Smoke Inhalation Injury in a Pregnant Patient: A Literature Review of the Evidence and Current Best Practices in the Setting of a Classic Case

Neonatal hypoxic-ischemic encephalopathy after acute carbon monoxide intoxication during pregnancy. A case report and brief review of the literature

Carbon monoxide (CO) poisoning during pregnancy is a rare occurrence, associated with high maternal and fetal mortality rates. As CO can cross the placenta, leading to intrauterine hypoxia, CO intoxication can result in neurological sequelae and neurologic complications in fetuses who survive. We report a case of a preterm newborn acutely exposed to CO in-utero and delivered by emergent cesarean section at the 31st week of gestation due to the severe burns suffered by the mother following an indoor boiler explosion. As CO has serious adverse effects both on the mother and fetus, it is important to recognize and treat poisoning in a timely manner. Despite maternal blood CO levels, CO intoxication at critical stage of central nervous system development can lead to hypoxic-ischemic lesions, thus interdisciplinary care and follow up for these patients are mandatory.

S2k guideline diagnosis and treatment of carbon monoxide poisoning

Carbon monoxide (CO) can occur in numerous situations and ambient conditions, such as fire smoke, indoor fireplaces, silos containing large quantities of wood pellets, engine exhaust fumes, and when using hookahs. Symptoms of CO poisoning are nonspecific and can range from dizziness, headache, and angina pectoris to unconsciousness and death. This guideline presents the current state of knowledge and national recommendations on the diagnosis and treatment of patients with CO poisoning. The diagnosis of CO poisoning is based on clinical symptoms and proven or probable exposure to CO. Negative carboxyhemoglobin (COHb) levels should not rule out CO poisoning if the history and symptoms are consistent with this phenomenon. Reduced oxygen-carrying capacity, impairment of the cellular respiratory chain, and immunomodulatory processes may result in myocardial and central nervous tissue damage even after a reduction in COHb. If CO poisoning is suspected, 100% oxygen breathing should be immediately initiated in the prehospital setting. Clinical symptoms do not correlate with COHb elimination from the blood; therefore, COHb monitoring alone is unsuitable for treatment management. Especially in the absence of improvement despite treatment, a reevaluation for other possible differential diagnoses ought to be performed. Evidence regarding the benefit of hyperbaric oxygen therapy (HBOT) is scant and the subject of controversy due to the heterogeneity of studies. If required, HBOT should be initiated within 6 h. All patients with CO poisoning should be informed about the risk of delayed neurological sequelae (DNS).

Hypoxia: A teratogen underlying a range of congenital disruptions, dysplasias, and malformations

In this review, we explore evidence that hypoxia in the developing human fetus can lead not only to the more commonly accepted disruptive-type defects, but also patterns of anomalies that suggest that hypoxia can exert a more classic teratogenic effect, using the brain as one example. We review neuropathology in the context of intrauterine hypoxia, particularly as it relates to carbon monoxide poisoning, in utero strokes, and homozygous alpha-thalassemia. In general, the associated brain injuries resemble those seen with other causes of hypoxic-ischemic injury. Fetal strokes during development usually lead to loss of brain tissue in areas that do not follow a typical embryologic pattern, and therefore are considered disruptions. However, there is also evidence that fetal brain ischemia can cause more classically recognized patterns of abnormal embryonic neuronal migration and organization such as polymicrogyria, cortical dysplasia, or dysgenesis, including select types of focal cortical dysplasia. This study summarizes available literature and evidence to raise clinicians' awareness regarding the association between hypoxia and congenital anomalies, including brain malformations.

Toxic Blood Hydrogen Cyanide Concentration as a Vital Sign of a Deceased Room Fire Victim-Case Report

Carbon monoxide (CO) and hydrogen cyanide (HCN) are two common toxic products of combustion. HCN concentrations of fire victims are not routinely determined in most legal medicine services in Romania. We present the case of a room fire victim in which we evaluated the concentrations of HCN and carboxyhemoglobin (COHb), their contribution to the mechanism of death, and the possibility that HCN concentration can be interpreted as vital sign. COHb was determined by spectrophotometry. HCN was spectrophotometrically determined with ninhydrin in postmortem blood samples after its removal with 20% phosphoric acid and uptake into a solution of potassium carbonate. The presence of ethyl alcohol was determined by gas chromatography. The COHb concentration was 6.15%, while the blood HCN concentration was 1.043 µg × mL⁻¹ and the total HCN was 1.904 µg × ml⁻¹. A blood alcohol content of 4.36 g‰ and a urine alcohol content of 5.88 g‰ were also found. Although the fire produced a considerable amount of soot, and there were signs of inhalation of soot particles, the COHb level cannot be interpreted as a vital sign. Toxic concentrations of HCN and total HCN can be interpreted as a vital sign and indicates a contributive effect of HCN in the mechanism of death.

