tommyk
04-09-2006, 12:21 AM
Hy 2109
A 35-year-old man named Matt Dillon has been admitted to the medical intensive care unit in ACUTE respiratory distress. An endotracheal tube is placed for mechanical
ventilation at a tidal volume of 900 mL, a rate of 12 breaths/min, and a fraction of inspired oxygen of 50%. The positive end expiratory pressure is 10 cm.
Medications include subcutaneous heparin and aspirin. He now develops tachycardia and a blood pressure of 70/palpation mm Hg. Cardiac examination reveals multiple premature contractions. His arterial blood gas reveals a PO2 of 40 mm Hg. Which of the following is the most likely cause of this condition? (Hint: Think acute vs. chronic and the age of the patient. Think slowly and methodically. And do NOT RUSH TO THE ANSWER. Think first please because this is HARD USMLE type question!
1-Cardiac arrhymia
2-Bronchial secretions
3-MI
4-Pneumothorax
5-Pumonary embolus
6-Anxiety provoked heart rate increase on a movie set.
a) #4. The sudden onset of tachycardia and hypotension indicates an acute process. Since the patient is being mechanically ventilated with positive pressure, he is at increased risk of a bullous rupture from barotrauma, leading to a pneumothorax.
Cardiac arrhythmia could lead to tachycardia and hypotension, BUT ventricular tachycardia and atrial fibrillation with a rapid ventricular response may cause this from decreased ventricular filling. An ECG would aid in this diagnosis. In the setting of mechanical ventilation, however, a pneumothorax must be excluded first.
Bronchial secretions usually have a progressively worsening presentation. Furthermore, the patient would exhibit desaturation, but not necessarily hypotension.
Myocardial infarction may lead to cardiogenic shock from failure. However, this would most likely be a bit more progressive and less acute. Infarction must remain high on the differential diagnosis, and the patient may require vasopressors because of the shock. In the immediate setting, the pneumothorax is more likely, given the acuity of onset.
Pulmonary embolus is on the differential diagnosis of electromechanical dissociation. This patient's risk of an embolus is increased because of prolonged immobilization. However, the subcutaneous heparin should be adequate prophylaxis against an embolism.
A 35-year-old man named Matt Dillon has been admitted to the medical intensive care unit in ACUTE respiratory distress. An endotracheal tube is placed for mechanical
ventilation at a tidal volume of 900 mL, a rate of 12 breaths/min, and a fraction of inspired oxygen of 50%. The positive end expiratory pressure is 10 cm.
Medications include subcutaneous heparin and aspirin. He now develops tachycardia and a blood pressure of 70/palpation mm Hg. Cardiac examination reveals multiple premature contractions. His arterial blood gas reveals a PO2 of 40 mm Hg. Which of the following is the most likely cause of this condition? (Hint: Think acute vs. chronic and the age of the patient. Think slowly and methodically. And do NOT RUSH TO THE ANSWER. Think first please because this is HARD USMLE type question!
1-Cardiac arrhymia
2-Bronchial secretions
3-MI
4-Pneumothorax
5-Pumonary embolus
6-Anxiety provoked heart rate increase on a movie set.
a) #4. The sudden onset of tachycardia and hypotension indicates an acute process. Since the patient is being mechanically ventilated with positive pressure, he is at increased risk of a bullous rupture from barotrauma, leading to a pneumothorax.
Cardiac arrhythmia could lead to tachycardia and hypotension, BUT ventricular tachycardia and atrial fibrillation with a rapid ventricular response may cause this from decreased ventricular filling. An ECG would aid in this diagnosis. In the setting of mechanical ventilation, however, a pneumothorax must be excluded first.
Bronchial secretions usually have a progressively worsening presentation. Furthermore, the patient would exhibit desaturation, but not necessarily hypotension.
Myocardial infarction may lead to cardiogenic shock from failure. However, this would most likely be a bit more progressive and less acute. Infarction must remain high on the differential diagnosis, and the patient may require vasopressors because of the shock. In the immediate setting, the pneumothorax is more likely, given the acuity of onset.
Pulmonary embolus is on the differential diagnosis of electromechanical dissociation. This patient's risk of an embolus is increased because of prolonged immobilization. However, the subcutaneous heparin should be adequate prophylaxis against an embolism.