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an equal amount of isotonic crystalloid from the bag before injecting the drug to make sure the
volume stays 200 mL.
Romifidine (mg/hr) = rate x body weight = 0.03 mg/kg/hr x 500 kg = 15 mg/hr
Now work out Romifidine (mL/hr) = calculated mg/hr / formulation strength (mg/mL) x = 15
mg/hr / 10 mg/mL = 1.5 mL/hr
Spike bag depending on admin set used. Notice that when running the drip set at 1 drop/second
then the total amount of hours it will run is indicated in the last column! Therefore you will
need to add: 0.75 mL, 1.5 mL or 4.5 mL to a 200 mL bag using a 10, 20 or 60 drop/mL admin
set, respectively.
Morphine (mg/hr) = rate x body weight = 0.05 mg/kg/hr x 500 kg = 25 mg/hr
Now work out Morphine (mL/hr) = calculated mg/hr / formulation strength (mg/mL) x = 25
mg/hr / 10 mg/mL = 2.5 mL/hr
Spike bag depending on admin set used. Notice that when running the drip set at 1 drop/second
then the total amount of hours it will run is indicated in the last column! Therefore you will
need to add: 1.25 mL, 2.5 mL or 7.5 mL to a 200 mL bag using a 10, 20 or 60 drop/mL admin
set, respectively.
Remember to withdraw an equal volume if isotonic crystalloid before injecting the drugs. It is
best to calculate the total volume of drugs and withdrawing the total before injecting anything
into the bag! For example: Use a 20 drop/mL admin set in this example. Before you inject the
romifidine and morphine you will need to withdraw 1.5 + 2.5 = 4 mL of isotonic crystalloid
should be removed first before adding the drugs.
Physiological saline (0.9% NaCl) is an acceptable isotonic solution of choice to mix the cocktails
with.
Table 2: Explanation on how to calculate, formulate and administer a constant rate infusion of
drugs.
Conclusion
Stable sedation and analgesia can be obtained from administering a boluses followed
by a constant rate infusions of various combinations of drugs. Typically α2adrenoreceptor agonists are used. When surgical intervention is required, it is
always advised to include an opioid and appropriate NSAIDs to complement
analgesia. Very invasive surgeries such as standing laparoscopy, thoracotomies have
been done before. Thus this is a very useful technique, provided the clinician
addresses the horse’s analgesic level and maintains a stable sedation to improve
personnel safety and horse comfort during the procedure.
References
1.
2.
3.
4.
Clarke KW, England GCW, Goossens L. (1991) Sedative and cardiovascular effects of romifidine,
alone and in combination with butorphanol, in the horse. Veterin ary Anaesthesia and Analgesia 18,
25-29.
Gaynor J, S., Muir W, W. (2009) Handbook of Veterinary Pain Management. Mosby Elsevier,
Missouri, USA.
Hall LW, Clark KW. (2001) Veterinary Anaesthesia. Harcourt Publishers Limited, England.
Latimer F, Eades S, Pettifer G, Tetens J, Hosgood G, Moore R. (2002) Cardiopulmonary,
hematological, serum chemistry and peritoneal fluid alterations associated with abdominal
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