GI

Question 1

What are some pre-op considerations for GI disease?

Answer 1

• 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

Question 2

How can we control the amount of gastric contents?

Answer 2

• 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

Question 3

What factors can reduce LES tone?

Answer 3

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

Question 4

What factors can increase LES tone?

Answer 4

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

Question 5

What is a hiatal hernia?

Anesthesia considerations?

Answer 5

• 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!

Question 6

What is the pathophysiology associated with a small bowel obstruction?

Answer 6

• 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

Question 7

What happens with a large bowel obstruction?

competent vs incompetent ileocecal valve?

Answer 7

• 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

Question 8

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

Answer 8

• 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

Question 9

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

Answer 9

• 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

Question 10

What are the parasympathetic effects on the GI tract?

How does our anesthetic affect this?

Answer 10

• 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

Question 11

What is acute pancreatitis?

What are the symptoms?

Answer 11

• 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%)

Question 12

How is acute pancreatitis treated?

Answer 12

• 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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

• 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

Question 15

What are carcinoid tumors?

Where are they usually found?

Symptoms?

Answer 15

• 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

Question 16

What do non-metastatic carcinoid tumors do?

Answer 16

• 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

Question 17

What substances are secreted by carcinoid tumors?

Answer 17

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

Question 18

What is carcinoid syndrome?

Answer 18

• 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)

Question 19

What is Carcinoid heart disease?

Answer 19

• 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

Question 20

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

Answer 20

• 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

Question 21

Anesthetic management of pt with carcinoid syndrome

Answer 21

• 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
  *

Question 22

How is carcinoid crisis treated intraoperatively?

Answer 22

• 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

Question 23

Post-op management of pt with carcinoid syndrome

Answer 23

• 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