The implementation of a real time early warning system using machine learning in an Australian hospital to improve patient outcomes.

BACKGROUND: Early Warning Scores (EWS) monitor inpatient deterioration predominantly using vital signs. We evaluated inpatient outcomes after implementing an Artificial Intelligence (AI) based intervention in our local EWS. METHODS: A prior study calculated a Deterioration Index (DI) with logistic regression utilising demographics, vital signs, and laboratory results at multiple time points to predict any major adverse event (MAE-all cause mortality, ICU admission, or medical emergency team activation). The current study is a single hospital, pre-post study in Australia comparing the DI plus the existing EWS (Between the Flags-BTF) to only BTF. Data were collected on all eligible inpatients (≥16 years, admitted ≥24 hours, in general non-palliative wards). Controls were inpatients in the same hospital between January and December 2019. The DI was integrated into the electronic medical record and alerts were sent to senior ward nurse phones (July 2020-April 2021). RESULTS: We enrolled 28,639 patients (median age 73 years, IQR: 60-83) with 52.3% female. The intervention and control groups did not show any statistically significant differences apart from reduced admissions via the emergency department in the intervention group (40.4% vs 41.6%, P = 0.03). Risk for an MAE was lower in intervention than control (RR: 0.81; 95%CI: 0.74-0.89). Length of hospital stay was significantly reduced in the intervention group (3.74 days, IQR 1.84-7.26) compared to the control group (3.86 days, IQR 1.86-7.86, P = 0.002) CONCLUSIONS: Implementing the DI in one hospital in Australia was associated with some improved patient outcomes. Future RCTs are needed for further validation.

Perioperative transfusion and long-term mortality after cardiac surgery: a meta-analysis.

OBJECTIVES: Cardiac surgical procedures are associated with a high incidence of periprocedural blood loss and blood transfusion. Although both may be associated with a range of postoperative complications there is disagreement on the impact of blood transfusion on long-term mortality. This study aims to provide a comprehensive review of the published outcomes of perioperative blood transfusion, examined as a whole and by index procedure. METHODS: A systematic review of perioperative blood transfusion cardiac surgical patients was conducted. Outcomes related to blood transfusion were analysed in a meta-analysis and aggregate survival data were derived to examine long-term survival. RESULTS: Thirty-nine studies with 180,074 patients were identified, the majority (61.2%) undergoing coronary artery bypass surgery. Perioperative blood transfusions were noted in 42.2% of patients and was associated with significantly higher early mortality (OR 3.87, p < 0.001). After a median of 6.4 years (range 1-15), mortality remained significantly higher for those who received a perioperative transfusion (OR 2.01, p < 0.001). Pooled hazard ratio for long-term mortality similar for patients who underwent coronary surgery compared to isolated valve surgery. Differences in long-term mortality for all comers remained true when corrected for early mortality and when only including propensity matched studies. CONCLUSIONS: Perioperative red blood transfusion appears to be associated with a significant reduction in long-term survival for patients after cardiac surgery. Strategies such as preoperative optimisation, intraoperative blood conservation, judicious use of postoperative transfusions, and professional development into minimally invasive techniques should be utilised where appropriate to minimise the need for perioperative transfusions.

Paraprotein associated heparin resistance during cardiopulmonary bypass.

INTRODUCTION: Heparin resistance during cardiopulmonary bypass poses a significant intraoperative dilemma. Antithrombin deficiency related heparin resistance is well described, but less common causes are still poorly understood and inadequately managed. CASE REPORT: We present a case of heparin resistance during cardiopulmonary bypass in a gentleman with no previous haematological history or thrombotic risk factors. The patient required three times the regular dose of unfractionated heparin to achieve acceptable conditions to initiate and maintain bypass. The patient was found to have elevated serum immunoglobulin M (IgM) kappa paraprotein on post-operative investigation. DISCUSSION: Paraproteins may exhibit non-specific binding to long polymeric chains of unfractionated heparin and inhibits the interaction between heparin and antithrombin. As a result, excessive doses of heparin are required to overcome this, which increases the risk of perioperative bleeding and other complications. CONCLUSION: Elevated serum paraprotein levels should be recognised as a cause of heparin resistance during cardiopulmonary bypass.

LIMA to LAD grafting returns patient survival to age-matched population: 20-year outcomes of MIDCAB surgery.

