Comparison between capnodynamic and thermodilution method for cardiac output monitoring during major abdominal surgery: An observational study.

BACKGROUND: Cardiac output (CO) monitoring is the basis of goal-directed treatment for major abdominal surgery. A capnodynamic method estimating cardiac output (COEPBF) by continuously calculating nonshunted pulmonary blood flow has previously shown good agreement and trending ability when evaluated in mechanically ventilated pigs. OBJECTIVES: To compare the performance of the capnodynamic method of CO monitoring with transpulmonary thermodilution (COTPTD) in patients undergoing major abdominal surgery. DESIGN: Prospective, observational, method comparison study. Simultaneous measurements of COEPBF and COTPTD were performed before incision at baseline and before and after increased (+10 cmH2O) positive end-expiratory pressure (PEEP), activation of epidural anaesthesia and intra-operative events of hypovolemia and low CO. The first 25 patients were ventilated with PEEP 5 cmH2O (PEEP5), while in the last 10 patients, lung recruitment followed by individual PEEP adjustment (PEEPadj) was performed before protocol start. SETTING: Karolinska University Hospital, Stockholm, Sweden. PATIENTS: In total, 35 patients (>18 years) scheduled for major abdominal surgery with advanced hemodynamic monitoring were included in the study. MAIN OUTCOME MEASURES AND ANALYSIS: Agreement and trending ability between COEPBF and COTPTD at different clinical moments were analysed with Bland--Altman and four quadrant plots. RESULTS: In total, 322 paired values, 227 in PEEP5 and 95 in PEEPadj were analysed. Respectively, the mean COEPBF and COTPTD were 4.5 ±â€Š1.0 and 4.8 ±â€Š1.1 in the PEEP5 group and 4.9 ±â€Š1.2 and 5.0 ±â€Š1.0 l min-1 in the PEEPadj group. Mean bias (levels of agreement) and percentage error (PE) were -0.2 (-2.2 to 1.7) l min-1 and 41% for the PEEP5 group and -0.1 (-1.7 to 1.5) l min-1 and 31% in the PEEPadj group. Concordance rates during changes in COEPBF and COTPTD were 92% in the PEEP5 group and 90% in the PEEPadj group. CONCLUSION: COEPBF provides continuous noninvasive CO estimation with acceptable performance, which improved after lung recruitment and PEEP adjustment, although not interchangeable with COTPTD. This method may become a tool for continuous intra-operative CO monitoring during general anaesthesia in the future. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT03444545.

Clinical and experimental validation of a capnodynamic method for end-expiratory lung volume assessment.

INTRODUCTION: Lung protective ventilation can decrease post-operative pulmonary complications. The aim of this study was to evaluate a capnodynamic method estimating effective lung volume (ELV) as a proxy for end-expiratory lung volume in response to PEEP changes in patients, healthy subjects and a porcine model. METHODS: Agreement and trending ability for ELV in anaesthetized patients and agreement in awake subjects were evaluated using nitrogen multiple breath wash-out/in and plethysmography as a reference respectively. Agreement and trending ability were evaluated in pigs during PEEP elevations with inert gas wash-out as reference. RESULTS: In anaesthetized patients bias (95% limits of agreement [LoA]) and percentage error (PE) at PEEP 0 cm H2 O were 133 mL (-1049 to 1315) and 71%, at PEEP 5 cm H2 O 161 mL (-1291 to 1613 mL) and 66%. In healthy subjects: 21 mL (-755 to 796 mL) and 26%. In porcines, at PEEP 5-20 cm H2 O bias decreased from 223 mL to 136 mL LoA (34-412) to (-30 to 902) and PE 29%-49%. Trending abilities in anaesthetized patients and porcines were 100% concordant. CONCLUSION: The ELV-method showed low bias but high PE in anaesthetized patients. Agreement was good in awake subjects. In porcines, agreement was good at lower PEEP levels. Concordance related to PEEP changes reached 100% in all settings. This method may become a useful trending tool for monitoring lung function during mechanical ventilation, if findings are confirmed in other clinical contexts.

Performance of a capnodynamic method estimating cardiac output during respiratory failure - before and after lung recruitment.

