midterm Flashcards
toxicology
-“The study of poisons and their actions in the
animal body
* Things that poison animals may also poison
people
describe the difference between toxin and toxicant
- Toxin: poisons that originate from a biological source
-Toxicant: poison of man-made or synthetic origin
dose
- “The dose defines the poison”
- A substance can be safe at one dose, but higher at another
- Units: amount of poison per unit body weight
- Dose dose not =concentration
- Most important factor in considering exposure to poisons
-median lethal dose
Median lethal dose = LD5
- Estimation of lethality
- Dose that kills 50% of the test species
- Specific for route and species
dose response
-A toxic effect is proportional to the dose of a substance
* Higher dose = more severe toxic effect
* Response can be lethality, reproductive effects,
effects on the immune system
* Exception: idiosyncratic reactions
* Adverse drug reactions
duration of exposure
- Acute: effects occur within 24 hours of exposure
- Sub-acute: >24 hours to <30 days
- Sub-chronic: 1-3 months of repeated exposures
- Chronic: effects produced by prolonged exposure (>3 months)
- Poisons with a low LD50 tend to be acutely toxic
- Chronic toxicity results from prolonged, repeated exposure
- LD50 is not a good estimate of chronic toxicity
T O X I C O K I N E T I C S
- Toxicity is guided by pharmacokinetics (“toxicokinetics”)
- For an agent to cause toxicity, it needs to interact with its target site at a sufficient dose
-absorption
-distribution
-metabolism
-elimination
distribution
- Factor of organ perfusion, diffusion of the toxic substance, the affinity of the toxic substance for
a certain organ/tissue, binding to plasma proteins - Highly perfused organs: liver, kidney, heart, lung, intestines, brain
- Tend to get the highest exposure to poisons
- Poorly perfused: skin, connective tissue, fat
D E T O X I F I C A T I O N / B I O T R A N S F O R M A T I O N phases
phase 1: Oxidation, hydrolysis, reduction: lipophilic →
more water soluble
phase 2: conjugation
phase 3: elimination via urine, bile, exhalation
-mostly happens in liver
Bioactivation
-metabolism of a parent compound to a more toxic metabolite
* Important examples in veterinary medicine
* Acetaminophen (Tylenol cats)
* Ethylene glycol (antifreeze)
* Bromethalin (rodenticide)
intraspecies differences
- Most individuals fall within the bell curve for a dose-
response relationship - Individuals can respond differently to a given dose of a poison
- Inherent differences in ADME, other factors
- Examples
- Ivermectin and ABC delta-1
- Bedlington terriers and Cu accumulation
- “Treat the patient, not the poison
age and toxicosis
-very young and very old are more susceptible to toxins.
-reduced ability to detoxify, eliminate, and reduced barrier functions.
physiochemical properties of the toxin
-state: gas, aqueous, solid
-size: smaller particles faster
-lipophilicity: passes membranes easily
-acid/base: * Henderson-Hasselbach
* Affects the ionization of a compound in solution → absorption
* Presence/absence of food in stomach
health and physiological status and toxicosis
- Liver and/or kidney disease
- Impaired ability to clear toxic substances from the body
- General debilitation
- Pregnancy, lactation
- Gastrointestinal inflammation
two goals of diagnostics in toxicology
-Confirming exposure to a toxic dose
* Monitoring clinical signs resulting from poisoning
pre analytical errors in sampling
-sample collection:
wrong sample
liver (not enough)
blood/ serum plasma (not enough, hemolysis)
-sample transportation: weather, packaging
-lead to inaccurate results and misdiagnosis
hemolysis in blood sample
- Compromises interpretation of iron, zinc, magnesium,
and chemistry panel - Causes of hemolysis:
- Delayed separation of serum from clot
- Freezing whole blood
- Inadequate centrifugation
- Wrong needle/syringe
- Inadequate volume collected
- Vigorous mixing
- Exception: hemolysis from poisoning
emergency blood panel tests
– four tests:
* Blood glucose
* Total protein
* BUN
* PCV
- Very helpful starting point
- Some toxins cause hypoglycemia
- BUN: kidney problems
- PCV: plasma colour, anemia
blood gas analysis
- Venous versus arterial
- Ionized and total calcium: hyper- and hypocalcemia
- Acid-base status
- pH, pCO2, HCO3, base excess (BE)
