Effectiveness of acetazolamide for reversal of metabolic alkalosis in weaning COPD patients from mechanical ventilation

Combination Diuretic Therapy With Thiazides: A Systematic Review on the Beneficial Approach to Overcome Refractory Fluid Overload in Heart Failure

Heart failure (HF) is a notable public health issue, and intravenous loop diuretics are frequently employed to address acute decompensated heart failure (ADHF) and alleviate symptoms of congestion. However, prolonged use of loop diuretics can lead to drug resistance, and some patients experience refractory volume overload that does not respond to treatment. Sequential nephron blockade, which involves combining loop and thiazide diuretics, has been proposed as a strategy to overcome diuretic resistance and improve fluid overload management. This systematic review aims to critically evaluate the effectiveness and safety of this combination diuretic therapy. Following the directives detailed in the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a comprehensive search was conducted. Eligibility criteria were established to select relevant studies, including the requirement for studies to be conducted on human subjects and published as free full-text papers in English within the last 10 years. Several databases were searched using a combination of Medical Subject Heading (MeSH) phrases and keywords related to heart failure, loop diuretics, and thiazide diuretics. The search yielded 948 references, and after screening titles, abstracts, and full-text papers, eight final studies (five observational studies and three randomized control trials) were included in the review. Based on the findings of this systematic review, there is substantial evidence to endorse the efficacy of combination diuretic therapy of loop and thiazide diuretics in augmenting diuresis and enhancing outcomes for patients who exhibit insufficient responses to single-agent diuretics. Additionally, the review provides valuable insights about the timing and type of diuretics to use, helping clinicians make informed therapeutic decisions. However, to ensure patient safety and well-being, it is imperative to take into account the potential for electrolyte disturbances and impacts on renal function, necessitating diligent and vigilant monitoring as well as effective management strategies. In light of these findings, further research is warranted to optimize the dosing regimens and to delve deeper into the long-term safety and efficacy of combination therapy. Such research endeavors will undoubtedly contribute to refining treatment approaches and advancing patient care in the field of HF management.

Acid-Base Disorders in the Critically Ill Patient

Acid-base disorders are common in the intensive care unit. By utilizing a systematic approach to their diagnosis, it is easy to identify both simple and mixed disturbances. These disorders are divided into four major categories: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis. Metabolic acidosis is subdivided into anion gap and non-gap acidosis. Distinguishing between these is helpful in establishing the cause of the acidosis. Anion gap acidosis, caused by the accumulation of organic anions from sepsis, diabetes, alcohol use, and numerous drugs and toxins, is usually present on admission to the intensive care unit. Lactic acidosis from decreased delivery or utilization of oxygen is associated with increased mortality. This is likely secondary to the disease process, as opposed to the degree of acidemia. Treatment of an anion gap acidosis is aimed at the underlying disease or removal of the toxin. The use of therapy to normalize the pH is controversial. Non-gap acidoses result from disorders of renal tubular H + transport, decreased renal ammonia secretion, gastrointestinal and kidney losses of bicarbonate, dilution of serum bicarbonate from excessive intravenous fluid administration, or addition of hydrochloric acid. Metabolic alkalosis is the most common acid-base disorder found in patients who are critically ill, and most often occurs after admission to the intensive care unit. Its etiology is most often secondary to the aggressive therapeutic interventions used to treat shock, acidemia, volume overload, severe coagulopathy, respiratory failure, and AKI. Treatment consists of volume resuscitation and repletion of potassium deficits. Aggressive lowering of the pH is usually not necessary. Respiratory disorders are caused by either decreased or increased minute ventilation. The use of permissive hypercapnia to prevent barotrauma has become the standard of care. The use of bicarbonate to correct the acidemia is not recommended. In patients at the extreme, the use of extracorporeal therapies to remove CO 2 can be considered.

Diuretic combinations in critically ill patients with respiratory failure: A systematic review and meta-analysis

BACKGROUND

In patients with respiratory failure, loop diuretics remain the cornerstone of the treatment to maintain fluid balance, but resistance is common.

AIM

To determine the efficacy and safety of common diuretic combinations in critically ill patients with respiratory failure.

METHODS

We searched MEDLINE, Embase, Cochrane Library and PROSPERO for studies reporting the effects of a combination of a loop diuretic with another class of diuretic. A meta-analysis using mean differences (MD) with 95% confidence interval (CI) was performed for the 24-h fluid balance (primary outcome) and the 24-h urine output, while descriptive statistics were used for safety events.

