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Surgery > Physiologic Response to Surgery > Flashcards

Physiologic Response to Surgery Flashcards

1
Q

What is the stress response?

A
  • hormonal and metabolic changes that are triggered by stress
  • caused by surgery, trauma, burns, severe infection, extreme exercise
  • interplay of physiological, psychological and behavioral changes
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2
Q

What physiological changes that occur during the stress response?

A
  • hormonal
  • metabolic
  • immunologic
  • hematological
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3
Q

What are psychological and behavioral changes that occur during the stress response?

A
  • psych:
    fatigue, malaise, depression (esp after CV surgery)
  • behavioral: reluctance to move
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4
Q

Describe in general the hormonal response to stress?

A
  • begins w/ activation of HPA axis and the sympathetic nervous system
  • they receive afferent nerve input from the area of trauma or injury
  • normal feedback mechanism then fails (in stress response - have both elevated cortisol and ACTH)
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5
Q

Involvement of SNS in stress response?

A
  • catecholamines are released from the adrenal medulla
  • NE increases from the presynaptic nerve terminals
  • leads to tachycardia and HTN
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6
Q

Activation of SNS effect on pancreas, kidneys, and liver?

A
  • renal:
    renin release causes conversion of angiotensin I to II
    aldosterone release causing Na+ retention
  • pancreatic:
    glucagon release: breakdown glycogen into glucose, and also decreased insulin release and increased resistance
  • hepatic:
    glucagon from pancreas stimulates breakdown of glycogen in liver and muscle: increased glucose and lactate concentration: mobilization of free fatty acids from lipid stores
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7
Q

Fxns of pituitary gland?

A 
- anterior pituitary: 
controlled by hypothalamic releasing or inhibiting factors (CRF, GHRF)
ACTH, GH, prolactin 
- posterior pituitary:
directly controlled by hypothalamus, ADH
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8
Q

Pituitary changes during surgery?

A

Anterior:
-increased ACTH leads to increase release of cortisol and glucocorticoids from the adrenal medulla
-increased GH leds to increased blood sugar as it antagonizes insulin, GH may also have a positive role in wound healing
- increased prolactin due to decreased prolactin inhibiting factors
Posterior:
- hypothalamic input causes increased ADH which leads to further increase in ACTH

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9
Q

What happens to cortisol during surgery?

A
  • begins to increase rapidly following the start of surgery
  • release stimulated by ACTH
  • max increase in 4-6 hrs
  • levels may increase 3-4x normal
  • usually increasd cortisol levels cause a decrease in secretion of ACTH but during and after surgery this feedback mechanism doesn’t work and both ACTH and cortisol remain high
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10
Q

Fxn of cortisol?

A
  • promotion of protein breakdown and gluconeogenesis
  • inhibits glucose use by cells and increases blood glucose
  • promotes lipolysis leading to further increases in blood glucose
  • has glucocorticoid anti-inflammatory effects
  • has mineralocorticoid effects causing fluid retention and K+ loss
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11
Q

What happens to insulin during surgery?

A
  • key anabolic hormone
  • synthesized and secreted from pancreas
  • promotes uptake of glucose into muscle and adipose tissue
  • converts glucose into glycogen and triglycerides
  • inhibits protein catabolism and lipolysis
  • concentration decreases after induction of anesthesia and during trauma by inhibition of Beta cells in pancreas by alpha-2-adrenergic effects of catecholamines
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12
Q

What happens to glucagon during surgery?

A
  • produced by alpha cells of the pancreas
  • promotes hepatic glycogenolysis
  • increases gluconeogensis from amino acids in the liver
  • has lipolytic activity
  • transient increase but doesn’t contribute much to hyperglycemic response
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13
Q

What happens to thyroid hormones during surgery?

A
  • total and free T3 decrease after surgery and return to normal after several days
  • TSH concentrations decrease after the 1st 2 hrs then return to normal
  • unaltered or decreased secretion in surgery
  • changes related to catecholamines and cortisol
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14
Q

What hormones increase during surgery?

A
  • pituitary: GH, ACTH, Prolactin, ADH, B-endorphin
  • adrenal: catecholamines, cortisol, and aldosterone
  • pancreatic: glucagon
  • renin
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15
Q

What hormones decrease during surgery?

A
  • insulin
  • testosterone
  • estrogen
  • T3
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16
Q

How is carbohydrate metabolism altered in surgery?

