Thread by @ssfarouk, 1/As kidney replacement therapies (KRT) have become a strained and limited resource [...]

1/

As kidney replacement therapies (KRT) have become a strained and limited resource during the #COVID19 pandemic, here is a quick #tweetorial on how these treatments work:

What is the main mechanism by which clearance is achieved during intermittent #hemodialysis?

2/

KRT has 2 powers:

https://abs.twimg.com/emoji/v2/... draggable="false" alt="1⃣" title="Keycap digit one" aria-label="Emoji: Keycap digit one">Clearance (removal of solutes, like potassium

https://abs.twimg.com/emoji/v2/... draggable="false" alt="🍌" title="Banana" aria-label="Emoji: Banana">)

https://abs.twimg.com/emoji/v2/... draggable="false" alt="2⃣" title="Keycap digit two" aria-label="Emoji: Keycap digit two">Volume removal

https://abs.twimg.com/emoji/v2/... draggable="false" alt="💧" title="Droplet" aria-label="Emoji: Droplet">

...and it comes in 2 flavors:

https://abs.twimg.com/emoji/v2/... draggable="false" alt="1⃣" title="Keycap digit one" aria-label="Emoji: Keycap digit one">Intermittent

https://abs.twimg.com/emoji/v2/... draggable="false" alt="2⃣" title="Keycap digit two" aria-label="Emoji: Keycap digit two">Continuous

2/KRT has 2 powers: https://abs.twimg.com/emoji/v2/... draggable=

3/ How does the potassium go from 7.2 meq/L to 4 after an intermittent #hemodialysis (iHD) session?

Chemistry 101: DIFFUSION!

Solutes are cleared via diffusion as they move

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬇️" title="Downwards arrow" aria-label="Emoji: Downwards arrow"> their concentration gradient across a SEMIPERMEABLE membrane

DOI: 10.1056/NEJMc1301071

3/ How does the potassium go from 7.2 meq/L to 4 after an intermittent #hemodialysis (iHD) session? Chemistry 101: DIFFUSION! Solutes are cleared via diffusion as they move https://abs.twimg.com/emoji/v2/... draggable=

their concentration gradient across a SEMIPERMEABLE membraneDOI: 10.1056/NEJMc1301071" title="3/ How does the potassium go from 7.2 meq/L to 4 after an intermittent #hemodialysis (iHD) session? Chemistry 101: DIFFUSION! Solutes are cleared via diffusion as they move https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬇️" title="Downwards arrow" aria-label="Emoji: Downwards arrow"> their concentration gradient across a SEMIPERMEABLE membraneDOI: 10.1056/NEJMc1301071" class="img-responsive" style="max-width:100%;"/>

4/ A closer look at that dialysis filter...

Blood runs through the filter "straws", while the dialysate runs in the opposite direction

https://abs.twimg.com/emoji/v2/... draggable="false" alt="🔃" title="Clockwise downwards and upwards open circle arrows" aria-label="Emoji: Clockwise downwards and upwards open circle arrows"> around them & does not come in direct contact with the

https://abs.twimg.com/emoji/v2/... draggable="false" alt="🩸" title="Drop of blood" aria-label="Emoji: Drop of blood">

Larger filters with bigger pores can be used to further optimize clearance.

4/ A closer look at that dialysis filter...Blood runs through the filter "straws", while the dialysate runs in the opposite direction https://abs.twimg.com/emoji/v2/... draggable=

around them & does not come in direct contact with the https://abs.twimg.com/emoji/v2/... draggable="false" alt="🩸" title="Drop of blood" aria-label="Emoji: Drop of blood">Larger filters with bigger pores can be used to further optimize clearance." title="4/ A closer look at that dialysis filter...Blood runs through the filter "straws", while the dialysate runs in the opposite direction https://abs.twimg.com/emoji/v2/... draggable="false" alt="🔃" title="Clockwise downwards and upwards open circle arrows" aria-label="Emoji: Clockwise downwards and upwards open circle arrows"> around them & does not come in direct contact with the https://abs.twimg.com/emoji/v2/... draggable="false" alt="🩸" title="Drop of blood" aria-label="Emoji: Drop of blood">Larger filters with bigger pores can be used to further optimize clearance." class="img-responsive" style="max-width:100%;"/>

