![]() ![]() Challanges of capnography during sedation.Capnography – American Academy of Pediatrics – Monitoring guidelines during sedation.Monitored Anesthesia Care- Injury and Liability.Speciality Applications Toggle sub-menu.About Author: Bhavani Shankar Kodali MD.Hypocapnia may promote endogenous production of lactate (so-called “lactic alkalosis”).The net effect is an impairment in ventilation-perfusion matching, which may exacerbate hypoxemia. Global hypocapnia throughout the lung causes bronchoconstriction and attenuation of hypoxic pulmonary vasoconstriction.Among intubated patients with ventilator-induced hypocapnia, this may cause patients to stop triggering breaths and simply “ride” the ventilator (generally not a desirable situation, as it may promote atelectasis and muscle atrophy). Hypocapnia will suppress the respiratory drive.Cerebral hypoperfusion due to hypercapnia may contribute to symptoms of a panic attack (e.g., confusion and dizziness).In very rare situations with impending herniation, hypocapnia may have therapeutic benefit (further discussion of this here). Generally, the dominant effect is a deleterious reduction in brain perfusion. This has two major consequences: a reduction in intracranial pressure, and a reduction in brain perfusion. Reduced CO2 triggers cerebral vasoconstriction.(Remember, one of the classic features of systemic inflammatory response syndrome is tachypnea). Respiratory alkalosis may be an early sign of sepsis, preceding hypoxemia or hypotension. ![]() Cirrhosis is a common cause of persistent respiratory alkalosis that is often encountered among intubated patients.Central neurogenic hyperventilation (e.g., meningitis, encephalitis, trauma, stroke).Excessive mechanical ventilation among intubated patients (iatrogenic).(2) Normal chest x-ray may still occur with some respiratory etiologies: mild cardiogenic pulmonary edema, pericardial tamponade, asthma, or pulmonary embolism.(1) Abnormal chest x-ray may suggest pulmonary disease as the cause.Pulmonary irritation can also drive dyspnea and increases in ventilation, likewise leading to hypocapnia. Hypoxemia itself can stimulate the respiratory drive, causing hypocapnia. Hypocapnia can be caused by nearly any pulmonary disease (e.g., pneumonia, asthma, pulmonary edema, pulmonary embolism, pneumothorax). ![]()
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