Well-being and cerebral oxygen saturation during acute heart failure in humans

Preoperative cerebral oxygenation in high-risk noncardiac surgical patients: an observational study on postoperative mortality and complications

Near Infrared Spectroscopy (NIRS) has become widely accepted to evaluate regional cerebral oxygen saturation (rScO2), potentially acting as a surrogate parameter of reduced cerebral oxygen delivery or increased consumption. Low preoperative rScO2 is associated with increased postoperative complications after cardiac surgery. However, its universal potential in pre-anesthesia risk assessment remains unclear. Therefore, we investigated whether low preoperative rScO2 is indicative of postoperative complications and associated with poor outcomes in noncardiac surgical patients. We prospectively enrolled 130 patients undergoing high-risk noncardiac surgery. During pre-anesthesia evaluation, baseline rScO2 was recorded with and without oxygen supplementation. The primary endpoint was 30-day mortality, while secondary endpoints were postoperative myocardial injury, respiratory complications, and renal failure. We further evaluated the impact of body position and preoperative hemoglobin (Hb) concentration on rScO2. Of the initially enrolled 130 patients, 126 remained for final analysis. Six (4.76%) patients died within 30 postoperative days. 95 (75.4%) patients were admitted to the ICU. 32 (25.4%) patients suffered from major postoperative complications. There was no significant association between rScO2 and 30-day mortality or secondary endpoints. Oxygen supplementation induced a significant increase of rScO2. Furthermore, Hb concentration correlated with rScO2 values and body position affected rScO2. No significant association between rScO2 values and NYHA, LVEF, or MET classes were observed. Preoperative rScO2 is not associated with postoperative complications in patients undergoing high-risk noncardiac surgery. We speculate that the discriminatory power of NIRS is insufficient due to individual variability of rScO2 values and confounding factors.

Cerebral oximetry: a developing tool for monitoring cerebral oxygenation during cardiopulmonary resuscitation

Despite improvements in cardiopulmonary resuscitation (CPR), survival and neurologic recovery after cardiac arrest remain very poor because of the impact of severe ischemia and subsequent reperfusion injury. As the likelihood of survival and favorable neurologic outcome decreases with increasing severity of ischemia during CPR, developing methods to measure the magnitude of ischemia during resuscitation, particularly cerebral ischemia, is critical for improving overall outcomes. Cerebral oximetry, which measures regional cerebral oxygen saturation (rSO₂ ) by near-infrared spectroscopy, has emerged as a potentially beneficial marker of cerebral ischemia during CPR. In numerous preclinical and clinical studies, higher rSO₂ during CPR has been associated with improved cardiac arrest survival and neurologic outcome. In this narrative review, we summarize the scientific rationale and validation of cerebral oximetry across populations and pathophysiologic states, discuss the evidence surrounding its use to predict return of spontaneous circulation, rearrest, and neurologic outcome, and provide suggestions for incorporation of cerebral oximetry into CPR practice.

Effect of phenylephrine on cerebral oxygen saturation and cardiac output in adults when used to treat intraoperative hypotension: a systematic review

OBJECTIVE

The objective of this review was to examine the effect of phenylephrine on cerebral oxygen saturation, cardiac output, and middle cerebral artery blood flow velocity when used to treat intraoperative hypotension.

INTRODUCTION

While the etiology of postoperative cognitive dysfunction in adults following surgery is likely multifactorial, intraoperative cerebral hypoperfusion is a commonly proposed mechanism. Research evidence and expert opinion are emerging that suggest phenylephrine adversely affects cerebral oxygen saturation and may also adversely affect cerebral perfusion via a reduction in cardiac output or cerebral vascular vasoconstriction. The administration of phenylephrine to treat intraoperative hypotension is common anesthesia practice, despite a lack of evidence to show it improves cerebral perfusion. Therefore, a systematic review of the effect of phenylephrine on cerebral hemodynamics has significant implications for anesthesia practice and future research.

INCLUSION CRITERIA

Studies of adults 18 years and over undergoing elective, non-neurosurgical procedures involving anesthesia were included. In these studies, participants received phenylephrine to treat intraoperative hypotension. The effect of phenylephrine on cerebral oxygen saturation, cardiac output, or middle cerebral artery blood flow velocity was measured.

METHODS

Key information sources searched included MEDLINE (Ovid), Embase, CINAHL (EBSCO), and Google Scholar. The scope of the search was limited to English-language studies published from 1999 through 2017. The recommended JBI approach to critical appraisal, study selection, data extraction, and data synthesis were used.

RESULTS

This systematic review found that phenylephrine consistently decreased cerebral oxygen saturation values despite simultaneously increasing mean arterial pressure to normal range. Results also found that ephedrine and dopamine were superior to phenylephrine in maintaining or increasing values. Phenylephrine was found to be similar to vasopressin in the extent to which both decreased cerebral oxygen saturation values. Results also showed that phenylephrine resulted in statistically significant declines in cardiac output, or failed to improve abnormally low preintervention values. The effect of phenylephrine on middle cerebral artery blood flow velocity was only measured in one study and showed that phenylephrine increased flow velocity by about 20%. Statistical pooling of the study results was not possible due to the gross variation in how the intervention was administered and how effect was measured.

CONCLUSIONS

This review found that phenylephrine administration resulted in declines in cerebral oxygen saturation and cardiac output. However, the research studies were ineffective in informing phenylephrine's mechanism of action or its impact on postoperative cognitive function.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO (CRD42018100740).

