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Intradialytic Hypotension
By Alaa Sabry, MD, FACP
Professor Of Nephrology, Mansoura University
Clin J Am Soc Nephrol. 2014 Apr 7; 9(4): 798–803.
• A 65-year-old man was on hemodialysis since 2006 type II diabetes mellitus.
• Hypertension, coronary artery disease, moderate concentric left ventricular hypertrophy (LVH).
• Medications metoprolol, lisinopril, gabapentin, cinacalcet, calcium acetate, lanthanum carbonate , and omeprazole.
• Laboratory (sodium=139 mEq/L, potassium=4.6 mEq/L, calcium 8.9=mg/dl, phosphorus=6.5 mg/dl, parathyroid hormone=558 pg/ml, albumin=3.4 g/dl, and hemoglobin=11.5 g/dl ).
• Dialysis : 4 hours. • Dialysate (2.0 mEq/L potassium and 2.5 mEq/L calcium with Bicarbonate
acid concentrate.• Kt/V was 1.49.• His average interdialytic weight gain was 4 kg per treatment.• Dry weight was 98.5 kg.
• He developed intradialytic hypotension (IDH) episode .• His predialysis temperature was 36.2°C., he felt poorly and was
diaphoretic. • In response, saline was administered, ultrafiltration was stopped, and
the patient was placed in a reclining position with resolution of the hypotension.
• He had a previous history of IDH and as a result, was already being dialyzed with cool dialysate (temperature=35.5°C) and ultrafiltration modeling. Given the apparent absence of signs of volume, his dry weight was increased to 99.5 kg.
• Despite this increase, 9 days later, he developed another episode of IDH .
• On this day, his predialysis temperature was 35.8°C. Once again, his dry weight was increased (to 100.5 kg.)
Clin J Am Soc Nephrol. 2014 Apr 7; 9(4): 798–803.
complications
IDHo- IDHr
Cramps
Arrhythmia
Chest& back pain
Itching
Seizures
Dialyzer reaction
Hemolysis
Air embolism
Disequilibrium syndrome- N&V-
Headache
Definition
IDH remains one of the most vexing management challenges for nephrologists.
It has three essential components: 1)A drop in BP generally defined as ≥20 mmHg
systolic BP or ≥10 mmHg in mean arterial pressure.2) The presence of symptoms of end organ ischemia.3) An intervention carried out by the dialysis staff .
Agarwal R. Curr Opin Nephrol Hypertens 21: 593–599, 2012 IDH complicates approximately 15%–30% of all hemodialysis treatments
Intradialytic Hypotension (IDH) mechanism?
Patient factors
Cardiac disease - Systolic dysfunction - Diastolic dysfunction Arrhythmias Pericardial disease Autonomic neuropathy Interdialytic weight gain Food ingestion in dialysis Antihypertensive agents Anemia (< Hb 7.0g/dL)
Dialysis procedure factors
Ultrafiltration, solute removal (Slower refilling of plasma volume) Dialysate TempDialysate composition Low sodium (<138mEq/L) Low calcium High magnesium Acetate
• It is important to rule out acute conditions that can lower BP.
• 1- Infections (especially involving the access if the patient has a permcath or a graft), pneumonia, cellulitis, and osteomyelitis.
• 2- Blood loss.• 3- New onset of cardiac arrhythmias (new onset
of cardiac arrhythmias).• 4- Pericardial effusion.
• Annoying complains (cramping and postdialysis fatigue)• Early termination of dialysis : inadequate fluid removal and
reduced efficacy of the dialysis therapy.• Suboptimal ultrafiltration over the long term may lead to
volume overload and interdialytic hypertension. perpetuate left-ventricular hypertrophy and reduce arterial compliance, which may provoke more IDH.
• Vascular access thrombosis • Ischemia of cerebral, mesenteric, and coronary circulations.• IDH may affect health-related quality of life .• Increased medical and nursing care.
Chang TI, et al.J Am Soc Nephrol 2011; 22:1526–1533.Flythe JE., et al Kidney Int 2011; 79:250–257.