RESULTS

Nine studies totalling 440 patients from a total of 6510 citations were included. When compared to loop diuretics alone, the addition of a second diuretic is associated with an improved negative fluid balance at 24 h [MD: -1.06 L (95%CI: -1.46; -0.65)], driven by the combination of a thiazide plus furosemide [MD: -1.25 L (95%CI: -1.68; -0.82)], while no difference was observed with the combination of a loop-diuretic plus acetazolamide [MD: -0.40 L (95%CI: -0.96; 0.16)] or spironolactone [MD: -0.65 L (95%CI: -1.66; 0.36)]. Heterogeneity was high and the report of clinical and safety endpoints varied across studies.

CONCLUSION

Based on limited evidence, the addition of a second diuretic to a loop diuretic may promote diuresis and negative fluid balance in patients with respiratory failure, but only when using a thiazide. Further larger trials to evaluate the safety and efficacy of such interventions in patients with respiratory failure are required.

Diuretic strategies in patients with resistance to loop-diuretics in the intensive care unit: A retrospective study from the MIMIC-III database

PURPOSE

To investigate various diuretic strategies to alleviate loop-diuretics resistance in critically ill patients.

MATERIALS AND METHOD

ICU adults requiring more than 1 mg/kg/day of furosemide, from the MIMIC-III database. Four diuretic strategies were investigated: incremental dose of loop diuretics, continuous infusion, combinations with a second class of diuretics and administration of intravenous albumin. A generalized estimating equation was used to investigate the associations between these strategies and endpoints. The primary outcome was the 24-h urine output and secondary endpoints included fluid balance, weight change, electrolyte and acid-base abnormalities, kidney replacement therapy initiation, and mortality.

RESULTS

A total of 7645 ICU stays from 6358 patients were included. After adjustment, the use of continuous loop-diuretic infusion was associated with a higher 24-h urine output (β: 732, 95% CI:669-795, p < 0.001), lower 24-h fluid balance (p < 0.001) and greater weight loss at 48-h (p < 0.001). Thiazide- and carbonic anhydrase inhibitor combinations were both associated with higher urine output (p < 0.001) and weight loss at 48-h (p < 0.01), while intravenous albumin was associated with fluid gain (p < 0.001). Risks of electrolyte and metabolic disturbances varied across diuretic strategies.

CONCLUSIONS

Continuous loop-diuretic infusion and thiazide- or acetazolamide-loop diuretic combinations increased urine output significantly, leading to a negative fluid balance and weight loss.

Metabolic Alkalosis in the Pediatric Patient: Treatment Options in the Pediatric ICU or Pediatric Cardiothoracic ICU Setting

Metabolic alkalosis is characterized by the primary elevation of the serum bicarbonate concentration with a normal or elevated partial pressure of carbon dioxide. Although there may be several potential etiologies in the critically ill patient in the pediatric or cardiothoracic intensive care unit, metabolic alkalosis most commonly results from diuretic therapy with chloride loss. In most cases, the etiology can be determined by a review of the patient's history and medication record. Although generally innocuous with limited impact on physiologic function, metabolic alkalosis may impair central control of ventilation, especially when weaning from mechanical ventilation. The following manuscript presents the normal homeostatic mechanisms that control pH, reviews the etiology of metabolic alkalosis, and outlines the differential diagnosis. Options and alternatives for treatment including pharmacologic interventions are presented with a focus on these conditions as they pertain to the patient in the pediatric or cardiac intensive care unit.

Acetazolamide Causes Worsening Acidosis in Uncompensated COPD Exacerbations: Increased Awareness Needed for Patient Safety

BACKGROUND

Acetazolamide has been studied extensively in post-hypercapnic alkalosis as a tool to facilitate ventilator weaning in chronic obstructive pulmonary disease (COPD). It has also been utilized to facilitate respiratory drive in nonmechanically ventilated patients with COPD. Although this is generally a forgiving intervention, providers must carefully select patients for this medication, as it can cause severe acidosis and deterioration of clinical status in severe COPD cases. The present report describes two cases of patients who developed worsening acidosis and hypercapnia after receiving acetazolamide in acute respiratory failure.