Difference in Cerebral and Hepatic Oxygenation in Response to Ultrafiltration in a Hemodialysis Patient With Congestive Heart Failure

Near-infrared spectroscopy has been used to measure regional oxygen saturation (rSO₂), and intradialytic tissue rSO₂ measurements have been playing an important role in evaluating changes in tissue oxygenation in various clinical settings of hemodialysis (HD) therapy.However, few reports have described changes in hepatic oxygenation associated with body fluid management in overhydrated HD patients. We herein report an HD patient with congestive heart failure (CHF) that had improved systemic and tissue oxygenation, including in the brain and liver, during HD with ultrafiltration. A 73-year-old man undergoing HD was admitted to our hospital with CHF. After admission, HD with ultrafiltration was performed to adequately manage his body fluid excess. Because of deterioration of systemic oxygenation on admission, we monitored his percutaneous arterial oxygen saturation (SpO₂) using a pulse oximeter and regional oxygen saturation (rSO₂) in the brain and liver using an INVOS 5100c oxygen saturation monitor during HD. At HD initiation, his cerebral and hepatic rSO₂ levels were relatively low, at 43.2% and 34.1%, respectively, in addition to the SpO₂ of 88%. During HD with ultrafiltration, systemic oxygenation evaluated by SpO₂ and tissue oxygenation by cerebral and hepatic rSO₂ improved. Interestingly, the hepatic rSO₂ ratio, defined as the ratio of rSO₂ values at t (min) during HD and the initial rSO₂ value before HD, increased larger than the cerebral rSO₂ ratio during HD. After the adjustment of body fluid condition under the maintained SpO₂ values, we confirmed the hepatic and cerebral SO₂ ratio again during HD, and these two values changed nearly in the same manner. Throughout our experience, in this case, we confirmed a remarkable increase in hepatic rSO₂ ratio relative to cerebral rSO₂ ratio under a CHF status during HD, and these differences disappeared after the adjustment of the body fluid status.

The response of a standardized fluid challenge during cardiac surgery on cerebral oxygen saturation measured with near-infrared spectroscopy

Near infrared spectroscopy (NIRS) has been used to evaluate regional cerebral tissue oxygen saturation (ScO₂) during the last decades. Perioperative management algorithms advocate to maintain ScO₂, by maintaining or increasing cardiac output (CO), e.g. with fluid infusion. We hypothesized that ScO₂ would increase in responders to a standardized fluid challenge (FC) and that the relative changes in CO and ScO₂ would correlate. This study is a retrospective substudy of the FLuid Responsiveness Prediction Using Extra Systoles (FLEX) trial. In the FLEX trial, patients were administered two standardized FCs (5 mL/kg ideal body weight each) during cardiac surgery. NIRS monitoring was used during the intraoperative period and CO was monitored continuously. Patients were considered responders if stroke volume increased more than 10% following FC. Datasets from 29 non-responders and 27 responders to FC were available for analysis. Relative changes of ScO₂ did not change significantly in non-responders (mean difference - 0.3% ± 2.3%, p = 0.534) or in fluid responders (mean difference 1.6% ± 4.6%, p = 0.088). Relative changes in CO and ScO₂ correlated significantly, p = 0.027. Increasing CO by fluid did not change cerebral oxygenation. Despite this, relative changes in CO correlated to relative changes in ScO₂. However, the clinical impact of the present observations is unclear, and the results must be interpreted with caution.Trial registration:http://ClinicalTrial.gov identifier for main study (FLuid Responsiveness Prediction Using Extra Systoles-FLEX): NCT03002129.

Comparison of the Effects of Desflurane and Sevoflurane on Cerebral Oxygen Saturation in Patients Undergoing Thyroidectomy: A Randomised Controlled Clinical Study

Objective

The commonly performed sitting position with head extended during thyroidectomy has been shown to cause adverse effects on cerebral regional oxygen saturation (CrSO2). Therefore, the present study aimed to investigate the effects of two well-known anaesthetic agents, desflurane and sevoflurane, on CrSO2 in patients undergoing thyroidectomy in the semi-sitting position by near-infra-red spectroscopy monitoring.

Methods

The study included 60 patients aged 18-65 years, with an American Society of Anesthesiologists (ASA) physical status classification score I-III, who underwent elective thyroidectomy in the semi-sitting position. The patients were randomly divided into two groups, depending on the anaesthetic agent administered: (1) sevoflurane group (Group S; n=30) and (2) desflurane group (Group D; n=30). After intubation, the patients were placed in a 45-degree semi-sitting position. Vital signs and the CrSO2 levels in both hemispheres were recorded both pre-induction and at the induction minute 1, post-intubation, post-positioning, every 5 minutes intraoperatively and in the case of sudden changes.

Results

No significant difference was found between the groups in terms of age, height, body weight, the ASA score, operative time and left- and right-hemisphere CrSO2 (p>0.05). Moreover, the two groups were statistically similar to each other with regard to peripheral capillary oxygen saturation, heart rate, systolic and diastolic blood pressure, mean artery pressure and end-tidal CO₂ (ETCO₂) levels.

Conclusion

Desflurane and sevoflurane had similar effects in the preservation of CrSO2 in patients undergoing thyroidectomy in the semi-sitting position.

Factors responsible for cerebral hypoxia in hemodialysis population

Brain tissue oxygenation (rSO(2)) measured by near-infrared spectroscopy (NIRS) is lower in hemodialysis patients than in the healthy population and is associated with cognitive dysfunction. The involved mechanisms are not known. We conducted this study to identify the factors that influence the rSO2 values in end-stage renal disease (ESRD) patients and to describe rSO2 changes during hemodialysis. We included a cohort of ESRD patients hemodialyzed in our institution. We recorded rSO2 using INVOS 5100C oximetry system (Medtronic, Essex, U.K.) and analyzed changes in basic laboratory values and hemodynamic fluctuations. Baseline rSO2 was lower in patients with heart failure (45.2±8.3 % vs. 54.1±7.8 %, p=0.006) and was significantly linked to higher red cell distribution width (RDW) (r=-0.53, p?0.001) and higher BNP level (r=-0.45, p=0.01). The rSO(2) value decreased in first 15 min of hemodialysis, this decrease correlated with drop in white blood count during the same period (r=0.43, p=0.02 in 10 min, r=0.43, p=0.02 in 20 min). Lower rSO(2) values in patients with heart failure and higher RDW suggest that hemodynamic instability combined with vascular changes probably leads to worse cerebral oxygenation in these patients. Decrease of rSO(2) in 15th minute of hemodialysis accompanied with a significant drop in leukocyte count could be explained by complement activation.

