Practical therapeutics

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Although cats and dogs are physiologically similar in many respects, and dosing regimens recommended for dogs can frequently be extrapolated to cats, there are some important differences in drug disposition between the two species that can have a profound influence on dosing recommendations. This chapter covers the following: medication compliance, antibacterials, glucocorticoids, effective feline analgesia and effective sedation and anaesthesia. : Giving oral medications to cats.

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3.4 Antibacterial activity. Drug classes with NO clinical useful antibacterial action against most if not all bacterial species in different quadrants. Drug classes with EXCELLENT (green) or very good (blue) antibacterial action against many bacterial species in different quadrants. Drugs not designated as red, green or blue for a particular quadrant do have some activity in that quadrant but there are a reasonable proportion of bacterial species that will be resistant to that agent. This does not mean that such drugs are not clinically useful but they may not be the best choice if the therapeutic aim is to maximize antibacterial activity against bacteria in a quadrant because of the nature of the infection or the clinical status of the patient. Examples of such drugs are: 1st generation cephalosporins, cefovicin and amoxicillin (without clavulanic acid) against Gram-negative aerobes and obligate anaerobes; lincosamides (other than clindamycin) against anaerobes; trimethoprim/sulphonamides in all quadrants; and tetracyclines in all quadrants except Gram-positive aerobes (tetracyclines have excellent activity against ‘atypical bacteria’).
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3.10 This cat appears to be interested in its surroundings and is relaxed, suggesting that analgesia is adequate after an exploratory laparotomy 5 days earlier. The eyes are fully open and the ears are in a relaxed position, a facial expression that may be indicative of patient comfort. It is important to assess the response of the cat to application of gentle pressure around the site of surgery or tissue injury. Note that the cat’s facial expression remains relaxed during palpation and the body position appears relaxed and without obvious discomfort.
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3.11 A cat following repair of a fractured jaw. The cat had received an NSAID preoperatively, a mandibular nerve block with bupivacaine, and intravenous buprenorphine (20 µg/kg) at the end of surgery. On examination the cat was dull and unresponsive to interaction and had closed slanting eyes and very flattened ears. These facial characteristics are thought to indicate pain in cats. Additional analgesia with 0.3 mg/kg methadone (slow i.v. over 1–2 minutes) was given, and the cat then appeared more comfortable.
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3.12 An example of a pain scoring system for cats. The Colorado State University Feline Acute Pain Scale can be downloaded from the International Veterinary Academy of Pain Management website (www.ivapm.org). The scale should not be used as a definitive pain score, but it is useful to aid decision-making about the severity of acute pain in cats and the requirement for analgesic administration. In general: the assessment begins with quiet observation of the patient in the cage at a distance; this is followed by an assessment of the response of the patient to interaction, including the reaction to gentle palpation of a wound or painful area. Advantages of the scale include: ease of use, with minimal interpretation required; the provision of specific descriptors for individual behaviours decreases interobserver variability. A disadvantage of this scale is the lack of validation by clinical studies comparing it to other scales. (© 2006 PW Hellyer, SR Uhrig, NG Robinson)
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3.14 Oral transmucosal administration of buprenorphine. (Courtesy of Polly Taylor)
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3.16 Label syringes with the patient ID, drug name, infusion rate and concentration. This facilitates checking that the correct infusion rate has been set and reduces the likelihood of drug infusion errors (e.g. incorrect drug, dose or patient). When delivering more than one drug by CRI, administer them using different syringes and controlled infusion apparatus. This allows the dose rate of each drug to be adjusted independently and also prevents any risk of interactions between drugs caused by mixing in the same syringe or drip bag.
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3.17 When delivering more than one type of solution to a cat continuously (e.g. Hartmann’s solution and an analgesic drug) it is useful to use an intravenous extension line connected directly to the intravenous catheter, with two ports for drug administration. This allows both solutions to be administered directly, close to the intravenous catheter, preventing mixing of drugs in the fluid line. The ports are colour-coded to allow easy identification of the two lines and use a needleless injection system. This cat is receiving only fluids via one port on the extension set; the other port is for analgesic administration.
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3.25 This cat has been premedicated with acepromazine and buprenorphine and is receiving oxygen, using a breathing system connected to an anaesthetic machine, immediately prior to induction of anaesthesia with intravenous propofol. Flow rates of 2–3 litres/min will increase inspired oxygen concentration and are well tolerated by most cats.
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3.29 A pulse oximeter is being used to monitor haemoglobin saturation with oxygen (pO) in an anaesthetized cat; the probe is placed on the tongue. pO is 100% and heart rate is 161 beats/min. The cat is lying on warm bedding and covered with a blanket to support its body temperature.
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3.31 PVC endotracheal tubes with an internal diameter (ID) of 3.5 mm; one tube has a cuff while the other does not. The connector at the end of the tube allows a sampling line to be attached directly into the breathing system to sample airway gases for sidestream capnometry. Care must be taken when inflating cuffs of PVC tubes as overinflation can still lead to tracheal damage.
