Capnodynamic monitoring of lung volume and blood flow in response to increased positive end-expiratory pressure in moderate to severe COVID-19 pneumonia: an observational study.

BACKGROUND: The optimal level of positive end-expiratory pressure (PEEP) during mechanical ventilation for COVID-19 pneumonia remains debated and should ideally be guided by responses in both lung volume and perfusion. Capnodynamic monitoring allows both end-expiratory lung volume ([Formula: see text]) and effective pulmonary blood flow (EPBF) to be determined at the bedside with ongoing ventilation. METHODS: Patients with COVID-19-related moderate to severe respiratory failure underwent capnodynamic monitoring of [Formula: see text] and EPBF during a step increase in PEEP by 50% above the baseline (PEEPlow to PEEPhigh). The primary outcome was a > 20 mm Hg increase in arterial oxygen tension to inspired fraction of oxygen (P/F) ratio to define responders versus non-responders. Secondary outcomes included changes in physiological dead space and correlations with independently determined recruited lung volume and the recruitment-to-inflation ratio at an instantaneous, single breath decrease in PEEP. Mixed factor ANOVA for group mean differences and correlations by Pearson's correlation coefficient are reported including their 95% confidence intervals. RESULTS: Of 27 patients studied, 15 responders increased the P/F ratio by 55 [24-86] mm Hg compared to 12 non-responders (p < 0.01) as PEEPlow (11 ± 2.7 cm H2O) was increased to PEEPhigh (18 ± 3.0 cm H2O). The [Formula: see text] was 461 [82-839] ml less in responders at PEEPlow (p = 0.02) but not statistically different between groups at PEEPhigh. Responders increased both [Formula: see text] and EPBF at PEEPhigh (r = 0.56 [0.18-0.83], p = 0.03). In contrast, non-responders demonstrated a negative correlation (r = - 0.65 [- 0.12 to - 0.89], p = 0.02) with increased lung volume associated with decreased pulmonary perfusion. Decreased (- 0.06 [- 0.02 to - 0.09] %, p < 0.01) dead space was observed in responders. The change in [Formula: see text] correlated with both the recruited lung volume (r = 0.85 [0.69-0.93], p < 0.01) and the recruitment-to-inflation ratio (r = 0.87 [0.74-0.94], p < 0.01). CONCLUSIONS: In mechanically ventilated patients with moderate to severe COVID-19 respiratory failure, improved oxygenation in response to increased PEEP was associated with increased end-expiratory lung volume and pulmonary perfusion. The change in end-expiratory lung volume was positively correlated with the lung volume recruited and the recruitment-to-inflation ratio. This study demonstrates the feasibility of capnodynamic monitoring to assess physiological responses to PEEP at the bedside to facilitate an individualised setting of PEEP. TRIAL REGISTRATION: NCT05082168 (18th October 2021).

Post-operative renal failure management in mechanical circulatory support patients.

Acute kidney injury (AKI) occurs commonly in patients requiring mechanical circulatory support (MCS) after cardiothoracic surgery. The prognostic implications of AKI in this patient group relate closely to the pathophysiology and risk factors associated with the underlying disease; pre-operative, intra-operative, and post-operative variables; hemodynamic factors; and type of support device used. General approaches to AKI management, including prevention strategies, medical management, and hemodynamic support, are also applicable in patients requiring MCS. Approaches to renal replacement therapy vary depend on patient factors, device-specific factors, and local preferences and experience. In this invited narrative review, we discuss the pathophysiology, risk factors, and prognostic implications of AKI in post-operative adult patients following institution of MCS. Management strategies for AKI are presented with a focus on those supported with either extracorporeal membrane oxygenation or a ventricular assist device.

Comparison of echocardiographic and invasive measures of volaemia and cardiac performance in critically ill patients.

Echocardiographic measurements are used in critical care to evaluate volume status and cardiac performance. Mean systemic filling pressure and global heart efficiency measures intravascular volume and global heart function. This prospective study conducted in fifty haemodynamically stabilized, mechanically ventilated patients investigated relationships between static echocardiographic variables and estimates of global heart efficiency and mean systemic filling pressure. Results of univariate analysis demonstrated weak correlations between left ventricular end-diastolic volume index (r = 0.27, p = 0.04), right atrial volume index (rho = 0.31, p = 0.03) and analogue mean systemic filling pressure; moderate correlations between left ventricular ejection fraction (r = 0.31, p = 0.03), left ventricular global longitudinal strain (r = 0.36, p = 0.04), tricuspid annular plane systolic excursion (rho = 0.37, p = 0.01) and global heart efficiency. No significant correlations were demonstrated by multiple regression. Mean systemic filling pressure calculated with cardiac output measured by echocardiography demonstrated good agreement and correlation with invasive techniques (bias 0.52 ± 1.7 mmHg, limits of agreement -2.9 to 3.9 mmHg, r = 0.9, p < 0.001). Static echocardiographic variables did not reliably reflect the volume state as defined by estimates of mean systemic filling pressure. The agreement between static echocardiographic variables of cardiac performance and global heart efficiency lacked robustness. Echocardiographic measurements of cardiac output can be reliably used in calculation of mean systemic filling pressure.

