Retrograde cerebral perfusion versus selective cerebral perfusion as evaluated by cerebral oxygen saturation during aortic arch reconstruction

The Influence of Extracerebral Tissue on Continuous Wave Near-Infrared Spectroscopy in Adults: A Systematic Review of In Vivo Studies

Near-infrared spectroscopy (NIRS) is a non-invasive technique for measuring regional tissue haemoglobin (Hb) concentrations and oxygen saturation (rSO₂). It may be used to monitor cerebral perfusion and oxygenation in patients at risk of cerebral ischemia or hypoxia, for example, during cardiothoracic or carotid surgery. However, extracerebral tissue (mainly scalp and skull tissue) influences NIRS measurements, and the extent of this influence is not clear. Thus, before more widespread use of NIRS as an intraoperative monitoring modality is warranted, this issue needs to be better understood. We therefore conducted a systematic review of published in vivo studies of the influence of extracerebral tissue on NIRS measurements in the adult population. Studies that used reference techniques for the perfusion of the intra- and extracerebral tissues or that selectively altered the intra- or extracerebral perfusion were included. Thirty-four articles met the inclusion criteria and were of sufficient quality. In 14 articles, Hb concentrations were compared directly with measurements from reference techniques, using correlation coefficients. When the intracerebral perfusion was altered, the correlations between Hb concentrations and intracerebral reference technique measurements ranged between |r| = 0.45-0.88. When the extracerebral perfusion was altered, correlations between Hb concentrations and extracerebral reference technique measurements ranged between |r| = 0.22-0.93. In studies without selective perfusion modification, correlations of Hb with intra- and extracerebral reference technique measurements were generally lower (|r| < 0.52). Five articles studied rSO₂. There were varying correlations of rSO₂ with both intra- and extracerebral reference technique measurements (intracerebral: |r| = 0.18-0.77, extracerebral: |r| = 0.13-0.81). Regarding study quality, details on the domains, participant selection and flow and timing were often unclear. We conclude that extracerebral tissue indeed influences NIRS measurements, although the evidence (i.e., correlation) for this influence varies considerably across the assessed studies. These results are strongly affected by the study protocols and analysis techniques used. Studies employing multiple protocols and reference techniques for both intra- and extracerebral tissues are therefore needed. To quantitatively compare NIRS with intra- and extracerebral reference techniques, we recommend applying a complete regression analysis. The current uncertainty regarding the influence of extracerebral tissue remains a hurdle in the clinical implementation of NIRS for intraoperative monitoring. The protocol was pre-registered in PROSPERO (CRD42020199053).

Aortic Dissection

Acute aortic dissection is a highly morbid condition with high mortality that requires emergent surgical evaluation and repair. The intraoperative management of acute aortic dissection requires the anesthesiologist to do far more than administer anesthesia and begins before the patient arrives at the operative theater. High-fidelity communication with the surgeon, knowledge of the surgical plan, knowledge of the anatomy of the dissection, and a nuanced understanding of aortic dissection pathophysiology are all critical aspects of anesthetic management.

Duration of deep hypothermic circulatory arrest for aortic arch surgery: is it a myth, fiction, or scientific leap?

INTRODUCTION

The use of deep hypothermic circulatory arrest (DHCA) to provide aortic surgeons with a bloodless operative field while simultaneously protecting the brain and peripheries from ischemic damage revolutionized cardiac and aortic surgery, and is currently used in specialist centers across the globe. However, it is associated with manifold adverse outcomes, including neurocognitive dysfunction and mortality. This review seeks to analyze the relationship between DHCA duration and clinical outcome, and evaluate the controversies and limitations surrounding its use.

EVIDENCE ACQUISITION

We performed a review of available literature with statistical analysis to evaluate the relationship between DHCA duration (<40 min and >40 min) and key clinical outcomes, including mortality, permanent and temporary neurological deficit, renal damage, admission length, and reintervention rate. The controversies surrounding DHCA use and future directions for care are also explored.

EVIDENCE SYNTHESIS

Statistical analysis revealed no significant association (P>0.05) between DHCA duration and clinical outcomes (early and late mortality rates, neurological deficit, admission length, and reintervention rate), both with and without adjunctive perfusion techniques.

CONCLUSIONS

Available literature suggests that the relationships between DHCA duration (with and without adjunctive perfusion) and clinical outcomes are unclear, and at present not statistically significant. Alternative surgical and endovascular techniques have been identified as promising novel approaches not requiring DHCA, as have the use of biomarkers to enable early diagnosis and intervention for aortic pathologies.

Effect of changes in cerebral oximeter values during cardiac surgery on the incidence of postoperative neurocognitive deficits (POND): A retrospective study based on propensity score-matched analysis

Objectives

The occurrence of postoperative neurocognitive deficits(POND)after major cardiac surgery is associated with an increase in perioperative mortality and morbidity. Oxidative stress caused by oxygen can affect neuronal damage, which can lead to POND. Whether the intraoperative rSO₂ value reflects oxidative stress and the associated incidence of POND is unknown.

Methods

Among 3482 patients undergoing cardiac surgery, 976 patients were allocated for this retrospective study. Of these, 230 patients (32.5%) were observed to have postoperative neurologic symptoms. After propensity score 1:2 ratio matching, a total of 690 patients were included in the analysis. Recorded data on the occurrence of POND from the postoperative period to predischarge were collected from the electronic records.

Results

The mean baseline rSO₂ value was higher in the POND (–) group than in the POND (+) group. The mean overall minimum rSO₂ value was lower in the POND (+) group (52.2 ± 8.3 vs 48.3 ± 10.5, P < 0.001). The mean overall maximum rSO₂ values were not significantly different between the two groups (72.7 ± 8.3 vs 73.2 ± 9.2, P = 0.526). However, there was a greater increase in the overall maximum rSO₂ values as compared with baseline in the POND (+) group (10.9 ± 8.2 vs 17.9 ± 10.2, P < 0.001). The degree of increase in the maximum rSO2 value was a risk factor affecting the occurrence of POND (adjusted odds ratio, 1.08; 95% confidence interval [CI], 1.04–1.11; P < 0.001). The areas under the receiver-operating characteristic curve for delta values of minimal and maximal compared with baseline values were 0.60 and 0.71, respectively.