Cerebral oximetry during preoperative resuscitation in elderly patients with hip fracture: a prospective observational study

This study explores the association between postadmission and intraoperative cerebral oxygenation (ScO₂), reflecting systemic perfusion, and postoperative mortality and delirium. Forty elderly (age > 65 years) patients with hip fractures were included in this prospective observational study. The ScO₂ was determined using near-infrared spectroscopy at initial resuscitation after patients were admitted to the hospital and during surgery. Postoperative delirium was assessed up to seven days after surgery using the memorial delirium assessment scale and the confusion assessment method. Ten patients (25%) developed postoperative delirium within the first seven postoperative days. At initial resuscitation ScO₂ was lower in patients that later developed delirium, but the difference was not significant (p = 0.331). Intraoperative ScO₂ values remained similar in the two groups. Mortality regardless of cause was 10% (4 out of 40 patients) after 30 days. At initial resuscitation ScO₂ was significant lower in the mortality group than in the surviving group (p = 0.042), and the ScO₂ nadir values were also significant lower (p = 0.047). Low ScO₂ during initial resuscitation (defined as ScO₂ < 55 for a minimum of two consecutive minutes) was also significantly associated with 30-day mortality (p = 0.015). There were no associations between low blood pressure and postoperative delirium or 30-day mortality. We found that low preoperative ScO₂ was better associated with 30-day all-cause mortality in elderly patients undergoing surgery for hip fracture than blood pressure measurements. Future studies in preoperative resuscitation of hip fracture patients should focus on perfusion measures as opposed to conventional haemodynamic.

Cerebral and Limb Tissue Oxygenation During Peripheral Venoarterial Extracorporeal Life Support

Femoral access in extracorporeal life support (ECLS) has been associated with regional variations in arterial oxygen saturation, potentially predisposing the patient to ischemic tissue damage. Current monitoring techniques, however, are limited to intermittent bedside evaluation of capillary refill among other factors. The aim of this study was to assess whether cerebral and limb regional tissue oxygen saturation (rSO₂) values reflect changes in various patient-related parameters during venoarterial ECLS (VA-ECLS). This retrospective observational study included adults assisted by femorofemoral VA-ECLS. Bifrontal cerebral and bilateral limb tissue oximetry was performed for the entire duration of support. Hemodynamic data were analyzed parallel to cerebral and limb rSO₂. A total of 23 patients were included with a median ECLS duration of 5 [1-20] days. Cardiac arrhythmias were observed in 12 patients, which was associated with a decreased mean rSO₂ from 61%±11% to 51%±10% during atrial fibrillation and 67%±9% to 58%±10% during ventricular fibrillation (P<0.001 for both). A presumably sudden increase in cardiac output due to myocardial recovery (n=8) resulted in a significant decrease in mean cerebral rSO₂ from 73%±7% to 54%±6% and from 69%±9% to 53%±8% for the left and right cerebral hemisphere, respectively (P=0.012 for both hemispheres). Also, right radial artery partial gas pressure for oxygen decreased from 15.6±2.8 to 8.3±1.9 kPa (P=0.028). No differences were found in cerebral desaturation episodes between patients with and without neurologic complications. In six patients, limb rSO₂ increased from on average 29.3±2.7 to 64.0±5.1 following insertion of a distal cannula in the femoral artery (P=0.027). Likewise, restoration of flow in a clotted distal cannula inserted in the femoral artery was necessary in four cases and resulted in increased limb rSO₂ from 31.3±0.8 to 79.5±9.0; P=0.068. Non-invasive tissue oximetry adequately reflects events influencing cerebral and limb perfusion and can aid in monitoring tissue perfusion in patients assisted by ECLS.

Intraoperative Cerebral Perfusion Disturbances During Transcatheter Aortic Valve Replacement

BACKGROUND

Transcatheter aortic valve replacement entails profound and unavoidable hemodynamic perturbations that may contribute to the neurological injury associated with the procedure.

METHODS

Thirty-one patients were monitored with cerebral oximetry as a surrogate marker of perfusion while undergoing transcatheter aortic valve replacement via a transfemoral approach under general anesthesia to detect intraoperative hypoperfusion insult. Serial neurologic, cognitive, and cerebral magnetic resonance imaging assessments were administered to objectively quantify perioperative neurologic injury and ascertain any association with significant cerebral oximetry disturbances.

RESULTS

Cerebral oximetry reacted promptly to rapid ventricular pacing with significant cerebral desaturation, relative to baseline, of greater than 12% and greater than 20% in 12 of 31 (68%) and 9 of 31 (29%) patients, respectively; or to an absolute measurement of less than 50% in 10 of 31 (33%) patients. Hyperemia occurred immediately following relief of aortic stenosis exceeding baseline by greater than 10% and greater than 20% in 14 of 31 (45%) and 5 of 31 (16%) patients. Postoperative cognitive dysfunction was evident in 3 of 31 (10%) patients and new magnetic resonance imaging-defined ischemic lesions were seen in 17 of 28 (61%) patients. No patient experienced clinically apparent stroke.

CONCLUSIONS

Cerebral oximetry reacted promptly to rapid ventricular pacing with significant desaturation and hyperemia a common occurrence. However, no association between this intraoperative insult and objective neurologic injury was detected.