Long-term Outcome in Severe Left Ventricular Primary Graft Dysfunction Post Cardiac Transplantation Supported by Early Use of Extracorporeal Membrane Oxygenation.

BACKGROUND: Severe primary graft dysfunction (PGD) is the leading cause of early death following cardiac transplantation. The early use of venoarterial extracorporeal membrane oxygenation (VA-ECMO) may facilitate graft rescue. However, the additional risks of its use are unknown. METHODS: We retrospectively reviewed the medical records of all adult patients who underwent cardiac transplantation from January 2009 to February 2016 at St Vincent's Hospital, Sydney, to evaluate risk factors for the use of VA-ECMO and related morbidity and long-term survival. RESULTS: One hundred ninety-two transplanted patients were identified, 49 (25%) of whom developed left or biventricular PGD requiring VA-ECMO. The total operation time (median 495 [interquartile range 139.8] versus 412.8 [132] min, P < 0.001), cardiopulmonary bypass time (220 [63] versus 176 [73] min, P < 0.001) and the presence of a previous sternotomy (29 [59%] versus 51 [36%], P = 0.019) were associated with the use of VA-ECMO. One-year survival in the VA-ECMO cohort was 71%. After a median follow-up time of 696 days (interquartile range 1201 d), survival was significantly higher in the non-ECMO group (P = 0.004) but not when conditioned on hospital survival (P = 0.34). Patients with shorter than median ECMO runtime (<108 h) had a similar long-term survival to patients who did not require ECMO (P = 0.559). In the ECMO cohort, multivariable logistic regression revealed baseline creatinine in µmol/L (odds ratio 0.99 [95% confidence interval 0.99-1.00], P = 0.019) and duration of ECMO support in days (odds ratio 0.65 [95% confidence interval 0.44-0.97], P = 0.034) were inversely and independently associated with 1-year survival. CONCLUSIONS: Short- and long-term survival of PGD supported with VA-ECMO was better than previously described. Early recovery of PGD on VA-ECMO support negates its negative impact on short- and long-term survival.

Fluid Balance and Recovery of Native Lung Function in Adult Patients Supported by Venovenous Extracorporeal Membrane Oxygenation and Continuous Renal Replacement Therapy.

Fluid overload is associated with increased mortality in adult patients with acute respiratory distress syndrome. In patients requiring venovenous extracorporeal membrane oxygenation (VV-ECMO), the effects of fluid removal on survival and lung recovery remain undefined. We assessed the impact of early fluid removal in adult patients supported by VV-ECMO and concomitant continuous renal replacement therapy, in an 18-bed tertiary intensive care unit between 2010 and 2015. Twenty-four patients met inclusion criteria, of these 15 (63%) survived to hospital discharge. In our patient group, a more negative cumulative daily fluid balance was strongly associated with improved pulmonary compliance (2.72 ml/cmH2O per 1 L negative fluid balance; 95% confidence interval [CI]: 1.61-3.83; P < 0.001). In addition, a more negative mean daily fluid balance was associated with improved pulmonary compliance (4.37 ml/cmH2O per 1 L negative fluid balance; 95% CI: 2.62-6.13; P < 0.001). Survivors were younger and had lower mean daily fluid balance (-0.33 L [95% CI: -1.22 to -0.06] vs. -0.07 L [95% CI: -0.76 to 0.06]; P = 0.438) and lower cumulative fluid balance up to day 14 (-4.60 L [95% CI: -8.40 to -1.45] vs. -1.00 L [95% CI: -4.60 to 0.90]; P = 0.325), although the fluid balance effect alone did not reach statistical significance.

Advances in critical care management of patients undergoing cardiac surgery.

Cardiac surgery has been evolving to include minimally invasive, hybrid and transcatheter techniques. Increasing patient age and medical complexity means that critical care management needs to adapt and evolve. Recent advances have occurred in several areas, including ventilation, haemodynamics and mechanical circulatory support, bleeding and coagulation, acute kidney injury, and neurological management. This narrative review describes standard care, recent advances, and future areas of research in the critical care management of patients undergoing cardiac surgery.

Echocardiographic approach to cardiac tamponade in critically ill patients.

Cardiac tamponade should be considered in a critically ill patient in whom the cause of haemodynamic shock is unclear. When considering tamponade, transthoracic echocardiography plays an essential role and is the initial investigation of choice. Diagnostic sensitivity of transthoracic echocardiography is dependent on image quality, and in some cases a transoesophageal approach may be required to confirm the diagnosis. Knowledge of the pathophysiology and echocardiographic features of cardiac tamponade are essential for the practicing Intensivist. This review presents an approach to the recognition, diagnosis, and treatment of cardiac tamponade in critically ill patients.

Extracorporeal cardiopulmonary resuscitation for refractory cardiac arrest: A multicentre experience.

