Flank Aesthesia In Bovine

1. Flank Aesthesia
In Bovine

2. Inverted L block
Infiltration of the skin, subcutaneous and deeper tissues in an inverted L shape
with 60 ml of 2% lignocaine solution is a commonly used technique to provide
analgesia for a flank laparotomy in a standing cow .

3. • It is also used in recumbent animals to block the site for a paramedian incision, or repeated
in a mirror image to form a U shape and analgesia for a midline incision. Injections must be
made both subcutaneously and down to the peritoneum to produce a total block. The block
can be achieved by making isolated injections at intervals of about 1 cm, which relies on
lateral diffusion of the analgesic solution.Alternatively, a wall of local analgesic solution can
be created by inserting a long needle to its depth,and injecting anaesthetic solution in a
steady stream as the needle is withdrawn.require additional desensitization of the dorsal
nerves cranial to the thirteenth. The last dorsal and first lumbar intervertebral foramina in
cattle are occasionally double. The last dorsal foramen lies immediately caudal to the head
of the last rib and on a level with the base of the transverse process of the first lumbar
vertebra.

4. Paravertebral nerve block
• Paravertebral block involves the perineural injection of local analgesic solution about the
spinal nerves as they emerge from the vertebral canal through the intervertebral
foramina. This technique is commonly used to provide analgesia forlaparotomy. It offers
a major advantage over use of field infiltration in that the abdominal wall including the
peritoneum is more likely to be uniformly desensitized. Additionally, the abdominal wall is
relaxed. he area of the flank bounded cranially by the last rib, caudally by the angle of
the ilium and dorsally by the lumbar transverse processes, is innervated by the thirteenth
and first and second lumbar nerves. In addition, the third lumbar nerve,n although it does
not supply the flank, gives off a cutaneous branch which passes obliquely backwards in
front of the ilium. Operations involving the ventral aspect of the abdominal wall will

5. The lumbar foramina are large and are situated between the base of the transverse
processes and approximately on the same level. The spinal nerves, after emerging
from the foramina, immediately divide into a smaller dorsal and a larger ventral branch.
The dorsal branch supplies chiefly the skin and muscles of the loins, but some of its
cutaneous branches pass a considerable distance down the flank. The ventral branch
passes obliquely ventrally and caudally between the muscles and comprises the main
nerve supply to the skin, muscles, and peritoneum of the flank The ventral branch is
also connected with the sympathetic system by a ramus communicans. Paralysis of
the nerves at their points of emergence from the intervertebral foramina will provoke
desensitization of the whole depth of the flank wall and complete muscular relaxation.
Block of
the rami communicantes will result in splanchnic vasodilatation and potential for
hypotension. The number of nerves to be blocked will depend on the site and extent of
the proposed inci
sion. The areas involved by blocking of respective nerves are illustrated in Fig. 12.5.

6. • Therefore, for rumenotomy, using an incision parallel with and about 7 cm caudal to
the last rib, analgesia of the thirteenth thoracic and first and second lumbar nerves is
required. The third lumbar nerve must be blocked for a more caudal incision and for
relaxation of the internal oblique muscle. A number of different techniques for blocking
the respective nerves have been described but the most reliable relies on directing
the needle towardsthe cranial border of the transverse process of the vertebra behind
the nerve to be blocked. For example, to block the 1st lumbar nerve the needle
should be directed to strike the cranial broder of the 2nd lumbar vertebra about 5–6
cm from theanimal’s midline. At such sites the cranial borders of the transverse
processes are usually in the same cross sectional plane of the body as the most
prominent parts of their lateral borders. To block the thirteenth thoracic and first,
second and third lumbar nerves skin weals should be raised in line with the most
obvious parts of the transverse processes of the second, third and fourth lumbar
vertebrae, 5–6 cm from, the midline of the body. Location of the transverse process of
the first lumbar vertebra is usually difficult (particularly in well-muscled or obese
animals) so in most cases the site for infiltration around the thir