Respiratory failure may cause hemodynamic instability with strain on the right ventricle. The capnodynamic method continuously calculates cardiac output (CO) based on effective pulmonary blood flow (COEPBF) and could provide CO monitoring complementary to mechanical ventilation during surgery and intensive care. The aim of the current study was to evaluate the ability of a revised capnodynamic method, based on short expiratory holds (COEPBFexp), to estimate CO during acute respiratory failure (LI) with high shunt fractions before and after compliance-based lung recruitment. Ten pigs were submitted to lung lavage and subsequent ventilator-induced lung injury. COEPBFexp, without any shunt correction, was compared to a reference method for CO, an ultrasonic flow probe placed around the pulmonary artery trunk (COTS) at (1) baseline in healthy lungs with PEEP 5 cmH2O (HLP5), (2) LI with PEEP 5 cmH2O (LIP5) and (3) LI after lung recruitment and PEEP adjustment (LIPadj). CO changes were enforced during LIP5 and LIPadj to estimate trending. LI resulted in changes in shunt fraction from 0.1 (0.03) to 0.36 (0.1) and restored to 0.09 (0.04) after recruitment manoeuvre. Bias (levels of agreement) and percentage error between COEPBFexp and COTS changed from 0.5 (- 0.5 to 1.5) L/min and 30% at HLP5 to - 0.6 (- 2.3 to 1.1) L/min and 39% during LIP5 and finally 1.1 (- 0.3 to 2.5) L/min and 38% at LIPadj. Concordance during CO changes improved from 87 to 100% after lung recruitment and PEEP adjustment. COEPBFexp could possibly be used for continuous CO monitoring and trending in hemodynamically unstable patients with increased shunt and after recruitment manoeuvre.

Performance of a capnodynamic method estimating effective pulmonary blood flow during transient and sustained hypercapnia.

The capnodynamic method is a minimally invasive method continuously calculating effective pulmonary blood flow (COEPBF), equivalent to cardiac output when intra pulmonary shunt flow is low. The capnodynamic equation joined with a ventilator pattern containing cyclic reoccurring expiratory holds, provides breath to breath hemodynamic monitoring in the anesthetized patient. Its performance however, might be affected by changes in the mixed venous content of carbon dioxide (CvCO2). The aim of the current study was to evaluate COEPBF during rapid measurable changes in mixed venous carbon dioxide partial pressure (PvCO2) following ischemia-reperfusion and during sustained hypercapnia in a porcine model. Sixteen pigs were submitted to either ischemia-reperfusion (n = 8) after the release of an aortic balloon inflated during 30 min or to prolonged hypercapnia (n = 8) induced by adding an instrumental dead space. Reference cardiac output (CO) was measured by an ultrasonic flow probe placed around the pulmonary artery trunk (COTS). Hemodynamic measurements were obtained at baseline, end of ischemia and during the first 5 min of reperfusion as well as during prolonged hypercapnia at high and low CO states. Ischemia-reperfusion resulted in large changes in PvCO2, hemodynamics and lactate. Bias (limits of agreement) was 0.7 (-0.4 to 1.8) L/min with a mean error of 28% at baseline. COEPBF was impaired during reperfusion but agreement was restored within 5 min. During prolonged hypercapnia, agreement remained good during changes in CO. The mean polar angle was -4.19° (-8.8° to 0.42°). Capnodynamic COEPBF is affected but recovers rapidly after transient large changes in PvCO2 and preserves good agreement and trending ability during states of prolonged hypercapnia at different levels of CO.

A modified breathing pattern improves the performance of a continuous capnodynamic method for estimation of effective pulmonary blood flow.

In a previous study a new capnodynamic method for estimation of effective pulmonary blood flow (COEPBF) presented a good trending ability but a poor agreement with a reference cardiac output (CO) measurement at high levels of PEEP. In this study we aimed at evaluating the agreement and trending ability of a modified COEPBF algorithm that uses expiratory instead of inspiratory holds during CO and ventilatory manipulations. COEPBF was evaluated in a porcine model at different PEEP levels, tidal volumes and CO manipulations (N = 8). An ultrasonic flow probe placed around the pulmonary trunk was used for CO measurement. We tested the COEPBF algorithm using a modified breathing pattern that introduces cyclic end-expiratory time pauses. The subsequent changes in mean alveolar fraction of carbon dioxide were integrated into a capnodynamic equation and effective pulmonary blood flow, i.e. non-shunted CO, was calculated continuously breath by breath. The overall agreement between COEPBF and the reference method during all interventions was good with bias (limits of agreement) 0.05 (-1.1 to 1.2) L/min and percentage error of 36 %. The overall trending ability as assessed by the four-quadrant and the polar plot methodology was high with a concordance rate of 93 and 94 % respectively. The mean polar angle was 0.4 (95 % CI -3.7 to 4.5)°. A ventilatory pattern recurrently introducing end-expiratory pauses maintains a good agreement between COEPBF and the reference CO method while preserving its trending ability during CO and ventilatory alterations.

[Transport and treatment of patients with STEMI in rural Iceland--Only a few patients receive PPCI within 120 minutes]. / Flutningstími og gæði meðferðar hjá sjúklingum með ST-hækkunar-hjartadrep á landsbyggðinni--fair ná í kransæðavíkkun innan 120 mínútna.

