ALVEOLAR-ARTERIAL OXYGEN GRADIENT, PNEUMONIA SEVERITY INDEX AND OUTCOMES IN PATIENTS HOSPITALIZED WITH COMMUNITY ACQUIRED PNEUMONIA

Alveolar-arterial oxygen gradient: An early marker to predict the severity of community-acquired pneumonia in children

To study the clinical significance of alveolar-arterial oxygen gradient (PA-aO2) for children with community-acquired pneumonia (CAP). A prospective study was carried out from January 2020 to June 2023, Overall, 100 patients were included in the study, 35 had severe pneumonia, whereas, 65 had non-severe pneumonia. Clinical and laboratory data were retrospectively collected at the time of hospital admission and during hospitalization. Patients were divided into severe and non-severe groups. PA-aO2 was significantly higher among children with severe pneumonia, as determined by WHO, PRESS (P < .001). PA-aO2 was significantly higher among children with mechanical ventilation, shock, sepsis, and mortality. Receiver operating characteristic curve (ROC) analysis for PA-aO2 showed that the area under the curve was 0.76 (P value < .05), with a sensitivity of 84.3% and a specificity of 67.9%. Our study suggests that PA-aO2 level has a predictive value for detecting community-acquired pneumonia severity in children.

Impact of cytidine diphosphocholine on oxygenation in client-owned dogs with aspiration pneumonia

BACKGROUND

New drugs for veterinary patients with acute respiratory distress syndrome (ARDS) are urgently needed. Early or late postinfection treatment of influenza-infected mice with the liponucleotide cytidine diphosphocholine (CDP-choline) resulted in decreased hypoxemia, pulmonary edema, lung dysfunction, and inflammation without altering viral replication. These findings suggested CDP-choline could have benefit as adjunctive treatment for ARDS in veterinary patients (VetARDS).

OBJECTIVES

Determine if parenterally administered CDP-choline can attenuate mild VetARDS in dogs with aspiration pneumonia.

ANIMALS

Dogs admitted to a veterinary intensive care unit (ICU) for aspiration pneumonia.

METHODS

Subjects were enrolled in a randomized, double-blinded, placebo-controlled trial of treatment with vehicle (0.1 mL/kg sterile 0.9% saline, IV; n = 8) or CDP-choline (5 mg/kg in 0.1 mL/kg 0.9% saline, IV; n = 9) q12h over the first 48 hours after ICU admission.

RESULTS

No significant differences in signalment or clinical findings were found between placebo- and CDP-choline-treated dogs on admission. All dogs exhibited tachycardia, tachypnea, hypertension, hypoxemia, hypocapnia, lymphopenia, and neutrophilia. CDP-choline administration resulted in rapid, progressive, and clinically relevant increases in oxygenation as determined by pulse oximetry and ratios of arterial oxygen partial pressure (Pa O2 mmHg) to fractional inspired oxygen (% Fi O2 ) and decreases in alveolar-arterial (A-a) gradients that did not occur in placebo (saline)-treated animals. Treatment with CDP-choline was also associated with less platelet consumption over the first 48 hours, but had no detectable detrimental effects.

CONCLUSIONS AND CLINICAL IMPORTANCE

Ctyidine diphosphcholine acts rapidly to promote gas exchange in dogs with naturally occurring aspiration pneumonia and is a potential adjunctive treatment in VetARDS patients.

Cardiopulmonary Pathophysiological Aspects in the Context of COVID-19 and Obesity

Obesity is a significant public health concern associated with high morbidity. Obese patients are at risk of severe COVID-19 infection, and obesity is a high-risk factor for admission to the intensive care unit. We aimed to write a narrative review of cardiac and pulmonary pathophysiological aspects of obese patients in the context of COVID-19 infection. Obesity affects lung volume, with a decrease in expiratory reserve volume, which is associated with a decrease in lung and chest wall compliance, an increase in airway resistance, and an increase in work of breathing. Obesity affects cardiac structure and hemodynamics. Obesity is a risk factor for hypertension and cardiovascular disorders. Moreover, obesity is associated with a low-grade inflammatory state, endothelial dysfunction, hyperinsulinemia, and metabolic disorders. Obesity is associated with severe COVID-19 and invasive mechanical ventilation. These previous cardiopulmonary pathological aspects may explain the clinical severity in obese patients with COVID-19. Obese patients are at risk of severe COVID-19 infection. Understanding cardiorespiratory pathophysiological aspects may help physicians manage patients in hospitals.

Can Alveolar-Arterial Difference and Lung Ultrasound Help the Clinical Decision Making in Patients with COVID-19?