Cerebral Oximetry for Cardiac and Vascular Surgery

The technology of transcranial near-infrared spectroscopy (NIRS) for the measurement of cerebral oxygen balance was introduced 25 years ago. Until very recently, there has been only occasional interest in its use during surgical monitoring. Now, however, substantial technologic advances and numerous clinical studies have, at least partly, succeeded in overcoming long-standing and widespread misunderstanding and skepticism regarding its value. Our goals are to clarify common misconceptions about near-infrared spectroscopy and acquaint the reader with the substantial literature that now supports cerebral oximetric monitoring in cardiac and major vascular surgery.

Brain natriuretic peptide (BNP) may play a major role in risk stratification based on cerebral oxygen saturation by near-infrared spectroscopy in patients undergoing major cardiovascular surgery

Purpose

A previous study reported that low baseline cerebral oxygen saturation (ScO₂) (≤50%) measured with near-infrared spectroscopy was predictive of poor clinical outcomes after cardiac surgery. However, such findings have not been reconfirmed by others. We conducted the current study to evaluate whether the previous findings would be reproducible, and to explore mechanisms underlying the ScO₂-based outcome prediction.

Methods

We retrospectively investigated 573 consecutive patients, aged 20 to 91 (mean ± standard deviation, 67.1 ± 12.8) years, who underwent major cardiovascular surgery. Preanesthetic baseline ScO₂, lowest intraoperative ScO₂, various clinical variables, and hospital mortality were examined.

Results

Bivariate regression analyses revealed that baseline ScO₂ correlated significantly with plasma brain natriuretic peptide concentration (BNP), hemoglobin concentration (Hgb), estimated glomerular filtration rate (eGFR), and left ventricular ejection fraction (LVEF) (p < 0.0001 for each). Baseline ScO₂ correlated with BNP in an exponential manner, and BNP was the most significant factor influencing ScO₂. Logistic regression analyses revealed that baseline and lowest intraoperative ScO₂ values, but not relative ScO₂ decrements, were significantly associated with hospital mortality (p < 0.05), independent of the EuroSCORE (p < 0.01). Receiver operating curve analysis of ScO₂ values and hospital mortality revealed an area under the curve (AUC) of 0.715 (p < 0.01) and a cutoff value of ≤50.5% for the baseline and ScO₂, and an AUC of 0.718 (p < 0.05) and a cutoff value of ≤35% for the lowest intraoperative ScO₂. Low baseline ScO₂ (≤50%) was associated with increases in intubation time, intensive care unit stay, hospital stay, and hospital mortality.

Conclusion

Baseline ScO₂ was reflective of severity of systemic comorbidities and was predictive of clinical outcomes after major cardiovascular surgery. ScO₂ correlated most significantly with BNP in an exponential manner, suggesting that BNP plays a major role in the ScO₂-based outcome prediction.

Cardiopulmonary Interactions

OBJECTIVES

The objectives of this review are to discuss the mechanisms by which respiration impacts cardiovascular function and vice versa, with an emphasis on the impact of these interactions in pediatric cardiac critical care.

DATA SOURCE

A search of MEDLINE was conducted using PubMed.

CONCLUSIONS

In the presence of underlying cardiac and respiratory disease, the interplay between these two systems is significant and plays a pivotal role in the pathophysiology of acute and chronic phases of a wide spectrum of diseases. An understanding of these relationships is essential to optimizing the care of critically ill patients.

[Near-infrared spectroscopy during cardiopulmonary resuscitation and mechanical circulatory support: From the operating room to the intensive care unit]

BACKGROUND

Near infrared spectroscopy (NIRS) allows continuous measurement of cerebral regional oxygen saturation (rSO2). It is a weighted saturation value derived from approximately 70-75 % venous, 20-25 % arterial and 2.5-5 % capillary blood. In contrast to pulse oximetry, NIRS is independent of pulsatile flow. Therefore, it is also applicable during extracorporeal circulation, cardiopulmonary resuscitation (CPR), and hypothermia.

OBJECTIVES

The purpose of this work is to describe the application of cerebral and somatic NIRS in cardiology and cardiac surgery patients in the operation room, during and after CPR, and during the intensive care unit stay.

MATERIALS AND METHODS

This article is based on peer-reviewed literature from PubMed.

RESULTS

Interventions based on decline of cerebral NIRS values during on-pump cardiac surgery can reduce major organ morbidity and mortality; however, the appearance of a postoperative cognitive dysfunction is scarcely influenced. Persisting of low cerebral oximetry values during resuscitation is a marker for not achieving return of spontaneous circulation under normothermia. NIRS is an additional method for monitoring that can be used during extracorporeal circulation.

CONCLUSION

NIRS is a rapidly available, user-friendly, and noninvasive method for continuous measurement of rSO2. NIRS provides additional information about tissue oxygenation especially during resuscitation and extracorporeal circulatory assist support. Recommendations concerning the use of NIRS for standard monitoring during resuscitation and mechanical circulatory support are not currently available. Further studies are required to show if use of NIRS can reduce pulse control and hands-off times during resuscitation and if use of NIRS can improve outcome after CPR and mechanical circulatory support.

Innovative approaches in the perioperative care of the cardiac surgical patient in the operating room and intensive care unit

Perioperative care for cardiac surgery is undergoing rapid evolution. Many of the changes involve the application of novel technologies to tackle common challenges in optimizing perioperative management. Herein, we illustrate recent advances in perioperative management by focusing on a number of novel components that we judge to be particularly important. These include: the introduction of brain and somatic oximetry; transesophageal echocardiographic hemodynamic monitoring and bedside focused ultrasound; ultrasound-guided vascular access; point-of-care coagulation surveillance; right ventricular pressure monitoring; novel inhaled treatment for right ventricular failure; new approaches for postoperative pain management; novel approaches in specialized care procedures to ensure quality control; and specific approaches to optimize the management for postoperative cardiac arrest. Herein, we discuss the reasons that each of these components are particularly important in improving perioperative care, describe how they can be addressed, and their impact in the care of patients who undergo cardiac surgery.

