It's critical – Managing the colic patient (Proceedings)

What are we managing?

• Hydration

• Dehydration

• Ongoing losses

• Ingesta

• Inflammation

• Pain

• Distention

• Motility and ileus

• Endotoxemia

Hydration

• Decrease in hydration status decreases motility

• Fluid circulation shifts from gut

• Colonic fluid used to increase circulating volume

• With impactions ingesta becomes dehydrated

• Ongoing losses need to be accounted for

• 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

o 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

• Importance:

o Maintain cardiovascular status

o Maintain electrolyte balance

o Horses may have ongoing losses of fluids due to:

o Ileus and reflux losses

o Diarrhea

o Leaky capillaries from damaged gut resulting in extravasation of fluids

• Cautions:

o Due to decreases in plasma volume and total protein, rapid administration can cause edema formation in lung, digit, brain, intestine, periphery

• Normosol R, LRS, 0.9% NaCl , Plasmalyte

o Prefer balanced solutions over 0.9% NaCl to avoid hypernaturemia

• 0.9% NaCl in HYPP horses

• Replace as 10-20 L bolus

• Maintenance – 2 ml/kg/hr

• Calculate % dehydration (% dehydration X bwt in kg = L of replacement) and ongoing losses (amount lost in reflux or diarrhea)

• Monitor hydration: avoid over-hydration

o PCV/TP

o Urine specific gravity

o 1.010-1.018 when on fluids

o Colloidal oncotic pressure

o Central venous pressure

o Blood pressure

• Hypertonic Saline

o 4-6 ml/kg

o Increases cardiac output and stroke volume

o 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)

o Effects are only transient

o Used for emergency fluid resuscitation, but must be followed by crystalloids at 2-3 X maintenance

o Combining with hetastarch at 4 ml/kg will prolong resuscitation efforts (Prough DS Anes Analg 1991;73:738-44)

Electrolyte supplementation

• Essential electrolytes decrease due to:

o Lack of intake

o Diuresis from fluid therapy

o Acid-base abnormalities

o Endotoxin binding (calcium)

o Gastro-intestinal loss via diarrhea (potassium)

• KCl (20° meq/L)

• Calcium borogluconate (20 ml/L)

• MgSO4 (150 mg/kg/day)

• Calcium and magnesium tend to be lower in horses with strangulating lesions (Garcia-Lopez AJVR 62(1):Jan 2001 7-12)

• Low levels can contribute to ileus and cardiac arrhythmias

Colloidal treatment

• Solutions that contain large molecular weight molecules that do not pass out of the vasculature and maintain colloidal oncotic pressure

• 100% are retained in vasculature (Crystalloids - only 25%)

• Increases blood volume and decreases extra-vasation of fluids

• Two types: synthetic and natural

• Used in horses with endotoxemia to expand circulating volume

• Used in hypoproteinemic horses (decreased albumin)

• Help maintain intravascular oncotic pressure especially when protein is less than 4.0 g/dl

• Hetastarch (synthetic)

o Variable molecule sizes

o Molecule sizes larger than that of albumin so less likely than plasma to leave vasculature

o Lasts for several days

o Increases COP

o Decreases PCV,TP

o 10 ml/kg/day

• Plasma (natural)

o Increases total protein

o 2-4 ml/kg needed to maintain plasma protein > 4 g/dl (Hardy et al Eg Surgery 1999.294-306)

o Approximately 1L required to increase TP by 1 g/dL (Hardy et al Eg Surgery 1999.294-306) Anti-endotoxic antibodies

o Not as effective as Hetastarch as the molecule size of plasma proteins still allows for its loss from the vasculature

o 60% redistributed to interstitial tissue

o Cannot be given rapidly, so not good for rapid resuscitation

• 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

• Flunixin meglumine (Banamine) most common NSAID used in colic patients

• 1.1 mg/kg BID

• Analgesic

• Anti-endotoxic

• Inhibit cyclooxygenases (COX)

• Decrease prostaglandin and thromboxane A2

• Effective as an analgesic when inflammatory response is present

• Other anti-inflammatory drugs include:

• Phenylbutazone

• Ketoprofen

• DMSO

Distention

• Mechanical or functional?

• Trocharization

• Nasogastric intubation

Trocharization

• Right or left flank

• Auscult for "ping"

• If left side ultrasound for spleen

• Local block

• Aseptic prep 14 gauge 5" catheter

• Insert sharply ½ length

• Remove stylet

• After gas evacuation has stopped

• Inject gentamicin during removal (+/-)

Trocharization

• Complications

• Peritonitis

• 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

• Trocharization

• Nasogastric intubation

• Analgesics

• Break cycle of pain

• Control while waiting for resolution (impactions) or surgery

Analgesia

• 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

• µ and receptor actions

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

• 6 times more likely

• Incidence 6-21%

• Mortality 13-43%

• Usually occurs in first 12-36 hours post-operatively

• Requires intensive medical management

• Fluid therapy critical to keep up with ongoing losses via gastric reflux

• Drugs to stimulate motility

Motility stimulators

• Lidocaine (1.3mglkg IV bolus followed by CRI 0.05 mg/kg/min)

• In people shown to shorten post-operative paralytic ileus

• Has anti-inflammatory properties: Inhibits prostaglandin synthesis and granulocyte migration

• Stimulates smooth muscle directly

• Metoclopramide (0.04 mg/kg/hr)

• 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)

• Increases gastric and cecal emptying

• Others

• Neostigmine (0.022 mg/kg IV)

• Erythromycin (0.5-1 mg/kg in 1L saline over 60 minutes Q6H)

• 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:

• Severe hemodynamic and cardiovascular disturbances

• Decreases circulating vascular volume

• Increases capillary permeability

• Ileus

• Coagulation disorders

• Signs:

• Pain

• Increased heart rate

• Edema

• Decreased motility

• Intestinal distention

• Reflux

• Thrombosis

• Bleeding tendencies

Treatment for endotoxemia

• Strategies for treating endotoxemia include:

• Prevent absorption into circulation

• Bind or neutralize toxin

• Prevent synthesis or release of inflammatory mediators

• Prevent cellular activation by endotoxin

• 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

Other considerations

• Antibiotics

• Nutrition

Antibiotics

• For treatment of sepsis

• Appropriate therapy found to significantly reduce mortality

• Typically utilize broad-spectrum antibiotics

• Cautions:

• Can break down bacterial cell walls resulting in endotoxin release

• 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:

• Enteral (oral)

• Parenteral (IV)

• Enteral

• 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

• Parenteral nutrition

• Indicated 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)

• Indicated in horses at risk for hyperlipemia

• Indicated when hypertriglyceridemia

• IV formulations that are made to meet the horse's daily energy requirements

• Combination of fat, glucose, and amino acids

• Complications:

• Catheter problems

• Hyperglycemia

• May also require concurrent treatment with insulin

• Infection leading to sepsis