Hyperbaric oxygen therapy in carbon monoxide poisoning in pregnancy: Maternal and fetal outcome

OBJECTIVE

Closer monitoring and treatment is vital for pregnant carbon monoxide (CO) poisoning cases due to fetal poisoning component. Permanent damage can occur in both the mother and the baby. It may cause stillbirth even though no serious clinical symptoms occur in the mother. Hyperbaric oxygen (HBO) treatment is advised for all pregnant patients regardless of their clinical symptoms. Pregnant CO poisoning patients that received HBO treatment and their fetal status were evaluated in this study.

METHODS

Pregnant patients poisoned with CO treated in the same hyperbaric clinic were evaluated. Pregnant patients that received HBO treatment in a multiplace chamber were evaluated in terms of clinical status, demographic structure, laboratory tests, fetal effects and progress of the fetus until birth and 6 months postpartum.

RESULTS

A total number of 32 pregnant cases were treated. COHb values were over 20% (min 6.9- max 40.2) in 23 patients, 11 patients had a history of syncope. All patients took HBO treatment under 2.4 ATA pressure for 120 min. 3 patients received more than 1 session of HBO treatments due to fetal stress; all other cases took 1 session of HBO treatment. No spontaneous abortus occurred in early follow-ups; only 4 babies were born prematurely. 2 of the babies were lost in the early phases after birth, due to causes non-related to CO poisoning complications (cyanotic heart disease, necrotising enterocolitis). No significant difference were observed in the comparison of laboratory results of patients with syncope and of those who did not have syncope and comparison of patients with COHb value higher than 20% and patients with COHb value lower than 20% (p > 0.05).

CONCLUSION

HBO is not advisable for pregnant patients except for CO poisoning. In this study it is observed that HBO treatment under 2.4 ATA pressure for 120 min has no harmful effects on the mother and the fetus. It is observed that continuation of HBO treatment in the cases with fetal distress findings has beneficial effects. COHb levels and syncope were shown to have no significant effect on clinical symptoms and on blood tests.

The Diagnosis and Treatment of Carbon Monoxide Poisoning

BACKGROUND

The symptoms of carbon monoxide (CO) poisoning are nonspecific, ranging from dizziness and headache to unconsciousness and death. A German national guideline on the diagnosis and treatment of this condition is lacking at present.

METHODS

This review is based on a selective literature search in the PubMed and Cochrane databases, as well as on existing guidelines from abroad and expert recommendations on diagnosis and treatment.

RESULTS

The initiation of 100% oxygen breathing as early as possible is the most important treatment for carbon monoxide poisoning. In case of CO poisoning, the reduced oxygen-carrying capacity of the blood, impairment of the cellular respiratory chain, and immune-modulating processes can lead to tissue injury in the myocardium and brain even after lowering of the carboxyhemoglobin (COHb) concentration. In patients with severe carbon monoxide poisoning, an ECG should be obtained and biomarkers for cardiac ischemia should be measured. Hyperbaric oxygen therapy (HBOT) should be critically considered and initiated within six hours in patients with neurologic deficits, unconsciousness, cardiac ischemia, pregnancy, and/or a very high COHb concentration. At present, there is no general recommendation for HBOT, in view of the heterogeneous state of the evidence from multiple trials. Therapeutic decision-making is directed toward the avoidance of sequelae such as cognitive dysfunction and cardiac complications, and the reduction of mortality. Smoke intoxication must be considered in the differential diagnosis. The state of the evidence on the diagnosis and treatment of this condition is not entirely clear. Alternative or supplementary pharmacological treatments now exist only on an experimental basis.

CONCLUSION

High-quality, prospective, randomized trials that would enable a definitive judgment of the efficacy of HBOT are currently lacking.

