Page 963 - Problem-Based Feline Medicine

44 – THE CAT WITH GENERALIZED WEAKNESS 955

● Prednisolone sodium succinate (5–10 mg/ kg IV) Cardiac effects may persist after limb paralysis has
to reduce the likelihood and severity of anaphy- resolved. Cats should not be stressed for 2–3 weeks after
laxis. Wait 10–30 minutes before giving TAS. recovery from paralysis. In dogs, stress may cause sud-
● Epinephrine 1:10 000 (3 ml SC) about 5 minutes den death up to 3 weeks after discharge from hospital.
prior to administration of TAS to reduce the likeli-
hood of anaphylaxis.
Prevention
● TAS (0.5–1 ml/kg) diluted 50:50 with 0.9% NaCl
and warmed to room temperature; either give Check daily for ticks.
slowly IV (over 20–30 minutes) or give IP.
Use a preventative product (fipronil, pyrethrins).
Supportive care.
● Oxygen therapy (oxygen cage, flow-by, nasal
MYASTHENIA GRAVIS*
catheter, or positive pressure ventilation) is indi-
cated for moderate to severe dyspnea.
Classical signs
● Furosemide (2–5 mg/kg IV) should be given to
reduce pulmonary edema in dyspneic animals and ● Adult cats or Siamese < 1 year of age.
repeated as necessary. ● Episodic muscle weakness induced by
● Metoclopramide (0.5 mg/ kg IM or IV) is indi- movement.
cated in vomiting animals to reduce the risk of ● Ventral neck flexion.
aspiration. ● Decreased palpebral reflex.
● Eye ointment should be applied to prevent corneal
desiccation.
● Nil per os is essential until the gag reflex returns. Pathogenesis
Then introduce oral fluids slowly.
There are two forms of this disease; a congenital
● Parenteral fluids are not routinely indicated and
form that is not associated with antibody production,
must be used with care due to the potential wors-
and an acquired form that is associated with anti-
ening of pulmonary edema. Colloid or heta/penta
bodies being produced against the acetylcholine
starch fluids may be used to maintain circulating
receptor.
fluid volume if the hematocrit is significantly
elevated. Crystalloids may be given after 24 hours The congenital form occurs Siamese cats. Abyssinian
at submaintanence rates if slow return of the gag cats and possibly Somali’s may be predisposed to the
reflex delays introduction of oral fluids. acquired form.
● If possible animals should be positioned sternally
The acquired form can occur idiopathically, or second-
to minimize pulmonary ventilation–perfusion mis-
ary to a variety of tumors (thymoma). With thymoma,
matching. Laterally recumbent animal should be
the tumor either produces excess antibody or antibody
positioned with the shoulders elevated to aid pha-
is produced against a similar antigen within the tumor
ryngeal drainage and turned every 2 hours to reduce
and in muscle.
ventilation–perfusion mismatching.
● Urine retention often occurs and manual expres-
sion of the bladder may be needed during recovery.
Clinical signs
● Stress must be minimized.
● Provision of a cool (not cold) environment may This is a rare disease in cats. Generally a disease of
alleviate signs. adult cats, except for the congenital form in Siamese
which presents at < 6 months of age.
Prognosis
Exercise intolerance and episodic weakness induced
Prognosis for gait scores 1–3 and respiratory scores by walking or playing are typical signs. The cat may
A–C is good. Gait score 4 and respiratory score D con- walk a few steps and flop down. Recovery occurs with
fers a guarded prognosis. rest.