A modified Gamblegram for the visual representation of acid-base disorders according to the Stewart-Figge approach.

The Gamblegram consists of two bars, each of which represents the sum of the charges of individual positively and negatively charged ions and is commonly used for visualizing changes in acid-base and electrolyte charges. However, according to the Stewart-Figge theory, the metabolic independent acid-base variables include the strong ion difference ([SID]) and the total concentrations of weak acids (albumin and inorganic phosphate), which are not shown in the conventional Gamblegram. Thus, the Gamblegram in its current form is unsuitable for visualizing acid-base perturbations using the Stewart-Figge approach. To overcome this problem the following modifications are proposed: 1) The positive bar is represented exclusively by strong ion difference ([SID]) 2) The negative bar is comprised of [HCO3̄], unmeasured ion charge ([X]) and albumin and inorganic phosphate charges which are considered proportional to their total concentrations assuming a standard pH of 7.4 (0.28⋅[Albumin] (g/l) and 1.8⋅[Phosphate] (mmol/l), respectively). The proposed method treats [HCO3̄] as a global index of the metabolic acid-base status, whose concentration is expressed as a function of the Stewart-Figge independent acid-base variables ([SID], [Albumin], [Phosphate] and [X]).

Functional Comorbidity Index and health-related quality of life in patients with obstructive sleep apnea.

INTRODUCTION: The role of comorbidities in determining health-related quality of life (HRQL) in obstructive sleep apnea (OSA) pa-tients has not been thoroughly investigated. Commonly used comorbidity tools, such as Charlson Comorbidity Index (CCI), have been designed with mortality as the outcome variable. A new tool, the Functional Comorbidity Index (FCI), has been especially developed to assess the effect of comorbidities on the "physical functioning" subscale of the Medical Outcomes Short Form-36 Health Survey (SF-36). AIMS: 1) To determine the role of FCI in the prediction of the effect of comorbidities on HRQL in OSA. 2) To determine whether FCI and CCI are equally robust in predicting the effect of comorbidities on HRQL in OSA. MATERIAL AND METHODS: Two hundred and fifty-five OSA patients were enrolled. Patients completed the SF-36 and the Medical Outcomes Study Sleep Scale (MOS-SS) forms, while their comorbidity status was assessed by FCI and CCI. The SF-36 physical (PCS-36) and mental component summary (MCS-36) scores were also calculated. RESULTS: PCS-36 was predicted by FCI (p < 0.001), male gender (p = 0.001), BMI (p = 0.002) and the "awakening with "breathlessness/headache" MOS-SS subscale (p = 0.011) (R2 = 0.348). Among these predictors, FCI exerted the most important quantitative effect. MCS-36 was predicted only by the "sleep disturbance" (p = 0.005) and the "awakening with breathlessness/headache" MOS-SS subscales (p < 0.001) (R2 = 0.221). CONCLUSIONS: In patients with OSA, FCI is an independent predictor of the physical aspect of their HRQL. FCI is more robust than CCI in assessing the effect of comorbidities on HRQL in OSA.

Effect of periodontal therapy on COPD outcomes: a systematic review.

BACKGROUND: Latest evidence suggests that periodontitis is prevalent among patients with chronic obstructive pulmonary disease (COPD), while recent studies have also reported a potential benefit of periodontal treatment on several COPD outcomes. This systematic review aims to determine the impact of periodontal treatment on exacerbation rate, lung function and quality of life of COPD patients. METHODS: A systematic search of electronic databases of PubMed, Scopus, Virtual Health Library, ScienceDirect, Wiley Online Library, Web of Science, ProQuest Dissertation and Theses Global and Google Scholar was conducted. Search restricted to studies involving human subjects which were published from January 2000 to March 2020 in English language. Distiller Systematic Review software was used for data management. Risk of bias was assessed using Risk of Bias 2 (RoB2) and Risk of Bias for non-randomized studies of intervention (ROBINS-I) tools. Overall quality of evidence was judged based on Grading of Recommendations Assessment, Development and Evaluation working group methodology. RESULTS: Out of 1442 articles retrieved, 7 full text articles were included in the review. Limited evidence suggests that periodontal treatment in patients with COPD and periodontitis is associated with reduced exacerbation frequency and a slower lung function decline rate, while its effects on quality of life remain unclear. In addition, periodontal treatment in COPD is associated with lower hospitalization rates and reduced all-cause mortality. Significant methodological differences were noted amongst included studies, while very low-to-moderate overall quality of evidence was demonstrated. CONCLUSIONS: Although it is reasonable to advise COPD patients not to neglect their dental health, further studies are warranted to determine the role of periodontal therapy on COPD clinical outcomes. TRIAL REGISTRATION: PROSPERO 2020 (CRD42020158481). https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020158481.

