Blood Gas Management Research Articles

Enhancing Neuroprotection in Cardiac and Aortic Surgeries: A Narrative Review

Background: Neurological injury poses a significant challenge in aortic surgery, encompassing spinal cord injury from thoraco-abdominal aorta intervention or stroke post-surgery on the arch and ascending aorta. Despite ample literature and proposals, a fully effective strategy for preventing or treating neurological injury remains elusive. This narrative review aims to analyze the most common neuroprotective strategies implemented for aortic arch surgery and aortic surgery. Results: Results from the reviewed studies showed that several strategies, including deep hypothermia cardiac induction (DHCA) and cerebral perfusion techniques (retrograde cerebral perfusion, RCP, and selective anterograde cerebral perfusion, SACP) aim to mitigate these risks. Monitoring methods such as electroencephalogram (EEG), somatosensory evoked potential (SEPs), and near-infrared spectroscopy (NIRS) offer valuable insights into cerebral function during surgery, aiding in the management of hypothermia and perfusion. Pharmacological agents and blood gas management (pH stat vs. alpha stat, hematocrit level, glycemic control) are crucial in preventing post-operative complications. Additionally meticulous management of atheromatous debris is essential to minimize embolic risks during surgery. Methods: For this narrative review, PubMed, Scopus, and Medline have been used to search articles about neuroprotection strategies in aortic and aortic arch surgeries. The search was narrowed to articles between 1975 and 2024. A total of 3418 articles were initially identified to be potentially relevant for this review. A total of 66 articles were included and were found to match the inclusion criteria. Conclusions: While an overabundance of neuroprotection strategies exists for cardiac surgery, particularly in procedures involving the aorta and the arch, their efficacy varies, with some well-documented and others still under scrutiny. Further research is imperative to advance our comprehension and refine prevention techniques for cardiac-surgery-related brain injury. This is crucial given its substantial contribution to both mortality and, notably, post-operative morbidity.

Wild harbour porpoises startle and flee at low received levels from acoustic harassment device

Acoustic Harassment Devices (AHD) are widely used to deter marine mammals from aquaculture depredation, and from pile driving operations that may otherwise cause hearing damage. However, little is known about the behavioural and physiological effects of these devices. Here, we investigate the physiological and behavioural responses of harbour porpoises (Phocoena phocoena) to a commercial AHD in Danish waters. Six porpoises were tagged with suction-cup-attached DTAGs recording sound, 3D-movement, and GPS (n = 3) or electrocardiogram (n = 2). They were then exposed to AHDs for 15 min, with initial received levels (RL) ranging from 98 to 132 dB re 1 µPa (rms-fast, 125 ms) and initial exposure ranges of 0.9–7 km. All animals reacted by displaying a mixture of acoustic startle responses, fleeing, altered echolocation behaviour, and by demonstrating unusual tachycardia while diving. Moreover, during the 15-min exposures, half of the animals received cumulative sound doses close to published thresholds for temporary auditory threshold shifts. We conclude that AHD exposure at many km can evoke both startle, flight and cardiac responses which may impact blood-gas management, breath-hold capability, energy balance, stress level and risk of by-catch. We posit that current AHDs are too powerful for mitigation use to prevent hearing damage of porpoises from offshore construction.

Effectiveness of online versus in-person structured training program on arterial blood gas, electrolytes, and ventilatory management of critically ill patients