Conclusions

Increased cerebral oximeter levels during cardiac surgery may also be a risk factor for POND. This is considered to reflect the possibility of oxidative neuronal damage, and further studies are needed in the future.

Association Between Cerebral Desaturation and Postoperative Delirium in Thoracotomy With One-Lung Ventilation: A Prospective Cohort Study

BACKGROUND

The association between cerebral desaturation and postoperative delirium in thoracotomy with one-lung ventilation (OLV) has not been specifically studied.

METHODS

A prospective observational study performed in thoracic surgical patients. Cerebral tissue oxygen saturation (Scto2) was monitored on the left and right foreheads using a near-infrared spectroscopy oximeter. Baseline Scto2 was measured with patients awake and breathing room air. The minimum Scto2 was the lowest measurement at any time during surgery. Cerebral desaturation and hypersaturation were an episode of Scto2 below and above a given threshold for ≥15 seconds during surgery, respectively. The thresholds based on relative changes by referring to the baseline measurement were <80%, <85%, <90%, <95%, and <100% baseline for desaturation and >105%, >110%, >115%, and >120% baseline for hypersaturation. The thresholds based on absolute values were <50%, <55%, <60%, <65%, and <70% for desaturation and >75%, >80%, >85%, and >90% for hypersaturation. The given area under the threshold (AUT)/area above the threshold (AAT) was analyzed. Delirium was assessed until postoperative day 5. The primary analysis was the association between the minimum Scto2 and delirium using multivariable logistic regression controlled for confounders (age, OLV time, use of midazolam, occurrence of hypotension, and severity of pain). The secondary analysis was the association between cerebral desaturation/hypersaturation and delirium, and between the AUT/AAT and delirium using multivariable logistic regression controlled for the same confounders. Multiple testing was corrected using the Holm-Bonferroni method. We additionally monitored somatic tissue oxygen saturation on the forearm and upper thigh.

RESULTS

Delirium occurred in 35 (20%) of 175 patients (65 ± 6 years old). The minimum left or right Scto2 was not associated with delirium. Cerebral desaturation defined by <90% baseline for left Scto2 (odds ratio [OR], 5.82; 95% confidence interval [CI], 2.12-19.2; corrected P =.008) and <85% baseline for right Scto2 (OR, 4.27; 95% CI, 1.77-11.0; corrected P =.01) was associated with an increased risk of delirium. Cerebral desaturation defined by other thresholds, cerebral hypersaturation, the AUT/AAT, and somatic desaturation and hypersaturation were all not associated with delirium.

CONCLUSIONS

Cerebral desaturation defined by <90% baseline for left Scto2 and <85% baseline for right Scto2, but not the minimum Scto2, may be associated with an increased risk of postthoracotomy delirium. The validity of these thresholds needs to be tested by randomized controlled trials.

The Role of Deep Hypothermia in Cardiac Surgery

Hypothermia is defined as a decrease in body core temperature to below 35 °C. In cardiac surgery, four stages of hypothermia are distinguished: mild, moderate, deep, and profound. The organ protection offered by deep hypothermia (DH) enables safe circulatory arrest as a prerequisite to carrying out cardiac surgical intervention. In adult cardiac surgery, DH is mainly used in aortic arch surgery, surgical treatment of pulmonary embolism, and acute type-A aortic dissection interventions. In surgery treating congenital defects, DH is used to assist aortic arch reconstructions, hypoplastic left heart syndrome interventions, and for multi-stage treatment of infants with a single heart ventricle during the neonatal period. However, it should be noted that a safe duration of circulatory arrest in DH for the central nervous system is 30 to 40 min at most and should not be exceeded to prevent severe neurological adverse events. Personalized therapy for the patient and adequate blood temperature monitoring, glycemia, hematocrit, pH, and cerebral oxygenation is a prerequisite and indispensable part of DH.

Non-invasive High Frequency Median Nerve Stimulation Effectively Suppresses Olfactory Intensity Perception in Healthy Males

Median nerve stimulation (MNS) had been performed in the existing literature to alleviate symptoms of nausea and vomiting. The observed facilitative effects are thought to be mediated by the vagal pathways, particularly the vagus nerve (VN) brainstem nuclei of the dorsal motor nucleus of vagus and nucleus tractus solitarius (DMV-NTS). Sense of smell is one of the major sensory modalities for inducing vomiting and nausea as a primary defense against potentially harmful intake of material. This study aimed to test effects of non-invasive, high and low frequency MNS on human olfactory functioning, with supplementary exploration of the orbitofrontal cortex (OFC) using near-infrared spectroscopy (NIRS). Twenty healthy, male, adults performed supra-threshold odor intensity tests (labeled magnitude scale, LMS) for four food-related odorant samples (presented in three different concentrations) before and after receiving high-, low frequency MNS and placebo (no stimulation), while cortical activities in the OFC was monitored by the NIRS. Data of the NIRS and LMS test of separate stimulation parameters were statistically analyzed using mixed-model analysis of variance (ANOVA). Only the high frequency MNS showed effects for suppressing the intensity perception of the moderate concentration of Amyl Acetate (p:0.042) and strong concentration of Isovaleric Acid (p:0.004) and 1-Octen-3-ol (p:0.006). These behavioral changes were coupled with significant changes in the NIRS recordings of the left (p:0.000) and right (p:0.003) hemispheric orbitofrontal cortices. This is the first study that applied non-invasive, high frequency MNS to suppress the supra-threshold odor ratings of specific concentrations of odors. The vagal networks are potential relays of MNS to influence OFC. Results from the current article implore further research into non-invasive, high frequency MNS in the investigation of its modulatory effects on olfactory function, given its potential to be used for ameliorating nausea and malnutrition associated with various health conditions.

Cerebral Circulation During Retrograde Cerebral Perfusion: Evaluation Using Laser Speckle Flowgraphy

BACKGROUND

The cerebroprotective effect of retrograde cerebral perfusion (RCP) and selective antegrade cerebral perfusion (SCP) still remains controversial. Laser speckle flowgraphy has shown much promise for novel perioperative neuromonitoring by assessing blood flow of the optic nerve head. This study aimed to evaluate the cerebral microcirculation in humans using laser speckle flowgraphy during simple circulatory arrest, RCP, and SCP under moderate hypothermia and to investigate whether RCP under moderate hypothermia is a reliable method of cerebral protection.