OBJECTIVES: Previous studies have demonstrated the safety and excellent short-term and mid-term survival after minimally invasive direct coronary artery bypass (MIDCAB). We reviewed the long-term outcomes up to 20 years, including overall survival and freedom from reintervention. METHODS: Consecutive patients who underwent MIDCAB between February 1997 and August 2020 were identified. Demographic details, operative information and long-term outcomes were obtained. The Australian National Death Index database was accessed to obtain long-term mortality data. RESULTS: A total of 271 patients underwent an MIDCAB procedure during the study period. There were no intraoperative deaths and only one 30-day mortality (0.4%). The mean length of follow-up was 9.82 ± 8.08 years. Overall survival at 5-, 10-, 15- and 20-year survival was 91.9%, 84.7%, 71.3% and 56.5%, respectively. Patients with single-vessel disease [left anterior descending artery (LAD) only] had significantly better survival compared to patients with multivessel disease (P = 0.0035). During long-term follow-up, there were no patients who required repeat revascularization of the LAD territory. Sixty-nine patients died with the cause of death in 15 patients (21.7%) being attributable to ischaemic heart disease. An analysis comparing the isolated LAD disease MIDCAB cohort survival with the expected survival among an age/gender/year matched sample of the Australian reference population, using the standardized mortality ratio, demonstrated that the rate of survival returned to that of the reference population (standardized mortality ratio = 0.94). CONCLUSIONS: MIDCAB is a safe and effective revascularization strategy which can be successfully performed in a carefully selected patient population with low morbidity and excellent long-term results. The survival of MIDCAB patients returns to that of their age/gender/year-matched counterparts within the normal population and hence should be offered as an alternative to coronary stenting when counselling patients with ischaemic heart disease.

In patients with lung cancer is combined endobronchial ultrasound and endoscopic ultrasound superior to conventional mediastinoscopy in staging the mediastinum?

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was 'In patients with lung cancer, is combined endobronchial ultrasound and endoscopic ultrasound (EBUS + EUS) superior to cervical mediastinoscopy (CM) in staging the mediastinum?' Altogether more than 110 papers were found, of which one meta-analysis, two RCTs, and two cohort studies represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Studies directly comparing EBUS + EUS and CM are limited in number and quality, with the majority of studies focusing on comparing endosonographic techniques or a single technique with surgical staging. Moreover, in four out of five studies, surgical staging of the mediastinum was undertaken following a negative EBUS + EUS result, limiting the utility of comparing endosonography alone. Regardless of this, the initial EBUS + EUS approach followed by surgical staging if negative resulted in greater sensitivity and detection of N2/3 metastases as well as greater sampling in the majority of studies, resulting in higher likelihood of upstaging and treatment alterations for patients. There was also improved quality of life demonstrated in the EBUS + EUS group with significant reductions in futile thoracotomies and less complications when compared with exclusive CM staging. We conclude that a combined approach of combined endosonography in the first instance, followed by CM staging of the mediastinum results in greater sensitivity of nodal disease and subsequent greater accuracy in upstaging and determining treatment plans with a concurrent reduction in complication rates and futile procedures.

A Trend-Based Early Warning Score Can Be Implemented in a Hospital Electronic Medical Record to Effectively Predict Inpatient Deterioration.

OBJECTIVES: To determine whether a statistically derived, trend-based, deterioration index is superior to other early warning scores at predicting adverse events and whether it can be integrated into an electronic medical record to enable real-time alerts. DESIGN: Forty-three variables and their trends from cases and controls were used to develop a logistic model and deterioration index to predict patient deterioration greater than or equal to 1 hour prior to an adverse event. SETTING: Two large Australian teaching hospitals. PATIENTS: Cases were considered as patients who suffered adverse events (unexpected death, unplanned ICU transfer, urgent surgery, and rapid-response alert) between August 1, 2016, and April 1, 2019. INTERVENTIONS: The logistic model and deterioration index were tested on historical data and then integrated into an electronic medical record for a 6-month prospective "silent" validation. MEASUREMENTS AND MAIN RESULTS: Data were acquired from 258,732 admissions. There were 8,002 adverse events. The addition of vital sign and laboratory trend values to the logistic model increased the area under the curve from 0.84 to 0.89 and the sensitivity to predict an adverse event 1-48 hours prior from 0.35 to 0.41. A 48-hour simulation showed that the logistic model had a higher area under the curve than the Modified Early Warning Score and National Early Warning Score (0.87 vs 0.74 vs 0.71). During the silently run prospective trial, the sensitivity of the deterioration index to detect adverse event any time prior to the adverse event was 0.474, 0.369 1 hour prior, and 0.327 4 hours prior, with a specificity of 0.972. CONCLUSIONS: A deterioration prediction model was developed using patient demographics, ward-based observations, laboratory values, and their trends. The model's outputs were converted to a deterioration index that was successfully integrated into a live hospital electronic medical record. The sensitivity and specificity of the tool to detect inpatient deterioration were superior to traditional early warning scores.

