GI (4) Flashcards
The GI tract constitutes approx ____% of total body mass
5%
What are the main functions of GI system?
- Motility
- Digestion
- Absorption
- Excretion
- Circulation
List GI layers from outer most to inner most:
- serosa
- longitudinal muscle layer
- circular muscle layer
- submucosa
- mucosa
What layers are in the mucosa? (List from outer to inner layer)
- muscularis mucosae
- lamina propria
- epithelium
Which muscle layer contracts to shorten the length of the intestinal segment?
Longitudinal muscle layer
Which muscle layer contracts to decreases the diameter of the intestinal lumen?
Circular muscle layer
Longitudinal and circular muscle layer work together to propagate _______ motility
gut
What is the mucosa composed of?
- Muscularis mucosa: function to move the villi
- Lamina propria: contains blood vessels, nerveendings, and immunecells
- Epithelium: GI contents are sensed, enzymes are secreted,and nutrients are absorbed
The GI tract is innervated by the _____________ nervous system.
Autonomic
What does the GI ANS consist of?
- Extrinsic nervous system
- Enteric nervous system
What is the function of the extrinsic nervous system?
- PNS and SNS
- SNS is inhibitory and decreases motility
- PNS is excitatory and activates motility
What is the function of the enteric nervous system?
- Independent nervous system
- Controls motility, secretions, and blood flow
- myenteric plexus and submucosal plexus
What does the celiac plexus innervate?
Innervates the proximal GI organs to the transverse colon
Hypogastric plexus innervates:
Descending colon and distal GI tract
What approaches can be used to block the celiac plexus?
- Trans-crural
- Intraoperative
- Endoscopic ultrasound-guided
- Peritoneallavage
_________ plexus lies between the smooth muscle layers and regulates the smooth muscle
Myenteric
__________ plexus transmits info from the epithelium to the enteric and central nervous systems
Submucosal
What is the enteric system composed of?
- Myenteric plexus
- Submucosal plexus
Both of these plexus respond to SNS and PNS stimulation
What is the function of myenteric plexus?
Controls motility→ enteric neuron, interstitial cells of Cajal (aka ICC cells, GI pacemakers), and smooth muscle cells
What is the function of the submucosal plexus?
- absorption
- secretion
- mucosal blood flow
What are anesthesia challenges involved with upper endoscopy?
- Sharing airway with endoscopist
- Usually done without ETT, must closely manage airway
- Procedure performed outside of the main OR (limited equipment & supplies
What are anesthesia challenges with colonoscopy?
Pt dehydration from bowel prep/NPO status
Functions of the stomach:
- Reservoir for food
- Mixes and breaks fown food to form chyme
- Empties into the small intestine
What is the purpose of GI barium swallow test?
Radiologic assessment of swallow function and GI transit
What is the gastric emptying study?
Pt fasts for >4 hours then consumes a meal with a radiotracer (frequent imaging for the next 1-2 hours)
How small must solids be broken down before entering the duodenum?
1-2 mm
What is the motility of the stomach controlled by?
Intrinsic and extrinsic neural regulation
What is small intestine manometry?
- Catheter that measures contraction pressures and motility of the small intestine
- Eval contraction during 3 periods (Fasting, during meal, and post prandial)
- Abnormal results are grouped into myopathic and neuropathic
PNS stimulates the ____ nerve to increase the number and force of ____:
Vagus; contractions
SNS stimulation to the ____ nerve ____ these contractions
splanchnic; inhibits
What is a lower GI series for?
Barium enema outlines the intestine so its visible on radiograph (allows for detection of colon/rectal abnormalities)
How does neurohormonal control modulate GI movement?
- Gastrin & motilin increase the strength and frequency of contractions
- Gastric inhibitory peptide inhibits contractions
How are diseases of the esophagus grouped?
- Anatomical
- Mechanical
- Neurologic
Many disease states overlap
What diseases are included in anatomical esophageal diseases?
- Diverticula
- Hiatal hernia
- Chronic acid reflux changes
What is the most common cause of non-variceal upper GI bleeding?
Peptic ulcer disease
What is the lifetime prevalence of peptic ulcer disease in men and women?
10% women
12% men
How many deaths per year occur d/t peptic ulcer disease?
15,000
What diseases are included in mechanical esophageal diseases?