A simplified quantitative acid-base approach for patients with acute respiratory diseases.

The Stewart-Figge acid-base model has been criticized for being mathematically complex. We aimed to develop simpler formalisms, which can be used at the bedside. The following simplifications were used: (1) [Ca2+] and [Mg2+] are replaced by their mid-reference concentrations (2) pH is set to 7.4. In the new model [SIDa] is replaced by its adjusted form, [SIDa, adj] = [Na+] + [K+] - [Cl-] + 6.5 and [SIG] is replaced by "bicarbonate gap", [BICgap] = [SIDa, adj] - (0.28⋅[Albumin]) - (1.82⋅[Phosphatei])- [HCO3̄]. The diagnostic performance of the model was tested in 210 patients with acute respiratory diseases and 17 healthy volunteers. [BICgap] was also compared to albumin-corrected anion gap ([AGc]). The concordant correlation coefficient between [SIDa, adj] and [SIDa] and between [BICgap] and [SIG] was 0.98 in both comparisons. The mean bias (limits of agreement) of [SIDa, adj] - [SIDa] and of [BICgap] - [SIG] were 0.53 meq/l (- 0.46 to 1.53) and 0.50 meq/l (- 0.70 to 1.70), respectively. A [SIDa, adj] < 50.4 meq/l had an accuracy of 0.995 (p < 0.001) for the diagnosis of strong ion (SI) acidosis, while a [SIDa, adj] > 52.5 meq/l had an accuracy of 0.997 (p < 0.001) for the diagnosis of SI alkalosis. A [BICgap] > 11.6 meq/l predicted unmeasured ion (UI) acidosis with an accuracy of 0.997 (p < 0.001), while an [AGc] > 19.88 meq/l predicted UI acidosis with an accuracy of 0.994 (p < 0.001). The "[BICgap] model" is a reliable tool for the assessment of acid-base disorders in patients with acute respiratory diseases. [BICgap] is not inferior to [AGc] in the diagnosis of UI acidosis.

Respiratory Involvement in Patients with Neuromuscular Diseases: A Narrative Review.

Respiratory muscle weakness is a major cause of morbidity and mortality in patients with neuromuscular diseases (NMDs). Respiratory involvement in NMDs can manifest broadly, ranging from milder insufficiency that may affect only sleep initially to severe insufficiency that can be life threatening. Patients with neuromuscular diseases exhibit very often sleep-disordered breathing, which is frequently overlooked until symptoms become more severe leading to irreversible respiratory failure necessitating noninvasive ventilation (NIV) or even tracheostomy. Close monitoring of respiratory function and sleep evaluation is currently the standard of care. Early recognition of sleep disturbances and initiation of NIV can improve the quality of life and prolong survival. This review discusses the respiratory impairment during sleep in patients with NMDs, the diagnostic tools available for early recognition of sleep-disordered breathing and the therapeutic options available for overall respiratory management of patients with NMDs.

Comparison of a new simplified acid-base tool to the original Stewart-Figge approach: a study on cardiac surgical patients.

