Page 39 - VetCPD Jnl Volume 7, Issue 4

How do I manage hyponatraemia?
Patients with severe hyponatraemia (<120mmol/L) need managing cautiously. Guidelines suggest that sodium should not increase by >0.5mmol/L/hr.
Rapid correction can occasionally lead to osmotic demyelination syndrome, resulting in neurological signs which
can develop 2-3 days afterwards.As a result, occasionally fluids with a lower sodium concentration will be necessary to avoid rapid increases whilst continuing to supplement at the required fluid rate. Table 5 lists commonly used crystalloid fluids and their sodium content. Specialist advice should be sought in dogs with marked hyponatraemia.
When do I need to manage hyperkalaemia?
Hyperkalaemia in hypoadrenocorticism infrequently requires specific intervention.With initial fluid therapy the increase in blood volume and subsequent rise in urine production helps correct hyperkalaemia. However, severe bradycardia secondary to hyperkalaemia may require treatment. Calcium gluconate (0.5 – 1.5ml/kg given slowly intravenously over 30mins,
SubOn
If initial fluid resuscitation has failed to significantly improve the hyperkalaemia in the first 30 to 60 minutes of treatment, or if the clinical condition dictates,
DOCP is licenced and there is evidence to suggest it is superior therefore should always be considered the first-choice
One should tailor the dose of ‘Zycortal’, and the concurrently administered glucocorticoid replacement therapy,
to the individual dog based on clinical response and normalisation of sodium and potassium serum concentrations. Electrolytes should be evaluated at day 10 and between days 25-28 after injection. Based on this, clinicians have the option of either adjusting the dose or prolonging the dosing interval (see Figure 4 for general treatment recommendations); the former is preferred. If the patient remains hyperkalaemic at day 10 and is clinically stable then the dose of glucocorticoid could be increased, before the increased dose of DOCP is administered as
planned at the next evaluation.Although repeatedly assessing a patient in order to ascertain when the medication is next due incurs short-term costs, this is likely to reduce long-term costs if it achieves a longer (but effective) dosing interval.
It is important that the same machine is used to monitor electrolytes, and that samples are not old or haemolysed,both of which can affect the electrolyte concentrations.
(Baumstark et
then insulin may be required. Insulin The manufacturer’s suggested initial
causes movement of potassium into
cells, thereby decreasing extracellular potassium concentration. However, in this instance care should be taken to avoid hypoglycaemic episodes and intravenous dextrose will be required.
When do I inject desoxy- corticosterone pivalate (DOCP)?
In the event of a crisis, the main goals
of treatment are to restore fluid volume, correct electrolyte abnormalities and provide glucocorticoids. Long-acting mineralocorticoids are not necessarily indicated at this stage. DOCP should be used as soon as the patient is rehydrated appropriately to ensure optimal absorption.
What are the current recommendations for using DOCP? Zycortal® (Dechra, UK) is the authorised long-acting formulation of DOCP in
the UK.Although fludrocortisone is available from compounding pharmacies,
dose is 2.2mg/kg given subcutaneously: however, many clinicians use a lower initial starting dose of 1.8mg/kg, based on studies which have demonstrated that lower doses result in effective clinical control (Bates et al. 2013; Jaffey et al. 2017). A recent study demonstrated that 1.5mg/kg DOCP was effective at controlling clinical signs and electrolyte concentrations in the majority of dogs with hypoadrenocorticism (Sieber- Ruckstuhl et al. 2018).
The duration of action of DOCP has been shown to range from 32 to 94 days in naïve dogs, and from 41 to 124 days
in previously-treated dogs, with a final dosing interval ranging from 38 to 90 days (Jaffey et al. 2017). In the UK the manufacturers’ current recommendation is that ‘Zycortal’ is intended for long term administration at intervals and doses dependent upon individual response.
TYPE
Primary typical
Table 3: Expected ACTH and aldosterone levels in types of hypoadrenocorticism
Elevated
Low
Primary atypical/isolated hypocortisolaemia
Elevated
Normal/low
Secondary
Low
Normal
Table 4: Hydrocortisone and dexamethasone treatment in an acute setting
HYDROCORTISONE
DEXAMETHASONE
Provides glucocorticoid activity and has the advantage of providing short-acting mineralocorticoid support, advantageous for correcting hyperkalaemia.
It can be used as a CRI at 0.5mg/kg/hour or given as 10mg/kg boluses intravenously every 3-6 hours.
Its use requires close monitoring of electrolytes though, and dose reductions may be required in the face of severe hyponatraemia.
Provides minimal mineralocorticoid but provides rapidly absorbable glucocorticoid.
A wide range of doses are described from 0.03 – 0.625mg/kg IV every 12hours (Kintzer and Peterson 2014; Scott-Moncrieff 2015); however, there is no evidence to suggest that such high doses are warranted. Care should be taken with high doses in case of the development of gastrointestinal bleeding. A dose of 0.1mg/kg may be considered appropriate initially.
scribers
Table 5: Sodium content of commonly used crystalloid fluids
FLUID SODIUM CONTENT (MMOL/L)
0.9% NaCl 154
Plasmalyte
140
Hartmann’s
131
77
with concurrent ECG monitoring) is
cardio-protective and rapidly effective (it temporarily antagonises the effects of hyperkalaemia on the membrane potential of cells) but will not lower the potassium concentration.
0.45% NaCl
ly
al. 2014).
ACTH CONCENTRATION
PLASMA ALDOSTERONE
VETcpd - Vol 7 Issue 4 - Page 35