5/ Strategies to maximize clearance (particularly relevant now given the #COVID19-related strain on KRT):

https://abs.twimg.com/emoji/v2/... draggable="false" alt="1⃣" title="Keycap digit one" aria-label="Emoji: Keycap digit one">Bigger filter size

https://abs.twimg.com/emoji/v2/... draggable="false" alt="2⃣" title="Keycap digit two" aria-label="Emoji: Keycap digit two">Higher dialysis blood flow rates (usually, these are 300-400 cc/min)

https://abs.twimg.com/emoji/v2/... draggable="false" alt="3⃣" title="Keycap digit three" aria-label="Emoji: Keycap digit three">Widen the concentration gradient and try a potassium-free dialysate

5/ Strategies to maximize clearance (particularly relevant now given the #COVID19-related strain on KRT):https://abs.twimg.com/emoji/v2/... draggable=

Bigger filter sizehttps://abs.twimg.com/emoji/v2/... draggable="false" alt="2⃣" title="Keycap digit two" aria-label="Emoji: Keycap digit two">Higher dialysis blood flow rates (usually, these are 300-400 cc/min)https://abs.twimg.com/emoji/v2/... draggable="false" alt="3⃣" title="Keycap digit three" aria-label="Emoji: Keycap digit three">Widen the concentration gradient and try a potassium-free dialysate" title="5/ Strategies to maximize clearance (particularly relevant now given the #COVID19-related strain on KRT):https://abs.twimg.com/emoji/v2/... draggable="false" alt="1⃣" title="Keycap digit one" aria-label="Emoji: Keycap digit one">Bigger filter sizehttps://abs.twimg.com/emoji/v2/... draggable="false" alt="2⃣" title="Keycap digit two" aria-label="Emoji: Keycap digit two">Higher dialysis blood flow rates (usually, these are 300-400 cc/min)https://abs.twimg.com/emoji/v2/... draggable="false" alt="3⃣" title="Keycap digit three" aria-label="Emoji: Keycap digit three">Widen the concentration gradient and try a potassium-free dialysate" class="img-responsive" style="max-width:100%;"/>

6/ So that& #39;s how we remove solute. What about the fluid?

Ultrafiltration (UF), or ISOTONIC fluid removal, is achieved via pressure that is exerted across the membrane that drives fluid out.

DOI: 10.1056/NEJMct1206045 @luck_urine

7/ Here& #39;s what goes into the iHD order:

https://abs.twimg.com/emoji/v2/... draggable="false" alt="1⃣" title="Keycap digit one" aria-label="Emoji: Keycap digit one">Access, blood flow, + dialysate flow rates (standard 800 cc/min)

https://abs.twimg.com/emoji/v2/... draggable="false" alt="2⃣" title="Keycap digit two" aria-label="Emoji: Keycap digit two">Dialysate composition

https://abs.twimg.com/emoji/v2/... draggable="false" alt="3⃣" title="Keycap digit three" aria-label="Emoji: Keycap digit three">Ultrafiltration volume

https://abs.twimg.com/emoji/v2/... draggable="false" alt="4⃣" title="Keycap digit four" aria-label="Emoji: Keycap digit four">Filter size

https://abs.twimg.com/emoji/v2/... draggable="false" alt="5⃣" title="Keycap digit five" aria-label="Emoji: Keycap digit five">Duration (standard 3.5hrs - though #COVID19 has forced shorter treatment times, affecting clearance)

7/ Here& #39;s what goes into the iHD order:https://abs.twimg.com/emoji/v2/... draggable=

8/ What about SLED? (sustained low efficiency dialysis)