Background: COVID-19 is an emerging infectious disease, that is heavily challenging health systems worldwide. Admission Arterial Blood Gas (ABG) and Lung Ultrasound (LUS) can be of great help in clinical decision making, especially during the current pandemic and the consequent overcrowding of the Emergency Department (ED). The aim of the study was to demonstrate the capability of alveolar-to-arterial oxygen difference (AaDO₂) in predicting the need for subsequent oxygen support and survival in patients with COVID-19 infection, especially in the presence of baseline normal PaO₂/FiO₂ ratio (P/F) values. Methods: A cohort of 223 swab-confirmed COVID-19 patients underwent clinical evaluation, blood tests, ABG and LUS in the ED. LUS score was derived from 12 ultrasound lung windows. AaDO₂ was derived as AaDO₂ = ((FiO₂) (Atmospheric pressure − H₂O pressure) − (PaCO₂/R)) − PaO₂. Endpoints were subsequent oxygen support need and survival. Results: A close relationship between AaDO₂ and P/F and between AaDO₂ and LUS score was observed (R² = 0.88 and R² = 0.67, respectively; p < 0.001 for both). In the subgroup of patients with P/F between 300 and 400, 94.7% (n = 107) had high AaDO₂ values, and 51.4% (n = 55) received oxygen support, with 2 ICU admissions and 10 deaths. According to ROC analysis, AaDO₂ > 39.4 had 83.6% sensitivity and 90.5% specificity (AUC 0.936; p < 0.001) in predicting subsequent oxygen support, whereas a LUS score > 6 showed 89.7% sensitivity and 75.0% specificity (AUC 0.896; p < 0.001). Kaplan–Meier curves showed different mortality in the AaDO₂ subgroups (p = 0.0025). Conclusions: LUS and AaDO₂ are easy and effective tools, which allow bedside risk stratification in patients with COVID-19, especially when P/F values, signs, and symptoms are not indicative of severe lung dysfunction.

Chest computed tomography and alveolar-arterial oxygen gradient as rapid tools to diagnose and triage mildly symptomatic COVID-19 pneumonia patients

Background

In the coronavirus disease 2019 (COVID-19) pandemic, rapid clinical triage is crucial to determine which patients need hospitalisation. We hypothesised that chest computed tomography (CT) and alveolar-arterial oxygen tension ratio (A-a) gradient may be useful to triage these patients, since they reflect the severity of the pneumonia-associated ventilation/perfusion abnormalities.

Methods

A retrospective analysis was performed in 235 consecutive patients suspected for COVID-19. The diagnostic protocol included low-dose chest CT and arterial blood gas analysis. In patients with CT-based COVID-19 pneumonia, the association between “need for hospitalisation” and A-a gradient was investigated by a multivariable logistic regression model. The A-a gradient was tested as a predictor for need for hospitalisation using receiver operating characteristic curve analysis and a logistic regression model.

Results

72 out of 235 patients (mean±sd age 55.5±14.6 years, 40% female) screened by chest CT showed evidence for COVID-19 pneumonia. In these patients, A-a gradient was shown to be a predictor of need for hospitalisation, with an optimal decision level (cut-off) of 36.4 mmHg (95% CI 0.70–0.91, p<0.001). The A-a gradient was shown to be independently associated with need for hospitalisation (OR 1.97 (95% CI 1.23–3.15), p=0.005; A-a gradient per 10 points) from CT severity score (OR 1.13 (95% CI 0.94–1.36), p=0.191), National Early Warning Score (OR 1.19 (95% CI 0.91–1.57), p=0.321) or peripheral oxygen saturation (OR 0.88 (95% CI 0.68–1.14), p=0.345).

Conclusion

Low-dose chest CT and the A-a gradient may serve as rapid and accurate tools to diagnose COVID-19 pneumonia and to select mildly symptomatic patients in need for hospitalisation.

Low-dose chest CT and alveolar–arterial oxygen gradient appear to be rapid and accurate tools to diagnose #COVID19 pneumonia, and to select mildly symptomatic patients in need of hospitalisationhttps://bit.ly/2N3rJlE

The alveolar-arterial gradient, pneumonia severity scores and inflammatory markers to predict 30-day mortality in pneumonia

OBJECTIVE

The objective of this study was to evaluate the association of elevated alveolar-arterial oxygen (A-a O₂) gradient with risk of mortality in hospitalized patients with community-acquired pneumonia (CAP).

METHODS

This prospective study included 206 patients diagnosed with CAP admitted to the ED. Demographics, comorbidities, arterial blood gas, serum electrolytes, liver-renal functions, complete blood count, NLR, PLR, CRP, CAR, procalcitonin, A-a O₂ gradient, expected A-a O₂ and A-a O₂ difference were evaluated. PSI and CURB-65 scores were classified as follow: a) PSI low risk (I-III) and moderate-high risk (IV-V) groups; b) CURB-65; low risk (0-2) and high risk (3-5) groups.