METHODS

A total of 23 consecutive patients who underwent a scheduled aortic arch or hemiarch surgical procedure on thoracic aorta aneurysm were enrolled. The laser speckle flowgraphy measurement that calculates mean blur ratio, a parameter of cerebral circulation, was obtained 6 times: after induction of anesthesia, baseline (T1), after initiation of cardiopulmonary bypass with cardiac arrest (T2), simple circulatory arrest (T3), RCP (T4), SCP (T5), and after the termination of cardiopulmonary bypass (T6).

RESULTS

Both mean blur ratios of simple circulatory arrest and RCP were significantly decreased compared with baseline. In contrast, no significant differences were observed between simple circulatory arrest and RCP. The mean blur ratio of SCP was significantly increased compared with both simple circulatory arrest and RCP.

CONCLUSIONS

In conclusion, no significant difference was observed in the cerebral circulation between RCP and simple circulatory arrest without adjunctive strategy under moderate hypothermia. In contrast, the cerebral circulation during SCP was significantly higher than simple circulatory arrest and RCP. These results suggest that cerebral microcirculation may not be adequate during RCP compared with SCP under moderate hypothermia.

Improvement of Olfactory Function With High Frequency Non-invasive Auricular Electrostimulation in Healthy Humans

In past literature on animal models, invasive vagal nerve stimulation using high frequencies has shown to be effective at modulating the activity of the olfactory bulb (OB). Recent advances in invasive vagal nerve stimulation in humans, despite previous findings in animal models, used low frequency stimulation and found no effect on the olfactory functioning. The present article aimed to test potential effects of non-invasive, high and low frequency vagal nerve stimulation in humans, with supplementary exploration of the orbitofrontal cortex using near-infrared spectroscopy (NIRS). Healthy, male adult participants (n = 18) performed two olfactory tests [odor threshold test (OTT) and supra-threshold test (STT)] before and after receiving high-, low frequency vagal nerve stimulation and placebo (no stimulation). Participant's olfactory functioning was monitored using NIRS, and assessed with two behavioral olfactory tests. NIRS data of separate stimulation parameters were statistically analyzed using repeated-measures ANOVA across different stages. Data from olfactory tests were analyzed using paired parametric and non-parametric statistical tests. Only high frequency, non-invasive vagal nerve stimulation was able to positively modulate the performance of the healthy participants in the STT (p = 0.021, Wilcoxon sign-ranked test), with significant differences in NIRS (p = 0.014, post-hoc with Bonferroni correction) recordings of the right hemispheric, orbitofrontal cortex. The results from the current article implore further exploration of the neurocircuitry involved under vagal nerve stimulation and the effects of non-invasive, high frequency, vagal nerve stimulation toward olfactory dysfunction which showcase in Parkinson's and Alzheimer's Diseases. Despite the sufficient effect size (moderate effect, correlation coefficient (r): 0.39 for the STT) of the current study, future research should replicate the current findings with a larger cohort.

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.

Right Axillary Artery Cannulation in Aortic Valve Replacement

OBJECTIVE

This retrospective study aimed to evaluate the results of our experience with axillary artery cannulation via a side graft in aortic valve replacement in patients with ascending aortic atherosclerotic disease.

METHODS

From January 2002 to 2012, we operated on 76 patients for aortic valve disease with the use of the axillary artery for arterial inflow in our institute. The indications for cannulation of the axillary artery were aortic aneurysm in 37 patients, severe aortic atherosclerosis in 28 patients, and re do surgery in 11 patients.

RESULTS

Right axillary artery cannulation via a side graft provides sufficient antegrade aortic flow of 2.6 ± 0.1 L/m(2) during cardiopulmonary bypass. No additional arterial cannulation was necessary to obtain sufficient perfusion during cardiopulmonary bypass. Although permanent perioperative stroke was observed in two patients, this did not occur during the operation. There were no problems with cannulation or wound and graft infections. During the follow-up period, there were no thrombotic events due to an axillary graft stump in the right upper extremities.

CONCLUSIONS

Axillary artery cannulation via a side graft is a useful and safe option for cardiopulmonary bypass in patients with atherosclerotic disease of the ascending aorta undergoing aortic valve replacement.

Cerebral near-infrared spectroscopy monitoring and neurologic outcomes in adult cardiac surgery patients: a systematic review

BACKGROUND

Near-infrared spectroscopy is used during cardiac surgery to monitor the adequacy of cerebral perfusion. In this systematic review, we evaluated available data for adult patients to determine (1) whether decrements in cerebral oximetry during cardiac surgery are associated with stroke, postoperative cognitive dysfunction (POCD), or delirium; and (2) whether interventions aimed at correcting cerebral oximetry decrements improve neurologic outcomes.

METHODS

We searched PubMed, Cochrane, and Embase databases from inception until January 31, 2012, without restriction on languages. Each article was examined for additional references. A publication was excluded if it did not include original data (e.g., review, commentary) or if it was not published as a full-length article in a peer-reviewed journal (e.g., abstract only). The identified abstracts were screened first, and full texts of eligible articles were reviewed independently by 2 investigators. For eligible publications, we recorded the number of subjects, type of surgery, and criteria for diagnosis of neurologic end points.

RESULTS

We identified 13 case reports, 27 observational studies, and 2 prospectively randomized intervention trials that met our inclusion criteria. Case reports and 2 observational studies contained anecdotal evidence suggesting that regional cerebral O(2) saturation (rSco(2)) monitoring could be used to identify cardiopulmonary bypass cannula malposition. Six of 9 observational studies reported an association between acute rSco(2) desaturation and POCD based on the Mini-Mental State Examination (n = 3 studies) or more detailed cognitive testing (n = 6 studies). Two retrospective studies reported a relationship between rSco(2) desaturation and stroke or type I and II neurologic injury after surgery. The observational studies had many limitations, including small sample size, assessments only during the immediate postoperative period, and failure to perform risk adjustments. Two randomized studies evaluated the efficacy of interventions for treating rSco(2) desaturation during surgery, but adherence to the protocol was poor in one. In the other study, interventions for rSco(2) desaturation were associated with less major organ injury and shorter intensive care unit hospitalization compared with nonintervention.

