (p<0.05). After 2 weeks of age, the rate of retinal ablation surgery was 3.3% when max SpO2 was >92 vs 1.3% when the max SpO2 was < or =92% (p<0.00001). The rate of > or =stage 3 ROP after 2 weeks of age was 5.5% when max SpO2 was >92 vs 2.4% when max SpO2 was < or =92% (p<0.0005). CONCLUSION: NICUs in the US today have a wide range of SpO2 guidelines. The results of this survey show a "gradient of risk" towards less retinal ablation surgery when the max SpO2 is <98% in the first 2 weeks following birth (p<0.05). There was a statistically significant lower rate of > or =stage 3 ROP and retinal ablation surgery when the max SpO2 was < or =92% after the first 2 weeks of age. A randomized, controlled trial is needed to establish a safe upper limit of SpO2 in the premature infant at risk for developing ROP.

Arterial blood gas and pulse oximetry in initial management of patients with community-acquired pneumonia.

OBJECTIVE: To identify the factors associated with the use of arterial blood gas (ABG) and pulse oximetry (PO) in the initial management of patients with community-acquired pneumonia (CAP) and arterial hypoxemia at presentation. PARTICIPANTS: A total of 944 outpatients and 1,332 inpatients with clinical and radiographic evidence of CAP prospectively enrolled from 5 study sites in the United States and Canada. ANALYSES: Separate multivariate logistic regression analyses were used to 1) compare measurement of ABG and PO within 48 hours of presentation across sites while controlling for patient differences, and 2) identify factors associated with arterial hypoxemia (PaO2 <60 mm Hg or SaO2 <90% for non-African Americans and <92% for African Americans) while breathing room air. RESULTS: Range of ABG use by site was from 0% to 6.4% (P =.06) for outpatients and from 49.2% to 77.3% for inpatients (P <.001), while PO use ranged from 9.4% to 57.8% for outpatients (P <.001) and from 47.9% to 85.1% for inpatients (P <.001). Differences among sites remained after controlling for patient demographic characteristics, comorbidity, and illness severity. In patients with 1 or more measurements of oxygenation at presentation, hypoxemia was independently associated with 6 risk factors: age >30 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.7 to 5.9), chronic obstructive pulmonary disease (OR, 1.9; 95% CI, 1.4 to 2.6), congestive heart failure (OR, 1.5; 95% CI, 1.0 to 2.1), respiratory rate >24 per minute (OR, 2.3; 95% CI, 1.8 to 3.0), altered mental status (OR, 1.6; 95% CI, 1.1 to 2.3), and chest radiographic infiltrate involving >1 lobe (OR, 2.2; 95% CI, 1.7 to 2.9). The prevalence of hypoxemia among those tested ranged from 13% for inpatients with no risk factors to 54.6% for inpatients with > or =3 risk factors. Of the 210 outpatients who had > or =2 of these risk factors, only 64 (30.5%) had either an ABG or PO performed. In the 48 outpatients tested without supplemental O2 with > or =2 risk factors 8.3% were hypoxemic. CONCLUSIONS: In the initial management of CAP, use of ABG and PO varied widely across sites. Increasing the assessment of arterial oxygenation among patients with CAP is likely to increase the detection of arterial hypoxemia, particularly among outpatients.

Pulse oximeter-associated toe injuries in a premature neonate: a case report.

Pulse oximetry is noninvasive and widely used in the intensive care unit and during surgery. Complications associated with the use of pulse oximetry have been reported, including burns, pressure erosion, skin necrosis and digital sensory loss. The causes of these complications may be due to the incompatibilities between the probes and the monitors used from different companies, pressure duration for too long on a single skin site or overheating induced by a short circuit of the probe cable. We report a 940-g premature infant who had severe pulse oximetry-associated injury to the oximetry site. This may have been due to the infant's susceptibility to injury resulting from his critical condition, including low cardiac output, poor peripheral circulation and poor heat dissemination. Our experience shows that, when pulse oximetry is used, especially in critically ill, premature infants, frequent checking of the sensor and the site where the sensor is applied is required to avoid burn injury or pressure erosion of the skin.