A
  • glucose homeostasis mechanisms are ineffective in the perioperative period
  • catabolic hormones promote glucose production and there is lack of insulin and peripheral insulin resistance:
  • cortisol and catecholamines
  • growth hormone
  • degree of hyperglycemia is relative to severity of surgery
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17
Q

What can hyperglycemia lead to after surgery?

A
  • risks of prolonged perioperative hyperglycemia:
    wound infection
    impaired wound healing
18
Q

How does protein metabolism change in surgery?

A

increased cortisol and cytokine concentration:

  • promotes catabolism
  • primarily skeletal muscle breakdown
  • some visceral muscle may also be catabolized for essential amino acids
  • these may be used by liver for energy or to make new proteins, like acute-phase proteins
  • albumin production is reduced and alters extracellular volume
  • leads to wt loss and muscle wasting: up to 0.5kg/day of muscle loss post major abdominal surgery
  • can indirectly measure degree of protein loss by nitrogen excretion in the urine
19
Q

How does lipid metabolism change during surgery?

A

lipolysis and ketone production:

  • due to increased catecholamines, cortisol, and glucagon secretion, and insulin deficiency
  • triglycerides are metabolized to free fatty acids and glycerol
  • free fatty acids are oxidized to acyl CoA in setting of high glucagon and low insulin: convertd to B-hydroxybutyrate, acetoacetate and acetone DKA)
20
Q

How does water and electrolyte metabolism change during surgery?

A

ADH:
- promotes water retention and concentrated urine, increased secretion for 3-5 days post op
Renin:
- released from juxtaglomerular cells of the kidney
- stim production of angiotensin II:
stimulates the releas of aldosterone from the adrenal cortex
Na+ and H2O resorption at DCT
K+ loss

21
Q

Cytokine release during surgery? Most impt cytokine? What is cytokine production limited by?

A
  • interleukins (1-17) and interferons, tumor necrosis factor
  • produced from activated macrophages, fibroblasts, endothelial and glial cells: response to tissue injury from surgery or trauma
  • mediators of immunity and inflammation
  • interleukin 6: most impt cytokine assoc w/ surgery
  • concentration peaks 12-24 h post surgery: degree of elevation depends on degree of tissue damage
  • IL-6 and other cytokines cause acute phase response
  • IL-6 and other cytokines cause the acute phase response: porduction of acute phase proteins - fibrinogen, CRP, complement, alpha-2-macroglobulin, amyloid A and ceruloplasmin
  • other effects: fever, agranulocytosis, hemostasis, tissue damage limitation, and promotion of healing
  • cytokine production is limited by cortisol - negative feedback
22
Q

Components of acute phase response?

A
  • systemic: fever, changes in vascular perm
  • bone marrow: increased neutrophils
  • liver produces acute phase proteins: CRP, fibrinogen, alpha-2-macroglobulin, coagulation proteins
  • transport proteins: increase in ceruloplasmin, decrease in transferrin, allbumin, and alpha-2-macroglobulin
  • changes in serum concentration of cations: copper increases and zinc and iron decrease
23
Q

How does opioids affect the stress response of surgery?

A
  • can suppress hypothalmic and pituitary hormone secretion
    ex: fentanyl and morphine
  • hormonal response to pelvic and abdominal surgery can be suppressed:
    high dose fentanyl
    -the down side: prolong recovery and increase need for post-op ventilatory support
24
Q

Anesthetic drugs used in surgery?

A
  • etomidate: suppresses cortisol production
  • benzodiazepines: may inhibit steroid production at level of pituitary
  • clonidine: inhibit stress responses mediated by SNS
25
Q

Use of regional anesthesia?

A

AKA: epidural/spinal anesthesia:
- can reduce glucose, ACTH, cortisol, GH and epi changes
- cytokine responses are unaltered
regional anesthesia can provide:
excellent analgesia, reduced thromboembolic complications, improved pulm. fxn and reduced paralytic ileus (general anesthesia: puts bowel to sleep, effects ciliary transport in lungs)

26
Q

Surgical technique used to modify stress response?

A
  • decreased cytokine release in minimally invasive surgeries
27
Q

Nutrition techniques used to modify the stress response?

A
  • enteral feeding w/ glutamine, arginine, omega-3 fatty acids has been shown to improve recovery
28
Q

Hormone therapy used to modify stress response?