CONCLUSIONS

Reductions in rSco(2) during cardiac surgery may identify cardiopulmonary bypass cannula malposition, particularly during aortic surgery. Only low-level evidence links low rSco(2) during cardiac surgery to postoperative neurologic complications, and data are insufficient to conclude that interventions to improve rSco(2) desaturation prevent stroke or POCD.

Regional cerebral oxygen saturation on hospital arrival is a potential novel predictor of neurological outcomes at hospital discharge in patients with out-of-hospital cardiac arrest

AIM

To investigate the association between regional brain oxygen saturation (rSO(2)) on hospital arrival and neurological outcomes at hospital discharge in patients with out-of-hospital cardiac arrest (OHCA).

METHODS

A prospective cohort study was conducted, registering 179 patients with OHCA who were referred to Senri Critical Care Medical Centre between April 2009 and June 2010. Of these patients, 92 met the inclusion criteria. The primary end point was "neurological outcomes" at hospital discharge according to the "Utstein style" guidelines.

RESULTS

The overall rate of good neurological outcome at hospital discharge was 14% (n=13). Sixty-one patients with rSO(2) ≤25% showed poor neurological outcome in the receiver operating curve analysis (optimal cut-off point, 25%; sensitivity, 0.772; specificity, 1.000; positive predictive value, 1.000; area under the curve (AUC), 0.919; p<0.0001). The AUC for rSO(2) was greater than that for base excess (p=0.0461) or lactate (p=0.0128) measured on hospital arrival. Since rSO(2) >40% was previously collated with good neurological outcome after cardiovascular surgery, we categorised our patients into three groups in a post hoc analysis: patients with rSO(2) ≤25% (n=61); patients with rSO(2) 26-40% (n=9) and patients with rSO(2) >40% (n=22). Patients with good neurological outcome were as follows: 0 (0%)/61 with rSO(2) ≤25%; two (22.2%)/9 with rSO(2) 26-40% and 11 (50.0%)/22 with rSO(2) >40% (p<0.0001).

CONCLUSION

rSO(2) on hospital arrival may help predict neurological outcomes at hospital discharge in patients with OHCA.

Cerebral oxygenation during the first days of life in preterm and term neonates: differences between different brain regions

Near-infrared spectroscopy is a noninvasive method for monitoring brain oxygenation. The aim of the study was to investigate differences between cerebral oxygenation in different brain regions in newborns. In a prospective study, we monitored simultaneously left and right frontoparietal and temporo-occipital regional cerebral oxygen saturation (rScO2) and cerebral fractional tissue extraction (cFTOE: (arterial oxygen saturation (SaO2) - rScO2)/SaO2) using near-infrared spectroscopy. A 2-h measurement was performed on d 1, 3, and 7. We included 10 very preterm (GA <32 wk), 10 preterm (GA: 32-37 wk), and 10 term (GA ≥37 wk) neonates. Limits of agreement for difference of the measurements between different places were determined using the Bland-Altman method. In all subgroups, the rScO2 and cFTOE values at different regions were not different. Limits of agreement were between ±14 and ±18% for all subgroups. Left-to-right differences were small between different postnatal and GAs. A decrease and increase over time for rScO2 and cFTOE values was detected for all four brain regions, most pronounced for infants with GA <32 wk. Cerebral oxygenation in stable preterm and term neonates seems not to differ between different regions of the brain during the early neonatal period. However, variability of individual measurements was quite high as indicated by large limits of agreement.

Monitoring Brain Oxygen Saturation During Coronary Bypass Surgery Improves Outcomes in Diabetic Patients: A Post Hoc Analysis

Background: Having previously demonstrated in a prospective study of 200 coronary artery bypass (CAB) patients that by using the brain as an index organ, interventions to improve cerebral oxygenation would have systemic outcome benefits, we undertook a post hoc analysis of the diabetic subset (n = 57) of the overall study group to determine whether the outcomes of these patients were similarly improved.Methods: Case-report forms for the 200 CAB patients study patients with a preoperative diagnosis of diabetes mellitus were stratified to intraoperative cerebral regional oxygen saturation (rSO2) monitoring with active display and a treatment intervention protocol (intervention group, n = 28) or to blinded rSO2 monitoring (control group, n = 29) and analyzed.Results: There were no significant differences between the 2 groups in overall risk factors, although there were trends toward a higher body mass index, a worse angina score, a worse grade of ventricle, and greater use of off-pump coronary revascularization in the control group of patients. The 2 groups were similar with respect to overall insulin dosage and perioperative blood glucose concentrations. Significantly more diabetic patients in the control group demonstrated profound cerebral desaturation, with an area under the curve of 2 postoperative complications (P = .006; = 0.37). An analysis after removing the patients who underwent off-pump surgery revealed that the control group had significantly more patients with sternal wound infections (5 versus 0; P = .047) and 2 postoperative complications (6 versus 0; P = .008) than the intervention group, as well as a trend toward longer ICU and postoperative hospitalization stays in the control group.Conclusion: Monitoring and management of cerebral rSO2 in diabetic CAB patients avoid profound cerebral desaturation and are associated with significantly lower incidences of complications and shorter postoperative lengths of stay.Implication Statement: A post hoc analysis of the diabetic cohort of a prospective, randomized, and blinded study of CAB patients revealed that those in whom cerebral oxygen saturation was actively monitored and maintained demonstrated significantly lower incidences of complications, resulting in shorter ICU and postoperative hospital stays compared with an unmonitored control group.

Cerebral Near-Infrared Spectroscopy in Adult Patients After Cardiac Surgery Is Not Useful for Monitoring Absolute Values But May Reflect Trends in Venous Oxygenation Under Clinical Conditions

OBJECTIVE

Cerebral near-infrared spectroscopy (NIRS) was evaluated for use in monitoring global oxygenation in adult patients after cardiac surgery.

DESIGN

Prospective, randomized clinical monitoring study.

SETTING

Intensive care unit for cardiac surgery; university hospital.

PARTICIPANTS

The study included 35 patients scheduled for cardiac surgery with insertion of a pulmonary artery catheter; patients with known cerebral-vascular perfusion disturbances were excluded.

INTERVENTIONS

Noninvasive cerebral NIRS oxygen saturation (rSO(2)) and conventional intensive care monitoring parameters were assessed.

