Turning the Light on Peritoneal Dialysis: A Basic Introduction to PD
Turning the light on Peritoneal Dialysis (PD) • Understanding the modality • Patient selection criteria • Components of a successful PD program
Goal statement The goals of this presentation are to understand peritoneal dialysis and to recognize patient selection criteria as one component of a successful PD program.
Learning objectives At the end of this presentation the participant will be able to: • Describe the components of a successful PD program. • List the organization that provides guidelines for peritoneal dialysis including appropriate patient selection. • Describe the difference between peritoneal dialysis and hemodialysis • Describe the function of the peritoneal membrane and dialysate in peritoneal dialysis.
Before we can discuss how to grow a PD program we need to understand the modality. The next few slides will be a brief review of principles of PD. Let’s look at how PD can be used as a renal replacement therapy.
The structure of the peritoneum • Living, serous membrane • Can be damaged • Semi permeable and selective • Filters various kinds of solute to varying degrees • Forms a closed sac in males and in females the sac is open at the fimbria of the fallopian tubes • Is comprised of two principal types • Visceral peritoneum around the internal organs • Parietal peritoneum lining the abdominal wall
The structure of the peritoneum • Size approximates body surface area • Approximates the surface area of the skin 1-2m2 in most adults • Proportionately larger in infants and small children • Effective surface area is about 1m2 • Size equivalent to a hemodialyzer • Size is fixed • Can lose effective surface area
Peritoneal dialysis is an internal technique for blood purification • PD is dialysis but is unlike extracorporeal (out of the body) dialysis systems • Nature provides • Blood path • Membrane • Dialysate compartment
Peritoneal dialysis is an internal technique for blood purification • The peritoneal membrane forms the peritoneal cavity which functions as the dialysate compartment • The membrane is semi-permeable and selectively filters solutes to varying degrees • Capillaries within the membrane provide the blood pathway
Anatomy of the peritoneum • The peritoneum • Forms folds between organs and elsewhere. The folds which are reflected from the walls over the viscera are called mesenteries. The folds can connect viscera to each other or anchor organs to the abdominal wall. • The greater omentum is a fold in the serosa of the stomach that hangs down like an apron over the front of the intestines. • Tends to be larger in heavy or previously heavy individuals. • PD catheter can become entangled in the omentum.
Peritoneal cavity • Potential rather than an actual space • Normally contains approximately 100 ml • Dialysate volumes which are usually 2 - 4 L can result in: • Discomfort • Respiratory embarrassment (especially if there is a thoracic leak) • Decreased food intake secondary to a sensation of fullness • Problems related to fluid weight or pressure such as back pain, hernia or fluid leak into tissues
Anatomy of the peritoneum Peritoneal Cavity
Peritoneal cavity • A catheter (which is a foreign body) placed in the cavity can cause: • Discomfort related to catheter or fluid pressure (rectal, bladder, penile) • Poor drainage because the catheter floats freely in the peritoneal cavity and may become: • Displaced or flipped up from pelvic gutter • Wrapped in the omentum • Entangled bowel loops • Soft tissue penetration by the catheter (rare)
Function of the peritoneum - solute transport and clearance Let’s examine how solutes are transported across the peritoneal membrane. The peritoneal membrane is the patient's tool for doing the work of dialysis. Membrane capability varies from person to person but is usually stable in an individual.
Diffusion • Solute movement from an area of higher concentration to an area of lower concentration • Movement continues until equilibrium occurs
Diffusion and dialysis • Diffusion occurs across a membrane that is semi-permeable. • There are different degrees of permeability to solutes of different sizes. • Net transfer of molecules occurs until an equal concentration of a given solute on both sides of the membrane. • Movement continues but there is no net change in concentration from one side to another.
Diffusion and dialysis In this diagram the green triangles and red circles represent two different molecules that transport at different rates. We see that the red circles are already in equilibrium on both sides of the membrane while the green triangles are not yet equilibrated. If this were to represent dialysis, then there would be no further removal of the red circles but green triangles could still be further dialyzed off.
Blood Dialysate Osmosis • Water movement from an area of lower to higher solute concentration • Ultrafiltration, or the amount of water removed, is related to the osmotic pressure gradient
Blood Dialysate O s m o s i s Osmosis and dialysis In this diagram the “D”s represent dextrose, the solute used as an osmotic agent. The dialysis solution is very highly concentrated compared to blood so that water moves into the dialysate.
