Q.541. What is the importance of biocompatible membranes in hemodialysis?
HEMODIALYSIS
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Q.541. What
is the importance of bio-compatible membranes in hemodialysis?
A. Once chemical & cellular
components of blood come in contact é artificial DX. membrane ⮞ an inflammatory✺ response, can be induced. The less
biocompatible the membrane, the more likely to activate WBCs &
complement
cascade. Earlier studies: dialyzing ARF ptn.s é older
style non-biocombatible (cellulose-based )👎membranes ⮞🠝M.R.(25%),
comp. to synthetic membranes. Interestingly, external sources of
inflmm.⮞ exacerbate
the underlying dis. processes &
interfere é normal R. recovery.
Q.542. What
are the recommended strategies for prevention of A/V. graft thrombosis?
A. Vascular
access stenosis of A/V graft is initiated
by endothelial cell injury, which ⮞ upregulation of adhesion molecules on
the endothelial cell surface. Alth. unproven, measures to prevent neointimal hyperplasia as well as other pharmacologic ag. tht address some
of the elements underlying vascular stenosis may help prevent stenosis. High
risk ptn. of initial graft failure & at low risk
for bleeding⮞Start ✌ [dipyridamole + aspirin].
Ptns at high risk of graft failure are those é P.H. of early
thrombosis (=3 m. fr. surgery) of a previous AV
graft. It’s reasonable to forego such therapy given the uncertainty concerning
the benefit & 🠉 risk of bleeding. We do NOT recommend warfarin for
prevention of thrombosis & failure of an AV graft. H.DX. ptn é very
early (24-48
h.s of surgery) or recurrent graft thrombosis é absorption of underlying
stenosis, we initiate an evaluation for a coagulation abnormality or
hypercoagulable state. Among selected ptns é such abnormal ⮞ warfarin may be
appropriate..
Q543. What is the role of fish oil in prevention
arterio-venous graft failure?
A.: Effect of fish oil (4 g/d.) on arterio-venous (AV) graft failure was
assessed in a randomized multicenter study that comp. the effect of fish oil or
placebo capsules taken four times/d. starting seven d.s after graft
creation. At 12 m. of follow-up, compared é placebo, fish
oil was ass. é lower rate of graft failure, fewer thromboses
& fewer intervenetions. Based upon these data, we suggested: ttt é fish
oil for ptns who have an AV graft.
Q.544. How
can the hemodynamic instability (Hypotension,
Hpt) during HDX. be clarified?
A. A.Sm.tc Hpt: 15-50 % ⮞🠉morbidity, through two ✌ clinical
patterns:
Episodic Hpt: é latter stages of DX. [vomiting, msc cramps & vagal
Sm. (yawning)].
Ch. Persistent Hpt é long-term ptn. é pre-Dx
systolic B.P.< 100
mmHg.
ETIOLOGY:
1) Rapid dcrease in pl. osmolality, which⮞ extracellular water to move into cells .
2) Rapid fluid removal to
attain "D.W.", espicially é large interdialytic wt. gains.
3) Inaccurate
determination of true "D.W.".
4) Autonomic neuropathy.
5) 🠟 cardiac reserve.
6) Use
of acetate rather than bicarbonate as a Dzt buffer.
7) Intake
of anti-H.T. medications that can impair CVS stability.
8) Use
of a lower Na+ concentration é
Dzt.
9) Sudden
release of adenosine duration organ ischemia .
10)Ingestion
of a meal immediately before or during DX .
11)Arrhythmias/pericardial effusion
é tamponade, vol.-unresponsive⮞🠟B.P.
12)Reactions to Dzr membrane, which ⮞ wheezing
&
dyspnea as well as Hpt.
13)
Increase synthesis of endogenous vasodilators, such as N.O.
14)
High Mg. concentrations in Dzt.
15)
Failure to increase pl. vasopressin levels .
Serious
diseases:[ e.g.
attention e.g.[
arrhyth., pericardial tamponade, valvular disorders, M.I., hemolysis, hge, septicemia
& air embolism]. Whatever the cause, HDX.-associated
Hpt:🠉M.R.
Q.545. How
to manage? R
A. A.Sm.tic
Hpt ptn may suffer fr.[light-headedness, msc cramps, n. & v. & dys-pnea]. Ac.
management: UF ⮞ either
stopped or 🠟rate. Ptn should be é Trendelenburg position & 🠟 QB.
Replace intravasc. volume é mannitol or saline. We currently
use i.v. bolus of N.S. as 1stline. Further ttt is based upon
etiology, e.g. [occult sepsis, cardiac and/or pericardial
disease & G.I. bleeding]. Ch. debilitating H.DX Hpt.
due to intolerance to rapid changes in blood vol. may tolerate gradual vol.
changes of P.D. or nocturnal HDX, or 🠉time and/or frequency of HDX.