Pathogenesis
PathogenesisPlasma volume depletion
What happens in a normal individual that is subjected to PV depletion
Large degree of fluid removal Effective plasma volume depletion Stimulation of low pressure baroreceptors Stimulate efferent sympathetic pathway Increase in SVR Increase in venous return Increase in stroke volume Increase in CO
PATHOPHYSIOLOGY OF INTRADIALYTICHYPOTENSION
High ultrafiltration rates.
Impaired cardiovascular defenses
High ultrafiltration rates.
• During a dialysis procedure, several liters of fluid are ultrafiltered.
• This volume of ultrafiltrate often exceeds the entire plasma volume pool.
• Plasma volume is partially restored by refilling the intravascular pool from the interstitial fluid compartment.
• When dry-weight is probed, the interstitial fluid space is reduced. As a result IDH frequency is increased.
Why do some ESRD patients not compensate appropriately to ultrafiltration?
It can result from autonomic or baroreceptor failure or disturbed cardiac function.
Diabetes, aging, and uremia can cause autonomic and baroreceptor dysfunction, leading to excessive venous pooling and aberrant vasodilation.
Cardiac diseases, such as LVH, ischemic heart disease, myocardial stunning, contribute to cardiac dysfunction with IDH .
Selby NM, McIntyre CW.: The acute cardiac effects of dialysis. Semin Dial 20: 220–228, 2007
Impaired Baroreflex
There were gradated increases in endotoxemia withincreasing CKD stage
predialysis endotoxin correlated with dialysis-induced hemodynamic stress relative hypotension
400 BC, when Hippocrates stated, “death sits in the bowels.”
TMAO = Trimethylamine-N-oxide (TMAO) PCS = p-cresyl sulfate
IS= indoxyl sulfate
How to assess volume status in hemodialysis patients ?
1- Dry Body Weight
1- Dry Body Weight
• Defined as “the lowest tolerated postdialysis weight achieved via gradual change in postdialysis weight at which there are minimal signs or symptoms of hypovolemia or hypervolemia” .
• Sinha AD,. Semin Dial 22: 480–482, 2009
• Probing to achieve dry weight should be done with caution given the potential adverse consequences of hypotension in an ESRD population with multiple comorbidities that predispose to end organ ischemia.
• Achievement of even a relatively small reduction in dry weight (1 kg) in hypertensive hemodialysis patients reduced systolic and diastolic BPs by 6.6 and 3.3 mmHg, respectively, in the Dry Weight Reduction in Hypertensive Hemodialysis Patients trial .
Agarwal Ret al 53: 500–507, 2009 .
2- Peripheral edema
• The presence or absence of pitting pedal edema is perhaps the simplest physical sign to elicit.
• Fallacies :• 1- Edema may be due to excess vascular
permeability .• 2-Stasis .• 3-Vasodilator drugs including dihydropyridines.• The utility of this simple physical sign as a marker
of hypervolemia in HD patients is unknown.
2- Peripheral edema
3-Hypertension
• Recently shown to be a poor predictor of the presence of volume overload.
• 500 hemodialysis patients from eight centers and measured predialysis BP and deviation of hydration status from normal using multiple frequency bioimpedance.
• 13% of patients had hypertension but were not hypervolemic.• 10% of patients were hypervolemic but did not have
hypertension.• This finding shows that hypertension does not always equal
hypervolemia and vice versa in hemodialysis patients.
3-Hypertension
Clinical Methods
• Notwithstanding their widespread use, these clinical methods fail to evaluate ECV status accurately even when applied by a well-educated and dedicated staff.
Assessment of Extracellular Fluid Volume
4- Measurement of body Fluid VolumesA)-Tracers
• Deuterium and tritium dilution are preferred means to measure TBW.
• Bromide, inulin, ferrocyanide, chloride, and sucrose dilution yield data on ECV
• Volume B = tracer mass given⁄ tracer concentration in B.• B= The compartment of interest. • Dilution methods are considered as gold
standards for evaluating fluid status.
