In this presentation, Dr Ibanda discusses acute kidney injury and Renal replacement therapy in obstetric patients

1. Acute Kidney Injury and
Renal replacement therapies
Ibanda Hood

2. Contents
• Prerequisites
• Functions of the kidney
• Renal changes in pregnancy
• A comparison of RFT findings in pregnancy and non-pregnancy
• Acute kidney Injury(AKI) in pregnancy
• Definition
• Epidemiology
• Causes of AKI
• Diagnosis of AKI
• Management of AKI in pregnancy
• Pharmacotherapy
• dialysis
• Renal Replacement Therapies/Strategies

3. Functions of the kidney
• Regulation of extracellular fluid volume.
• Long-term control of Blood pressure
• Regulation of osmolarity.
• Regulation of ion concentrations. (sodium, potassium and calcium).
• Regulation of pH.
• Excretion of wastes and toxins.
• Production of hormones (Erythropoietin, Vit D)

4. Physiologic adaptations of renal in pregnancy
• Anatomical
• Dilatation of renal collecting system
• Kidney enlargement
• Some hydronephrosis/hydroureter is normal
• More effects are seen on the right side
• Relative Statis of Urine
• Hemodynamic
• Decreased peripheral vascular resistance
• Decreased renal vascular resistance
• Arteriolar underfilling-leads to systemic responses
• Increased plasma volume
• Increased cardiac output
• Decreased blood pressure-mid-gestation
• Increased renal plasma flow/Increased GFR
• Solute Handling
• Some proteinuria is normal (<300mg/day
• Some Glucosuria is normal
• Acid-Base balance
• Increased minute ventilation
• Respiratory Alkalosis
• Kidneys compensate by decreasing serum HCO3
-
• Decreased HCO3
- reduces the buffering capacity if needed

5. A comparison of Renal function tests between
pregnant and non pregnant states
Parameter Pregnancy Values Nonpregnancy Values
Blood urea nitrogen (BUN) 5-12 mg/dl 10-20 mg/dl
Serum Creatinine <1 mg/dl <1.5 mg/dl
Serum Uric Acid 1.2-4.5 mg/dl 1.5-6 mg/dl
Serum Osmolality 275-280 mOsm/Kg 285-295 mOsm/kg
Serum Sodium 130-140 mEq/L 135-145 mEq/L
Serum Potassium 3.3-4.1 mEq/L 4.5-5.0 mEq/L
Urine Protein <300 mg/day < 150 mg/day
Urine Sodium 37-150 mmols/24hours 100-260 mmols/24hours
Urine creatinine-clearance 50-166 mL/min 91-130 mL/min
Urine Creatinine-Excretion 10.2-11.4 mmol/24hours 8.8-14 mmol/24hrs

7. Definitions

8. epidemiology
• Incidence in the LMIC has reduced over the last 30years.
• Decline due to decline in sepsis (2o Abortion/Birth)
• In HIC, the picture is not clear (classification but also use of ART)
increase GHTN/Preeclampsia.
• Mortality is higher in LMIC

9. Causes of AKI in Pregnancy
Obstetric complications
• Septic abortion
• Abruptio placentae
• Placenta praevia
• APH/PPH
• IUFD
• Puerperal sepsis
Pregnancy specific causes of AKI
• Preeclampsia/Eclampsia
• HELLP syndrome
• AFLP
• P-TMA
• aHUS
• TTP
• Hyperemesis gravidarum

10. Other Causes Not Related to pregnancy
• Postinfectious glomerulonephritis
• Lupus Nephritis
• Acute Pyelonephritis
• Dehydration
• Calculus of urinary tract

11. Classification of the causes of AKI
depending on the “location” of
the cause
Prerenal, Renal, and Post Renal

12. Prerenal AKI
• Hyperemesis gravidarum
• Hemorrhage
• Heart Failure
• Dehydration

13. Renal AKI
• Acute tubular necrosis
• Acute cortical necrosis
• AFLP
• Preeclampsia/HELLP
• TTP/aHUS
• Pyelonephritis
• Amniotic fluid embolism
• Pulmonary embolism
• Lupus Nephritis
• Acute interstitial Nephritis
• Drugs

14. Postrenal AKI
• Obstruction of urethral catheter
• Urethral obstruction (stricture, PUV)
• Neurogenic bladder
• DM
• Bladder rupture
• Blood clots
• Ureteral injury(clamping, cautery, ligation,
cutting, avulsion, devascularization, atony,
Adhesion with kinking)
• Edema
• Abdominal/Pelvic Neoplasms
• Compression from Gravid uterus, neoplasm,
lymphocoele, & Hematoma
• Congenital anomalies

15. Example of drugs that can cause kidney injury
• Antibiotics (
• NSAIDS
• Anfifungal
• Anticancer
• Herbal preparation
• Contrast agent

16. Investigations of AKI
Specific
RFT (Na, K, Cr, BUN)
Urinalysis (Volume/time, blood, urine Na, Cr, Urea, epithelial cells, proteins)
USS
IVP
Cystoscopy

17. Diagnosis of AKI

18. Diagnosis Of AKI (KIDGO Criteria)

19. MANAGEMENT OF AKI IN
OBSTETRIC PATIENTS
PHARMACOTHERAPY
DIALYSIS

20. Complications associated with AKI in
pregnancy
Maternal complication
• High likelihood of C-section
• Hemorrhage
• HELLP syndrome
• Placental abruption
• DIC
• Longer stay in ICU/HDU
• Preeclampsia in next pregnancy
• Maternal death
Fetal complication
• Higher incidence of perinatal
deaths/still births
• Lower gestation age at birth
• More LBW
N.B fetal complications can occur in next
pregnancy.

