Stages of progression
Globally, the postoperative period is divided into early (until discharge from the hospital) and late (from discharge to the final outcome) stages. Pathophysiologically, three consecutive phases are distinguished:
- Catabolic phase (3–7 days). A protective response to surgical stress. The body mobilizes plastic and energy resources. It is characterized by the predominance of protein breakdown (first, proteins of the liver, plasma, and gastrointestinal tract suffer, then muscles). The patient is lethargic or restless, with tachycardia, shallow breathing, and oliguria.
- Phase of reversal (4–6 days). A transitional period occurring in an uncomplicated course. The activity of the sympathoadrenal system decreases, water and electrolyte balance is restored (potassium is retained in cells). The patient's pain subsides, temperature normalizes, appetite returns, and peristalsis starts.
- Anabolic phase (2–5 weeks). The recovery period. Under the action of growth hormone and androgens, proteins, fats, and glycogen are actively synthesized. Body weight and the functions of all systems are restored. Final scar formation can last up to 3–6 months.
Pathophysiology of surgical stress
Surgery triggers a powerful neuroendocrine response. The hypothalamus, pituitary gland, and sympathetic nervous system are activated.
The blood concentration of catecholamines, glucocorticoids, aldosterone, and ACTH sharply increases. Meanwhile, insulin levels drop, leading to hyperglycemia.
Cascade of disorders:
- Neurohumoral shift causes vasospasm.
- Microcirculation is disrupted, leading to tissue hypoxia.
- Aerobic glycolysis is replaced by anaerobic, and metabolic acidosis develops.
- Fluid leaks into tissues, blood thickens, and the risk of stasis arises. The myocardium, liver, and kidneys are the first to suffer from these changes.
Monitoring and severity criteria
After complex procedures, patients are transferred to intensive care units (ICU). Assessment is based on identifying critical deviations that require emergency care.
| System | Red flags |
|---|---|
| Cardiovascular | Heart rate > 120, BP $\le$ 80 or $\ge$ 200 mmHg, CVP < 50 or > 110 mm H2O |
| Respiratory | Respiratory rate > 28 per minute, dull percussion sound, absent breath sounds |
| Excretory | Diuresis < 10 ml/h (oliguria) or anuria |
| GI tract | «Board-like» abdomen, absence of peristalsis > 3 days, melena |
| Wound | Massive bleeding, evisceration (organ protrusion), purulent discharge |
Basics of intensive care
The main tasks of doctors during this period are to correct metabolic shifts, establish $O_2$ delivery, and replenish energy expenditure.
- Nutritional support: Crucial to compensate for protein loss (which can reach 400 g in 10 days). Priority is given to early enteral nutrition.
- Pain management: Adequate analgesia (including epidural anesthesia) prevents excessive sympathetic stimulation and allows the patient to breathe deeply.
- Respiration and hemodynamics: Oxygen therapy, breathing exercises, infusion of fluids (e.g., dextrans) to correct microcirculation.
To remember the sequence of metabolic phases, use the acronym «KORA» (Catabolic, Of Reversal, Anabolic).
Class and exam questions
Why does the patient breathe frequently and shallowly during the first 24 hours after surgery?
This is due to pain in the surgical wound area, high standing of the diaphragm caused by intestinal paresis, and limited mobility.
Where does the body get protein during the catabolic phase?
First, rapid breakdown of liver proteins, blood plasma, and the gastrointestinal tract occurs, and only then — slow breakdown of skeletal muscle proteins.
What does a positive nitrogen balance mean in the phase of reversal?
This means that the nitrogen introduced into the body becomes greater than that excreted in the urine. This shift indicates the onset of active protein synthesis.
What else to study on this topic
- Detailed mechanism of neurohumoral regulation of surgical stress
- Specifics of protein metabolism in extensive GI resections
- Methods of water-electrolyte balance correction in the ICU
- Symptoms of peritoneal irritation and differential diagnosis of complications
- Organization of enteral and parenteral nutrition in surgical patients
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