SummaryThis study reviews the predictive value of maximum oxygen consumption ( _ VO 2 max ) and anaerobic threshold, obtained through cardiopulmonary exercise testing, in calculating peri-operative morbidity and mortality in non-cardiopulmonary thoraco-abdominal surgery. A literature review provided nine studies that investigated either one or both of these two variables across a wide range of surgical procedures. Six of the seven studies that reported sufficiently detailed results on peak oxygen consumption and four of the six studies that reported sufficiently detailed results on anaerobic threshold found them to be significant predictors. We conclude that peak oxygen consumption and possibly anaerobic threshold are valid predictors of peri-operative morbidity and mortality in non-cardiopulmonary thoraco-abdominal surgery. These indicators could potentially provide a means of allocating increased care to high-risk patients. Cardiopulmonary exercise testing (CPET or CPX) is a non-invasive, integrated assessment of cardiovascular and pulmonary function both at rest and under stress. Among the purported benefits is its ability to determine the ability of the subject's physiological capacity to cope with the metabolic demands created by the trauma of major surgery. During the test subjects are exposed to incremental physical exercise up to their maximally tolerated level, dictated either by exhaustion or symptom related cessation (e.g., breathlessness or angina). Several physiological variables are recorded including ventilatory parameters, inspiratory and expiratory gases, blood pressure (BP) and electrocardiogram (ECG). From these are derived two key indicators: the body's maximum oxygen uptake ( _ VO 2 max ) and the point at which anaerobic metabolism exceeds aerobic metabolism (Ventilatory Anaerobic Threshold or VAT). Together, these broadly indicate the ability of the cardiovascular system to deliver oxygen to the peripheral tissues and the ability of the tissues to utilise that oxygen. It has already been demonstrated that measures such as _ VO 2 max are useful predictors of postoperative complications of pulmonary resection surgery [1][2][3] and assessing the timing of cardiac transplant surgery [4], while the VAT is a predictor of postoperative cardiac complications in abdominal surgery [5]. Physiology of the anaerobic thresholdLactate accumulation in exercising muscle occurs when the muscle O 2 demand exceeds the supply. At this point the venous lactate concentration will begin to rise. This point is called the Lactate Anaerobic Threshold (LAT). The muscle lactate ⁄ pyruvate ratio increases at the LAT which supports the concept that the lactic acidosis results from relative muscle hypoxia [6][7][8].As an individual commences an incremental exercise test, their expired minute volume ( _ V E ), oxygen consumption per minute ( _ VO 2 ) and CO 2 production per minute ( _ VCO 2 ) all increase linearly with respect to variables such as work rate or time. However a point is reached when _ VCO 2 increases out of ...

BackgroundPostoperative pulmonary complications (PPCs) are associated with poor outcomes following thoracotomy and lung resection. Video-assisted thoracoscopic surgery (VATS) for lobectomy is now frequently utilised as an alternative to thoracotomy, however patients remain at risk for development of PPC. There is little known of the short-term outcome associated with PPC following VATS lobectomy and if there are any potential risk factors that could be modified to prevent PPC development; our study aimed to investigate this.MethodsA prospective observational study of consecutive patients undergoing VATS lobectomy for lung cancer over a 4-year period in a regional centre was performed (2012–2016). Exclusion criteria included re-do VATS or surgery for pulmonary infection. All patients received physiotherapy as necessary from postoperative day 1 (POD1) and PPC was determined using the Melbourne Group Scale. Outcomes included hospital LOS, intensive therapy unit (ITU) admission and hospital mortality.ResultsOf the 285 patients included in the study, 137 were male (48.1%), the median (IQR) age was 69 (13) years and the mean (±SD) FEV1% predicted was 87% (±19). Patients that developed a PPC (n = 21; 7.4%) had a significantly longer hospital LOS (4 vs. 3 days), higher frequency of ITU admission (23.8% vs. 0.5%) and higher hospital mortality (14.3% vs. 0%) (p < 0.001). PPC patients also required more physiotherapy contacts/time, emergency call-outs and specific pulmonary therapy (p < 0.05). Current smoking and COPD diagnosis were significantly associated with development of PPC on univariate analysis (p < 0.05), however only current smoking was a significant independent risk factor on multivariate analysis (p = 0.015).ConclusionsPatients undergoing VATS lobectomy remain at risk of developing a PPC, which is associated with an increase in physiotherapy requirements and a worse short-term morbidity and mortality. Current smoking is the only independent risk factor for PPC after VATS lobectomy, thus vigorous addressing of preoperative smoking cessation is urgently needed.

