Fluids, Electrolytes, Acid-Base Disorders, and Nutrition Support

Answer: C

An ileus, usually detected on radiologic examination of

the lower abdomen, indicates lack of motility and pres-

ence of distention and air within the small bowel. This

is usually depicted as “dilated loops of bowel.” Patients

cannot be fed safely or efficaciously by the enteral

route during an ileus (Answer C is correct). Answer A

is incorrect because a feeding tube can be placed for

enteral feeding of the patient with anorexia, and PN is

not indicated. Answer B is incorrect because presence

or absence of bowel sounds is not an accurate marker for

assessing bowel function. Answer D is incorrect because

a high gastric residual volume during enteral feeding,

combined with abdominal distension, bloating, emesis,

or regurgitation, can often be efficaciously treated with

prokinetic pharmacotherapy or advancement of the

feeding tube into the small bowel with resumption of

enteral feeding. In addition, the guidelines recommend

against discontinuing EN for a GRV less than 500 mL in

the absence of other signs of intolerance.

Answer B, 0.45% sodium chloride and potassium chlo-

ride 20 mEq/L, is correct given the average electrolyte

composition of gastric fluid (see Table 4 regarding the

electrolyte composition of GI fluids). Answers A, C,

and D are incorrect because they do not as accurately

replace the electrolyte content that is lost from gastric

fluid output.

Answer: A

With significant diarrhea, intravenous zinc requirements

from GI fluid losses during critical illness increase from

the normal requirements of 3–5 mg/day. Data analyses

show that most patients with increased intestinal losses

can achieve a positive zinc balance on 13 mg of intra-

venous zinc daily (Gastroenterology 1979;76:458-67).

As a result, most clinicians provide additional zinc sup-

plementation for patients with short bowel syndrome,

intestinal fistulas, or prolonged and sustained diarrhea

(Answer A is correct). Answer B is incorrect because

copper is an extremely rare and unlikely deficiency to

occur during parenteral nutrition therapy. Answers C

and D are incorrect because intractable diarrhea losses

are less likely to cause a deficiency, albeit with the

exception of copper (especially with extreme intestinal

bypass procedures for obesity).

Answer: C

Given the severity of the patient’s condition (recent sei-

zure from severe hyponatremia) and likely diagnosis

of SIADH, the immediate goal should be to achieve a

serum sodium concentration of greater than 120 mEq/L

by short-term infusion of 3% sodium chloride (Answer

C is correct). Conivaptan (Answer D) could then be

given to correct the hyponatremia, limiting the increase

in serum sodium concentration to less than 10–12

mEq/L/day. Fluid restriction is imperative and is the

primary overall management technique for this patient.

Answer A is incorrect because a more rapid response is

imperative because of the patient’s seizure and severity

of the condition. Answer B is incorrect because it would

be a potentially life-threatening error by providing more

ADH-like substance and because it is used to treat dia-

betes insipidus (the opposite condition of SIADH).

Answer: B

Studies show that increases in mesenteric potassium

concentrations detected by potassium sensors in the

splanchnic vascular bed evoke increased renal potas-

sium excretion (feed-forward regulation of potassium

homeostasis), even before regulation by aldosterone

(classic feedback regulation) (Answer B is correct).

The bioavailability of enteral potassium is 95%–100%

in the absence of aberrations in GI motility, function,

or anatomy. A primary difference between enteral and

parenteral potassium is that the rate of absorption is

slower with enteral potassium (Answer A is incorrect).

Intravenous potassium administration can inadvertently

be infused too quickly (it is acceptable to infuse potas-

sium at 10 mEq/hour for patients without a cardiac

monitor and up to 20 mEq/hour for those with a moni-

tor). Answer C is incorrect because potassium chloride

elixir or solution is an effective means for providing

potassium when given intra-gastrically. It generally only

causes diarrhea when given in higher doses or when

administered directly into the small bowel through a

feeding jejunostomy because it is a hypertonic solution.

Answer D is a nonsensible answer.