PURPOSE: To suggest a simplified method for strong ion gap ([SIG]) calculation. PATIENTS AND METHODS: To simplify [SIG] calculation, we used the following assumptions: (1) the major determinants of apparent strong ion difference ([SIDa]) are [Na+], [K+] and [Cl-] (2) [Ca2+] and [Mg2+] do not contribute significantly to [SIDa] variation and can be replaced by their reference concentrations (3) physiologically relevant pH variation is at the order of 10-2 and therefore we can assume a standard value of 7.4. In the new model, [SIDa] is replaced by its adjusted form, i.e. [SIDa,adj] = [Na+] + [K+] - [Cl-] + 6.5 and [SIG] is replaced by "bicarbonate gap", i.e. [BICgap] = [SIDa,adj] - (0.25·[Albumin]) - (2·[Phosphate]) - [HCO3-]. The model was tested in 224 postoperative cardiac surgical patients. RESULTS: Strong correlations were observed between [SIDa,adj] and [SIDa] (r = 0.93, p < 0.0001) and between [BICgap] and [SIG] (r = 0.95, p < 0.0001). The mean bias (limits of agreement) of [SIDa,adj] - [SIDa] and of [BICgap]-[SIG] was - 0.6 meq/l (- 2.7 to 1.5) and 0.2 meq/l (- 2 to 2.4), respectively. The intraclass correlation coefficients between [SIDa,adj] and [SIDa] and between [BICgap] and [SIG] were 0.90 and 0.95, respectively. The sensitivities and specificities for the prediction of a [lactate-] > 4 meq/l were 73.4 and 82.3% for a [BICgap] > 12.2 meq/l and 74.5 and 83.1% for a [SIG] > 12 meq/l, respectively. CONCLUSIONS: The [BICgap] model bears a very good agreement with the [SIG] model while being simpler and easier to apply at the bedside. [BICgap] could be used as an alternative tool for the diagnosis of unmeasured ion acidosis.

Successful management of drug-induced hypercapnic acidosis with naloxone and noninvasive positive pressure ventilation.

A 74-year-old man was referred to our hospital due to deteriorating level of consciousness and desaturation. His Glasgow Coma Scale was 6, and his pupils were constricted but responded to light. Chest radiograph was negative for significant findings. Arterial blood gas evaluation on supplemental oxygen revealed severe acute on chronic respiratory acidosis: pH 7.15; PCO2, 133 mm Hg; PO2,64 mm Hg; and HCO3, 31 mmol/L. He regained full consciousness (Glasgow Coma Scale, 15) after receiving a 0.4 mg dose of naloxone, but because of persistent severe respiratory acidosis (pH 7.21; PCO2, 105 mm Hg), he was immediately commenced on noninvasive positive pressure ventilation (NIV) displaying a remarkable improvement in arterial blood gas values within the next few hours. However, in the days that followed, he remained dependent on NIV, and he was finally discharged on a home mechanical ventilation prescription. In cases of drug-induced respiratory depression, NIV should be regarded as an acceptable treatment, as it can provide ventilatory support without the increased risks associated with invasive mechanical ventilation.

Effect of the independent acid base variables on anion gap variation in cardiac surgical patients: a Stewart-Figge approach.

PURPOSE: To determine the effect of each of independent acid base variables on the anion gap (AG) value in cardiac surgical patients. METHODS: This retrospective study involved 128 cardiac surgical patients admitted for postoperative care. The variation of AG (AGvar) between the day of admission and the first postoperative day was correlated via a multiple linear regression model with the respective variations of the independent acid base variables, that is, apparent strong ion difference (SIDa), strong ion gap (SIG), carbon dioxide (PCO2), and albumin and phosphate concentrations. RESULTS: The variations of all the above variables contributed significantly to the prediction of AGvar (adjusted R (2) = 0.9999, F = 201890.24, and P < 0.001). According to the standardized coefficients (ß), SIGvar (ß = 0.948, P < 0.001), [Albumin]var (ß = 0.260, P < 0.001), and [Phosphate]var (ß = 0.191, P < 0.001) were the major determinants of AGvar with lesser contributions from SIDa, var (ß = 0.071, P < 0.001) and PCO2, var (ß = -0.067, P < 0.001). CONCLUSIONS: All the independent acid base variables contribute to the prediction of the AG value. However, albumin and phosphate and SIG variations seem to be the most important predictors, while AG appears to be rather stable with changes in PCO2 and SIDa.

The base excess gap is not a valid tool for the quantification of unmeasured ions in cardiac surgical patients: a retrospective observational study.