It& #39;s just like iHD, but...not as efficient...and should be done for longer durations (e.g. 8 hours) to obtain similar clearance to iHD

9/ Let& #39;s move on to the CONTINUOUS KRTs

The Players: CVVH, CVVHD, & CVVHDF

CVVH = continuous venovenous hemofiltration

CVVH is the only continuous modality that does NOT use a dialysate. So how do we get clearance?

https://abs.twimg.com/emoji/v2/... draggable="false" alt="💥" title="Collision symbol" aria-label="Emoji: Collision symbol">REPLACEMENT FLUID

https://abs.twimg.com/emoji/v2/... draggable="false" alt="💥" title="Collision symbol" aria-label="Emoji: Collision symbol">

9/ Let& #39;s move on to the CONTINUOUS KRTs The Players: CVVH, CVVHD, & CVVHDFCVVH = continuous venovenous hemofiltration CVVH is the only continuous modality that does NOT use a dialysate. So how do we get clearance?https://abs.twimg.com/emoji/v2/... draggable=

REPLACEMENT FLUIDhttps://abs.twimg.com/emoji/v2/... draggable="false" alt="💥" title="Collision symbol" aria-label="Emoji: Collision symbol">" title="9/ Let& #39;s move on to the CONTINUOUS KRTs The Players: CVVH, CVVHD, & CVVHDFCVVH = continuous venovenous hemofiltration CVVH is the only continuous modality that does NOT use a dialysate. So how do we get clearance?https://abs.twimg.com/emoji/v2/... draggable="false" alt="💥" title="Collision symbol" aria-label="Emoji: Collision symbol">REPLACEMENT FLUIDhttps://abs.twimg.com/emoji/v2/... draggable="false" alt="💥" title="Collision symbol" aria-label="Emoji: Collision symbol">" class="img-responsive" style="max-width:100%;"/>

10/ If you& #39;ve seen a pt connected to a #CVVH machine, you remember the huge bags hanging in the room - these are bags of replacement fluid that achieve clearance & are infused into the patient via the filter.

Hospitals can purchase pre-made replacement fluid (example below)

https://abs.twimg.com/emoji/v2/... draggable="false" alt="👇🏽" title="Down pointing backhand index (medium skin tone)" aria-label="Emoji: Down pointing backhand index (medium skin tone)">

10/ If you& #39;ve seen a pt connected to a #CVVH machine, you remember the huge bags hanging in the room - these are bags of replacement fluid that achieve clearance & are infused into the patient via the filter. Hospitals can purchase pre-made replacement fluid (example below) https://abs.twimg.com/emoji/v2/... draggable=

" title="10/ If you& #39;ve seen a pt connected to a #CVVH machine, you remember the huge bags hanging in the room - these are bags of replacement fluid that achieve clearance & are infused into the patient via the filter. Hospitals can purchase pre-made replacement fluid (example below) https://abs.twimg.com/emoji/v2/... draggable="false" alt="👇🏽" title="Down pointing backhand index (medium skin tone)" aria-label="Emoji: Down pointing backhand index (medium skin tone)">" class="img-responsive" style="max-width:100%;"/>

11/ Remember that replacement fluid is essentially infused unchanged into the pt, so use caution in those with hypoNa to avoid overcorrection

Of note: Therapy fluid can be infused either before or after the CVVH filter. If you do it before, may lose some solute (via convection)

12/ The graphic below illustrates the differences between #CVVH, #CVVHD, and #CVVHDF

CVVH:

https://abs.twimg.com/emoji/v2/... draggable="false" alt="✅" title="White heavy check mark" aria-label="Emoji: White heavy check mark">Convection + replacement fluid;

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛔️" title="No entry" aria-label="Emoji: No entry">dialysate
CVVHD

https://abs.twimg.com/emoji/v2/... draggable="false" alt="✅" title="White heavy check mark" aria-label="Emoji: White heavy check mark">Dialysate + convection;

