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Q.640. Why Kt/V & creatinine clearance may not be correlated in continuous P.D.?


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Q.640. Why Kt/V & creatinine clearance may not be correlated in continuous P.D.? 

A. Until now the best yardstick for P.D. adequacy remains to be determined. Whereas prev. recomm. sugg.: use of either urea or cr. kinetics, 2006 NKF-K/ DOQI G.L. recomm.: Kt/Vurea target (ie, urea kinetics) only. Alth. Cr. cl. & Kt/V us. correlate, they’re not infrequently discrepant. Both DX. & Kru affect both Cr. Cl. & Kt/V. Ratio of Cr. Cl.-to-Kt/V is higher in ptn é Kru & falls if he became anuric.

Ch.ch. of Pr. membrane transport may affect the relationship between Cr. cl. & Kt/V. For shorter dwells, esp. in low transporters, urea clearance per dwell exceeds tht for Cr.. Whereas weekly Kt/V is independent of transporter type, weekly Cr. Cl. ê progressively fr. high to low transporters. It’s important to be aware of Pr. membrane transport ch.ch. of individual ptn when writing PD prescription & interpreting solute clearance results. Ptn wt hs a greater effect on Kt/V thn on Cr. Cl.. {A dcr. or incr. in wt Ø Kt/V to incr. or dcr., resp.}. So, Kt/V is often at or above target values in malnourished ptn & low in obese ptn. Using the desired rather thn actual wt Ø more accurate results.

Q.641. How to estimate the adequacy of peritoneal dialysis?

A. Ssc: (Minimal total Small Solute Clearance) target values:  minimal weekly target clearance (Kt/V urea & Cr. cl.) hv bn published by U.S. & international societies. A general consensus prev. recmm. target weekly DX. dose are not needed, wch may unnecessarilyØ transferred to HDX bec. of inadequate DX. é PD. ADEMEX study & Hong Kong trial hv shown: using standard P.D. regimens, attempts to maintain prev. recmm.: Ssc goals are not necessary. NKF-KDOQI 2006 guidelines revised the minimal delivered Ssc goals: Ptn. é Kru (considered signif. if ur. vol. >100 mL/d.E) the minimal "delivered" dose of Ssc shd be total (PD & Kru) Kt/Vurea of at least 1.7/w..Ptn. without Kru (insignif. if ur. vol. is <100 mL/d.), minimal "delivered" dose of Ssc shd be at least 1.7/w. European Best Practices Guidelines 2005 sugg.: minimum wkly target Kt/Vurea of 1.7.

The recmm. minimal delivered total Ssc of Kt/Vurea shd be at least 1.7/w. for CAPD. Measures preserving Kru is recommended. The minimal delivered total Ssc recomm. in the new guidelines are correct based on current evidence.

A requirement for higher values may be most applicable in U.S., a country in wch higher adequacy goals may be necessary for a relatively older & sicker ptn..In addition, higher values may be necessary in those eating more protein who may hv a metabolic need for relatively higher Ssc rates. In U.S., target doses sufficiently above minimum threshold to ensure minimum level of DX. dose , delivered to all ptn. target Kt/Vurea = 1.8/w..  

Automated P.D.: No prospective trials available & looking at relative risk of death in relationship to dose in APD . The 2006 K/DOQI work group: the higher targets prev-iously recomm. are not required é APD. Minimal dose of Kt/Vurea shd be 1.7/w. for APD. Once ptn is anuric , he shd undergo 24 h./d. PD to optimize middle molecular wt solute clearance. This’s because randomized trials hv only evaluated 24 h./d. PD. Calculation of solute clearance: Weekly Kt/Vurea cn be estimated fr. the foll.: daily Pr. urea clearance (Kt)= sum of product of all drain vol. (Pr.+ Kru) + ratio of urea conc. in the drained Dzt or urine to tht in pl. (D/P urea). If there’s significant Kru (residual kid. vol.:>100 mL/d.), both Pr. & residual R. components of Ssc are used in calculation.

Fluid balance:ñbody fluid ØñM.R. in P.D.. Fluid overload shd be evaluated & adjust P.D. prescription. To improve vol. status: [êdietary sod.; loop diuretics é signif. Kru; and/or change U.F. profile of long dwell or use aother osmotic ag.].                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 

Q.642. What are the problems with solute clearance & U.F. in continuous P.D.?

