Submitted by Beth Stroud, RN, BSN, Graduate Student Murray State University


Acute renal failure (ARF) has become increasingly common in patients with critical illnesses. Up to two-thirds of intensive care unit (ICU) patients develop ARF with the leading cause being sepsis (Kosinski, 2009). Treatment of ARF has been associated with higher costs and the following adverse outcomes: increased length of stay, excess mortality of 30-71%, need for chronic dialysis in the patients who survive, and the requirement of discharge to short-term or long-term care facilities (Uchino, Kellum, Bellomo, Doig, Morimatsu, Schetz, Tan, Bouman, Macedo, Gibney, Tolwani, & Ronco, 2005). Despite the prevalence of the disease and the need for evidence-based guidelines, over 57 different definitions exist for the critical condition.
Early recognition of ARF has been instrumental in improving patient outcomes. Interdisciplinary collaboration is essential for prompt identification of risks and for completing accurate ongoing assessments. Treatment of ARF includes multiple pharmacological and non-pharmacological components such as mechanical ventilation, vasoactive intravenous medications, nutritional support, and dialysis.
Based on the complexity of ARF, healthcare institutions are challenged with the need to provide complex care to obtain optimal patient outcomes. The American Association of Critical Care Nurses’ (AACN) Synergy Model provides a framework for institutions to correlate the patients’ characteristics and care needs with the nurses’ competencies in order to achieve optimal outcomes (Kaplow & Hardin, 2007). The purpose of this article is to demonstrate the use of the Synergy Model in obtaining optimal patient outcomes in the following case study.
Case Study: Acute Renal Failure and Sepsis
John is a 43 year old, white male who is single, has no children, is unemployed, and is  uninsured. He has been treated for hypertension and erectile dysfunction for the past 3 years and  has presented to the emergency department four times in the last month with complaints of not being able to urinate. His home medications include Aspirin 81 mg daily, Plavix 75 mg daily, Metoprolol 50 mg twice a day, and Viagra as needed; however, he has only been taking his Viagra since he lost his job three months ago. He has developed urinary retention and has been catheterizing himself at home for approximately one week with the foley catheter he pulled out of the trash at his last emergency room visit.
His older sister, the only surviving relative, has brought him to the emergency department with confusion, hypothermia, tachycardia, tachypnea, hypotension, neutropenia, bandemia, anemia, and thrombocytopenia. His admitting blood urea nitrogen (BUN) and creatinine were 65 and 7.5 mg/dl, respectively. His urinalysis revealed white blood cells (WBC) too numerous to count and trace of red blood cells (RBC). His potassium level was 5.8. Blood cultures revealed a gram-negative septicemia.
After being admitted and transferred to the ICU, John had a rapid decline in respiratory status and was intubated and mechanically ventilated. Fluid replacement was started using crystalloid solutions. Norepinephrine was started IV to manage the hypotension and maintain an adequate blood pressure. An infectious disease practitioner was consulted and John was started on aggressive antibiotic, antifungal, and antiviral therapy. The nephrologist ordered continuous renal replacement therapy (CRRT) to treat John’s ARF since he was too unstable to tolerate hemodialysis.
AACN Synergy Model
The American Association of Critical Care Nurses’ (AACN) Synergy Model for Patient Care is a conceptual framework used to guide nursing practice. The Synergy Model places the patient as the central focus and suggests matching the competencies and skills of the nurse to the patient’s care needs. The model identifies eight patient characteristics and eight nursing competencies and describes the relationship to outcomes for the patient, nurse, and the healthcare system. The Synergy Model is particularly important in critical care areas which require nurses to have greater competencies and skill sets to meet the needs of the critically ill patients such as John.