B-Whole-body bioimpedance• The most promising of the techniques.• Single frequency devices can only measure total body water .• Multifrequency devices measure both total body water and
extracellular water. • Whole-body bioimpedance is based on the assumption that the
body is a cylinder with uniform conductivity, which is not true given that the limbs provide 90% of total body resistance but only 30% of total body water. Segmental devices that measure bioimpedance in the calf do not suffer from this problem .
• Patients with pacemakers, stents, artificial joints, or amputation(s) and patients who are pregnant are prohibited to undergo bioimpedance analysis for safety and/or performance issues.
Dou Y, et al . Semin Dial 25: 377–387, 2012
B- Bioimpedance• (DW) is reached when two
criteria are satisfied:• (i) Flattening of the curve of
calf extracellular resistance (R0 ⁄Rt) over 20 minutes
• (ii) calf normalized resistivity( qN ) is equal to or greater than the lower threshold of the normal range seen in healthy subjects (males, 0.183 Xm3 ⁄ kg; females,0.20 Xm3 ⁄kg). 1-flattening of R0 ⁄Rt curve over 20 minutes
2- ( qN ) in the normal range (males, 0.183 Xm3 ⁄ kg; females, 0.20 Xm3 ⁄ kg).
C- Relative Blood Volume (RBV) Change• The relative change of blood volume (DRBV) can be
calculated from Equations ( assuming that red blood cell volume (RBCV) is constant during HD ).
• Online BV monitoring was suggested to evaluate the fluid status of HD patients.
• Disadvantage:• RBV was influenced by ultrafitration volume (UFV) and
UF rate (UFR). • Dasselaar JJ,. ASAIO J 53(4):479–484, 2007• RBV even increased by 2.4 ± 1.4% and 2.5 ± 0.8% during
the 1st and 2nd hour dialysis session even without ultrafiltration
• Nette RW, Blood Purif 19(1):33–38, 2001• A multicenter prospective study found that there were
no critical RBV reduction level for the appearance of symptomatic hypotension in 123 HD patients
• Andrulli S, Am J Kidney Dis 40(6):1244–1254, 2002
D- Biofeedback technology • Most biofeedback devices continuously monitor
blood pressure (BP) or infer plasma refilling from the relative blood volume.
• Calibrated software can then automatically adjust dialysate conductivity and/or ultrafiltration rates to optimize the balance between fluid removal and preservation of intravascular volume .
• Integrated mathematical modeling software can also be used to achieve neutral or negative sodium balance.
• Eight Trials .• 716 Patients .• All trials were open-label and at least four were
industry-sponsored. • No study evaluated hospitalization and the
evidence for effect on mortality was of very low quality.
• The frequency of IDH was lower among patient receiving biofeedback dialysis in all six studies that reported this outcome
Crit-Line Intradialytic Monitoring Benefit (CLIMB) Study
• A total of 227 patients were randomized to Crit-Line monitoring and 216 were randomized to conventional monitoring for 6 mo.
• Patients dialyzed with blood volume monitoring over a 6-month period versus controls had higher mortality (8.7% versus 3.3% (P 0.021) .
• Hospitalization rates were also higher in the intervention group.
Crit-Line Intradialytic Monitoring Benefit (CLIMB) Study
E)-The Inferior Vena Cava Diameter• The maximal IVCD during
quiet expiration and inspiration (IVCDe; IVCDi) and the collapsibility index (CI) are calculated.
• Inferior vena cava (IVC) diameter was measured at the level just below the diaphragm in the hepatic segment .
• Inferior vena cava (IVC) is normally 1.5 to 2.5 cm in diameter (measured 3 cm from right atrium).
• Inferior vena cava (IVC) normally collapses more than 50% with inspiration.
• Collapse <50% suggests volume overload
D)-The Inferior Vena Cava Diameter
• A limitation of ultrasound measurement• 1- Is user-dependent (significant degree of
intra- and interobserver variability ).• 2-Affected by patient compliance and conditions
(e.g., intestinal gases may reduce visibility). • Perhaps this indicates that it is not practically
feasible for routine hemodialysis use.• 3-it is difficult to interpret in patients with heart
failure and tricuspid regurgitation.