8. • teenth thoracic nerve is found by simple measurement. The distance between the skin weals over the second and
third lumbar transverse processes is measured and another skin weal is produced at a distance equal to this,
cranial to the anterior weal, to mark the site where the needle is to be introduced to strike the cranial border of the
first lumbar transverse process. A stout needle (7 cm long, 3 mm bore) is inserted through each skin weal and the
underlying longissimus dorsi muscle infiltrated with 2–3 ml of 1% lignocaine (lidocaine) or other local analgesic
solution as they ar advanced to a depth of about 4 cm from the skin surface. This infiltration is omitted by some
workers but it does serve to counteract spasm of the longissimus dorsi during the subsequent insertion of the
longer needle used to deposit analgesic solution around the main nerve trunks. The needles used for injection
around the nerves (10 cm long, 2 mm bore) are introduced, after an appropriate pause, through the holes made
in the skin by the stout needles used for infiltration of the longissimus dorsi muscle, and advanced to strike the
anterior border of the transverse process. Each needle is then redirected cranially over the edge of the transverse
process and advanced until it is felt to penetrate the intertransverse ligament. Penetration of the intertransverse
ligament is made more obvious if the needles used have ‘shortbevel’ points. Injection of 15 ml of local analgesic
solution is made immediately below the ligament and a further 5 ml is injected as the needle is withdrawn to just
above the ligament. During final withdrawal of the needle the skin is pressed downwards to prevent separation of
the connective tissue and aspiration of air through the needle. It is important to ensure that the needles shall be
vertical when contact is first made with the cranial border of the transverse processes for, if they are not,
redirection over the edge of the processes may cause their points to lie well away from the course of the nerves.
Successful infiltration around the nerves is indicated first by the development of a belt of hyperaemia which
causes a distinct and appreciable rise in skin temperature. Full analgesia develops in about ten minutes and
when lignocaine with adrenaline 1:400 000 is used it persistsfor about 90 minutes. When a unilateral block is fully
developed it produces a curvature of the

9. • spine, the convexity of which is towards the analgesic side (Fig. 12.6). An alternative method of
lumbar paravertebral block utilizing a lateral approach to the nerves is favoured by some. About 10
ml of local analgesic solution is injected beneath each transverse process towards the midline. The
needle is then withdrawn a short distance and then redirected first cranially, then caudally, with
more analgesic solution being injected along each line of insertion.A total of about 20 ml of solution
is used for each site and the last portion of each 20 ml is injected slightly dorsal and caudal to the
transverse process to block dorsolateral branches of the nerves. With this technique analgesic
solution maybe injected below fascial sheets and thus be prevented from bathing the nerves. It is
inevitable that failure or at least partial failure will sometimes attend attempts to inject local
analgesic solution in the immediate vicinity of a series of nerves situated at a depth of 5–7 cm from
the body surface, however careful the technique of injection and no matter which approach is
adopted. Among the factors which reduce the precision of the method are: the nerves traverse the
intertransverse spaces obliquely; in some ani the nerve roots are double, emerging from double
foramina; it is difficult to ensure that the site of injection is the same as that assessed from the body
surface; penetration of the muscular mass of the back tends to cause spasmodic contraction of the
muscles with consequent modification of the needle track. Precise location of the injection sites is
also more difficult in the newer large breeds of cattle.

11. Caprine Flank
Anesthesia

12. Paravertebral nerve block
• In sheep and goats lumbar paravertebral nerve block is carried
out using techniques similar to those employed in cattle. For
operations carried out through the flank the thirteenth thoracic
and first three lumbar nerves are blocked. For each of these
nerves up to 5 ml of 1 or 2% lignocaine is used, divided and
injected above and below the intertransverse ligament, up to a
maximum total dose of 6 mg/kg lignocaine. Onset of analgesia
may be as fast as 5 minutes. Duration of analgesia is an hour,
or longer when lignocaine with adrenaline is used.