Test yourself 1. The peritoneum removes solutes and fluids much like the dialyzer or artificial kidney in hemodialysis. True False 2. The peritoneal membrane forms the peritoneal cavity which functions as the dialysate compartment. True False 3. Osmosis moves solutes out of the blood and into the dialysate. True False
Answers for test yourself 1. The peritoneum removes solutes and fluids much like the dialyzer or artificial kidney in hemodialysis. Answer: True. The peritoneum is a semi-permeable membrane and filters solutes and water during peritoneal dialysis. 2. The peritoneal membrane forms the peritoneal cavity which functions as the dialysate compartment. Answer: True 3. Osmosis moves solutes out of the blood and into the dialysate. Answer: False. Osmosis is the movement of water from an area of lower concentration to an area of higher concentration.
Continuous therapies • Continuous Ambulatory Peritoneal Dialysis (CAPD) • 4 - 5 exchanges* /24 hours • 2L - 2.5L exchanges* • 8 - 10L per 24 hours* • The exchanges are done manually by the patient *May be more • Dialysate is present in the peritoneal cavity at all times
Continuous therapies • Continuous Cycling Peritoneal Dialysis (CCPD) • Machine automated during sleep hours • 10 - 12 hours at night • 8L or more at night • 2L or more during the day • 10L or more in 24 hours • Dialysate is present in the peritoneal cavity at all times
Continuous therapies • PD Plus: Utilizing the cycler for a daytime exchange in addition to cycling at night • Night cycles for 8 – 10 hours • All exchanges delivered by cycler • Pause exchange • Night exchanges • Daytime fill • 10L or more / 24 hours • Dialysate is present in the peritoneal cavity at all times
PD solutions: Understanding what is in the dialysate • Composition of PD solutions: • Sodium 132 mEq/L • Potassium none • Calcium 2.5 - 3.5 mEq/L • Chloride 96 - 102 mEq/L • Sodium lactate 448 gm/100ml • Magnesium 0.5 - 1.5 mEq/L • Dextrose 1.5% - 4.25%
Dialysis exchange process An exchange should take approximately 20-40 minutes to complete. Drain Fill Dwell
The drain phase • Drain • About 15 - 25 minutes and depends on: • Catheter function • Amount of solution • Gravity • Diameter of tubing • Position or intra-abdominal pressure • Condition of system
The fill phase • Fill • About 10 minutes and depends on • Amount of solution • Solution bag height • Diameter of tubing • Intra-abdominal pressure • Condition of system
The dwell • Dwell (a prescribed time) • Dialysis takes place during the dwell time • Time required for transport of solutes across the peritoneum • CAPD • Usually 4 - 5 hours during the day and • 9 hours at night • Cycling • Usually 1 - 3 hours at night and • 15 hours during the day
Test yourself Peritoneal dialysis can be done manually or by a machine as the patient prefers. True False The fill time is the time that it takes to a. Stay in the peritoneal cavity b. Allow the dialysate to flow out of the cavity into a bag c. Drain fresh dialysate from the bag into the peritoneal cavity
Answers for test yourself Peritoneal dialysis can be done manually or by a machine as the patient prefers. Answer: True The fill time is the time that it takes to c. Drain fresh dialysate from the bag into the peritoneal cavity, filling the cavity with the dialysate fluid
Test yourself An exchange consists of _____ and ______. a. drain and fill b. fill and dwell c. fill, dwell and drain Continuous means that dialysate a. is always present in the peritoneal cavity b. is present except during the day c. is present except at night PD cyclers are most commonly used while the patient sleeps True False
Answers to test yourself An exchange consist of _____ and ______. a. drain and fill Continuous means that dialysate a. is always present in the peritoneal cavity PD cyclers are most commonly used while the patient sleeps True
Patient selection criteria • There are some patients for whom PD may be a better option than hemodialysis. • There are pros and cons regarding modality selection for any patient. • Selection of patients who may do better on PD or for whom PD may be contraindicated as per the KDOQI guidelines will be reviewed.
