Acute carbon monoxide intoxication and hyperbaric oxygen in pregnancy

Maternal exposure to hyperbaric oxygen at the preimplantation stages increases apoptosis and ectopic Cdx2 expression and decreases Oct4 expression in mouse blastocysts via Nrf2-Notch1 upregulation and Nf2 downregulation

BACKGROUND

The environmental oxygen tension has been reported to impact the blastocyst quality and cell numbers in the inner cell mass (ICM) during human and murine embryogenesis. While the molecular mechanisms leading to increased ICM cell numbers and pluripotency gene expression under hypoxia have been deciphered, it remains unknown which regulatory pathways caused the underweight fetal body and overweight placenta after maternal exposure to hyperbaric oxygen (HBO).

RESULTS

The blastocysts from the HBO-exposed pregnant mice revealed significantly increased signals of reactive oxygen species (ROS) and nuclear Nrf2 staining, decreased Nf2 and Oct4 expression, increased nuclear Tp53bp1 and active caspase-3 staining, and ectopic nuclear signals of Cdx2, Yap, and the Notch1 intracellular domain (N1ICD) in the ICM. In the ICM of the HBO-exposed blastocysts, both Nf2 cDNA microinjection and Nrf2 shRNA microinjection significantly decreased the ectopic nuclear expression of Cdx2, Tp53bp1, and Yap whereas increased Oct4 expression, while Nrf2 shRNA microinjection also significantly decreased Notch1 mRNA levels and nuclear expression of N1ICD and active caspase-3.

CONCLUSION

We show for the first time that maternal exposure to HBO at the preimplantation stage induces apoptosis and impairs ICM cell specification via upregulating Nrf2-Notch1-Cdx2 expression and downregulating Nf2-Oct4 expression.

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.

Trauma in Pregnancy

Trauma is the leading cause of nonobstetric maternal death. Pregnant patients have a similar spectrum of traumatic injuries with a noted increase in interpersonal violence. A structured approach to trauma evaluation and management is recommended with several guidelines expanding on ATLS principles; however, evidence is limited. Optimal management requires understanding of physiologic changes in pregnancy, a team-based approach, and preparation for interventions that may including neonatal resuscitation. The principles of trauma management are the same in pregnancy with a systematic approach and initial maternal focused resuscitation..

Narrative minireview of the current status of hyperbaric oxygen therapy for pregnant women

We performed a narrative minireview for a PubMed search on March 31, 2023, using the keywords "pregnant" and "hyperbaric oxygen" to identify any related articles. Most reports have described pregnant women with carbon monoxide (CO) poisoning being treated by hyperbaric oxygen therapy (HBOT). HBOT helped improve the maternal condition and ensure normal fetal development. Some pregnant women with CO poisoning treated by HBOT suffered abortions or gave premature birth to low-weight babies or with congenital malformations. However, these results were considered sequelae of CO poisoning, not HBOT. We hypothesized that for pregnant women facing a life-threatening situation, for which the effectiveness of HBOT has previously been suggested, prioritizing the stabilization of the mother may also be beneficial for normal fetal development.

Perinatal Carbon Monoxide Poisoning: Treatment of a 2-Hour-Old Neonate with Hyperbaric Oxygen

A 41-year-old gravida 4 para 3 (G4P3) and 38 ^5/7 weeks pregnant woman presented to labor and delivery with dizziness, headache, and decreased fetal movement after 12 hours of exposure to carbon monoxide (CO) from a grill that was used inside for heat. The mother was hemodynamically stable, and her neurologic examination was intact. Her carboxyhemoglobin level, which was obtained 12 hours after removal from the CO exposure, was 7.4%. The fetus's heart rate was 173 beats per minute with moderate variability and one late appearing deceleration, not associated with contractions. The biophysical profile score was 2 of 8. The obstetrics team performed a routine cesarean section. The 1- and 5-minute Apgar's scores were 7 and 8, respectively. The arterial cord gas result was as follows: pH = 7.05, PCO ₂  = 71 mm Hg, pO ₂  = 19 mm Hg, bicarbonate = 14 mmol/L, and carboxyhemoglobin = 11.9%. The mother and infant were treated with hyperbaric oxygen therapy consisting of 100% oxygen at 2.4 atmosphere absolutes (ATA) for 90 minutes at 2.5 hours after delivery. Following one hyperbaric oxygen treatment, the infant was transitioned to room air and routine postpartum treatment and was discharged 3 days later in good condition. Hyperbaric oxygen treatment was well tolerated in this neonate.

