Page 1799 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1268 PART 11: Special Problems in Critical Care

pancuronium, vecuronium, and atracurium produce no adverse fetal Low-dose dopamine is not an established therapy for renal support, and
effects with short-term use in the gravida. Of these, cisatracurium should not be used for the purpose of treating ARF in pregnancy.
3
(pregnancy category B) may be preferred as it does not depend on
renal or hepatic function for elimination. When possible, left lateral ■ ACUTE LIVER FAILURE
patient positioning will minimize the decrease in venous return that In pregnancy, de novo liver function test abnormalities are uncommon,
occurs with positive pressure ventilation. Maternal arterial blood gases evident in less than 5% of pregnancies in the United States. Acute liver
should be assessed frequently in those with severe acid-base or respira- failure in pregnancy is even more uncommon. In spite of periportal or
tory derangements. During mechanical ventilation, fetal monitoring focal parenchymal necrosis and fibrin deposition in the sinusoids seen
154
should be ongoing, and acute ventilatory changes that lead to even subtle on histopathology, preeclampsia and the HELLP syndrome rarely lead
levels of fetal decompensation should be avoided. to liver failure. However, subcapsular hematoma, intraparenchymal
If life-threatening hypoxemia persists despite maximizing ventilatory hemorrhage, or hepatic rupture or infarction may occur. These compli-
strategies, ECMO may be considered. Data on the use of ECMO dur- cations are an indication for delivery, and close monitoring is required
ing pregnancy are limited, but several case reports support its use as a as worsening thrombocytopenia and increasing LDH levels may be seen
salvage intervention. As high flow is needed, femoral venous access up to 48 hours after delivery. Acute fatty liver of pregnancy (AFLP)
160
165
in pregnant patients is not ideal. However, one group reported success is a rare complication of pregnancy, most commonly presenting in the
by accessing both femoral veins in addition to the jugular vein. As third trimester. It is associated with significant maternal (18%) and
160
with nonpregnant patients, better outcomes in pregnant patients may be fetal (23%) mortality. It is thought to result from deficiencies of the
seen with the implementation of ECMO early in the phase of refractory enzymes of mitochondrial fatty acid beta-oxidation. When a woman
respiratory failure.
heterozygous for these enzyme defects is pregnant with a homozygous
fetus, fetal fatty acids accumulate and are detected in maternal circula-
OTHER DISORDERS OF PREGNANCY tion. This accumulation leads to hepatic fat deposition and impaired
166
■ VENOUS THROMBOEMBOLISM hepatic function. Risk factors for AFLP include multiple gestations and
a first pregnancy. Patients present with nonspecific symptoms such as
Venous thromboembolic disease is reviewed in full in Chap. 39. headache, nausea and vomiting, right upper quadrant or epigastric pain,
Pregnancy is a well-known risk factor for deep vein thrombosis and pul- malaise, and anorexia. Jaundice, hepatic encephalopathy, and coagulop-
monary embolism. Importantly, the increased risk of thromboembolic athy may follow 1 to 2 weeks later. Cholestasis with mild to severe eleva-
disease continues into the postpartum period. Deep vein thrombosis tions in serum aminotransferases is noted. Ultrasonography may show
161
occurs on the left side in up to 80% of pregnant patients. In addition, it increased echogenicity. While CT scanning is more sensitive, and may
is more likely to occur higher in the pelvis, for which ultrasound is less demonstrate decreased attenuation, this modality carries the risk of fetal
167
diagnostically sensitive. Chest imaging is an important complement to radiation exposure. Liver biopsy is definitive but must be undertaken
leg ultrasound when thromboembolic disease is suspected. 113,162,163 with caution if there is an attendant coagulopathy. Histology in AFLP
reveals microvesicular fatty infiltration detected on frozen sections with
■ ACUTE RENAL FAILURE oil red O staining. When fulminant hepatic failure ensues, it can be
While the incidence of acute renal failure (ARF) in pregnancy has fallen complicated by encephalopathy, renal failure, pancreatitis, hemorrhage,
DIC, seizures, coma, or death. Because deterioration may occur rapidly,
significantly with improved preeclampsia management and a decline expectant management is generally not advised, and treatment includes
in illegal abortions, the associated mortality and long-term morbidity delivery of the fetus. Jaundice, liver dysfunction, and DIC may worsen
remain significant. ARF can complicate hemorrhage, preeclampsia, during the first week after delivery but should improve thereafter. Full
164
amniotic fluid embolism, or acute fatty liver of pregnancy. Preeclampsia maternal recovery is the typical outcome although fulminant hepatic
is a particularly important condition associated with ARF. The develop- failure requiring liver transplantation has been reported. Infant compli-
ment of placental abruption, the HELLP syndrome, DIC, or hemorrhage cations include hypoglycemia, hypotonia, acute or chronic skeletal and
further increases the risk of ARF in preeclampsia. Sepsis and infection cardiac muscle dysfunction, and sudden infant death syndrome.