- Electrolytes (Na, K, Mg)
- Glucose
- Lactate
in clinic imaging
- T-FAST: air, fluid:
- B-lines: “wet” lung problems
- Pulmonary edema, bleeding
- A-FAST: free abdominal fluid or hemorrhage:
- Radiographs
- Abdominal ultrasound
coagulation panel
- Not all clinics, but many emergency clinics
- Prothrombin time (PT): extrinsic and common pathway
- Partial thromboplastin time (PTT): intrinsic and common pathway
- Considerations:
- Fill up to the line
- Clean venipunctur
VDL: metals and minerals test
- Inductively coupled plasma mass spectrometry (ICP-MS)
- In general: plasma/serum , liver
- Plasma/serum: 2 mL (red or green top tube)
- Liver: 2-5 g fresh or frozen – ship on ice packs
- Liver biopsies: at least 0.2 g
- Lead: 90% of lead is bound to red blood cells
- Heparinized whole blood (green top tube) – ship on ice packs
- Tissue (liver, kidney, etc)
VDL: pesticides
- High performance liquid chromatography (HPLC), liquid chromatography mass spectrometry
(LC/MS), gas chromatography mass spectrometry (GC/MS) - Samples to submit:
- Any suspect bait materials
- Stomach contents: strychnine, OP/carbamates
- Whole blood: acetylcholinesterase activity (OP/carbamates)
- Brain: acetylcholinesterase activity (OP/carbamates)
VDL: water analysis
-Algal toxins: 20 mL of water stored at -4°C: Ship on ice packs
* Metals and trace minerals
* Nitrate
* Drug/pesticide residues
* Some provincial labs offer farm water testing for free
V D L : F E E D A N A L Y S I S
- LC/MS, ICP-MS, colorimetric methods
- Metals and trace minerals
- Nitrates, cyanide
- Mycotoxins: 0.2-2 kg of feed in a resealable plastic bag
- Drug, pesticide residues
- Ionophores: 100 g feed
- Biggest consideration: representative sampling!!
representative sampling of feed
- Sampling affects results
- Contaminants are not typically uniformly distributed in a sample
- General guidelines
- Submit what the animal consumes
- Sample from multiple areas and create a composite sample
shipping your samples containers
- Sample packaging:
- Primary container: leak-proof, plastic containers
- Secondary container: leak-proof, contains absorbent materials in case of leakage
- Tertiary container: rigid (cardboard box)
shipping your samples weather
- Weather conditions:
- Cold weather: room temperature gel packs (not frozen) for samples that do not require chilling
- Chilled (not frozen) gel packs for samples that need to be chilled
- Hot weather: pack sample with cold packs and absorbent material
- Cold packs should be separate from sample
- Insulated shipping container (Styrofoam box)
water quality and animal health
- Most common problem for livestock: decreased performance
- Growth
- Reproduction
- Milk production
- Chronic consumption of poor-quality water
- Acute poisoning from poor quality water is rare
total dissolved solids TDS
-total concentration of ions soluble in water or total salts in water
* Positive charge: Na+, Ca2+, Mg2+
* Negative charge: SO4-, Cl-, HCO3-
* Groundwater > surface water
* More salts = more charge = greater ability of water to conduct electricity
* Electrical conductivity
* High TDS in water: poor palatability
-<1000 acceptable
-7000-10000 unacceptable for most, over for cattle and horses
S U L F A T E S ( S O 4 ) in water
S U L F A T E S ( S O 4 )
* Sodium sulfate, magnesium sulfate, and calcium sulfate
* Component of TDS
- Source: soil, rock, effluent from industry
- Health problems:
- Decreased intake: palatability
- Diarrhea
- Decreased copper absorption in ruminants
- Polioencephalomalacia
- Need to consider total dietary sulfur exposure
sulfates and secondary copper deficiency in ruminants
-Copper, molybdenum, and sulfates form an insoluble complex
* Cu is a component of many important enzymes
- Herd level issues:
- Diarrhea
- High open rate
- Unthrifty
- Increased infections
Polioencephalomalacia
- Ruminants
- Exact mechanism unknown
- Clinical features
- Star-gazing
- Wandering
- Twitching, chewing
- Nystagmus, blindness
- Recumbency
- Seizures
metals + minerals in water
- Sources: naturally occurring in rock + effluent from industry
- Trace minerals: not a significant contribution to dietary requirements
- Metals and minerals are not generally causes of acute poisoning
- Palatability issues – metallic taste
- Iron
- Copper
- Manganese
- Zinc
water associated toxicological problems
