Questions and Answers
Which of the following can lead to hypoxemia during the washout of nitrous oxide?
Hypoxic pulmonary vasoconstriction (HPV) increases blood flow to poorly ventilated areas of the lung.
False
Name one drug that may inhibit hypoxic pulmonary vasoconstriction.
All inhalations
The presence of ___________ may decrease diffusion capacity and result in arterial hypoxemia in the PACU.
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What causes noncardiogenic pulmonary edema in the PACU?
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Match the following lung diseases with their resultant effects:
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Describe what causes cardiogenic pulmonary edema in the PACU.
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High inspired FiO2 through a face mask can help prevent hypoxemia during nitrous oxide washout.
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What is the likely effect of anesthesia drugs on the CO2 response curve?
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The apnea threshold increases after shifting the CO2 response curve to the right.
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What should be administered to reverse arterial hypoxemia due to hypercapnia in the PACU?
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In cases of inadequate reversal of neuromuscular blockade, administer _________ or _________.
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Match the cause of hypercapnia with the appropriate treatment:
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Which method is effective for reversing hypercapnia caused by neurologic injury during surgery?
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Inadequate analgesia can cause hypercapnia, which can be managed by administering more pain medications.
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Name one treatment for bronchospasm in the PACU.
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Which dosage of Sugammadex is appropriate for a patient with TOF 2/4?
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Neostigmine should be administered at a dose of 0.16-0.2 mg/mg of Glycopyrrolate.
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What are the common causes of hypoxemia in the PACU?
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The most common causes of respiratory complications in the PACU are atelectasis and _____ hypoventilation.
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Match the neuromuscular blockers to their reversal agent:
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What is a recommended method to monitor upper airway obstruction in the PACU?
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Postoperative hypoventilation can be caused by inadequate analgesia.
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If Succinylcholine is used, the recommended management is supportive care, including _____ and jaw thrust.
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Study Notes
Anesthesia and CO2 Response
- Anesthesia drugs shift the CO2 response curve to the right, resulting in decreased alveolar ventilation for increased PaCO2.
- Higher CO2 levels are necessary to trigger increased respiratory rate (RR) and tidal volume.
- Individual variability exists; a certain CO2 threshold leads to sedation for each person.
- Shifting the curve to the right raises apnea threshold, requiring significant CO2 accumulation for respiratory drive activation, risking CO2 narcosis.
Management of Arterial Hypoxemia in PACU
- Supplemental oxygen or normalizing PaCO2 can reverse arterial hypoxemia caused by hypercapnia.
- If hypercapnia results from over-sedation, reversal agents (e.g., Naloxone, Flumazenil) may be administered carefully to preserve analgesic effects.
- Inadequate analgesia can be addressed with additional pain medication to improve respiratory effort.
- Neuromuscular blockade inadequacy requires Sugammadex or Neostigmine/Glycopyrrolate for reversal.
- Neurologic injuries call for an immediate neuro consult and airway protection via intubation.
- In COPD cases, non-invasive ventilation techniques (mask, NC, CPAP) are essential.
- Bronchospasm management includes administration of 100% oxygen, Epinephrine, Albuterol/Ipratropium, and possibly Hydrocortisone.
Neuromuscular Blockade Reversal
- Rocuronium or Vecuronium reversal involves Sugammadex: 2 mg/kg IV for TOF 2/4; 4 mg/kg IV for TOF 0/4 or 1-2 PTC.
- If Succinylcholine is used, supportive care is necessary, including chin lift and 100% FiO2.
- Atracurium or Cisatracurium reversal involves Neostigmine (0.05-0.07 mg/kg) and Glycopyrrolate (0.16-0.2 mg/mg of Neostigmine).
Airway Management Post-Surgery
- Upper airway obstruction post-thyroid or carotid surgery mandates decompression through clip/suture release and hematoma evacuation, with tracheostomy as an emergency option.
- Effective monitoring during OR to PACU transport includes vigilance for snoring, stridor, absent breath sounds, and maintaining watch over oxygen saturation.
Common Causes of Hypoxemia in PACU
- Causes include pulmonary embolism, obstructive sleep apnea (OSA), pneumothorax, pulmonary edema, atelectasis, upper airway obstruction, bronchospasm, aspiration, hypoventilation, and diffusion hypoxia.
- Most prevalent factors are atelectasis and alveolar hypoventilation.
Postoperative Hypoventilation Causes
- Hypoventilation can stem from reduced ventilatory drive, pulmonary/respiratory muscle deficiency, inadequate neuromuscular blockade reversal, poor analgesia, bronchospasm, or pneumothorax.
Normal Ventilatory Response to CO2
- Normally, elevated CO2 results in rapid, deep breathing to expel CO2.
- In the case of pneumothorax, immediate chest X-ray and possible chest tube insertion are critical if the patient is hemodynamically compromised.
Diffusion Hypoxia
- Occurs during nitrous oxide washout upon emergence from general anesthesia, leading to dilution of alveolar oxygen and hypoxemia.
- Administering high FiO2 can mitigate these hypoxic effects.
Hypoxic Pulmonary Vasoconstriction
- This mechanism diverts blood from poorly ventilated lung areas to enhance V/Q matching and minimize perfusion to under-ventilated regions.
- Inhaled anesthetics and nitroprusside inhibit hypoxic pulmonary vasoconstriction through vasodilation.
Coexisting Lung Diseases and Hypoxemia
- Conditions like emphysema, interstitial lung disease, primary pulmonary hypertension, and pulmonary fibrosis can reduce diffusion capacity, contributing to arterial hypoxemia post-surgery.
Pulmonary Edema Causes in PACU
- Cardiogenic pulmonary edema arises from volume overload or congestive heart failure (CHF).
- Noncardiogenic pulmonary edema may result from airway obstruction (post-obstructive pulmonary edema), sepsis, or transfusion reactions (TRALI).
Postobstructive Pulmonary Edema
- Defined as pulmonary edema secondary to airway obstruction, which can occur after surgical procedures.
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Description
This quiz explores the impact of anesthesia drugs on the CO2 response curve and how it affects alveolar ventilation and the body's response to increased PaCO2 levels. Understand the limits of respiratory response and the implications of sedation due to elevated CO2. Test your knowledge on these critical concepts in anesthesiology.