Shock Syndromes I

Answer: C

This older adult patient presents with septic shock.

Shock is a syndrome of impaired Do2, leading to tissue

injury and end-organ failure. In this case, it is important

to realize that fever is a symptom of an inflammatory

syndrome, not a shock syndrome (Answers A, B, and

D are incorrect). This patient’s presentation with hypo-

tension, confusion, and hyperlactatemia suggests the

presence of a shock syndrome in the setting of impaired

Do2 (Answer C is correct).

The Fick equation for Do2 best shows Do2. According

to this equation, Do2 depends on CO and Cao2. Cardiac

output depends on heart rate and SV. Typically, an ele-

vated heart rate will increase CO and Do2. However,

if a patient has atrial fibrillation, ventricular filling is

impaired and SV is decreased, causing a decrease in CO

and Do2 (Answer B is correct). Lactate does not impede

Do2 but is a byproduct of impaired Do2 (Answer A is

incorrect). Similarly, Do2 is not impaired by acute kid-

ney injury (Answer C is incorrect). Finally, fever is an

inflammatory response that increases Vo2 but does not

impair Do2 (Answer D is incorrect).

Answer: D

The patient’s laboratory values and arterial pH are

consistent with hyperchloremic metabolic acidosis,

and chloride-rich fluids should be avoided. Lactated

Ringer’s solution is considered a relatively chloride-

poor solution (chloride content 111 mEq/L) and is best

in this case (Answer D is correct). With its chloride

content of 154 mEq/L, 0.9% sodium chloride is consid-

ered a chloride-rich fluid. Liberal use of chloride-rich

fluids such as 0.9% sodium chloride has been associated

with an increased need for renal replacement therapy

(Answer A is incorrect). Although albumin 5% is con-

sidered a chloride-poor solution, data from randomized

controlled trials have not supported a mortality ben-

efit with albumin over crystalloids, even in the setting

of hypoalbuminemia. Moreover, the patient has not

received a “substantial volume” of crystalloids (she has

received less than 30 mL/kg of fluid) that would coin-

cide with recommendations to give albumin (Answer

B is incorrect). Hydroxyethyl starch solutions may also

have a high chloride content (depending on the formula-

tion) and have been associated with an increased need

for renal replacement therapy in the general critical care

population, with no mortality benefit. Hydroxyethyl

starch solutions should be avoided for fluid resuscitation

in the ICU (Answer C is incorrect).

Answer: B

The patient has evidence of end-organ hypoperfusion

(urinary output less than 0.5 mL/kg/hour and elevated

lactate concentration without significant clearance),

despite a MAP greater than 65 mm Hg and quantita-

tive resuscitation. The patient probably needs a higher

perfusion pressure because of a right-shifted zone of

autoregulation secondary to hypertension. The norepi-

nephrine dose should be increased to target a higher

MAP; the exact target will depend on the patient’s

response and should be selected as the threshold that

improves end-organ perfusion (Answer B is correct).

The patient has no evidence of impaired CO (his Scvo2 is

not low); therefore, fluids (to improve SV) and inotropes

(e.g., dobutamine) are not indicated (Answers C and D are

incorrect). Because the patient has continued evidence of

hypoperfusion, action should be taken, and the current

therapy should be modified (Answer A is incorrect).

Answer: B

The patient has hypotension and signs of hypoperfusion

with an elevated lactate concentration; possible inter-

ventions such as fluid administration should be explored

further. Because the patient requires a high Fio2, a reli-

able predictor of fluid responsiveness should be used to

guide fluid therapy instead of administering fluid with-

out respect to predicting responsiveness. In the setting

of atrial fibrillation, an elevated PPV is not a reliable

predictor of fluid responsiveness, and further evaluation

should be done before fluids are administered (Answer

A is incorrect). A PLR test can be used in both spontane-

ously breathing patients and those receiving mechanical

ventilation to predict fluid responsiveness, and the patient

has a method to assess the presence (or absence) of a CO

response (Answer B is correct). Although the accuracy

of the CO value from arterial pulse pressure waveform

analysis may be somewhat limited by atrial fibrillation,

this may be accounted for with the internal software of

most devices and can be used to gauge a response to

the PLR test. The patient has a femoral central venous

catheter, which cannot be used to assess hemodynamic

markers such as CVP or Scvo2 (Answers C and D are

incorrect). Furthermore, CVP is an inadequate predictor

of fluid responsiveness.