[steps275]

Effect of Squatting on venous return????

At some places it is written that it increases preload while at some places it shows that it decreases preload...
Really confused...
MTB fischer says preload increases:here is link
http://books.google.com/books?id=07...ng increase or decrease venous return&f=false

While this site says it decreases ... http://www.scribd.com/doc/37239626/Congenital-Heart-Disease

There was a ques in UWORLD about TOF n squatting but it is poorly explained about preload...
Well in TET spell treatment squatting relives symps by;;;
1-Constricting arteries n thus increasing afterload
2- And it can help in tet spell only if it decreases preload ..

Any good explanation plzz... or we have to just skip venous role of squating in tet spell treatment and remember its increasing preload effect while ansering murmur ques..:-((

Here is another link supporting decrease venous return..
http://books.google.com/books?id=s6...chanism of squatting on venous return&f=false

 

[rasheed]

Physiologic Sequence of Squatting and it's effect on TOF Spell, Afterload, and Preload

Squatting --> Obstruction of Femoral Arteries --> Increased Peripheral vascular resistance --> Increased LV Afterload --> Increased LV Pressure --> Decreased Right ventricular over Left Ventricular pressure gradient --> Decreased shunting of blood from right ventricle to left ventricle (R to L shunt) through the VSD --> Improved flow to the pulmonary artery --> Better alveolar perfusion --> Better oxygenation --> Decreased symptoms of TOF spell.

But also,

Squatting --> Obstruction of Femoral Veins --> Increased pooling of blood in the venous reservoir (high capacity veins) --> Decreased preload --> Decreased Venous Return --> Decreased blood coming back to the right ventricle --> again decreasing the flow across the VSD (RV to LV shunt)

I also suggest you read this
http://www.usmle-forums.com/usmle-step-2-ck-buzzwords/2676-knee-chest-position-children.html

 

[evavar]

Thank you Rasheed for your explanation, I was always confused about that.

 

[steps275]

Ya i know that ..and it shud be the mechanism to get relief from tet spells..but the prob is that for valvular prob n to ans wether murmur inc or dec w squating we need to know that fact properly coz in MTB ficher said opposite..I have also pasted the link to that and there are lot of site saying that squating increase preload...

 

[hardik221186]

hey thanks

Squatting --> Obstruction of Femoral Arteries ........

hey rasheed thank you very much for such a nice explanation nd now my doubt about squatting in rx of tof is clear........u doing such a nice job man keep it up man thanks once again

 

[hardik221186]

Well in TET spell treatment squatting relives symps by;

TET spell mean????full name??????????

 

[dr_ram]

hemodynamic effects of squatting.

I was searching on the internet last month, coz i had the same doubt.
i accumulated some info, i would like to share it.

Squatting shows its effect on hemodynamics in two phases:

1. Immediate- due to compression on peripheral veins.
2. Sustained- due to two reasons (A and B) explained below.

-First phase lasts for 20-30seconds, in which, there is sudden fall in venous return form lower extremities (decreased pre-load). This is the reason for DECREASED VENOUS RETURN IN FIRST PHASE. This phase helps by trapping highly de-oxygenated blood in legs and feet, therefore the child is relieved of the symptoms as soon as the child assumes this position.

-During next 15seconds, there is increased peripheral vascular resistance (mostly arterioles), in-turn increasing the left ventricular after-load.

-In about a minute's time the second phase sets in. This phase is due to increased left ventricular after-load (REASON A), which increases the left ventricular pressure ''relative'' to the right ventricular pressure. This leads to reduction of right to left shunt (as the pressure in left is higher than in the right ventricle), which in-turn increases pulmonary blood flow and allows better oxygenation of blood.
-It is assumed that due to INCREASED SKELETAL MUSCLE TENSION in squatting position, venous blood is pumped back to the heart. This leads to INCREASED VENOUS RETURN IN SECOND PHASE (REASON B), leading to INCREASED CARDIAC OUTPUT, which relives the child of cyanotic spell.
-please note that the increased cardiac output in second phase is only during the time when the child is in squatting position. Once the child resumes to standing position, the cardiac output and vascular resistance return to the baseline level

Therefore, there is,
Decrease in venous return during EARLY PHASE OF SQUATTING.
Increase in venous return during LATE PHASE.
Any corrections or suggestions are welcome.

 

[Rich]

Effect of Squatting on venous return????

