Texas Equine Veterinary Association

www.teva-online.org • Page 20 The Guaifenesen-Ketamine-Xylazine (GKX) combination is one of many methods of Total Intravenous Anesthesia (TIVA) used in horses. GKX is unique from the standpoint that it can be used in the surgical suite or for short procedures performed in the field. Supplies needed for perform GKX anesthesia include an intravenous catheter (14 gauge x 5.25 inches is preferred) and an administration set. concentrations and drUg dosages of gKX Guaifenesen is used to induce muscle relaxation and restraint as an adjunct to anesthesia in horses. GKX is made by combining 5% Guaifenesen (1 liter), Ketamine (1 gram) and Xylazine (500 milligrams). If the patient is a donkey or mule, it is recommended to double the dose of Ketamine (2 grams) and Xylazine (1 gram) because their metabolism is higher and they have an increased resistance to anesthetics. Anesthetic induction drugs used in various combinations to perform TIVA include: Xylazine (1.1 mg/kg IV [not to exceed 500 mg], ), Butorphanol (0.05 mg/lb IV), Diazepam (0.015 mg/lb IV), and Ketamine (2.2 mg/kg IV). Guaifenesen concentrations greater than 5% should be avoided to prevent hematuria. generaL Uses of gKX GKX anesthesia or "Triple Drip" can be used safely in surgeries or procedures that last less than 1.5 hours. GKX is an appropriate anesthesia choice as long as the horse is in good physical condition and laboratory bloodwork is within normal limits. Nasal oxygen should be supplemented at a rate of 5L/hr through an endotracheal tube. Some contraindications for using GKX include: surgeries lasting longer than 2 hours, neonatal patients, geriatric patients, and patients that have been administered any mood altering medications prior to hospitalization. Examples of surgical procedures commonly performed using GKX include arthroscopies, neurectomies, desmotomies, hernia repairs, cryptorchid castrations, and other shorter elective procedures. Pros and cons of gKX anesthesia GKX is more cost and time effective than inhalant anesthesia for short surgeries, and GKX is just as safe as inhalant anesthesia in healthy horses. Horses receiving GKX appear have smoother anesthetic recoveries when compared to horses being maintained on inhalant anesthesia. In addition, no anesthetic machine maintenance or soda lime monitoring is required with GKX. One-liter bags of Guaifenesen make it easier to store, calculate usage and hang from a pole. Furthermore, a one-liter bag of Guaifenesen is already reconstituted in comparison to bottles; therefore, warm water baths are not necessary to reconstitute Guaifenesin bags. Blood gases do not need to be performed under GKX in comparison to inhalant anesthetics; thus, another reason GKX is cheaper than inhalant anesthesia. Monitoring Patients Under gKX Direct blood pressure (IBP), electrocardiogram (EKG), pulse oximetry, physical parameters, eye position, mucous membrane color, capillary refill time, and direct evaluation are recommended to monitor patients while using GKX. If an arterial catheter is unattainable, then indirect blood pressure monitoring via an inflatable cuff (IBP) should be used. Blood pressure tends to run slightly higher than patients maintained with inhalant anesthesia. Horses will always have a palpebral and corneal reflex under GKX, unless the horse is in a deep plane of anesthesia. Indicators of a light patient include increasing respiratory rate, increasing blood pressure, increasing heart rate, and nystagmus. Attentive monitoring is imperative, as horses being anesthetized with GKX can change planes of anesthesia more rapidly than those being maintained with inhalant anesthesia. GKX anesthesia should be ran lighter plane of anesthesia if possible. Trainees should never take their eyes off the patient; not all patients react the same under anesthesia. Running TIVA or inhalant anesthesia is considered an "art" and requires a very observant person to run anesthesia successfully. driP rates for gKX A 15 drop/ml primary administration set should be used. Initially, bolus the GKX fro 1.5-2 minutes while attaching EKG and pulse oximetry leads. After the initial bolus, slow down to a moderate drip (~3 drops/second) while inserting the arterial catheter. Maintenance GKX drip rate should be between 2-3 drops/second; horses may require a higher or lower drip rate. If a horse gets too light, then a 1.5-3 ml Ketamine "bump" followed by a GKX bolus, will be necessary until the horse returns to a surgical plane of anesthesia. In general, most horses will require approximately about 1 liter/hour of GKX. anesthetic recoverY Butorphanol (0.45 mg/kg, IM) has proven to be very beneficial for pain management and a smoother anesthetic recovery. On average, anesthetic recovery time for horses anesthetized with GKX is 30 minutes; however, shorter anesthetic recovery rates are not uncommon. GKX recovery is generally very smooth in even in horses that have a poor anesthetic induction. Post- anesthetic hypothermia and/or muscle fasciculation is uncommon in horses anesthetized with GKX in comparison to horses maintained on inhalant anesthesia. g K X i n h o u S e O R f i e l d a n e S t h e S i a LISa MELOy, RVT Equine Sports Medicine and Surgery Submitted by Lisa Meloy, RVT at TEVA Platinum Practice, Equine Sports Medicine and Surgery in Weatherford, Texas

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