Physiological Responses to

Surgery & Trauma

Muhammad Shoyab

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5th Year MBBSSir Salimullah Medical College

May 05, 2009Revised : July 2015

Surgery is a major stress . . .

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. . . that not only overwhelms the patient’s psychology . . .

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. . . but also overburdens physiology & homeostasis.

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But is this what we want?

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The answer is NO

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The aim of modern surgical practice is to ensure

stress-free peri-operative care.

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which means . . .Iatrogenically created imbalances

corrected by therapeutic interventionrather than overburdening homeostasis

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The stress response is a neuroendocrine process.

CSDT9

With metabolic & biochemical components

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Stress Response

Metabolic

BiochemicalFluid &

Electrolytes

SYMPATHETIC CHAIN

CRHTRHGHRH

CORTISOL

ADRENALINE

GLUCAGON

ACTH THYROXINE

TSH

Injury

Sensory Nerves

THALAMUS

Nociceptors

ADRENAL

PANCREAS

HYPOTHALAMUS

THYROID

PITUITARY

B&LINSULIN

GROWTH HORMONE

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CSDT12

Metabolic Changes

ProteolysisLipolysisGlycogenolysisDecreased peripheral glucose uptake (insulin resisance)Neoglucogenesis

CSDT

Summary of Metabolic Effects

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This is known as the acute phase reaction or the catabolic phase.

It lasts for 24 – 48 hours.

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Objective : To conserve volume and energy to combat the stress.

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In addition to metabolic, the stress response also produces biochemical changes

Best Practice & Research Clinical Anaesthesiologyhttp://www.sciencedirect.com

Stress Response

Metabolic

Biochemical

Fluid & Electrolytes

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ALDOSTERONE

SYMPATHETIC CHAIN

Injury

Sensory Nerves

Nociceptors

ADRENAL

ADH

PITUITARYAnaesthetics Vasodilation

ECV falls

Inflammation

IL-1 , TNF

Increased vascular permeability

Albumin escapes into ISF

Water osmoses to ISF

Pre-op fasting / fluid loss

Perioperative evaporation

TBW falls

RAA Axis

Best Practice & Research Clinical Anaesthesiologyhttp://www.sciencedirect.com

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BIOCHEMICAL CHANGES

OLIGURIA

ADH

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OLIGURIA

ADHThus, salt (NaCl) and water are retained avidly in the first few days.

Best Practice & Research Clinical Anaesthesiologyhttp://www.sciencedirect.com

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Hence, no extra sodium is

needed in the first 24 – 48

hours.

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Inflammation

IL-1 , TNF

Increased vascular permeability

Increased cellular permeability

Na enters cells

Fall of serum sodium

In reality, total body sodium is conserved or even overloaded, but serum sodium level appears low.

So, this is called pseudohyponatraemia. Best Practice & Research Clinical Anaesthesiology

http://www.sciencedirect.com

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This is why, administration of sodium is restricted over the first few days after surgery, to avoid further overloading of sodium.

Protein catabolism is accompanied by potassium efflux.

CSDT21

Proteins maintain the intracellular negative charge.

Loss of proteins from the cell creates an electrical imbalance . . .

. . . which is balanced by potassium efflux. This may result in hyperkalaemia.

This potassium is lost in exchange of sodium during the sodium retention phase.

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However, the catabolic phase is soon overtaken by anabolism.

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During the anabolic phase, glycogen and protein are resynthesized.

This causes rapid reuptake of K+.

This may lead to hypokalaemia unless carefully supplemented.

Best Practice & Research Clinical Anaesthesiologyhttp://www.sciencedirect.com

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Hence, potassium supplementation must be done

carefully – no excess, no deficit.

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Factors of Stress

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• Adequate fluid therapy to maintain the effective circulatory volume while avoiding interstitial fluid overload

• Minimal preoperative fasting

• Adequate analgesia

• Early post-operative mobilization

• Early return to oral feeding

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Ways to Reduce Stress

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Stress-free peri-operative care

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Stress-free peri-operative care

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