Carbon Monoxide and Cyanide Poisoning in the Burned Pregnant Patient: An Indication for Hyperbaric Oxygen Therapy

Carbon monoxide (CO) is a small molecule poison released as a product of incomplete combustion. Carbon monoxide binds hemoglobin, reducing oxygen delivery. This effect is exacerbated in the burned pregnant patient by fetal hemoglobin that binds CO 2.5- to 3-fold stronger than maternal hemoglobin. With no signature clinical symptom, diagnosis depends on patient injury history, elevated carboxyhemoglobin levels, and alterations in mental status. The standard of care for treatment of CO intoxication is 100% normobaric oxygen, which decreases the half-life of CO in the bloodstream from 5 hours to 1 hour. Hyperbaric oxygen (HBO2) is a useful adjunct to rapidly reduce the half-life of CO to 20 minutes and the incidence of delayed neurologic sequelae. Because of the slow disassociation of CO from hemoglobin in the fetus, there is a far stronger indication for HBO2 in the burned pregnant patient than in other burn patient populations.Cyanide intoxication is often a comorbid disease with CO in inhalation injury from an enclosed fire, but may be the predominant toxin. It acts synergistically with CO to effectively lower the lethal doses of both cyanide and CO. Diagnosis is best made in the presence of high lactate levels, carboxyhemoglobin concentrations greater than 10%, injury history of smoke inhalation from an enclosed fire, and alterations in consciousness. While treatment with hydroxocobalamin is the standard of care and has the effect of reducing concomitant CO toxicity, data indicate cyanide may also be displaced by HBO2.Carbon monoxide and cyanide poisoning presents potential complications impacting care. This review addresses the mechanism of action, presentation, diagnosis, and treatment of CO and cyanide poisonings in the burned pregnant patient and the use of HBO2 therapy.

Utility and outcomes of hydroxocobalamin use in smoke inhalation patients

INTRODUCTION

Hydroxocobalamin has been available for use for suspected cyanide toxicity in smoke inhalation patients in the United States since 2006. Our study compares outcomes of patients who received hydroxocobalamin to historical controls who did not.

METHODS

In this retrospective review, patients administered hydroxocobalamin (2008-2014) were compared to historical controls (2002-2008). Patients <18 years, patients who received an alternate antidote, and patients without suspicion of smoke inhalation injury were excluded. Mortality was the primary outcome. Secondary outcomes evaluated were 7-day change in creatinine, culture-proven pneumonia, days on mechanical ventilation, ventilator- free days (VFD), ICU length of stay (ICU LOS), and hospital length of stay (HLOS).

RESULTS

A total of 138 patients in the hydroxocobalamin group and 135 in the control group were identified. Mortality rate was similar between both groups (29% vs. 28%, p=0.90). Hydroxocobalamin was associated with lower pneumonia rate (23% vs. 49%, p<0.01), less ventilator days (4 days vs. 7 days, p<0.01), and increased VFD (20 days vs. 11 days, p=0.01) compared to controls. Shorter ICU LOS (6 days vs. 10 days, p=0.03) and a trend toward lower HLOS (7 day vs. 11 days, p=0.06) were also found in patients who received hydroxocobalamin.

CONCLUSIONS

Routine administration was associated with lower rate of pneumonia, faster liberation from the ventilator, and reductions in intensive care unit stay. Burn centers should consider its empiric use in suspected smoke inhalation patients.

Burns During Pregnancy: Implications for Maternal-Perinatal Providers and Guidelines for Practice

IMPORTANCE

When a major burn is suffered during pregnancy, the obstetric provider is challenged to respond on an evidence basis because personal experience usually is lacking. Currently, there is a paucity of publications to inform the obstetrician, guide practice, and impact early critical decision making.

OBJECTIVE

The aims of this study were to summarize the available information on early management of burns during pregnancy and to identify components of best practices for optimal outcome.

EVIDENCE ACQUISITION

The PubMed database was searched for relevant titles and abstracts involving pregnant patients suffering from second-/third-degree burns. Among these studies, the bibliographies were investigated for further relevant literature. A total of 114 studies were identified during the initial search, and only studies published in English and French were included for a total of 42. Variable data were available for 1141 patients, with complete data for 139 cases. Mediation and regression analysis were used for available data. Insufficient data were available to undertake a systematic review.

RESULTS

Total body surface area of burns (TBSAB) was positively associated with maternal death, and the odds of maternal mortality increase by 1.08 per percentage increase of TBSAB (P < 0.001). Fetal survival depends on maternal survival (P ≤ 0.001). Maternal survival declines incrementally when TBSAB exceeds 55%, and inhalation injury further exacerbates maternal-perinatal risk.

CONCLUSIONS

Emergent assessment of the pregnant burn victimincludes determination of gestational age, extent of TBSAB, presence of inhalation injury, and continuous fetal monitoring. If gestational age is 24 weeks or longer and TBSAB exceeds 55%, urgent cesarean delivery appears desirable for the mother and baby.

RELEVANCE

A specific analysis of maternal-perinatal outcome based on TBSAB and gestational age is relevant to obstetric and emergency providers who provide care to pregnant burn patients.

