Surgery is a significant physiological stressor that triggers a complex response in the body. This stress response can be categorized into two main components: the neuroendocrine-metabolic response and the inflammatory-immune response. The extent and impact of this response depend on various factors, including the type and invasiveness of the surgical procedure.
| Categories of Stress Response |
|---|
| 1. Neuroendocrine-Metabolic |
| 2. Inflammatory-Immune |
Impact of Surgery
General anesthesia, commonly used during surgery, has limited influence on cytokine responses. This is because the surgical procedure itself serves as the primary trigger for the stress response. Therefore, understanding and managing the stress response becomes essential in perioperative care.
| Surgery’s Impact on the Body |
|---|
| Surgery triggers stress response |
| Anesthesia minimally affects cytokine responses |
The Body’s Adaptive Response
The stress response is the body’s adaptive mechanism to the perioperative environment. While it serves a vital purpose, it can also have drawbacks. These drawbacks include:
| Consequences of Stress Response |
|---|
| 1. SIRS |
| 2. Hypermetabolism |
| 3. Hypercatabolism |
| 4. Disrupted Negative Feedback |
Physiological Responses to Surgical Stress
Surgical stress induces a range of physiological responses, encompassing the neuroendocrine-metabolic, endocrine, and inflammatory-immune systems. These responses play a crucial role in the body’s adaptation to the stress of surgery. In this article, we will delve into these responses and their significance in the perioperative period.
| Response Systems | Key Elements | Impact |
|---|---|---|
| Neuroendocrine-Metabolic Response | – Sympathetic Nervous System (SNS) activation | – Mobilization of carbohydrate and fat stores |
| – Release of adrenaline (epinephrine) | – Increased heart rate and vascular smooth muscle tone | |
| – Shift in blood flow to active muscles | – Enhanced coagulability of blood | |
| Endocrine System Response | – Corticotrophin-releasing hormone (CRH) release | – Activation of hypothalamo-pituitary-adrenal (HPA) axis |
| – Adrenocorticotropic hormone (ACTH) secretion | – Promotion of glucocorticoid (cortisol) release | |
| – Growth hormone (GH) secretion | – Hepatic glycogenolysis and insulin resistance | |
| – Antidiuretic hormone (ADH) release | – Regulation of extracellular fluid volume | |
| – Other hormonal changes (prolactin, testosterone, thyroid hormones) | – Normalization within days to weeks | |
| Metabolic Response | – Hypermetabolism and hypercatabolism | – Mobilization of energy sources |
| – Hepatic glycogenolysis, skeletal muscle proteolysis, and fat lipolysis | – Maintenance of blood glucose levels | |
| – Sympathetic-induced glucagon stimulation | – Reduction of insulin release and insulin sensitivity | |
| – Activation of renin-angiotensin-aldosterone system (RAAS) | – Fluid retention, increased vascular tone | |
| Inflammatory-Immune Response | – Activation of innate immune system | – Production of proinflammatory cytokines (e.g., IL-6, TNF-a) |
| – Migration of monocytes, neutrophils, and macrophages | – Potential for systemic inflammatory response syndrome (SIRS) | |
| – Activation of natural killer (NK) cells | – Cytotoxicity against damaged and infected cells | |
| – Production of pro- and anti-inflammatory cytokines | – Regulation of the inflammatory response | |
| – Acute phase response (increase in acute phase proteins) | – Early innate immunity and response to tissue injury |
Neuroendocrine-Metabolic Response
The neuroendocrine-metabolic response involves the activation of the sympathetic nervous system (SNS) and hormonal changes, primarily mediated by adrenaline (epinephrine). This response enhances energy mobilization, increases heart rate, redirects blood flow, and promotes coagulability.
Endocrine System Response
The endocrine response is coordinated by the hypothalamus, which triggers the hypothalamo-pituitary-adrenal (HPA) axis. This leads to the secretion of cortisol, growth hormone, and antidiuretic hormone (ADH). These hormones play roles in regulating metabolism, immune function, and fluid balance.
Metabolic Response
Surgical stress induces a state of hypermetabolism and hypercatabolism, mobilizing energy sources such as glycogen, muscle tissue, and fat stores. This response is characterized by altered insulin and glucagon levels, contributing to hyperglycemia and muscle catabolism.
