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Nursing School

GI System Outline
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GI System


A&P:  Esophagus – food enters the upper esophagus & passes thru the upper esophageal sphincter.  Food is pushed along by peristaltic waves – these waves are produced by contractions of underlying smooth muscle.  A muscular sphincter prevents food from refluxing up the esophagus into the trachea.  The lower sphincter is a pressure sphincter.  The pressure in the stomach is lower than the pressure in the esophagus. Gas from fatty foods (& nicotine) increase the pressure in the stomach which causes reflux. 


Meds given for pressure:  Antacids-they decrease the stomach’s pressure by neutralizing, buffering & absorbing the stomach acid.


Stomach – Food is stored and broken down for digestion & absorption here.

HCL, mucus, the enzyme pepsin, and the intrinsic factor are secreted here.  Food is changed into a semi-fluid state called chyme. 

-HCL aids in breakdown of food elements within the stomach and influences the acidity of the stomach & the body’s systemic acid/base balance. 

-Mucus protects stomach lining from enzyme & acid activity

-pepsin helps to digest protein

-intrinsic factor is an essential component necessary for Vitamin B12 absorption in the intestine (someone lacking intrinsic factor has “pernicious anemia”, so they are given monthly B12 injections)


Meds may interfere with stomach lining = aspirin, so give Ecotrin, (enteric coated aspirin).


pH of the stomach ranges from 1 - 3.5 pH


Small Intestine – Includes the Ileum, duodenum, and jejunum.

-          20-21 feet long

-          chyme mixes with digestive enzymes bile and amylase

-          segmentation churns the chyme further breaking down food

-          nutrients absorbed are sodium chloride, potassium, magnesium, bicarbonate & calcium

-          absorbs enzymes from pancreas such as amylase (digests carbs), and lipase (digests fats)

-          absorbs bile & gives stool its color; bile is produced in the liver & stored in the gall bladder.  (if gall bladder rmvd, bile goes directly to duodenum)


Large Intestine – (Colon) Includes the cecum, the ascending/transverse/descending/sigmoid colons, the rectum, & the anus.

-          5-6 ft long

-          the ileocecal valve connects the sm. & lg. intestines; it is a pressure valve which prevents the colon contents from regurgitating back into the sm. Intestine.

-          chyme enters thru the ileocecal valve in a semi-fluid state, but the volume of water decreases as the chyme moves thru the colon

Sigmoid – where the waste products are now called feces, which are stored until just before defecation.

Rectum – 4-6 inches long

-          normally remains empty of feces until just before defecation, unless constipation occurs

-          contains vertical & transverse folds of tissue that play a role in retaining feces

-          vertical fold contains arteries & veins-which may become distended due to pressure of straining (hemmorhoids)

-          consists of 2 sphincter muscles (internal & external); the internal sphincter is controlled by the autonomic nervous system; the external is voluntary, and controlled by motor nerves


4 Inter-related Functions

1. Absorption-H2O & NaCl are absorbed daily

2. Protection-releases mucus; purpose is to reduce friction & protect the colon by lubricating the colon contents to prevent trauma of the lining

3. Secretion- Bicarbonate is secreted in exchange for chloride

4. Elimination-removes waste products of digestion & gas



-          a Valsalva Maneuver-occurs during a BM.

o       This begins with mov’t in the left colon, moving stool toward rectum.  The external sphincter relaxes & the abdominal muscles contract.  The contraction of the muscles leads to holding one’s breath while bearing down.  The Maneuver increases intrathoracic, intraocular, and intracranial pressures. 

o       Stool softeners-emollient (ex. Colace) are used for people who have other conditions and shouldn’t perform the valsalva maneuver, to prevent constipation.

-          Mass peristaltic mov’ts push the digested food toward the rectum 3-4 times/day, usually 1 hr after a meal is the strongest.


Factors Affecting Defecation

  1. Stress- incr peristalsis & may cause diarrhea
  2. depression- slows body down & may cause constipation
  3. fiber- adds bulk to stool & helps stimulate peristalsis
  4. physical activity- promotes peristalsis
  5. immobilization- depresses colon motility = slows peristalsis
  6. AGE; infants- stool is liquidy, stomach is small=frequent BM’s, can’t tolerate complex starches

      adolescent males- have rapid growth of large intest. & have increase in HCL secretion which breaks down the foods quickly & makes them             hungry again

      elderly- have slowing of peristalsis & food takes longer to get thru the    system; have loss of muscle tone in the internal sphincter of the large      intest. (maybe due to laxative use); also may have loss of control over           bowel elimination, leading to incontinence; have slowing of nerve           impulses which can lead to constipation or incontinence.