AIM: To describe the ECPR experience of two Australian ECMO centres, with regards to survival and neurological outcome, their predictors and complications. METHODS: Retrospective observational study of prospectively collected data on all patients who underwent extracorporeal cardiopulmonary resuscitation (ECPR) at two academic ECMO referral centres in Sydney, Australia. MEASUREMENTS AND MAIN RESULTS: Thirty-seven patients underwent ECPR, 25 (68%) were for in-hospital cardiac arrests. Median age was 54 (IQR 47-58), 27 (73%) were male. Initial rhythm was ventricular fibrillation or pulseless ventricular tachycardia in 20 patients (54%), pulseless electrical activity (n=14, 38%), and asystole (n=3, 8%). 27 (73%) arrests were witnessed and 30 (81%) patients received bystander CPR. Median time from arrest to initiation of ECMO flow was 45min (IQR 30-70), and the median time on ECMO was 3days (IQR 1-6). Angiography was performed in 54% of patients, and 27% required subsequent coronary intervention (stenting or balloon angioplasty 24%). A total of 13 patients (35%) survived to hospital discharge (IHCA 33% vs. OHCA 37%). All survivors were discharged with favourable neurological outcome (Cerebral Performance Category 1 or 2). Pre-ECMO lactate level was predictive of mortality OR 1.35 (1.06-1.73, p=0.016). CONCLUSIONS: In selected patients with refractory cardiac arrest, ECPR may provide temporary support as a bridge to intervention or recovery. We report favourable survival and neurological outcomes in one third of patients and pre-ECMO lactate levels predictive of mortality. Further studies are required to determine optimum selection criteria for ECPR.

Implementation of an evidence based guideline reduces blood tests and length of stay for the limping child in a paediatric emergency department.

INTRODUCTION: Acute non-traumatic limp is a common reason for children to present to the emergency department (ED). There is a wide differential diagnosis for these patients, and there are certain serious conditions which cannot be missed. An evidence based guideline for the 'limping child' was designed and the impact of guideline implementation on a number of specific, predefined quantitative outcomes was assessed. METHODS: An initial retrospective chart review over 3 months was carried out for all patients presenting with acute non-traumatic limp. Following guideline introduction and implementation, information was gathered prospectively for a further 3 month period. Data outcomes between the two patient groups were then compared. RESULTS: 110 patients met the criteria for inclusion: 56 pre-guideline and 54 post-guideline implementation. Baseline characteristics and diagnosis breakdown were similar in both groups. The rate of laboratory investigations was significantly reduced following guideline implementation (68% of patients pre-guideline, vs 48% post-guideline; (χ(2)), p=0.03). The number of x-rays carried out was similar in each group (74 pre- vs 67 post-guideline, mean 1.32 vs 1.28; (χ(2)), p=0.53). Length of time spent in the ED was significantly reduced following guideline implementation (median time 150 min pre- vs 82.5 min post-guideline; (χ(2)), p=0.04). No cases of serious pathology were missed using the guideline. CONCLUSION: Implementation of an evidence based clinical practice guideline for the limping child in a paediatric ED reduced the overall time patients spent in the ED, reduced the need for unnecessary laboratory investigations and ensured that appropriate investigations were carried out on an individual patient basis.

Venous vs arterial blood gases in the assessment of patients presenting with an exacerbation of chronic obstructive pulmonary disease.

OBJECTIVE: The purpose of this study was to investigate the clinical correlation between arterial and venous blood gas (VBG) values in patients presenting to the emergency department (ED) with acute exacerbation of chronic obstructive pulmonary disease. METHODS: A prospective study of patients with chronic obstructive pulmonary disease presenting to the ED with acute ventilatory compromise was done. Patients were included if their attending physician considered arterial blood gas sampling important in their initial assessment. Data from arterial and venous samples were compared using Spearman correlation and bias plot (Bland-Altman) methods. RESULTS: Ninety-four patients were enrolled in the study. Eighty-nine patients had complete data sets for analysis. Arterial hypercarbia was present in 30 patients (33.7%; range, 51-140.19 mm Hg). All cases of arterial hypercarbia were detected using VBG sampling when a screening cutoff of 45 mm Hg was applied (sensitivity, 100%; 95% confidence interval, 88.7%-100% and specificity, 34%; 95% confidence interval, 23.1%-46.6%). Bias plot revealed moderate agreement between arterial and venous Pco(2) with an average difference of 8.6 mm Hg and 95% limits of agreement of -7.84 to 25.05 mm Hg. For pH, mean difference between each group was 0.039 (range, -0.12 to 0.03). Linear regression analysis for pH demonstrated very close equivalence with a regression coefficient of 0.955, and Spearman correlation showed significant correlation of 0.826 (P = .001). CONCLUSION: Venous pH and HCO(3) values show excellent correlation with arterial values. Using a previously validated screening cutoff of 45 mm Hg, venous CO(2) has 100% sensitivity in detecting arterial hypercarbia. There is insufficient agreement between venous and arterial CO(2) for VBG to replace arterial blood gas in determining the degree of hypercarbia.