BackgroundThe aim of this study is to determine the feasibility of using nuclear magnetic resonance (NMR) tracer studies (13C-enriched glucose) to detect ex vivo de novo metabolism in the perfusion fluid and cortical tissue of porcine kidneys during hypothermic machine perfusion (HMP).MethodsPorcine kidneys (n = 6) were subjected to 24 h of HMP using the Organ Recovery Systems LifePort Kidney perfusion device. Glucose, uniformly enriched with the stable isotope 13C ([U-13C] glucose), was incorporated into KPS-1-like perfusion fluid at a concentration of 10 mM. Analysis of perfusate was performed using both 1D 1H and 2D 1H,13C heteronuclear single quantum coherence (HSQC) NMR spectroscopy. The metabolic activity was then studied by quantifying the proportion of key metabolites containing 13C in both perfusate and tissue samples.ResultsThere was significant enrichment of 13C in a number of central metabolites present in both the perfusate and tissue extracts and was most pronounced for lactate and alanine. The total amount of enriched lactate (per sample) in perfusion fluid increased during HMP (31.1 ± 12.2 nmol at 6 h vs 93.4 ± 25.6 nmol at 24 h p < 0.01). The total amount of enriched alanine increased in a similar fashion (1.73 ± 0.89 nmol at 6 h vs 6.80 ± 2.56 nmol at 24 h p < 0.05). In addition, small amounts of enriched acetate and glutamic acid were evident in some samples.ConclusionsThis study conclusively demonstrates that de novo metabolism occurs during HMP and highlights active metabolic pathways in this hypothermic, hypoxic environment. Whilst the majority of the 13C-enriched glucose is metabolised into glycolytic endpoint metabolites such as lactate, the presence of non-glycolytic pathway derivatives suggests that metabolism during HMP is more complex than previously thought. Isotopic labelled ex vivo organ perfusion studies using 2D NMR are feasible and informative.

Hypothermic machine perfusion (HMP) and static cold storage (SCS) are the two methods used to preserve deceased donor kidneys prior to transplant. This study seeks to characterise the metabolic profile of HMP and SCS porcine kidneys in a cardiac death donor model. Twenty kidneys were cold flushed and stored for two hours following retrieval. Paired kidneys then underwent 24 h of HMP or SCS or served as time zero controls. Metabolite quantification in both storage fluid and kidney tissue was performed using one dimensional H NMR spectroscopy. For each metabolite, the net gain for each storage modality was determined by comparing the total amount in each closed system (i.e. total amount in storage fluid and kidney combined) compared with controls. 26 metabolites were included for analysis. Total system metabolite quantities following HMP or SCS were greater for 14 compared with controls (all p< 0.05). In addition to metabolic differences with control kidneys, the net metabolic gain during HMP was greater than SCS for 8 metabolites (all p < 0.05). These included metabolites related to central metabolism (lactate, glutamate, aspartate, fumarate and acetate). The metabolic environments of both perfusion fluid and the kidney tissue are strikingly different between SCS and HMP systems in this animal model. The total amount of central metabolites such as lactate and glutamate observed in the HMP kidney system suggests a greater degree of de novo metabolic activity than in the SCS system. Maintenance of central metabolic pathways may contribute to the clinical benefits of HMP.

Objectives: Following major thoracic surgery physiotherapy is recommended to improve reduced lung volume, aid secretion clearance, and improve mobility, however, in many centres physiotherapy provision is variable following minimally invasive Video-Assisted Thoracoscopic Surgery (VATS). The objective of this study was to observe frequency of pulmonary disease (COPD), body mass index (BMI), preoperative mobility and age were independently associated with issues potentially amenable to physiotherapy (p=0.013). Conclusion:Following VATS lobectomy a large proportion of patients demonstrated issues potentially amenable to physiotherapy. We recommend that patients receive routine physiotherapy assessment following this type of surgery to ensure that all issues are identified early. Screening of COPD, BMI, preoperative mobility and age will allow early identification of patients who may benefit most from postoperative physiotherapy and preoperative optimisation, however, these factors cannot predict the need for physiotherapy.