What is the mortality rate in the Intensive Care Unit (ICU)?

Mortality Rate in the ICU

The average mortality rate in intensive care units (ICU) is approximately 35%, with significant variation depending on patient population, underlying conditions, and geographic location. 1

General ICU Mortality Statistics

• ICU mortality rates vary widely across different studies and patient populations, ranging from 0% to 72%, with a mean ICU mortality rate of 34.9% according to recent comprehensive data 1
• Hospital mortality for ICU patients is even higher, with a mean rate of 45% (range 5-72%) 1
• Mortality rates in ICUs have remained relatively stable over time despite advances in medical technology and treatment protocols 1
• In large-scale studies, mortality was almost four times higher in ICU patients compared to non-ICU patients (18% versus 5%) 1

Factors Affecting ICU Mortality

Patient-Specific Factors

• Age is a significant determinant of mortality, with older patients having higher mortality rates 2
• Male sex is independently associated with increased mortality risk (HR 1.57) 2
• Pre-existing conditions significantly impact survival rates, particularly:
  • Chronic obstructive pulmonary disease (HR 1.68) 2
  • Type 2 diabetes (HR 1.18) 2
  • Hypercholesterolemia (HR 1.25) 2

Disease-Specific Factors

• Severe respiratory failure requiring invasive mechanical ventilation is associated with higher mortality 1
  • Approximately 48.8% of ICU patients require invasive mechanical ventilation 1
  • High fraction of inspired oxygen (FiO2) at admission is an independent risk factor for death (HR 1.14) 2
  • Low PaO2:FiO2 ratio is associated with increased mortality (HR 0.80) 2
• Septic shock significantly increases mortality risk, with approximately 50% of severe community-acquired pneumonia (CAP) ICU admissions being associated with septic shock 1
• Development of multiple organ dysfunction dramatically increases mortality risk 1

Timing of ICU Admission

• Early ICU admission is associated with better outcomes compared to delayed admission 1
• Patients admitted to ICU after being on a medical ward for 1-2 days typically have worse outcomes than those admitted directly from the emergency department 1
• A large retrospective analysis showed mortality rates of 46.3% for patients admitted to ICU within 2 days of hospital admission, rising to 50.4% for those admitted between 2-7 days, and 57.6% for those admitted after 7 days 1

COVID-19 ICU Mortality

• During the COVID-19 pandemic, ICU mortality rates were initially higher than typical ICU mortality:
  • Early in the pandemic (up to May 2020), ICU mortality for COVID-19 patients was 41.6% 3
  • By September 2020, this had decreased to 35.5%, likely due to improved treatment protocols 4
• In a large Italian cohort study of 3,988 critically ill COVID-19 patients:
  • 48.7% died in the ICU 2
  • 53.4% died in the hospital overall 2
  • Median ICU length of stay was 12 days 2

Special Populations and Considerations

• Elderly patients (≥90 years) have higher absolute mortality but interestingly, excess mortality (beyond expected population mortality) was not significantly influenced by age within this group 5
• ICU acuity level impacts outcomes - counterintuitively, low-risk patients have better outcomes in high-acuity ICUs compared to low-acuity ICUs 6
• For patients with severe community-acquired pneumonia, ICU mortality rates range from 20% to 50% depending on admission criteria 1

Trends and Variations

• ICU admissions for certain conditions like severe community-acquired pneumonia have been increasing over time 1
• Geographic variations exist in ICU mortality rates, with significant differences observed between regions 4
• Mortality rates can be significantly higher during surge situations, such as pandemics, due to strain on healthcare systems 1

Common Pitfalls in Interpreting ICU Mortality Data

• Reported mortality rates may vary based on whether they include patients still in ICU at the time of reporting 3
• The true mortality rate should be calculated based on completed ICU episodes (either discharge or death) rather than crude rates 3
• Registry data often reports lower mortality rates compared to individual studies or cohorts 4
• Lack of standardization in reporting prevents accurate comparison between different studies and regions 4