Both surgical and percutaneous revascularization improve prognosis in patients with a coronary chronic total occlusion (CTO) irrespective of collateral robustness.

The impact of surgical or percutaneous coronary revascularization on prognosis in patients with a chronic total occlusion (CTO) remains uncertain. Particularly, whether revascularization of those with robust coronary collaterals improves prognosis is unknown. The objective of this study was to determine the predictors and prognostic impact of revascularization of a CTO, and to determine the clinical impact of robust coronary collaterals. Patients with a CTO diagnosed on coronary angiography between Jul 2010 and Dec 2019 were included in this study. Management strategy of the CTO was defined as percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG) or medical management. The degree of collateral robustness was determined by the Rentrop grading classification. Demographic, angiographic and clinical outcomes were recorded. A total of 954 patients were included in the study, of which 186 (19.5%) patients underwent CTO PCI, 296 (31.0%) patients underwent CABG and 472 (49.5%) patients underwent medical management of the CTO. 166 patients (17.4%) had Rentrop grade zero or one collaterals, 577 (60.5%) patients had Rentrop grade two and 211 (22.1%) had Rentrop grade three collaterals. The independent predictors of medical management of the CTO were older age, greater stenosis in the donor vessel, an emergent indication for angiography, a non-LAD CTO and female sex. The degree of collateral robustness was not associated with long-term mortality, while patients who were revascularized either through CABG or PCI had a significantly lower mortality compared to medical management alone (p < 0.0001). In patients with a CTO, the presence of robust collaterals is not associated with prognosis, while both surgical and percutaneous revascularization is associated with improved prognosis. Further research into the optimal revascularization strategy for a CTO is required.

'Is totally endoscopic coronary artery bypass grafting compared with minimally invasive direct coronary artery bypass grafting associated with superior outcomes in patients with isolated left anterior descending disease?'

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was 'Is totally endoscopic coronary artery bypass grafting compared with minimally invasive direct coronary artery bypass grafting associated with superior outcomes in patients with isolated left anterior descending disease?' Altogether more than 118 papers were found using the reported search, of which 4 represented the best evidence to answer the clinical question, which included 2 prospective cohort studies and 2 retrospective observational studies. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers were tabulated. There is a significant variation within the MIDCAB and TECAB techniques amongst the studies-including the experience of the surgeon, use of cardiopulmonary bypass, patient selection, and target vessel grafting strategies-highlighting the complexity of comparing these two minimally invasive procedures. Operative times were comparable across all studies, with TECAB patients having higher transfusions rates and conversion rates to either a median sternotomy or MIDCAB procedure. Overall safety was comparable between the two cohort groups, with similar length of stay and 30-day mortality. However, the TECAB group were more likely to require re-operation for bleeding and reintervention for early revascularisation with greater total hospital costs than the MIDCAB patients. Based on the available evidence, we conclude that TECAB is associated with a higher rate of transfusions, conversion to median sternotomy or MIDCAB, early graft failure and reintervention compared to the MIDCAB approach. We advise caution in adopting a TECAB approach.

Operative Results of Mitral Valve Repair and Replacement in Chronic Ischaemic Mitral Valve Regurgitation.

