Recovery from anaesthesia
General:
The recovery period is a critical phase of any anaesthetic and deaths can and do occur at this stage. Considerable thought should be given to the conditions and location in which tigers are expected to recover, and if safe, to monitoring them until fully mobile again. It is important to move a tiger to a safe place for recovery at the beginning of anaesthesia because it may not be possible to do so when it starts to recover. Anaesthetising more than one tiger at a time can create difficulties in the recovery phase as monitoring multiple recoveries or resolving problems in more than one animal could be extremely challenging – especially if one individual recovers faster than another.
Ideally, all animals should be allowed to recover undisturbed in quiet, dimly lit conditions within an area free from physical hazards. This will be extremely difficult to achieve in practice. Most tigers will stagger somewhat as they attempt to move away, and potential environmental hazards (water, risk of falling, etc.) in the immediate environment must be assessed and dangers mitigated. Precautions must be taken to prevent tigers overheating during recovery or from becoming too cold depending on the prevailing weather. Eyes should be protected from direct sunlight and the entire body should be shaded during recovery in hot conditions.
Tigers should be placed on their side for recovery, with the shoulders slightly higher than the rear end (to avoid abdominal contents pressing on the diaphragm), and head and neck extended with the nose positioned lower than the back of the head so that any secretions or regurgitated ingesta can drain away from the larynx. If the tiger allows, the tongue should be extended and left protruding from the mouth. (This encourages saliva to drain away from the mouth and allows the anaesthetist to observe the colour of mucous membranes during recovery).
Before leaving a tiger to recover final checks on its vital signs should be made using the ABC approach (See monitoring section). Particular attention should be paid to ensuring that the airway is clear – making sure that excessive amounts of saliva and any food material, foreign bodies etc are removed from the mouth and pharynx. Monitoring of pulse, respiration and temperature should continue until it is no longer safe to do so, or until such interference disturbs the animal. Discrete observation from a distance can be aided with binoculars. In poor light conditions it is easier to see the breathing if some light-coloured material has been placed on the chest. For safety reasons, the area should be vacated before the tiger becomes mobile enough to pose a danger to field staff.
Anaesthetic reversal drugs:
When medetomidine or xylazine have been used, recovery can be hastened by the use of intramuscular atipamezole. Between 3 and 5 mg atipamezole are given for each mg of medetomidine in the induction dose. When used to reverse xylazine 1 mg atipamezole is given for every 10 mg xylazine used.
Reversal of medetomidine (or xylazine) and ketamine anaesthesia with atipamezole within 30 minutes of induction creates a greater likelihood of excitement, hallucinations, ataxia and excessive salivation on recovery – a situation that increases the probability of tigers injuring themselves at this stage. These effects are due to residual ketamine as only the medetomidine (or xylazine) is reversed. Therefore, it is always best to wait for a full 45 minutes before reversal is attempted unless an emergency situation arises.
In emergencies, or when the anaesthetist is keen to accelerate recovery for whatever reason, atipamezole can be given intravenously or split between the intravenous and intramuscular routes. Safety issues that may follow sudden recovery after intravenous atipamezole must be considered in advance! Tigers occasionally vomit on recovery following atipamezole. Some individuals show a tendency apparently to sleep after a complete recovery but are aroused by the slightest stimulus.
Transportation of anaesthetised tigers:
Tigers should not be transported in crates, boxes, etc., until they have fully recovered from an anaesthetic. It is all too easy for an anaesthetised cat to be thrown into an awkward position in the crate by the motion of the vehicle, which may lead to a respiratory obstruction and eventually death. Inhalation of vomit or regurgitated stomach contents can also occur in the anaesthetised or semi-anaesthetised tiger during transport, leading to respiratory obstruction or inhalation pneumonia. In extreme circumstances transport over rough roads could throw an anaesthetised animal in its crate violently enough to fracture its neck or other bones. If transport under anaesthesia is absolutely necessary, the tiger should be under direct but discrete observation at all times to avoid these problems.