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

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