D)- Lung Ultrasound • Lung ultrasound can
evaluate extravascular lung water by identifying B-lines.
• Vertical artifacts arising from the pleural line and extending to the edge of the screen that move synchronously with respiratory acts .
• its use has been validated for the evaluation of acute respiratory failure acute and chronic heart failure .
• 71 consecutive patients undergoing HD.• Ultrasound, bioimpedance and clinical
measurements were performed immediately before and after (within 15 min) dialysis sessions.
• A significant reduction in B-lines numbers during the HD session, and the reduction in B-lines correlated with weight loss due to HD.
E-BiomarkerBrain Natriuretic Peptide
• The precursor protein pro brain natriuretic peptide (proBNP) is produced in cardiac myocytes.
• BNP is closely related to left ventricular (LV) mass and LV dysfunction.
• BNP has been proposed as a biomarker of fluid status.
• In HD patients, these biomarkers do not reliably reflect ECV status, because cardiac stretch is not well correlated with ECV.
Methods to assess ECV volume
vv
Management
Corrective steps to treat hypotensive episode
• Reduce the blood flow rate ???????
• Reduce the ultrafiltration rate
• Put the patient in Trendlenberg position ????
• Restoration of plasma volume
• Nasal oxygen
• Pressor agents
• Discontinue dialysis
Albumin Versus Saline ?
• Seventy-two patients .• 37 to treatment sequence 1 (5%albumin to treat the first episode of
IDH, the second and third dialysis sessions with IDH were treated with normal saline ).
• 35 to treatment sequence 2 (normal saline to treat the first dialysis session with IDH, the second and third dialysis sessions with IDH were treated with 5% albumin ).
• Effects of interventions:• 5% albumin is not superior to normal saline for the treatment of
symptomatic hypotension in maintenance haemodialysis patients with a previous history of IDH.
• There were no significant differences in the nursing time required to treat IDH and the time required to restore BP.
INTERVENTIONS TO REDUCE THEINCIDENCE OF IDH
Salt RestrictionNKF KDOQI guidelines recommend an upper limit of daily salt intake of 5 g( 85 mmol of sodium) .∼
1- Limiting interdialytic weight gain
• A common misconception that exists is that reduction in interdialytic weight gain is achieved by restricting fluid, which ignores the most basic principles of salt and water homeostasis.
• The main determinant of extracellular fluid volume is sodium.• This process involves making informed and healthy food
choices, because only 15% of salt ingested in the United States is added during the cooking process or at the table .
• Through dietary sodium restriction would provoke less ultrafiltration and therefore lower hemodynamic stress during dialysis.
• Limiting dietary sodium intake is therefore recommended especially for patients who gain excess (>2 kg) weight in the interdialytic period.
• Increasing dry-weight reduces the need to ultrafilter, but it also risks volume overload and hypertension.
• Thus, the decision to increase dry-weight has to be weighed against its potential risks.
2- Increasing dry-weight
3- Fasting during dialysis
• Sherman RA, Torres F, Cody RP. Postprandial blood pressure changes during hemodialysis. Am J Kidney Dis 1988; 12:37–39.
3- Food ingestion • After a meal:• 1-Peripheral vascular resistance decreases (20%).• 2- Blood flow to the splanchnic circulation (35%) and liver
(69 %)increase. • 3-Baroreceptor responses are impaired after glucose
ingestion. • Patients with autonomic dysfunction are particularly prone
to hypotension after meals (diabetic patients).• A prospective controlled trial of 125 hemodialysis
treatments in nine nondiabetic patients.• Mean BP fell by 14.4 mmHg/h 45 minutes after a meal
consumed between 1.5 and 2 hours after the start of dialysis versus 2.2 mmHg/h in the control period.