MEASUREMENTS AND MAIN RESULTS

Simple regression analysis was used to assess the correlation of rSO(2) to hemodynamic parameters. There was fair-to-moderate intersubject correlation to hemoglobin concentration (r = 0.45, p < 0.0001) and mixed venous oxygen saturation (SmvO(2)) (r = 0.33, p < 0.0001). Sensitivity and specificity of rSO(2) to detect substantial (>or=1 standard deviation) changes in mixed venous oxygen saturation were 94% and 81%, respectively.

CONCLUSIONS

Cerebral NIRS in adult patients might not be the tool to replace mixed venous oxygen monitoring. Further work has to be done to assess its potential to reflect intraindividual trends.

Cerebral Perfusion

Aortic arch surgery necessitates interrupted brain perfusion and carries a risk of brain injury. Various brain protective techniques have been advocated to reduce risk including hypothermic arrest and retrograde or selective antegrade perfusion. Knowledge of the pathophysiologic consequences of deep hypothermia, may aid the surgeon in deciding when to initiate circulatory arrest and for how long. Retrograde cerebral perfusion use was advocated to prolong safe arrest durations but may not improve outcomes. Selective antegrade cerebral perfusion appears to have become the preferred method of brain protection. However, the delivery conditions and optimal perfusate constitution require further study.

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.

Axillary Cannulation for Proximal Aortic Surgery is as Safe in the Emergent Setting as in Elective Cases

BACKGROUND

Right axillary artery cannulation and selective antegrade cerebral perfusion (SCP) have become well-described strategies in the surgical treatment of proximal aortic disease. Many series report increases in adverse outcomes with SCP used in emergent settings. We compare outcomes in elective and emergent patients.

METHODS

Over 21 months, SCP through right axillary cannulation with a side graft was performed in 61 patients. Thirty-three percent (20 of 61) underwent emergent operation for Stanford type A dissection or intramural hematoma, including 3 of 20 (4.7%) with pericardial tamponade; the remainder of SCP (41 of 61) was elective. The mean follow-up was 9.1 +/- 0.40 months.

RESULTS

Selective antegrade cerebral perfusion was used in 20 of 22 emergent cases (91%), with 2 unsuccessful cannulation attempts, and no peripheral arterial dissections encountered. The SCP flows averaged 16.3 +/- 0.71 cc x kg(-1) x min(-1) for a mean perfusion period of 26.1 +/- 1.9 minutes. The average cardiopulmonary bypass time for all patients was 173 +/- 11 minutes. Average hospital stay was 8.1 +/- 0.80 days. One case (1.3%) of permanent and 3 cases (4.8%) of temporary neurologic dysfunction occurred in SCP patients. The hospital mortality rate for emergent SCP cases (2 of 20, 10%) was not statistically different from the mortality rate for elective SCP cases (3 of 41, 7.3%, p = not significant), with no difference in complication rates. All 3 SCP patients with preoperative tamponade survived without complication. Cerebral oximetry data showed a trend toward decreased left-sided (contralateral) scalp perfusion. There was no association of emergent status with neurologic dysfunction, death, or any other adverse outcome.

CONCLUSIONS

Axillary cannulation and SCP in the surgical treatment of proximal aortic pathology is safe in both elective and emergent settings.

Assessment of Cerebral Oxygen Balance During Deep Hypothermic Circulatory Arrest by Continuous Jugular Bulb Venous Saturation and Near-Infrared Spectroscopy

OBJECTIVE

The purpose of this study was to compare jugular venous bulb saturation (SjvO(2)) and regional cerebral oximetry (rSO(2)) by near-infrared spectroscopy (NIRS) during procedures with deep hypothermic circulatory arrest (DHCA).

DESIGN

Prospective observational study.

SETTING

Academic hospital.

PARTICIPANTS

Patients undergoing aortic reconstructive surgery with DHCA from July 2001 to January 2005.

INTERVENTION

The authors examined cerebral oxygenation by continuous NIRS monitoring and by blood gas analysis of intermittently sampled jugular bulb blood (SjvO(2)). Data were obtained during various stages of the procedure in 29 patients. NIRS measurements were compared with SjvO(2).

MEASUREMENTS AND MAIN RESULTS

NIRS and SjvO(2) trends were similar. Overall, cerebral venous oxygen saturation obtained from NIRS was lower compared with SjvO(2) (p < 0.05), especially during periods of low temperature. The mean correlation between NIRS and SjvO(2) was 0.363, and the individual correlations varied from -0.11 to 0.91. The low mean correlation was because of a high degree of variability in the NIRS data between patients.

CONCLUSION

It was concluded that NIRS does not closely correlate with SjvO(2) in this patient population. Cerebral oximetry measured by NIRS could not replace jugular bulb saturation as an intraoperative marker of adequate metabolic suppression.

Monitoring cerebral oxygen saturation in elderly patients undergoing general abdominal surgery: a prospective cohort study

BACKGROUND AND OBJECTIVES

The aim of this prospective, observational study was to evaluate changes in regional cerebral oxygen saturation (rSO2) and incidence of intraoperative cerebral desaturation in a cohort of elderly patients undergoing major abdominal surgery.

METHODS

rSO2 was continuously monitored on the left and right sides of the forehead in 60 patients older than 65 yr (35 males and 25 females; ASA II-III; age: 72 +/- 5 yr; without pre-existing cerebral pathology, and baseline Mini Mental State Examination (MMSE) score >23) undergoing sevoflurane anaesthesia for major abdominal, non-vascular surgery >2 h.

RESULTS

Baseline rSO2 was 63 +/- 8%; cerebral desaturation (rSO2 decrease <75% of baseline or <80% in case of baseline rSO2 <50%) occurred in 16 patients (26%). The MMSE decreased from 28 +/- 1 before surgery to 27 +/- 2 on 7th postoperative day (P = 0.05). A decline in cognitive function (decrease in MMSE score > or = 2 points one week after surgery as compared to baseline value) was observed in six patients without intraoperative cerebral desaturation (13.6%) and six patients who had intraoperative cerebral desaturation (40%) (P = 0.057) (odds ratio: 4.22; CI95%: 1.1-16). Median (range) hospital stay was 14 (5-41) days in patients with an area under the curve of rSO2 <50% (AUCrSO2<50%) >10 min%, and 10 (4-30) days in those with an AUCrSO2<50% <10 min% (P = 0.0005).

