Top ten priorities for anesthesia and perioperative research: a report from the Canadian Anesthesia Research Priority Setting Partnership.

PURPOSE: The purpose of the Canadian Anesthesia Research Priority Setting Partnership (CAR PSP) was to identify a top ten list of shared priorities for research in anesthesia and perioperative care in Canada. METHODS: We used the methods of the James Lind Alliance to involve patients, caregivers, healthcare professionals, and researchers in determining the research priorities in Canada. In a first survey, participants submitted questions that they want research to answer about anesthesia and perioperative care. We summarized those responses into a longlist of questions. We reviewed the literature to see if any of those questions were already answered. In a second survey, participants chose up to ten questions from the longlist that they thought were most important to be answered with research. From that list, the highest ranking questions were discussed and assigned a final rank at an in-person workshop. RESULTS: A total of 254 participants submitted 574 research suggestions that were then summarized into 49 questions. Those questions were checked against the literature to be sure they were not already adequately addressed, and in a second survey of those 49 questions, participants chose up to 10 that they thought were most important. A total of 233 participants submitted their priorities, which were then used to choose 24 questions for discussion at the final workshop. At the final workshop, 22 participants agreed on a top ten list of priorities. CONCLUSION: The CAR PSP top ten priorities reflect a wide variety of priorities captured by a broad spectrum of Canadians who receive and provide anesthesia care. The priorities are a tool to initiate and guide patient-oriented research in anesthesia and perioperative care.

RéSUMé: OBJECTIF: L'objectif du Partenariat canadien pour l'établissement des priorités de la recherche en anesthésie (CAR-PSP) était d'établir une liste des dix principales priorités pour la recherche sur les soins anesthésiques et périopératoires au Canada. MéTHODES: Nous avons utilisé la méthodologie de la James Lind Alliance pour impliquer des patients, des aidants, des professionnels de la santé et des chercheurs afin de déterminer quelles étaient les priorités en matière de recherche au Canada. Dans une première enquête, les participants ont envoyé des questions sur les soins anesthésiques et périopératoires auxquelles ils voulaient que la recherche réponde. Nous avons résumé ces envois par une liste exhaustive de questions. Nous avons passé en revue les publications pour voir s'il existait déjà des réponses à ces questions. Dans une deuxième étude, les participants ont choisi dans la liste jusqu'à dix questions qui leur semblaient les plus importantes et pour lesquelles la recherche devrait fournir des réponses. À partir de cette liste, les questions les mieux classées ont été discutées et un classement définitif leur a été attribué au cours d'un atelier où tous les participants étaient présents en personne. RéSULTATS: Au total, 254 participants ont envoyé 574 suggestions de recherche qui ont été résumées en 49 questions. La littérature a été examinée pour s'assurer que ces questions n'avaient pas déjà reçu des réponses adéquates, et dans une seconde étude, les participants ont choisi jusqu'à 10 questions qu'ils jugeaient les plus importantes parmi ces 49 questions. Au total, 233 participants ont communiqué leurs priorités qui ont alors servi à choisir 24 questions ouvertes pour la discussion dans un atelier final. Dans cet atelier, 22 participants se sont mis d'accord sur une liste des dix principales priorités. CONCLUSION: Les dix principales priorités du CAR-PSP sont le reflet d'un grand éventail de priorités venant de Canadiens de tous horizons qui reçoivent ou fournissent des soins d'anesthésie. Ces priorités sont un outil permettant d'entamer et de guider une recherche axée sur le patient dans le domaine des soins anesthésiques et périopératoires.

A medical mystery of complex regional pain syndrome.

Complex regional pain syndrome (CRPS) is a condition of neuropathic pain, which is characterized by significant autonomic and inflammatory features. CRPS occurs in patients who have limb surgery, limb fractures, or trauma. Many patients may have pain resolve within twelve months of the inciting incident; however, a small subset progresses to the chronic form. This transitional process often happens by changing from warm CRPS with dominant inflammatory phase to cold CRPS, in which autonomic characteristics or manifestations dominate. Several peripheral and central mechanisms are involved, which might vary among individuals over a period of time. Other contributors include peripheral and central sensitization, autonomic alterations, inflammatory and immune changes, neurochemical changes, and psychological and genetic factors. Although effective management of the chronic CRPS form is often challenging, there are a few high quality randomized controlled trials that support the efficacy of the most commonly used therapeutic approaches.

