Care of the Burned Pregnant Patient

Introduction

Approximately 8% of women experience trauma during their pregnancies. Trauma in pregnancy is the most common cause of nonobstetric-related death; more generally, trauma is the leading cause of death in the age group under 40 in the United States. Women in their reproductive years are the population at the greatest risk of trauma. While it is rare to see a pregnant woman in the burn ICU in industrialized nations, burn trauma is a great risk to pregnant women in developing countries. Correspondingly, recent literature regarding the care of burned pregnant patients more commonly comes from journals in these developing countries and consists mainly of small studies and case reports. Burn injury during pregnancy tends to happen in the home environment. In developing countries, this may be in part attributable to the large proportion of women who attempt suicide via self-immolation.

Due to the particular paper paucity pertaining to pregnant patients, there is no great consensus on the population of burned pregnant women, size of burn disease burden in the population, or mortality of mother and fetus. However, what does exist in the literature reveals that the maternal mortality rate exceeds 50% and has been reported at 100% when total body surface area (TBSA) burned exceeds 40–60%. This statistic remains unchanged from Rode's study in 1990 showing that when TBSA was greater than 50%, maternal survival “was unlikely.” These appalling mortality data contrast a contemporaneous study by Herndon et al. that determined the lethal burn size for 50% (LD50) of pediatric patients reached 98% TBSA burned. Despite progress made in survival rates of other burned populations, pregnant burned victims suffer the same mortality rates as in the 1960s. In a recent study, 60% of burned pregnant burned patients died, with an overall 50% mortality rate of the fetus. As could be predicted, fetal survival greatly depends on maternal survival, although there is a high spontaneous labor rate among burned pregnant patients. While pregnancy does not greatly influence treatment protocols, it might factor into maternal outcome following thermal insult, given the enormously high mortality rate of pregnant women with severe burn injury when compared to the mortality rates of nonpregnant women and men with comparable burn wound sizes. However, more study is obviously necessary.

Mortality Factors

A consensus in literature exists: burn size correlates most significantly with the mortality of both mother and fetus. Large burn size is the single most predictive indicator for mortality. The odds of mortality of the mother rise by 1.08 per percentage of TBSA burned ( P < 0.0001). Furthermore, there is an association between mortality, TBSA burned, and the incidence of intentional burns. Women who attempt suicide via self-immolation had greater TBSA and resultantly higher mortality rates, especially those with greater than 50% TBSA burned. Rode reported a direct relationship between the size of burn and the frequency rates of spontaneous abortion and premature delivery. Rezavand et al. demonstrated that, in every trimester, maternal TBSA burned positively correlated with fetal death as well as maternal demise. Agarwal found fetal loss occurred at a higher rate than maternal death even at greater maternal TBSA burned.

The second strongest predictor of mortality of both mother and fetus is smoke inhalation, the treatment of which remains controversial. Maternal fatalities and mothers with fetal losses were more common in those with concurrent inhalation injuries. The resultant hypoxia strongly correlates with maternal and fetal death. Closed and structural fires emit smoke potentially imbued with cyanide (CN) and carbon monoxide (CO) gases. Upon inhalation, CO and CN demonstrate synergistic effects; furthermore, they concentrate at higher levels in the fetus than the mother as fetal hemoglobin binds CO and CN more avidly than maternal. As such, providers must treat two patients with awareness of potential effects of CO and CN poisoning on both mother and child. Facial burns, large burns, and self-inflicted, intentional burns all strongly associate with inhalation injury. Significant thermal injury in the pregnant patient population can have not only direct but indirect effects on the pulmonary system. Unique to the pregnant burn patient, vital lung capacity decreases while mucosal edema, oxygen consumption, and minute ventilation increase. As with the severely burned nonpregnant patient, should a pregnant burn victim be suspected of suffering from inhalation injury, emergent intubation ought to be instituted. Given the known physiologic changes of pregnancy, which are compounded by burn edema, early intubation in the severely burned pregnant patient should be strongly considered. Hydroxycobalamin, the cyanide antidote recommended in Chapter 32 , is a pregnancy category C drug and should only be used if the benefits outweigh the risks because cyanide crosses the placenta and will poison the fetus to a greater extent than the mother.

Gestational age was also a factor reported in several studies. Argawal found fetal survival in the third trimester correlated less to maternal survival but rather strongly to gestational age. Liu determined gestational age-specific risk of birth to be greater among the population of injured mothers than noninjured in each gestational week until week 38, irrespective of medical condition. Gestational age is not the sole criteria for neonatologists and obstetricians in determining viability of a fetus. The fetal weight benchmark of 500 g has been adopted, which is the lower size limit at which intubation is feasible. Given the potentiality of obstetric intervention, it is imperative to precisely ascertain the gestational age and weight of the fetus via fetal ultrasound and menstrual and sexual patient history data early in the management of acute burns.

Hypovolemic shock and sepsis have also been found to be complications resulting in maternal and fetal death. Recurrent septicemia is a major challenge in the management of a severely burned obstetric patient. Intraabdominal hypertension and abdominal compartment syndrome develop in most severely burned patients within 48 hours of injury. Intraabdominal hypertension is present when intraabdominal pressure measures in excess of 12 mm Hg, and abdominal compartment syndrome exists when intraabdominal pressure is greater than 20 mm Hg, particularly if additional organs display dysfunction. Pregnancy induces physiologic changes in all major maternal organ systems, mimicking early perturbations seen in multisystem organ dysfunction (MOD). All these complications potentially lead to MOD, compounding the existing state present in the pregnant population and further jeopardizing severely burned obstetric patients.

Fetal Viability

Managing obstetrical complications provides an additional challenge to the burn team. Second to death of the mother, placental abruption is the most common cause of the death of the fetus following trauma. Due to the intense kinetics undergone by a pregnant patient postburn, the fetus often spontaneously delivers. In layman's terms, this is a miscarriage. Consistently studies show that fetal mortality rates were highest during the first trimester in the setting of major burns. However, with aggressive fetal monitoring, appropriate obstetrical intervention can preserve the life of the fetus earlier in the course of pregnancy. Studies indicate this approach starts approximately in the 22nd week of gestation. Determining the gestational age and weight of the fetus enables the healthcare team to most effectively guide this care. In a large study, Linder et al. demonstrated that early preterm, low-risk deliveries increased the risk of fetal complications with higher rates of neonatal ICU (NICU) admission, sepsis, and antibiotic treatment as compared to late-term neonates or the gestational control population. While the study only began evaluation at gestational week 37 of low-risk singleton deliveries, it did show that neonatal morbidity risk corresponds with early term deliveries. The burn, obstetric, and neonatal teams must collectively weigh the risks of preterm delivery against the risks of the fetus remaining in utero and besieged by the expected effects of severe burn trauma.