Guidelines for managing the colic patient
What are we managing?
• Hydration
o dehydration
o ongoing losses
o ingesta
• Inflammation
• Pain
• Distention
• Motility and ileus
• Endotoxemia
Hydration
• Decrease in hydration status decreases motility
• Fluid circulation shifts from gut
o Colonic fluid used to increase circulating volume
• With impactions ingesta becomes dehydrated
• Ongoing losses need to be accounted for
o Especially important in ileus
Fluid therapy
• Oral fluid therapy
o Used in impactions + diarrhea
o More effective for hydrating ingesta over IV fluids (Lopes et al AJVR 2004;65: 695-204)
o Use indwelling N-G tube
• small or large bore
o Continuous or intermittent
o Water plus balanced electrolyte solution most effective for hydrating colonic ingesta
• Per liter
-5.37g NaCl (table salt)
-0.37g KCl (lite salt)
-3.78g NaHCO3 (Baking Soda)
o Epsom salts most effective for softening small colon ingesta
• Osmotic cathartic
• 1g/kg SID or BID
o CRI
• 1-2 L/hr
• more rapid rate can make them colicky
• Set-up
-Used 5 L fluid bags
-Large IV Set
-Small bore NG tube (foal)
o Intermittent boluses
• 2-3 L Q2-3hrs
• Crystalloids
o Importance:
• Maintain cardiovascular status
• Maintain electrolyte balance
• Horses may have ongoing losses of fluids due to:
• Ileus and reflux losses
• Diarrhea
• Leaky capillaries from damaged gut resulting in extravasation of fluids
o Cautions:
• Due to decreases in plasma volume and total protein, rapid administration can cause edema formation in lung, digit, brain, intestine, periphery
o Normosol R, LRS, 0.9% NaCl , Plasmalyte
• Prefer balanced solutions over 0.9% NaCl to avoid hypernaturemia
• 0.9% NaCl in HYPP horses
o Replace as 10-20 L bolus
o Maintenance – 2 ml/kg/hr
o Calculate % dehydration (% dehydration X bwt in kg = L of replacement) and ongoing losses (amount lost in reflux or diarrhea)
o Monitor hydration: avoid over-hydration
• PCV/TP
• Urine specific gravity
• 1.010-1.018 when on fluids
• Colloidal oncotic pressure
• Central venous pressure
• Blood pressure
o Hypertonic Saline
• 4-6 ml/kg
• Increases cardiac output and stroke volume
• Shown to more rapidly normalize lactate in endotoxemia models (Bertone et al AJVR 1990;5(7):999-1007, Ardern et al ACVS Proc 1991, p 10)
• Effects are only transient
• Used for emergency fluid resuscitation, but must be followed by crystalloids at 2-3 X maintenance
• Combining with hetastarch at 4 ml/kg will prolong resuscitation efforts (Prough DS Anes Analg 1991;73:738-44)
• Electrolyte Supplementation
o Essential electrolytes decrease due to:
• Lack of intake
• Diuresis from fluid therapy
• Acid-base abnormalities
• Endotoxin binding (calcium)
• Gastro-intestinal loss via diarrhea (potassium)
o KCl (20 meq/L)
o Calcium borogluconate (20 ml/L)
o MgSO4 (150 mg/kg/day)
o Calcium and magnesium tend to be lower in horses with strangulating lesions (Garcia-Lopez AJVR 62(1):Jan 2001 7-12)
o Low levels can contribute to ileus and cardiac arrhythmias
• Colloidal Treatment
o Solutions that contain large molecular weight molecules that do not pass out of the vasculature and maintain colloidal oncotic pressure
o 100% are retained in vasculature (Crystalloids -only 25%)
o Increases blood volume and decreases extra-vasation of fluids
o Used in horses with endotoxemia to expand circulating volume
o Used in hypoproteinemic horses (decreased albumin)
o Help maintain intravascular oncotic pressure especially when protein is less than 4.0 g/dl
o Two types: synthetic and natural
• Hetastarch (synthetic)
-Variable molecule sizes
-Molecule sizes larger than that of albumin so less likely than plasma to leave vasculature
-Lasts for several days
-Increases COP
-Decreases PCV,TP
-10 ml/kg/day
• Plasma (natural)
-Increases total protein
-2-4 ml/kg needed to maintain plasma protein > 4 g/dl (Hardy et al Eg Surgery 1999.294-306)
-Approximately 1L required to increase TP by 1 g/dL (Hardy et al Eg Surgery 1999.294-306) Anti-endotoxic antibodies
-Not as effective as Hetastarch as the molecule size of plasma proteins still allows for its loss from the vasculature
-60% redistributed to interstitial tissue
-Cannot be given rapidly, so not good for rapid resuscitation
o We often use Hetastarch and Plasma in combination for horses with decreased total protein
Inflammation
• Caused by distention or obstruction
• Primary in proximal enteritis
• Anti-inflammatory treatment
o Flunixin meglumine (Banamine) most common NSAID used in colic patients
• 1.1 mg/kg BID
• Analgesic
• Anti-endotoxic
• Inhibits cyclooxygenases (COX)
• Decrease prostaglandin and thromboxane A2
• Effective as an analgesic when inflammatory response is present
• Other anti-inflammatory drugs include
o Phenylbutazone
o Ketoprofen
o DMSO
Distention
•Mechanical or functional?