Patient Characteristics
The Synergy Model’s eight characteristics help nurses identify patient needs across the continuum of health to illness and are as follows: resiliency, vulnerability, stability, complexity, resource availability, participation in care, participation in decision making, and predictability.
Understanding these characteristics as they change with the patient’s condition helps determine the competencies essential to deliver optimal care. John’s patient characteristics are outlined in the following table:
Stability (decreasing)
Hypothermia, hypotension, tachycardia, tachypnea, confusion
Complexity (increasing)
Two or more body systems entangled, systemic infection, respiratory compromise
Predictability (uncertain)
Instability and uncertainty in the patient’s life Resiliency
Very rapid decline with sepsis, unresponsive 30 minutes upon arrival to ICU Vulnerability
Little if no financial reserve from loss of job and limited resources
Participation in decision making and care (absent shortly after admission)
Confusion and cognitive impairment from advanced sepsis. Sister was very emotional and apologetic. She was not “close” to the patient in general as she identified in the history
Resource availability
Limited financial resources.
No assistance possible from family
Unknown available community resources.
John was experiencing a decrease in stability and resiliency based on the sepsis, renal failure, respiratory failure, and rapid physical decline. His complexity and vulnerability as a patient was drastically increasing because of the disease process as well as the lack of resource availability. The predictability is not certain as well as his willingness to participate in care.
The nursing characteristics and competencies of the Synergy Model will be addressed as it relates to patient outcomes. Understanding and applying the Synergy Model to John’s patient characteristics first requires knowledge of the pathophysiology and treatment modalities for ARF
and sepsis.
Pathophysiology of acute renal failure
According to Kosinski (2009), acute renal failure is “a sudden decline in both glomerular and tubular function, resulting in the failure of the kidneys to excrete nitrogen and waste products with a corresponding failure to maintain fluid, electrolyte and acid-base balance” (p.4).
ARF may be associated with decreased urinary output of less than 30 ml/h. Prerenal failure may not result in kidney damage with early identification and prompt treatment. The focus of this discussion will be on prerenal caused by the alteration in renal systemic vascular resistance ratio as a result of sepsis.
The normal functions of the kidneys are to filter and excrete wastes and toxins by regulating fluids, electrolytes, and acid-base balance. The kidneys receive 20% to 25% of cardiac output and the amount of blood that flows through the renal arterioles depends on renal blood flow. Any alteration in the renal blood flow alters the glomelular filtration rate (GFR) (Broden, 2009).
The chemical and humoral mediators released during sepsis contribute to a pro-inflammatory response and systemic vasodilation. The resulting decrease systemic pressure stimulates the sympathetic nervous system, leading to renal artery constriction and a decrease in both filtration and excretion.
Systems Assessment
Impairment of renal function affects multiple body systems, making the care needs of ARF complex and challenging. Ongoing comprehensive assessments are critical; the caregiver must be attentive to the signs and symptoms of renal disease as well as complications with other organs and systems. The complexity of ARF demonstrates the need for correlating patient characteristics and nursing competencies in the Synergy Model to obtain optimal outcomes.
The primary effect of ARF is a decrease in urinary output that leads to fluid retention and edema. Oliguria is the classic sign with an output of less than 400 ml in 24 hours. The decrease in filtration leads to BUN and creatinine build up in the blood as the kidney loses its ability to remove waste products. Other lab results that may be abnormal include metabolic acidosis, hyperkalemia, hyponatremia, hyperphosphatemia, hypocalcemia, and hypermagnesemia.

In general, the fluid volume overload experienced in ARF may lead to hypertension, pulmonary edema, peripheral edema, and arrhythmias. The kidneys fail to excrete excess potassium which may lead to the following: muscle weakness, neuromuscular irritability, bradycardia, heart block, asystole, or other arrhythmias (Campbell, 2003).