13. • Flank laparotomy can be performed using local infiltration
of lignocaine in an inverted L pattern 2 to 3 cm cranial and
dorsal to the intended skin incision site. Blebs of
lignocaine must be injected subcutaneously and deep in
the abdominal muscle at approximately 1.5 cm intervals
along the injection site. The maximum dose of lignocaine
to be injected at one time is 6 mg/kg and dilution of 2%
solution to 1% solution may be necessary to provide
sufficient volume for injection. The duration of analgesia is
about 1.5hours.

14. Epidural block
• Epidural block can be produced by injection of local anaesthetic solution into
the epidural space at the lumbosacral junction. Complete analgesia and
paralysis can be induced in the hindlimbs and abdomen to allow surgery,
depending on the volume of local anaesthetic injected (Trim, 1989). The dose
rates for different drugs and their times for onset of action are listed in Table
13.1. The doserates listed are to produce analgesia for flank laparotomy. The
dose should be decreased if theanimal is old, obese, or pregnant. A lower
dose of lignocaine, such as 1 ml/7 kg, is sufficient for perineal or hindlimb
surgical procedures, and for caesarian section. The long duration of hindlimb
paralysis from bupivacaine block for caesarian section interferes with nursing
of the newborn, and for that reason lignocaine with adrenaline isusually
preferred.

15. • The lumbosacral junction is easy to palpate in thin animals but recognition of landmarks will
benecessary to identify the point of needle insertion in muscled or fat animals. Epidural block can be
performed with the goat or sheep standing or in lateral recumbency. An imaginary line between the
cranial borders of the ilium crosses between the spinous processes of the last lumbar vertebrae(Fig.
13.3). The caudal borders of the ilium, where the angle bends to parallel midline, are level withthe
cranial edge of the sacrum. The point of needle insertion is midline halfway between the spinousm
process of the seventh lumbar vertebra and the sacrum. If the spinous process of the last lumba
vertebra can be palpated, the next depression caudal to it is the lumbosacral space. This area must
be clipped and the skin prepared with a surgical scrub. A spinal needle should be used because it
has a stilette to prevent injection of a core of subcutaneous tissue into the epidural space. The notch
on the hub of the needle indicates the direction of the bevel. Thus the anaesthetist can ensure that
injection of local anaesthetic solution is towards the head of the animal. When epidural nerve block is
to be performed on the conscious animal, 1–3 ml 2% lignocaine should be injected subcutaneously
with a fine needle at the site intended for insertion of the spinal needle. For lambs, kids, and pygmy
goats, a 22 gauge 3.7 cm spinal needle can be used. For adult animals a sturdier needle, such as an
18 gauge 6.25cm spinal needle, is recommended. The needle should be inserted midline
perpendicular to the curvature of the hindquarters and perpendicular to the midline sagittal plane of
the animal, i.e. not gnecessarily parallel or perpendicular to the floor or table top

18. • Considerable pressure may be needed to introduce the needle through the skin and supraspinous
ligament and it may be preferable to puncture the skin first with a larger, sharp hypodermic needle.
Once introduced, the spinal needle should be advanced gently for two reasons. First, to be able to
appreciate the resistance then penetration of the interarcuate ligament which lies over the epidural
space, described as a ‘pop’, and secondly, to control introduction of the tip of the needle into the
epidural space so that movement of the needle can be stopped immediately. Further introduction of
the needle will penetrate the spinal cord and the animal, if conscious, will jump and may dislodge the
position of the needle. If the tip of the needle strikes bone and the needle does not appear to be
deep enough to be in the epidural space, the needle should be withdrawn until the tip is just under
the skin and redirected in a cranial direction. If unsuccessful, the procedure should be repeated with
the needle advanced in a caudal direction. After correct placement of the needle, the stilette should
be removed and placed on a sterile surface. A 3 ml syringe containing 0.5 ml air should be attached
to the spinal needle and the plunger withdrawn to test for aspiration of cerebrospinal fluid (CSF) or
blood. Attempts at aspiration should reveal only a vacuum and aspiration of air meansthat the
syringe is not tightly attached to the needle. When no cerebrospinal fluid or blood is aspirated, a test
injection of a small amount of air should be made. Injection should be easy whenthe needle is in the
epidural space. After correct

