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Reaction of the Body to Injury

• Homeostasis is the balanced state of the human body before injury or surgery.
• Homeostasis maintains nearly constant conditions in the internal environment.
• All organs and tissues perform functions that help to maintain these constant conditions.

Basic Concepts in Homeostasis

• Homeostasis is the foundation of normal physiology.
• Stress-free perioperative care helps to preserve homeostasis after elective surgery.
• Resuscitation, surgical intervention, and critical care can restore homeostasis in severely injured patients.

Metabolic Response to Injury

• The response to injury has two phases: Ebb and Flow.

• Ebb phase: Occurs in the first few hours after injury, characterized by cold, hypotension, potentially reversible shock (with resuscitation), or irreversible shock.

• Flow phase: If the individual survives the ebb phase, they enter the flow phase. This phase is further divided into two parts:

  • Catabolic flow phase: This initial phase lasts about a week, characterized by a high metabolic rate, protein and fat breakdown, resulting in net loss of body nitrogen and weight loss.
  • Anabolic flow phase: This phase lasts for around 2-1 weeks, follows the catabolic phase, and is characterized by the restoration of protein and fat stores, leading to weight gain and positive nitrogen balance.

• Metabolic response to injury is graded and evolves with time, with the severity of the injury correlating with the magnitude of the metabolic and immunological changes.

Physiological Response Components

• Physiological consequences
• Metabolic manifestations
• Clinical manifestations
• Laboratory changes

Clinical Response Components

• Fever
• Tachycardia
• Tachypnea
• Wound inflammation
• Anorexia

Laboratory Response Components

• Leukocytosis
• Hyperglycemia
• Hepatic renal dysfunction

Mediator of Injury Response

• Neuro-endocrine (hormonal) response to injury; acute phase (short-term survival) is characterized by the pituitary's active secretion and elevated counter regulatory hormones (cortisol, glucagon, and adrenaline). Chronic phase (chronic wasting) involves hypothalamic suppression and low circulating levels of target organ hormones.

Systemic Inflammation Response Syndrome (SIRS)

• SIRS is diagnosed when two or more of the following are present:
  • Heart rate > 90 beats/min
  • Temperature > 38°C or < 36°C
  • Respiratory rate > 20 breaths/min
  • White blood cell count (WBC) > 12,000/mm³ or < 4,000/mm³
• SIRS combined with a suspected or present source of infection equals sepsis.