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Flashcards in GI Deck (23)
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1

What are some pre-op considerations for GI disease?

  • Assessment of intravascular fluid volume and electrolyte concentration and nutrition
  • Often have GERD, bowel obs, vomiting, or hypersecretion of acid
  • Clotting abnormalities may need to be corrected b/c fat soluble vit K may be malabsorbed and is necessary for formation of factor II, VII, IX, X
  • Gastric lesions/resections often have iron deficiency anemia with megaloblastic vitamin B12 anemia
    • lack inrinsic factor or overgrowth of B12 consuming bacteria in blind loop

2

How can we control the amount of gastric contents?

  • ASA NPO guidelines
  • Increase gastric emptying with prokinetics (metoclopramide)
  • Reduce gastric volume and acidity with NG tube, nonparticulate, H2 antagonist, PPI
  • Cricoid pressure, cuffed ETT or proseal LMA

3

What factors can reduce LES tone?

  • volatile agents, TPL, propofol
  • opioids
  • anticholinergics
  • B-agonists
  • TCAs
  • Glucagon
  • cricoid pressure
  • obesity
  • hiatal hernia
  • pregnancy

4

What factors can increase LES tone?

  • anticholinesterases
  • acetylcholine
  • succinylcholine
  • alpha adrenergic agonists
  • antacids
  • reglan
  • serotonin
  • histamine
  • beta blockers

5

What is a hiatal hernia?

Anesthesia considerations?

  • Hiatal hernia- protrusion of portion of stomach through the hiatus of the diaphragm and thoracic cavity
  • Most pts do not have symptoms of reflux- LES integrity is more important
  • Aspiration precautions only indicated if pt is symptomatic!

6

What is the pathophysiology associated with a small bowel obstruction?

  • segment of bowel proximal to obstruction dilates and contains gas and fluids
  • there is an increase in small bowel secretion with a decrease in absorption
  • as bowel dilation increases fluid is lost into the bowel wall and peritoneal cavity
  • progressive dilation and edema of the bowel or of a volvulus may lead to impaired bowel supply with potential necrosis and perforation
  • after perforation further rapid fluid loss occurs and pt is at high risk of bacterial toxemia
  • hemoconcentration, hypovolemia, and hypokalemia
    • K is not only lost in gastric fluid (vomiting, diarrhea) but also secreted by kidney in response to the alkalosis

7

What happens with a large bowel obstruction?

competent vs incompetent ileocecal valve?

  • Slower, less dramatic presentation than small bowel
  • Competent iliocecal valve = closed obstruction, bowel dilation (right colon and cecum), with eventual impairment of blood supply, necrosis, and perforation
  • incompetent iliocecal valve = bowel contents reflux into small bowel leading to feculent vomiting
  • after perforation further rapid fluid loss occurs and pt is at high risk of bacterial toxemia

  • hemoconcentration, hypovolemia, and hypokale

8

What happens to fluid and electrolyte balance with a bowel obstruction?

  • Decreased intake- NPO, anorexia
  • 3rd spacing
    • sequestration of H2O, protein, and electrolytes into abdominal structures leads to ascites formation which leads to IBD and intestinal obstruction
  • Loss of fluids via NG tube, emesis, diarrhea, diuretics, fistula loses
  • Side effects of therapies
    • hypophosphatemia from parenteral nutrition
    • hyperkalemia or cardiac arrhythmias from too vigorous treatment of hypokalemia
    • CHF from too rapid or vigorous tx of hypovolemia

9

What are the goals when caring for a pt with a bowel obstruction?

  • Protect the airway
    • RSI ns awake vs pre-induction NG suction
  • restore vascular and interstitial volume
  • correct pH and electrolyte imbalance
  • normalize systemic vascular resistance
    • deficits corrected with a combination of balanced salt solution and colloid (protein losses)
    • maintenance D5 1/2NS with 20/40 mEq KCL
    • may need vasodilators

10

What are the parasympathetic effects on the GI tract?

How does our anesthetic affect this?

  • PSNS activity = increased bowel peristalsis
  • Cholinesterase inhibitors increase the frequency and magnitude of pressure waves in the colon, especially in diseased bowel
  • Atropine, glyco, and other anesthetics help reduce this effect
  • Anecdotal evidence that bowel anastomosis disruption occurs with neostigmine has never been verified experimentally

11

What is acute pancreatitis?

What are the symptoms?

  • Acute pancreatitis is pancreatic auto-digestion
    • associated with ETOH abuse and gallstones
    • hallmark = increased serum amylase
  • Symptoms:
    • excruciating mid-epigastric abd pain that radiates to back, relieved w/sitting
    • fluid deficit d/t N/V and GI bleed
    • ileus often develops
    • hypocalcemia with tetany
    • pleural effusions and ascites with dyspnea
    • fever and shock (50%)
    • ARDS (20%)
    • ARF (25%)

12

How is acute pancreatitis treated?