The role of acetylcholinesterase inhibitors such as neostigmine and rivastigmine on chronic pain and cognitive function in aging: A review of recent clinical applications.

Chronic pain in patients with Alzheimer's disease or dementia is a complex issue in the medical field; these patients suffer from the common causes of chronic pain, especially in geriatric medicine. To ensure the correct type and level of given treatment, medical care should be taken to avoid the contribution of chronic pain and cognitive impairment in the elderly population. Acetylcholinesterase inhibitors (AChE-Is) have been proven as an efficient therapeutic resource for significant improvement in dementia of Alzheimer's disease and chronic pain due to the fact that cholinergic deficit is considered as an early finding in cognitive impairment and persisting pain. Some AChE-Is are investigated here in terms of treatment of dementia and chronic pain management. Neostigmine has been used as an adjunct analgesic in the postoperative period and in combination with other analgesic medications in an intrathecal approach. Rivastigmine has, over the past ten years, become the approved agent for the management of dementia of mild to moderate Alzheimer's disease and has gained approval for treating different types of non-Alzheimer's dementia. In this review, we will focus on the two types of AChE-Is (rivastigmine and neostigmine) in the development of their clinical use and their respective mechanisms of actions on improving cognitive function and managing chronic pain.

Nonanesthetic Effects of Ketamine: A Review Article.

Ketamine is considered a dissociative anesthetic medication, and it is commonly administered by a parenteral route. It works mainly by blocking the N-methyl-D-aspartate receptor. It inhibits the voltage-gated Na and K channels and serotonin and dopamine reuptake; also, it affects specific receptors, such as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, and aminobutyric acid A receptors. Ketamine appears to have particular mechanisms that are potentially involved during analgesic induction, including enhancing of descending inhibition and antiinflammatory effects. More recently, it has been shown that ketamine has potential in clinical practice for the management of chronic pain, cognitive function, depression, acute brain injury, and disorders of the immune system.

Tetrodotoxin for Moderate to Severe Cancer-Related Pain: A Multicentre, Randomized, Double-Blind, Placebo-Controlled, Parallel-Design Trial.

OBJECTIVE: This study evaluated subcutaneous injections of tetrodotoxin (TTX) for the treatment of moderate to severe, inadequately controlled cancer-related pain. METHODS: Eligible patients were randomized to receive TTX (30 µg) or placebo subcutaneously twice daily for four consecutive days. Efficacy was assessed using pain and composite endpoints (including pain and quality of life measures), and safety was evaluated using standard measures. RESULTS: 165 patients were enrolled at 19 sites in Canada, Australia, and New Zealand, with 149 patients in the primary analysis "intent-to-treat" population. The primary analysis supports a clinical benefit of TTX over placebo based on the pain endpoint alone with a clinically significant estimated effect size of 16.2% (p = 0.0460). The p value was nominally statistically significant after prespecified (Bonferroni Holm) adjustment for the two primary endpoints but not at the prespecified two-sided 5% level. The mean duration of analgesic response was 56.7 days (TTX) and 9.9 days (placebo). Most common adverse events were nausea, dizziness, and oral numbness or tingling and were generally mild to moderate and transient. CONCLUSIONS: Although underpowered, this study demonstrates a clinically important analgesic signal. TTX may provide clinically meaningful analgesia for patients who have persistent moderate to severe cancer pain despite best analgesic care. This clinical study is registered with ClinicalTrials.gov (NCT00725114).

Erythropoietin and Nonhematopoietic Effects.

Erythropoietin (EPO) is the main regulator of red blood cell production. Since the 1990s, EPO has been used for the treatment of anemia associated with end-stage renal failure and chemotherapy. The erythropoietin receptors were found on other organs such as the brain, spinal cord, heart and skin. In addition, it has been shown that many tissues produce and locally release EPO in response to hypoxic, biochemical and physical stress. In cellular, animal and clinical studies, EPO protects tissues from ischemia and reperfusion injury, has antiapoptotic effects and improves regeneration after injury. In this article, we mainly review the nonhematopoietic effects and new possible clinical indications for EPO.

Neuroprotective Effect of Erythropoietin in Postoperation Cervical Spinal Cord Injury: Case Report and Review.

