Chapter 1
General Considerations and Anaesthesia

1. 1.1 Pre-operative assessment
2. 1.2 Instrumentation
3. 1.3 Asepsis
4. 1.4 Sutures and suturing
5. 1.5 Restraint
6. 1.6 Pre-medication and sedation
7. 1.7 General anaesthesia
8. 1.8 Local analgesics
9. 1.9 Regional analgesia

1.1 Pre-operative Assessment

Introduction

The bovine patient is a stoical animal and modern crushes and physical restraint options allow many techniques to be carried out in the field. However, this should not excuse a thorough clinical and ethical assessment prior to any surgical procedure.

Assessment should include numerous factors apart from the physical condition of the subject:

• welfare implications of the procedure
• potential duration of a productive life
• economic situation including insurance status and economic return on the surgery
• surgical risk regarding complete recovery
• future breeding prospects including heritability of the condition being corrected
• pathology of other body systems directly or indirectly related to the primary condition

General physical examination is essential before emergency or elective surgery to assess risks and concurrent disorders.

Welfare and Quality of Life

Animal welfare may be judged using a number of criteria. Making these judgements is an essential part of the vet's role. Vets must also lead by example. Decisions to perform surgery, and how it is to be done, are complex. Foremost in the process must be the welfare of the cow or calf. The surgeon should ask themselves:

• How necessary is this procedure: will benefits to the animal outweigh any pain or discomfort?
• What will the animal's quality of life be afterwards? Is the procedure likely to lead to a 'life worth living' or preferably 'a good life' for the animal in question?
• How does this procedure compare with an alternative option of humane slaughter or euthanasia?
• To what extent can pain and discomfort be mitigated during and after the procedure?
• To what extent can fear and distress be mitigated during and after the procedure?
• What can we learn from this situation to make life better for cows and calves in the future?

The last question is vital: sometimes it is easy for the surgeon to focus on the individual animal in question (that is important too) but lose sight of the greater picture. For example: performing surgery on a cow with toe necrosis can greatly improve her quality of life, but what measures can be put in place to prevent further cases? You are asked to dehorn or castrate some yearling cattle: could it be done at a younger age next time?

Warning

Some procedures are deemed to be simply unethical and there is legislation in place preventing them, though there are regional variations. Examples in the UK of illegal procedures include:

• tail docking in calves or adult cattle (except in cases of injury)
• castration over one week by means of an elastrator
• castration without anaesthetic for animals over two months of age

Furthermore, the Veterinary Surgeons Act means that any surgery involving entering a body cavity (e.g. joint spaces; abdomen; thoracic cavity) can only be carried out by a qualified veterinary surgeon in the UK. It is incumbent on the vet to provide suitable anaesthesia and analgesia.

Anaesthesia techniques are described in Section 1.7-1.9. Peri-operative analgesia is discussed in Section 2.11, though there is clearly overlap in these two areas of pharmacology and surgical preparation. The use of a crush/squeeze chute should never replace adequate analgesia and sedation for surgical procedures.

Tip

Learn and practice good communication techniques. Effective communication between farm vet and producer is vital to ensure that pain and suffering are reduced to a minimum among stock. Vets should be the leaders in animal welfare: this leadership requires exact personal skills, which is in addition to any technical abilities or scientific knowledge required of vets.

Laboratory Tests

Under farm practice conditions laboratory tests may not be performed, but major parameters very simply estimated with minimal apparatus are:

• packed cell volume: microcentrifuge, microhaematocrit apparatus
• total protein: refractometer

Normal haematological and biochemical parameters of cattle are listed in Table 1.1.

Table 1.1 Reference ranges (haematology and plasma biochemistry) in cattle.

Units Average (%) Range (± 2SD) Haematology Erythrocytes ×1012/l 7.0 (5-10) Haemoglobin g/dl 11.0 (8-15) PCV (haematocrit) 1/l 35.0 28-38 Fibrinogen g/l 4.0 (2-7) Leucocytes ×109/l 7.0 (4-12) Neutrophils (non-segmented bands) ×109/l 0.02 (0.5%) 0-1.12 (0-2%) Neutrophils (segmented mature) ×109/l 2.0 (28%) 0.6-4 (25-48%) Lymphocytes ×109/l 4.5 (58%) 2.5-7.5 (45-75%) Monocytes ×109/l 0.4 (4%) 0.02-0.8 (2-7%) Eosinophils ×109/l 0.65 (9%) 0-2.4 (0-20%) Basophils ×109/l 0.05 (0.5%) 0-0.2 (0-2%) Neutrophil: lymphocyte ratio - 0.45?:?1 - Plasma biochemistry Urea mmol/l 4.2 2.0-6.6 Creatinine µmol/l 100 44-165 Calcium mmol/l 2.5 2.0-3.4 Inorganic phosphate mmol/l 1.7 1.2-2.3 Sodium mmol/l 139 132-150 Potassium mmol/l 4.3 3.6-5.8 Chloride mmol/l 102 90-110 Magnesium mmol/l 1.02 0.7-1.2 Total protein g/l 67 51-91 Albumin g/l 34 21-36 Globulin g/l 43 30-55 Glucose mmol/l 2.5 2.0-3.2 Alkaline phosphatase iu/l 24 20-30 AST SGOT iu/l 40 20-100 ALT SGPT iu/l 10 4-50 Lactate dehydrogenase (LDH) iu/l 700 600-850 Bilirubin µmol/l 4.1 0-6.5 Cholesterol mmol/l 2.6 1.0-3.0 Creatine phosphokinase mmol/l 3.0 0-50 The above values refer to healthy adult (> 3 years old) cattle, and have been compiled from various sources. Interpretation of possible deviations from the above ranges should consider variations due to the laboratory technique, breed, lactational and nutritional status, and should always be related to the presenting signs and symptoms of the individual or group. Units are given as SI units

In some abdominal conditions (abomasal torsion or volvulus, intestinal obstruction) estimation of plasma electrolytes (e.g. chloride) is valuable in assessing prognosis and calculating requirements for fluid replacement. Fluid therapy is discussed in Chapter 2.

Congenital Defects

Incidence of congenital defects in cattle is 0.2-3%, with 40-50% born dead. Most defects are visible externally. Congenital defects reduce the value of affected calves and economic losses are most severe when combined with embryonic or foetal mortality, particularly if it results in an extended subsequent calving interval. Close collaboration between the vet, farmer and geneticist is essential and good breeding records are vital.

Tip

'Congenital' is not synonymous with 'heritable' or 'genetic'. Where it is likely that the condition is inherited, steps should be taken...