Dyspnea may result from the decrease in oxygenation either from associated anemia or from fluid volume overload and pulmonary edema associated with ARF. The dyspnea may be at rest or worsen with exertion. Auscultation of lung field may reveal crackles.
ARF patients are anemic secondary to the impaired RBC production, hemolysis, bleeding, hemodilution, and decrease RBC survival. Damaged kidneys produce less erythropoietin to stimulate RBC production and the damaged red blood cells are not replaced. The decrease in hemoglobin leads to insufficient oxygenation manifested by dyspnea.
Uremia may cause nausea, vomiting, anorexia, gastric ulcers and colitis which places the patient at risk for GI bleeding. The increase in urea may also cause the patient’s breath to smell like foul urine.
Exceptions for John’s case study
John exhibited the majority of the above symptoms; however, he did not experience hypertension, pulmonary edema, peripheral edema, and arrhythmias common to ARF due to the vasodilation effect of the sepsis. Conversely, he was hypotensive and required volume replacement and intraveneous vasopressors. His blood gases revealed metabolic acidosis,
resulting from the lactic acid produced from the sepsis.
Diagnostic Tools
Conventional Biomarkers
The conventional methods of diagnosing ARF are urine output, creatinine, and urea. However, the presence or absence of urine does not necessarily denote renal malfunction. The output is more indicative of renal hemodynamics than actual renal function. The excretion of sodium and urea has not been proven to be sensitive in early ARF because the tubular functions may remain intact unless clinical conditions such as sepsis alter tubular function. Urine protein is present in other diseases such as diabetes, shock, and chronic kidney disease (Kosinski, 2009).
New Biomarkers
Acute renal failure can be diagnosed earlier utilizing the following biomarkers in addition to the conventional markers listed above: Cystatin C, Interlukin 18 (IL 18), Neutrophil Gelatinas-Associated Lipocalin (NGAL), and Kidney injury Molecule (KIM-1). Cystatin C is a marker of the glomelular filtration rate and is independent of age, sex, and muscle mass. Cystatin C has a small molecular mass and can be filtered more freely at the glomerulus. Interlukin 18 is an inflammatory cytokine which enters urine in the proximal tubule. NGAL propagates with injured endothelium of the lungs, stomach, colon, and kidneys and rises with acute infections. Kidney injury molecule (KIM-1) is a transmembrane protein that is excreted in the proximal tubule and detected in ischemic kidney disease. Cystatin C and NGAL are measured in the serum. IL-18, KIM-1, and NGAL are measured in the urine.
Diagnostic Imaging
Diagnostic imaging may also be needed in determining the underlying disease and differentiating between acute and chronic disease. The following may be utilized as diagnostic procedures: X rays, computed tomography scan (CT), magnetic resonance imaging (MRI), ultrasound, arteriogram, and renal biopsy. Ultrasounds of x rays of the ureters and bladder may also be included.
Rifle Criteria
The RIFLE criteria (Thurman, 2009) is evidence-based practice tool used for the diagnosis of ARF. The diagnosis of ARF can be the result of changes in the serum creatinine level, a change in the urinary output, or both. The RIFLE tool assesses the following: risk of renal dysfunction, injury to the kidney, failure of kidney function, loss of kidney function and end-stage kidney disease.

Treatment Modalities and Best Practice
The ultimate goals for treating ARF caused by sepsis are to eliminate the cause and to support the patient’s renal function. The primary focus in treatment of prerenal disease is restoring the blood flow with adequate pressure to the kidney. However, some of the treatments such as mechanical ventilation bring about further complications for the renal system, requiring greater need for the following supportive measure: maintaining fluid and electrolyte balance, removing nitrogenous wastes, sustaining nutrition, and providing emotional support and teaching to the patient and his family.
Mechanical Ventilation
Renal blood flow (RBF) is decreased as a result of permissive hypercapnea, hypoxemia and positive end-expiratory pressure (PEEP) associated with the use of mechanical ventilation. Decreased RBF caused by constriction in permissive hypercapnea results from both direct and indirect mechanisms. According to Broden (2009), the direct mechanism of hypercapnea is the stimulation of the sympathetic nervous system and release of norepinephrine, causing vasoconstriction and decrease in renal blood flow and GFR. The indirect mechanism is the effect of systemic vasodilatation and decrease vascular resistance, leading to further release of norepinephrine.
The use of lung-protective mechanical ventilation with optimal combination of lower tidal volumes and PEEP is currently standard of practice for preventing acute lung injury. The use of PEEP has not been directly linked to impairment of renal function. Healthcare providers need to recognize the stress of mechanical ventilation on the renal system and conduct frequent ongoing thorough assessments to identify potential complications.
Fluid replacement and vasoactive drugs
Vasoactive medications are frequently used to increase the mean arterial pressure and blood flow to the kidneys once the autoregulation of the kidneys is lost. Norepinephrine has been shown to be the most advantageous in patients with acute kidney injury and failure caused by sepsis (Kosinski, 2009). The norepinephrine increases the mean arterial pressure which, in turn, controls renal function and urine output. Norepinephrine has been shown to decrease renal blood flow in hypovolemic patients; therefore, it is critical to treat hypovolemia with crystalloid solutions prior to administration.
Acute renal failure can be treated by intermittent dialysis, peritoneal dialysis, or continuous renal replacement therapy (CRRT). The treatment modality is determined based on the patient’s diagnosis and condition. Many patients who are hemodynamically unstable do nottolerate intermittent dialysis as they often become hypotensive during treatment. Repeated episodes of hypotension may cause further injury and ischemia to the nephrons. Likewise, peritoneal dialysis is contraindicated in unstable patients because the pulmonary function may be compromised by the large volume of fluid instilled into the peritoneal cavity. CRRT is tolerated best in unstable, critically ill patients because it removes volume and solutes slowly, avoiding the rapid changes associated with hemodialysis. The goals of CRRT are to maintain optimal fluid balance and to correct electrolyte and metabolic abnormalities.
Frequent assessments are required for patients who are on CRRT. Vital signs need to be monitored for hypotension that may occur as a result of hypovolemia during therapy and for hypothermia that may occur as a result of the amount of blood that is in the tubing outside the body. Perfusion and hemodynamic status should be assessed by observing capillary refill, peripheral pulses, and skin temperature and color. The catheter site must be assessed for warmth, redness, edema, drainage, and tenderness. Accurate monitoring of the patient’s electrolyte levels, acid-base balance, and fluid balance are essential with CRRT. Hourly calculations must be performed to determine adjustments in fluid volumes.
Caring for CRRT patients requires knowledge of the CRRT system for troubleshooting alarms when they occur. For instance, if the patient is not receiving anticoagulant therapy and/or replacement fluids, the risk of clotting of the hemofilter is increased.
Critically ill patients often experience catabolism due to stress, further contributing to increased risks of ARF. The BUN and creatinine levels are increased as the body breaks down muscle for protein; however, nutrition should be low in protein and sodium and high in fats and carbohydrates to prevent the protein burden on the patient’s kidneys (Campbell, 2003). Fluids are generally restricted to the amount of the patient’s urine output plus 500 to 700 ml. Parental nutrition is recommended if the gastrointestinal tract is not functional.