INTRODUCTION: New research shows shown that erythropoietin has neuro-protective effects. In preclinical trial and human clinical trials, it was demonstrated that erythropoietin is effective treatment for spinal cord injury. Early administration of medications after injury increases the hope of attenuating secondary damage and maximizing an improved outcome. CASE PRESENTATION: A 42-year-old female patient presented with gait instability and progressive weakness in her right leg over a 6-year period. She was diagnosed as myelomalacia and was candidate for cervical discectomy. After surgery, she suffered from right hemiplegia due to spinal cord injury that did not respond well to routine treatment. Darbepoetin alpha (Aranesp) 100 mcg, subcutaneous daily for three days, was added to the patient's treatment seven days after trauma and resulted in rapid improvement. The patient recovered progressively and was discharged from the hospital ten days after erythropoietin therapy. CONCLUSIONS: This case report supports the beneficial role of erythropoietin in function, maintenance, and recovery of neurons. Erythropoietin is a double-edge sword, as long-term erythropoietin therapy has some complications, like thromboembolism and stroke. Recent studies suggested that erythropoietin should be given as single high dose to exert a rapid neuro-protective effect with minimal hematopoietic side effects. We believe that the effects and other adverse consequences of erythropoietin and its non-erythropoietic derivatives should be evaluated in clinical trials.

Efficacy of an intrathecal multidrug infusion for pain control in older adults and in end-stage malignancies: A report of three cases.

The aim of the present study was to explore the effectiveness of an alternative method to manage pain based on a time-limited intrathecal (IT) infusion of an analgesic medication mixture. Three patients (69, 64 and 94 years of age) with intractable and poorly controlled pain due to bed sores, pelvic metastatic mass, and thoracic vertebra and rib fractures, respectively, were treated. Daily doses of opioids could not be increased due to side effects. An IT catheter (20 G) was placed by percutaneous approach in the lumbar area while advancing toward the thoracic region, and was then tunnelled and fixed subcutaneously. It was connected to an external infusion pump with a mixture of bupivacaine 1 mg/mL, naloxone 0.02 ng/mL, ketamine 100 µg/mL, morphine 0.01 mg/mL and clonidine 0.75 µg/mL. The starting rate was 1 mL/h. The pain was mostly controlled at a rate of <1 mL/h. Opioid consumption was reduced dramatically. The catheter was kept in place for one month in the first and third patients, and for six months in the second patient, until his death. Major side effects, such as hypotension, constipation, muscle weakness, sphincter dysfunction, and cognitive or mood deterioration, were not observed with this approach. One patient experienced a urinary tract infection followed by sepsis and meningitis, which was cured by antibiotics. The catheter was removed in this patient. IT infusion with a low-concentration multidrug mixture could be considered as an alternative modality for intractable pain relief in older adults or in malignancies.

Update on the pathogenesis of complex regional pain syndrome: role of oxidative stress.

PURPOSE: Complex regional pain syndrome (CRPS) is a chronic inflammatory pain syndrome that affects one or more extremities of the body. It is characterized by burning pain and abnormalities in the sensory, motor, and autonomic nervous systems. This review illustrates how oxidative stress and nuclear factor erythroid 2-related factor (Nrf2) activation might contribute to understanding the etiopathogenesis of CRPS. PRINCIPAL FINDINGS: The precise cause of CRPS remains unclear, and current treatments are not effective in many patients. The mechanism underlying CRPS may differ across patients and even within a single patient over time. Inflammatory and neuronal mechanisms have been suggested as key contributors to CRPS. Recent evidence demonstrates that oxidative stress is associated with clinical symptoms in patients with CRPS-I. Oxidative stress plays a key role in CRPS pathogenesis. The Nrf2 factor is a master regulator of the transcription of multiple antioxidants, which protects against oxidative stress and inflammation by inducing antioxidant and detoxifying genes through binding with an antioxidant response element. It has antinociceptive effects against inflammatory pain in an animal model. CONCLUSION: This review summarises the effect of oxidative stress and mitochondrial dysfunction in the pathogenesis of CRPS. It also addresses the question of whether there is a potential role for Nrf2 (activated by pharmacological or nutritional activators) in alleviating the clinical features of CRPS or preventing its progression.

Anti-inflammatory effect of oxytocin in rat myocardial infarction.

