by André Voisin
PART IX
PRACTICAL METHODS OF PROTECTION AGAINST GRASS TETANY
CHAPTER 40
Therapeutics of grass tetany
Simultaneous injections of calcium and magnesium
The subject of this book is primarily the study of methods of protection against grass tetany; in other words, it is "protective" medicine,1 and not therapeutic or clinical medicine in relation to grass tetany that is being studied.
It seems necessary for the veterinary surgeon, however, to say something
on the therapeutic treatment of hypomagnesaemic grass tetany, before
studying rotective measures.
It was stated at the outset that it is not always easy to distinguish
hypomagnesaemic grass tetany from hypocalcaemic milk fever. This
difficulty in diagnosis appears to have led, in almost all countries, to a
mixture of calcium and magnesium
salts 2
being used for the injections. From some points of view, however, this is
not always very desirable, as calcium can assume the role
of magnesium antagonist in animal physiology. On the other hand, this
dual treatment has the advantage of:
| 1. | treating simultaneously hypocalcaemia and hypomagnesaemia, which are often difficult to distinguish; |
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| 2. | possibly avoiding the paralysing effects of an excess of magnesium. |
|
A treatment that has become popular is the parenteral injection of a
mixture of magnesium, calcium and phosphorus
(Mg, Ca, P).3
According to British surveys this would appear to be the most effective
treatment (Table 33).Table 33: Results obtained in the therapy of grass tetany using different injections
Treating the recumbent animal and the animal still able to stand
WHITE believes that there are grounds for applying different treatments depending on whether the animal is prostrate or still on its feet.
In the case of the recumbent animal he advises one intravenous injection
of 400 c.c. of a combined solution of calcium and magnesium salts,
together with the slow, intravenous injection of 80 c.c. of a solution of
25% magnesium sulphate. Almost immediately afterwards he gives a
subcutaneous injection of 60 gm. of a 25% magnesium sulphate solution.
Should there be no visible improvement in the animal's condition within a
few minutes, WHITE injects 600-1000 mg. chloropromazine
intravenously.4
In most cases after this additional injection it is possible to get the
animal into a sitting position and keep it there, supported by bales of
straw. A wise policy is to cover it with empty sacks so that it does not
catch cold. Moving the cow on the ground must be avoided, as must any
noise or sudden movement round about the animal. If it is in the sun, try
to shelter it by means of a shade for its body or at least a piece of
cloth for its head.
Where the animal is still standing but highly nervous, WHITE prefers an
intra-muscular injection of magnesium sulphate. Unlike the intravenous
injection, this does not require any restraint being placed on the animal,
and consequently there is less danger of triggering a more severe attack
and provoking a convulsion.
In both cases, if the treatment effects a partial or total improvement, it
is recommended that the magnesium injection be repeated the following day.
Even if the improvement in the animal's condition is insufficient,
injections of chloropromazine are recommended every 8-12 hours until the
animal becomes relatively calm. WHITE advises the commencement, as soon as
possible, of oral administration of calcined magnesite: the idea being to
consolidate the results obtained and prevent any relapse.
In every case it is up to the veterinary practitioner, with his well-known
powers of observation, to judge what line the treatment should adopt and
what methods should be applied.
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For the definition of "protective" medicine, see the introduction.
*
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Generally constituted as follows:
Pure calcium chloride 40 gm.
Pure magnesium chloride 15 gm.
Distilled water 400 gm.
Injected slowly over 15 minutes into the jugular vein of the standing
animal, or mammary vein if the animal is lying down, a watch being kept on
the heart.
Gluconates or burogluconates of calcium and magnesium can likewise be
used. CORNETTE advises the use of glutamates which supply a radical
neutralizing ammonia.
STEELE-BODGER advises intravenous injections of 3.3% magnesium lactate. He
believes the injection can be made rapidly without fear of the risks
incurred by the use of magnesium sulphate under the same conditions.
In the U.S.A. satisfactory results have been obtained from intravenous
injections of a 10% magnesium acetate solution.
Subcutaneous injections of 25% magnesium sulphate are also possible.
SEEKLES has been seen to advise subcutaneous injections of 10% magnesium
chloride.
Note that subcutaneous injections are resorbed more slowly than
intravenous, the latter having a more transitory effect due to their more
rapid elimination in the urine, not to mention the dangers involved if the
injections are given too quickly. In case of failure or relapse the
injections can be repeated every 3-4 hours. *
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In the U.S.A. DOZSA advises the intravenous injection of a solution
containing calcium, magnesium and dextrose. The injection must be made
slowly. *
- Or megaphene. Derivative of phenothiazine. Strengthens the effect of narcotics and acts as a sedative on the central nervous system. *