Dialysis

Question 1

Duration of Hemodialysis

Answer 1

typically 4h a day
3 days a week

Question 2

Access Sites for Dialysis

Answer 2

-Arteriovenous fistula (AVF): join artery to vein in arm -> placed 3-6 months before dialysis bc the fusion has to mature (often in chronic patients, where dialysis is likely in the future)

-Arteriovenous graft (AVG): polytetrafluoroethylene (PTFE) graft, join the artery to a vein in the arm via tube (patients with fragile veins)

-Percutaneous (tunneled) catheter: tube placed in a large vein (usually neck) -> emergent dialysis

Question 3

Pros/Cons of Arteriovenous fistula (AVF)

Answer 3

Pro:
-own veins are joined to own artery
-> lower rate of infection
-> less clot formation
-> last longer

Con:
-it takes 3-6 mo (up to 1 year) to mature
-not ideal for older patients or those with small veins
-the goal is to use the BP of the artery and cause the vein to become an “artery” ???

Question 4

Access sites for patients with small veins or elderly

Answer 4

Arteriovenous graft (AVG)

Question 5

Pros and Cons of Arteriovenous graft (AVG)

Answer 5

-artery and vein are connected via a tube
Pro: for elderly and pt with small veins

Con:
-can be used for up to 2 weeks
-risk of infection
-risk of clotting

Question 6

Pros and Cons of Percutaneous (tunneled) catheter

Answer 6

Pro:
-it is temporary
-for urgent dialysis

Cons:
-prone to infection
-high rate clots/clogging
-inadequate dialysis

Question 7

Indications for Dialysis

Answer 7

patients not able to maintain homeostasis
-AEIOU
-Acidosis
-Electrolyte Abnormalities
-Intoxication
-Overload (volume): pt doesn’t urinate, cant manage volume
-Uremia: pt doesn’t filter BUN -> BUN elevated (patient becomes uremic) -> altered mental status

Question 8

When should dialysis be initiated based on the guidelines?

Answer 8

Start discussion: CKD stage 4
-Initiate: CKD stage 5: kidney failure (symptoms)

-CAUTION: the patient may be at stage 4 but have no symptoms (AEIOU)

Question 9

Examples of patients appropriate to start dialysis

Answer 9

Patient A: ABG indicates acidosis
Patient E: elevated K value, peak t waves (complication due to hyperkalemia)

Patient I: antifreeze overdose (a substance that can be removed via dialysis)

Patient O: SOB and 3+ pitting edema, CXR confirms pulmonary edema (if a patient can’t or was not treated successfully with diuretics -> consider dialysis)

Patient U: his BMP shows an elevated BUN of 100 [7-20]

Question 10

Complications of HD (dialysis)

Answer 10

-chest pain
-arrhythmias
-hypotension:
excessive filtration, antiHTN meds, eating food before HD (activates parasympathetic NS -> lowers BP)

Question 11

How to counteract dialysis-induced hypotension

Answer 11

-slow down the filtration rate (if appropriate, some patients are more acute and need a high filtration rate)
-Trendelenburg position
-IV fluids
-Midodrine (alpha-agonist causing vasoconstriction, short-halflife and only going to last for the dialysis sessions)

Question 12

Other complications

Answer 12

-Muscle cramps (5-20%) due to volume contraction and decreased muscle perfusion
-> IV fluids, stretch and vitamin E (less studied)

-Thrombosis: patients using the AV graft
-> Use heparin (thrombose lysis) or saline flush

-N/V
-headache
-itching
-infection (in patients with the AV graft)

Question 13

Peritoneal Dialysis

Answer 13

-typically only used for end-stage renal disease (ESRD due to CKD)
-uses the peritoneal membrane to filter blood
-the dialysate flows into the abdomen -> blood in the blood vessels flows by and diffusion occurs in the membrane
-the dialysate is drained into a drainage bag after dialysis

Question 14

Two types of Peritoneal Dialysis

Answer 14

-Continuous Ambulatory Peritoneal Dialysis (CAPD): dialysis solution stays in the stomach for 4-6h and is changed 3-4x per day

-Automated Peritoneal Dialysis (APD): for patients unable to perform aseptic manipulations; automated cycler
-> Continuous cycling Peritoneal Dialysis (CCPD)
-> Nocturnal Peritoneal Dialysis

Question 15

Complications of Peritoneal Dialysis (PD)

Answer 15

Peritonitis
-contamination with skin bacteria (commonly gram-positive, but also gram-negative, polymicrobial, fungal)

-symptoms: abdominal pain, N/V, cloudy peritoneal fluid when draining the fluid!

Question 16

Diagnosis of Peritonitis

Answer 16

-elevated WBC > 100 cells/mm3 with at least 50% neutrophils

Treatment:
-Intra-peritoneal antibiotics (no systemic absorption)
-cover gram-positive and gram-negative empirically
-usually 2-3 weeks
RECALL: coverage for skin bacteria and gram-negative enterics

Question 17

Other complications of Peritoneal Dialysis (PD)

Answer 17

-Hernia
-Hypervolemia
-Feeling of fullness

Question 18

Continuous Renal Replacement Therapy (CRCT)

Answer 18

-gentler hemodialysis -> fewer volume shifts and less hypotension
-often reserved for critically ill patients

Access:
-Internal jugular vein
-Femoral vein
-Subclavian vein

Question 19

Medication dosing Consideration

Answer 19

-renal dose adjustments
-dosage might differ between the different types of dialysis
-active metabolites are renally eliminated
-CRRT&raquo_space; HD&raquo_space; PD

Question 20

Consideration of the drug choice during dialysis

Answer 20

-small molecular weight drugs = easily removed by the dialysis
-Protein-binding: bind drugs not so easily removed
-Vd: Vd (lipophilic) not greatly removed, hydrophilic - great removal
-pore size of the membrane

-for HD: the faster the rate, the greater the drug removal
-for PD: the more often the dialysate is changed the more drug removal

Question 21

Common skin bacteria and their antibiotic coverage + gram-negative enteric coverage

Answer 21

Anaerobes:
Cefotetan (2nd), Cefoxitin (2nd)
-Pip/Tazo
-Metronidazole
-Clindamycin
-Carbapenem