While an increasing amount of evidence demonstrates the homeostatic functions of the cardiac oxytocin (OT) system, less is known about the role of this hormone in the injured heart. The current study examined the effect of OT infusion on cell apoptosis, expression of proliferating cell nuclear antigen (PCNA) and inflammation in the acute and subacute phases of myocardial infarction (MI). Prior MI male Sprague-Dawley rats were infused subcutaneously with OT 25 or 125 ng/(kg h) for 3 or 7 days. Saline-treated MI and sham-operated rats served as controls. Echocardiography and analysis of cardiac sections were used to disclose OT actions. Left ventricular fractional shortening, estimated to be 46.0 +/- 1.8% in sham controls, declined to 21.1 +/- 3.3% in vehicle-treated MI rats and was improved to 34.2 +/- 2.1 and to 30.9 +/- 2.5% after treatment with OT 25 and 125 ng/(kg h), respectively. OT infusion resulted in: (1) increase of cells expressing PCNA in the infarct zone, diminished cell apoptosis and fibrotic deposits in the remote myocardium; (2) suppression of inflammation by reduction of neutrophils, macrophages and T lymphocytes; (3) depression of the expression of proinflammatory cytokines tumor necrosis factor-alpha and interleukin-6 with promotion of transforming growth factor-beta. OT treatment reduced expression of atrial and brain natriuretic peptides in the infarcted ventricle, as well as the concentration of both peptides in the circulation. These results indicate that continuous OT delivery reduces inflammation and apoptosis in infarcted and remote myocardium, thus improving function in the injured heart.

The effects of surgery and anesthesia on memory and cognition.

This chapter describes current findings from the research into postoperative cognitive dysfunction (POCD) following cardiac and non-cardiac surgery in older adults. The evidence suggests that a significant proportion of patients show POCD in the early weeks following surgery and anesthesia. Specific domains of cognition are affected, especially memory. Much less evidence supports the presence of POCD several months or years after surgery, suggesting that POCD may be transient. However, several methodological issues make it difficult to compare findings across studies. Increasing age is among the most consistently reported patient-related risk factor. Other factors more directly related to the surgery and anesthesia are likely to contribute to the pathogenesis of POCD, including inflammatory processes triggered by the surgical procedure. Animal studies have provided valuable findings otherwise not possible in human studies; these include a correlation between the inflammatory response in the hippocampus and the development of POCD in rodents.

Increased alveolar and plasma gelatinases activity during postpump syndrome: Inhibition by inhaled nitric oxide.

Postpump syndrome is associated with systemic inflammation. Matrix metalloproteinases (MMP)-2 and -9 contribute to proinflammatory and platelet-activator reactions. Nitric oxide (NO) is involved in the regulation of MMPs. The objectives of our study were to investigate the intensity of inflammation induced by 3 different surgical procedures, the effects of inflammation on the activity of MMPs, and the regulation of inflammation by inhaled NO (20 ppm). Inhaled NO was initiated immediately after tracheal intubation and maintained for the total duration of the experiments. Thirty pigs were equally randomized into 6 groups [sham; sham + NO; cardiopulmonary bypass; bypass + NO; bypass + lipopolysaccharide (1 microg/kg for 50 min); bypass + lipopolysaccharide + NO] and animals were subjected to anesthesia and mechanical ventilation up to 24 h. The levels of MMP-2 and MMP-9 in plasma and bronchoalveolar lavage were measured using zymography. Bypass resulted in a time-dependent rise in MMP activity, an effect potentiated by lipopolysaccharide. Inhaled NO attenuated the effects of bypass + lipopolysaccharide. These results confirm that MMP-2 and MMP-9 are associated with the inflammatory process causing the postpump syndrome. Preemptive and continuous administration of inhaled NO helps to prevent increased MMP-2 and MMP-9 activity.

Pre-emptive and continuous inhaled NO counteracts the cardiopulmonary consequences of extracorporeal circulation in a pig model.