CASE REPORT

Case 1 was a 72-year-old obese male with COPD who was dependent on supplemental oxygen and presented to the emergency department (ED) with acute on chronic hypercapnic respiratory failure. He was given a one-time dose of acetazolamide in the ED for "respiratory failure made worse by severe metabolic alkalosis." His arterial blood gas (ABG) worsened overnight, accompanied by decreased mental status: pH 7.32, paCO₂ 82 mm Hg, paO₂ 50 mm Hg, HCO₃ 41.7 mmol/L, FiO₂ 32% to pH 7.21, paCO₂ 91.7 mm Hg, paO₂ 59 mm Hg, HCO₃ 36.6 mmol/L, and FiO₂ 32%. Case 2 was a 62-year-old male with COPD who was dependent on supplemental oxygen and presented to the ED with acute on chronic hypercapnic respiratory failure. He was given acetazolamide in the ED with similar results: ABG on presentation pH 7.37, paCO₂ 79.3 mm Hg, paO₂ 77.6 mm Hg, HCO₃ 45.5 mmol/L, and FiO₂ 32%. The next morning, ABG was pH 7.29, paCO₂ 79 mm Hg, paO₂ 77 mm Hg, HCO₃ 45.5 mmol/L, and FiO₂ 32%. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Acetazolamide given early in the uncompensated setting can worsen acidosis and potentiate clinical deterioration.

Carbonic anhydrase inhibitors in patients with respiratory failure and metabolic alkalosis: a systematic review and meta-analysis of randomized controlled trials

Background

Metabolic alkalosis is common in patients with respiratory failure and may delay weaning in mechanically ventilated patients. Carbonic anhydrase inhibitors block renal bicarbonate reabsorption, and thus reverse metabolic alkalosis. The objective of this systematic review is to assess the benefits and harms of carbonic anhydrase inhibitor therapy in patients with respiratory failure and metabolic alkalosis.

Methods

We searched the following electronic sources from inception to August 2017: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and SCOPUS. Randomized clinical trials were included if they assessed at least one of the following outcomes: mortality, duration of hospital stay, duration of mechanical ventilation, adverse events, and blood gas parameters. Teams of two review authors worked in an independent and duplicate manner to select eligible trials, extract data, and assess risk of bias of the included trials. We used meta-analysis to synthesize statistical data and then assessed the certainty of evidence using the GRADE methodology.

Results

Six eligible studies were identified with a total of 564 participants. The synthesized data did not exclude a reduction or an increase in mortality (risk ratio (RR) 0.94, 95% confidence interval (CI) 0.57 to 1.56) or in duration of hospital stay (mean difference (MD) 0.42 days, 95% CI −4.82 to 5.66) with the use of carbonic anhydrase inhibitors. Carbonic anhydrase inhibitor therapy resulted in a decrease in the duration of mechanical ventilation of 27 h (95% CI −50 to −4). Also, it resulted in an increase in PaO₂ (MD 11.37 mmHg, 95% CI 4.18 to 18.56) and a decrease in PaCO₂ (MD −4.98 mmHg, 95% CI −9.66, −0.3), serum bicarbonate (MD −5.03 meq/L, 95% CI −6.52 to −3.54), and pH (MD −0.04, 95% CI −0.07 to −0.01). There was an increased risk of adverse events in the carbonic anhydrase inhibitor group (RR 1.71, 95% CI 0.98 to 2.99). Certainty of evidence was judged to be low for most outcomes.

Conclusion

In patients with respiratory failure and metabolic alkalosis, carbonic anhydrase inhibitor therapy may have favorable effects on blood gas parameters. In mechanically ventilated patients, carbonic anhydrase inhibitor therapy may decrease the duration of mechanical ventilation. A major limitation of this finding was that only two trials assessed this clinically important outcome.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2207-6) contains supplementary material, which is available to authorized users.