CONCLUSIONS

In a population of healthy elderly patients, undergoing non-vascular abdominal surgery cerebral desaturation can occur in up to one in every four patients, and the occurrence of cerebral desaturation is associated with a higher incidence of early postoperative cognitive decline and longer hospital stay.

Aortic Arch Reconstruction: Safety of Moderate Hypothermia and Antegrade Cerebral Perfusion During Systemic Circulatory Arrest

BACKGROUND AND AIM

The ideal strategy for cerebral protection during aortic arch (AA) reconstructive surgery remains undefined. Antegrade cerebral perfusion (ACP) during systemic circulatory arrest (SCA) may provide superior results; however, optimal systemic temperature is undetermined. Our objective was to determine whether "deep" hypothermia is necessary during ACP with SCA, and whether the degree of hypothermia is associated with neurologic outcomes postoperatively.

METHODS

Retrospective series of 72 consecutive patients (aged 65.9 +/- 3.2 years) who underwent AA reconstructive surgery at Vancouver General Hospital using a cerebral protection strategy of ACP with SCA between December 1995 and December 2002. Patients were divided into two groups according to lowest systemic temperature: <22 degrees C (n = 52) and > or =22 degrees C (n = 20).

RESULTS

ACP was via right axillary or innominate artery, +/- left common carotid cannulation. Median SCA time with ACP was not different between groups. There were four hospital deaths (5.6%) (three from the <22 degrees C group). Eight patients (11.2%) had major neurologic injuries (seven from the <22 degrees C group): 4 (5.6%) permanent (1 fatal) and 4 (5.6%) temporary. There was a trend toward a significantly higher incidence of delirium in the <22 degrees C group than the > or =22 degrees C group (30.8 vs 10.0%, respectively, p = 0.07).

CONCLUSIONS

In our experience, SCA with ACP was a safe technique for AA reconstructive surgery. The observation of a larger number of major neurologic injuries, and a trend toward a higher incidence of delirium in the <22 degrees C group, suggests that systemic temperatures below 22 degrees C may not be necessary and may be associated with a higher incidence of neurologic injury when using ACP during SCA.

Methods of cerebral protection in surgery of the thoracic aorta

During the last decade, a considerable increase in the number of operations on the thoracic aorta has been observed. Although patient's outcomes have improved considerably, this surgery is still associated with significant morbidity and mortality due to neurological complications. Various methods have been proposed and widely used as means to protect the brain from ischemic damage. This review summarizes the principal methods of cerebral protection, describes the advantages and disadvantages of each method and their impact on patient outcomes, and discusses the different surgical techniques proposed to minimize the risk of cerebral injuries.

Continuous Monitoring of Cerebral Oxygen Saturation in Elderly Patients Undergoing Major Abdominal Surgery Minimizes Brain Exposure to Potential Hypoxia

Elderly patients are more prone than younger patients to develop cerebral desaturation because of the reduced physiologic reserve that accompanies aging. To evaluate whether monitoring cerebral oxygen saturation (rSO(2)) minimizes intraoperative cerebral desaturation, we prospectively monitored rSO(2) in 122 elderly patients undergoing major abdominal surgery with general anesthesia. Patients were randomly allocated to an intervention group (the monitor was visible and rSO(2) was maintained at > or =75% of preinduction values; n = 56) or a control group (the monitor was blinded and anesthesia was managed routinely; n = 66). Cerebral desaturation (rSO(2) reduction <75% of baseline) was observed in 11 patients of the treatment group (20%) and 15 patients of the control group (23%) (P = 0.82). Mean (95% confidence intervals) values of mean rSO(2) were higher (66% [64%-68%]) and the area under the curve below 75% of baseline (AUCrSO2(2)< 75% of baseline) was lower (0.4 min% [0.1-0.8 min%]) in patients of the treatment group than in patients of the control group (61% [59%-63%] and 80 min% [2-144 min%], respectively; P = 0.002 and P = 0.017). When considering only patients developing intraoperative cerebral desaturation, a lower Mini Mental State Elimination (MMSE) score was observed at the seventh postoperative day in the control group (26 [25-30]) than in the treatment group (28 [26-30]) (P = 0.02), with a significant correlation between the AUCrSO(2) < 75% of baseline and postoperative decrease in MMSE score from preoperative values (r(2)= 0.25, P = 0.01). Patients of the control group with intraoperative cerebral desaturation also experienced a longer time to postanesthesia care unit (PACU) discharge (47 min [13-56 min]) and longer hospital stay (24 days [7-53] days) compared with patients of the treatment group (25 min [15-35 min] and 10 days [7-23 days], respectively; P = 0.01 and P = 0.007). Using rSO(2) monitoring to manage anesthesia in elderly patients undergoing major abdominal surgery reduces the potential exposure of the brain to hypoxia; this might be associated with decreased effects on cognitive function and shorter PACU and hospital stay.

Aortic Arch Replacement Using a Trifurcated Graft: Simple, Versatile, and Safe

BACKGROUND

Hypothermic selective antegrade cerebral perfusion during aortic arch replacement may prevent adverse neurologic sequelae. It can be provided via balloon-tipped catheters or a branched graft sewn to the brachiocephalic vessels. We report a consecutive series of total arch replacement using a trifurcated graft.

METHODS

From September 1999 through October 2004, 109 patients underwent nonemergent total arch replacement using this technique. The graft, placed during a period of hypothermic circulatory arrest, was used for selective cerebral perfusion during the arch reconstruction.

RESULTS

Adverse outcomes were seen in 9 (8.3%) patients: hospital death in 5 (4.6%), and stroke in 5 (4.6%). Transient neurologic dysfunction was noted in 6 (5.5%) patients. Mean duration of hypothermic circulatory arrest was 31.2 +/- 6.6 minutes and selective cerebral perfusion was 65.3 +/- 20.9 minutes. Reoperation for bleeding was required in 3 (2.8%) patients and prolonged intubation in 15 (13.8%). Median intensive care unit stay was 3 days (interquartile range 2-4; range, 1 to 108) and hospital stay was 9 (interquartile range 8-15; range, 5 to 108).

CONCLUSIONS

The trifurcated graft technique results in low rates of perioperative mortality, temporary neurologic dysfunction, and stroke. It may reduce cerebral embolization as it requires no instrumentation of the aortic arch to establish selective cerebral perfusion and, although it mandates hypothermic circulatory arrest to place the graft, this interval is reliably brief enough to fall within accepted safe limits. This strategy leaves no residual arch tissue behind, and allows placement of an elephant trunk proximal to one or more arch vessels if anatomically indicated.

