A patient with a non-ST segment elevation myocardial infarction (NSTEMI) is receiving heparin.
What is the purpose of the heparin?

Choice A rationale

The patient is manifesting classic signs of the progressive stage of hypovolemic shock due to severe dehydration from vomiting, diarrhea, and osmotic diuresis. A blood pressure of 72/62 indicates a profound drop in mean arterial pressure, leading to compensatory failure. The body shunts blood to vital organs, causing peripheral cyanosis and cold, clammy skin. Lethargy and disorientation signify decreased cerebral perfusion. Normal blood glucose is 70 to 99 mg/dL; 748 mg/dL is extremely high, causing massive fluid shifts.

Choice B rationale

Cardiogenic shock results from primary cardiac pump failure, often following a myocardial infarction. While this patient has a rapid, irregular, and thready pulse of 128, the primary etiology here is fluid loss from gastrointestinal distress and hyperglycemia rather than intrinsic heart muscle damage. In the refractory stage, multi-organ failure is irreversible and death is imminent. This patient still has a measurable urinary output of 120 ml, suggesting they are in the progressive rather than the final terminal stage.

Choice C rationale

Septic shock is characterized by a systemic inflammatory response to infection, typically presenting with a high fever or hypothermia and vasodilation in early stages. This patient has a temperature of 97 degrees F, which is slightly low but not necessarily indicative of sepsis. The primary history involves fluid loss and extreme hyperglycemia. Septic shock usually involves a decrease in systemic vascular resistance, whereas this patient's cold, clammy skin and cyanosis suggest high systemic vascular resistance as a compensation for low volume.

Choice D rationale

The compensatory stage of shock involves the activation of the sympathetic nervous system to maintain cardiac output and blood pressure. In that stage, the blood pressure usually remains within normal limits or is only slightly decreased. A blood pressure of 72/62 indicates that compensatory mechanisms have failed. Furthermore, "diabetic shock" is not a standard clinical classification for shock stages; rather, the patient is likely in a Hyperglycemic Hyperosmolar State causing hypovolemia, which has progressed beyond compensation.

Choice A rationale

In assist/control mode, every breath—whether initiated by the machine or the patient—is delivered at the full set tidal volume of 800 mL. If the patient is tachypneic at 22 breaths/min, they are receiving 22 high-volume breaths per minute. This excessive ventilation flushes out too much carbon dioxide from the blood. Since CO2 is an acid, a decrease in arterial CO2 (PaCO2 < 35 mmHg) leads to an increase in blood pH, resulting in respiratory alkalosis.

Choice B rationale

Metabolic acidosis is characterized by a low pH ( < 7.35) and a low bicarbonate level ( < 22 mEq/L). It is typically caused by the accumulation of metabolic acids, such as lactic acid or ketones, or the loss of bicarbonate through the kidneys or GI tract. Tachypnea on a ventilator in assist/control mode specifically affects the respiratory component of the acid-base balance by removing CO2, which does not directly cause a primary metabolic acid-base disturbance.

Choice C rationale

Respiratory acidosis occurs when there is alveolar hypoventilation leading to the retention of carbon dioxide (PaCO2 > 45 mmHg) and a decrease in pH. This would happen if the ventilator settings were too low or if the patient had significant dead space ventilation. In this scenario, the patient is over-ventilating by breathing 22 times per minute at a large tidal volume, which prevents the accumulation of CO2 and therefore makes respiratory acidosis impossible in this context.

Choice D rationale

Metabolic alkalosis involves a high pH (> 7.45) and an elevated bicarbonate level (> 26 mEq/L). This is usually caused by the loss of hydrogen ions through gastric suctioning or vomiting, or the excessive intake of bicarbonate. While the patient in the scenario will likely have an elevated pH, it is driven by the rapid respiratory removal of carbon dioxide rather than a metabolic shift in bicarbonate levels or fixed acid loss from the body.