Patients who prefer PD or will not do hemodialysis. Patients report improved quality of life2 and that they are more satisfied with their treatments when compared to hemodialysis (HD) patients Pediatric patients No vascular access needed Due to the difficulties in maintaining vascular access in infants and small children, PD is usually the modality of choice when weight is < 20 kg. More gentle treatment Regular school attendance Can be best achieved by a home modality. K/DOQI Guideline 291: Indications for PD 1.National Kidney Foundation. NKF K/DOQI Guidelines http://www.kidney.org/professionals/kdoqi/guidelines 2.Merkus, MP. American Journal of Kidney Disease 29:584-592, 1997
K/DOQI Guideline 29: Indications for PD • Patients who cannot tolerate HD • Congestive/ischemic heart disease1 • Due to the rapid shifting of volume within fluid compartments during HD, some patients with severe cardiac disease may be better managed on PD. • Patients on PD have a lower incidence of left ventricular hypertrophy, arrhythmias, and hypertension compared to that of HD patients. 1. Canziani, ME. Artificial Organs 19(3):241-244, 1995
K/DOQI Guideline 29: Indications for PD • Extensive vascular disease and • Vascular access problematic patients • Extensive peripheral or central venous occlusive disease prohibits surgical placement of some types of hemodialysis access. These patients are at risk of severe ischemia or even gangrene following placement of vascular access. • Marginal vascular beds are at risk for ischemia or reduced perfusion during hypotension, which is frequent in some HD patients. These patients benefit from the increased vascular stability achieved with PD. Canziani, ME. Artificial Organs 19(3):241-244, 1995
Additional considerations for patients that would do well on PD • Distance from dialysis facility • Patients living in rural communities or where severe weather could be problematic. • Nursing home patients • Eliminates the difficulties with transportation three times per week. • Working patients • Avoids treatment scheduling conflicts • Patients who work report increased satisfaction with dialysis • Diabetic patients • No vascular access needed • IP (intra-peritoneal) insulin option
K/DOQI Guideline 30: Absolute Contraindications for PD • Documented loss of peritoneal function or extensive abdominal adhesions that limit dialysate flow. • PD efficiency relies on effective peritoneal blood flow, dialysate flow, sufficient peritoneal surface area and peritoneal transport rate to allow adequate solute and fluid removal. • Any compromise in these functions may result in inadequate peritoneal dialysis and thus the failure of PD. • There is no way of knowing the functionality of the peritoneum until it is tried. Many patients who have been on PD and were transplanted have successfully returned to PD post transplant failure. National Kidney Foundation. NKF K/DOQI Guidelines http://www.kidney.org/professionals/kdoqi/guidelines
K/DOQI Guideline 30: Absolute Contraindications for PD • Absence of suitable assistant in the patient who is physically or mentally incapable of performing PD. • Performing PD requires certain physical and intellectual capabilities in the patient and/or caregiver. • It is important that the patient and/or the caregiver be able to identify and troubleshoot any problems that may arise during PD. • Be open minded, blind patients, patients who cannot read, and patients with severe physical limitations have been successful PD patients. National Kidney Foundation. NKF K/DOQI Guidelines http://www.kidney.org/professionals/kdoqi/guidelines
K/DOQI Guideline 30: Absolute Contraindications for PD • Uncorrectable mechanical defects that prevent effective PD or increase the risk of infection (e.g., surgically irreparable hernia, omphalocele, gastroschisis, diaphragmatic hernia and bladder extrophy.) • The dialysate must come into contact with the vascular bed of the peritoneum, otherwise dialysis will not be accomplished. • These congenital birth defects involve a weakening of in the abdominal wall wherein abdominal organs herniate. National Kidney Foundation. NKF K/DOQI Guidelines http://www.kidney.org/professionals/kdoqi/guidelines
K/DOQI Guideline 31: Relative Contraindications for PD • Peritoneal leaks • Body size limitations • Intolerance to PD volumes necessary to achieve adequate PD dose • Inflammatory or ischemic bowel disease • Abdominal wall or skin infection • Morbid obesity (in short people) • Severe malnutrition • Frequent episodes of diverticulitis National Kidney Foundation. NKF K/DOQI Guidelines http://www.kidney.org/professionals/kdoqi/guidelines
K/DOQI Guideline 31: Relative Contraindications for PD • Patients with relative contraindications account for a only small portion of PD candidates and this population is not significant enough to impact the low PD utilization rate that we see in the US today. • This section of the K/DOQI guidelines is opinion based. National Kidney Foundation. NKF K/DOQI Guidelines http://www.kidney.org/professionals/kdoqi/guidelines
Test yourself There are written guidelines regarding patient selection criteria True False For some patients PD is a better option because it places less stress on the cardiovascular system. True False Documented extensive abdominal adhesions that limit dialysate flow will not impede PD True False
Answers to test yourself There are written guidelines regarding patient selection criteria True For some patients PD is a better option because it places less stress on the cardiovascular system. True Documented extensive abdominal adhesions that limit dialysate flow will not impede PD False, this is a contraindication for peritoneal dialysis.
Building the components of a successful PD program • Physician support • Active and effective modality education program • Program infrastructure