Complications and Pharmacologic Interventions of Invasive Positive Pressure Ventilation During Critical Illness

Objective: To review the fundamentals of invasive positive pressure ventilation (IPPV) and the common complications and associated pharmacotherapeutic management in order to provide opportunities for pharmacists to improve patient outcomes. Data Sources: A MEDLINE literature search (1950-December 2017) was performed using the key search terms invasive positive pressure ventilation, mechanical ventilation, pharmacist, respiratory failure, ventilator associated organ dysfunction, ventilator associated pneumonia, ventilator bundles, and ventilator liberation. Additional references were identified from a review of literature citations. Study Selection and Data Extraction: All English-language original research and review reports were evaluated. Data Synthesis: IPPV is a common supportive care measure for critically ill patients. While lifesaving, IPPV is associated with significant complications including ventilator-associated pneumonia, sinusitis, organ dysfunction, and hemodynamic alterations. Optimization of pain and sedation management provides an opportunity for pharmacists to directly affect IPPV exposure. A number of pharmacotherapeutic interventions are related directly to prophylaxis against IPPV-associated adverse events or aimed at reduction of duration of IPPV. Conclusions: Enhanced knowledge of the common complications, associated pharmacotherapy, and monitoring strategies facilitate the pharmacist's ability to provide increased pharmacotherapeutic insight in a multidisciplinary intensive care unit setting.

Acetazolamide Therapy for Metabolic Alkalosis in Pediatric Intensive Care Patients

OBJECTIVE

Patients in PICUs frequently present hypochloremic metabolic alkalosis secondary to loop diuretic treatment, especially those undergoing cardiac surgery. This study evaluates the effectiveness of acetazolamide therapy for metabolic alkalosis in PICU patients.

DESIGN

Retrospective, observational study.

SETTING

A tertiary care children's hospital PICU.

PATIENTS

Children receiving at least a 2-day course of enteral acetazolamide.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic variables, diuretic treatment and doses of acetazolamide, urine output, serum electrolytes, urea and creatinine, acid-base excess, pH, and use of mechanical ventilation during treatment were collected. Patients were studied according to their pathology (postoperative cardiac surgery, decompensated heart failure, or respiratory disease). A total of 78 episodes in 58 patients were identified: 48 were carried out in cardiac postoperative patients, 22 in decompensated heart failure, and eight in respiratory patients. All patients received loop diuretics. A decrease in pH and PCO2 in the first 72 hours, a decrease in serum HCO3 (mean, 4.65 ± 4.83; p < 0.001), and an increase in anion gap values were observed. Urine output increased in cardiac postoperative patients (4.5 ± 2.2 vs 5.1 ± 2.0; p = 0.020), whereas diuretic treatment was reduced in cardiac patients. There was no significant difference in serum electrolytes, blood urea, creatinine, nor chloride after the administration of acetazolamide from baseline. Acetazolamide treatment was well tolerated in all patients.

CONCLUSIONS

Acetazolamide decreases serum HCO3 and PCO2 in PICU cardiac patients with metabolic alkalosis secondary to diuretic therapy. Cardiac postoperative patients present a significant increase in urine output after acetazolamide treatment.

Impact of acetazolamide use in severe exacerbation of chronic obstructive pulmonary disease requiring invasive mechanical ventilation

PURPOSE

To analyse the impact of acetazolamide (ACET) use in severe acute decompensation of chronic obstructive pulmonary disease requiring mechanical ventilation and intensive care unit (ICU) admission.

PATIENTS AND METHODS

Retrospective pair-wise, case-control study with 1:1 matching. Patients were defined as cases when they had received acetazolamide (500 mg per day) and as controls when they did not received it. Patients were matched according to age, severity on admission (pH, PaO2/FiO2 ratio) and SAPSII score. Our primary endpoint was the effect of ACET (500 mg per day) on the duration of mechanical ventilation. Our secondary endpoints were the effect of ACET on arterial blood gas parameters, ICU length of stay (LOS) and ICU mortality.

RESULTS

Seventy-two patients were included and equally distributed between the two studied groups. There were 66 males (92%). The mean age (± SD) was 69.7 ± 7.4 years ranging from 53 to 81 years. There were no differences between baseline characteristics of the two groups. Concomitant drugs used were also not significantly different between two groups. Mean duration of mechanical ventilation was not significantly different between ACET(+) and ACET(-) patients (10.6±7.8 days and 9.6±7.6 days, respectively; P = 0.61). Cases had a significantly decreased serum bicarbonate, arterial blood pH, and PaCO2 levels. We did not found any significant difference between the two studied groups in terms of ICU LOS. ICU mortality was also comparable between ACET(+) and ACET(-) groups (38% and 52%, respectively; P = 0.23).

CONCLUSION

Although our study some limitations, it suggests that the use of insufficient acetazolamide dosage (500 mg/d) ACET (500 mg per day) has no significant effect on the duration of mechanical ventilation in critically ill COPD patients requiring invasive mechanical ventilation. Our results should be confirmed or infirmed by further studies.