- Achalasia
- Esophageal spasms
- hypertensive LES
Peptic ulcer disease may be associated with ____ ____
Helicobacter pylori
Symptoms of peptic ulcer disease:
- Burning epigastric pain exacerbated with fasting and improved with meals
___% risk of perforation in those who do not receive treatment for peptic ulcer disease
10%
What diseases are included in neurologic esophageal diseases?
- Neuro disorders (stroke)
- Vagotomy
- Hormone deficiencies
Symptoms of perforation with PUD:
Sudden/severe epigastric pain caused by acidic secretions into peritoneum
Mortality in PUD is due to shock or perforation >___
> 48 hours
What are the most common S/S of esophageal disease?
- Dysphagia
- Heartburn
- GERD
What causes acute gastric outlet obstructions?
Acute obstructions caused by edema and inflammation in pyloric channel at the beginning of duodenum
- Onset may be acute or slow
What is dysphagia?
Difficulty swallowing (may be oropharyngeal or esophageal)
When is oropharyngeal dysphagia common to occur?
After head/neck surgeries
What causes chronic gastric outlet obstruction?
Chronic obstructions or stenosis can be caused by repetitive ulceration and scarring
How is esophageal dysphagia classified?
- Esophageal dysmotility: symptoms occur with liquids and solids
- Mechanical esophageal dysphagia: symptoms only with solid food
What happens with gastroesophageal reflex disease?
Effortless return of gastric contents into pharynx
(heartburn, nausea, “lump in throat”)
Treatment for gastric ulcers:
H2 blockers, PPIs, prostaglandin analogues, cytoprotective agents
5 types of gastric ulcers are normally caused by what??
NSAIDs, H. Pylori, ETOH
Neuromuscular disorder of the esophagus creating an outflow obstruction d/t inadequate LES tone and a dilated hypomobile esophagus:
Achalasia
Treatment for H. Pylori gastric ulcers:
Triple therapy - (2 abx +PPI) x 14 days
What causes achalasia?
- loss of ganglionic cells of the esophageal myenteric plexus
- absence of LES inhibitory neurotransmitters
- LES cant relax (unopposed cholinergic stimulation)
- Esophageal dilation with food unable to move forward
5 types of gastric ulcers:
What is Zollinger Ellison syndrome?
Non B cell pancreatic tumor (gastrinoma) that causes hypersecretion of gastrin
What are S/S of esophageal disease?
- dysphagia
- regurgitation
- heartburn
- chest pain
What is absent in zollinger ellison syndrome?
The negative feedback look where gastrin stimulates gastric acid secretion, and gastric acid normally inhibits further gastrin release
What is long term achalasia associated with?
Increased risk of esophageal cancer
How is Achalasia diagnosed?
Esophageal manometry and/or esophagram
Symptoms of zollinger ellison syndrome:
- Peptic ulcer disease
- Erosive esophagitis
- Diarrhea
What are the 3 classes of achalasia?
- Type 1: minimal esophageal pressure, responds well to myotomy
- Type 2: entire esophagus pressurized; responds well to treatment, has best outcomes
- Type 3: esophageal spasms w/premature contractions; has worst outcomes
Prevalence of zollinger ellison syndrome:
- Occurs in 0.1-1% of PUD patients
- M>F
- most commonly between ages 30-50
What are treatment options for achalasia?
All treatments are palliative
- Meds: nitrates/CCB to relax LES
- Endoscopic botox injections
- Pneumatic dilation
- Laparoscopic hellar myotomy
- peri-oral endoscopic myotomy (PEOM)
- Esophagectomy
Up to ___% of patients with ____ are metastatic at time of diagnosis
50%; gastrinomas
What is the most effective non-surgical treatment for achalasia?
Pneumatic Dilation
What is the best surgical treatment for achalasia treatment?
Laparoscopic Hellar myotomy
Treatment for ZES:
- PPIs
- Surgical resection of gastrinoma
Considerations for patients with ZES:
- Increased gastric volume (RSI these patients)
- Electrolyte imbalances
- Endocrine abnormalities
Preop considerations for ZES:
- Correct electrolytes
- increase gastric pH with meds
- RSI
Functions of the small intestine:
- Motility mixes the nutrients with digestive enzymes, further reducing particle size and increasing solubility
- Major function is to circulate contents and expose them to the mucosal wall to maximize absorption
What are anesthesia considerations for patients with Achalasia?
- increase risk for aspiration
- RSI or awake intubation indicated
Where do most esophageal spasms occur? What causes them?
Spasms that usually occur in distal esophagus likely from autonomic dysfunction
Esophageal spasms are more common in __________
Elderly
How are esophageal spasms diagnosed?
