5 Complications and Integrated Practice

Assess the patient and identify the cause

Acute kidney injury (AKI) can disrupt fluid balance, electrolyte levels, and acid–base regulation. Priorities are to identify the likely cause, recognize immediately dangerous complications, and monitor the patient’s response to interventions.

Initial assessment and trends

• Assess airway, breathing, circulation, mental status, vital signs, and oxygenation. Severe shortness of breath, chest pain, new confusion, dangerous heart-rhythm changes, or rapidly worsening weakness require urgent escalation.

• Assess volume status and urine output by reviewing intake and output, recent weight change, edema, lung sounds, and blood pressure. Oliguria—commonly less than $0.5\ \mathrm{mL/kg/hour}$—is a warning sign, but its cause and the overall clinical picture matter.

• Consider reduced kidney perfusion, such as from dehydration, bleeding, or shock; kidney tissue injury, such as from sepsis, nephrotoxic exposure, or prolonged ischemia; and urinary obstruction. Review medications and assess for obstruction when indicated.

• Follow trends in creatinine and blood urea nitrogen (BUN), potassium, sodium, bicarbonate, calcium, phosphorus, and urinalysis. Obtain an electrocardiogram (ECG) when hyperkalemia is suspected or present.

After interventions, reassess urine output, respiratory status, blood pressure, fluid balance, and repeat laboratory results as clinically directed.

Recognize and respond to fluid overload

Reduced kidney function may cause fluid retention, edema, hypertension, and pulmonary edema. Increasing breathlessness, low oxygen levels, or crackles may indicate that fluid is affecting the lungs; escalate promptly, support breathing as needed, and notify the clinical team.

Fluid administration should be guided by the assessment. Fluids may help when there is volume depletion, but can worsen overload. Do not assume every patient with AKI needs fluid boluses or fluid restriction: individualize management according to volume status and reassess.

Manage hyperkalemia

Potassium can rise when the kidneys cannot excrete it effectively. Hyperkalemia may cause dangerous conduction abnormalities, although the ECG can be normal even when potassium is high. Treat severe hyperkalemia, or hyperkalemia accompanied by ECG changes, as urgent.

Management has three distinct goals: protect the heart from dangerous electrical effects, shift potassium into cells when appropriate, and remove potassium from the body. Dialysis may be required when hyperkalemia is severe or refractory to medical treatment.

Interpret acid–base and other laboratory changes

Impaired kidney function may contribute to metabolic acidosis, reflected by low bicarbonate and, when measured, low blood pH. Phosphorus may rise and calcium may fall; the clinical significance of these changes depends on their severity and context.

Rising creatinine and BUN support impaired kidney function, but neither value by itself establishes the need for dialysis.

Recognize uremic complications

Accumulation of waste products may cause nausea, poor appetite, itching, or fatigue. Serious uremic complications include encephalopathy, pericarditis, and a bleeding tendency. New altered mental status or chest pain in a patient with worsening kidney failure warrants urgent evaluation.

Decide when kidney replacement therapy is needed

Consider kidney replacement therapy when a life-threatening fluid, electrolyte, or acid–base problem exists, or when a significant complication such as uremic encephalopathy or pericarditis requires it. Examples include refractory hyperkalemia, severe acidosis, and fluid overload that causes respiratory compromise.

Base the decision on the clinical context and trends, not on a single BUN or creatinine threshold. Dialysis is considered when serious complications cannot be adequately controlled by other treatment—not simply because a laboratory value is high.

Monitor during hemodialysis

During hemodialysis, monitor blood pressure, symptoms, and vascular access. Hypotension and muscle cramps are common problems and may be associated with rapid fluid removal or changes in body-fluid balance. If a patient becomes dizzy, develops cramps, or has falling blood pressure during fluid removal, communicate the blood-pressure change, symptoms, timing, and fluid-removal context to the dialysis team, and follow the treatment team’s protocol.

Access infection, clotting, or poor blood flow can interfere with treatment. Fever or chills, redness or drainage at the access site, uncontrolled bleeding, or a fistula or graft that no longer has its usual vibration needs prompt attention.

Apply the priorities to clinical situations

Low urine output after illness

A patient with several days of vomiting and diarrhea has low urine output, blood pressure below their usual level, and a creatinine rise from baseline. The lungs are clear and there is no peripheral edema. Reduced kidney perfusion from volume depletion is a likely prerenal cause. Follow vital signs, volume status, intake and output, urine output, and kidney-function and electrolyte trends. Carefully guided fluid replacement may be needed; restricting fluid without assessing volume could worsen poor kidney perfusion. Assess for other causes if kidney function does not improve.

Possible hyperkalemic emergency

A patient with worsening AKI reports weakness and has markedly elevated potassium with new ECG conduction abnormalities. Treat this as an urgent, potentially life-threatening emergency and escalate care immediately. Address the goals of protecting the heart, shifting potassium into cells when appropriate, and removing potassium from the body. Consider urgent dialysis if hyperkalemia is severe or cannot be adequately controlled with medical treatment.

Worsening breathing and fluid retention

Increasing shortness of breath, low oxygen saturation, crackles, and worsening edema despite initial medical management raise concern for pulmonary edema from fluid overload. Escalate breathing and oxygenation concerns promptly, reassess volume status and vital signs, and notify the treating team. Consider dialysis or other kidney replacement therapy if fluid overload causing respiratory compromise cannot be controlled medically.

Symptoms during hemodialysis

Dizziness and painful leg cramps as blood pressure falls during fluid removal indicate intradialytic hypotension with muscle cramps. Report the blood-pressure change, symptoms, timing, and fluid-removal context to the dialysis team, and follow the treatment team’s protocol. Also assess for access infection or clotting, bleeding, and poor access flow.