- Blue green algae
- Water deprivation sodium ion toxicosis
(“salt poisoning”) - Water hemlock
- Botulism
water testing
- Water quality varies year to year, even within a season
- Cannot rely on previous years’ data
- Annual testing as a baseline
- If there are concerns about water quality or performance is decreasing
When to consider poisoning
- Sudden onset of illness or sudden death in an otherwise healthy animal / group of otherwise healthy animal(s)
- Illness following a recent change to food, medications, environment
- Animal was left in an environment for an extended with potential access to poisons (garage, farm)
- Vague, non-specific illness that has not responded to other treatments
- Concerns for intentional poisoning
- If bloodwork findings are unexpected
approach to managing the poisoned animal
-Stabilize patient*** most important
-History/research of toxin, physical exam
-Decontamination
-Give antidote (if available)
-Minimum database
-Symptomatic and supportive therapy, including monitoring
evaluate the patient
-immediate poisoning: highest priority for triage
* Examine for life-threatening problems (Airway, Breathing, Circulation, Disability, External Assessment)
* TPR – hypo or hyperthermia; heart rate, pulse quality, MM colour, CRT; respiratory rate and effort, including sounds
* Neurologic assessment: level of consciousness
taking a toxicology history
-WHAT: name of product, drug % or dose and ingredients of what dog got into.
-HOW MUCH: estimate ingested amount, compare to LD50 or minimum lethal dose
-WHEN: has the animal developed any symptoms at home, current medications, other animals involved, significant health history, if other treatments have been tried.
decontamination goal
- Principles:
- To minimize absorption and/or promote elimination
- To remove or dilute a topic irritant or corrosive
- When benefits of decontamination outweigh risks*
- Depends on the route of exposure: ocular, dermal, gastrointestinal, inhaled
- Majority of toxins are ingested → gastrointestinal decontamination
gastrointestinal decontamination techniques
- Inducing emesis
- Administration of activated charcoal
- Gastric lavage
Emesis
- The action or process of vomiting: stomach and proximal duodenum emptied
- Physiology: stimulation of the chemoreceptor trigger zone in the medulla or peripheral (GI) receptors
- First line treatment for GI decontamination***
- Indications:
- Recent ingestion* → ideally <1-2 hours post-ingestion (within 30-60 minutes)
- Effective for small, uncharged molecules and weak acids
- Asymptomatic patient
- Unknown ingestion
- Give a small meal before inducing emesis if animal has an empty stomach
drugs to induce emesis
-dogs: apomorphine IV 0.03 mg/kg, IM 0.04 mg/kg BW
-cats: xylazine IM: 0.44 mg/kg BW,
dexmedetomidine, hydromorphone
E M E S I S
* Contraindications:
-SYMPTOMATIC PATIENTS
* Neurologic animal: decreased mentation, seizures (can’t protect airway=ASPIRATION)
* Lack of pharyngeal reflexes, laryngeal paralysis, megaesophagus
* Hypoxia, weakness
- Agent type:
- Corrosive or volatile materials (dilute don’t induce vomit)
- Sharp/pointy materials
- Agents with rapid onset of toxicity
- Animal is actively vomiting or has already vomited
- Brachycephalic dogs at home
- Animal cannot vomit (rabbits, rodents, birds, horses
Emesis high risk cases
-proceed with caution:
* Brachycephalic breeds
* History of seizures
* Very young or very old
* Recent GI surgery (involves muscles in GI tract can rip sutures)
* Significant underlying disease
Emesis risks in clinic
Risks: aspiration, lack of efficacy, sedation, intussusception
* Consider hydration status
* Ensure animal cannot consume its vomit
-> repoisoning
- Administer anti-emetic after emesis:
- Maropitant (Cerenia) – 1 mg/kg SC $$
- Ondansetron (Zofran) – 0.1-0.2 mg/kg SC, IM, IV $$$$
- ± Metoclopramide (Reglan, Emeprid) - 0.2-0.5 mg/kg SC, IM
At home emesis type and side effects
-hydrogen peroxide 3%: DOGS ONLY
* Mechanism: stimulates pharyngeal receptors (CN IX) + local gastric irritation
* Under recommendation of vet or poison control center
* Fresh/unexpired → bubbly
* Dose: 1-2 mL/kg (max. 3 tablespoons)
- Potential side effects in dogs:
- GI irritation and ulceration
- Aspiration
- Lack of efficacy
- GDV
do not use: salt, mustard powder, syrup of ipecac, dishwasher fluid, finger.