Sherman RA, Torres F, Cody RP.: Am J Kidney Dis 12: 37–39, 1988
The mean URR and spKt/V values of the patients were higher in the sessions without food ingestion.
The session with food intake showed a faster decrease in the MAP value after hour 1
4&5)-Sodium and UF profiling
• The dialysate sodium concenteartion at the beginning of the of treatment is hypertonic and during the final hours of dialysis is progresively reduced , reaching almost normal levels before the end of dialysis.
• Sodium profiling prevents IDH By:• 1- An increased ECF sodium level at the time of peak UF rate
improves water shift from ICF to the ECF compartment with improved venous refill and prevention of Bezold- jarisch reflex.
• 2- Hypertonic dialysate accelerates urea equiliberation between ICF and ECF while urea removal is at its peak during the first hour of dialysis.
Ultrafiltration modeling • Provide higher ultrafiltration
rates early in the hemodialysis procedure when the interstitial space is larger and plasma refilling is higher.
• As the treatment proceeds, the interstitial space decreases in size, refilling rates decline, and ultrafiltration rate is reduced.
4&5)-Sodium and UF profilingDisadvantages
• The time-averaged sodium concentration can result in positive sodium balance .
• Stimulates thirst.• Larger interdialytic weight gains .• Increases BP. • If a higher than mean dialysate sodium
concentration is used early, it must then be balanced by a lower than mean sodium dialysate concentration later in the treatment, which may result in an increase in IDH during this period.
• 24 studies• 76. 635 patients.• Effects of different sodium dialysate prescriptions minimum
concentration of 133 mmol/L- a maximum of 145 mmol/L• Higher DNa+ was significantly associated with greater mortality only
in patients with higher serum sodium concentration.• There was a trend toward lower mortality for those with lower
predialysis serum sodium concentration when dialysing against higher DNa+.
• This hypothesis is in agreement with a recent post hoc analysis of 1549 participants of the HEMO study, showing that each 4 mmol/L increment in baseline pre-dialysis serum sodium concentration was associated with an HR for all-cause mortality of 0.84.
The current range of 138– 140 mmol/L should be maintained until well-designed trials will offer new insights.
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6- Cool temperature dialysis
• First described by Maggiore et al. in the 1980s . Maggiore Q, Proc Eur Dial Transplant Assoc 1981; 18: 597–602
• Body temperature rises during standard dialysis .:• 1- Heat transfer to the patient from warm
dialysate (especially as many dialysis patients have low baseline core temperatures),
• 2- Reduced heat loss from the skin due to vasoconstriction
• 3- Increased thermogenesis from an inflammatory response to a blood-membrane reaction.
• Sixteen studies (235 patients) examined dialysis .• In the control arm of the study, standard dialysate
temperature varied between studies (38.5C, 37.5C, 37.0C and 36.5C ).
• Cool-dialysis temperature also varied ( 35.5C, 35.0C 34.5C and 34.0C ).
• No studies reported mortality as an outcome measure.
• universally adequate, most studies did not use blinding.
Outcome measures
Intradialytic hypotension Dialysis adequacy
The rate of IDH with standard dialysis was 7.1 times greater than with cool dialysis
None of these individual studies reported a difference in adequacy
Kt/V or URR
Other outcome measures
• Ventricular contractility:• A significantly greater increase in the velocity of circumferential
fibre shortening (ventricular contractility )with cool dialysis. • Plasma Noradrenaline:• A significantly greater plasma noradrenaline level with cool-
temperature dialysis .• Nitric oxide Products:• A greater fall with cool temperature dialysis. • Thermal Symptoms:• Three studies reported increased frequency of thermal
symptoms during the intervention arm.• 13–19% of patients felt cool in the intervention arm with a
dialysate temperature of 35.0C.
7- Change Dialysate Composition
Dialysate compositionCalcium
• Increasing dialysate calcium concentration improves myocardial contractility (stroke volume, systolic BP, and postdialysis calcium concentration )and reduces IDH.
• Limited Data have shown only marginal benefit on the freqency of IDH episodes with the use of dialysate Ca > 3.mEq/L.
