Pathophysiology of Surgical Site Infection: A Comprehensive Interactive Tutorial

1. Interactive Tutorial By Rachel M Grooms Alverno College MSN 621 Advanced Pathophysiology Pathophysiology of Surgical Site Infection All images are imported from microsoft clip art. groomsrm@alverno.edu

2. Tutorial Directions • Hover over underlined text for further information. • To advance to the next slide: • Click or • Use space bar • To go back to the previous slide: • Click • To go to back to the first slide: • Click • To view specific content: • Click on the action buttons on the Menu slide

3. Outcomes • At the end of this tutorial you should be able to: • verbalize the importance of preventing infection post surgical incision • identify characteristics of the immune/inflammatory response initiated post surgical incision to prevent infection. • identify characteristics of the stress response occurring post surgical incision to prevent infection. • identify the relationship between genetics and infection post surgical incision. • identify surgical practices effective in preventing surgical site infection.

4. Tutorial Menu Introduction Homeostasis Immune/Inflammatory Response Genetics Stress Response Applicability to Practice Case Studies References

5. Pathophysiology of Surgical Site Infection Stress Response, Immune/Inflammation Response, Genetics, and Applicability to Practice Reviewed

6. Tutorial Overview • The body’s defense against severe infection following injury or trauma post surgical incision requires an intricate balance be maintained through specially designed protective physiological mechanisms. • Communication pathways between the nervous system and immune system that protect the body from infection post surgical incision are described.

7. Genetic factors influencing these regulatory physiological mechanisms and communication pathways are included. • Applicability of the pathophysiology of surgical site infection to surgical practice is explored.

8. Why Learn AboutSurgical Site Infection? • Complications resulting from surgical site infections continue to be a significant cause of morbidity and mortality among hospitalized patients. • The Centers for Disease Control and Prevention (CDC) monitor nosocomial infections using the National Nosocomial Infections Surveillance (NNIS) system established in 1970.

9. “Based on NNIS system reports, SSIs are the third most frequently reported nosocomial infection, accounting for 14% to 16% of all nosocomial infections among hospitalized patients” (Mangram et al, 1999, p. 251). • “Among surgical patients, SSIs were the most common nosocomial infection, accounting for 38% of all such infections”(Mangram et al, 1999, p. 251).

10. Hospital reporting of nosocomial conditions is now required by CMS. • In February, 2006 the Deficit Reduction Act of 2005 was enacted reducing hospital reimbursement from The Centers of Medicare and Medicaid Services (CMS) for hospital acquired conditions. • Beginning October 1, 2008, reimbursement for the treatment of nosocomial conditions acquired on and after admission will be discontinued.

11. Test Your Knowledge SSIs continue to be a significant cause of morbidity and mortality among hospitalized patients. SSIs are common nosocomial infections among surgical patients. Hospitals will continue to be reimbursed after October 1, 2008 for hospital acquired conditions. T F T F T F

12. Why is understanding the pathophysiology of surgical site infection important? • Understanding the pathophysiology of surgical site infection increases operating room personnel awareness of the importance of strict adherence to surgical techniques/interventions to achieve the best possible post operative outcomes.

13. The immune and inflammatory physiological processes are initiated post surgical incision to prevent infection. Immune/Inflammatory Responseof Surgical Site Infection

14. Sources of infection post surgical incision: • Endogenous • Most common cause of SSIs • Exogenous

15. Immune Response • There are two components of the immune response the body mobilizes as protective mechanisms against invading pathogens: • Natural immunity • Specific immunity

16. Components of natural immunity include: • leukocytes • granulocytes • neutrophils • eosinophils • basophils • monocytes/macrophages • natural killer cells • cytokines (IL-1B, IL-6, interferon-y, tumor necrosis factor-alpha, complement)

17. Components of Natural Immunity Leukocytes Natural Killer Cells Granulocytes Monocytes Neutrophils Macrophages Chemicals Cytokines Eosinophils Basophils

18. Natural immunity is the body’s primary defense against infection post surgical incision. • Cells involved in natural immunity are capable of attacking multiple invading pathogens within minutes to hours when challenged. Segerstrom and Miller (2004)

19. Granulocytes and monocytes comprise the largest group of immune cells involved in natural immunity. • Neutrophils and macrophages are phagocytic cells that flock to the site of injury or infection releasing toxic substances that kill invading pathogens. Segerstrom and Miller (2004)

20. Illustration Surgical Incision Macrophage Macrophage Neutrophil Neutrophil Pathogens

21. Neutrophils and macrophages then consume these invading pathogens through a mechanism known as phagocytosis. • In addition, macrophages release proinflammatory cytokines as a component of the inflammatory response described next.