PREVENTION: Accurate
"D.W.": Adjust it empirically by trial &
error. It’s set at wt below which unacceptable Sm., e.g. cramping, n. & v., or Hpt occur.“D.W”
is highly variable & fluctuate é intercurrent illnesses (e.g. Drr.
or infection) & é changes in H.B. (Epo). Other modalities:[blood vol.
monitoring, U/S assessment of I.V.C., natriuretic peptide, extravasc. lung
water indices & bioimpedance]. Best studies⮞bioimpedance:
extra- & intracell.
vol. & total body water assess. Particular promise⮞technique in which continuous
intradialytic assess. are confined to the calf since excess extracellular
fluids is greater in L.L.. Steady, constant UF: DX machines
are equipped é accurate UF devices⮞remove vol. steadily & evenly over sessions ⮞ tolerance of UF é fewer S.E. Some physicians use
modeling protocols :more (or less) wt is
removed at beginning/end of DX. Efficacy of U.F./sod. Modeling help in sp.
cases. Incr. wt. loss us. occ. é setting of a higher Dzt sod. conc..
🠉 Dzt sodium & sod. modeling: Higher
Dzt sod.(≥140 meq/L) has been among the most efficacious & best
tolerated thpies for episodic Hpt. Dzt 🠋 sodium⮞ marked 🠋in
pl. osmolality dur. DX, protecting extracellular volume by🠋osmotic
fluid loss into cells. Efficacy of higher Dzt
sod. in 🠋Hpt &
other untoward DX-related S.E. ws assessed in a blinded, crossover study: A
constant sod.of140meq/LLinear sodium. ramping
(155-140 meq/L) Stepwise sodium ramping (155 meq/L /3 h.& 140 meq/L/ one
h.)Both sod. ramping protocols ⮞ signif. but small decreased in No. of Hpt episodes comp.e constant Na+DX.K/DOQI 2005: limitations
of sod. modeling:[lacked correlation between blood volume & onset
of Hpt, signif. individual &
interDX variations in sod. levels, thirst, wt gain & postDX
Hpt].
Combined sod. modeling & UF:UF
profiling is ch.ch. by UF being intermittently stopped or decr.
gradually, thereby ⮞pl.
refilling. Combination of UF & sod. profiling can further enhance pl.
refilling; in turn, this can ⮞ greater
stability during HDX.
Sequential UF & isovolemic DX: Maintenance
of pl. osmolality cn also be attained by initial UF alone (without DX) (isolated UF)
foll. by isovolemic DX in wch little or no further
fluid removal occur due to 🠋TMP.
This sequential procedure often allows large vol.
of fluid to be removed without inducing Hpt. This maneuver, however,
is difficult to perform in out ptn since it needs increased time of DX.
HCO3Dzt buffer: HCO3 is
now widely available & adaptable to all new DX machines. Diff. in cost betw.
acetate & HCO3DX is minimal, while
B.P. is better maintained é HCO3. Acetate
accumulation in blood ⮞V.D.
activity that ⮞dev.
of Hpt & -ve effects upon energy metabolism in the heart tht can 🠋cardiac function .
ºC control: Low DztºC: improve
hemodynamic stability by🠉CVS contractility & 🠉v. tone.
Isothermic DX, in wch body ºC remains constant dur. HDX, may
prove useful in stabilizing B.P.. Obs. tht ch. HDF may hv improved
hemodynamic stability comp. to HDX may result directly fr. diff. energy
transfer profiles.
Improvement in CVS performance: Frequency
of DX-ass. hemodynamic instability is greatly incr. é P.H. of [H.F., cardiomegaly, or IHD] ⮞ poor L.V. performance,
and, importantly, 🠋cardiac
reserve . CVS performance can be 🠉in the following ways:
1) Dzt Ca. However, 🠉Dzt Ca
may ⮞ hypercalcemia
&🠋bone
turnover.
2) Using cool ºCHDX, which can also 🠉vasc. resistance .
3) Correction of anemia with Epo.
Midodrine: Ptn é A.N.&
thosee severe HDX Hpt not responsive to the above measures ⮞ selective a-1
adrenergic agonist midodrine ⮞effective & well tolerated.
Carnitine: 🠋 incidence of Hpt episodes & msc cramps.
Avoid food: Food
ingestion on DX ⮞ signif.🠋 systemic
vasc. resistance tht cn contribute to 🠋in B.P. This effect is not
corrected by concurrent intake of caffeine. Adenosine release: = an
endogenous V.D. tht hs bn related to Hpt episodes on HDX. This is
cn be blunted by caffeine, wch act as adenosine receptor antagonist.
Adenosine
receptor antagonist, FK352, was found to signif. 🠋 episodes
of intradialytic Hpt . Vasopressin: Vasopressin release is not incr.
in HDX dur. vol. removal. Vasopressin significant ass. é 🠋 incid.
of Sm.tc Hpt episodes & 🠉 fluid removal.
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