Cerebral oximetry in cardiac anesthesia

Cerebral oximetry based on near-infrared spectroscopy (NIRS) is increasingly used during the perioperative period of cardiovascular operations. It is a noninvasive technology that can monitor the regional oxygen saturation of the frontal cortex. Current literature indicates that it can stratify patients preoperatively according their risk. Intraoperatively, it provides continuous information about brain oxygenation and allows the use of brain as sentinel organ indexing overall organ perfusion and injury. This review focuses on the clinical validity and applicability of this monitor for cardiac surgical patients.

The effect of tourniquet deflation on hemodynamics and regional cerebral oxygen saturation in aged patients undergoing total knee replacement surgery

BACKGROUND

Inflation and deflation of a pneumatic tourniquet used in total knee replacement surgery induces various changes in patient's hemodynamic and metabolic status, which may result in serious complications, especially in aged patients. Near-infrared spectroscopy (NIRS) is a monitoring device designed to estimate the regional cerebral oxygen saturation. We evaluated the effect of tourniquet deflation on hemodynamics and regional cerebral oxygen saturation in aged patients undergoing total knee replacement surgery, using NIRS.

METHODS

Twenty-eight American Society of Anesthesiologists physical status I or II patients, over the age of sixty-five years undergoing total knee replacement surgery, were included. Under general anesthesia, the mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume (SV), and regional cerebral oxygen saturation (rSO(2)) were recorded before induction of anesthesia and every 2 min after tourniquet deflation for 20 min. Arterial blood gas analysis was performed 5 min before, in addition to 0, and 10 min after tourniquet deflation.

RESULTS

The decrease of rSO(2) was not significant during 20-min deflation period. MAP, CO and SV showed significant decrease during 2 to 12, 4 to 6 and 2 to 6-min period after tourniquet deflation, respectively (P < 0.05). There was no relationship between a maximal decrease of MAP and rSO(2).

CONCLUSIONS

In aged patients undergoing total knee replacement surgery under general anesthesia, tourniquet deflation caused significant changes in hemodynamic and metabolic status, but not in regional cerebral oxygen saturation. It is recommended to monitor neurologic status, as well as hemodynamic and metabolic status to avoid serious complications, especially in aged patients.

Cerebral oximetry and cognitive dysfunction in elderly patients undergoing surgery for hip fractures: a prospective observational study

Aim:

This study was conducted to examine perioperative cerebral oximetry changes in elderly patients undergoing hip fracture repair and evaluate the correlation between regional oxygen saturation (rSO₂) values, postoperative cognitive dysfunction (POCD) and hospital stay.

Materials and Methods:

This prospective observational study included 69 patients. Data recorded included demographic information, rSO₂ values from baseline until the second postoperative hour and Mini Mental State Examination (MMSE) scores preoperatively and on postoperative day 7. MMSE score ≤23 was considered evidence of cognitive dysfunction. Postoperative confusion or agitation, medications administered for postoperative agitation, and hospital length of stay were also recorded. Data were analyzed with Student’s t-test, Pearson’s correlation or multiple regression analysis as appropriate.

Results:

Patient age was 74±13 years. Baseline left sided rSO₂ values were 60±10 and increased significantly after intubation. Baseline rSO₂ L<50 and <45 was observed in 11.6% and 10.1% of patients respectively. Perioperative cerebral desaturation occurred in 40% of patients. MMSE score was 26.23 ± 2.77 before surgery and 25.94 ± 2.52 on postoperative day 7 (p=0.326). MMSE scores ≤ 23 were observed preoperatively in 6 and postoperatively in 9 patients. Patients with cognitive dysfunction had lower preoperative hematocrit, hemoglobin, SpO₂ and rSO₂ values at all times, compared to patients who did not. There was no correlation between rSO₂ or POCD and hospital stay. Patients with baseline rSO₂ <5 required more medications for postoperative agitation.

Conclusion:

Cognitive dysfunction occurs preoperatively and postoperatively in elderly patients with hip fractures, and is associated with low cerebral rSO₂ values.

Near infrared spectroscopy describes physiologic payback associated with excess postexercise oxygen consumption in healthy controls and children with complex congenital heart disease

Exercise creates a physiologic burden with recovery from such effort crucial to adaptation. Excess postexercise oxygen consumption (EPOC) refers to the body's increased metabolic need after work. This investigation was designed to determine the role of near infrared spectroscopy (NIRS) in the description of exercise recovery in healthy controls (NL) and children with congenital heart disease (CHD). Subjects were recruited with exercise testing performed to exhaustion. Exercise time (EXT), heart rate (HR), and oxygen consumption (VO(2)) were measured. Four-site NIRS (brain, kidney, deltoid, and vastus lateralis) were measured during exercise and into recovery to establish trends. Fifty individuals were recruited for each group (NL = 26 boys and 24 girls; CHD = 33 boys and 17 girls). Significant differences existed between EXT, VO(2), and peak HR (P < 0.01). NIRS values were examined at four distinct intervals: rest, peak work, and 2 and 5 min after exercise. Significant cerebral hyperemia was seen in children with CHD post exercise when compared to normal individuals in whom redistribution patterns were directed to somatic muscles. These identified trends support an immediate compensation of organ systems to re-establish homeostasis in peripheral beds through enhanced perfusion. Noninvasive NIRS monitoring helps delineate patterns of redistribution associated with EPOC in healthy adolescents and children with CHD.

Baseline cerebral oximetry values in elderly patients with hip fractures: a prospective observational study

AIM

This study was conducted to evaluate baseline cerebral tissue regional oxygen saturation (rSO(2)) values and identify risk factors related to severe rSO(2) reductions in elderly patients with hip fractures.