Esophagram
In the small intestine, the ____ and ____ muscle layers coordinate to achieve ____
Circular and longitudinal; achieve segmentation
Pain from esophageal spasm mimics_______
Angina
What are treatments for esophageal spasms?
- Nitro
- antidepressants
- phosphodiesterase inhibs
What is esophageal diverticula?
- Outpouchings in the wall of the esophagus
- Increases risk for aspiration: need to remove particles and RSI
What are different types of esophageal diverticula?
- Pharyngoesophageal (Zenker diverticulum): bad breath d/t food retention
- Midesophageal: may be caused by old adhesions or inflamed lymph nodes
- Epiphrenic (supradiaphragmatic): pts may experience achalasia
What is segmentation in the small intestine?
Occurs when two nearby areas contract and isolate a segment to hold the contents in place long enough to be absorbed into the circulation
What is segmentation in the small intestine controlled by?
What about motility?
The enteric nervous system with motility controlled by the extrinsic nervous system
What is a hiatal hernia?
- Herniation of stomach into thoracic cavity, occurs through the esophageal hiatus in the diaphragm
- Weakening in connective tissues that anchor the GE junction to the diaphragm
- May be asymptomatic often have GERD
Reversible causes of small bowel dysmotility:
- mechanical obstruction such as hernias, malignancy, adhesions, volvuluses
- bacterial overgrowth leading to alterations in absorptive function
- ileus, electrolyte abnormalities and critical illness
________: 100,000 people in the US Have esophageal cancer
4-5
How does esophageal cancer present?
Progressive dysphagia and weight loss
Nonreversible causes of small bowel dysmotility can be classified as what two types?
Structural or neuropathic
Why is esophageal cancer survival rate poor? Where are most of these cancers located?
- Abundant lymphatics leads to lymph node metastasis
- Most are adenocarcinomas in the lower esophagus (related to GERD, Barretts, obesity)
What are structural causes of small bowel dysmotility?
- Scleroderma
- Connective tissue disorders
- IBD
What are the 2 different types of esophageal cancers?
- Adenocarcinomas (Most common)
- Squamous cell carcinoma
What can be done for esophageal cancer to cure or palliative care?
Transthoracic, transhiatal, or minimally invasive Esophagectomy
What is high risk associated with esophagectomy?
Recurrent laryngeal nerve injury (40% resolve spontaneously)
Post esophagectomy patients are high risk for ___________ for life
aspiration
What are neuropathic causes of small bowel dysmotility?
Pseudo-obstruction caused by intrinsic and extrinsic nervous system dysfunction
- only produce weak, uncoordinated contractions
- leads to bloating, nausea, vomiting, abdominal pain
What causes GERD?
Incompetence of the gastro-esophageal junction, leading to reflux
What are S/S of GERD? What percent of adults have GERD?
- Heartburn
- Dysphagia
- Mucosal injury
15% of adults
What does GERD reflux contents include?
- HCl
- Pepsin
- Pacreatic enzymes
- Bile
Functions of the large intestine:
- Reservoir for waste and indigestible material before elimination
- extracts remaining electrolytes and water
Bile reflux is associated with ___________ __________ and adenocarcinoma
Barrett metaplasia
The colon also exhibits giant ____ ____
migrating complexes
What 3 mechanisms cause gastro-esophageal incompetence?
- Transient LES relaxation from gastric distention
- LES hypotension
- Autonomic dysfunction of GE junction
What are giant migrating complexes for in the large intestine?
How often do they occur?
Serve to produce mass movements across the large intestine
In a healthy state, they occur approx. 6-10x/day
What are the two primary symptoms of colonic dysmotility?
- altered bowel habits
- intermittent cramping
What is normal LES pressure? What is LES pressure with GERD?
Norm: 29mmHg
GERD: 13mmHg
Treatments for GERD:
- Avoidance of trigger foods
- Meds: Antacids, H2 blockers, PPIs
- Surgery: Nissen Fundoplication, Toupet, LINX
What are some preop interventions for patients with GERD?
- Cimetidine, Ranitidine-↓acid secretion & ↑ gastric pH
- PPI’s generally given night before and morning of
- Sodium Citrate- PO nonparticulate antacid
- Metoclopramide
- Aspiration precautions (RSI)
What are the most common diseases associated with colonic dysmotility?
IBS and IBD
What can happen if you have increased frequency of giant migrating complexes?