BackgroundDue to the risk of viral transmission during in-person training, a shift toward online platforms is imperative in the current pandemic. Therefore, we compared the effectiveness of an in-person interactive course with a structurally similar online course designed to improve cognitive skills among clinical health professionals in arterial blood gas analysis, management of electrolyte imbalances, and approaches to mechanical ventilation in critically ill patients.MethodsIn an observational, outcome assessor-blinded, cohort trial, group A included participants enrolled prospectively in an online course, while group B included those who took part in an in-person course (retrospective arm). The primary objective was comparison of cognitive skills through a pre and post-test questionnaire. Statistical analysis was performed using Student t-test.ResultsIn total, 435 participants were analyzed in group A, while 99 participants were evaluated in group B. The mean pre-test score was 9.48±2.75 and 10.76±2.42, while the mean post-test score was 11.94±1.90 (passing rate, 64.6%) and 12.53±1.63 (passing rate, 73.3%) in groups A and B, respectively. Group B scored significantly higher in both pre-test (P=0.001) and post-test evaluations (P=0.004). The improvement in post-test score was significantly greater (P=0.001) in group A (2.46±2.22) compared to group B (1.77±1.76). The medical specialties fared better in group B, while surgical specialties scored higher in group A. The pre-test vs. post-test scores exhibited a moderate correlation in both groups (P<0.001). The feedback survey showed a Likert score >3.5 for most points in both groups.ConclusionsThe online teaching module exhibited a significant benefit in terms of participant sensitization and knowledge sharing.

Antegrade cerebral perfusion at 25 °C for arch reconstruction in newborns and children preserves perioperative cerebral oxygenation and serum creatinine.

Antegrade cerebral perfusion (ACP) typically is used with deep hypothermia for cerebral protection during aortic arch reconstructions. The impact of ACP on cerebral oxygenation and serum creatinine at a more tepid 25 °C was studied in newborns and children. Between 2010 and 2014, 61 newborns and children (<5 years old) underwent aortic arch reconstruction using moderate hypothermia (25.0±0.9 °C) with ACP and a pH-stat blood gas management strategy. These included 44% Norwood-type operations, 30% isolated arch reconstructions, and 26% arch reconstructions with other major procedures. Median patient age at surgery was 9 days (range, 3 days-4.7 years). Cerebral oxygenation (NIRS) was monitored continuously perioperatively for 120 hours. Serum creatinine was monitored daily. Median cardiopulmonary bypass (CPB) and cross clamp times were 181 minutes (range, 82-652 minutes) and 72 minutes (range, 10-364 minutes), respectively. ACP was performed at a mean flow rate of 46±6 mL/min/kg for a median of 48 minutes (range, 10-123 minutes). Cerebral and somatic NIRS were preserved intraoperatively and remained at baseline postoperatively during the first 120 hours. Peak postoperative serum creatinine levels averaged 0.7±0.3 mg/dL for all patients. There were 4 (6.6%) discharge mortalities. Six patients (9.8%) required ECMO support. Median postoperative length of hospital and intensive care unit (ICU) stay were 16 days(range, 4-104 days) and 9 days (range, 1-104 days), respectively. Two patients (3.3%) received short-term peritoneal dialysis for fluid removal, and none required hemodialysis. Three patients (4.9%) had an isolated seizure which resolved with medical therapy, and none had a neurologic deficit or stroke. ACP at 25 °C preserved perioperative cerebral oxygenation and serum creatinine for newborns and children undergoing arch reconstruction. Early outcomes are encouraging, and additional study is warranted to assess the impact on late outcomes.

Off pump coronary artery bypass grafting in a patient with cerebrovascular disease.