Inflammatory-Immune Response
The inflammatory-immune response involves both the innate and adaptive immune systems. Surgical stress activates innate immune cells like macrophages and neutrophils, leading to the production of proinflammatory cytokines. The balance between pro- and anti-inflammatory responses influences patient outcomes and the risk of complications.
Monitoring Postoperative Recovery
Various blood markers, including cortisol, IL-6, white blood cell count (WCC), and C-reactive protein (CRP), can help track postoperative recovery. IL-6 and CRP, in particular, are associated with the magnitude of surgical stress and can serve as early indicators of infection or excessive inflammation.
Modulation of the Perioperative Stress Response
The physiological stress response to surgery can have significant implications for patient outcomes. Several strategies, including the use of anesthetic drugs, analgesics, regional anesthesia, surgical techniques, glucocorticoids, and nutrition/fluid management, can be employed to modulate this response and minimize its adverse effects. Below, we explore these strategies in detail.
| Anesthetic Drugs | Mechanism | Effects |
|---|---|---|
| I.V. and Volatile Anaesthetic Agents | – Propofol (continuous infusion) can block cortisol secretion. | – Propofol emulsion containing triglycerides may reduce proteolytic response. |
| – Etomidate inhibits cortisol and aldosterone synthesis. | – Considered obsolete due to increased mortality in sepsis. | |
| – Volatile agents (e.g., sevoflurane, isoflurane) inhibit ACTH, cortisol, catecholamines, and GH. | – May impair platelet aggregation and clot stability. | |
| Analgesics and Other Medications | Mechanism | Effects |
| Benzodiazepines | – Inhibit cortisol production at the hypothalamicepituitary level. | – Effect on surgical outcomes not clear. |
| a2-Adrenergic Agonists (Clonidine, Dexmedetomidine) | – Inhibit surgical stress response mediated by the sympathetic nervous system (SNS). | – Reduce cortisol and renin concentrations, impart haemodynamic stability. |
| Opioids | – Reduce ACTH and GH secretion by reducing CRH release. | – High-dose opioids can suppress ACTH and cortisol secretion but may require postoperative ventilatory support. |
| – Opioids have immunomodulatory effects, with varying impact on immune function. | – Conflicting evidence regarding their effect on tumor growth and cancer recurrence. | |
| Regional Anaesthesia | Mechanism | Effects |
| Neuraxial Analgesia | – Blocks HPA axis response by preventing afferent activation of hypothalamus and efferent stimulation of organs. | – Impairs secretion of adrenocorticotropic hormone, cortisol, adrenaline, and GH. |
| – Potential benefits include earlier return of gut function, reduced pulmonary dysfunction, and reduced inflammatory response. | – May affect coagulation positively. | |
| Surgical Techniques | Mechanism | Effects |
| Minimally Invasive Surgery (e.g., Laparoscopic, Robotic) | – Reduces tissue injury and duration of surgery. | – Lowers concentrations of proinflammatory biomarkers (e.g., IL-6, CRP). |
| – Associated with enhanced recovery after surgery (ERAS) programs. | – Decreases the need for postoperative analgesia. | |
| Glucocorticoids | Mechanism | Effects |
| Perioperative Supplementation | – Reduces proinflammatory mediators (e.g., IL-6, IL-8, CRP) in some surgeries. | – May lower pulmonary complications and infection rates. |
| – Concerns about potential hyperglycemic response in diabetic patients. | – Effects on patients with reduced cortisol response require further study. | |
| Nutrition and Fluids Management | Mechanism | Effects |
| Enhanced Recovery After Surgery (ERAS) | – Reduces fasting time, includes preoperative carbohydrate loading. | – Lowers fluid requirements, improves insulin resistance, and reduces catabolism. |
| – Emphasizes early enteral feeding and multimodal analgesia. | – May involve immunonutrition with specific supplements (e.g., glutamine, arginine, omega-3 fatty acids). |
In summary, the modulation of the perioperative stress response involves a multifaceted approach that encompasses various aspects of anesthesia, analgesia, surgical techniques, and perioperative care. These strategies aim to mitigate the negative effects of surgical stress, optimize patient recovery, and improve overall outcomes. However, the choice and combination of interventions should be tailored to each patient’s specific needs and the nature of the surgical procedure.