🩺 AKI in ICU: Causes, Diagnosis, Management & Survival Guide (Complete 2025 Updated Post)

Author: Dr Sanjay Prajapati
Category: Critical Care | Nephrology
Reading Time: 8 minutes🩺 AKI Acute Kidney Injury in ICU: Causes, Diagnosis, Management & Survival Guide (Complete 2025 Updated Post)

🔍 Overview

Acute Kidney Injury (AKI) in ICU patients is a life-threatening emergency with high mortality. Learn causes, KDIGO staging, diagnosis, management, dialysis indications, and prevention in this complete ICU guide.

🧠 What is Acute Kidney Injury (AKI)?

Acute Kidney Injury (AKI) is a sudden decline in kidney function over hours to days.
It is extremely common in ICU patients and has a 50–80% mortality rate.

📌 KDIGO Definition of AKI

AKI is diagnosed if any of the following occur:

• Increase in serum creatinine ≥ 0.3 mg/dL within 48 hours
• Increase ≥ 1.5 × baseline within 7 days
• Urine output < 0.5 mL/kg/hour for 6 hours

Important: Criteria should be applied only after optimizing fluid status.

🚦 AKI Staging (RIFLE, AKIN, KDIGO)

🔥 RIFLE Criteria

🔥 AKIN Criteria

• Stage 1: 1.5× Cr or +0.3 mg/dL
• Stage 2: 2× Cr
• Stage 3: 3× Cr, Cr >4 mg/dL, or dialysis needed

🩸 Why Serum Creatinine Is Not Reliable Alone

• It lags behind injury
• eGFR formulas do NOT apply in AKI
• Affected by muscle mass, hydration, and distribution volume

⚠️ Causes of AKI (Prerenal, Intrinsic, Postrenal)

1️⃣ Prerenal (Most Common in ICU — Hypoperfusion)

• Volume loss (diarrhea, vomiting, hemorrhage)
• Hypotension
• Heart failure
• NSAIDs
• Contrast-induced AKI
• Hepatorenal syndrome

2️⃣ Intrinsic AKI

• ATN (Acute Tubular Necrosis) – ischemia, sepsis, drugs
• Glomerular: GN, Goodpasture
• Interstitial: drug allergy, pyelonephritis
• Vascular: renal artery stenosis, emboli

3️⃣ Postrenal (Obstruction)

• Prostate enlargement (BPH)
• Bilateral stones
• Tumors
• Neurogenic bladder
• Retroperitoneal fibrosis

🧪 Diagnosis & Workup in AKI

🔹 History & Examination

Check for:

• New medications
• Fluid loss
• Heart failure signs
• Edema, JVD
• Bladder distension
• CVA tenderness

🔹 Key Investigations

• BUN, Creatinine
• ABG, Electrolytes
• CBC
• Serology: ANA, ANCA, HBV, HCV, anti-GBM

🧫 Urinalysis Clues (Very Important for Differentiation)

Prerenal AKI

• Bland urine
• High osmolality
• Low Na (<20 mEq/L)
• FeNa <1%

Intrinsic AKI (ATN)

• Muddy brown casts
• Na >40
• FeNa >2%
• Osm <350

🖥️ Ultrasound Findings

• Hydronephrosis → obstruction
• Small kidneys → chronic disease
• Normal size → acute process

🏥 AKI in ICU: Why More Dangerous?

Incidence in ICU: 40–60%

Mortality: >50%

Risk Factors

• Age
• Sepsis
• Liver disease
• Heart failure
• Mechanical ventilation

💉 Management of AKI in ICU

1️⃣ General Principles

• Treat underlying cause
• Maintain MAP > 60 mmHg
• Avoid nephrotoxic drugs
• Optimize fluids
• Track I/O, weight, BP
• Correct electrolytes

💊 Dialysis Indications — AEIOU (Life-Saving Rule)

🛠️ Dialysis Modalities

🌀 Intermittent Hemodialysis (IHD)

• Fast removal
• Best for small molecules

💧 CRRT (Continuous Renal Replacement Therapy)

• Gentle
• Ideal for unstable patients
• Less hypotension

🫧 Peritoneal Dialysis

• Alternative when others unavailable

🔄 Stopping Dialysis

Stop when:

• Urine output improves
• Creatinine starts declining
• Creatinine clearance rises

🛡️ Prevention of AKI

Non-Drug

• Hydration
• Maintain MAP
• Avoid nephrotoxins

Drug-Based

• Diuretics
• Mannitol
• Fenoldopam
• Natriuretic peptides

🧭 Prognosis

• Mortality >50% with multiorgan failure
• Many recover, but some develop chronic kidney disease
• Prevention is the key to survival

❓ Frequently Asked Questions (FAQ)