Gabutti L, Nephrol Dial Transplant 24: 973–981, 2009
Draw BacK:• Hypercalcemia and decrease Bone Turnover.
8- Convective renal replacement therapies
Convective renal replacement therapies• A randomized trial that assigned 70 patients to
hemodialysis, 36 to hemofiltration, and 40 to hemodiafiltration .
• The primary endpoint of this trial was the frequency of symptomatic IDH compared to the baseline period.
• Among hemodialysis patients, the frequency increased from 7.1 to 7.9%.
• Hemofiltration, it fell from 9.8 to 8%.• Hemodiafiltration group it fell from 10.6 to 5.2%. • The OR for risk reduction in symptomatic IDH for
hemofiltration was 0.69 and for hemodiafiltration it was 0.6.
• Bolasco P,Ghezzi PM, Serra A, et al. Effects of acetate-free haemodiafiltration (HDF) with endogenous reinfusion (HFR) on cardiac troponin levels. Nephrol Dial Transplant 2011; 26:258–263.
9-Increased frequency and duration of dialysisShort daily hemodialysis
10- Adjusting antihypertensive medications • Hold antihypertensive drugs before
hemodialysis based on the rationale that poorer BP control in the short term is preferable to IDH, which is especially true for direct venous (nitrates) and arterial (hydralazine) dilators.
• One can also administer once daily antihypertensive medications at bedtime.
Pharmacologic measures
8- Midodrine • Midodrine a prodrug that is rapidly absorbed and
transformed into the active metabolite desglymidodrine, which is a selective α-1 adrenergic agonist.
• Administers 2.5–10 mg 15–30 minutes before dialysis. A second smaller dose can be given halfway through the treatment.
• It has high bioavailability, with peak levels occurring at 60 minutes, and it is removed by hemodialysis (half-life is 3.0 hours on hemodialysis); therefore, the drug effect does not persist long in the postdialytic period.
Prakash S, et al.: Midodrine appears to be safe and effective for dialysis-induced hypotension: A systematic review. Nephrol Dial Transplant 19: 2553–2558, 2004.
• Nine studies• 117 patients.• There was also a decrease in
symptoms of IDH with midodrine and very few adverse side effects.
• Limitation is the quality of the studies.• two of the studies were crossover in
design but the remainder were pre- and post-intervention.
• There were no published randomized controlled parallel group trials .
• The number of patients in each study was small.
Used Cautiously
• CHF• Negative intropes (beta Blockers)• Alpha adrenergic agents (ephrdrine, …
Aggrevate supine hypertension)• Antagonize action of alpha adrenergic blockers
(terazocin, Prazocin..)….. Urinary retention
Sertaline
• SSRI• Neurocardiogenic syncope,
Idiopathic orthostatic hyotension, IDH• SE; Inomnia, Dizzness, fatigue,
Somnolence and Headache.
• Laughter can provide (spontaneous or simulated).• 1- Improving mood• 2- Reducing depression • 3- Improving life satisfaction nd quality of life • Laughter Yoga (LY), developed in India in 1995 (clapping, arm and leg movement, deep breathing
exercises, gentle neck and shoulder stretches as well as facilitated laugh and smile exercises ) .• Takes only 30 to 45 min, and is appropriate for group settings Methods.• Design : 12 weeks • The number of IDH episodes in the four weeks prior to the LY intervention (pre), four weeks of the
LY (during), and four weeks after the (post) was compiled retrospectively.• Intradialytic hypotensive (IDH) episodes• There were 19 IDH episodes recorded in the month preceding the LY, 19 IDH episodes recorded
during, and four recorded post LY intervention. Based on these data, the odds of IDH decreased by 80 % (OR = 0.20, CI = 0.07 – .61) which was statistically significant (χ21 = 9.76, p = .002).
• The reasons for this difference are unclear but it is unlikely that a change of this magnitude would be related to the intervention alone.
How to increase BP?