A. Ch. P.D. cn be complicated by A: inadequate “solute” clearance or ê U.F..     (1) Inadequate solute clearance:= [incr. BUN & pl. cr. or app. of uremic Sms despite seemingly successful PD]. It may be caused by poor compliance,  high protein intake or hypercatabolic state, or ê intrinsic P.M. permeability. These causes cn be distinguished by PET. Initial tttØ more intensive DX., achieved by é vol. of inflow Dzt/exchange. If failed Ø transfer to H.DX..

(2) Impaired U.F.: ch.ch. by persistently low drain vol. after 4 h. of dwell. It’s caused by é Pr. solute transport, wch may be transient, due to Ac. peritonitis, or sustained, often due to repeated episodes of peritonitis. Ptn é ê U.F. may be ttted by shortening dwell time, or by using more freq. hypertonic exchanges. Other options: instillation of icodextrin Dzt., or use of diuretics in ptn. é Kru. Occ. ptn é U.F. failure may require maintenance H.DX. via temporary C.V. cth..

Combination of N. or low solute transport & low drain volumes sugg. Pr. cth. malfunction, extraPr. Dzt. leakage, enhanced absorption by Pr. lymphatics or ê in U.F. Co.. A dcr. U.F. Co. is rare, and may occ. in conj. é SEP.

Q.643. How to increase K/t.V. in P.D. patients?

   A. Three tools to incr. K/tv.:                 B                    

(1) é No. of dwells. (Dwell= Exchange frequency).

(2) é Size of dwells.

(3) Use Icodextrin é day time.

Q.644. What is Quantum?  !     What is Adequest?  !

A. Quantiam: a device to check No. of dwells to check ptn. compliance in P.D.

A. Adequest: a formula developed by Baxter for evaluation of P.D adequacy.

Q.645. What is PET (Peritoneal equilibration test)?

A. PET = [a semi-quantitative assess. of Pr. Membrane” transport function”. ]  Ratio of solute conc. in Dzt & plasma (D/P ratio) at sp. times (t) dur. dwell signifies the extent of solute equilibration. Four categories are recognized: AA

1)   High Transporter Ü Rapid Loss of concentration gradient.

2)   High Average.

3)   Low Average.

4)   Low transporter.

Q.646. How & when to do PET?

PET is a highly reproducible procedure üü consisting of 4 h. DX. exch. é DX. solution. The standardized test measures Dzt cr. & glucose at 0, 2 & 4 h. of dwell & S.cr. & glucose at any time dur. the test. We perform a PET 1-2 w. after initiation of P.D., as a baseline value.      P

Clinical applications: to classify Pr. membrane func. & assess reasons underlying inadequate DX. or UF. To best assess UF failure, some recommend : modified PET Ø 2.5 % dextrose + 4.25% dextrose Ø maximal osmotic drive. With this test, failure: defined as [U.F. volume <400mL] after a 4 h. dwell with 2 L. of 4.25 % dextrose (3.86 % glucose). It’s not customary to perform a PET dur. or after episode of peritonitis as Ac. changes us. reversed after recoveryü.

Q.647. How frequent are abdominal hernias occurring in continuous P.D.?

A. Hernia rates in P.D. are currently rep.: 0.06-0.08 /ptn./y. Pathophysiology: Principal risk f. for hernia formation reflect anatomic, hydrostatic, or metabolic f.s. Sm.s incl. [painless swelling é different sites, discomfort or disfigurement & problems related to hernia complc.]. Migration of pr. fluid into other body structures cn c either abd. wall or genital edema. More serious complc. are rare but incl.: small bowel obstruction & intestinal incarceration and/or strangulation.

Measures taken pre- & post-operative to ê risk of hernia & Dzt. leaks incl.: eval-uation & repair of existing hernias, the location & procedures used for P.D. cth. Placement & methods to ê intra-abd. pressure in post-op. period. Ptns dev. hernia after initiation of PD shd undergo elective repair. Use of a polypropylene mesh prosthesis Øê risk of post-op. hernia. Low-vol. supine P.D. cn be resumed several d.s after repair. TTT of Dzt. leak varies in ptn. é or without ass. hernia. ttt of an uncomplc. Dzt. leak (é no ass. hernia) cn initially be ttt.ed by temporarily stopping PD, changing to low vol., supine, or dry day PD, or by short term transfer to HDX. ttt of recurrent leaks depends on location & etiology of the leak.