  1. pain
  2. pregnancy- pressure on the intestines causes non-free passage of contents
  3. meds; black stool means high in iron- if not on iron pills though, it may mean bleeding in the upper GI tract (bleeding in lower GI would be red in the stool)

      narcotics- cause constipation

      antibiotics- cause diarrhea (because they destroy normal flora); you can            help give back normal flora by giving yogurt, milk, sour cream,         acidopholus

  1. surgery- general anesthesia causes peristalsis to temporarily stop (colon or        intestinal surgery will cause peristalsis to stop)

      Paralytic Ileus- when there is no peristalsis; pt will have NO bowel sounds;

      can last 24-48 hours; being NPO also delays peristalsis; once peristalsis resumes, the pt is put on clear liquids

      S/s of a paralytic ileus= absent bowel sounds, abdominal discomfort,     distention, vomiting, lack of flatus, fever, decr. urine output

      If not treated, would develop fluid/electrolyte imbalance leading to shock          or death.

-Giving a pt chewing gum after surgery may help reduce or avoid a paralytic ileus

Assessment of bowel function:

Look at patient’s:  normal elimination pattern & if any changes, meds, diet, daily fluid intake, exercise patterns, Hx surgery or past illness in the GI system, bowel diversions (colostomy, etc if present), ask about their methods to promote bowel function (laxatives, enemas?)


Common problems & nursing interventions:

-Constipation- irregular BM, absence of, painful increasing in difficulty, very         hard small pellets

      Causes:  laxative use, meds, diet, lack of fluid

-Impaction- extreme form of constipation, when there is stool in the rectum,           happens in some elderly pts due to immobility-tend to lose sensation

      S/s: hypoactive, diminished bowel sounds, bloat, fluid stool, abdominal             cramping

                  Disimpacting digitally- will gently break it up, pull some out,                 finally give oil-rentention enema to soften stool & help them move out of                        rectum;  VERY gently as not to stimulate the Vagus nerve-if so, they will         become sweaty, light-headed & will have to put them in       Trendelenberg position.

-Diarrhea- a symptom of an underlying problem; expulsion of liquid feces,             more than normal in volume & frequency; causes fluid & electrolyte            imbalance leading to dehydration;

      Nursing Interventions include: IV therapy to replace fluid

      -make sure they have access to bathroom

      -skin care very important for incontinent pts (check peri area q2h)

      -monitor I&O

      -administer anti-diarrheal meds

-Incontinence- due to loss of muscle tone, or due to certain disease process   such as Dementia/Alzheimer’s

-Flatulence- GAS; sometimes a rectal tube can be inserted for extreme cases;

      meds used = antacids


Measures to relieve symptoms of problems in the GI system:

  1. NG tube – thru nose to stomach

      Used to: a. Decompress stomach by removing its contents

                     b. Feed

                     c. Pump out blood or poisons


A.  DECOMPRESSION:  usually done after abdominal or intestinal surgery to prevent paralytic ileus.

      Brands for decompression:  Levin tubing-has red tipped/single lumen, Salem Sump-blue-tipped, has air vent, 2 lumens; air vent is to keep the tube from rubbing vs. the stomach lining & damaging the lining (we put in 20 cc’s of air q4h); 

The tubes are large-bore tubes, and are only kept in 2 wks to prevent nasal necrosis.

Done by Dr’s order which will read:

      NG tube to low intermittent suction/ or NG tube to low continuous suction

Nursing measures would include:  monitor I&O by drawing line on tape on container w/date & initials

-give good nasal care & assess for skin breakdown

-irrigation of the tube q4h or PRN

-meticulous mouth care q2h

-ice chips

-check for placement of the tube to make sure it’s in the stomach 2 ways

1.  insert 20-30 cc’s of air using syringe, listen to left upper quadrant or upper epogastric area; will hear a swishing sound when the air goes in.

2.  check the pH of the gastric secretions; normal = 1 - 3.5 pH, the lower the pH, the less likely bacteria will infect the stomach lining, but if pH is too low, may develop ulcers due to the acid; if > 3.5 pH, it promotes bacteria growth & incr. the risk of aspiration pneumonia (fluid in the lung) due to reflux.


