A 62-year-old woman is evaluated on postoperative day 1 following an open total abdominal … — USMLE Step 2 CK

A 62-year-old woman is evaluated on postoperative day 1 following an open total abdominal hysterectomy for symptomatic uterine fibroids. Over the last $6$ hours, her recorded urine output has been a total of $70\text{ mL}$ . Her temperature is $37.9^\circ\text{C}$ ( $100.2^\circ\text{F}$ ), blood pressure is $100/65\text{ mmHg}$ , pulse is $98\text{/min}$ , and respiratory rate is $16\text{/min}$ . Her oxygen saturation is $98\%$ on room air. She has been receiving maintenance intravenous normal saline at $75\text{ mL/hr}$ . Physical examination reveals dry oral mucosa and a soft abdomen with mild incisional tenderness. Breath sounds are clear bilaterally. A Foley catheter is in place. Which of the following are appropriate initial actions in the management of this patient? (Select all that apply)

Administer a rapid intravenous bolus of isotonic crystalloidAnswer
Flush the Foley catheter with sterile salineAnswer
C
Administer intravenous furosemide
D
Order blood cultures and a chest radiograph
E
Administer empiric broad-spectrum intravenous antibiotics

Answer

The appropriate initial actions are to administer a rapid intravenous bolus of isotonic crystalloid and flush the Foley catheter with sterile saline.

The correct combination of actions addresses the two most common and easily reversible causes of postoperative oliguria. Flushing the Foley catheter ensures that there is no mechanical obstruction preventing urine from draining. Simultaneously, administering an isotonic fluid bolus addresses prerenal azotemia caused by hypovolemia, which is strongly suggested by the patient's dry oral mucosa, low-normal blood pressure, and low rate of maintenance fluid infusion.

Step-by-Step Solution

Calculate the expected minimum urine output to confirm oliguria.

Oliguria is defined as

<0.5\text{ mL/kg/hr}

. For a

75\text{ kg}

woman (estimated weight to match the presentation), this would be

37.5\text{ mL/hr}

. Producing only

70\text{ mL}

over

6

hours (

~11.6\text{ mL/hr}

) confirms severe oliguria.

Recognizing the severity of the decreased urine output is necessary to guide clinical urgency.

Evaluate for post-renal (obstructive) causes.

The patient has a Foley catheter, which can become blocked by debris, clots, or kinking.

Flushing the catheter is a rapid bedside procedure to immediately rule out mechanical obstruction before pursuing systemic interventions.

Assess the patient's intravascular volume status to rule in pre-renal causes.

The patient has borderline hypotension (

100/65\text{ mmHg}

), a high-normal heart rate (

98\text{/min}

), and dry mucous membranes, which point to hypovolemia. The low maintenance fluid rate (

75\text{ mL/hr}

) further supports under-resuscitation.

Intravascular volume depletion is the most common cause of early postoperative oliguria, and a fluid challenge with isotonic crystalloid helps restore renal perfusion.

Key Concept

The initial management of postoperative oliguria includes ruling out mechanical catheter obstruction and evaluating volume status, followed by an isotonic fluid bolus if hypovolemia is suspected. Low-grade fever on postoperative day 1 is physiologic and does not warrant an infectious workup.

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