Sir, Despite some reservations after its early beginning and reported successes, off pump coronary artery bypass surgery (OPCAB) is regaining widespread acceptance as a viable alternative to standard revascularisation techniques. This resurgence of interest is because cardiopulmonary bypass is still associated with many adverse systemic effects including complement activation, neurocognitive dysfunction, coagulation abnormalities, and activation of systemic inflammatory response, cerebral oedema with increased extracellular brain water noted immediately after surgery.[1] These changes are not seen with OPCAB surgery, making this more acceptable option for the patient with cerebrovascular disease. An 83-year-old hypertensive, non-diabetic male patient weighing 63 kg with a history of recent non-Q-wave myocardial infarction (MI) and transient ischaemic attack (TIA) 3 months back presented with unstable angina. All his investigations were normal except ST depression on anterolateral leads of electrocardiogram (ECG). Transthoracic echocardiogram revealed akinetic basal, posterior inter ventricular septum and inferior wall with left ventricular ejection fraction of 40%. His coronary angiogram showed single vessel disease of left anterior descending (LAD) territory. Carotid Doppler showed left internal carotid artery stenosis (30%) and right internal carotid artery stenosis (50%). In view of TIA history, his computed tomography (CT) angiogram of the head was obtained which showed multiple intracerebral aneurysms of the circle of Willis and its branches. In view of his CT angiogram and unstable angina, an urgent OPCAB was planned as neurointervention was not feasible with on-going myocardial ischaemia. Patient was premedicated and induction was facilitated with fentanyl 250 μg, thiopentone sleep dose, and intubation was performed with vecuronium bromide 8 mg. Monitoring included ECG, intra arterial blood pressure, central venous pressure (CVP), pulmonary artery pressure (PAP), pulse oximetry, temperature, end tidal CO2, arterial blood gases, blood sugar, urine output and bispectral index (BIS). After anterior left thoracotomy, left internal mammary artery to LAD anastomosis was performed on the beating heart. Haemodynamic recordings included blood pressure, 122/66 mm Hg, heart rate 82 beats/min, PAP 28/15 mm Hg, CVP 7 mm Hg and cardiac inde × 2.9 L/min/m2. The BIS level was maintained between 40 and 45. During the anastomosis, haemodynamic parameters were stable. Trendelenburg position of the patient was avoided, and transient hypotension was managed with preload augmentation with fluid transfusion and vasopressors. After shifting to the ward, the patient was assessed by a neurophysician as a routine consultation. He was discharged from the hospital on sixth post-operative-day and was readmitted after 6 weeks for clipping of the intracerebral aneurysms. Unstable angina is one of the most common life-threatening medical emergencies. It may result in death or nonfatal MI in up to 20% of patients within 30 days of the ischaemic event. Both conservative and invasive treatments for unstable angina are effective in reducing the death or MI, but the FRISC II trial recommended invasive treatment.[2] Technical advances in surgical procedures, anaesthesia, and post-operative care have improved the results of surgery for unstable angina.[3,4] Recently the benefits of OPCAB have been increasingly reported.[5] The patient in this report posed a clinical dilemma because of life-threatening intracranial pathology in the face of recent MI and unstable angina. The anaesthetic management proved challenging because of concerns about elevated intracranial pressure (ICP) and on-going myocardial ischaemia. Priority was given to the cardiac disease as is recommended by the American Heart Association/Society of Cardiovascular Anaesthesiologists guidelines of 2009. The effects of all anaesthetics and vasoactive drugs used had to be carefully considered, about cerebral blood flow and cardiac function and also the arterial blood gas management. The question of whether or not to hyperventilate the patient posed a dilemma. A balance was needed to be maintained to avoid the risk of aneurysm rupture and simultaneously maintain an adequate cerebral perfusion pressure. The decision was made to maintain the pCO2 between 30 and 40 mm Hg. There was the theoretic concern that rapid normalisation of ICP with hyperventilation could increase the transmural pressure gradient across the aneurysm wall with possibility of rupture. CVP was closely monitored as an indirect indicator of ICP. BIS monitor was used primarily to monitor the depth of anaesthesia, precise titration of anaesthetic agents and facilitate an earlier awakening, for early neurological assessment and early extubation of the patient. Stable haemodynamics was maintained throughout the procedure. The conclusion is that the OPCAB surgery is a safer option for the patient with intracerebral aneurysm undergoing coronary artery bypass grafting.

Influence of α-Stat and pH-Stat Blood Gas Management Strategies on Cerebral Blood Flow and Oxygenation in Patients Treated With Therapeutic Hypothermia After Out-of-Hospital Cardiac Arrest