A C T I V A T E D C H A R C O A L indications
-binds up toxins and poisons and prevents absorption into blood stream.
-High heat and temperature processed wood → very porous
* Adsorption of compounds in the GIT to decrease absorption
- Indications: first line treatment for poisoning
- Recent ingestion
- Asymptomatic, stable patient
activated charcoal contraindications
- Alcohols, xylitol, hydrocarbons, metals, nitrates/nitrites, caustic/corrosive agents, salt, chlorates
- Severe dehydration
- Potential for GI surgery
activated charcoal dosing **dont need to know dosing
- Dose: 1-2 g/kg BW q6-8 hr, diluted 1:10 in water
- First dose should contain a cathartic (sorbitol): 1-2 mL/kg of 70% solution
- Consider repeated doses (without cathartic) for compounds that undergo EHC, have a long t1/2, or are
extended release (“SR”, “XR”, “ER”) - Give immediately after pet has vomited
- Toxiban: 10-20 mL/kg
- Ways to give charcoal: put in a small amount of food, through OG tube, syringin
activated charcoal risks
- Risk of administration: hypernatremia, poor visibility during endoscopy, aspiration
- Risk factors for hypernatremia:
1. Dehydration
2. Vomiting, fasting, or incapable of drinking
3. Predisposition to electrolyte imbalances (CKI, endocrine diseases, psychogenic polydipsia)
4. Poisons that cause hypernatremia (chocolate, bromethalin, salt, playdough)
cathartics
- Reduces GI transit time → enhanced fecal expulsion
- Ingredient in ToxiBan
- Other options: sodium sulfate (Glauber’s salt), magnesium sulfate (Epsom salt)
- Contraindications:
- GI stasis
- Ingestion of a caustic substance
- Patient is hypotensive and/or volume depleted
- Patient has diarrhea or has been given a laxative
- Renal insufficiency, electrolyte imbalance
gastric lavage indications
- Flushing the stomach with water through an OG/NG tube to remove stomach contents
- “Pumping the stomach”
- Performed under sedation or general
anesthesia with endotracheal intubation - Indications:
- Animal cannot vomit
- Emesis has been unsuccessful
- Large volume of stomach contents present
- Symptomatic patient
- Potentially lethal exposure
ocular decontamination
-To prevent corneal damage or damage to deeper structures of the globe
* Corrosive and irritant agents
* Examination of the eye should be performed to check for damage
* Rinse eye with tepid water (tap, saline, or distilled) for 20-30 minutes
* Owner can start ocular decontamination at home
* Sedation may be required
* Do not use contact lens solution
* Flush medial to lateral to prevent exposure to the other eye
inhalational decontamination
- Multiple mechanisms: irritation, increased secretions, pulmonary edema, aspiration
- Can be complex mixtures – smoke from a fire
- Main principle: move to fresh air
- Ensure adequate ventilation in treatment area
- Occupational hazard: zinc phosphide exposure
antidotes
- Most toxic substances do not have specific antidotes
- Certain antidotes only work within a certain time window
- Antidotes can have side effects
- May not be readily available
- Can be expensive
- Not a guarantee of success
symptomatic and supportive care CNS: seizers, tremors
- Seizures (status epilepticus): diazepam, general anesthesia (propofol)
- Severe metabolic side effects of uncontrolled seizures
- Tremors: methocarbamol, acepromazine
symptomatic and supportive care CNS: agitation, hypoglycemia, cerebral edema
- Agitation/hyperexcitability: sedation – acepromazine, butorphanol
- Hypoglycemia: IV dextrose
- Minimum dilution of 50%
- Cerebral edema: mannitol or hypertonic saline, + furosemide, + colloids
cardiovascular and respiratory supportive care
- Blood pressure support: fluids, positive inotropes, vasoconstrictors
- Blood products: whole blood, pRBCs, FFP, FP
- Antiarrhythmics: beta-blockers, others
- Oxygen
- Intubation: manual or mechanical ventilation
- Acid base and electrolyte abnormalities
- Hyperkalemia: regular insulin w/ dextrose
- Hypercalcemia: bisphosphonates, example vitamin D tox.
