**11. Local anesthesia for vessel puncture**

248 A Bird's-Eye View of Veterinary Medicine

Behavioural and physiological evidence suggests that pain and beak sensitivity persists for weeks or months after trimming (Craig and Swanson, 1994). A local analgesic (bupivacaine and diethyl sulfoxide) administered to the cut beak of 6-week-old chicks after trimming prevents at least some of the acute pain and the reduction in feed intake usually seen in the

In many countries, laboratory animals (mainly rodents) but also farm animals (mainly

Experiments conducted on farm animals may cause pain which ought to be eliminated or

The suffering associated with surgical procedures may be prevented with the use of local anaesthetics. Most of them, if injected or inhalated, have an effect on physiological functions of animal body which may distort the results of an experiment, but this is also true for the pain which triggers stress reaction. The experiments may be performed without anaesthesia

Reliable results of experiments on farm animals are largely dependent on the standardisation of the factors affecting physiological reactions of these animals and on the broad idea of their wellbeing. The main factors influencing the quality of experiments conducted on farm animals include: their biological status (sex, age, body mass); health condition; nutrition; maintenance conditions; animal headquarters (ventilation, temperature, humidity, lighting, noise); exposure to stressogenic stimuli; proper care; the choice of appropriate experimental techniques. Meeting these requirements allows to obtain

Experiments conducted on animals often require blood sampling. It is important to safeguard the welfare of farm animals from which blood is harvested for research purposes. Contemporary animal welfare requirements are more stringent than they have been in the past, and it is appropriate that there should be guidelines to protect the welfare of animals

For the research purposes, blood harvesting usually implicates the removal of a relatively large volume of blood over a short period of time, i.e. more than would usually be required

It is in the interests of good science as well as the welfare of the animals used that stress on the animals is kept to a minimum. If the process of harvesting is stressful for the animal because of handling, pain or discomfort, physiological changes occur which may

Although local areas of anaesthesia can be produced by subcutaneous injection of local anaesthetics, the process of injection may itself cause pain. A number of attempts have been

made to obtain suitable formulations for effective topical application to the skin.

first 24 hours after trimming.

used in blood harvesting operations.

compromise the quality of the scientific result obtained.

or routine diagnostic tests.

**10. Topical anesthetics** 

**9. Using farm animals for experimental purposes** 

reduced to minimum for ethical and scientific reasons.

horses, cattle, sheep and goats) are used in research, testing and teaching.

only in exceptional cases, when it is necessary from the scientific point of view.

repeatable, reliable results of experiments and to create proper living conditions.

Pain associated with vessel puncture has long been accepted as an unavoidable consequence of blood collection and intravenous drug administration. The degree of pain associated with the procedure is believed to be minimal, provided that a fine gauge needle is used and that the animal is expertly restrained and the operator skilled in the technique.

In many instances, however, it is necessary to use larger gauge needles and this may produce a detectable reaction from the animal. Such responses are also noted more frequently when over-the-needle type cannulae are inserted to provide long-term vascular access.

When vessel puncture is undertaken by relatively inexperienced staff, repeated attempts may be necessary before the procedure is carried out successfully. Under these circumstances, the animal may experience greater pain or discomfort than when the technique is undertaken by a skilled operator.

There has been considerable debate as to the nature of pain in animals, since it is unclear what form animal experiences may take. It has been suggested that one constructive approach is to accept that animals are capable of sensory experiences which, given the opportunity, they avoid and which modify their biochemistry, physiology, and behaviour in a species-specific way. Many of the stimuli that produce these reactions in animals would produce the sensation described as pain in man, and hence nociceptive reactions in animals such as withdrawal of the limb, vocalizations and aggressive behaviour may be interpreted as one type of response to pain.

In human anaesthetic practice, it has been demonstrated that pain caused by the intravessel insertion of needles and cannulae can be alleviated by the topical application of local anaesthetic cream. The feasibility of using a similar technique in animals has been shown.

A commercially available local anaesthetic cream (EMLA®) can be used for application prior to vessel puncture in farm animals. EMLA cream consists of a eutectic mixture of lignocaine base (25 mg/ml) and prilocaine base (25 mg/ml), together with an emulsifier, a viscosity increasing agent and water and with the pH of the cream adjusted to pH 9,4 with sodium hydroxide.

Local Anesthesia for Husbandry Procedures and Experimental Purposes in Farm Animals 251

1% of body weight is the weight of 16 to 17% of the circulating blood volume in sheep and

If more than 15% of blood volume is removed, consideration should be given to fluid

For young animals, the volumes removed should be relatively less. For animals 6 months old, not more than 10% circulating blood volume should be removed, with incremental increases to the maximums above when fully grown (more than 12 months old for sheep

If too much blood is drawn too quickly or too frequently without replacement, animals may develop hyperpnoea (deep and rapid breathing) and may go into a state of hypovolaemic shock. In the longer term the removal of to much blood causes anaemia, muscle weakness, increased susceptibility to cold, reduced exercise tolerance and ill-thrift, particularly if

If 15% to 20% of the blood volume is removed, cardiac output and blood pressure will be

Inexpert bleeding techniques can result in bruising around the vein, haematoma formation

Blood can be collected from the jugular vein in cattle of all ages or from the tail (coccygeal)

A variety of collection devices may be used: vacutainers, bleeding tubes, syringe and needle. Restraint should ensure quick, easy and safe collection of the sample causing minimal

This may involve use of a bail, race, or crush for tail bleeding. For jugular bleeding the animal may require minimal restraint (e.g. halter) or may need to be restrained in a crush with head bail and the employment of a halter or nose grips. Use of nose grips should be

Operators should use gloves and disinfect them between animals to prevent the transmission of blood-borne diseases. Equipment such as vacutainer holders should also be

Jugular bleeding - The animal must be restrained with the head elevated and the jugular groove exposed. The jugular vein is raised by pressure at the base of the jugular groove. The needle is passed through the skin and into the vein by a firm thrust directed an angle of 20o

Tail bleeding - Restraint should prevent the animal from moving away during the procedure.

Approximately 150 mm from the base of the tail, the groove lying in the ventral midline of the tail is located. Midway along the body of a coccygeal vertebra, the needle must be inserted perpendicularly to the surface of the skin to a depth of a few millimetres and the

The tail must be raised vertically with one hand until it is horizontal with the ground.

cattle; about 13% in horses and about 14% in goats.

management and nutrition are suboptimal.

and/or inflammation at the site.

vein of older cattle.

avoided wherever possible.

cleaned between animals.

distress.

**12.1 Bleeding technique in cattle** 

reduced. Removal of 30% to 40% can induce shock.

to the skin surface and the blood sample is withdrawn.

replacement using lactated Ringer's solution with 5% dextrose.

and goats, 18 months old for cattle and 3 years old for horses).