In patients treated with therapeutic hypothermia after out-of-hospital cardiac arrest, two blood gas management strategies are used regarding the PaCO2 target: α-stat or pH-stat. We aimed to compare the effects of these strategies on cerebral blood flow and oxygenation. Prospective observational single-center crossover study. ICU of University hospital. Twenty-one therapeutic hypothermia-treated patients after out-of-hospital cardiac arrest more than 18 years old without history of cerebrovascular disease were included. Cerebral perfusion and oxygenation variables were compared in α-stat (PaCO2 measured at 37 °C) versus pH-stat (PaCO2 measured at 32-34 °C), both strategies maintaining physiological PaCO2 values: 4.8-5.6 kPa (36-42 torr). Bilateral transcranial middle cerebral artery flow velocities using Doppler and jugular vein oxygen saturation were measured in both strategies 18 hours (14-23 hr) after the return of spontaneous circulation. Pulsatility and resistance indexes and cerebral oxygen extraction were calculated. Data are expressed as median (interquartile range 25-75) in α-stat versus pH-stat. No differences were found in temperature, arterial blood pressure, and oxygenation between α-stat and pH-stat. Significant differences were found in minute ventilation (p = 0.006), temperature-corrected PaCO2 (4.4 kPa [4.1-4.6 kPa] vs. 5.1 kPa [5.0-5.3 kPa], p = 0.0001), and temperature-uncorrected PaCO2 (p = 0.0001). No differences were found in cerebral blood velocities and pulsatility and resistance indexes in the overall population. Significant differences were found in jugular vein oxygen saturation (83.2% [79.2-87.6%] vs. 86.7% [83.2-88.2%], p = 0.009) and cerebral oxygen extraction (15% [11-20%] vs. 12% [10-16%], p = 0.01), respectively. In survivors, diastolic blood velocities were 25 cm/s (19-30 cm/s) versus 29 cm/s (23-35 cm/s) (p = 0.004), pulsatility index was 1.10 (0.97-1.18) versus 0.94 (0.89-1.05) (p = 0.027), jugular vein oxygen saturation was 79.2 (71.1-81.8) versus 83.3% (76.6-87.8) (p = 0.033), respectively. However, similar results were not found in nonsurvivors. In therapeutic hypothermia-treated patients after out-of-hospital cardiac arrest at physiological PaCO2, α-stat strategy increases jugular vein blood desaturation and cerebral oxygen extraction compared with pH-stat strategy and decreases cerebral blood flow velocities in survivors.

Improving Cardiopulmonary Bypass: Does Continuous Blood Gas Monitoring Have a Role to Play?

The CDI™500 (Terumo Cardiovascular Systems, Ann Arbor, MI) is an in-line blood gas monitoring device that has been used in clinical practice for over a decade. Few randomized studies have evaluated the value of this device with respect to improved perfusion management. We routinely use automated continuous quality indicator programs to assess perfusion management. The aim of this study is to investigate in a prospective randomized trial the role of in-line blood gas monitoring in the improvement of blood gas management during cardiopulmonary bypass (CPB) utilizing continuous quality indicators. Patients were randomized into two groups (Control, CDI). Patients in the Control group received our standard CPB blood gas management, with intermittent blood gas results. Continuous blood gas measurements from the CDI™500 were recorded at 20-second intervals, with the perfusionist blinded to these measurements. Patients in the CDI group received standard CPB blood gas management, in addition to continuous blood gas measurements visible on the CDI™500, the alarm system activated, and the data recorded. Perfusion management for all cases was guided by institutional protocols. One hundred patients (50 in each group) were included in the study. No significant difference existed between the groups on demographic, surgical, or clinical outcomes. Blood gas levels of patients in the CDI group were able to be maintained in accordance to protocol a greater percentage of the time, e.g., pCO2management was 2% versus 20% (p= .008); this was most notable for differences between the Control and the CDI group for pCO2&gt; 45 mmHg (p= .003). Practice variation determined via statistical control charts improved for both pH and pCO2, represented by a decrease in the variation associated with practice. Continuous blood gas monitoring with the CDI™500 results in significantly improved blood gas management as determined by adherence to institutional protocols.