22. Cytokine Macrophage, Neutrophil, & Leukocyte Pathogens

23. Test Your Knowledge Endogenous pathogens are the most common source of SSIs. • Click on some exogenous sources of invading pathogens: T F Patients Surgical Personnel Surgical Instruments Surgical Equipment

24. Specific immunity is activated post-surgical incision in immediate response to injury post surgical incision. Granulocytes and monocytes comprise the largest group of cells involved in natural immunity. T F T F

25. Neutrophils are granulocytes. Neutrophils and macrophages kill invading pathogens through a mechanism known as phagocytosis. T F T F

26. Inflammatory Response • The skin is a first line defense against infection. • When the skin barrier is injured, inflammation occurs as a result of the immune response to surgical incision.

27. Leukocyte trafficking occurs at the site of tissue injury post surgical incision initiating an inflammatory response. • Of the leukocyte cells moving into the site of tissue injury, macrophages are primarily responsible for initiating the inflammatory response. Viswanathan and Dhabhar (2005)

28. Macrophages release cytokines to regulate the inflammatory response of natural immunity post surgical incision. • Cytokines mediate the inflammatory response to tissue injury by responding to surface receptors on target cells and replicating the appropriate immune cell response accordingly. Desborough (2000)

29. Illustration Surgical Incision Pathogens Pathogens Cytokines Cytokines Neutrophil Neutrophil Macrophage Macrophage Cell Surface Receptors On Invading Pathogens

30. Test Your Knowledge The skin is a barrier to infection. Inflammation is a physiologic process that occurs after injury to the skin post surgical incision. T F T F

31. What are the most common cells of natural immunity regulating the inflammatory response to injury post surgical incision? Leukocytes Neutrophils Macrophages Cytokines

32. Stress Responseof Surgical Site Infection What is Stress? • In the 1930s an endocrinologist named Hans Seyle described stress as the body’s response to any form of noxious stimuli called stressors. Porth (2005)

33. Stressors is the term Hans Selye used to describe endogenous and exogenous events responsible for initiating the stress response. Endogenous stressorExogenous stressor anxiety surgical incision Porth (2005)

34. The stress response post surgical incision includes activation of the neuroendocrine control system. • The neuroendocrine control system is comprised of the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. Wilmore (2002)

35. Illustration Neuroendocrine Control System Sympathetic Nervous System Hypothalamic-Pituitary-Adrenal Axis

36. Sympathetic Nervous System • The SNS is activated as a result of psychological stress and injury to the body caused by the surgical incision. • When the SNS is activated, catecholamines are released into the blood stream.

37. The catecholamines released are: • epinephrine • norepinephrine • Catecholamines circulating in the blood stream increase sympathetic activity by attaching to adrenergic receptors located on cell surfaces within the body.

38. Different cell surface receptors account for different responses to neurotransmitters. • The adrenergic receptors include: • alpha 1 and beta 1 receptors • alpha 2 and beta 2 receptors

39. Alpha 1 and Beta 1 receptors are excitatory. • Alpha 2 and Beta 2 receptors are inhibitory. Click here to learn about specific adrenergic receptor responses. When you have finished viewing the adrenergic receptor slides, click on the button to return here.

40. Illustration Neuroendocrine Control System Sympathetic Nervous System Catecholamines Cell Cell Epinephrine Norepinephrine Cell Cell Bloodstream Adrenergic Receptors

41. Test Your Knowledge Anxiety is an endogenous stressor. Surgical incisions are exogenous stressors. The neuroendocrine control system regulates the stress response to endogenous and exogenous stressors. T F T F T F

42. The SNS and HPA axis comprise the neuroendocrine control system. The SNS releases cortisol into the bloodstream when the stress response is activated post surgical incision. T F T F

43. What catecholamines are released as a result of the stress response pre and post surgical incision? Epinephrine Norepinephrine Aldosterone Vasopressin

44. Catecholamines attach to alpha and beta receptors located on cell surfaces. • Which cell surface receptors are excitatory? T F Alpha 1 Alpha 2 Beta 1 Beta 2

45. Hypothalamic-Pituitary-Adrenal Axis • The stress response to surgical incision initiates the following sequence of events from the HPA axis: • The hormone corticotropin-releasing factor (CRF) is released into the portal system circulation. • CRF stimulates the release of adrenocorticotrophic hormone (ACTH). • ACTH stimulates the secretion of glucocorticoid hormones.

46. One of the most recognized glucocorticoid hormones released as a result of the stress response post surgical incision is cortisol. • Cortisol release maintains homeostasis through the following negative feedback mechanisms described next: • decreases immune/inflammatory response • increases stress response

47. Illustration Neuroendocrine Control System Sympathetic Nervous System Hypothalamic-Pituitary-Adrenal Axis Catecholamines Glucocorticoids CRF ACTH Epinephrine Norepinephrine Cortisol Bloodstream

48. What are the hormones released from the HPA axis during the stress response? Corticotropin ACTH Glucocorticoids Cortisol

49. Cortisol is a glucocorticoid hormone. Cortisol is a regulator of the immune/inflammatory and stress responses. T F T F

50. Homeostasis &Surgical Site Infection • The body’s normal state of homeostasis is threatened by the immune/inflammatory response to tissue injury post surgical incision. • Negative feedback mechanismsare initiated to maintain homeostasis.