Correct Answer: C

Rationale: A serum bicarbonate level of 18 mEq/L is most concerning in a client with COPD as it indicates metabolic acidosis, requiring immediate intervention. In COPD, patients often retain carbon dioxide, leading to respiratory acidosis. A low serum bicarbonate level suggests that the body is compensating for this respiratory acidosis by increasing bicarbonate levels to maintain balance. Therefore, a low serum bicarbonate level in this scenario is alarming. Choices A, B, and D are within normal ranges and not directly related to the acid-base imbalance seen in COPD.

Correct Answer: C

Rationale: The correct answer is C: Troponin level. Troponin levels should be closely monitored in a client with chest pain and a history of myocardial infarction to assess for ongoing myocardial injury. Troponin is a specific marker for myocardial damage. Monitoring white blood cell count (choice A) is not directly related to myocardial infarction. Serum creatinine (choice B) is more indicative of renal function rather than cardiac status. Hemoglobin level (choice D) is important but does not directly reflect ongoing myocardial injury.

Correct Answer: C

Rationale: The correct action for the nurse to take first is to inform the anesthesia care provider. The patient's ingestion of coffee violates the NPO (nothing by mouth) guidelines before surgery, which increases the risk of aspiration during anesthesia. Informing the anesthesia care provider promptly allows for appropriate assessment and decision-making regarding the patient's anesthesia plan. Ensuring preoperative lab results, starting an IV, or contacting the obstetrician can be important steps but addressing the NPO violation and its implications on anesthesia safety take precedence.

Correct Answer: D

Rationale: The correct answer is D. A prothrombin time of 18 seconds is most concerning in a client with hepatic encephalopathy as it indicates impaired liver function and an increased risk of bleeding. This requires immediate intervention to prevent bleeding complications. Choice A, serum ammonia level of 80 mcg/dl, is elevated but not as urgent as the abnormal prothrombin time. Choice B, bilirubin level of 3.0 mg/dl, is elevated but does not directly indicate an urgent need for intervention in this situation. Choice C, serum sodium level of 135 mEq/L, is within the normal range and does not require immediate intervention.

Correct Answer: C

Rationale: The correct answer is C: 'Use of accessory muscles.' In a client with COPD and pneumonia, the use of accessory muscles indicates increased work of breathing. This finding is concerning as it may signal respiratory failure, requiring immediate intervention. Oxygen saturation of 90% (choice A) is low but not as immediately concerning as the increased work of breathing. A respiratory rate of 24 breaths per minute (choice B) is slightly elevated but not as critical as the use of accessory muscles. Inspiratory crackles (choice D) may be present in pneumonia but are not as indicative of impending respiratory failure as the increased work of breathing shown by the use of accessory muscles.