TEMS & PCMs during dialysis show significant results in raising BP
• Dietary counseling on limiting salt intake, which resulted in a reduction of his interdialytic weight gain from 4 to 2.5 kg. Over the subsequent 2 months, there were no additional episodes of IDH. His predialysis BP has been stable around 130/60 mmHg.
Clin J Am Soc Nephrol. 2014 Apr 7; 9(4): 798–803.
Conclusion• IDH is and will continue to remain a management
challenge for nephrologists given the cyclical nature of expansion and contraction of the extracellular fluid volume with three times a week hemodialysis and difficulties in restricting sodium intake.
• Manipulations of the hemodialysis prescription and pharmacologic agents can help reduce the frequency of IDH.
• Salt restriction in an attempt to limit interdialytic weight gain, frequently use cool dialysate, administer midodrine in those patients who cannot tolerate cool dialysate when appropriate, prohibit food ingestion during the dialysis procedure, and use ultrafiltration modeling.
Neurological complications• Within the brain, MRI have shown pathological findings
including the presence of leukoariaiosis, “a nonspecific change in the brain white matter caused by loss of axons and myelin because of ischemic injury” (McIntyre, 2010) which is thought to increase vascular ageing.
• “This form of subcortical injury occurs precisely ... where episodic intradialytic reduced perfusion would be expected to have its maximal effect” (McIntyre, 2010).
There are several mechanisms counteracting the consequent relative intravascular hypovolemia, thereby aiming to preserve adequate blood pressure to ensure perfusion of critical organ systems they are:
1. Plasma refilling.
2. Cardiac adjustment.
3. Venous tone.
4. Systemic vascular resistance and arterial compliance. Failure of these compensatory mechanisms leads to
intradialytic hypotension.
Normal compensatory response on hemodialysis
In which acute drop in BP occurs due to sudden sympathatic withdrawal due to ventricular underfilling.
During severe hypovolemia, Bezold-Jarisch reflex can be triggered. This occuring in a patients who start HD with a lower BP or who are dialyzed with a high UF rate.
Impaired the normal reaction of the resistance and capacitance vessels during a decline in blood volume during dialysis treatment. A decreased arteriolar constriction may compromise the physiological increase in systemic vascular resistance during hypovolaemia. A reduction in the passive and active constriction of venules and veins, which serve to centralize blood volume during hypovolaemia, impairs venous return.
Types of intradialytic hypotension
Bradycardiac type (Bezold-jarisch reflex)
In which gradual decrease in BP occurs with tachycardia seems to be characterized by a gradual overwhelming of the patient’s maximal hemodynamic defense capacity due to the ongoing volume withdrawal. It was hypothesized, that failure of the heart to respond to the ongoing sympathetic excitation with a sufficient increase in COP might eventually result in sympathetic exhaustion. This point in time would be reached earlier in patients with diminished myocardial responsiveness or contractile reserve, who are therefore hypotension-prone .Conversely, one could also hypothesize that forward failure might develop as a result of cardiac exhaustion due to the persistent constriction of the circulation, with an insufficiently preloaded heart pumping against a maximally increased after load.
Tachycardiac hypotension
Hemodialysis therapy for more than 6 months is associated with
reduction of plasma and tissue levels of carnitine and carnitine esters.
Carnitine deficiency is associated with several metabolic defects,
defined as dialysis-related carnitine disorders, including IDH.
Intravenous L-carnitine therapy at 20 mg/kg into the dialysis venous
port with each session of dialysis was associated with reduced
frequency of IDH and muscle cramps and LV ejection fraction as it
improves vascular smooth muscle and cardiac function.
L-Carnitine
Sertraline is a selective serotonin reuptake inhibitor.
Improves symptoms in patients with neurocardiogenic syncope idiopathic orthostatic hypotension and IDH.
These disorders share a common pathogenic mechanism with IDH: a paradoxical withdrawal of central sympathetic outflow, resulting in sudden decrease in blood pressure with bradycardia.
Side effects dizziness, insomnia, fatigue, somnolence, and headache.
