CardiologyClinical TopicsCritical CareUncategorized

Stemming a lethal immunologic response

By: Polly Gerber Zimmermann

AFTER EXPERIENCING VOMITING and diarrhea for the past day, Katherine Astley, age 52, visits her primary care provider. The physician finds the patient’s vital signs stable and sends her home with instructions to drink plenty of clear liquids. But 12 hours later, Mrs. Astley is brought to the emergency department (ED) by her husband, who reports she has been unable to tolerate the fluids.

Assessment hints

In the ED, Mrs. Astley tells the nurse she’s thirsty and dizzy. Her vital signs are temperature 100.4° F (38° C), blood pressure (BP) 98/60 mm Hg, heart rate (HR) 120 beats/minute (bpm), and respiratory rate (RR) 18 breaths/minute when lying down. In a standing position, her BP is 77/53 mm Hg, HR is 118 bpm, and RR is 18 breaths/minute. Her oxygen saturation (O2 sat) is 92% on room air. The nurse notes that Mrs. Astley’s tongue is furrowed.

Recognizing these as signs of significant dehydration, the nurse obtains I.V. access and, as ordered, gives an initial bolus of 300 mL normal saline solution. The patient’s vital signs remain unchanged. The nurse continues giving I.V. fluids at 150 mL/hour while awaiting blood test results. The physician admits Mrs. Astley for 23-hour observation with a diagnosis of dehydration.

On the scene

On arrival at your inpatient unit, Mrs. Astley’s vital signs are BP 94/52 mm Hg, HR 104 bpm, and RR 22 breaths/minute. Her O2 sat is still 92% on room air. Blood tests show a white blood cell (WBC) count of 16,300/mm3, neutrophils 97%, platelets 59,000/mm3, blood urea nitrogen (BUN) 48 mg/dL, and creatinine 2.1 mg/dL.

You know elevated WBC and neutrophil counts are classic indicators of acute infection, her unexpectedly decreased platelet count indicates thrombocytopenia, and her elevated BUN and creatinine levels signify decreased renal function. What’s more, Mrs. Astley’s hypotension
persists even though she has received 1 L of fluid. You call the hospitalist to report the results.

The hospitalist says the patient has systemic inflammatory response syndrome (SIRS) with sepsis. He orders early, empiric therapy of rapid I.V. antibiotic administration and aggressive I.V. fluid resuscitation. As ordered, you insert an indwelling catheter to monitor urine output and give repeat fluid boluses over 20 minutes until Mrs. Astley’s urine output measures 0.5 mL/kg/hour. After two blood cultures are obtained, a broad-spectrum antibiotic infusion is started. Mrs. Astley is transferred to the ICU for more intensive care and central hemodynamic monitoring.


Over the next few days, Mrs. Astley’s condition stabilizes. Her vital signs are HR 90 bpm, BP 120/70 mm Hg, and RR 18. Also, her WBC count decreases.

Education and follow-up

In SIRS, the immune system overreacts to an infection. This leads to increased microvascular clotting and reduced ability to break down clots, in turn causing widespread microvascular perfusion deficits and global hypoxia. Hypoxia occurs at the cellular level even if O2 sat is normal.

Thrombocytopenia sometimes accompanies SIRS. SIRS is diagnosed in patients with two or more of the following criteria:

  • temperature below 98.1° F (36.7° C) or above 100.4° F (38° C)
  • HR above 90 bpm
  • RR above 20 breaths/minute or partial pressure of arterial carbon dioxide below 32 mm Hg
  • WBC count below 4,000/mm3 or above 12,000/mm3, or more than 10% bands (immature neutrophils).

Sepsis is SIRS with a coexisting infection (either suspected or proven). For a patient with SIRS with or without sepsis, treatment must begin within the first 6 hours.

SIRS can have a vague presentation. Fortunately, your critical-thinking skills and knowledge of SIRS criteria allowed you to recognize that Mrs. Astley’s life was in danger, and your quick action led to prompt interventions.

Polly Gerber Zimmermann is Associate Professor of Nursing at Truman College in Chicago, Illinois.

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