Concept behind DDAVP-HTS regime
The most troublesome part of treating hypoNa is the requirement of keeping a steady rise of SNa:
- SNa dropping may cause serious complication
- SNa rising too quickly as well may cause serious complication
Human body is just a huge compartment of salt water as far as SNa level is concerned. Given no significant reservoir in the body (unlike most other electrolytes which have intracellular reservoirs thus we need to consider input vs distribution vs output), The SNa level is simply the result of the balance between the input & output of water & Na.
Usually the tricky part of treating severe hypoNa with the traditional approach (aka the "chasing your tail" method) revolves around the unpredictability of renal response (i.e. output). So no matter how meticulously you control the input you can't have full control of SNa rise.
In the DDAVP-HTS regime, IV 3% hypertonic saline serves as the primary Na source to replete the "Na deficit". Its advantages include:
- reliable intake (when compared to NaCl tab which is not very palatable thus may have variable intake)
- High concentration (in other words, containing small amount of free water)
- thus usually doesn't require large volumes for treatment
- safe for administration via peripheral IV for relatively long duration
- See this post for details: Safety of hypertonic solution
- may be safe to be given as intermittent bolus instead of continuous infusion
- See SALSA trial
Regular DDAVP limits urine free water loss by creating a state of "iatrogenic SIADH", thus reduce the uncertainty of output. Regular extrinsic DDAVP also makes the abrupt (and sometimes unexpected) rise in SNa - usually as the result of low intrinsic ADH activity - less likely.
However, it also comes with its own limitation:
- Whilst DDAVP limits urine free water loss (diuresis), it doesn't restrain sodium loss (natriuresis), which can occur usually around day 3 of regular DDAVP-HTS
- See these posts for details:
- As it creates a state of SIADH, if input isn't properly controlled (e.g. free water ingestion not avoided), SNa can still drop.
Publication:
We have published our early experience with the DDAVP-HTS protocol in HKJEM:
Cheung JCH, Cheung EHL, Ho L, Tse CL, Yip YY, Lam KN. Protocolized proactive desmopressin plus 3% saline therapy for severe euvolemic hyponatremia in the wave of COVID-19: The local experience and the potential role of emergency departments. Hong Kong Journal of Emergency Medicine. 2023 Jul 19;10249079231188844.