Brain Protection During Pediatric Cardiopulmonary Bypass

Improvements in peri- and postoperative surgical techniques have greatly improved outcomes for pediatric patients undergoing cardiopulmonary bypass (CPB) in the treatment of congenital heart defects (CHDs). With decreased mortality rates, the incidence of adverse neurological outcomes, comprising cognitive and speech impairments, motor deficits, and behavioral abnormalities, has increased in those patients surviving bypass. A number of mechanisms, including ischemia, reperfusion injury, hypothermia, inflammation, and hemodilution, contribute to brain insult, which is further confounded by unique challenges presented in the pediatric population. However, a number of brain monitoring and preventative techniques have been developed or are being currently evaluated in the practice of pediatric CPB. Monitoring techniques include electroencephalography, near-infrared as well as visible light spectroscopy, transcranial Doppler ultrasound, and emboli detection and classification quantitation. Preventative measures include hypothermic perfusion techniques such as deep hypothermic circulatory arrest, low-flow CPB, blood gas management, and pharmacologic prophylaxes, among others. The present review summarizes the principles of brain insult, neurodevelopmental abnormalities, monitoring techniques, methods of prevention, as well as preexisting morbidities and risk factors in pediatric CPB, with a focus on brain protection. Clinical and translational research is presented with the aim of determining methods that may optimize neurological outcomes post CPB and guiding further study.

Jugular Venous Oxygenation During Hypothermic Cardiopulmonary Bypass in Patients at Risk for Abnormal Cerebral Autoregulation: Influence of α-Stat Versus pH-Stat Blood Gas Management

In a prospective, randomized study of cardiac surgical patients at risk for impaired cerebral blood flow autoregulation, we compared alpha-stat and pH-stat blood gas management. The 40 patients enrolled had age >70 yr, diabetes, prior stroke, or uncontrolled hypertension. During hypothermia and early rewarming, jugular oxygen tensions were significantly lower in alpha-stat patients (n = 12) than pH-stat patients (n = 19; P < 0.05). During rewarming, jugular venous desaturation (i.e., SjvO(2) <50%) occurred in 6 of 12 alpha-stat patients, but no pH-stat patients (P = 0.0006). Patients at risk for poor cerebral autoregulation have higher oxygen tensions and saturations if pH-stat blood gas management is used during cardiopulmonary bypass.

Perioperative issues due to long-standing lung collapse during repair of a large ascending aortic aneurysm

Acute lung collapse during open-heart surgery may potentially lead to problems such as inadequate gas exchange, increased pulmonary vascular resistance, increased afterload to the right ventricle, and difficulty in weaning from cardiopulmonary bypass (CPB). Therefore, expansion of the lungs is ensured prior to separation from CPB. We report the inability to manually expand a chronically collapsed lung during the repair of ascending aortic aneurysm. The collapsed lung did not pose difficulty in separation from CPB and in blood gas management during the perioperative period. We discuss perioperative management issues in such situations.

Anesthetic Management for the Pediatric Patient Undergoing Deep Hypothermic Circulatory Arrest

Early definitive repair of complex congenital heart defects is now advocated. For the completion of many of these repairs, the use of deep hypothermic circulatory arrest (DHCA) is an absolute necessity. Unfortunately, there is undeniable neurologic morbidity, as well as other complications associated with DHCA. Anesthesiologists can aid in minimizing these unfortunate complications with the appropriate anesthetic management. Areas of current controversy in managing pediatric patients undergoing DHCA, which will be covered in this article, include cardiopulmonary bypass strategies (low-flow cardiopulmonary bypass versus DHCA), arterial blood gas management, hemodilution effects, glucose management, and the use of steroids, barbiturates, and antifibrinolytics. Every institution varies in their techniques, and there is always some new insight to be gained from discussion of these differences. At this time, anesthesiologists and surgeons alike are striving to gain further understanding of what truly occurs with the use of DHCA and in turn apply this clinically to provide better care for all pediatric patients undergoing this unique management.

Right Ventricle–to–Pulmonary Artery Conduit Versus Blalock-Taussig Shunt: A Hemodynamic Comparison