Acetazolamide therapy for metabolic alkalosis in critically ill pediatric patients

OBJECTIVE

Despite a paucity of supporting literature, acetazolamide is commonly used in critically ill children with metabolic alkalosis (elevated plasma bicarbonate [pHco-3] and pH). The objective of this study was to assess the change in 18 hours after initiation of acetazolamide therapy.

DESIGN

Retrospective study.

SETTING

PICU of an urban, tertiary-care children's hospital.

PATIENTS

Mechanically ventilated children (≤ 17 yr) with metabolic alkalosis (pHco-3 ≥ 35 mmol/L).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 153 consecutively screened patients, 61 patients (29 female patients) were enrolled: 18 cardiac patients (after congenital heart disease repair) and 43 noncardiac patients. The cardiac patients were younger than the noncardiac patients (median [interquartile range] age, 0.6 mo [0.3-2.5 mo] vs 7.4 mo [2.8-39.9 mo]; p < 0.00001) and had higher preacetazolamide baseline diuretic scores and urine output. The pHco-3 levels 18 hours after initiation of acetazolamide were reduced in the cohort as a whole (40.2 ± 4.8 to 36.2 ± 5.6 mmol/L; p < 0.001) and in the noncardiac patients, but they were unchanged in the cardiac patients. The PCO2 remained unchanged after acetazolamide in both subgroups. Because young age and presence of cardiac disease were potential confounders, the 20 noncardiac patients who are 6 months old or younger were compared with the cardiac subgroup and demonstrated reduced pHco-3 after acetazolamide and lower preacetazolamide baseline diuretic score and urine output.

CONCLUSION

Acetazolamide reduces pHco-3 concentration in critically ill, mechanically ventilated children overall, but it did not do so in cardiac patients in our cohort, even in comparison with noncardiac patients of a similar age. These findings do not support the current use of acetazolamide for metabolic alkalosis in critically ill children with congenital heart disease. Further study is required to determine why these cardiac patients respond differently to acetazolamide than noncardiac patients and whether this response impacts important clinical outcomes, for example, weaning mechanical ventilation.

Population pharmacodynamic modeling and simulation of the respiratory effect of acetazolamide in decompensated COPD patients

BACKGROUND

Chronic obstructive pulmonary disease (COPD) patients may develop metabolic alkalosis during weaning from mechanical ventilation. Acetazolamide is one of the treatments used to reverse metabolic alkalosis.

METHODS

619 time-respiratory (minute ventilation, tidal volume and respiratory rate) and 207 time-PaCO2 observations were obtained from 68 invasively ventilated COPD patients. We modeled respiratory responses to acetazolamide in mechanically ventilated COPD patients and then simulated the effect of increased amounts of the drug.

RESULTS

The effect of acetazolamide on minute ventilation and PaCO2 levels was analyzed using a nonlinear mixed effect model. The effect of different ventilatory modes was assessed on the model. Only slightly increased minute ventilation without decreased PaCO2 levels were observed in response to 250 to 500 mg of acetazolamide administered twice daily. Simulations indicated that higher acetazolamide dosage (>1000 mg daily) was required to significantly increase minute ventilation (P<.001 vs pre-acetazolamide administration). Based on our model, 1000 mg per day of acetazolamide would increase minute ventilation by >0.75 L min(-1) in 60% of the population. The model also predicts that 45% of patients would have a decrease of PaCO2>5 mmHg with doses of 1000 mg per day.

CONCLUSIONS

Simulations suggest that COPD patients might benefit from the respiratory stimulant effect after the administration of higher doses of acetazolamide.

Acetazolamide improves oxygenation in patients with respiratory failure and metabolic alkalosis

INTRODUCTION

Coexistent respiratory failure and metabolic alkalosis is a common finding. Acidotic diuretics cause a fall in pH that may stimulate respiration.

OBJECTIVE

The purpose of the study was to evaluate the effectiveness of short-term treatment with acetazolamide for combined respiratory failure and metabolic alkalosis.

METHODS

A randomised, placebo-controlled and double-blind parallel group trial where oral acetazolamide 250 mg three times a day for 5 days were administered to patients hospitalised for respiratory failure because of a pulmonary disease (Pa O2 ≤ 8 kPa and/or Pa CO2 ≥ 7 kPa) who had concurrent metabolic alkalosis [base excess (BE) ≥ 8 mmol/L]. Pa O2 after 5 days was the primary effect variable. Secondary effect variables were Pa CO2 , BE and pH on day 5, and the total number of days in hospital.