Cardiopulmonary bypass (CPB) activates a systemic inflammatory response characterized clinically by alterations in cardiovascular and pulmonary function. The aim of this study was to measure the cardiopulmonary consequences in sham-operated pigs, and in animals subjected to CPB in the presence or absence of lipopolysaccharide (LPS). We also investigated, if the perioperative administration of inhaled NO exerts significant cardiopulmonary effects in an anaesthetized and mechanically ventilated pig model of extracorporeal circulation. Thirty pigs were randomized into six equal groups (sham; sham+INO; CPB; CPB+INO; CPB+LPS; CPB+LPS+INO) and subjected to anaesthesia with mechanical ventilation for up to 24h. We found that CPB+LPS group has the highest degree of lung injury. We also demonstrated that there was a significant difference on the cardiovascular parameters (heart rate, central venous pressure, stroke volume index, and mean systemic arterial blood pressure) between the CPB groups and the sham groups. The deteriorated lung mechanics was associated with a decrease in active subfraction of surfactant (LA) with time during the procedure (P=0.0003), on which inhaled NO had only an initial beneficial effect. In our model, inhaled NO had no long-term beneficial effect on lung mechanics and surfactant homeostasis despite improving lung haemodynamics, inflammation, and oxygenation. We conclude from this study that the use of pre-emptive and continuous inhaled NO therapy has protective and safe effects against lung ischemia/reperfusion associated with CPB.

Postoperative cognitive dysfunction after cardiac surgery.

Prolonged postoperative cognitive dysfunction (POCD) is reported to occur frequently after cardiac surgery. However, it is rarely assessed in routine clinical practice and receives little attention. Although the cerebral consequences of cardiopulmonary bypass have been measured clinically, insights into the resulting molecular and pathologic events within the brain have only begun to be investigated. POCD is likely to impair quality of life and constitutes a large burden on society when elderly patients prematurely lose their independence. Numerous studies have reported that neurocognitive deficit is associated with heightened mortality, increased length of hospital stay, and discharge to a nursing home. This is linked with a tremendous demand for health-care resources. Because of the magnitude of the clinical problem, serious consideration must be directed toward understanding its etiology and the development of neuroprotective strategies. Clearly identifying the mechanisms of POCD is challenging. The purpose of this review is to discuss recent developments in our understanding of the pathophysiologic mechanisms, prevention, and treatments that have been designed to ameliorate brain dysfunction after cardiac surgery.

Effects of inhaled nitric oxide on inflammation and apoptosis after cardiopulmonary bypass.

BACKGROUND: Cardiopulmonary bypass (CPB), a procedure often used during cardiac surgery, is associated with an inflammatory process that leads to lung injury. We hypothesized that inhaled nitric oxide (INO), which has anti-inflammatory properties, possesses the ability to modulate lung cell apoptosis and prevent CPB-induced inflammation. METHODS: Twenty male pigs were randomly classified into four groups: sham, sham plus INO, CPB, and CPB plus INO. INO (20 ppm) was administered for 24 h after anesthesia. CPB was performed 90 min into INO treatment. BAL fluid and blood were collected at time 0 (before CPB), at 4 h after beginning CPB, and 24 h after beginning CPB (T24). RESULTS: At T(24), BAL interleukin (IL)-8 levels and neutrophil percentages were elevated significantly in the CPB group. At T(24), INO reduced IL-8 concentrations and attenuated the increase of neutrophil percentage in the CPB-plus-INO group. Nitrite-plus-nitrate (NOx) concentrations were decreased significantly in groups without INO. Moreover, animals treated with INO showed higher rates of pulmonary apoptosis compared to their respective control groups except for the sham-plus-INO group, in which they were diminished. CONCLUSION: These results demonstrate that NOx production is reduced after CPB, and that INO acts as an anti-inflammatory agent by decreasing neutrophil numbers and their major chemoattractant, IL-8. INO also increases cell apoptosis in the lungs during inflammatory conditions, which may explain, in part, how it resolves pulmonary inflammation.

Nitric oxide, cell signaling and cell death.

Nitric oxide (NO) is an important bioregulatory molecule in the nervous, immune and cardiovascular systems. NO participates in the regulation of the daily activities of cells as well as in cytotoxic events. It possesses a controversial effect on cell viability by acting both as a protection against apoptogenic stimuli, or by inducing apoptosis when produced at elevated concentrations. The mechanisms of NO in regulating these biological functions can be either through cyclic guanylate cyclase (cGMP)-dependent or cGMP-independent pathways. The purpose of this review is to highlight the implication of NO in cell signalling, synaptic transmission, and cell death. We focus also on the protective role as well as the toxicity of NO. Finally, the adverse effects of inhaled nitric oxide are also depicted in this review.