A comprehensive assessment of 48 hour postoperative hemodynamics in neonates randomized to the right ventricle-to-pulmonary artery (RV-PA) conduit or modified Blalock-Taussig (BT) shunt for stage 1 palliation of hypoplastic left heart syndrome was performed to determine the potential benefits of the modified technique. Randomization to either RV-PA conduit or BT shunt was stratified by surgeon and the presence of aortic atresia. The designated procedure was performed by using hypothermic cardiopulmonary bypass with phenoxybenzamine, continuous cerebral perfusion, pH-stat blood gas management, and continuous postoperative venous oximetry. Differences between treatments were analyzed by time-series generalized least-squares regression, chi2 tests, two-way repeated measures analysis of variance, and the Levene variance ratio test for variability in parameters, as appropriate. All patients underwent the procedure to which they were randomized. There were no differences in age, weight, deep hypothermic circulatory arrest, or cardiopulmonary bypass times between patients receiving the BT shunt (n = 8) or the RV-PA conduit (n = 9). There was one early and one late death in the RV-PA conduit group, and one interstage death in the BT shunt group. Other than diastolic blood pressure (39 mm Hg in BT shunt versus 46 mm Hg in RV-PA conduit, p < 0.001), there were no differences in the mean values of arterial saturation, venous oximetry, mean arterial blood pressure, pulmonary-to-systemic flow ratio (Qp/Qs), or any other physiologic or inotropic support variable between groups. The variability of physiologic values related to pulmonary blood flow was greater in the RV-PA group (Qp/Qs coefficient of variation, 0.91 versus 2.50, p < 0.001). In this randomized prospective study, no hemodynamic benefits of the RV-PA modification for stage 1 palliation of hypoplastic left heart syndrome were found. Pulmonary blood flow was more variable, and the diastolic blood pressure was higher. These findings did not influence indicators of systemic oxygen delivery with our afterload reduction strategy.

Normoxia vs. Hyperoxia: Impact of Oxygen Tension Strategies on Outcomes for Patients Receiving Cardiopulmonary Bypass for Routine Cardiac Surgical Repair

Oxygen pressure field theory (OPFT) was originally described in the early 1900s by Danish physiologist, Dr. August Krogh. This revolutionary theory described microcirculation of blood gases at the capillary level using a theoretical cylindrical tissue model commonly referred to as the Krogh cylinder. In recent years, the principles and benefits of OPFT in long-term extracorporeal circulatory support (ECMO) have been realized. Cardiac clinicians have successfully mastered OPFT fundamentals and incorporated them into their clinical practice. These clinicians have experienced significantly improved survival rates as a result of OPFT strategies. The objective of this study was to determine if a hyperoxic strategy can lead to equally beneficial outcomes for short-term support as measured by total ventilator time and total length of stay in intensive care unit (ICU) in the cardiopulmonary bypass (CPB) patient at a private institution. Patients receiving traditional blood gas management while on CPB (group B,n= 17) were retrospectively compared with hyperoxic patients (group A,n= 19). Hyperoxic/OPFT management was defined as paO2values of 300–350 mmHg and average VSAT&gt; 75%. Traditional blood gas management was defined as paO2values of 150–250 mmHg and average VSAT&lt; 75%. No significant differences between treatment groups were found for patient weight, CPB/AXC times, BSA, pre/post Hgb, pre/post-platelet (PLT) counts, pre/post-creatinine levels, pre/post-BUN, UF volumes, or CPB urine output. Additionally, no significant statistical differences were found between treatment groups for total time in ICU (T-ICU) or total time on ventilator (TOV). Hyperoxic management strategies provided no conclusive evidence of outcome improvement for patients receiving CPB for routine cardiac surgical repair. Additional studies into the impact of hyperoxia in short-term extracorporeal circulatory support are needed.

Blood Gas Strategies and Management during Pediatric Cardiopulmonary Bypass

Blood gas management during hypothermic cardiopulmonary bypass may be corrected by pH stat or alpha stat strategy. The pH stat philosophy is to maintain the blood pH constant at any temperature. Carbon dioxide must be introduced to the oxygenator in order to maintain the pH and pCO2 during hypothermic cardiopulmonary bypass. Conversely, during alpha stat blood gas management pH is maintained according to 37 degrees C despite the patient temperature. Alpha stat management preserves intracellular pH and autoregulation of cerebral vasculature by following the natural shift of the oxyhemoglobin dissociation curve. In-line blood gas analysis is a practical tool in assessing adequate blood gas management, because this technology provides immediate detection for modification of air/oxygen/carbon dioxide parameters. Results from several studies favor the pH stat strategy during neonatal cardiopulmonary bypass. This strategy increases tissue oxygenation and cerebral blood flow while cooling. Data also suggest that pH stat management results in better outcomes with shorter ventilation times and intensive care unit stays after pediatric cardiac surgery.