RESULTS

Of 70 patients enrolled (35 in each group), data from 54 were analysed per protocol, while last observation carried forward was used for the remaining 16. During the 5-day treatment, Pa O2 increased on average 0.81 kPa in the placebo group and 1.41 kPa in the acetazolamide group. After adjustment for baseline skewness, the difference was statistically significant (adjusted mean difference 0.55 kPa, 95% confidence interval 0.03-1.06). Pa CO2 decreased in both groups, but the difference was not statistically significant. As expected, pH and BE decreased markedly in the acetazolamide group.

CONCLUSION

Acetazolamide may constitute a useful adjuvant treatment mainly to be considered in selected patients with respiratory failure combined with prominent metabolic alkalosis or where non-invasive ventilation is insufficient or infeasible.

Acetazolamide: a second wind for a respiratory stimulant in the intensive care unit?

Patients with chronic obstructive pulmonary disease (COPD) are affected by episodes of respiratory exacerbations, some of which can be severe and may necessitate respiratory support. Prolonged invasive mechanical ventilation is associated with increased mortality rates. Persistent failure to discontinue invasive mechanical ventilation is a major issue in patients with COPD. Pure or mixed metabolic alkalosis is a common finding in the intensive care unit (ICU) and is associated with a worse outcome. In patients with COPD, the condition is called post-hypercapnic alkalosis and is a complication of mechanical ventilation. Reversal of metabolic alkalosis may facilitate weaning from mechanical ventilation of patients with COPD. Acetazolamide, a non-specific carbonic anhydrase inhibitor, is one of the drugs employed in the ICU to reverse metabolic alkalosis. The drug is relatively safe, undesirable effects being rare. The compartmentalization of the different isoforms of the carbonic anhydrase enzyme may, in part, explain the lack of evidence of the efficacy of acetazolamide as a respiratory stimulant. Recent findings suggest that the usually employed doses of acetazolamide in the ICU may be insufficient to significantly improve respiratory parameters in mechanically ventilated patients with COPD. Randomized controlled trials using adequate doses of acetazolamide are required to address this issue.

Population pharmacodynamic model of bicarbonate response to acetazolamide in mechanically ventilated chronic obstructive pulmonary disease patients

INTRODUCTION

Acetazolamide is commonly given to chronic obstructive pulmonary disease (COPD) patients with metabolic alkalosis. Little is known of the pharmacodynamics of acetazolamide in the critically ill. We undertook the pharmacodynamic modeling of bicarbonate response to acetazolamide in COPD patients under mechanical ventilation.

METHODS

This observational, retrospective study included 68 invasively ventilated COPD patients who received one or multiple doses of 250 or 500 mg of acetazolamide during the weaning period. Among the 68 investigated patients, 207 time-serum bicarbonate observations were available for analysis. Population pharmacodynamics was modeled using a nonlinear mixedeffect model. The main covariates of interest were baseline demographic data, Simplified Acute Physiology Score II (SAPS II) at ICU admission, cause of respiratory failure, co-prescription of drugs interfering with the acid-base equilibrium, and serum concentrations of protein, creatinin, potassium and chloride. The effect of acetazolamide on serum bicarbonate levels at different doses and in different clinical conditions was subsequently simulated in silico.

RESULTS

The main covariates interacting with acetazolamide pharmacodynamics were SAPS II at ICU admission (P = 0.01), serum chloride (P < 0.001) and concomitant administration of corticosteroids (P = 0.02). Co-administration of furosemide significantly decreased bicarbonate elimination. Acetazolamide induced a decrease in serum bicarbonate with a dose-response relationship. The amount of acetazolamide inducing 50% of the putative maximum effect was 117 ± 21 mg. According to our model, an acetazolamide dosage > 500 mg twice daily is required to reduce serum bicarbonate concentrations > 5 mmol/L in the presence of high serum chloride levels or coadministration of systemic corticosteroids or furosemide.

CONCLUSIONS

This study identified several covariates that influenced acetazolamide pharmacodynamics and could allow a better individualization of acetazolamide dosing when treating COPD patients with metabolic alkalosis.