- Monitoring HR/RR, oxygenation (pulse oximetry), ventilation (PaCO2), ECG, blood pressure,
PCV/TP/Erythrogram, electrolytes + acid/base status
support and symptomatic care: GI drugs and products
- Vomiting: anti-emetic, fluids, specific electrolytes as needed
- Diarrhea: fluids, specific electrolytes as needed
- Gastroprotectants: metoclopramide, sucralfate, omeprazole
- GI bleed: blood products may be necessary
- Monitoring PCV/TP, CBC/chemistry/UA for indications of dehydration or loss of absorptive function (protein losing enteropathy
support and symptomatic care: liver
- Hepatoprotectants (N-acetylcystine NAC), vitamin E, Silumarin (milk thistle)
- Dietary change
- Dextrose
- Vitamin K
- Fluids
- Lactulose
- Ascites: fluids + diuretics
- Monitoring chemistry panel (liver
enzymes + indicators of hepatic
function), mentation,
MM/plasma colou
support and symptomatic care: kidney
- Fluids → diuresis
- Blood pressure support
- Dialysis
- Dietary change
- No “nephroprotectants”
- Monitoring chemistry panel for indicators of GRF (urea, creatinine, electrolytes), urinalysis for concentrating ability (USG), presence of abnormal findings in urine, urine output
intravenous lipid emulsion IVLE mechanism, dose
- Developed to treat lidocaine overdose in humans
- Acts as nutritional + energy support
- Mechanism: acts as a sink for lipophilic drugs → prevents absorption of
drugs from bloodstream - Dose: 1.5 mL/kg of 20% IVLE IV for one minute, followed by 0.25 mL/kg/min
for 30-60 minutes - Monitor patient for lipemia
- Lipophilic drugs: ivermectin, baclofen, lidocaine, marijuana
cholestryramine uses
Questran:
* Anti-lipemic, bile acid sequestrant
* Human drug: treats bile acid malabsorption from chronic diarrhea
- May be useful for lipophilic poisons with a high degree of enterohepatic circulation
- Vitamin D3
- Microcystin
- NSAIDs
- Decontamination mechanism: combines with bile acids in intestines to form a complex that is excreted in the feces
- Mix powder with water or canned wet food
Cholestryramine contraindications/ cautions/ side effects
- Contraindications
- Pregnant/lactating animals
- Biliary obstruction
- Cautions:
- Interferes with absorption of fat-soluble vitamins
- Interferes with absorption of oral medications
- Patients with kidney problems, hypovolemia
- Side effect (humans): constipation
calling into the pet poison hotline
-initial call taken by vet/ vet tech
-history taken
-assessment made as to risk concern
-trreatment needs determined
-follow up by veterinary clinic as needed throughout patients care
patient assessment of the poisoned animal
-is the patient stable?: assess vitals, neurological state, hydration status, lab results
-any current/ past medical concerns?: longstanding medical diseases, recent illness or surgery, current prescription and non-prescription medications
poisoned animal step 2 singlement
Species:
* Species differences with toxicities
Breed:
* Brachycephalic breeds
* Increased risk with emesis
* ABCB1 (MDR-1)gene mutation risk
* Higher toxicity risk with certain drugs
* Collie 70%, long-haired whippet 65%,
Australian shepherd 50%
patient assessment age?
Age factors
-Hepatic metabolizing function
decreased <12wks of age
-Cardiac output more HR dependent in young animals
-Tachycardia vs bradycardia
-Potentially lower toxic dose for
neonates or geriatric patients
-Renal compromise and hepatic
impairment in older patients
patient assessment weight?
-Difference between toxic and non-toxic ingestions is often a thin line
-Accurate weights needed to properly assess toxicity risk
-Decontamination preferences in large vs small breed
-Added risks/concerns with obesity
toxicity assessment
1.) what was the toxin
2.) what is the route of exposure: dermal, oral, ocular, inhaled
3.) what was the dose or amount exposed to? THE DOSE MAKES THE POISON
4.) time since exposure? LARGE FATOR, in rate of absorption, helpful for decontamination methods, clinical signs
5.) where did the exposure occur?