PATIENTS AND METHODS

This was a prospective observational single-centre study on patients undergoing scheduled or urgent operation for isolated hip fracture. The study was approved by the Institution Ethics Committee, and all patients signed informed consent before entering the study. Data were collected on factors potentially related to baseline cerebral rSO(2). Data were analysed with Student's t-test, Pearson's correlation or multiple regression analysis as appropriate.

RESULTS

Sixty-nine patients, aged (mean±standard deviation (SD)) 74±13 years participated. Left baseline rSO(2) was 60.09±10.20 and right baseline rSO(2) was 58.64±9.92. Baseline rSO(2)<45 was observed in 10.1% of patients on the left and 8.7% on the right side. Correlation between left- and right-side baseline cerebral rSO(2) was highly significant (r=0.852, p<0.001). Baseline cerebral rSO(2) had a positive, highly significant correlation with preoperative haematocrit (r=0.50, p<0.001) and arterial haemoglobin oxygen saturation (SpO(2)) (r=0.587, p<0.001), but correlation was negative with the American Society of Anesthesiologists (ASA) physical status (r=-0.42, p<0.001) and age (r=-0.39, p=0.001). Linear regression showed that preoperative haematocrit accounts for 23% (R(2)=0.23) of baseline rSO(2) variability, whereas preoperative haematocrit and SpO(2) combined account for 43.7% of rSO(2) variability (R(2)=0.437). Combined preoperative haematocrit+SpO(2)+age accounted for 51.3% (R(2)=0.513) of observed rSO(2) variability.

CONCLUSION

Low baseline cerebral rSO(2) values are common in elderly hip fracture patients, despite normal haemodynamic and arterial saturation values. Preoperative haematocrit, SpO(2) and age explain a significant portion of cerebral rSO(2) variability. More studies are needed to validate our findings and assess the potential benefit of interventions aimed at improving cerebral rSO(2) in elderly hip fracture patients.

Correlation between cerebral tissue and central venous oxygen saturation during off-pump coronary bypass graft surgery

We compared simultaneous regional cerebral oxygen saturation and central venous oxygen saturation at different time periods in 20 adult patients (median age, 57.9; range, 35 to 76 years) undergoing off-pump coronary artery bypass (OPCAB) graft surgery (n= 20). Mean arterial pressure (MAP), partial pressure of carbon dioxide (PcvCO(2)), heart rate, haematocrit (Hct), lactate and patient oxygen saturation (SpO(2)) were also recorded as a secondary analysis to determine independent predictors of cerebral desaturation and interactions between predictors. The cross-sectional analysis performed at each time point showed several significant moderate to strong positive correlations between central venous oxygen saturation and both right and left cerebral oxygen saturations; however, right cerebral saturations correlated better with central venous saturations than left cerebral saturation. Partial pressure of carbon dioxide (PcvCO(2)) was identified as a major predictor of cerebral saturation 0.59 (p < 0.001). Central venous saturation can be used as a surrogate measure of cerebral oxygen saturation during OPCAB surgery.

Cerebral desaturation during cardiac arrest: its relation to arrest duration and left ventricular pump function

OBJECTIVE

To determine the impact of brief periods of cardiac arrest (CA) on regional cerebral oxygen saturation (rSO2) in patients with low left ventricular ejection fraction (LVEF <30%).

DESIGN

Prospective observational study.

SETTING

Cardiac surgery room at a university hospital.

PATIENTS

Seventy-seven consecutive patients undergoing elective implantation of a cardioverter/defibrillator in monitored anesthesia care. According to preoperative assessments, left ventricular function was classified as normal (LVEF >50%), moderately impaired (LVEF 30%-50%), or severely reduced (LVEF <30%).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

rSO2 was determined during threshold testing with concomitant induction of CA. In patients with LVEF <30%, mean baseline rSO2 (59%) was already below the lower range of normal despite normal arterial blood pressure, heart rate, and arterial oxygen saturation. rSO2 increased by 6% after 6 L/min oxygen insufflation (p < 0.05) and dropped again in each group after CA, reaching a nadir after successful defibrillation. Patients with LVEF <30% and baseline rSO2 <63% exhibited the lowest values. They also showed the highest incidence (11%) of critical cerebral desaturations (i.e., >20% drop from baseline or rSO2 value <50%). rSO2 in patients with LVEF <30% was always below that determined in patients with LVEF >30% (p < 0.05). There was a strong correlation between rSO2 values before CA and rSO2 nadir (p < 0.05). The drop in rSO2 was only moderately related to the brief CAs (p < 0.05).

CONCLUSION

These findings demonstrate that severely compromised left ventricular pump function is associated with diminished rSO2. As these patients seem to be more susceptible to critical desaturations, they may be prone to severe tissue hypoxemia unless adequate oxygen delivery is reestablished rapidly. This may contribute to the poor neurologic outcome after successful resuscitation in patients with LVEF <30%.

Baseline regional cerebral oxygen saturation correlates with left ventricular systolic and diastolic function

OBJECTIVE

To evaluate the correlation between baseline cerebral oxygen saturation (ScO(2)) and cardiac function as assessed by pulmonary artery catheterization and transesophageal echocardiography (TEE).

DESIGN

A retrospective study.

SETTING

A tertiary care university hospital.

PARTICIPANTS

Cardiac surgery patients.