  • Aggressive IV fluid administration (up to 10 L)
  • NPO to "rest" the pancreas now being reconsidered- enteral nutrition is being started earlier
  • Opioids for severe pain
  • ERCP within 1st 24-72 hrs to remove gallstones

13

What do you often see in a pt with Crohn's disease?

  • Bowel obstruction- malnourished and dehydrated
  • Loss of fluids and nutrients through fistulae
  • often very ill on steroids and immunosuppressive therapy

14

What do you often see in a pt with Ulcerative colitis?

  • Electrolyte and fluid imbalances
  • Vit B12 and folate deficiency
  • assess for arthritis, iritis, and hepatitis
  • often come to OR to remove precancerous lesions, hemorrhage, bowel perforation, bowel obstruction, toxic megacolon
  • Often extensive operations; total colectomy or total proctocolectomy
  • steroids and immunosuppressive drugs

15

What are carcinoid tumors?

Where are they usually found?

Symptoms?

 

  • Tumors derived from enterochromaffin cells
    • can be found in any tissue with endoderm (esophagus to rectum)
    • most frequent site is appendix, but these rarely metastacis or produce carcinoid syndrome
    • tumors arising in the ileocecal region have the highest incidence of metastases
  • Usually asymptomatic- may have vague:
    • abdominal pain
    • diarrhea
    • intermittent intestinal obstruction 
    • GI bleeds

16

What do non-metastatic carcinoid tumors do?

  • secrete hormones that are transported to the liver through the portal vein where they are inactivated
  • most symptoms are related to hormones secreted into GI tract and systemic circulation
  • secrete a variety of hormones, mediators, and biogenic amines

17

What substances are secreted by carcinoid tumors?

  • serotonin (large quantities)
    • this increases platelet serotonin and metabolite 5-HIAA)
  • histamine
  • substance P
  • catecholamines (dopamine)
  • bradykinin
  • tachykinin
  • motilin
  • corticotrophin
  • prostaglandins
  • kallikrein

18

What is carcinoid syndrome?

  • 7-20% of pts with carcinoid tumor have carcinoid syndrome which usually means they have lung or liver metastasis
  • Symptoms depend on location of the tumor and the specific hormones produced and secreted
    • cutaneous flushing of neck, head, upper thorax (kinins, histamine)
    • Bronchoconstriction (serotonin, bradykinin, sub P)
    • Hyperglycemia (serotonin)
    • hypotension (kinins, histamine)
    • HTN (serotonin)
    • diarrhea (serotonin, prostaglandins)
    • carcinoid heart disease (serotonin)

19

What is Carcinoid heart disease?

  • Flushing + diarrhea + cardiac dysfunction = cardiac triad
  • usually right sided
    • tricuspid regurgitation is predominant
    • tricuspid stenosis and pulmonary valve regurgitation or stenosis can also occur
  • intramyocardial metastases and cardiac arrhythmias also seen

20

What should you do pre-operatively for a pt with a carcinoid syndrome?

  • Surgical excision is most effective tx
  • Octreotide- reduces release of vasoactive amines
    • carcinoid tumors have somatostatin receptors
    • Octreotide should be taken SQ starting 2 weeks prior to OR and weaned 1 week after
  • anxiolytics- stress/anxiety releases serotonin
  • H1 and H2 blocking drugs- block histamine release
    • avoid histamine releasing drugs (morphine, succ)
  • nebulized ipratropium bromide
  • steroids
  • monitor glucose, insulin gtt if necessary
  • arterial BP monitoring necessary- rapid hemodynamic changes
    • avoid vasoactive medications (NE, Epi, dopamine, isoproterenol) can provoke carcinoid crisis
  • CVP, PA catheter and TEE can also be considered especially with carcinoid heart disease

21

Anesthetic management of pt with carcinoid syndrome

  • Prevent carcinoid crisis with vasoactive and bronchoconstrictive consequences
    • stress
    • physical or chemical stimulation
    • manipulation of tumor
  • you want pt DEEP for DVL and ETT placement
  • Avoid histamine releasing drugs
  • all volatile agents acceptable
  • Regional
    • epidural better than spinal (slow titration to avoid hypotension)
    • treat with fluids and octreotide
  • Ondansetron (serotonin antagonist) is great antiemetic
  •  

22

How is carcinoid crisis treated intraoperatively?

  • Octreotide gtt for prevention 50-100 mcg/hr
  • Octreotide 25-100 mcg for hypotension or bronchospasm
  • Vasopressin for refractory hypotension
  • Aprotinin (kallikrein inhibitor)- 2nd line for hypotension
  • For HTN- labetalol or increase VA

23

Post-op management of pt with carcinoid syndrome

  • Secretion of vasoactive substances from residual tumor/metastasis and emotional and physical stress related release can still occur
    • intensive hemodynamic monitoring
    • Octreotide administration continued
    • effective post-op analgesia