Tissue oxygenation monitoring during major pediatric surgery using transcutaneous liver near infrared spectroscopy

BACKGROUND

The aim of the study was to compare liver tissue oxygenation determined by near infrared spectroscopy (NIRS) with central venous oxygen saturation (SvO(2)) and intestinal perfusion as measured by gastric intramucosal pH (pHi) in pediatric surgical patients.

METHODS

Twenty children undergoing craniofacial surgery with expected major intraoperative blood loss were studied. NIRS tissue oxygenation index (TOI(Liver)) and pHi values were recorded. Arterial blood gas analysis and SvO(2) were assessed from periodically taken blood samples. Data are presented as ranges (median) and were compared using linear regression analysis. Sensitivity and specificity of the intra-individual changes in TOI(Liver) to predict falling SvO(2) or pHi values were calculated.

RESULTS

Patients age ranged from 0.79 to 8.27 years (1.92 years). TOI(Liver) ranged from 41.5 to 77.4% (61.5%), gastric pHi from 7.13 to 7.60 (7.37) and SvO(2) from 51 to 86% (74%). Among patients only moderate correlation was found between TOI(Liver) and SvO(2) (r = 0.594, P < 0.0001) and gastric pH(i) (r = 0.502, P < 0.0001). Intra-individual measured TOI(Liver) values, however, demonstrated close correlation with SvO(2) values (r = 0.680 to 0.976) but a varying correlation with gastric pHi values (r = 0.055 to 0.972). Sensitivity/specificity of TOI(Liver) to predict decreasing SvO(2) or gastric pHi values were 76.4/73.4% and 67.4/62.7% respectively.

CONCLUSIONS

TOI(Liver) provided a better trend monitor of central venous oxygen saturation than gastric intramucosal pH. Because of its limited sensitivity and specificity to indicate deterioration of SvO(2), liver tissue oxygenation measured by transcutaneous NIRS does not provide additional practical information for clinical management.

Non-invasive monitoring of haemoglobin concentration in paediatric surgical patients using near-infrared spectroscopy

We evaluated the near-infrared spectroscopy based tissue haemoglobin index for continuous non-invasive monitoring of haemoglobin concentration during paediatric surgery. Blood samples from 40 children (from birth to 16 years old) were analysed oximetrically. From the first blood sample the tissue haemoglobin index/haemoglobin concentration coefficient was calculated for further tissue haemoglobin index-derived haemoglobin concentrations in each patient. Comparison of corresponding values revealed a bias and precision of -0.02 and 5.41 g.l(-1), respectively. Sensitivity and specificity of tissue haemoglobin index were 73.1% and 70.0%, respectively, for predicting falling haemoglobin concentration values. Currently, the tissue haemoglobin index is not suitable for monitoring haemoglobin concentration in children undergoing surgery.

Contemporary Results of Total Aortic Arch Replacement

BACKGROUND AND AIM

Aneurysmal dilatation of the aortic arch is uncommon, and the complex anatomy involved imposes unique technical challenges. The results of surgical intervention reported from large centers are improving; however, the degree to which these results are reproducible by other surgeons is less clear. We therefore reviewed our recent experience with total aortic arch replacement.

METHODS

Between July 1, 1997 and July 1, 2001 19 patients underwent complete aortic arch replacement, with or without concomitant procedures. We retrospectively reviewed perioperative results retrieved from the computerized database and clinical records.

RESULTS

The mean age of the study population was 68 +/- 8.3 years (range 52 to 82), with women predominating (11 women, 8 men). All patients had hypertension. Patient history indicated active or past tobacco abuse in 16 patients (80%); cerebrovascular disease in 3, and peripheral vascular disease in 7 patients. Associated procedures included an elephant trunk in 12 (63%), replacement of the upper descending thoracic aorta in 5 (26%), concomitant coronary artery bypass in 5 (26%), and aortic root replacement in 3 (16%). One patient underwent replacement of the entire aorta from sinotubular ridge to iliac bifurcation in a single procedure. Brachiocephalic reconstruction with a "Y-graft" permitting early antegrade cerebral perfusion was performed in 12 patients. Retrograde cerebral perfusion was performed in ten patients (53%). Perioperatively, death occurred in two patients (11%) and stroke in two (11%).

CONCLUSIONS

With cautious application, techniques developed in high-volume centers can also achieve satisfactory results when used at centers with a more modest case volume.

Measurement of cerebral oxygenation state in anaesthetized children using the INVOS 5100 cerebral oximeter

BACKGROUND

Near-infrared spectroscopy is a developing technique for monitoring cerebral oxygenation during anaesthesia. The aim of this study was to evaluate absolute values of cerebral oxygenation during stable anaesthesia conditions in otherwise healthy children using the recently introduced INVOS 5100 cerebral oximeter with a paediatric and adult sensor and to compare them with values obtained from the NIRO 300 oximeter.

METHODS

Thirty paediatric surgical patients (aged 0.23-15.97 years) were studied during general anaesthesia with tracheal intubation and controlled ventilation. Comparative measurements of cerebral oxygenation were performed on the forehead with two probes within 10 min under stable cardiorespiratory and anaesthesia conditions. Cerebral oxygenation values (rSO2) obtained from the paediatric and adult INVOS 5100 sensors were compared with the tissue oxygenation index (TOI) obtained from the NIRO 300 cerebral oximeter using 4- and 5-cm emitter-detector separation.

RESULTS

Cerebral rSO2 values and the TOI values both showed a large range of cerebral oxygenation in the children studied (rSO2: 59-95%, TOI: 48-85%). Cerebral rSO2 values measured by the INVOS 5100, particularly with the paediatric sensor, were significantly higher than the TOI values obtained from the NIRO 300 (P < 0.0001). Agreement between the INVOS and NIRO oximeter was poor.

CONCLUSION

The large range and the poor agreement of cerebral oxygenation values between the two oximeters makes it difficult to define a normal value. Cerebral oxygenation readings by these monitors, based on one single point measurement during anaesthesia, should be viewed with caution. Actually, there may be little indication for routine use of such monitoring during general anaesthesia.

