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
2
Q
What physiological changes that occur during the stress response?
A
- hormonal
- metabolic
- immunologic
- hematological
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
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)
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
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
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
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
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
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
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
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
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
14
Q
What hormones increase during surgery?
A
- pituitary: GH, ACTH, Prolactin, ADH, B-endorphin
- adrenal: catecholamines, cortisol, and aldosterone
- pancreatic: glucagon
- renin
15
Q
What hormones decrease during surgery?
A
- insulin
- testosterone
- estrogen
- T3
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
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
Use of regional anesthesia?
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
Surgical technique used to modify stress response?
- decreased cytokine release in minimally invasive surgeries
27
Nutrition techniques used to modify the stress response?
- enteral feeding w/ glutamine, arginine, omega-3 fatty acids has been shown to improve recovery
28
Hormone therapy used to modify stress response?
- insulin infusions +/- glucose may reduce excess protein breakdown
29
Maintenance of normothermia use in surgery?
- reduces metabolic response to surgery
| body gets too cold - increase stress response
30
Relationship of surgery and length of surgery to stress response?
- magnitude and duration of stress response are directly proportional to extent of surgical injury
31
What is a dehiscence? RFs?
- 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
What is a evisceration?
- complete dehiscence of an abdominal wound can lead to evisceration where the abdominal organs are protuding out of the wound
33
What is cellulitis?
- an infection of the tissue just below the skin surface
34
What is gangrene? diff forms?
- 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
What is an abscess?
- 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
What is bacteremia? How can this occur?
- 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
What is septicemia?
- 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
What is SIRS?
- 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
PP of sepsis/SIRS?
- 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)
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The cause may include:
-direct effects of invading microorganisms or their toxic products
-release of large quantities of:
proinflammatory mediators
complement activation
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40
Coagulation that occurs in SIRS?
-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
Organ dysfxn in SIRS/Sepsis?
- 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
Parameters of SIRS?
- 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