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3.32 A red rubber tube with a cuff.
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Image of View of the larynx. The tip of the epiglottis is visible ventrally in the midline; the laryngeal opening is the orifice in the midline caudal to the epiglottis.
View of the larynx. The tip of the epiglottis is visible ventrally in the midline; the laryngeal opening is the orifice in the midline caudal to the epiglottis. View of the larynx. The tip of the epiglottis is visible ventrally in the midline; the laryngeal opening is the orifice in the midline caudal to the epiglottis.
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Image of The Murphy’s eye at the tip of the tube is to allow a passageway for airflow should the lumen of the tube be obstructed by being positioned directly against the wall of the trachea.
The Murphy’s eye at the tip of the tube is to allow a passageway for airflow should the lumen of the tube be obstructed by being positioned directly against the wall of the trachea. The Murphy’s eye at the tip of the tube is to allow a passageway for airflow should the lumen of the tube be obstructed by being positioned directly against the wall of the trachea.
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3.34 An Ayre’s T-piece breathing system with a Jackson–Rees modification (the reservoir bag, C). The reservoir bag allows manual IPPV should respiratory support be required during anaesthesia. A connects to the ETT in the patient; B connects to the common gas outlet of the anaesthetic machine to supply fresh gases. The reservoir bag is to be connected to a scavenging system. Take care that the outlet of the reservoir bag does not become obstructed by twisting at this connection. Always check that the bag is emptying adequately; excessive bag inflation indicates that outflow from the bag is obstructed and this rapidly becomes very dangerous for the patient, as it causes increased expiratory pressure.
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3.35 A cat recovering from anaesthesia in an incubator to maintain body temperature. The cat is also receiving supplemental oxygen via a facemask, and a pulse oximeter is being used to measure pO via a probe placed on the tongue. Intravenous fluid therapy is being delivered via an indwelling catheter in the medial saphenous vein.
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3.39 An example of an anaesthetic record. This form allows patient details to be recorded as well as information about premedication (drug, dose, route of administration, time of administration), induction agents, and other drugs given during anaesthesia and fluid therapy. The graphical format for recording changes in physiological variables facilitates early detection of changes. (Courtesy of Langford Veterinary Services)
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3.40 Eye position and depth of anaesthesia. Ventromedial rotation of the eye at a light to moderate depth of anaesthesia with isoflurane. The blink reflex had been abolished. Further ventromedial rotation of the eye as depth of anaesthesia increases. Surgery is usually possible when both eyes show this degree of ventromedial rotation and the blink reflex is abolished. However, eye position alone should not be relied upon; a combination of signs (e.g. eye position, blink reflex, heart and respiratory rates) should be used.
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3.41 Pulse palpation. Femoral: in this image the pulse is being palpated on the medial aspect of the right thigh caudal to the femur. Sublingual artery. The tongue is gently extended and the fingertips used to palpate the artery as it runs on the ventral midline of the tongue. Pressure should be gentle; excessive pressure will occlude the vessel so that the pulse is no longer palpable. Metatarsal artery, running craniomedial to the hock. The left hand of the anaesthetist is holding the limb in gentle extension at the tip of the toes. Overextension of the limb would make the metatarsal artery very difficult to palpate.
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3.42 Many cats will tolerate pulse oximetry via the ear pinna, and this site can be very effective if the pinnae are unpigmented and relatively unhairy. This cat is awake and receiving oxygen supplementation in an oxygen cage with a covered front.
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3.43 ECG monitoring via electrodes placed on the metacarpal/metatarsal pads of the left and right forelimbs and right hindlimb. For the purposes of monitoring heart rhythm during anaesthesia the precise electrode configuration is not important. For example, if surgery were being carried out on the right forelimb, the electrodes could be placed on the left forelimb metacarpal pad and right and left hindlimb metatarsal pads. On the right forelimb it can be seen that the gel pad of the electrode is positioned against the metacarpal pad; the ECG lead clips directly to the electrode via a metal pin.
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3.45 An oesophageal temperature probe (A) has been placed in this cat. The tip of the probe lies in the distal oesophagus (approximately level with the heart base). The probe has a thermocouple at the distal end, and is connected to a multi-parameter monitor that gives a continuous reading of body temperature.
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3.46 Sidestream capnometry. The sampling line delivering airway gases from the respiratory system to the capnometer is connected to the endotracheal tube via a low dead space connector (A). The sampling line (B) is connected to the capnometer module of the multiparameter monitor and produces a continuous capnogram trace (C) showing changes in end-tidal CO concentration during inspiration and expiration.
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3.49 An example of a flow chart for carrying out CPR (assuming that no defibrillator is available).
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3.51 Anaesthesia protocols for prepubertal castration or ovariohysterectomy in kittens. The authorized alternative uses butorphanol at 0.4 mg/kg instead of buprenorphine.
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Pill crushers and pill splitters Pill crushers and pill splitters
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