Avoiding Kidney Injury:

Obstetric Patients

Objectives

• Discuss incidence and impact of acute kidney injury & chronic kidney disease in

obstetric patients

• Review the pathophysiology related to pregnancy and risk for developing AKI

• Summarize neuraxial and general anesthesia recommendations supported by the

literature for obstetric patients with AKI or CKD

For more information….

• For a more in-depth overview of kidney disease, including staging and definitions,

reference:

MPOG Avoiding Kidney Injury - Overview, Pathophysiology, Definitions

• For other specialty specific recommendations, reference the following sections of the

toolkit:

– Avoiding Kidney Injury - Pediatrics

– Avoiding Kidney Injury - Cardiac

– Avoiding Kidney Injury - Recommendations for Adult Surgical Patients

Kidney Disease in Obstetric Patients

• Kidney disease is an independent risk

factor for maternal and fetal morbidity and

mortality

• Multiple renal physiologic changes in

pregnancy

• AKI in pregnancy is rare, hard to define,

and difficult to measure

Renal Function Changes in Pregnancy

2,3

↑ Renal Blood Flow

↑ GFR (30-50%)

↓Scr

↑ Protein excretion (up

to 300mg/24h)

↓ Plasma osmolality

and plasma sodium

levels

↑ Uric Acid Excretion

↑Kidney

size by 1

Kidney volume

increases up to 30%

and dilation of

calyces, pelvis and

ureters occurs

Progesterone causes

smooth muscle

relaxation

Gravid uterus causes

partial ureteral

obstruction

↑ Stasis, resulting in

increased risk of

urinary tract

infection

↑

Intravascular

volume

Renal Function Changes in Pregnancy

3,4,5

CKD in Pregnancy

CKD in Obstetric Patients

Maternal Outcomes

Fetal Outcomes

• 5x more likely to experience

• Gestational HTN

• Preeclampsia

• Eclampsia

• Maternal Mortality

• 2x greater risk of adverse fetal

outcomes

• Risk proportional to degree of

maternal CKD

8,9

CKD is estimated to affect 3% of all pregnant women

CKD in Pregnancy

• Obstetric complications increase proportionally with the extent of the mother’s

preexisting renal disease and hypertension

• Women with CKD at increased risk for preeclampsia and preterm delivery

• There is a 4.7x greater risk of progression to ESRD for patients with CKD that develop

preeclampsia

Maternal Renal Function

Associated Risks

11, 13, 14, 15, 16, 17

Mild elevated creatinine (1.2-1.4mg/dL) Small risk for decline in renal function

Moderate renal insufficiency (1.4-2.5mg/dL) 20-30% increased risk of preeclampsia and preterm

delivery

Severe renal insufficiency (Cr >2.5mg/dL) 70% experience preterm delivery, 40% experience loss

of renal function during pregnancy or postpartum

leading to dialysis

Perioperative Management of Obstetric patients with CKD

• Include assessment of changes to renal function and related systems

Periop Eval

• Consult nephrology team to assist early in pregnancy

Consults

• Dependent on severity of CKD

• Typically euvolemic patients with stable mild to moderate renal insufficiency and well

controlled HTN do well with minimal special interventions

• Dialysis dependent patients present greater anesthetic challenge

Anesthetic Management

• Avoid nephrotoxic drugs in patients with residual kidney function

Nephrotoxic Drugs

Neuraxial Anesthesia Considerations for Obstetric patients with CKD

• Determine fluid status before anesthesia

– If euvolemic, treat hypotension with a vasopressor instead of fluids to reduce risk of fluid overload

• Assess coagulation status

– At risk for abnormal bleeding

– May have residual heparin from HD catheter that precludes regional anesthesia

• Documentation of pre-existing neuropathy prior to neuraxial anesthesia

• Insufficient evidence to recommend spinal vs epidural

Intraop Management of Obstetric patients with CKD

• Non invasive BP monitoring appropriate for early CKD with well controlled HTN

• Pad and protect HD fistula, no blood pressures on that arm

• Check serum K before OR, succinylcholine will cause a 0.5-0.7 mEq/L increase

• Magnesium sulfate prolongs NMB

• Morphine and meperidine can cause accumulation of toxic metabolites in renal failure

11,20

• Fentanyl, sufentanil, remifentanil are considered safe to use in renal failure

18,21

• Neuraxial opioids are a good choice for postop pain relief if not contraindicated

18,22

• NSAIDs may worsen renal function

11,23

AKI in Pregnancy

AKI In Pregnancy

• Causes of AKI

– In developing countries, septic abortions are the most prevalent cause of pregnancy related