Further compresses the inflamed mucosa, which can lead to significant erosions and hemorrhage
Which patients usually get reglan in preop?
- Diabetics (gastroparesis)
- Obese
- Pregnant
reglan= gastrokinetic
In IBD, contractions are suppressed due to ____, but the giant migrating complexes ____
inflammation; remain
What is the 2nd most common inflammatory disorder after RA?
Inflammatory bowel disease
What is the incidence of IBD?
18:100,000 people
What are factors that increase intraop aspiration risk?
- Emergent surgery
- Full Stomach
- Difficult airway
- Inadequate anesthesia depth
- Lithotomy
- Autonomic Neuropathy
- Gastroparesis
- DM
- Pregnancy
- ↑ Intraabdominal pressure
- Severe Illness
- Morbid Obesity
What is ulcerative colitis?
Mucosal disease of part or all of the colon
What can occur in severe cases of ulcerative colitis?
The mucosa can be hemorrhagic, edematous and ulcerated
Symptoms of IBD:
- Diarrhea
- Rectal bleeding
- Crampy abdominal pain
- N/V
- Fever
- Weight loss
Lab values for IBD:
-↑plts
-↑erythrocyte sedimentation rate
- decreased H&H
- decreased albumin
What warrants surgical colectomy?
Hemorrhage requiring 6+ units of blood in 24-48 hours
What triggers toxic megacolon?
Electrolyte disturbances
How many cases of toxic megacolon resolve?
about 1/2 resolve and 1/2 require colectomy
Mortality rate of colon perforation:
15%
What part of the bowel does Crohn’s disease affect?
Acute or chronic inflammatory process that may affect any/all of the bowel
What is the most common site for Crohn’s and how does it present?
Terminal ileum; presents with ileocolitis, RLQ and diarrhea
Symptoms for Crohn’s disease:
- Weight loss
- Fear of eating
- Anorexia
- Diarrhea
In Crohn’s, persistent inflammation gradually progresses to what?
Fibrous narrowing and stricture formation
In Crohn’s extensive inflammation leads to what?
Loss of absorptive surfaces, resulting in malabsorption
1/3 of Crohn’s patients have additional symptoms of what?
- Arthritis
- Dermatitis
- Kidney stones
In Crohn’s, diarrhea decreases and is replaced by what?
Chronic bowel obstruction
Medical treatment for IBD:
- 5-acetylsalicyclic acid (mainstay for IBD)
- PO/IV glucocorticoids during flares
- Antibiotics: Rifaximin, flagyl, cipro
- Purine analogues
Surgery considerations for IBD treatment:
- Last resort - resected segment should be as conservative as possible
- small intestine resection should be limited to <1/2 length
>2/3 resection leads to “short bowel syndrome” - requiring TPN
Where do 95% of carcinoid tumors originate from?
GI tract
(but may occur in any area of GI tissue)
What do carcinoid tumors secrete?
Peptides and vasoactive substances
- Gastrin, insulin, somatostatin, motilin, neurotensin, tachykinins, glucagon, serotonin, other biological actives
Carcinoid syndroms occurs in ___ of patients with carcinoid tumors
10%
Symptoms of carcinoid tumors:
- Flushing
- Diarrhea
- HTN/HoTN
- Bronchoconstriction
- May acquire right heard endocardial fibrosis
- Left heart generally more protected as the lungs clear some of the vasoactive substances
What is carcinoid syndrome?
When large amounts of serotonin and vasoactive substances reach systemic circulation
Diagnosis of carcinoid syndrome:
- Urinary or plasma serotonin levels
- CT/MRI
Treatment for carcinoid syndrome:
- Avoid serotonin-triggers
- Serotonin antagonists
- Somatostatin analogues
Preop considerations for carcinoid syndrome:
Octreotide before surgery and prior to tumor manipulation to attenuate volatile hemodynamic changes
Incidence of acute pancreatitis:
Incidence has increased 10 fold since 1960s
- likely due to↑alcoholism along with better diagnostics
Pancreas contains numerous ____:
Digestive enzymes
What is autodigestion normally prevented by?
- Proteases packaged in precursor form
- Proteases inhibitors
- Low intra-pancreatic calcium, which decreases trypsin activity
*failure of any of these mechanisms can trigger pancreatitis
What are the most common causes of acute pancreatitis?
Gallstones and alcohol abuse (60-80%)
How do gallstones cause acute pancreatitis?
Obstruct ampulla of vater, causing pancreatic ductal HTN
Pancreatitis is also seen in what patients?