Any good explanation plzz... or we have to just skip venous role of squating in tet spell treatment and remember its increasing preload effect while ansering murmur ques..:-((

[/URL]

dear steps275..

i see that ur confused bcos of not knowing when to answer "squatting increases preload", n when to answer "squatting increases afterload" as the mechanism for a given scenario...so let me try to help u out here..

there r 2 places where questions on Squatting comes up in USMLE (usually in step 2)

1) Squatting is part of a physical exam maneuver in patients with a murmur (or asxtic pts in whom u suspect mitral valve prolapse)...here the usmle wants to determine whether u r able to correlate the effect of various hemodynamic changes on the murmur (or does it elicit a murmur if none existed earlier)....
(Note: in old pts/or pts who cant squat...an equivalent test is to do a knee-chest flexion while supine..causes same hemodynamic change as a squat!!)

2) Children with TOF instinctively/from previous experience know they have to Squat to get immediate relief from tet/hypoxic spell.. n the usmle wants to determine whether u know the mech of how this relief is attained.

Now, what u shud understand is that...

in the first scenario... while we(physicians) ask the pt to squat during the physical exam...we r actually continuously auscultating this patient(while he was standing and immediately on squatting and then on standing again)[remember, how we were taught to "be seated" when asking the pt to squat so that we could continue auscultation uninterruptedly during this activity!!].

What we r trying to achieve from this continuous ausc....is to determine what happens to the existing murmur when the squat squeezed blood through the veins into the heart..ie..what is the effect on the murmur because of the INCREASED PRELOAD brought about by this SUDDEN squat.

however , in the 2nd scenario...as u must have read correctly from many of the posts above...while the child REMAINS Squatted, (ie over time)..this squat actually INCREASES AFTERLOAD...decreases R to L shunts etc..

Now, we never wait for this long (ie till the squat increases the afterload) during a P/E maneuver to determine whether murmur has undergone any change due to the increased afterload...
if we wanted to check the effect of afterload on a murmur [n we do in some cases....eg to differentiate b/w systolic murmur of mitral valve prolapse(inc with inc afterload) n Hypertrophic cardiomyopathy(dec with inc aftrload), b/c BOTH of them have a softer/decreased murmur with increased preload n viceversa]...so, if we wanted to check effect of afterload on a murmur...we wud ask pt to do a Handgrip(ask pt to squeeze ur fingers with both his palms), n NOT a PROLONGED squat (althou theoretically it can also give u the same result)

In short... if u dont want to read all the crap said upto now , n still want to get ur doubt cleared....let me summarize...

"When squatting is done as a P/E maneuver..we r looking for its ability to INCREASE PRELOAD n bring about a change in murmur" (a high yield point...ALL murmurs-AS/AR/MR/MS n their Pulm n Tricusp equivalents have INCREASED INTENSITY of murmur when preload increases, EXCEPT MVP and HCM).

"When children with TOF Squat..they do so b/c they r looking for the ability of the Squat to increase Systemic vascular Resistance (increase afterload)"

"If we wanted to check the effect of increased afterload on a murmur through a P/E maneuver...we wud ask the patient to do a handgrip exercise"

Cheers!!

 

[drcuddles]

But also,

Squatting --> Obstruction of Femoral Veins --> Increased pooling of blood in the venous reservoir (high capacity veins) --> Decreased preload --> Decreased Venous Return --> Decreased blood coming back to the right ventricle --> again decreasing the flow across the VSD (RV to LV shunt)

I also suggest you read this
http://www.usmle-forums.com/usmle-step-2-ck-buzzwords/2676-knee-chest-position-children.html

So does squatting increase or decrease PRE-load ? Isn't squatting supposed to increase preload ????

 

[drcuddles]

Squatting shows its effect on hemodynamics in two phases:

1. Immediate- due to compression on peripheral veins.
2. Sustained- due to two reasons (A and B) explained below.

-First phase lasts for 20-30seconds, in which, there is sudden fall in venous return form lower extremities (decreased pre-load). This is the reason for DECREASED VENOUS RETURN IN FIRST PHASE. This phase helps by trapping highly de-oxygenated blood in legs and feet, therefore the child is relieved of the symptoms as soon as the child assumes this position.

Can you please further clarify the above mentioned statement (Immediate stage) !

 

[Veridigm]

Dude. Thank you SO MUCH. My brain doesn't hurt any more, and the anger sharks are back in their pen.