AKI

24,25

– In developed countries, the most common causes are severe preeclampsia-eclampsia, acute

pyelonephritis of pregnancy, and bilateral renal cortical necrosis

26,27

• The majority of women who experience AKI in pregnancy have comorbid conditions or

pregnancies complicated by kidney disease, hypertension, diabetes, preeclampsia,

HELLP syndrome, hemorrhage or infections

Pregnancy Specific Causes of AKI

29,2

Early Causes (<20 weeks) Late Causes (>20 weeks)

Pre-Renal Hemorrhage (abortion, ectopic pregnancy)

Sepsis/Septic Shock (abortion, retained products

of conception, pyelonephritis, etc)

Hypovolemia (d/t hyperemesis gravidarum)

Hemorrhage (antepartum: placenta previa, placental

abruption, placenta accreta) (postpartum: atony,

trauma, uterine rupture)

Sepsis (pyelonephritis, chorioamnionitis, puerperal

sepsis)

Intrinsic Acute tubular necrosis (d/t septic abortion) Preeclampsia

HELLP Syndrome (most common cause of AKI in

pregnancy)

Acute fatty liver disease of pregnancy

Thrombotic thrombocytopenic purpura (TTP)

Atypical hemolytic uremic syndrome (aHUS)

Post-Renal n/a Uteropelvic obstruction (gravid uterus, masses, renal

stone, normally seen with a pelvic pathology)

Surgical (ureter damage, post surgical obstruction)

Neoplasm

AKI in Pregnancy

• Non-pregnant AKI definitions (ie KDIGO) not appropriate during pregnancy

• No consensus definition of AKI in pregnancy, making it difficult to establish incidence

rate

• Acute renal failure was found in 4.52 per 10,000 US births from 2008-2009

ACOG Renal Insufficiency

Definition

↑SCr ˃ 1.1mg/dL or doubling SCr in the absence of other renal

disease

Definition used as part of diagnostic criteria for severe preeclampsia

Non-

pregnant adult

First

Trimester

Second

Trimester

Third

Trimester

Normal Ref Range

Creatinine (mg/dL)

.05-.09 0.4-0.7 0.4-0.8 0.4-0.9

AKI in Pregnancy

Increased renal function may mask early AKI symptoms

Lab values considered normal in non-pregnant women may indicate

worsening renal function in pregnant patients

Increasing proteinuria in pregnant patients with CKD may be normal in the

progression of pregnancy and not indicative of worsening function

Difficult to establish baseline GFR in pregnancy without 24h collection

Oliguria in preeclampsia is part of disease pathology in response to

intravascular depletion and may not indicate worsening renal fn

Management of AKI in Pregnancy

• Management of AKI in pregnancy should focus on management of the cause of AKI

and consider multiple causes

• Should also consider non-pregnancy related causes of AKI

• Renal biopsy rarely indicated, usually delayed until after delivery

• Should use multidisciplinary approach

• Renal therapy

– Low dose dopamine - Not recommended

– Furosemide - Not recommended

– Fenoldopam - Needs further research

– N-acytylcysteine - Needs further research

– Albumin - Needs further research

Clinical Assessment of Pregnant Women with Raised Creatinine

AKI in Pregnancy Management

• Consider transfer to specialty center if not responding to initial conservative

measures

• Review medications and discontinue nephrotoxic drugs if possible

– Renally cleared medications may need adjustment

– A single loading dose of magnesium sulfate for preeclampsia considered safe even in renal failure

• Should optimize status before delivery

– If BUN >80 mg/dL or K >5.5mEq/L, dialysis should be performed before elective vaginal or c-section

delivery

• Neuraxial anesthesia is preferred to general anesthesia

• Considerations for general anesthesia in the setting of AKI similar to that for CKD

Obstetric Kidney Disease Summary

• Kidney disease in pregnancy increases risk of adverse outcomes to both the mother and the fetus

• Perioperative management of obstetric patients with CKD should consider CKD staging and related

physiologic changes

• Intraop management of CKD should consider individual need for CVP monitoring dependent on

fluid status, adjustments of anesthetic medications as appropriate, and protection of HD fistula if

present

• Multiple renal physiologic changes in pregnancy make AKI in pregnancy hard to define and difficult

to measure. Lab values considered normal in non-pregnant women may be indicative of AKI in

pregnancy

• Obstetric AKI management should be individualized to consider the cause of the AKI

• Considerations should be made to discontinue nephrotoxic drugs as appropriate and monitor

bleeding risk related to neuraxial anesthesia

References

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