Performance of automated air tonometry under hypothermia

Intestinal tonometry is used during hypothermic cardio-pulmonary bypass surgery to assess splanchnic perfusion. In an in vitro set-up the performance of automated air tonometry (TONOCAP) was tested for normo- and hypothermia. A 14-FG tonometry catheter was built into a testing chamber (100 cm(3)) perfused with blood from a cardio-pulmonary bypass circuit with P(a)co(2) held at 5.6-5.8 kPa (alpha-stat). P(r)co(2) from the balloon of the tonometry catheter was measured at intervals of 10 min at 37 degrees C and at 25 degrees C by the TONOCAP. Bias (precision) of P(r)co(2) - P(a)co(2 alpha-stat) and P(r)co(2) -P(a)co(2 pH-stat) at 37 degrees C blood temperature were low at 0.23 kPa (0.21) each. Tonometrically measured P(r)co(2) at 25 degrees C significantly differed from P(a)co(2 alpha-stat) bias (precision) of 2.00 kPa (0.11) but was similar to P(a)co(2 pH-stat) (0.30 kPa (0.11)). P(r)co(2) values as measured by the TONOCAP represent pH-stat approach. Identical blood gas management (pH- or alpha-stat) should be used for calculation of mucosal-arterial CO(2) difference (P(r-a)co(2) gap) or calculation of intramucosal pH.

Arterial blood gas management during cardiopulmonary bypass.

This study sought to investigate the effects of α-stat and pH stat regimens on cardiac outcome during moderate hypothermic cardiopulmonary bypass. 100 patients undergoing elective coronary artery bypass grafting (CABG) were randomly assigned with respect to the target value for PaCO(2) during cardiopulmonary bypass (CPB) into 2 groups. In 50 patients the target PaCO(2) was 40 mmHg, measured at a standard electrode temperature of 37°C while in the other 50 patients the target PaCO(2) was 40 mmHg, corrected to the patients nasopharyngeal temperature (lowest value reached: 32±0.5°C). There were no significant differences between groups with regards to cardiac outcome such as appearance of new 'Q' waves on the electrocardiogram, postoperative creatinine kinase-MB fraction, systemic vascular resistance (SVR), cardiac index (Cl), need for inotropic or intra-aortic balloon pump support and the length of postoperative ventilation or intensive care unit stay. These findings support the hypothesis that CO(2) management during CPB at moderate hypothermia has no clinically significant effect on cardiac outcome.

Ex vivo evaluation of a new neonatal/infant oxygenator: comparison of the Terumo CAPIOX® Baby RX with Dideco Lilliput 1 and Polystan Safe Micro in the piglet model

A newly developed neonatal and infant oxygenator with a nonheparin biocompatible polymer coating, low priming volume (43 mL), high oxygen transfer, wide operating range (<1.5 L/min) and low pressure drop represents a promising solution for cardiac surgery in neonates and infants. We compared the new CAPIOX Baby RX, Terumo (BRX) with two commonly used neonatal oxygenators: Dideco Lilliput 1 (DL1) and Polystan Safe Micro (PSM) in a piglet model. Fifteen piglets (5.6 +/- 1.3kg) were placed on standardized cardiopulmonary bypass (CPB) for 6 hours using one of the three oxygenators (n = 5 in each group). After 120 min, the system was cooled to 25 degrees C for 60 min and then returned to normothermia. Arterial and venous blood gas data and temperature were recorded continuously by a CDI500 System (Terumo). Pressure drop, FiO2 and gas flow were recorded. Blood samples were taken before CBP, after 10 min, before and after cooling, and at the end. Total blood counts, thrombin-antithrombin complex and plasma-free haemoglobin (PfHb) were measured. All oxygenators showed acceptable performance for the duration of CPB. The BRX had lower mean gas flow (0.33 +/- 0.05 L/min) and FiO2 (0.43 +/- 0.02%) throughout CPB than the DL1 (1.14 +/- 0.25 L/min, p = 0.006 and 0.60 +/- 0.02%, p = 0.009, respectively) or the PSM (1.47 +/- 0.87 L/min and 0.54 +/- 0.08%, p = ns). Pressure drop in the BRX group ranged from 12 to 22 mmHg. This was significantly lower than in the DL1 group (39-65 mmHg, p = 0.005). In the PSM group, values ranged between 24 and 33 mmHg (p = ns). The increase in PfHb at six hours was significantly lower in the BRX (11.3 +/- 4.2 ng/dL) versus the DL1 (42.2 +/- 6.1 ng/dL, p = 0.004) and the PSM (56.7 +/- 15.5 ng/dL, p = 0.045). The BRX is as safe as the DL1 and the PSM, with superior performance in pressure drop, efficient blood gas management and lower haemolysis. The BRX exhibited the lowest prime, hold-up volume and breakthrough time.