To Check Gastric pH

-pull back secretions into syringe, wipe onto pH paper & compare color immediately to color scale (put whatever is left in syringe back into the pts system to prevent messing up their fl/lyte balance)


Example situation:  If pt has maintenance IV of D5 NS with 20mEq potassium running @100mL/hr, & is putting out 2000mL/day, it’s not enough to replace the lost fluid; the Dr. will order an NG replacement to replace NG secretions cc/cc w/lactated ringers.  (ex. If pt puts out 500 mL during 1 shift, you will put 500 mL lactated ringers back in)


Irrigating the Tube (done w/or w/o a Dr’s order):

Dr’s order would say: Irrigate NG tube w/20-30cc’s of NS q4h & PRN

-put in 20-30mL of NS, then withdraw same amount of fluid, then can get rid of it

-purpose of irrigation is to maintain patency & prevent clogging of the tube


  1. FEEDING /gravage- 3 types of feedings

1)      continuous feeding

2)      Cyclic feeding-nocturnal feeding- feeding at certain times

3)      Bolus/intermittent/syringe feedings – all use syringe, put feed into the NG tube at designated times


Brands of Feeding tubes:

Dobhoff- thin, weighted at the tip (temp tube)

Levin (temp tube)

PEG & G-tube- these are permanent tubes placed surgically


Feeding order from Dr. would read:

Type of supplement being given, the strength, and the rate to give at

Ex.  Continuous feed of Jevity strength (mixed with water) @50mL/hr


Bolus/Intermittent/Syringe feed of Jevity strength 200mL q4h


**Position of patient for feedings:

Continuous feed = Semi-Fowler’s, 45 degree angle all the time (if have to turn pt & put the head of the bed down, must turn pump off first)

Intermittent feed = 45 degree angle DURING feeding + up to 1 hour after, then can lower HOB


Checking Placement of the Feeding Tube:

-must go to x-ray to confirm placement of a Dobhoff tube during INITIAL placement & must wait for x-ray results before feeding

-if regular tube, it’s checked w/20-30cc’s of air via syringe

      *continuous is checked qshift

      *intermittent is checked q4h


  1. LAVAGE – used for cases of bleeding or poisoning

      Brands used:  Levin, Salem Sump


Checking Residual:

-using syringe, pull back (because what’s in the stomach should be absorbed, not lying in there)

-check q4h on intermittent feed

-check q4h on continuous feed, BUT pump must be turned OFF first & must wait 20 minutes before checking residual

-what is taken out should be put back in

-if you get a large amount (100-150cc’s) of residual, means the stomach is not absorbing properly; keep pump off, wait an 1 hr & check again; if high again, change to strength, or call Dr.

      S/s of high residual: nausea, hypoactive bowel sounds, distended abdomen, pt has feeling of fullness => all cause chance of aspiration


BAG & Tubing is changed q24h:

-don’t put any more than 4 hours of formula up at a time (prevents from spoiling/bacteria growth)

-flush w/200cc tap water qshift thru syringe per Dr’s order


Administration of Meds via feeding tube:

      -check placement, flush with warm tap water before and after med administration

      -make sure Drug Guide says the med can be crushed; crushed meds are mixed only with water, not mixed with other liquid medications

      -Dilantin (anti-seizure); feeding must be turned off 1hr prior to and after administration of this drug


Administration of Meds via NG tube:

      -decompression-connected to suction-suction must be TURNED OFF

      -flush with 30-60cc’s warm tap water

      -crush meds if necessary

      -check placement

      -clamp tube for at least 20 minutes after admin of meds (otherwise they’ll                     be sucked back thru the tube!)




Antacids-neutralize, buffer, absorbs; can cause slight constipation

Aluminum Hydroxide Gel =Amphojel


MOM-can be an antacid or laxative-depends on dosage

Histamine H2 Antagonists/antiulcer agents







Types of ENEMAS: (introduction of fluid into the rectum to cause distention & cause BM)

Cleansing enema: evacuates waste from the lower colon

Oil Rentention enema: softens feces

Hypertonic enema: Fleets enema-draws fluid into bowel from subq tissues & blood stream causing rapid distention of the bowel



  1. Barium Enema- x-ray of large colon
  2. Colonoscopy – exploration of the entire colon
  3. Esophagogastroduodenoscopy EGD – exam of the esophagus, stomach, and part of the small intestine
  4. Upper GI series/Barium swallow – x-ray of the esophagus, stomach and the first part of the small intestine



  1. Ova & parasites
  2. Culture & sensitivity
  3. Hemoccult – looking for hidden blood
  4. Stool Assays/Stool Cytotoxin Test – C-diff – occurs when normal flora is altered, C-diff flourishes in the intestinal tract & produces a toxin that causes watery diarrhea; (confirmed by a toxin in the test)

      -in mild cases-if the cause is found, the tx is removal of the cause

      -in moderate cases give Flagil, Vancomycin

      -Pt will be isolated

      -People at RISK:  those who have repeated enemas, prolonged use of NG          tube, GI surgery, overuse of penicillin/clindamycin/cephalosporin/AB’s

      -SYMPTOMS: frequent, foul smelling, watery diarrhea


Thank You Sara, for all of your hard work!

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