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛔️" title="No entry" aria-label="Emoji: No entry"> replacement fluid
CVVHDF:

https://abs.twimg.com/emoji/v2/... draggable="false" alt="✅" title="White heavy check mark" aria-label="Emoji: White heavy check mark">Dialysate + convection + replacement fluid

@RenalFellowNtwk #FOAMed

12/ The graphic below illustrates the differences between #CVVH, #CVVHD, and #CVVHDFCVVH: https://abs.twimg.com/emoji/v2/... draggable=

13/ Say you only need volume removal, but no clearance:

Use your resources wisely and opt for a pure- #convection therapy:

Slow continuous ultrafiltration ( #SCUF) AKA aquapheresis or "CHF Solutions"

Don& #39;t waste dialysate or replacement fluid if you don& #39;t need it!

#COVID19

14/ Compared to iHD, continuous KRT will achieve slower clearance & volume removal

https://abs.twimg.com/emoji/v2/... draggable="false" alt="🐢" title="Turtle" aria-label="Emoji: Turtle"> (e.g. 100 cc/hr vs 1L/hr)

PIRRT = "middle ground" and uses higher RF rates to lower tx times & has been used during #COVID19 pandemic to maximize CKRT machine use

https://abs.twimg.com/emoji/v2/... draggable="false" alt="👇🏽" title="Down pointing backhand index (medium skin tone)" aria-label="Emoji: Down pointing backhand index (medium skin tone)">

https://www.nxstage.com/hcp/therapies/pirrt/">https://www.nxstage.com/hcp/thera...

14/ Compared to iHD, continuous KRT will achieve slower clearance & volume removal https://abs.twimg.com/emoji/v2/... draggable=

(e.g. 100 cc/hr vs 1L/hr)PIRRT = "middle ground" and uses higher RF rates to lower tx times & has been used during #COVID19 pandemic to maximize CKRT machine use https://abs.twimg.com/emoji/v2/... draggable="false" alt="👇🏽" title="Down pointing backhand index (medium skin tone)" aria-label="Emoji: Down pointing backhand index (medium skin tone)"> https://www.nxstage.com/hcp/thera..." title="14/ Compared to iHD, continuous KRT will achieve slower clearance & volume removal https://abs.twimg.com/emoji/v2/... draggable="false" alt="🐢" title="Turtle" aria-label="Emoji: Turtle"> (e.g. 100 cc/hr vs 1L/hr)PIRRT = "middle ground" and uses higher RF rates to lower tx times & has been used during #COVID19 pandemic to maximize CKRT machine use https://abs.twimg.com/emoji/v2/... draggable="false" alt="👇🏽" title="Down pointing backhand index (medium skin tone)" aria-label="Emoji: Down pointing backhand index (medium skin tone)"> https://www.nxstage.com/hcp/thera..." class="img-responsive" style="max-width:100%;"/>

15/ In summary:

https://abs.twimg.com/emoji/v2/... draggable="false" alt="1⃣" title="Keycap digit one" aria-label="Emoji: Keycap digit one"> KRT = continuous/intermittent

https://abs.twimg.com/emoji/v2/... draggable="false" alt="2⃣" title="Keycap digit two" aria-label="Emoji: Keycap digit two">Solute clearance: diffusion; UF: convection

https://abs.twimg.com/emoji/v2/... draggable="false" alt="3⃣" title="Keycap digit three" aria-label="Emoji: Keycap digit three">Modality choice: Volume/solute removal needs + what& #39;s available

https://abs.twimg.com/emoji/v2/... draggable="false" alt="4⃣" title="Keycap digit four" aria-label="Emoji: Keycap digit four">Optimize treatments that may be shorter by

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⬆️" title="Upwards arrow" aria-label="Emoji: Upwards arrow"> blood/RF flow rates, using larger filters, & tailoring your dialysate

16/

And did not cover this above - but acute #PeritonealDialysis is another innovative and effective way to relieve some of the strain on resources like iHD & CVVH

Will let @osamaelshamy88 tackle that #tweetorial...

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