are also important risk factors for ARF in pregnancy. Even when not
complicated by sepsis, pyelonephritis in pregnant patients is associated
with a greater risk of ARF compared to pyelonephritis in nonpregnant MAINTENANCE OF THE INTERNAL ENVIRONMENT
compression from the gravid uterus, which may be more likely to occur ■ ACID-BASE STATUS
patients. Finally, there are case reports of ARF from genitourinary
164
in the setting of increased uterine distention with polyhydramnios, During labor, the normal respiratory alkalosis of pregnancy worsens
multiple gestations, or uterine fibroids. Idiopathic postpartum ARF is an with maternal hyperventilation, although current evidence suggests this
unusual complication of pregnancy and may occur days to weeks after a is not clinically relevant. Unlike the spontaneous hyperventilation of
168
normal pregnancy and delivery. The etiology is unknown but it may be labor and delivery, a persistent respiratory alkalosis has been demon-
a variant of HUS or TTP with predominantly renal involvement. strated to decrease uteroplacental blood flow and result in fetal asphyxia
The evaluation of the pregnant patient with renal insufficiency is sim- in animal models. Metabolic alkalosis also is thought to decrease
156
ilar to that of the nonpregnant patient, keeping in mind that creatinine placental blood flow and impair fetal Pa O 2 . Since severe and persistent
169
levels in pregnancy are lower and a “normal” creatinine may indicate respiratory and metabolic alkaloses in critical illness are often a result of
renal injury. Renal biopsy is reserved for the minority of patients with medical treatment, such as excessive mechanical ventilation, nasogastric
ARF for whom a comprehensive clinical evaluation does not suggest suction, and diuretic use, close monitoring of maternal acid-base status
the diagnosis, especially the preterm gravida with suspected but uncon- should allow prevention or early correction of alkalemia.
firmed preeclampsia, where a biopsy showing an alternate diagnosis Acidemia may also be detrimental to the fetus. As reviewed, a mild
would avert delivery of a preterm fetus. increase in maternal Pa CO 2 is generally well tolerated, but permissive
Management of ARF in pregnancy includes treating the underlying hypercapnia that results in a significant respiratory acidosis is best
cause, preventing further damage, and providing supportive care and avoided. A mild, transient metabolic acidosis occurs in normal labor and
dialysis as necessary. Renal dysfunction associated with preeclampsia delivery, presumably as a result of hyperventilation and other muscle
and the HELLP syndrome should respond to delivery of the fetus, activity. While maternal lactate is transferred rapidly to the fetus, the
170
while TTP and HUS require plasmapheresis. A thorough evaluation for acidosis often resolves in the neonate within an hour of delivery. When
occult sepsis should be performed when the etiology of ARF is unclear. a maternal metabolic acidosis develops as a result of illness, treatment

section11.indd 1268 1/19/2015 10:52:24 AM