Respiratory care
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Hypercapnia and hypocapnia commonly complicate conditions that are present in critically ill patients. Both conditions have important physiologic effects that may impact the clinical management of these patients. For instance, hypercapnia results in bronchodilation and enhanced hypoxic vasoconstriction, leading to improved ventilation/perfusion matching. ⋯ Buffering hypercapnic acidosis should be considered only for a specific clinical indication (eg, hemodynamic instability). For clinicians choosing to buffer hypercapnic acidosis, tris-hydroxymethyl aminomethane is recommended over sodium bicarbonate, as it is more effective in correcting pH and is not associated with increased carbon dioxide production. Future studies should aim to address these areas of uncertainty to help guide clinicians in the therapeutic use and management of hypercapnia/hypocapnia in critically ill patients.
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Oxygen is essential for normal aerobic metabolism in mammals. Hypoxia is the presence of lower than normal oxygen content and pressure in the cell. Causes of hypoxia include hypoxemia (low blood oxygen content and pressure), impaired oxygen delivery, and impaired cellular oxygen uptake/utilization. ⋯ Clinical management of tissue hypoxia usually focuses on global hypoxemia and oxygen delivery. As we move into the future, the clinical focus needs to change to assessing and managing mission-critical regional hypoxia to avoid unnecessary and potential toxic global strategies. We also need to focus on understanding and better harnessing the body's own adaptive mechanisms to hypoxia.