WCS27 Metabolic Response In Surgical Patients Flashcards
Metabolic response of body to operation
Operation: A form of tissue trauma and stress
Body’s response:
- to ensure survival from acute stress and recovery
- attenuate consequence of stress + achieve homeostasis
- have wound healed
- at the consumption of body’s store of energy and protein
- magnitude of response: dependent on degree of trauma and stress
Stress during operation
- Low room temperature + Low humidity
—> Heat and Fluid loss from patient - Exposure of viscera to air
—> Heat and Fluid loss from patient - Bleeding
—> Fluid loss from patient - Skin incision, muscle / fascia division
- Tissue trauma
- Hypothermia
- Bacterial contamination
Consequence of trauma and stress
Tissue trauma:
- ***Inflammatory response
Bleeding:
- ***Hypotension
- ***Hypoperfusion of vital organs
- Blood transfusion —> ***Immunosuppression (due to the infusion of allogeneic donor leukocytes, or their products, present in the cellular blood products)
- **Hypothermia:
- Vasoconstriction
- ↓ CO
- ***Coagulopathy
Bacterial contamination:
- ***Infection
Exposure of viscera to air:
- ***Fluid loss
- Hypothermia
Desiccation of wound:
- Infection
Consequence of failed wound healing
Abdominal wound:
- Evisceration
Anastomosis:
- Bowel —> Peritonitis —> Mortality
- Blood vessels —> Bleeding —> Loss of organ function
Phases of metabolic response
- Ebb phase
- phase of metabolic response to operation - Flow phase
- phase of metabolic response after operation - Anabolic phase
- recovery from operation
- Ebb phase
Stress response occurs within the first 12 to 48 hours after injury
- ↑ Catecholamine, ↑ Glucagon
—> ↑ Blood glucose
—> ↑ Lactate
—> ↑ Free fatty acids - ↓ CO
—> Organ hypoxia and ischaemia
—> ↓ Oxygen consumption - Below-normal core temp
—> ↓ Oxygen consumption
Outcome:
- Succumb from ischaemia, lack of O2 and nutrient supply to major organs
- Survive if injury not severe and homeostasis is achieved by body’s response
- Survive even if severe injury if prompt resuscitation given, BP, CO maintained —> complete homeostasis achieved
- Flow phase
Metabolic response aims at **Wound healing + **Restoration of function
- **Hypermetabolism:
1. ↑ Catecholamine, Glucagon, Cortisol, Insulin in blood
2. ↑ CO, blood flow rate
Clinical manifestations:
- ↑ HR, Pulse rate
- ↑ RR
- ↑ body temp
Purpose:
- ↑ blood flow to wound to promote wound healing
- ↑ blood flow to vital organs to maintain function
Response:
1. ↑ Catecholamine, Glucagon, Cortisol, Insulin in blood
—> -/↑ Glucose + -/↑ FFA + Normal lactate
—> ↑ consumption of glucose, FFA, a.a.
—> ↑ O2 consumption
—> ↑ CO2 production + heat production
- ↑ CO, Body temp
—> ↑ O2 consumption
—> ↑ CO2 production + heat production - ↑ Aldosterone, ADH
—> Fluid retention - IL1, IL6, TNF spillage from wound
—> Systemic inflammatory response
—> Multi-organ failure
Wound healing process
- Inflammatory reaction
- ***Removal of debris, blood clots and bacteria by macrophage
- ***Formation of new blood vessels, collagen, epithelium
Early stage:
1. **Cytokine released from **macrophage
—> Vasodilatation, ↑ Blood flow, ↑ Leakage of fluid from capillaries, Migration of leukocytes across blood vessel wall into site of injury
- IL-1 (Fever)
- TNF-α (Fever, Shock, Systemic inflammatory response syndrome (SIRS))
- IL-6 (Fever)
- IL-8
- IL-12
- Signs of inflammation (erythema, induration, edema)
Intermediate stage:
- Scab formation
- ***Fibroblast go into wound, Less macrophage
Late stage:
- ***Restoration, Scars remain
Prerequisite for perfect wound healing
- Supply of ***nutrients for actively dividing cells
- amino acids, glucose, fatty acid - Supply of ***oxygen
- Good tissue blood supply and venous drainage
- ***Minimal necrotic debris
Supply of nutrients in absence of feeding:
1. ***Glycogen store in liver and muscle
—> muscle atrophy if used up
- Mobilisation of **amino acids from muscle + **fatty acids from body fat
—> weight loss
—> malaise, muscle weakness
—> predisposition to bronchopneumonia (weak cough)
—> mortality from chest infection
Cytokine production
- IL1, IL6, IL8, IL12, TNF-α released by macrophage accumulate in wound
- Important for local inflammatory response and promotion of wound healing
- ***Massive cytokine production if tissue trauma is extensive
- Absorption of cytokines into systemic circulation
—> ***Systemic inflammatory response
—> Aggravation of clinical sign of hypermetabolism
Systemic Inflammatory Response Syndrome (SIRS)
- Body temp >38 oC
- HR >90 /min
- RR >20 /min OR PaCO2 <32 mmHg
- ***WBC >12 x10^9/L
Causes of multi-organ failure as a result of systemic inflammatory response
- Leakage of fluid from capillaries into interstitial space —> tissue edema —> ↑ in intercapillary distance —> ↓ nutrient and O2 supply to cells
- Thrombi within terminal branches of artery —> Ischaemia
- Tissue ischaemia in organs —> macrophage infiltrate of organ —> more cytokine production
Organs affected in SIRS
Brain: Encephalopathy Nerve: Polyneuropathy Muscle: Myopathy of critical illness Lung: ARDS Heart: Cardiogenic shock, Peripheral edema GI tract: Delayed gastric emptying, Stress ulcer, Paralytic ileus, Anorexia Kidney: Acute tubular necrosis (AKI) Blood: DIC
Metabolic response to surgery
- Beneficial for recovery
- Cost may be substantial
- SIRS will subside if serious, continuing, superimposed insult (i.e. infection, bleeding) is avoided / eradicated
- Anabolic phase
- Recovery, ↑ nutrient intake
- Loss of retained fluid
- Restoration of lean body mass, body weight, fat store and well being