Decontamination methods: Gastrointestinal
Emesis Activated
charcoal Cathartics
Gastric Lavage Whole bowel
irrigation
Endoscopy and surgical removal
emesis gastric content recovery
Gastric content recovery:
* 49% (range 9-75%) w/emesis < 30 min. after ingestion
* 17-62% 1 hr after ingestion
* Emesis most common w/in 2 hrs after ingestion
safe emesis substances up to 6 hr after ingestion
- Grapes/raisins
- Chocolate
- Gum
- Large plant ingestion
- Massive ingestion
- Drugs that decrease gastric emptying
o Opioids
o Salicylates
o Anticholinergics
o Tricyclic antidepressants
emesis in dogs drugs
-apomorphine: dopaminergic drug: stimulated CRTZ
-Ropinirole
(Clevor®): D2 receptor agonist in CRTZ
* Metoclopramide can be used to reverse AE
* Dogs only
-hydrogen peroxide:
* 3%, fresh, bubbly, non-expired
* Gastric irritant
* 1-2 ml/kg, max 50mls TOTAL (may exceed in larger dogs to 60-75 mls, case dependent)
Remember, 1 tsp/10 lbs, 1 tbs/30 lbs
emesis in cats drugs
-xylazine: alpha 2 ardenergic agonist, antidote: yohimbine
-dexmetetomidine: alpha 2 ardenergic agonist. antidote: antisedan
-Cons to both
Efficacy – May be as low as 50%
Excessive sedation
Cardiovascular collapse
-DO NOT USE in cats: hydrogen peroxide, apomorphine
decontamination methods not recommended
-salt: hypertranemia
-liquid dish soap: ineffective, aspiration risk
-digital stimulation: physical injury
-syrup of ipecac: cardiac effects and prolonged vommiting
active charcoal pros
- Readily available
- Relatively inexpensive
- Suspected to bind most toxicants
- May ↓ absorption by 25-30%
w/delayed administration - Can administer with food
cons
Window for administration?
* Hypernatremia
* Difficult to administer
* Messy
* Vomiting after administration
* Diarrhea/changes to stool
* Binds to therapeutic medications
* Unknown benefit
Activated charcoal dosing
- Standard dose 1-2 g/kg PO
- 1-5 g/kg (Plumb’s)
- Multi-dose
o Repeat in 6-8 hours if extended-release formula medication
o Repeat q 6-8 hours for 24 hours if enterohepatic
recirculation occurs
o *Manufacturer suggests ½ the dosage, but gives no recommended dosing schedule
Decontamination methods: Cathartics
mech: Osmotic – draws water into GIT, Accelerates speed of drug transit through GIT. Decrease time for toxin absorption,
Decreases time for desorption of
toxin from activated charcoal
-Sorbitol: Most rapid & potent cathartic. given with activated charcoal
gastric lavage indications
- Species that do not vomit
- Unsuccessful emesis attempt
- Large volume of stomach
content - Symptomatic patients with a
large ingestion - Varies based on toxin
- Potentially life-threatening
toxin
gastric lavage
- Hydrocarbon ingestions
- Corrosives
- Recent surgery
- Unstable patients
- Patients at higher risk for
bleeding or injury - Inappropriate timeframe
- Liquid toxins- limited benefit
Decontamination methods:
Whole bowel irrigation
indications:
* Iron
* Enteric coated drugs
* Sustained or ER formulations
* Packets of drugs
* Uncommonly performed
Polyethylene glycol:
* 25-40 ml/kg PO followed by continuous oral infusion of 0.5 ml/kg/hr → radiographic clearance or clear effluent
Decontamination methods:
Endoscopy
endoscopy:
* Coins
* Non-leaking batteries
* Especially button batteries
* Patches
* Fentanyl, lidocaine
* Bottles/plastic
* Other metals
* Evaluate for injury to esophagus/stomach
Decontamination methods:
surgical removal
Unable to remove endoscopically
oDiisocyanate/Isocyanate/Polyurethane containing expansive glues
o(Original Gorilla Glue®)
oSharp objects
oLarge foreign bodies
oMedication bezoars
oLeaking batteries
oLarge # of objects
o+/- yeast bread dough
- Negatives
oMay be delayed pending stability of patient
oGeneral anesthesia
oCost
oAccessibility of equipment
oOperator skill-Endoscop