Aortic Valve Replacement for a Patient with Essential Thrombocythemia: A Case Report

A 51-year-old male patient with 3+ aortic insufficiency, hepatitis C, osteomyelitis right foot, and a preoperative platelet count 1.3 million/mm3 required cardiopulmonary bypass (CPB). Essential thrombocythemia is a relatively unknown entity with the utilization of CPB. After consulting with the surgeon, an anesthesiologist and another perfusionist, a team approach was used to discuss treatment for this patient during CPB. The treatment consisted of exchange transfusions, autotransfusion techniques, and current protocol for blood gas management. No incidence of hypercoagulability was observed during this procedure or postoperatively. Based on current knowledge of pathophysiology and review of the literature, plateletpheresis should be the current management of essential thrombocythemia.

The thoracic aorta

This article summarizes current concepts in the surgical management of a variety of conditions of the thoracic aorta. The emphasis is on explaining in broad terms the particular difficulties in managing the operative set-up to prevent neurological injury. Acute aortic dissection, and aneurysms of the arch and descending aorta are used to illustrate this. Aortic root pathology in dissection, and its significance for the required repair, is outlined. The techniques to protect the brain during interruption of its normal blood supply in arch repair are outlined – hypothermia with varying blood gas management, antegrade and retrograde selective perfusion. The risk to blood supply of the spinal cord in replacement of the descending aortic is discussed. A range of techniques to reduce this risk is described: partial bypass, cerebrospinal fluid drainage, intercostals inclusion and expeditious surgery.

Modified ultrafiltration may not improve neurologic outcome following deep hypothermic circulatory arrest.

Modified ultrafiltration (MUF) improves systolic blood pressure and left ventricular performance, as well as lowering transfusion requirements, after cardiopulmonary bypass (CPB). MUF has also been shown to enhance acute cerebral metabolic recovery after deep hypothermic circulatory arrest (DHCA), but whether this improves neurologic outcome is unknown. Sixteen neonatal piglets underwent CPB and 90 min of DHCA. The hematocrit was maintained between 25 and 30%. Alpha-stat blood gas management was used. After separation from CPB, animals were randomized to 15 min of MUF (n = 8) or no intervention (n = 8). Neurologic injury was assessed with behavior scores and histologic examination. Standardized behavior scores were obtained on post-operative days 1, 3, and 6 (0 = no deficit to 95 = brain death). The percentage of injured neurons by hematoxylin and eosin staining and the degree of reactive astrocytosis by glial filbrillary acidic protein (GFAP) immunohistochemistry were assessed to determine histologic scores in the neocortex and hippocampus (0 = no injury to 4 = diffuse injury). There were no statistically significant differences between groups during CPB. After MUF, the hematocrit was significantly higher (40% +/- 5.7 vs. 28% +/- 3.9, P < 0.001). There were no significant differences in behavior scores between groups (p > 0.1). There was resolution of deficits by day 6 in all animals. Neuronal injury was present in 81% (13/16) of the animals with no statistically significant differences between groups in incidence or severity. Use of MUF after DHCA does not prevent neuronal injury or improve neurologic outcome in this neonatal swine model.