Overview
This series of articles provides guidance and information to individuals who will undertake surgical procedures on animals as part of their research work. These articles should be read in conjunction with the ones in Anaesthesia for Minor Procedures (EU20) and Advanced Anaesthesia for Surgical or Prolonged Procedures (EU21) since these provide more detail on preoperative and postoperative care of animals.
Additional information on specific surgical procedures can be found in Waynforth and Flecknell (1992), Rigalli, A and Di Loreto, (2009), and a range of veterinary texts. Video tutorials are also available to assist with specific procedures (e.g. telemeter implantation).
Aims of experimental surgery
In contrast to the aims of surgery carried out for veterinary or medical purposes, experimental surgery aims to produce a carefully defined animal model in order that a disease, condition or basic anatomical/physiological feature may be studied in vivo. In order to achieve this, the same principles that apply to veterinary or medical surgical procedures must be adopted. These general principles – “Halsted’s principles” – lay out clear guidelines that must be followed to optimise the outcomes of surgery:
- Handle tissues gently
- Be meticulous in controlling haemorrhage
- Preserve the blood supply to the tissues
- Observe strict aseptic technique
- Apply minimal tension to tissues
- Ensure tissues are accurately apposed
- Obliterate dead space
(Definition: Dead space: space remaining in tissues as a result of failure of proper closure of surgical or other wounds, permitting accumulation of blood or serum.)
Failure to follow these principles results in a range of complications, for example:
- Trauma to tissue releases inflammatory mediators that increase post-operative pain, alter the animal’s physiology and metabolism, and may have specific influences on particular research protocols.
- Areas of tissue starved of oxygen with consequent delayed healing will lead to wound breakdown.
- If dead space is left in tissues that are not repaired effectively, tissue fluid and blood will accumulate, and post-operative infection rates will increase.
- Wound contamination at the time of surgery will lead to further problems with infection and wound breakdown.
These problems will result in animals experiencing unnecessary pain, suffering and distress, leading to compromised animal welfare, as well as the production of an ill-defined animal model. The increased variability in the animals following surgery will require larger experimental groups, and unexpected losses of animals because of surgical complications leads to both a waste of animals, and a waste of resources. Good surgical technique therefore offers opportunities to apply Refinement and Reduction to your research work.