• Trocharization
o Procedure
• Right or left flank
• Auscult for "ping"
• If left side ultrasound for spleen
• Local block
• Aseptic prep 14 gauge 5" catheter
• Insert sharply 1/2 length
• Remove stylet
• After gas evacuation has stopped remove catheter
• Inject gentamicin during removal (±)
o Complications
• Peritonitis
o Indications
• Severe gas distention & surgery not an option
• Prior to referral when severe gas distention present and/or long trailer ride
Pain
• Alleviate source
• Distention
o Trocharization
o Nasogastric intubation
o Analgesics
• Break cycle of pain
• Control while waiting for resolution (impactions) or surgery
-Alpha 2 angonists
• Provide analgesia by binding to α2 receptors in CNS
• Most potent visceral analgesics
• Sedatives
• Xylazine: 1.1 mg/kg
• Duration of action = 20 minutes
• Detomidine: 20 – 40 μg/kg
• Duration of action = 45-90 minutes
o NSAIDS
• Flunixin meglumine
-1.1 mg/kg
-Effective for visceral pain
-Rapid onset of action
-Duration of action 6 to 12 hours
-Strong COX-1
o Opioids
• Agonists and mixed agonists and antagonists that suppress nociceptive cells.
• Inhibition of pain transmission in the dorsal horn of the spinal cord and brain
• Butorphanol: 0.1 – 0.4 mg/kg IV or IM
-3 minutes until onset after IV administration
-Peak 15 to 30 minutes
-Provides 60 to 90 minutes of analgesia IV and up to 4 hours IM.
-Good for visceral analgesia, especially with alpha 2 agonists
Motility
• Decreases with even minor GI insult
• Fluid therapy, decreasing inflammation, and/or decreasing distention will help stimulate motility
• May need primary motility stimulation in severe cases of ileus
Ileus
• Loss of normal motor function of GI tract
• Most common complication following GI surgery
• Predominantly associated with small intestinal lesions
o 6 times more likely
• Incidence 6-21%
• Mortality 13-43%
• Usually occurs in first 12-36 hours post-operatively
• Requires intensive medical management
o Fluid therapy critical to keep up with ongoing losses via gastric reflux
o Drugs to stimulate motility
Motility stimulators
• Lidocaine (1.3mglkg IV bolus followed by CRI 0.05 mg/kg/min)
o In people shown to shorten post-operative paralytic ileus
o Has anti-inflammatory properties: Inhibits prostaglandin synthesis and granulocyte migration
o Stimulates smooth muscle directly
• Metoclopramide (0.04 mg/kg/hr)
o Decreased volume, duration, and rate of reflux (Dart et al Aust Vet J. 1996 Oct;74(4):280-4)
• Bethanechol (0.025 mg/kg IV or SC Q4-6H)
o Increases gastric and cecal emptying
• Others
o Neostigmine (0.022 mg/kg IV)
o Erythromycin (0.5-1 mg/kg in 1L saline over 60 minutes Q6H)
o Acepromazine/yohimbine
Endotoxemia
• Endotoxins are lipopolysaccharides from the cell walls of Gram negative bacteria
• Exist normally in the lumen of the intestine
• Toxin moves easily across damaged intestinal cell walls and goes into circulation where it exerts its systemic effects, which are mainly inflammatory responses
• Results in:
o Severe hemodynamic and cardiovascular disturbances
o Decreases circulating vascular volume
o Increases capillary permeability
o Ileus
o Coagulation disorders
• Signs:
o Pain
o Increased heart rate
o Edema
o Decreased motility
o Intestinal distention
o Reflux
o Thrombosis
o Bleeding tendencies
• Treatment for Endotoxemia
o Prevent absorption into circulation
o Bind or neutralize toxin
o Prevent synthesis or release of inflammatory mediators
o Prevent cellular activation by endotoxin
o Medical management of products of endotoxemia
• Polymyxin B (6,000 IU/kg TID) (Morresey PR, Mackay RK Am J Vet Res. 2006 Apr;67(4):642-7)
-Antibiotic
-Binds Lipid A portion of toxin thereby inactivating it
-Shown to effectively reduce endotoxin associated inflammation (Parviainen AJVR 62(1) Jan 2001 72-75)
-Can be nephrotoxic
• Hyperimmune plasma
-Contains anti-bodies that bind the endotoxin
-Treated horses shown to have improved clinical appearance and shorter recovery time than control horses (Spier SJ Circ Shock 28:235-248, 1989)
-Horses can have a hypersensitivity reaction to plasma so they must be monitored carefully during administration
• Flunixin meglumine (1.1 mg/kg IV BID or 0.25 mg/kg IV QID)
-Inhibits prostaglandin's effects of endotoxin
-Reverses hypotension
-Decreases temperature
-Decreases heart rate
-Improves gas-exchange
• Pentoxyfilline
-Improves circulation
-Oral absorption questionable
-May take too long to have desired affects
• Heparin
-Prevents coagulation disorders
Antibiotics
• For treatment of sepsis
• Appropriate therapy found to significantly reduce mortality
• Typically utilize broad-spectrum antibiotics
• Cautions:
o Can break down bacterial cell walls resulting in endotoxin release
o Can cause a antibiotic associated diarrhea
Nutrition
• Important in the critically ill patient as they are in hypermetabolic state
• Appropriate caloric intake promotes healing, decreases morbidity
• Two types:
o Enteral (oral)
• Best form of nutrition:
-Promotes mucosal healing
-Helps maintain normal motility and function
-Normal flora of bacteria maintained
-Decreases chances of sepsis
-Cheapest
• Contraindications
-Ileus
-Obstructions
-Shock states
o Parenteral (IV)
• IV formulations that are made to meet the horse's daily energy requirements
• Combination of fat, glucose, and amino acids
• Indications:
-When enteral feeding cannot take place for greater than 3 days
-Indicated earlier in horses in poor body condition or increased metabolic needs (e.g. lactating mares)
-In horses at risk for hyperlipemia
-Hypertriglyceridemia
• Complications:
-Catheter problems
-Hyperglycemia
-May also require concurrent treatment with insulin
-Infection leading to sepsis