19. • placement of the needle, the 3 ml syringe should be detached and the syringe containing the local anaesthetic
solution attached. Injection of the drug should be made over at least 30 seconds. Faster injections result in
increased intracranial pressure which, if the animal is conscious, manifest as opisthotonus, nystagmus, and
collapse. After injection, the spinal needle should be withdrawn. If analgesia of one side or leg is required the
animal should be placed in lateral recumbency with the side to be desensitized underneath. When bilateral
analgesia is required, the animal should be positioned either prone or supine so that the vertebral canal is
horizontal. The goat or sheep should not be allowed to ‘dog-sit’, otherwise analgesia will not develop cranially. The
spinal cord may project into the sacrum in sheep and goats and penetration of the dura will result in aspiration of
CSF. Injection into the subarachnoid space of the same volume of local anaesthetic intended for epidural
analgesia will result in the block extending further cranially and respiratory arrest. Usually, the volume for
subarachnoid injection is half the epidural dose. There is some risk of local anaesthetic solution entering CSF
through the puncture hole if the spinal needle is partly withdrawn and redirected into the epidural space a few mm
distant from the original insertion. If the entry of the needle into a venous sinus is not detected by aspirating blood,
intravenous injection may result in cardiovascular depression. The local anaesthetic solution should be warmed
when the epidural injection is to be made in the conscious animal. Injection of a cold solution will stimulate
receptors in the spinal cord and the animal will jump, possibly dislodging the needle. Indwelling catheters can be
inserted into the epidural space at the lumbosacral junction using a 16 gauge Tuohy needle as described for
caudal analgesia. Placement of a venous catheter is a sensible precaution when epidural analgesia is to be used
for surgery. Epidural injection of local anaesthetic solution causes paralysis of the splanchnic nerves and results in
a decrease in blood pressure. Hypotension may develop, especially in hypovolaemic animals, such as for
caesarian section, or animals positioned in such a way as to promote pooling of blood in the hindlimbs. In these

20. • animals, treatment should include expansion of blood volume with intravenous
administration of fluid and injection of ephedrine, 0.06 mg/kg, or methoxamine,
5–10 mg. Animals with urethral obstruction being given epidural analgesia for
perineal urethrostomy or cystotomy may already have a distended urinary
bladder at risk of rupture. Nonetheless, administration of fluid intravenously is
important to restore blood volume and cardiovascular function. One option is to
decrease the size of the bladder by cystocentesis. Alternatively, fluid infusion
can begin at the time of epidural administration so that surgical relief of
distension can be accomplished before a substantial increase in urine
production occurs. Approximately 50% of human patients experience visceral
pain during caesarian section under epidural block with bupivacaine and
describe the pain as poorly localized, dull pain, or as a feeling of heaviness or
squeezing (Alahuhta et al., 1990). Sheep or goats may respond by movement or
vocalization to manipulation of viscera during laparotomy under epidural
analgesia with lignocaine or bupivacaine. The animals may be made more
comfortable by i.v. butorphanol, 0.1mg/kg, diazepam, 0.05–0.10mg/kg, or
xylazine, 0.02 mg/kg. Disadvantages of adjunct drug

21. • administration include respiratory depression, pharyngeal relaxation that may
promote regurgitation and pulmonary aspiration, and depression of the lambs
or kids delivered by caesarian section. Sensory block may extend several
dermatomes cranial to the level of motor block. Limb movement is possible
even when the animal is sufficiently analgesic for surgery. During recovery
from epidural block, the ability to move the hindlimbs may develop before
analgesia is lost, although the ability to stand may not return until long after
analgesia is gone. Respiratory paralysis can occur if local anaesthetic solution
travels cranially to the neck. This will occur if a too large volume is injected, i.e.
inaccurate calculation of dose. In this event, general anesthesia must be
quickly induced, the trachea intubated and IPPV applied until the animal is
able to breathe again. During recovery from epidural block produced by local
anaesthetic solutions, the animal should be allowed to recover quietly. It will be
able to maintain sternal recumbency but there is potential for injury to the
hindlimbs if it makes uncoordinated attempts to rise