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

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Nov 01, 2009

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