RESULTS

The survival rates of the PSI class (I-III) were significantly higher than the ones of the PSI class (IV-V) (92.1% vs. 62.9%, respectively). The percentage of survivors of the CURB-65 score (0-2) group (81.9%) was higher than the survivors of CURB-65 score (3-5) group (27.8%). Creatinine, BUN, uric acid, phosphorus, RDW, CRP, CAR, procalcitonin, lactate, A-a 0₂ gradient, expected A-a 0₂ and A-a 0₂ difference were significantly higher and basophil was lower in non-survivors. A-a O₂ gradient (AUC 0.78), A-a O₂ difference (AUC 0.74) and albumin (AUC 0.80) showed highest 30-day mortality prediction. NLR (AUC 0.58) and PLR (AUC 0.55) showed lowest 30-day mortality estimation. Procalcitonin (AUC 0.65), PSI class (AUC 0.81) and PSI score (AUC 0.86) indicated statistically significant higher 30-day mortality prediction.

CONCLUSION

A-a O₂ gradient, A-a O₂ difference and albumin are potent predictors of 30-day mortality in CAP patients in the ED.

The role of the clinical laboratory in diagnosing acid-base disorders

Acid-base homeostasis is fundamental for life. The body is exceptionally sensitive to changes in pH, and as a result, potent mechanisms exist to regulate the body's acid-base balance to maintain it in a very narrow range. Accurate and timely interpretation of an acid-base disorder can be lifesaving but establishing a correct diagnosis may be challenging. The underlying cause of the acid-base disorder is generally responsible for a patient's signs and symptoms, but laboratory results and their integration into the clinical picture is crucial. Important acid-base parameters are often available within minutes in the acute hospital care setting, and with basic knowledge it should be easy to establish the diagnosis with a stepwise approach. Unfortunately, many caveats exist, beginning in the pre-analytical phase. In the post-analytical phase, studies on the arterial reference pH are scarce and therefore many different reference values are used in the literature without any solid evidence. The prediction models that are currently used to assess the acid-base status are approximations that are mostly based on older studies with several limitations. The two most commonly used methods are the physiological method and the base excess method, both easy to use. The secondary response equations in the base excess method are the most convenient. Evaluation of acid-base disorders should always include the assessment of electrolytes and the anion gap. A major limitation of the current acid-base laboratory tests available is the lack of rapid point-of-care laboratory tests to diagnose intoxications with toxic alcohols. These intoxications can be fatal if not recognized and treated within minutes to hours. The surrogate use of the osmolal gap is often an inadequate substitute in this respect. This article reviews the role of the clinical laboratory to evaluate acid-base disorders.

Limb remote ischemic preconditioning attenuates lung injury after pulmonary resection under propofol-remifentanil anesthesia: a randomized controlled study

BACKGROUND

Remote ischemic preconditioning (RIPC) may confer the protection in critical organs. The authors hypothesized that limb RIPC would reduce lung injury in patients undergoing pulmonary resection.

METHODS

In a randomized, prospective, parallel, controlled trial, 216 patients undergoing elective thoracic pulmonary resection under one-lung ventilation with propofol-remifentanil anesthesia were randomized 1:1 to receive either limb RIPC or conventional lung resection (control). Three cycles of 5-min ischemia/5-min reperfusion induced by a blood pressure cuff served as RIPC stimulus. The primary outcome was PaO2/FIO2. Secondary outcomes included other pulmonary variables, the incidence of in-hospital complications, markers of oxidative stress, and inflammatory response.

RESULTS

Limb RIPC significantly increased PaO2/FIO2 compared with control at 30 and 60 min after one-lung ventilation, 30 min after re-expansion, and 6 h after operation (238 ± 52 vs. 192 ± 67, P = 0.03; 223 ± 66 vs. 184 ± 64, P = 0.01; 385 ± 61 vs. 320 ± 79, P = 0.003; 388 ± 52 vs. 317 ± 46, P = 0.001, respectively). In comparison with control, it also significantly reduced serum levels of interleukin-6 and tumor necrosis factor-α at 6, 12, 24, and 48 h after operation and malondialdehyde levels at 60 min after one-lung ventilation and 30 min after re-expansion (all P < 0.01). The incidence of acute lung injury and the length of postoperative hospital stay were markedly reduced by limb RIPC compared with control (all P < 0.05).