Avoidance of antihypertensive drugs and prescription of vasoactive medication before dialysis.
SSRI (Sertraline)
Haemodiafiltration techniques should not be considered a first-line option for the prevention of IDH, but as a possible alternative to cool dialysis.
Sequential isolated ultrafiltration followed by isovolemic dialysis should not be used as a regular strategy for the prevention of IDH
Prolongation of the dialysis duration and increase dialysis frequency or short daily dialysis.
Peritoneal dialysis: Treatment change to peritoneal dialysis should be considered in patients who remain refractory to interventions for the prevention of IDH.
Convective techniques and isolated ultrafilteration
Dysbiosis• An imbalanced intestinal microbial community with
quantitative and qualitative alterations in the composition and metabolic activities of the gut microbiota.
• The main contributing factors :1- Slow intestinal transit time . 2-Impaired protein assimilation .3- Decreased consumption of dietary fiber. 4-Iron therapy .5- Frequent use of antibiotics.
Schematic representation of the association between uremia, dysbiotic gut microbiome, gut-derived uremic toxins, andclinical manifestations of these uremic toxins.
Measurement of Body Fluid Volumes• A variety of methods are used to
determine body fluid volumes.• Methods differ with respect to
underlying principles and the fluid compartment of interest .
• Tracer dilution and bioimpedance techniques can estimate ECV, ICV, and total body water (TBW, TBW = ECV+ ICV),
• Monitoring of relative blood volume changes during HD, inferior vena cava diameter (IVCD) measurements and biochemical markers (such as atrial natriuretic peptide, brain natriuretic peptide [BNP]) provide information about the intravascular filling state. IF, interstitial fluid;
ECV, extracellular fluid; PV, plasma volume;RBCV, red blood cell volume; ICV, intracellular fluid; BIA, single or multifrequency
bioimpedance analysis; IF pressure, interstitial fluid pressure; RBV, relative blood volume; IVCD, inferior vena cava diameter..
Conclusion
• Biochemical markers and the IVCD method do not directly reflect ECV, which limits their clinical use.
• Relative blood volume monitoring may be useful to define individual tolerance levels for fluid removal, but it cannot provide information about ECV status.
• Currently, methods of multifrequency bioimpedance spectroscopy appear to be the preferred method to determine the ECV status in HD patients within a clinical setting.
• Combining BIS and RBV monitoring may help deliver HDwith both adequate fluid removal using a dry weight goal defined by BIS, and safe margins of ultrafiltration rate to prevent intradialytic hypotensive episodes.
• IDH is an important cause of morbidity among dialysis patients.
• Recently, the generation of endotoxins from an ischemic gut is proposed as a novel pathway that may cause IDH.
• Automatic biofeedback-controlled dialysis may improve IDH in part by improvement in myocardial stunning and preservation of cardiac function.
• However, the effects of automatic biofeedback dialysis are inconsistent between studies and sample sizes are small.
• Cool temperature dialysate causes vasoconstriction, activates the sympathetic nervous system, preserves central blood volume, and mitigates IDH.
• Increasing the treatment time to at least 4h three times a week and limiting dialysate and dietary sodium intake are effective ways to reduce IDH.
• Ultrafiltration profiling needs further work, but it appears that removing more fluid during the first hour of dialysis and reducing the rate later on may also reduce IDH.
Conclusion• Reducing dialysate temperatureis an effective
intervention to reduce the rate of IDH.• Overall, there was a trend to an increased
frequency of cold symptoms with cool dialysis • Reducing the temperature of the dialysate is an
effective intervention to reduce the frequency of IDH.
• Cool dialysis does not adversely affect dialysis adequacy
• We found that pedal edema in HD patients was associated with common cardiovascular risk factors such as older age, overweight or obesity, and left ventricular hypertrophy.
• Edema was not correlated to NT-proBNP, IVC diameter, collapse index, ejection fraction, right atrial pressure, left atrial diameter, or changes in RBV.
• This suggests that edema may not be a marker of intravascular volume in stable long-term HD patients.