Provision of emotional support and teaching
Acute renal failure is often very sudden and unexpected for both the patient and the family members. Thorough patient teaching about nutritional needs, fluid restrictions, medications, and the role of dialysis is essential in providing emotional support patients and family members.
Success story as it relates to the AACN synergy model
Nurse competencies
The complex care needs identified in John’s case exemplar should be correlated with the assigned nurse’s skill set and competencies according to AACN Synergy Model. The eight nursing competencies of the Synergy Model are as follows: clinical judgment, advocacy and moral agency, caring practice, collaboration, systems thinking, response to diversity, facilitator of learning, and clinical inquiry. Each competency is important in providing care; however, the competencies that take priority for John are clinical judgment, clinical inquiry, collaboration, and response to diversity.
The nurse would need strong clinical judgment to interpret and make decisions based on assessment findings that indicate John is in ARF caused by sepsis. John’s complex care requires his nurse to be clinically competent in assessment skills and additional skill sets for mechanical ventilation, pharmacology, and CRRT.
The clinical inquiry in John’s case incorporates ongoing questioning and evaluation of practice to direct John’s care through the use of evidence based guidelines. The use of Norepinephrine and CRRT are currently standard of practice for ARF.
Collaboration with multiple caregivers was also essential based on John’s complex needs for mechanical ventilation, IV vasopressor, and dialysis. John’s rapid decline and loss of consciousness warrants an advocate acting in his behalf to resolve both ethical and clinical concerns. Both response to diversity and caring practice are important due to the embarrassment of his erectile dysfunction, frequent partners, and use of Viagra.
The AACN Synergy Model measures nursing outcomes based on the dimensions of nursing practice. According to Kaplow and Hardin (2007), when the nursing competencies are properly assigned based on the patient characteristics, the expected outcomes should include “the extent to which care objectives are met, management of physiological changes, and the presence or absence of preventable complications” (p. 4). The outcomes from John’s case exemplar were very favorable.
Forty-eight hours after CRRT was started, John’s potassium level was 3.5, his creatinine level was 6.3, and his BUN was 61. Potassium was added to his intravenous fluids and his electrolytes continued to trend toward normal.
After five days of the initiation of antibiotic, John’s sepsis was slowly resolving and he was weaned from both the ventilator and his vasoactive drips. Total parenteral nutrition and IV antibiotics were continued until day 14 of hospitalization. John’s renal function returned and he was discharged from the hospital on day 18.
The AACN Synergy Model is especially applicable in critical care areas where patient care is very complex. ARF occurs in two-thirds of intensive care patients and those who are treated with CRRT have a mortality rate of 40-60% even with correction of biomarkers.
Utilization of nursing competencies in the AACN Synergy Model for screening, treatment options, and measureable outcomes in ARF will provide optimal patient outcomes as evidenced by decreased length of stay, decrease costs, and decreased mortality.

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