MEASUREMENTS AND RESULTS

Patients undergoing cardiac surgery with bilateral recording of their baseline ScO(2) using the INVOS 4100 (Somanetics, Troy, MI) were selected. A pulmonary artery catheter was used to obtain their hemodynamic profile. Left ventricular (LV) systolic and diastolic function was evaluated by TEE, after the induction of anesthesia, using standard criteria. A model was developed to predict ScO(2). A total of 99 patients met the inclusion criteria. There were significant correlations between mean ScO(2) values and central venous pressure (CVP) (r = -0.31, p = 0.0022), pulmonary capillary wedge pressure (r = -0.25, p = 0.0129), mean pulmonary artery pressure (MPAP) (r = -0.24, p = 0.0186), mean arterial pressure/MPAP ratio (r = 0.33, p = 0.0011), LV fractional area change (<35, 35-50, and >or=50, p = 0.0002), regional wall motion score index (r = -0.27, p = 0.0062), and diastolic function (p = 0.0060). The mean ScO(2) had the highest area under the receiver operating characteristic curve (0.74; confidence interval, 0.64-0.84) to identify LV systolic dysfunction. A model predicting baseline ScO(2) was created based on LV systolic echocardiographic variables, CVP, sex, mitral valve surgery, and the use of beta-blocker (r(2) = 0.42, p < 0.001).

CONCLUSION

Baseline ScO(2) values are related to cardiac function and are superior to hemodynamic parameters at predicting LV dysfunction.

A Proposed Algorithm for the Intraoperative Use of Cerebral Near-Infrared Spectroscopy

Near-infrared spectroscopy (NIRS) is a technique that can be used as a noninvasive and continuous monitor of the balance between cerebral oxygen delivery and consumption. The authors develop and propose an algorithm for the use of NIRS based on optimizing factors that can affect cerebral oxygen supply/demand. These factors are the position of the vascular cannula, perfusion pressure, arterial oxygen content, partial pressure of carbon dioxide, haemoglobin, cardiac output, and the cerebral metabolic rate of oxygen. Dissemination of a useful treatment algorithm is the primary purpose of this article. Further multicenter studies are necessary to confirm the benefits and cost-effectiveness of this promising monitoring modality.

Cerebrovascular effects of hemodialysis in chronic kidney disease

Patients with end-stage renal disease (ESRD) undergoing hemodialysis are known to suffer cognitive deficits and stroke of unknown etiology. It has been suspected that the treatment itself may contribute to the syndrome by unknown mechanisms, which we investigated in this study. End-stage renal disease patients on hemodialysis (n=19) or peritoneal dialysis (PD, n=5) were compared with 14 healthy controls. Subjects participated in magnetic resonance imaging (MRI) measurements of cerebral atrophy, cerebral blood flow (CBF) arterial spin labeled-MRI (ASL-MRI), quantitative Doppler blood flow through the internal carotid artery, and cerebral oxymetry. The Doppler and oxymetry procedures were also performed at the beginning and end of a single hemodialysis session. End-stage renal disease patients on hemodialysis showed significant cerebral atrophy, associated with longer hemodialysis duration and cognitive deficits, including focal bilateral lesions in the caudate nucleus and midbrain. Cerebral oxygenation was extremely low before dialysis (rSO(2) 41+/-13, compared with 70+/-2 in controls, P<0.02) and improved only slightly after dialysis. Carotid blood flow was also very low at the start of dialysis (115+/-28 mL/sec, versus 193+/-56 in controls, P<0.005) but normalized at the end of the session (181 mL/sec). The PD patients showed intermediate values, between the hemodialysis and controls. Notably, duration of hemodialysis treatment predicted global gray-matter volume (r=-0.74), change of blood flow during dialysis (r=-0.65), and baseline rSO(2) (r=-0.65). The findings suggest that ESRD patients on hemodialysis suffer low CBF during the interdialytic cycle. Coupled with low cerebral oxygenation levels and atherosclerosis, this may contribute significantly to the etiology of the observed cerebral atrophy, cognitive deficits, and high stroke prevalence.

Functional Near Infrared Spectroscopy (fNIRS): An Emerging Neuroimaging Technology with Important Applications for the Study of Brain Disorders

Functional near-infrared spectroscopy (fNIRS) is an emerging functional neuroimaging technology offering a relatively non-invasive, safe, portable, and low-cost method of indirect and direct monitoring of brain activity. Most exciting is its potential to allow more ecologically valid investigations that can translate laboratory work into more realistic everyday settings and clinical environments. Our aim is to acquaint clinicians and researchers with the unique and beneficial characteristics of fNIRS by reviewing its relative merits and limitations vis-à-vis other brain-imaging technologies such as functional magnetic resonance imaging (fMRI). We review cross-validation work between fMRI and fNIRS, and discuss possible reservations about its deployment in clinical research and practice. Finally, because there is no comprehensive review of applications of fNIRS to brain disorders, we also review findings from the few studies utilizing fNIRS to investigate neurocognitive processes associated with neurological (Alzheimer's disease, Parkinson's disease, epilepsy, traumatic brain injury) and psychiatric disorders (schizophrenia, mood disorders, anxiety disorders).

Monitoring Brain Oxygen Saturation During Coronary Bypass Surgery: A Randomized, Prospective Study

BACKGROUND

Cerebral deoxygenation is associated with various adverse systemic outcomes. We hypothesized, by using the brain as an index organ, that interventions to improve cerebral oxygenation would have systemic benefits in cardiac surgical patients.

METHODS

Two-hundred coronary artery bypass patients were randomized to either intraoperative cerebral regional oxygen saturation (rSO2) monitoring with active display and treatment intervention protocol (intervention, n = 100), or underwent blinded rSO2 monitoring (control, n = 100). Predefined clinical outcomes were assessed by a blinded observer.

RESULTS

Significantly more patients in the control group demonstrated prolonged cerebral desaturation (P = 0.014) and longer duration in the intensive care unit (P = 0.029) versus intervention patients. There was no difference in overall incidence of adverse complications, but significantly more control patients had major organ morbidity or mortality (death, ventilation >48 h, stroke, myocardial infarction, return for re-exploration) versus intervention group patients (P = 0.048). Patients experiencing major organ morbidity or mortality had lower baseline and mean rSO2, more cerebral desaturations and longer lengths of stay in the intensive care unit and postoperative hospitalization, than patients without such complications. There was a significant (r(2) = 0.29) inverse correlation between intraoperative rSO2 and duration of postoperative hospitalization in patients requiring > or =10 days postoperative length of stay.

