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O. Louise1
1VetsNow, Anaesthesia & ECC, Manchester, United Kingdom
Louise O’Dwyer MBA BSc (Hons) VTS (Anesthesia&ECC) DipAVN (Medical & Surgical) RVN
Clinical Support Manager, VetsNow, Manchester, U.K.
All orthopaedic procedures are not necessarily considered an emergency, and in patients that have sustained traumatic orthopaedic injuries surgery, and therefore anaesthesia, is likely to be postponed until the patient is considered stable, and concurrent injuries,
e.g. pulmonary contusions, hypovolaemic shock, have been corrected. It should be remembered that some fractures can result in significant blood loss, particularly pelvic or femoral fractures, and so hypovolaemia and anaemia, are always a concern in these patients, either on presentation, or a few days post-trauma, therefore assessment of the patients haemodynamic status should be assessed and corrected prior to anaesthesia, along with treatment of anaemia if required.
As well as initial stabilization, any fractured limbs or wounds should be appropriately dressed, and wounds debrided if open fractures are present. Placement of supportive dressings in patients with fractures will result in some pain relief due to reducing movement and dislocation of bone fragments, along with preventing further trauma of the limb.
Once the patient is deemed suitably stable for anaesthesia then a plan can be created. The premedication combination will be determined by the individual patient’s status, but commonly will be a combination of a sedative (acepromazine or an alpha 2 agonists at low doses) and a pure opioid (methadone) are appropriate choices. An appropriate opioid is used to provide analgesia, muscle relaxation and sedation, whilst its combination with a sedative will allow a reduction in the dose of both induction and inhalation agents. For induction of anaesthesia most of the commonly used short acting induction agents are appropriate, e.g. propofol or alfaxalone. Anaesthesia is then maintained using either isoflurane or sevoflurane administered, remembering both these agents result in a dose- dependent decrease in cardiac output and therefore blood pressure, so careful monitoring is required.
Effective analgesia is essential in all patients, but in patients that have sustained traumatic injuries pain
can have severe effects on multiple organ systems. Inappropriately treated pain makes trauma patients more prone to systemic inflammatory response syndrome (SIRS), immunosuppression, sepsis, and long-lasting maladaptive pain.
Pain has negative effects on wound healing, with greater post-surgical pain being associated with delayed wound healing and also increasing serum cortisol levels which again will impair wound healing.
Overall a multimodal approach to analgesia in trauma patients should be used. By utilizing analgesic agents that act on different points on the pain pathway, along with agents that work synergistically, we can reduce the dosages and therefore side-effects associated with individual drugs. Opioids are an excellent choice for orthopaedic patients as they are effective, titratable, and reversible whilst having minimal cardiovascular side effects. Another group of agents worth considering
are local anaesthetics, which can be used as part of a regional block.
Placement of Local Anaesthetic Blocks
The use of local anaesthetic blocks as part of a multimodal approach to analgesia, is potentially the
most effective form of analgesia for many small animal surgeries, but also, for the majority of veterinary clinics, the most underused. For the majority of the blocks
that will be discussed all that is needed is a syringe, a needle, local anaesthetic and a knowledge of the relevant anatomy. Technically these blocks do not require any specialist equipment, but nerve location equipment is recommended to guide perineural injections of local anaesthetics.
Local anaesthetic blocks can be used to enhance analgesia whilst the animal is under general anaesthesia, this means that less volatile agent will be required
to maintain anaesthesia, and is likely to result in
a ‘smoother’ anaesthetic. Local anaesthesia can
also be used in sedated or occasionally conscious patients in order to allow minor surgical procedures or manipulations to be performed. Local anaesthetics are the only class of analgesics that are true analgesics, in that they completely block pain sensations, all the other drugs that are considered to be ‘analgesics’. Local anaesthetic drugs block pain because the stop the nerves conducting the pain signals and so work on the transmission part of the pain pathway.
When performing any of the local blocks, aspiration to check for blood, following needle insertion, but
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