BACKGROUND: The base excess gap (BE(gap)) method is commonly used for the quantification of unmeasured ions in critically ill patients. However, it has never been validated against the standard quantitative acid-base approach. OBJECTIVE: To compare the BE(gap) as a tool for the prediction of the excess of unmeasured ions with the offset of strong ion gap (SIG) from its reference value. DESIGN: A retrospective observational study. SETTING: Adult ICU in a tertiary hospital. PATIENTS: One hundred and thirty-five cardiac surgical patients admitted for postoperative care. INTERVENTIONS: None. MAIN OUTCOME MEASURES: BE(gap) was calculated as BE(gap) = SBE - BE(si) - BE(wa), where SBE is the standard base excess, BE(si) is the partition due to strong ions ([Na+]-[Cl-]-[lactate-] - 30.5) and BE(wa) is the partition due to weak acids [0.25×{42 - (albumin)}]. The deviation of the observed SIG (SIG(ob)) from its reference value was calculated as deltaSIG = 2.85 - SIG(ob). We used Bland-Altman and concordance correlation analysis to compare BE(gap) with deltaSIG. A bias of ±1 meq l(-1) with limits of agreement of ±2 meq l(-1) and a concordant correlation coefficient of more than 0.9 were considered to indicate a strong agreement. RESULTS: The concordant correlation coefficient between BE(gap) and deltaSIG was 0.702. The mean bias between the two variables was 1.8 meq l(-1), with a lower limit of agreement of -0.9 meq l(-1) and an upper limit of agreement of 4.4 meq l(-1). CONCLUSION: The BE gap method cannot reliably quantify the unmeasured ion excess in cardiac surgical patients. Clinicians should use the full Stewart-Figge model for quantitative acid-base assessments.

Ventilator-associated sinusitis in adults: systematic review and meta-analysis.

OBJECTIVE: To review the epidemiology, risk factors for, treatment and outcome of ventilator-associated sinusitis (VAS). METHODS: We performed a systematic review and meta-analysis of available data without time restrictions. A conservative random effects model was employed to calculate pooled odds ratios (OR) and 95% confidence intervals (CIs). RESULTS: Out of 620 retrieved reports, 31 papers fulfilled our inclusion criteria. Infectious sinusitis affects 27% of mechanically ventilated patients and was found to be the cause of undetermined fever in 25% of the cases. Although radiographic VAS was higher in nasotracheally compared to orotracheally intubated patients (OR 4.66, 95% CI 1.35-16.13), clinical VAS was not (3.67, 0.80-6.81). The presence of VAS has been associated with the presence of VAP (3.66, 1.81-7.37) or bacteremia (6.85, 2.14, 21.92); however, it is unknown whether an etiologic relationship between them exists. In patients with concomitant VAS and VAP or bloodstream infections identical pathogens are isolated in 59% and 20% of the cases, respectively. The presence as opposed to absence of VAS was not associated with excess mortality (1.02, 0.35-3.01). CONCLUSION: VAS is a common infection in critically ill adults and correlates with other important infectious complications.

Strong ion reserve: a viewpoint on acid base equilibria and buffering.

Evidence suggests that strong ions can exist reversibly bound to proteins in a pH-dependent manner and that they can be recruited into the biological solution, modulating its strong ion difference in a process that opposes the acid base disturbances imposed on the system. These recruitable strong ions represent the solution's 'strong ion reserve'. The physiologic [corrected] role of these protein-bound strong ions [corrected] in the buffering of acid base disorders is discussed.

Frequency, prevention, outcome and treatment of ventilator-associated tracheobronchitis: systematic review and meta-analysis.