21. RENAL REPLACEMENT THERAPY
IN OBSTETRIC PATIENTS

22. Indications of Renal Replacement Therapy
Life threatening
• Refractory fluid overload
• Pulmonary Edema/Hypoxia
• Metabolic acidosis
• Azotemia (increased BUN/creatinine)
• Cardiac Failure
• Platelet dysfunction
• Hyperkalemia
• EKG Abnormalities (Peaked T-wave, ST- segment depression, BBB, Increased PR interval, Ventricular tachycardia, Decreased P wave Amplitude)
• Seizures
• Cerebral Edema
• Hepatic failure
• Neurologic Signs (comma, confusion, agitation, altered mental state, paralysis, paresthesia)

23. Indications of Renal Replacement Therapy
When recently reported, RRT is needed in the following conditions
• Severe sepsis/SIRS
• Multisystem organ failure(MSOF)
• Adult Respiratory Distress syndrome
• Tumor Lysis Syndrome
• Chronic Heart Failure
• Rhabdomyolysis(Myoglobin released during muscle injury)
• Some patients on Cancer chemotherapy

24. Methods used in RRT
• Hemofiltration
• Dialysis
• Hemodialysis
• Hemodiafilteration

25. Scientific principles used in RRT
For fluid removal
• Ultrafiltration: Hydrostatic pressure gradient forces fluid to move across a semipermeable
membrane.
For solute Removal
• Convection: Convection occurs when solutes are transported across a semipermeable
membrane with plasma water in response to a hydrostatic pressure gradient that is created
on the blood side of the hemofilter. Convection enhances the removal of low- and middle-
molecular-weight Molecules
• Diffusion: in diffusion, movement of solute across a semipermeable membrane is driven
by a concentration gradient between the blood and the dialysate. It’s suitable for LMW
substances like urea & creatinine
• Adsorption: Large and/or hydrophobic molecules with affinity for the membrane
attach to the inner pores of the membrane and hence are removed from plasma.

26. DIALYSIS
• Hemodialysis
• Peritoneal Dialysis

27. Types of Renal Replacement Strategies
• Temporary
• Intermittent Renal replacement therapy: Work on similar principles but
they balance the risk and benefits of temporary and continuous RRT
• Continuous Renal Replacement therapies
• Slow continuous ultrafiltration
• Continuous Venous Hemofiltration
• Continuous Venous Hemodialysis
• Continuous Venous High-Flux Hemodialysis
• Continuous venous Hemodiafiltraton

28. Slow continuous ultrafiltration (SCUF)
• It’s typically used for 24 hours
• High flux membranes and low flow rates are used
• It’s used for volume control in patients with severe, diuretic-resistant
volume overload.
• Disadvantage: the low filtration rates and lack of substitution fluids
render this therapy ineffective as a blood purification modality.

29. Continuous Venovenous Hemofiltration (CVVH)
• CVVH is prescribed for 24 hours, over an extended time.
• The technique uses High-flux membranes
• Convection is its main mechanism of solute transport
• High flow rates are used for the ultrafiltration rate, leading to loss of too
much filtrate.
• Hence, reinfusion(replacement) fluid is needed in CVVH
• Replacement fluid can be given before the filter (predilution) or after the
filter (postdilution).
• Post or predilution affects solute removal and therapy requirements.
• Predilution is more effective than postdilution.

30. Continuous Venovenous Haemodialysis
• CVVHD is characterized by slow countercurrent dialysate flow into the
ultrafiltrate/dialysate compartment of the dialyzer.
• Ultrapure dialysate may be produced using online proportioning
systems, or bags containing sterile dialysate may be used
• The prevalent mechanism of solute transport in this technique is
diffusion, with the prescribed ultrafiltration rate targeted to achieve
the patient’s desired fluid balance (i.e., without requirement of fluid
reinfusion)
• Either High flux or low flux filters can be used in CVVHD, but High flux
filters are typically prescribed.