A modern literature review of carbon monoxide poisoning theories, therapies, and potential targets for therapy advancement

The first descriptions of carbon monoxide (CO) and its toxic nature appeared in the literature over 100 years ago in separate publications by Drs. Douglas and Haldane. Both men ascribed the deleterious effects of this newly discovered gas to its strong interaction with hemoglobin. Since then the adverse sequelae of CO poisoning has been almost universally attributed to hypoxic injury secondary to CO occupation of oxygen binding sites on hemoglobin. Despite a mounting body of literature suggesting other mechanisms of injury, this pathophysiology and its associated oxygen centric therapies persists. This review attempts to elucidate the remarkably complex nature of CO as a gasotransmitter. While CO's affinity for hemoglobin remains undisputed, new research suggests that its role in nitric oxide release, reactive oxygen species formation, and its direct action on ion channels is much more significant. In the course of understanding the multifaceted character of this simple molecule it becomes apparent that current oxygen based therapies meant to displace CO from hemoglobin may be insufficient and possibly harmful. Approaching CO as a complex gasotransmitter will help guide understanding of the complex and poorly understood sequelae and illuminate potentials for new treatment modalities.

Carbon Monoxide Poisoning during Pregnancy: Presentation of a Rare Severe Case with Fetal Bladder Complications

Carbon monoxide poisoning during pregnancy is a rare and potentially serious condition. Fetal complications are uncommon, related to anoxic lesions. The severity of these complications does not depend on the level of maternal COHb. We report the case of a 22-year-old pregnant woman who at 30 weeks of gestation had carbon monoxide poisoning secondary to a fire in her home, complicated by cardiac arrest and severe fetal damage. The child had not brain damage, but presented bladder lesions not previously described, with urinary ascites complicating megacystis.

Delivery and management of a preterm infant in the burn unit: a multidisciplinary approach

Burns during pregnancy can have profound effects on both the mother and her fetus. While the mother can suffer cardiovascular collapse, infection, hemorrhage and inhalation injury with respiratory failure, the fetus is affected through the placenta by all of these changes as well as by the transfer of drugs administered to the mother. We report a case of severely burned female patient at 29 weeks gestation, who, due to deteriorating maternal condition, was delivered and managed at 32 weeks gestation by a multidisciplinary team. To the best of our knowledge this is the first reported case of a preterm infant delivered in a burn unit.

Hydroxocobalamin in cyanide poisoning

INTRODUCTION

On theoretical grounds, hydroxocobalamin is an attractive antidote for cyanide poisoning as cobalt compounds have the ability to bind and detoxify cyanide. This paper reviews the pharmacokinetic and pharmacodynamic aspects of hydroxocobalamin, its efficacy in human cyanide poisoning and its adverse effects.

METHODS

PubMed was searched for the period 1952 to April 2012. A total of 71 papers were identified in this way; and none was excluded. PHARMACOKINETICS AND PHARMACODYNAMICS: Pharmacokinetic studies in dogs and humans suggest a two-compartment model, with first order elimination kinetics. Pharmacodynamic studies in animals suggest that hydroxocobalamin would be a satisfactory antidote for human cyanide poisoning. EFFICACY IN HUMAN POISONING: There is limited evidence that hydroxocobalamin alone is effective in severe poisoning by cyanide salts. The evidence for the efficacy of hydroxocobalamin in smoke inhalation is complicated by lack of evidence for the importance of cyanide exposure in fires and the effects of other chemicals as well as confounding effects of other therapeutic measures, including hyperbaric oxygen. Evidence that hydroxocobalamin is effective in poisoning due to hydrogen cyanide alone is lacking; extrapolation of efficacy from poisoning by ingested cyanide salts may not be valid. The rate of absorption may be greater with inhaled hydrogen cyanide and the recommended slow intravenous administration of hydroxocobalamin may severely limit its clinical effectiveness in these circumstances.

ADVERSE EFFECTS

Both animal and human data suggest that hydroxocobalamin is lacking in clinically significant adverse effects. However, in one human volunteer study, delayed but prolonged rashes were observed in one-sixth of subjects, appearing 7 to 25 days after administration of 5 g or more of hydroxocobalamin. Rare adverse effects have included dyspnoea, facial oedema, and urticaria.

CONCLUSIONS

Limited data on human poisonings with cyanide salts suggest that hydroxocobalamin is an effective antidote; data from smoke inhalation are less clear-cut. Although clinically important reactions to hydroxocobalamin have not been seen, some, non-life threatening, adverse reactions can occur.