A
  • insulin infusions +/- glucose may reduce excess protein breakdown
29
Q

Maintenance of normothermia use in surgery?

A
  • reduces metabolic response to surgery

body gets too cold - increase stress response

30
Q

Relationship of surgery and length of surgery to stress response?

A
  • magnitude and duration of stress response are directly proportional to extent of surgical injury
31
Q

What is a dehiscence? RFs?

A
  • wound rupture along surgical suture
  • RFs:
    pt: age, obesity, diabetes, smoking, steroids
    surgical technique: poor knot tying or closure techniques, excessive tension
    wound: trauma or infection
32
Q

What is a evisceration?

A
  • complete dehiscence of an abdominal wound can lead to evisceration where the abdominal organs are protuding out of the wound
33
Q

What is cellulitis?

A
  • an infection of the tissue just below the skin surface
34
Q

What is gangrene? diff forms?

A
  • necrosis of tissue occurs due to lack of adequate vascular supply or infection
    forms of gangrene:
    -wet: tissue infected, swollen, fetid smell
    -dry: ischemia w/o infection
    -gas: bacterial infection thta produces gas in the tissues (Clostridium perfringens)
  • other: necrotizing fasciitis, spreads deep along tissue planes
35
Q

What is an abscess?

A
  • collection of pus built up w/in the body tissue
  • usually caused by bacterial infection but can also be sterile (irritant from injection)
  • painful, tender, fluctuant, and erythematous nodule
  • frequently assoc w/ pustula nd surrounded by rim of erythematous swelling
36
Q

What is bacteremia? How can this occur?

A
  • presence of bacteria in the blood
    bacteria can enter bloodstream:
    -from complications of infections (Like pneumonia or meningitis)
  • during surgery (esp when involving mucous membranes such as GI tract)
  • due to catheters and other fbs entering the arteries or veins (including during IV drug abuse)
37
Q

What is septicemia?

A
  • bacteremia that often occurs w/ severe infections (systemic signs and sxs w/ organ failure)
  • aka bacteremia w/ sepsis
  • serious life-threatening infection that gets worse very quickly
38
Q

What is SIRS?

A
  • clinical syndrome identical to sepsis characterized by dysregulation of inflammation but unlike sepsis can be caused by an infecitous or noninfectious etiology
  • ex of noninfectious etiologies: autoimmune disorder, pancreatitis, vasculitis, thromboembolism, burns or surgery
  • early sepsis and SIRS are indistinguishable
  • SIRS is defined as 2 or more abnormalities in temp, HR, respiration, or WBC count
39
Q

PP of sepsis/SIRS?

A
  • release of proinflammatory mediators in response to infection (or other tissue insult) exceeds the boundaries of the local enviro, leading to a more generalized response (abnormal response to trauma, inflammation or infection - leads to inflammatory cascade - which leads to excessive proinflammatory activation followed by excessive release of antiinflammatory mediators)
The cause may include:
-direct effects of invading microorganisms or their toxic products
-release of large quantities of:
proinflammatory mediators
complement activation
40
Q

Coagulation that occurs in SIRS?

A

-cytokines IL-1 and TNF-alpha:
affect endothelial surfaces
also causes decreased fibrinolysis
- resulting in expression of tissue factor
- tissue factor initiates production of thrombin and promotes coagulation
- microvascular thrombosis then occurs (this leads to organ damage)

41
Q

Organ dysfxn in SIRS/Sepsis?

A
  • occurs as a result of:
    cellular injury
    microvascular thrombosis
    release of proinflammatory and antiinflammatory mediators
  • all organ systems may be affected:
    MC involved include the circulation, lung, GI tract, kidney and nervous system
42
Q

Parameters of SIRS?

A
  • temp: greater than 38C or less than 36C
  • HR: greater than 90
  • SBP: less than 90 or down 40 from baseline
  • RR: greater than 20
  • labs: less than 100,000 platelets
  • acute rise in bili (total over 4)
  • GI: ileus
  • Cr: rise of 0.5
  • lactate: ischemic tissues, arterial hypoxemia
  • increase in CRP, procalcitonin
  • WBC greater than 12,000 or less than 4,000
  • increased blood gluocse
  • sig edema
  • alterd mental status

Surgery (19 decks)

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