Ventilation prevents pulmonary endothelial dysfunction and improves oxygenation after cardiopulmonary bypass without aortic cross-clamping.

OBJECTIVE: Endothelial dysfunction of the pulmonary arterial tree occurring after cardiopulmonary bypass (CPB) contributes to pulmonary hypertension and respiratory failure in the postoperative period. The goal of the present study was to characterize the alterations of endothelial cell signal transduction pathways in pulmonary arteries following CPB, the effect of ventilation and nitric oxide (NO) inhalation on endothelium-dependent relaxations and the alterations in hemodynamics and oxygenation. METHODS: Six groups of Landrace swine were compared: control, sham without CPB, CPB 150min+no reperfusion, CPB 150min+reperfusion 60 min, CPB 150min+ventilation (tidal volume 12 ml/kg)+reperfusion 60 min, and CPB 150min+NO inhalation (with ventilation, NO 40 ppm)+60 min of reperfusion. No cross-clamping was applied, the heart was left beating, empty. Pulmonary artery reactivity was evaluated in organ chambers to assess the endothelium-dependent relaxations. RESULTS: CPB alone did not alter endothelial function. CPB and pulmonary reperfusion induced a statistically significant decrease in endothelium-dependent relaxations to acetylcholine. Mechanical ventilation during CPB prevented the reduction of relaxations to acetylcholine. Ventilation and NO inhalation during CPB did not differ from ventilation alone in terms of endothelium-dependent relaxations. There were no differences between groups for relaxations to bradykinin. There was a significant increase in arterial oxygen tension in the ventilated group compared to the non-ventilated group. CONCLUSION: Pulmonary reperfusion after CPB causes a selective dysfunction of Gi-protein-mediated relaxations. Mechanical ventilation prevents the pulmonary endothelial dysfunction due to reperfusion after CPB. Ventilation also improves oxygenation after CPB. Mechanical ventilation could be used as a preventive approach for patients undergoing cardiac surgery with extracorporeal circulation.

[Influence of inhaled nitric oxide on surfactant in the total cardiopulmonary bypass pig model].

OBJECTIVE: To study whether or not inhaled nitric oxide (INO) can improve surfactant production and pulmonary mechanics after CPB in pigs, and to seek the mechanism of lung injury during mechanical ventilation. METHODS: Thirty pigs were randomized into 6 groups: Sham (n = 5), Sham + INO (n = 5), CPB (n = 5), CPB + INO (n = 5), CPB + lipopolysaccharide (LPS) (n = 5), and CPB + LPS + INO (n = 5). After anesthesia induction, INO (mass fraction, 20 x 10(-6)), added to the gas mixture, was given to the animals throughout the procedure. After 2 hours of INO treatment, broncho-alveolar lavage (BAL) fluid was taken for surfactant assay and cytology analysis. Pulmonary hemodynamics parameters and lung compliance were measured as well. CPB was performed for 90 minutes after the first BAL sampling at T0. Four hours (T4) and 24 hours (T24) following CPB, BAL and other measurements were repeated. After CPB, LPS (4 micrograms.kg-1) was infused to specific groups of pigs within 90 minutes in order to stimulate the inflammation process. RESULTS: Pulmonary hemodynamics parameters (pulmonary artery pressure, pulmonary vascular resistance and oxygenation) in all INO groups were much better than those of the control groups at T4 and T24. However, lung compliance of pigs in all groups declined with time, and showed statistically significant differences at T24 compared with T0. At T0, the active subfraction of surfactant (large aggregate, LA) was increased in animals given INO treatment compared with the controls, but decreased with time, and at T24 significantly reduced in all groups. In LPS groups, this decrease LA after T4 was very obvious. Total cell counts and the percent differentials of neutrophils in BAL increased with time, being lower in the INO groups than in other groups. CONCLUSION: INO exposure exerted time-related effects on the lung surfactant (LA). Initially, INO resulted in short-term increase of surfactant production at T0. However, with time passing by, INO exposure following CPB did not prevent long-term decrease of lung surfactant and lung compliance although INO was beneficial for pulmonary hemodynamics and oxygenation. In summary, despite the use of INO, synergetic effects of long-term hyperoxia, mechanical ventilation and inflammation following CPB may exacerbate pulmonary mechanics and result in surfactant dysfunction.