OBJECTIVE: To clarify issues regarding the frequency, prevention, outcome, and treatment of patients with ventilator-associated tracheobronchitis (VAT), which is a lower respiratory tract infection involving the tracheobronchial tree, while sparing the lung parenchyma. METHODS: We performed a systematic review and meta-analysis of relevant available data, gathered though searches of PubMed, Scopus, and reference lists, without time restrictions. A conservative random effects model was used to calculate pooled odds ratios (OR) and 95% confidence intervals (CI). RESULTS: Out of the 564 initially retrieved articles, 17 papers were included. Frequency of VAT was 11.5%. Selective digestive decontamination was not proved an effective preventive strategy against VAT (OR: 0.62, 95% CI: 0.31e1.26). Presence, as opposed to the absence, of VAT was not associated with higher attributable mortality (OR: 1.02, 95% CI: 0.57e1.81). Administration of systemic antimicrobials (with or without inhaled ones), as opposed to placebo or no treatment, in patients with VAT was not associated with lower mortality (OR: 0.56, 95% CI: 0.27e1.14). Most of the studies providing relevant data noted that administration of antimicrobial agents, as opposed to placebo or no treatment, in patients with VAT was associated with lower frequency of subsequent pneumonia and more ventilator-free days, but without shorter length of intensive care unit stay or shorter duration of mechanical ventilation. CONCLUSIONS: Approximately one tenth of mechanically ventilated patients suffer from VAT. Antimicrobial treatment of patients with VAT may protect against the development of subsequent ventilator-associated pneumonia and improve weaning outcome.

Infections related to airway stenting: a systematic review.

BACKGROUND: Airway stenting is nowadays an established method for the palliative and/or curative treatment of central airways obstruction. However, complications related to the use of airway stents have been reported. OBJECTIVE: We endeavored to systematically evaluate the currently available evidence regarding the infections associated with airway stenting. METHODS: We independently searched in PubMed for relevant reports. We considered articles which reported on clinical infections related to airway stenting. A case was identified as stent-associated respiratory tract infection (SARTI) according to the authors of the individual papers, based on clinical findings with or without radiological or microbiological confirmation. RESULTS: Twenty-three articles (19 cohorts/case series and 4 case reports), involving 501 patients with airway stents, were included. The indication for airway stenting was malignancy and benign disease in 45 and 55% of the included patients, respectively. Ninety-three (19%) out of the 501 stented patients experienced SARTI. Pneumonia was the most common type of SARTI (47%), followed by bronchial infection (24%), cavitary pneumonia/lung abscess and intraluminal fungus ball. Staphylococcus aureus (39%) and Pseudomonas aeruginosa (28%) were the most commonly identified pathogens. Twenty-six (68%) out of the 38 patients with SARTI, for whom outcome data were available, died. CONCLUSION: The accumulated and evaluated evidence suggests that SARTI probably involves 1 in 5 patients with airway stent. Although the possibility of SARTI should not discourage the interventional pneumologists from inserting airway stents, the data seem to underline the urgent need for establishing a consensus definition and diagnostic criteria for SARTI.

Administration of antibiotics via the respiratory tract as monotherapy for pneumonia.

There is increasing interest in applying alternatives to the systemic modes of administration of antimicrobial agents for the treatment of patients with pneumonia. We endeavored to accumulate and evaluate the published evidence on the role of aerosolized antimicrobials administered as monotherapy for patients with pneumonia through searches of PubMed, Scopus and relevant bibliographies. Seven relevant studies (one randomized controlled trial, four case series and two case reports), including 63 patients, were identified; 37% (23 out of 63) and 63% (40 out of 63) of these patients suffered from community-acquired and nosocomial (including ventilator-associated) pneumonia, respectively. Acinetobacter baumannii (41%), Gram-positive cocci (37%) and Pseudomonas aeruginosa (16%) were the pathogens most frequently isolated from sputum, tracheal aspirates, bronchoalveolar lavage and bronchial brush specimens. Colistin (49%), penicillin (37%) and aminoglycosides (17%) were the antimicrobials administered via the respiratory tract. Concurrent systemic antimicrobials (without activity against the isolated pathogens) were given to 33% (21 out of 63) of patients. Clinical cure and bacteriological eradication from the aforementioned specimens were observed in 86% (54 out of 63) and 85% (33 out of 39) of patients, respectively. For the 31 patients for whom data were available, all-cause mortality and attributable mortality were 36% (11 out of 31) and 10% (three out of 31), respectively. The very limited published data preclude any strong conclusions; however, the available data seem to suggest that aerosolized antimicrobial monotherapy for pneumonia should not be a priori excluded when systemic access is unavailable, denied by the patient or when concerns exist regarding bioavailability in the lungs or systemic toxicity. Clinicians are encouraged to publish any relevant experience in order for a considerable body of literature to be accumulated.