INTRODUCTION: ST-segment Elevation Myocardial Infarction (STEMI) is a life-threatening disease and good outcome depends on early restoration of coronary blood flow. Primary percutaneous coronary intervention (PPCI) is the treatment of choice if performed within 120 minutes of first medical contact (FMC) but in case of anticipated long transport or delays, pre-hospital fibrinolysis is indicated. The aim was to study transport times and adherence to clinical guidelines in patients with STEMI transported from outside of the Reykjavik area to Landspitali University Hospital in Iceland. MATERIALS AND METHODS: Retrospective chart review was conducted of all patients diagnosed with STEMI outside of the Reykjavik area and transported to Landspitali University Hospital in Reykjavik in 2011-2012. Descriptive statistical analysis and hypothesis testing was applied. RESULTS: Eighty-six patients had signs of STEMI on electrocardiogram (ECG) at FMC. In southern Iceland nine patients (21%) underwent PPCI within 120 minutes (median 157 minutes) and no patient received fibrinolysis. In northern Iceland and The Vestman Islands, where long transport times are expected, 96% of patients eligible for fibrinolysis (n=31) received appropriate therapy in a median time of 57 minutes. Significantly fewer patients received appropriate anticoagulation treatment with clopidogrel and enoxaparin in southern Iceland compared to the northern part. Mortality rate was 7% and median length of stay in hospital was 6 days. CONCLUSIONS: Time from FMC to PPCI is longer than 120 minutes in the majority of cases. Pre-hospital fibrinolysis should be considered as first line treatment in all parts of Iceland outside of the Reykjavik area. Directly electronically transmitted ECGs and contact with cardiologist could hasten diagnosis and decrease risk of unnecessary interhospital transfer. A STEMI database should be established in Iceland to facilitate quality control.

[Successful resuscitation of a pulseless young woman with pulmonary embolus in rural Iceland]. / Mannbjorg a Modrudal a Fjollum.

A 27 year old woman suffered a witnessed cardiac arrest in rural Iceland and regained pulse after one hour's resuscitation. She was transported by an air ambulance to a tertiary medical center in Reykjavik where she was diagnosed with a large pulmonary embolus. After 24 hours therapeutic hypothermia she was rewarmed and extubated two days later. She was discharged from the hospital after two weeks neurologically intact. This case illustrates that even in rural circumstances the chain of survival works if all the links are strong, with early access, early resuscitation and early advanced care.

[Management of patients with STEMI transported with air-ambulance to Landspitali University Hospital in Reykjavík]. / Flutningstími og gaedi medferdar hjá sjúklingum med ST-haekkunar hjartadrep á Nordur- og Austurlandi.

INTRODUCTION: A good outcome of patients presenting with STEMI (ST-Segment Elevation Myocardial Infarction) depends on early restoration of coronary blood flow. Pre-hospital fibrinolysis is recommended if primary percutaneous coronary intervention (PPCI) cannot be performed within 90 minutes of first medical contact (FMC). The purpose of this study was to study transport times for patients with STEMI who were transported with air-ambulance from the northern rural areas of Iceland to Landspitali University Hospital in Reykjavík, and to assess if the medical management was in accordance with clinical guidelines. MATERIALS AND METHODS: Retrospective chart review identified 33 patients with STEMI who were transported with air-ambulance to Landspitali University Hospital in Reykjavík during the years 2007 and 2008. RESULTS: The total time from first medical contact to arrival at Landspitali University Hospital emergency room was 3 hours and 7 minutes (median). All patients received aspirin and 26 (78.8%) received clopidogrel and enoxaparin. 16 patients (48.5%) received thrombolytic therapy in median 33 minutes after FMC and 15 patients had PPCI performed in median 4 hours and 15 minutes after FMC. Estimated PCI related delay was 3 hours and 42 minutes (median). One patient died and one was resuscitated within 30 hospital days. Mean hospital stay was 6.0 days. CONCLUSIONS: First medical contact to balloon time of less than 90 minutes is impossible for patients with STEMI transported from the northern rural areas to Landspitali University Hospital in Reykjavík. Medical therapy was in many cases suboptimal and PCI related delay too long.

Resolution of proteinuria in a patient with X-linked Alport syndrome treated with cyclosporine.

We report a 9-year-old Icelandic male with Alport syndrome and nephrotic-range proteinuria who responded well to cyclosporine therapy. He presented at the age of 2 years with gross hematuria and proteinuria during an episode of upper respiratory tract infection. Three years later he had developed persistent proteinuria; kidney function was normal. A renal biopsy revealed marked irregularities in the glomerular basement membrane consistent with Alport syndrome. Mutation analysis revealed a single base insertion in COL4A5 which was predicted to cause a major structural defect in the collagen IV alpha5 chain. Despite angiotensin-converting enzyme inhibitor therapy his proteinuria progressed to the nephrotic range associated with edema. At the age of 7 years, cyclosporine therapy was instituted, which promptly resulted in almost complete resolution of proteinuria. Three years later his urinary protein excretion was close to the normal range and serum creatinine remained within normal limits. We conclude that closely monitored cyclosporine therapy may be a safe and effective treatment in patients with severe proteinuria and Alport syndrome.