31. When is CVVHD most useful
• used primarily to provide renal replacement therapy in critically ill,
hemodynamically unstable
• Adult patients with acute renal failure.
• Infants and children with inborn errors of metabolism
• CVVHD also has been advocated as a means to effectively cool
patients with hyperthermia
• It used to improve hemodynamic stability in hypotensive patients,
• To Treat hypothermia using warmed dialysate

32. Continuous Venous High-Flux Hemodialysis
• CVVHFD is delivered at the same manner of CVVHD, but with the use of
high-flux membranes
(membranes and filters are defined as high-flux when the membrane ultrafiltration coefficient KUF > 25 mL/hr/mm Hg/m2)
• In addition to diffusive solute clearance there is also a major element of
ultrafiltration and convective solute clearance
• The rate of ultrafiltration is controlled by an ultrafiltration/dialysate
volume control system and obviates replacement fluid.
• In CVVHFD, positive pressure in the dialysate compartment causes
ultrafiltration in the proximal part of the dialyzer and backfiltration more
distally
• During backfiltration, there is a flow of dialysate from the dialysate
compartment across the membrane into the blood compartment

33. When is CVVHFD best
• Sepsis: Clearance of higher molecular-weight inflammatory mediators
is achieved more effectively with high cutoff membranes during
CVVHFD.
• However, because many inflammatory mediators and cytokines are
removed primarily by adsorption, there is some removal also during
CVVHD and CVVH

34. Continuous venovenous Hemodiafiltraton (CVVHDF)
• Continuous venovenous Hemodiafiltration (CVVHDF) operates combining the principles
of haemodialysis and hemofiltration and requires a high-flux hemodiafilter
• CVVHDF may allow for an optimal combination of diffusion and convection to provide
clearances over a very broad range of solutes
• Dialysate is circulated in countercurrent mode with respect to blood and, at the same
time, ultrafiltration is obtained in excess of the desired fluid loss from the patient
• The ultrafiltrate is replaced partially or totally with reinfusion fluid, either in predilution
or postdilution mode
• For optimal clearance, Later-generation CRRT machines allow a combination of
predilution and postdilution with the aim of combining the advantages of both reinfusion
techniques.
• The optimal balance is dictated most likely by the specific set of CVVHDF operating
conditions, namely blood flow rate, dialysate flow rate, ultrafiltration rate, and filter type.

35. Addition Considerations in the delivery of RRT
• Anticoagulation: Systemic heparin is used, this helps in ensuring a longer
life of the filter.
• Drug elimination during CRRT: The pharmacokinetics of drug removal in
critically ill patients receiving CRRT is complex. In general, tissue protein-
bound drugs have relatively high molecular weights and large volumes of
distribution, resulting in limited removal.
• Yet, antimicrobials with lower protein binding are cleared more readily
• Flow rates, membrane pore size also significantly influences drug clearance. Combined
agents, e.g. PISA may have different clearance.
• Efficiency, Intensity, and Efficacy: can be used to characterize treatment
dose in CRRT.

36. A table summarizing some of RRT modes that
can be used in obstetric patients
TYPE ACRONYM NOTE
Slow Continuous Ultrafiltration SCUF • Its goal is fluid removal.
• Women who will benefit include those with fluid overload
and/or CCF
Continuous venovenous hemofiltration CVVH • Goal is fluid management with moderate solute removal
• Women with moderate electrolyte imbalance, are oliguria,
and need parenteral nutrition or blood products.
• Women in septic shock and those resistant to diuretics
• CVVH uses ultrafiltration and convection to remove fluid
and solutes
Continuous venovenous hemodialysis CVVHD • The goal of CVVHD is fluid management with greater
solute removal than CVVH
• Indications: hemodynamic instability, hypervolemia,
anuria, electrolyte imbalance, acidosis, & need for
parenteral nutrition despite fluid overload.
Continuous venovenous CVVHDF • CVVHDF’s aim is to maximize fluid & electrolyte removal

37. Complications of RRT
• Complications of Vascular access (cellulitis, abscess, bactiremia sepsis, hemorrhage, thrombosis,
vascular injury….)
• Complications of peritoneal access (sepsis, peritonitis, adhesion, visceral injury..)
• Complications of an extracorporeal circuit (hemolysis, bioincompartibility, air embolism,
micro contamination, chemical contamination……….)
• Complication of anticoagulation (Hemorrhage, Thrombosis, Heparin associated thrombocytopenia)
• Complications of hemodynamic instability and compromise (vasodilation, volume
depletion, Hypotension)
• Electrolyte imbalance
• Metabolic complications (acid base, electrolytes, vits & micronutrients depletion, amino acid depletion,
Hormone depletion)
• Complications due to human error (Physician, Nurse, Pharmacist, technician,)
• Thermal imbalance

38. References
• Liu et’ al .(2017). Pregnancy outcomes in patients with acute kidney injury during pregnancy: a systematic
review and meta-analysis; BMC pregnancy and child birth; 17(235).
• Tangren et’ al. (2017). Pregnancy Outcomes after Clinical Recovery from AKI; JASN; 28 (5) 1566-1574
• Rao, S. & Jim, B. (2018). Acute Kidney Injury in Pregnancy: The Changing Landscape for the 21st Century; KI
reports; 3 (2), 247–257.