A9 Surgery

Topic

Surgery physically reorganizes the body through the removal, repair, or reconstruction of tissues and organs. This intervention triggers a systemic stress response involving hormonal and nervous mechanisms. Although initially an adaptation intended to help the body withstand the surgical insult, it can become excessive during major operations or in patients with pre-existing medical conditions.

One of the primary hormonal responses is a rise in cortisol levels. During surgery and general anesthesia, blood cortisol concentration increases, peaks, and subsequently declines until returning to normal. While elevated, cortisol increases glucose availability, partially suppresses immune activity, and promotes protein breakdown. Regional anesthesia can attenuate this response by blocking some of the signals originating from the surgical site before they activate systemic stress pathways.

Anesthesia must be maintained at a sufficient depth throughout the procedure. For inhaled anesthetics, the reference point used is the concentration at which approximately half of patients do not move in response to a surgical incision. Based on this reference, the concentration is adjusted according to the patient's specific characteristics and individual response.

Fluid balance is another fundamental aspect; both deficits and excesses can lead to complications. During major surgery, some fluid may shift from the effective circulation into the interstitial space, the bowel, and traumatized tissues—a phenomenon known as "third-spacing." In major abdominal operations, this redistribution can involve significant fluid volumes for every hour of the procedure.

To avoid fluid replacement based solely on predetermined estimates, goal-directed fluid therapy utilizes circulatory parameters measured during the operation. Fluid administration is adjusted according to the patient's hemodynamic response to each bolus, aiming to maintain adequate circulation without causing dehydration or volume overload.

Once surgery concludes, the healing process begins. First, bleeding is controlled; next, an inflammatory phase ensues; subsequently, tissue proliferates to fill the wound; and finally, a remodeling phase occurs, reorganizing the new tissue. Mechanical strength increases progressively—rapidly at first and more slowly thereafter—eventually reaching a high fraction of the original strength (close to 80%) after several weeks.

Different wound functions recover at varying rates. The skin barrier against microorganisms may be restored within one or two days, whereas the strength required to remove sutures without the wound reopening takes approximately one or two weeks. Remodeling and the development of the scar's final strength continue for several months.

Surgical risk is also assessed prior to a procedure. This evaluation combines the patient's baseline health status with characteristics of the operation, such as its magnitude and urgency. General health status can range from that of a healthy individual to that of a patient with a life-threatening condition unrelated to the surgery. Risk calculators integrate this information with other variables to estimate the likelihood of serious complications or death during the perioperative period. Risk increases when significant pre-existing disease and urgent surgery coincide.

Overall, surgical management encompasses far more than the physical intervention on the tissues. The systemic stress response must be modulated via anesthesia; the depth of anesthesia requires adjustment during the procedure; circulatory status necessitates fluid replacement tailored to the individual's response; and the time course of healing must be respected post-procedure. Concurrently, preoperative risk assessment allows for an evaluation of the balance between benefits and potential complications. Clinical practice integrates these elements before, during, and after surgery to ensure that the anatomical repair or reorganization yields the expected benefit with the lowest possible risk to the patient.

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