How to anaesthetize a giraffe

How to Anaesthetize a Giraffe* Important Principles 1. The large size of giraffe limits the ability of theatre personnel to physically control them during the delicate phases of induction and recovery. 2. The giraffe’s long neck acts as a lever arm and can be a source of danger to theatre staff as well as the patient itself. During the recovery period muscle spasms in the patient’s neck can be fatal. 3. Giraffe tend to vomit and regurgitate. This is most likely to occur upon induction from the increased intraabdominal pressure resulting from the patient impacting the ground since the skin and muscles over the abdomen are very tense. Opioids make this even more likely and a rumen bolus may be seen progressing up the neck as a precursor to a potentially fatal aspiration. 4. The posterior position of the larynx and their limited mouth opening makes intubating the giraffe technically difficult. Consequently this is rarely done. 5. Prolonged induction and anaesthesia can lead to hyperthermia, myopathy and secondary trauma. 6. Physiological adaptations of significance to the anaesthetist include hypertension, small respiratory tidal volume, large physiological dead space and low cardiac output during anaesthesia. You Will Need 1. An operating area with stable footing, smooth walls and very tall ceilings. A modified cattle crush with catwalk would be ideal. 2. At least four strong men in addition to the anaesthetist and surgical staff. 3. Several lengths of thick rope, a blindfold and earplugs. 4. A long spine board- a wide plank or Malibu surfboard will suffice as alternatives. 5. Anaesthetic agents (see below), dart gun, iv cannulae and infusion equipment. Preoperative Assessment and Preparation

1. Measure patient’s height and weight. If the latter is not feasible note the patient’s shoulder height in cm. 2. Ensure all theatre staff are fully briefed and prepared for the induction. Only experienced and physically fit staff should be involved. 3. Fast patient from food for 72hrs and from water for 48hrs. 4. Warn the patient’s carers of the high risk of perioperative morbidity and mortality- up to 10%. 5. Only book one case for the theatre session. Perioperative Management and Monitoring 1. Induction takes between 30minutes and an hour. Initial sedation is usually achieved with a sedative administered via dart gun. To induce recumbency further anaesthetic agents are given. It may be necessary to physically bring the giraffe down by casting it with a rope. 2. Especial care must be taken with regard to the patient’s neck. It must be supported by a long board so that the head is above the stomach. The neck should be extended to keep the airway patent and the nose pointed down to facilitate drainage of secretions. The angle of the neck is altered q10-15mins to prevent muscle spasms. 3. Blindfold the patient and apply earplugs. 4. Secure iv access- the jugular vein is the preferred site. 5. Apply standard monitoring: shave ear and apply pulse oximeter, place standard ETT in patient’s nostril and attach CO2 sensor to it, insert rectal temperature probe and apply BP cuff above the carpus. The pulse can be palpated in the auricular or mandibular artery.

6. Depth of anaesthesia monitoring can be facilitated by noting the patient’s response to hoof trimming.

7. Record the patient’s pulse, blood pressure, respirations

and oxygen saturation. Note that ET CO2 may not accurately reflect true arterial tensions. 8. Coordinate staff in preparation for emergence. Administer antagonist agents. 9. As the patient wakens, remove the blindfold and earplugs. Place a rope around the patient’s shoulders. Before attempting the final phase of the recovery ensure the patient has adequate muscle strength - this correlates with the patient’s ability to resist head restraint by lifting one man off the ground. Support the patient’s head and elevate the head as three assistants apply traction on the shoulder rope to assist the patient into the sternal position.

Anaesthetic Agents 1. Several combinations have been

2.

3. 4. 5.

used successfully. The first reported cases were with succinylcholine but there were significant problems associated with the use of this as a sole agent. Most experience is with a combination of xylazine, an α 2agonist and etorphine, an opioid. Atropine (7-8mg/ adult) is often given to prevent xylazine induced bradycardia. Giraffe are very sensitive to opioids and caution is mandatory with the use of these agents as they cause profound cardiorespiratory depression and can provoke vomiting and regurgitation. 5% glycerol glycolate has been used to deepen the anaesthetic and facilitate muscle relaxation. Anatgonists used to reverse xylazine include atipamezole, yohimbine and doxapram. Naltrexone is most commonly used to antagonize the opioids. More recently success has been reported with a combination of medetomidine (150mcg) and ketamine (3mg/ cm of shoulder height). Hyaluronidase was mixed in to facilitate absorption of the intramuscular injection. Opioids were required to supplement anaesthesia for major procedures, eg. Carfentanil. Again atipamezole was used to reverse the effects of the medetomidine.

*Why Giraffe? Because I like them, that’s why.