Multiple Organ Dysfunction Syndrome

Question 1

What is MODS? Definitions..

Answer 1

• presence of altered function involving at least two or more organ systems in an acutely ill patient such that homeostasis cannot be maintained without intervention.*

• the development of potentially reversible physiologic derangement involving two or more organ systems not involved in the disorder that resulted in ICU admission, and arising after a potentially
life-threatening physiologic insult.

Progressive dysfunction of two or more interdependent organ systems resulting from an uncontrolled inflammatory response to a severe illness or injury.

MODS is defined as the progressive physiological dysfunction of two or more organ systems where homeostasis cannot be maintained without intervention (Nickson 2019)

Question 2

Causes

Answer 2

Sepsis / septic shock
= most common cause of MODS
= extreme immune response to an infection whereby the immune system can injure tissues and organs (can be life threatening).

Other triggers: severe trauma, major surgery, burns, heat stroke, liver failure, circulatory shock
OR… Any severe injury or disease process that activates systemic inflammation

Question 3

Organs / systems involved

Answer 3

6 main systems:
• Respiratory / lungs
• Cardiovascular / heart
• Renal / kidney
• Hepatic / liver
• Brain / CNS
• Haematologic / blood
Others...
• GI
• Immune system
• Endocrine / metabolism

Question 4

MODS progression… primary mods

Answer 4

Primary MODS
Direct organ injury – shock, trauma, necrosis
- Decreased perfusion
- Stress response
- Stress hormones (catecholamines - Adr)
- Local inflammation

Question 5

MODS progression… secondary mods

Answer 5

Secondary insult
(e.g. surgery / injury infection, ischemia …)

Triggers excessive inflammatory reaction from primed Macrophages (TNFa / IL-1)

• Widespread endothelial damage
• Infection present = amplification
• self perpetuating inflammation
• distant organ damage
• Metabolic stress in organ
• Enhanced inflammation

secondary mods… death

Question 6

Two hit model & inflammation

Answer 6

Meakin’s “two-hit” model of postinjury Multiple Organ Failure
• The first hit (trauma / shock ) primes neutrophils and macrophages
• The second hit (nosocomial infection/complication) results in detrimental inflammatory response

Involves many immune / inflammatory cell types including:
mast cells, macrophages, vascular endothelial cells, neutrophils.

Remember….
Role of immune cells is to kill / clean up infected, distressed, dying and dead cells

MODS is caused by an overwhelming imbalance between systemic inflammatory response and counter regulation (anti- inflammatory) response.

Question 7

MODS pathology

Answer 7

histologic features of the organs involved in MODS include evidence of
• oedema
• inflammation (imm cell infil.) • tissue ischemia or necrosis
• variable degrees of fibrosis and repair
(remember the dysfunction is partly reversible)

Question 8

Descriptors / Diagnosis 1

Answer 8

• first descriptions:
generally counted the number of failing systems,
& the need for clinical intervention for each system

• More recently:
several similar descriptive scales developed based on quantification of organ dysfunction as a numeric scale.
e.g.s
- Multiple system organ failure score
- Sequential organ failure assessments (SOFA) score
- Denver Postinjury MOF score

• In order to be diagnosed with MODS, the patient should be experiencing dysfunction of at least two organs (this may be mild or severe) in addition to systemic inflammatory response syndrome (Nickson 2019).

Question 9

Management / treatment

Answer 9

At present there is no agent that can reverse the established organ failure
• Therapy is supportive care, i.e. safeguarding haemodynamics, and respiration.
• Maintaining adequate tissue oxygenation is a principal target
• Starting enteral nutrition within 36 hours of admission to an intensive care unit has reduced infectious complications

MODS is less a syndrome to be treated than a complication to be prevented.

MODS is difficult to treat, escalates quickly and is often fatal. Therefore, early detection is crucial in preventing its progression

Question 10

Summary

Answer 10

• Multiple organ dysfunction caused by uncontrolled widespread inflammation
• Organs that fail are often not those directly injured in the initial insult
• Lag period of days to weeks
• Not all patients have sepsis (not all are infection induced)
• No septic focus found in in 30% of bacteremic patients dying of clinical sepsis and MODS
• Identification and treatment may not improve survival
• Main aim is early detection and prevention