CONCLUSION

Limb RIPC attenuates acute lung injury via improving intraoperative pulmonary oxygenation in patients without severe pulmonary disease after lung resection under propofol-remifentanil anesthesia.

Effect of combined remote ischemic preconditioning and postconditioning on pulmonary function in valvular heart surgery

BACKGROUND

The aim of this study was to evaluate the lung-protective effect of combined remote ischemic preconditioning (RIPCpre) and postconditioning (RIPCpost) in patients undergoing complex valvular heart surgery.

METHODS

In this randomized, placebo-controlled, double-blind trial, 54 patients were assigned to an RIPCpre plus RIPCpost group or a control group (1:1). Patients in the RIPCpre plus RIPCpost group received three 10-min cycles of right-side lower-limb ischemia of 250 mm Hg at both 10 min after anesthetic induction and weaning from cardiopulmonary bypass. The primary end point was to compare postoperative Pao(2)/Fio(2). Secondary end points were to compare pulmonary variables, incidence of acute lung injury, and inflammatory cytokines.

RESULTS

In both groups, Pao(2)/Fio(2) at 24 h postoperation was significantly decreased compared with each corresponding baseline value. However, intergroup comparisons of pulmonary variables, including Pao(2)/Fio(2) and incidence of acute lung injury, revealed no significant differences. Serum levels of IL-6, IL-8, IL-10, and tumor necrosis factor-α were all significantly increased in both groups compared with each corresponding baseline value, without any significant intergroup differences. There were also no significant differences in transpulmonary gradient of IL-6, IL-10, and tumor necrosis factor-α between the groups.

CONCLUSIONS

RIPCpre plus RIPCpost as tested in this randomized controlled trial did not provide significant pulmonary benefit following complex valvular cardiac surgery.

N-Acetylcysteine modulates acute lung injury induced by Pseudomonas aeruginosa in rats

1. In critically ill patients, Pseudomonas aeruginosa-induced pneumonia and the lung injury associated with infection are major causes of mortality. The aim of the present study was to evaluate the protective properties of N-acetylcysteine (NAC) in rats infected with P. aeruginosa and the role of nitric oxide synthases (NOS) protein in this process. 2. Pneumonia was induced in rats by infecting them with P. aeruginosa intratracheally. One group of rats was treated with NAC (150 mg/kg per day, i.p., for 7 days). An untreated group served as the control. Samples were collected both before (0 h) and after infection (24 h). Bacterial loads in lung tissue, the lung wet : dry (W/D) ratio and pulmonary vascular permeability were assessed. Total cell and polymorphonuclear leucocyte cell counts in bronchoalveolar lavage fluid were determined. The expression of inducible (i) NOS and endothelial (e) NOS protein was analysed and correlated with indices of lung injury using Pearson's correlation analysis. 3. Bacterial load, lung injury indices and NOS expression increased after infection. Pretreatment with NAC mitigated lung injury although it did not significantly change bacterial loads. Furthermore, NAC treatment increased eNOS protein expression, but decreased iNOS expression, in lung tissues after infection. The expression of iNOS protein was positively correlated with indices of lung injury, whereas there was a negative correlation between eNOS expression and lung injury indices. 4. N-Acetylcysteine modulated P. aeruginosa-induced lung injury in rats. The results suggest that this effect maybe due to regulation of iNOS and eNOS protein expression by NAC.

Cardiac troponin I levels and alveolar-arterial oxygen gradient in patients with community-acquired pneumonia

BACKGROUND

Patients with community-acquired pneumonia (CAP) appear to have cardiac stress as demonstrated by elevated B-type natriuretic peptide (BNP). We hypothesised that myocardial stress and decrease in oxygenation might also lead to elevations of cardiac troponin I (cTnI) levels in serum.

OBJECTIVE

The aim of this study was to see if cTnI was associated with the alveolar-arterial oxygen gradient (DeltaA-a), a marker of severity in CAP.

METHODS

Retrospective cohort study of 901 CAP patients with no evidence of acute coronary syndrome presenting to a large, tertiary-care, urban teaching hospital over a 3-year period.

RESULTS

A strong linear trend between log(10)cTnI and DeltaA-a was observed (r(2)=0.76) with a statistically significant Spearman correlation coefficient (r(s)=0.75; p<0.0001) between cTnI and DeltaA-a. A cTnI value of 0.5 ng/ml discriminated mild CAP from moderate-severe CAP with an OR=208 (95% CI: 50.5-408; p<0.0001).

CONCLUSIONS

These data suggest that decreased blood O(2) levels as suggested by elevated DeltaA-a may lead to acute myocardial damage and that cTnI may be useful as a biomarker to stratify risk in subjects with CAP.