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Fluid administration for the treatment of isoflurane-induced hypotension in dogs

Aarnes, Turi K.

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2009, Master of Science, Ohio State University, Veterinary Clinical Sciences.

Isoflurane is the most commonly used inhalant anesthetic in veterinary practice. Hypotension, a side effect of isoflurane anesthesia, increases morbidity and mortality. Intravenous (IV) fluid therapy is frequently proposed for correction of anesthetic-induced hypotension. The efficacy of fluid therapies for the treatment of isoflurane-induced hypotension has not been investigated. The objective of our study was to determine the effect of the IV administration of a crystalloid (Lactated Ringer’s Solution, (LRS)) or colloid (Hetastarch, HES) on isoflurane-induced hypotension in dogs. We hypothesized that IV fluid administration would correct isoflurane-induced hypotension and that HES administration would correct isoflurane-induced hypotension more rapidly, more effectively, and with a smaller volume than with LRS.

Six Beagles were studied. Isoflurane minimum alveolar concentration (MAC) was individually determined. All dogs underwent each treatment in a random-ordered three-way cross-over design, separated by a minimum of 7 days: an infusion of HES, an infusion of LRS, and no IV fluid administration (NFA).

Following propofol induction and isoflurane maintenance, dogs were instrumented. Dogs were maintained at 1.3 times MAC for an additional 30 minutes. Baseline data were collected. The isoflurane concentration was increased to achieve a systolic arterial blood pressure (SABP) of 80 mmHg (time 0). The isoflurane concentration required to attain a SABP of 80 mmHg was maintained for the duration of the experiment. Fluid administration in the HES and LRS groups began at time 0 at a rate of 80 mL/kg/hr.

Fluid administration was discontinued if SABP returned to within 10% of baseline. If SABP did not return to within 10% of baseline values, fluid was administered to a pre-determined maximum volume: 40 mL/kg for HES and 80 mL/kg for LRS.

Heart rate, SABP, mean ABP, diastolic ABP, mean pulmonary artery pressure, right atrial pressure, cardiac output, and blood volume change (BV) were measured and recorded at baseline, time 0, and at 15, 30, 45, 60, 90, and 120 minutes in all groups, and at 150 and 180 minutes in the fluid treatment groups.

Blood gases, pH, lactate, electrolytes, packed cell volume (PCV), total protein (TP), albumin, colloid osmotic pressure (COP), and viscosity were determined at baseline, time 0, 15, 30, 60 and 120 minutes, and viscosity was also determined at 180 minutes in the fluid treatment groups. Blood was collected 24 hours after recovery for hemogram, PCV, TP, lactate, viscosity, and chemical profile analysis. Cardiac index (CI) and systemic vascular resistance (SVR) were calculated.

Administration of 80 mL/kg of LRS did not increase SABP in any dog, while administration of 40 mL/kg or less of HES increased SABP in four of six dogs. SABP, DABP, and MABP were significantly increased in dogs that received HES compared with LRS. CI increased and SVR decreased with fluid administration. Viscosity was lower in dogs that received LRS compared with HES. PCV and TP decreased with LRS. COP increased with HES.

Hetastarch but not LRS increased SABP despite lower volumes of HES administered. The present study supports the administration of HES over LRS for the treatment of isoflurane-induced hypotension in dogs.

Richard Bednarski, DVM, MS (Committee Chair)
Phillip Lerche, BVSc, PhD (Committee Member)
John Hubbell, DVM, MS (Committee Member)
Karsten Schober, DVM, PhD (Committee Member)

Recommended Citations

Citations

  • Aarnes, T. K. (2009). Fluid administration for the treatment of isoflurane-induced hypotension in dogs [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236023502

    APA Style (7th edition)

  • Aarnes, Turi. Fluid administration for the treatment of isoflurane-induced hypotension in dogs. 2009. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1236023502.

    MLA Style (8th edition)

  • Aarnes, Turi. "Fluid administration for the treatment of isoflurane-induced hypotension in dogs." Master's thesis, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236023502

    Chicago Manual of Style (17th edition)