BACKGROUND: Ischaemic mitral regurgitation (IMR) carries significant morbidity and mortality. Surgical management includes coronary artery bypass surgery alone or concomitant with mitral valve repair or replacement. There is ongoing debate regarding the appropriate approach to the mitral valve in relation to long-term outcomes. This review examines our early and late follow-up, with operative and echocardiographic outcomes for mitral valve repair and mitral replacement for chronic IMR. METHODS: A retrospective review was performed on prospectively collected data of 119 consecutive patients who either underwent mitral repair (n=101) or mitral replacement (n=18) for chronic IMR at Prince Henry and The Prince of Wales hospitals in Sydney between 1999-2016. All patients had pre and postoperative transthoracic echocardiograms. Follow-up echocardiographic data was obtained from the most recent clinical appointment. Follow-up mortality outcomes were obtained with ethics approval from the Australian National Death Index (NDI). RESULTS: There was no statistical difference between cardiopulmonary bypass (CPB) time, cross-clamp time, time spent in intensive care unit (ICU) and time to discharge between cohorts. The replacement cohort was noted to have higher preoperative pulmonary artery (PA) pressures and a higher severity of IMR. Seven (7) deaths were in the mitral valve (MV) repair group within 30 days (6.9%) and three deaths in the MV replacement group within 30 days (16.7%). Echocardiographic follow-up was complete in 78% of the MV repair cohort at an average of 4.06±2.66 years, and 73% complete in the MV replacement cohort at an average of 6.09±4.3 years. Three (3) patients had prior MV repair before MV replacement early at days zero and 17, and late at 8 years respectively. Follow-up echocardiography showed mitral regurgitation (MR) in the mitral valve repair cohort as ≤ mild in 83.5% and ≤ trivial in 35.6%. In the MV replacement cohort MR ≤ mild in 100% and ≤ trivial in 82% with no moderate or severe MR. Preoperative tricuspid regurgitation (TR) and a flexible annuloplasty were predictive of an MR grade > mild in the repair cohort at discharge. Five-year (5-year) survival for the repair cohort was 85% with a mean follow-up time of 7.1±3.83 years. For the replacement cohort, five-year survival was 77.8% with a mean follow-up time of 5.35±1.54 years. CONCLUSIONS: Mitral valve repair and replacement for chronic IMR has acceptable mortality, reintervention rates and excellent postoperative echocardiographic degrees of IMR in this cohort. Further evaluation is required into quality of life post intervention for IMR and of preoperative predictive factors of significant MR postoperatively to help guide the appropriate choice of treatment. The presence of preoperative tricuspid regurgitation of moderate grade or higher, and the use of a flexible annuloplasty may indicate patients more likely to have a higher grade of MR at follow-up following mitral valve repair in patients with IMR.

Delayed diagnosis of right-sided valve endocarditis causing recurrent pulmonary abscesses: a case report.

BACKGROUND: Pulmonary valve infective endocarditis is a rare diagnosis that is usually associated with immunocompromised states or structurally abnormal hearts. It is unusual for it to occur in structurally normal hearts or to cause recurrent symptoms after targeted antibiotics. Although guidelines suggest follow-up with repeat echocardiography and inflammatory marker surveillance, this case demonstrates that these are not always useful investigations, and instead imaging of the chest may be more appropriate. CASE PRESENTATION: We describe a case of a 74-year-old man who presented with respiratory symptoms and was originally misdiagnosed with pneumonia but later found to have a large pulmonary valve vegetation caused by Streptococcus mitis. Despite initially responding to antibiotic therapy, the vegetation continued to cause pulmonary emboli and cavitating lung abscesses months later, necessitating pulmonary valve replacement. CONCLUSIONS: This case demonstrates that pulmonary valve endocarditis can present atypically with recurrent respiratory symptoms, and in such cases, echocardiography should be considered to investigate for right-sided infective endocarditis. In addition, despite correct treatment, with normalization of inflammatory markers and improvement in vegetation size, infective endocarditis can continue to cause systemic symptoms. Finally, clinicians should consider chest computed tomography routinely as part of right-sided infective endocarditis follow-up.

Temporary extracorporeal bypass modalities during aortic surgery.

The key to aortic surgery is protection of the brain, heart, spinal cord, and viscera. For operations involving the aortic arch, the focus is on cerebral protection, while for pathology involving the descending thoracic aorta, the focus is on spinal protection. Optimal cerebral and spinal protection requires an extensive knowledge of the operative steps and an understanding of the cardiopulmonary bypass modalities that are possible. A bloodless field is required when operating on the aorta. As a result, periods of ischemia to the central nervous system and end-organ viscera are often unavoidable. The main techniques to mitigate ischemia include hypothermia and selective perfusion of the ischemic organ in question. This chapter will first briefly review bypass modalities and then describe how they can be used for various aortic scenarios.

A Review of the Endovascular Management of Thoracic Aortic Pathology.

BACKGROUND: Thoracic endovascular aortic repair (TEVAR) has recently gained popularity, but there is ongoing debate surrounding its safety and efficacy. We present 13 years of TEVAR experience at our institution. METHODS: Data from procedures performed between September 2000 and October 2013 were sourced. Eighty-one TEVARs were performed in 72 patients for various disorders of the thoracic aorta. RESULTS: The mean duration of follow-up was 62 months (range, 2-140 months). One-month, one-year, and five-year survival rates were 93%, 88%, and 63%, respectively. Five mortalities occurred within 30 days of operation (7%), three of which were related to vascular complications. There were 12 episodes of postoperative endoleak (12.5%). The left subclavian artery was covered without revascularisation in nine cases resulting in two episodes of subclavian steal syndrome and one episode of left arm claudication. Three patients had perioperative strokes, and one patient spinal cord ischaemia. CONCLUSIONS: We demonstrated low rates of reintervention after TEVAR and a low risk of complications, particularly neurological. We therefore advocate an endovascular approach for thoracic pathology involving the aortic arch and descending aorta, particularly in elderly patients. Coverage of the LSCA is often necessary, but where possible, prophylactic revascularisation should be performed.