- Immunodeficiency syndrome
- Hyperparathyroidism
-↑Ca++
Symptoms of acute pancreatitis:
- Excruciating epigastric pain that radiates to back
- N/V
- abdominal distention
- steatorrhea
- ileus
- fever
- tachycardia
- HoTN
Hallmark labs of acute pancreatitis:
Increased serum amylase and lipase
Imaging for acute pancreatitis:
- Contrast CT or MRI,
- endoscopic US
What are the complications of acute pancreatitis?
25% experience serious complications such as shock, ARDS, renal failure, necrotic pancreatic abscess
Treatment for acute pancreatitis:
- Aggressive IVF
- NPO to rest pancreas
- Enteral feeding (over TPN)
- Opioids
Why is enteral feeding preferred over TPN in patients with acute pancreatitis?
TPN is associated with greater risk of infectious complications
What is the purpose of an ERCP with acute pancreatitis?
- Fluoroscopic examination of biliary and pancreatic ducts
- Interventions include stone removal, stent placement, sphincterotomy, hemostasis
Is upper or lower GI bleeding more common?
Upper
In upper GI bleeds, ___% of blood loss will lead to HoTN and tachycardia
> 25%
Orthostatic HoTN normally indicates HCT ____?
<30%
What does melena indicate?
bleed is above the cecum (where SI meets colon)
What are BUN values for upper GI bleeding and why?
> 40 mg/dL due to absorbed nitrogen into bloodstream
What is the diagnostic procedure of choice for upper GI bleeding?
EGD
- endoscopic ulcer ligation
- ligation of bleeding varices
What is the last resort for uncontrolled variceal bleeding?
Mechanical balloon tamponade
Causes of lower GI bleeding:
- Diverticulosis
- Tumors
- Colitis
For lower GI bleeds, what can be performed when hemodynamically stable?
Unprepped sigmoidoscopy
What does persistent lower GI bleeding warrant?
Angiography and embolic therapy
What is an ileus?
- Characterized by massive dilation of the colon without mechanical obstruction
- loss of peristalsis leads to distention of the colon
What can cause an ileus?
- Electrolyte disorders
- Immobility
- Excessive narcotics
- Anticholinergics
Ileus are also thought to be due to what imbalance?
Neural-input imbalance of excessive SNS stimulation along with inadequate PNS input to the colon
Treatment for ileus:
- Restore electrolyte imbalance
- Hydrate
- Mobilize
- NG suction
- Enemas
What medication can produce immediate results in 80-90% of ileus?
Neostigmine 2-2.5 mg over 5 minutes
*cardiac monitoring required
If an ileus is left untreated, what may happen?
Ischemia and perforation
In preop, patients are often nervous and ____ charged:
Sympathetically
What happens to the GI system when you’re anxious in preop?
Inhibition of GI activity is directly proportional to the amount of norepinephrine secreted from SNS stimulation
*higher anxiety = higher GI inhibition
What do volatile anesthetics depress in the GI system?
Electrical, contractile and propulsive GI activity
What is the first part of the GI tract to recover?
The small intestine
When does the stomach and colon recover postop?
Stomach = 24 hours
Colon = 30-40 hours
Volatile agents coupled with what can inhibit GI function and motility?
SNS hyperactivity associated with surgery
Nitrous oxide is __x more soluble than ___ in the blood and will diffuse into gas containing cavities
30x more soluble than nitrogen - will diffuse out of the blood faster than nitrogen
When giving nitrous, GI distention correlates with what?
The pre-existing amount of gas in the bowel, as well as the duration and concentration of nitrous administered
When should nitrous be avoided?
Lengthy abdominal surgeries or when the bowel is already distended
Do NMBDs affect GI motility?
NO - only skeletal muscle, so the GI motility remains intact
How does neostigmine increase bowel peristalsis?
Increasing frequency and intensity of contractions
Why is an anticholinergic often given with neostigmine?
To counteract the bradycardia associated with neostigmine
Does sugammadex affect GI motility?
NO
Opioids are known to cause what??
reduced GI motility and constipation
What receptors do opioids stimulate?
Mu, Delta, Kappa
Where is there a high density of peripheral mu-opioid receptors?
Myenteric and submucosal plexuses
What is caused by activation of mu-receptors?
Delayed gastric emptying and slower GI transit
What are some other adverse effects of anesthesia on the GI system?
- Nausea
- Anorexia
- Delayed digestion
- Abdominal pain
- Constipation