CONCLUSION

Monitoring cerebral rSO2 in coronary artery bypass patients avoids profound cerebral desaturation and is associated with significantly fewer incidences of major organ dysfunction.

Per-operative cerebral near-infrared spectroscopy (NIRS) predicts maternal hypotension during elective caesarean delivery in spinal anaesthesia

BACKGROUND

Spinal anaesthesia-induced maternal hypotension is common during elective caesarean section. This study evaluated whether cerebral near-infrared spectroscopy predicts maternal hypotension, defined as a 25% reduction in systolic blood pressure or heart rate or presentation of clinical symptoms.

METHOD

Thirty-eight ASA I-II parturients scheduled for elective caesarean section with spinal anaesthesia were monitored by near-infrared spectroscopy for changes in cerebral oxygenation (ScO(2)) with the recordings blinded to the anaesthesiologist.

RESULTS

There was a 5% decrease in ScO(2) (median 8%, interquartile range 5-11%) in all 22 patients who developed hypotension, whereas only 2 of 13 women who did not develop hypotension had a 5% decrease in ScO(2). Median time from a 5% decrease in ScO(2) to hypotension was 81 (interquartile range 30-281) s. The sensitivity of near-infrared spectroscopy to predict hypotension was 1.00, with a specificity 0.85 and a predictability of 0.91.

CONCLUSION

The results demonstrate a relationship between ScO(2) and impending hypotension during low-dose spinal anaesthesia for elective caesarean section. We suggest that immediate measures are taken to stabilise blood pressure if the near-infrared spectroscopy determined cerebral oxygenation decreases by more than 5%.

Cerebral oxygenation responses to standing in elderly patients with predominantly diastolic dysfunction

Patients with left ventricular dysfunction may have different orthostatic responses of blood pressure (BP) and cerebral oxygenation than healthy elderly subjects. We investigated orthostatic changes in systemic haemodynamic variables and cerebral oxygenation in 21 elderly patients with heart failure New York Heart Association class I-III in stable condition (age 70-83 years) after withdrawal of furosemide and captopril for 2 weeks, and in 18 healthy elderly subjects (age 70-84 years). Frontal cortical concentration changes of oxyhaemoglobin ([O2Hb]) and deoxyhaemoglobin ([HHb]) were continuously measured by near-infrared spectrophotometry and BP changes by Finapres before and during 10 min of standing. Upon standing [O2Hb] reflecting blood flow, changed by -1.2 +/- 0.9 micromol L-1 (mean +/- SEM) in the patients, whereas it decreased by -4.5 +/- 0.6 micromol L-1 (P<0.01) in the healthy subjects after standing (P<0.05 between groups). [HHb] reflecting the sum of cerebral blood flow, arterial oxygen saturation and cerebral oxygen uptake, increased by 1.5 +/- 0.5 micromol L-1 (P<0.05) and 1.7 +/- 0.6 micromol L-1 (P<0.05), respectively. Compared with healthy elderly subjects, elderly patients with left ventricular dysfunction showed smaller orthostatic [O2Hb] decreases (P<0.01), in relation to higher orthostatic BP rises (P<0.05). These findings indicate that BP changes and an altered cardiovascular balance may influence orthostatic cortical haemodynamic responses in elderly subjects.

Cerebral oxygenation during exercise in patients with terminal lung disease

STUDY OBJECTIVES

In patients with terminal lung disease who were exercising, we assessed whether improved arterial O2 saturation with an increased fraction of inspired oxygen (FIO2) affects cerebral oxygenation.

DESIGN

Randomized, crossover.

PATIENTS AND METHODS

The cerebral changes in oxyhemoglobin (DeltaHbO2) and changes in deoxyhemoglobin (DeltaHb) levels were evaluated using near-infrared spectrophotometry and the middle cerebral artery (MCA) mean velocity (V(mean)) was determined by transcranial Doppler ultrasonography in 13 patients with terminal lung disease (New York Heart Association class III-IV). Patients were allocated to an FIO2 of either 0.21 or 0.35 during incremental exercise with 15 min between trials.

RESULTS

Peak exercise intensity (mean [+/- SE], 26 +/- 4 W) reduced the arterial O2 pressure (at rest, 64 +/- 3 mm Hg; during exercise, 56 +/- 3 mm Hg) and the arterial oxygen saturation (SaO2) [at rest, 92 +/- 2%; 87 +/- 2%; p < 0.05], while the arterial CO2 pressure was not significantly affected. The MCA V(mean) increased from 49 +/- 5 to 63 +/- 7 cm/s (p < 0.05) as did the DeltaHb, while the DeltaHbO2 remained unaffected by exercise. With an elevated FIO2, the SaO2 level (at rest, 95.8 +/- 0.7%; during exercise, 96.0 +/- 1.0%) and arterial O2 pressure (at rest, 102 +/- 11 mm Hg; during exercise, 100 +/- 8 mm Hg) were not significantly affected by exercise, and the levels of blood oxygenation remained higher than the values established at normoxia (p < 0.05). The MCA V(mean) increased to a level similar to that achieved during control exercise (ie, to 70 +/- 11 cm/s). In contrast to control exercise, DeltaHb decreased while DeltaHbO2 increased during exercise with 35% O2 (p < 0.05).

CONCLUSION

An O2-enriched atmosphere enabled patients with terminal lung disease to maintain arterial O2 saturation during exercise. An exercise-induced increase in cerebral perfusion was not affected by hyperoxia, whereby the enhanced availability of oxygenated hemoglobin increases cerebral oxygenation. The clinical implication of the study is that during physical activity patients with terminal lung disease are recommended to use an elevated FIO2 to protect cerebral oxygenation.