Impending paradoxical embolism: have we lost the clot?

Impending paradoxical embolism is a rare diagnosis that requires urgent treatment. We present a case where surgical thromboembolectomy was undertaken. The thrombus vanished from view on transesophageal ultrasound and was presumed to have undergone embolisation while bypass was established. Unexpectedly, it was found tangled in the superior vena cava cannula apertures.

Arrhythmogenicity of hypothermia - a large animal model of hypothermia.

BACKGROUND: Therapeutic hypothermia (TH) is used to mitigate cerebral injury after an out of hospital cardiac arrest. There is a perceived risk of increased arrhythmias with temperatures lower than the current target of 32-34°C for TH. This study sought to develop and investigate the electrophysiological changes in a sheep model of systemic hypothermia regarding the susceptibility to ventricular arrhythmias. METHODS: Ten sheep underwent systemic hypothermia using a venous-venous extra-corporeal circuit whilst instrumented with a 12 lead ECG. An epicardial sock recorded potentials to 30°C (N=10) or 26°C (N=6). Activation times (AT) and Activation Recovery Intervals (ARI) were calculated using custom software. RESULTS: The AT and ARI were significantly prolonged with increased heterogeneity during hypothermia. This effect was most pronounced between normothermia and 34°C during sinus rhythm (SR). For ventricular pacing (VP) however heterogeneity continued to increase with progressive hypothermia. CONCLUSIONS: Hypothermia causes a significant increase in the heterogeneity of depolarisation and repolarisation. There is evidence to suggest that SR is protective with most of the increase in heterogeneity occurring with cooling to 34°C. This raises the possibility that the current target temperatures for therapeutic hypothermia may be safely lowered to provide a gain in cerebral protection.

An Unusual Case of Cannula Obstruction Resulting from Venous Thromboembolism.

Cerebral strokes of unknown origin frequently present with a patent foramen ovale (PFO), a common atrial septal defect occurring in approximately 25% of the adult population. Deep vein thrombosis (DVT) or pulmonary embolism (PE) in the presence of a PFO can produce paradoxical systemic embolization subsequent to an increase in pulmonary pressure, permitting entry of thrombi into the arterial circulation. Diagnosis of an impending paradoxical embolism (IPDE) involves the detection of DVT or PE in the presence of an abnormal communication between left and right circulations and may include a right-to-left shunt. Treatment includes oral anticoagulation, antiplatelet agents, thrombolysis, transcatheter closure of the defect, or surgical embolectomy and PFO closure. As a result of risks of intracranial hemorrhage with fibrinolysis, pulmonary embolectomy using cardiopulmonary bypass (CPB) and deep hypothermia is a primary treatment with a surgical mortality rate at approximately 5%. Despite optimal management, IPDE is associated with a mortality rate of 18%. Prompt diagnosis and treatment is critical in avoiding systemic thromboembolization and strokes in these patients. We report a case of superior vena cava cannula obstruction resulting from a paradoxical embolus traversing a PFO during surgery. Warning signs and management during CPB are discussed.

Liberal use of axillary artery cannulation for aortic and complex cardiac surgery.

OBJECTIVES: Axillary artery cannulation for cardiopulmonary bypass has been described previously as a safe and reliable technique, with a low risk of atheroemboli, avoidance of malperfusion in aortic dissection and facilitation of selective antegrade cerebral perfusion during hypothermic circulatory arrest. The aim of this study was to document the broad applicability of axillary cannulation and its associated morbidity and identify where it was not possible to use planned axillary cannulation. METHODS: A retrospective review of a single surgeon's 10-year experience of axillary cannulation using the side-graft technique in 184 consecutive patients (age 22-92 years) in aortic and complex cardiac surgery from July 2002 to June 2012. RESULTS: There were no intraoperative deaths and no major complications related to axillary artery use. There were six postoperative deaths unrelated to axillary artery cannulation. Six patients (3.3%) had minor complications as a direct result of axillary cannulation including seroma, haematoma, chronic pain and pectoralis major muscle atrophy. There were 10 cases where planned axillary cannulation was abandoned, due to inadequate size of the axillary artery in 8 patients and axillary artery dissection and morbid obesity in 1 patient each. CONCLUSIONS: Axillary artery cannulation is an ideal arterial inflow site in cases where the ascending aorta is unsuitable as it is safe, reliable and reduces the risks of atheroembolization and malperfusion. Major complications are rare with this meticulous technique and it is our standard practice in complex cardiac and aortic surgery.