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Clinical Journal of the American... Jan 2023Acid-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...
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.
Topics: Humans; Bicarbonates; Critical Illness; Acidosis; Acid-Base Equilibrium; Acid-Base Imbalance; Alkalosis
PubMed: 35998977
DOI: 10.2215/CJN.04500422 -
Respirology (Carlton, Vic.) Apr 2019Non-invasive ventilation (NIV) with bilevel positive airway pressure is a non-invasive technique, which refers to the provision of ventilatory support through the... (Review)
Review
Non-invasive ventilation (NIV) with bilevel positive airway pressure is a non-invasive technique, which refers to the provision of ventilatory support through the patient's upper airway using a mask or similar device. This technique is successful in correcting hypoventilation. It has become widely accepted as the standard treatment for patients with hypercapnic respiratory failure (HRF). Since the 1980s, NIV has been used in intensive care units and, after initial anecdotal reports and larger series, a number of randomized trials have been conducted. Data from these trials have shown that NIV is a valuable treatment for HRF. This review aims to explore the principal areas in which NIV can be useful, focusing particularly on patients with acute HRF (AHRF). We will update the evidence base with the goal of supporting clinical practice. We provide a practical description of the main indications for NIV in AHRF and identify the group of patients with hypercapnic failure who will benefit most from the application of NIV.
Topics: Acute Disease; Humans; Hypercapnia; Noninvasive Ventilation; Pulmonary Disease, Chronic Obstructive; Respiratory Insufficiency
PubMed: 30636373
DOI: 10.1111/resp.13469 -
Pulmonology 2019Chronic Obstructive Pulmonary Disease (COPD) history is characterized by episodes of exacerbation of varying severity, featured by acute worsening of respiratory...
Chronic Obstructive Pulmonary Disease (COPD) history is characterized by episodes of exacerbation of varying severity, featured by acute worsening of respiratory symptoms, commonly precipitated by respiratory tract infection. The recent ERS/ATS clinical practice guidelines strongly recommend the application of non invasive ventilation (NIV) for patients with acute respiratory failure (ARF) leading to acute or acute-on-chronic respiratory acidosis (pH 7.35) and not for those patients with acute exacerbation of COPD (AECOPD) and hypercapnia who are not acidotic. In recent years, High-Flow through Nasal Cannula (HFNC) has been introduced in the clinical practice. We designed the present systematic review of the literature to assess all effects of HFNC use reported in exacerbated COPD patients. In this setting, HFNC is able to keep PaCO2 unmodified, while oxygenation slightly deteriorates as opposed to NIV. Furthermore, the work of breathing is reduced with HFNC by a similar extent to NIV, while it increases by 40-50% during conventional oxygen therapy (COT). HFNC is also reported to be more comfortable than COT and NIV. Despite these results, little and limited evidence for improved clinical outcomes is currently available.
Topics: Acidosis, Respiratory; Blood Gas Analysis; Disease Progression; Humans; Hypercapnia; Noninvasive Ventilation; Positive-Pressure Respiration; Pulmonary Disease, Chronic Obstructive; Respiratory Insufficiency; Respiratory Rate; Respiratory Therapy; Treatment Outcome; Work of Breathing
PubMed: 31591056
DOI: 10.1016/j.pulmoe.2019.08.001 -
Journal of Applied Physiology... Apr 2007Acetazolamide, a potent carbonic anhydrase (CA) inhibitor, is the most commonly used and best-studied agent for the amelioration of acute mountain sickness (AMS). The... (Review)
Review
Acetazolamide, a potent carbonic anhydrase (CA) inhibitor, is the most commonly used and best-studied agent for the amelioration of acute mountain sickness (AMS). The actual mechanisms by which acetazolamide reduces symptoms of AMS, however, remain unclear. Traditionally, acetazolamide's efficacy has been attributed to inhibition of CA in the kidneys, resulting in bicarbonaturia and metabolic acidosis. The result is offsetting hyperventilation-induced respiratory alkalosis and allowance of chemoreceptors to respond more fully to hypoxic stimuli at altitude. Studies performed on both animals and humans, however, have shown that this explanation is unsatisfactory and that the efficacy of acetazolamide in the context of AMS is likely due to a multitude of effects. This review summarizes the known systemic effects of acetazolamide and incorporates them into a model encompassing several factors that are likely to play a key role in the drug's efficacy. Such factors include not only metabolic acidosis resulting from renal CA inhibition but also improvements in ventilation from tissue respiratory acidosis, improvements in sleep quality from carotid body CA inhibition, and effects of diuresis.
Topics: Acetazolamide; Adaptation, Physiological; Altitude Sickness; Carbonic Anhydrase Inhibitors; Humans; Oxygen; Oxygen Consumption
PubMed: 17023566
DOI: 10.1152/japplphysiol.01572.2005 -
Interface Focus Apr 2021Carbon dioxide (CO), a primary product of oxidative metabolism, can be sensed by eukaryotic cells eliciting unique responses via specific signalling pathways. Severe... (Review)
Review
Carbon dioxide (CO), a primary product of oxidative metabolism, can be sensed by eukaryotic cells eliciting unique responses via specific signalling pathways. Severe lung diseases such as chronic obstructive pulmonary disease are associated with hypoventilation that can lead to the elevation of CO levels in lung tissues and the bloodstream (hypercapnia). However, the pathophysiological effects of hypercapnia on the lungs and specific lung cells are incompletely understood. We have recently reported using combined unbiased molecular approaches with studies in mice and cell culture systems on the mechanisms by which hypercapnia alters airway smooth muscle contractility. In this review, we provide a pathophysiological and mechanistic perspective on the effects of hypercapnia on the lung airways and discuss the recent understanding of high CO modulation of the airway contractility.
PubMed: 33628424
DOI: 10.1098/rsfs.2020.0021