Direct visualization of minimal cerebral capillary flow during retrograde cerebral perfusion: an intravital fluorescence microscopy study in pigs

BACKGROUND

Retrograde cerebral perfusion (RCP) is used in some centers during aortic arch surgery for brain protection during hypothermic circulatory arrest. It is still unclear however whether RCP provides adequate microcirculatory blood flow at a capillary level. We used intravital microscopy to directly visualize the cerebral capillary blood flow in a piglet model of RCP.

METHODS

Twelve pigs (weight 9.7 +/- 0.9 kg) were divided into two groups (n = 6 each): deep hypothermic circulatory arrest (DHCA) and RCP. After the creation of a window over the parietal cerebral cortex, pigs underwent 10 minutes of normothermic bypass and 40 minutes of cooling to 15 degrees C on cardiopulmonary bypass ([CPB] pH-stat, hemocrit 30%, pump flow 100 mL x kg(-1) x min(-1)). This was followed by 45 minutes of DHCA and rewarming on CPB to 37 degrees C. In the RCP group the brain was retrogradely perfused (pump flow 30 mL x kg(-1) x min(-1)) during DHCA through the superior vena cava after inferior vena cava occlusion. Plasma was labeled with fluorescein-isothiocyanate-dextran for assessing microvascular diameter and functional capillary density (FCD), defined as total length of erythrocyte-perfused capillaries per observation area. Cerebral tissue oxygenation was determined by nicotinamide adenine dinucleotide hydrogen (NADH) autofluorescence, which increases during tissue ischemia.

RESULTS

During normothermic and hypothermic antegrade cerebral perfusion the FCD did not significantly change from base line (97% +/- 14% and 96% +/- 12%, respectively). During retrograde cerebral perfusion the FCD decreased highly significantly to 2% +/- 2% of base line values (p < 0.001). Thus there was no evidence of significant capillary blood flow during retrograde cerebral perfusion. The microvascular diameter of cerebral arterioles that were slowly perfused significantly decreased to 27% +/- 6% of base line levels during RCP. NADH fluorescence progressively and significantly increased during RCP, indicating poorer tissue oxygenation. At the end of retrograde cerebral perfusion there was macroscopic evidence of significant brain edema.

CONCLUSIONS

RCP does not provide adequate cerebral capillary blood flow and does not prevent cerebral ischemia. Prolonged RCP induces brain edema. However, there might be a role for a short period of RCP to remove air and debris from the cerebral circulation after DHCA because retrograde flow could be detected in cerebral arterioles.

Aortic arch repair with right brachial artery perfusion

BACKGROUND

To determine the effectiveness of unilateral selective cerebral perfusion for aortic arch repair and to discuss possible modifications to enhance technical simplicity.

METHODS

In the period between January 1996 and April 2001, 104 patients underwent aortic arch repair with the use of right brachial artery low flow (8 to 10 mL/kg per minute) antegrade selective cerebral perfusion under moderate hypothermia (26 degrees C). Mean patient age was 52 +/- 12 years. Sixty-four patients presented with Stanford type A aortic dissection, including 12 with acute dissection; 38 patients had aneurysmal dilatation of the ascending aorta and aortic arch; and 2 patients had isolated arch aneurysm. Ascending and partial arch replacement was performed in 50 patients; ascending and total arch replacement in 33 patients; ascending and descending arch replacement in 19 patients; and isolated arch replacement in 2 patients.

RESULTS

Mean antegrade cerebral perfusion time was 39 +/- 22 minutes. One patient with acute proximal dissection died because of cerebral complications. One other patient developed right hemiparesis, which resolved during the second postoperative month without sequela. Other than these 2 cases (1.9%), no other neurologic event was observed.

CONCLUSIONS

The technique of low flow antegrade selective cerebral perfusion through the right brachial artery may be used for a vast majority of aortic aneurysms and dissections requiring arch repair. This technique does not necessitate deep hypothermia, requires shorter cardiopulmonary bypass and operation times, has the advantage of simplicity, provides optimal vascular repair without time restraints and, in terms of clinical results, is as safe as other techniques for cerebral protection.

Cerebral protection: the surgeon's view

The cardiothoracic team has to be ready with a strategy that corners the preoperative to postoperative period, but the cardiothoracic surgeon has to be prepared to perform the optimal procedure by concentrating on the procedure and avoiding circulatory arrest. If it is not possible to avoid circulatory arrest the surgeon should choose the ideal cerebroprotective technique for each patient, which is not always the same technique, change the method during the procedure if necessary, and remember that cerebral protection is not the same as cerebral metabolic preservation.

Neurological Complications of Aortic Surgery

Surgery of the aortic arch involves an inherently high risk of neurological complications. A number of factors have been identified which may predispose the patient to brain injury, and various techniques employed in an attempt to counteract these are outlined. In particular the vulnerability of the brain to ischemia has led to the development of three adjunctive cerebral protective techniques, hypothermic circulatory arrest, retrograde cerebral perfusion and selective antegrade cerebral perfusion, all based upon brain cooling and metabolic inhibition. The relative merits and disadvantages of these techniques are therefore discussed. Finally, pharmacologic adjuncts and potential future developments in aortic arch surgery are discussed.

Simulation study of a selective cerebral perfusion system with a single centrifugal pump

We previously successfully developed a simple nonroller extracorporeal circulation system (NRECC). In aortic arch surgery, more than two pumps are generally used for systemic perfusion and selective cerebral perfusion (SCP); we developed a new pressure-dependent perfusion system for SCP based on our NRECC and operated by a single centrifugal pump. The cerebral perfusion line was branched from the main perfusion line, and one 15 French and two 12 French cannulae were used for SCP. The perfusion pressure was regulated with a tube occluder. Afterload was changed from 30 to 80 mm Hg, the pressure of the SCP line was increased from 80 to 200 mm Hg, and flow volume was measured. When the afterload was set at 50 mm Hg, according to the increase of perfusion from 80 to 200 mm Hg, the flow volume of the 15 French cannula increased from 280 to 950 ml/min. Under the same conditions, flow volume of the 12 French cannula increased from 160 to 560 ml/min. Sufficient flow volume of the SCP lines was obtained when the SCP line pressure was over 80 mm Hg. As a result of the increased perfusion pressure, the flow volume showed a direct increase. These findings suggest that aortic arch surgery is possible using this SCP system.