Q.648. what is the role of P.D. in treatment of acute kidney injury (ARF)?

A. PD is an overlooked procedure for dialytic support in AKI, Ac. PD remains a viable option for ttt of selected ptn. é AKI. This’s esp. true for hemodynamically compromised or hv sev. coagulation abn. or when other modalities are not readily available. Compared é other available modalities, PD hs several adv. as a RRT in AKI. These incl.:[Wide availability, ease of performance & access placement, ability to remove large amounts of fluid in hemodynamically unstable ptn, easy & gradual correction of acid-base & electrolyte imbalance, no need for anticoa-gulation and highly biocompatible]. There’re No. of indications & C.I. for Ac. PD in AKI. Most are only relative indications or relative C.I. for the technique. Ac. PD cn be performed intermittently or continuously (depending upon: desired fluid & solute removal) & either manually or APD. Ac. manual PD is us. performed by nurs-es. By comparison, automated device or cycler ê the need for constant nursing supervision. Standard Ac. PD prescription incl.: {length of session, Dzt. Compos-ition, exchange vol., inflow & outflow (drain) periods, dwell time, No. of exchanges, Dzt additives & adjusting fluid balance}.

Q.649. What are the complications associated with acute PD?

A. Ac. P.D. complc., some are serious, life-threatening, many are preventable:                 

 I. Mech. complications: Mostly not serious, but mayØê DX. Efficiency, wch incl.:

1)   Abd. Pain/discomfort: Mild abd. pain/discomfort is common & us. 2ndry to abd. distention. Moderate/sev. pain us. due to  cth.-related complc. or infc. .

2)   Intraabd. hge: Mild bleeding is frequent & cn be obs. é cth. placement. However, sev. intraabd. hge hs bn rep. fr. cth., partic. semirigid Ac. cth.

3)   Leakage: is common & ttt.: ê exchange vol. for 1st 24 h. Temporary cessation of PD may be necessary &  bowel evacuation cn mitigate the problem.

4)   Inadequate drainage: us. due to êbowel motility. Bowel catharticsØ improve drainage, while manipulation of cth. may occasionally be necessary.

5)   Bowel perforation: Obs. é semirigid Ac PD cth.ØSev. abd. pain, bld-tinged Pr. effluent, intraabd. hge & (rarely) shock. Bowel/fecal material cn be noted é effluent Dzt., ttt.: [Cessation of PD., cath. removal, i.v. A.B. & bowel repair].

II. Infc. complic.: Common, esp. peritonitis, wch cn be signif. dcr. by maintai-ning sterile precautions dur. cth. placement & preventing contamination dur. ex-changes. Leaking Dzt predisposes to peritonitis. Puncture site abscess cn result fr. bedside placement of Ac. PD cth., esp. missed attention to sterile technique.                                                                                                                                         

 III. “Pulmonary” complications:

1)   Basal atelectasis & pneumonia: cn result fr.é IAP ass. é Ac. PD.Ø inadequ-ate lung expansion & stasis of secretions.

2)   Pl. effusion: fluid migration È to thoracic cavity, hydrothorax, cn occ. é  diaphragmtic defect or its lymphatics Ø Rt. sided eff.(most common). êIAP by ê exchange vol. & using supine position wil help. Pleurodesis rarely required.

3)   Aspiration : é intraPr. pressure predisposes to GERDØ é risk of aspiration.

IV. CVS. complications:

1.    Hypovolemia: due to excessive U.F.

2.    Cardiac arrhythmias: due mostly to electrolyte & metabolic disturbances, or diaphragmatic elevation.

V. Metabolic complications:

1)   Hyperglycemia.

2)   Hypernatremia.

3)   Hypoglycemia.

4)   Hypokalemia: Standard PD solutions do not contain K+, add K+ to Dzt.

VI. Protein loss: May exceed 5 g/d.. wch incr. by aggressive U.F. & infection.