Carbon Monoxide Poisoning

Carbon monoxide is a colorless, odorless, highly toxic gas primarily produced through the incomplete combustion of organic material. Carbon monoxide binds to hemoglobin and other heme molecules, causing tissue hypoxia and oxidative stress. Symptoms of carbon monoxide poisoning can vary from a mild headache to critical illness, which can make diagnosis difficult. When there is concern for possible carbon monoxide poisoning, the diagnosis can be made via blood co-oximetry. The primary treatment for patients with carbon monoxide poisoning is supplemental oxygen, usually delivered via a nonrebreather mask. Hyperbaric oxygen can also be used, but the exact indications are controversial.

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.

Carbon monoxide poisoning during pregnancy treated with hyperbaric oxygen

Acute carbon monoxide (CO) intoxication during pregnancy causes fetal death and teratogenic effects. Hyperbaric oxygen (HBO2) therapy has the potential to improve them. HBO2 therapy should be considered to treat CO intoxication during pregnancy.

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.

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.

Clinical management and progress in sudden sensorineural hearing loss during pregnancy

Sudden sensorineural hearing loss (SSNHL) is a relatively rare, but distressing, disease in pregnant women. Little is known about the causes, clinical manifestations, treatments, and prognosis of SSNHL. Some hypotheses have been proposed to explain the pathophysiological mechanism of SSNHL, but most of them have not been identified. This article reviews the existing literature to present a summary of this clinical problem. Most patients suffer from SSNHL in the second or third trimester, and show moderate to profound hearing loss. The interval between the initial treatment and onset of hearing loss is less than 10 days in most patients. Some patients with SSNHL show tinnitus, vertigo, or dizziness, and fullness of the ear. Although some patients have a tendency for self-cure, treatment with intravenous dextran 40 combined with intratympanic corticosteroids is probably a safe and effective therapeutic strategy for pregnant patients with SSNHL. Further clinical research is necessary to identify the best therapeutic strategy for these patients.

SCUBA Diving in Pregnancy

OBJECTIVE

Obstetrical care providers may occasionally encounter women with questions about the safety of Self-Contained Underwater Breathing Apparatus (SCUBA) diving in pregnancy. This article provides an overview of safety issues associated with basic SCUBA diving and offers guidance to practitioners about how to evaluate and counsel pregnant women about the associated maternal and fetal risks. Basic diving physiology is reviewed and the implications of SCUBA diving during pregnancy are discussed. A literature review examined available animal and human data about the potential adverse effects of the physiological changes of pregnancy on divers, the impact of pressure changes during diving, and possible consequences of hyperbaric gas exposure and rapid decompression on mother and fetus.

DATA SOURCES

Studies were found by searching the terms "scuba diving," "pregnancy," "fetus," "decompression illness," "hyperbaric medicine," and "animal studies" in the databases Medline, Pubmed, and Embase. Reference lists from existing articles and reports from identified diving magazines were also reviewed. Studies were limited to the English language and included publications until 2016.

STUDY SELECTION

All relevant human studies were selected. Five retrospective studies and one prospective study assessing the antenatal and postnatal outcomes of women who participated in SCUBA diving while pregnant were reviewed.

DATA SYNTHESIS

Published data was limited in both quantity and quality. The authors' experience with SCUBA diving together with a background in obstetrics allowed themes to be explored and recommendations developed.

CONCLUSIONS

In addition to established risks of SCUBA diving, pregnant women are at increased risk due to changes in body habitus (affecting equipment fitting and balance). Animal data suggest possible adverse fetal effects due to fetal decompression illness (DCI) and hyperbaric oxygen exposure. Human data, though generally reassuring, are of poor quality and thus do not completely exclude adverse outcomes. In general, women should be cautioned to avoid diving during pregnancy, but inadvertent exposure to recreational diving in early pregnancy is not a reason for pregnancy termination.

Clinical chameleons: an emergency medicine focused review of carbon monoxide poisoning

Carbon monoxide (CO) is a colorless, odorless gas that is found in the environment, in the home, and in the human body as a normal part of mammalian metabolism. Poisoning from CO, a common exposure, is associated with significant morbidity and mortality if not recognized and treated in a timely manner. This review evaluates the signs and symptoms of CO poisoning, conditions that present similar to CO poisoning, and an approach to the recognition and management for CO poisoning. CO poisoning accounts for thousands of emergency department visits annually. If not promptly recognized and treated, it leads to significant morbidity and mortality. CO poisoning poses a challenge to the emergency physician because it classically presents with non-specific symptoms such as headache, dizziness, nausea, and vomiting. Due to nonspecific presentations, it is easily mistaken for other, more benign diagnoses such as viral infection. The use of specific historical clues such as exposure to non-conventional heat sources or suicide attempts in garages, as well as the use of targeted diagnostic testing with CO-oximetry, can confirm the diagnosis of CO poisoning. Once diagnosed, treatment options range from observation to the use of hyperbaric oxygen. CO poisoning is an elusive diagnosis. This review evaluates the signs and symptoms CO poisoning, common chameleons or mimics, and an approach to management of CO poisoning.

Case Report of Carbon Monoxide Poisoning in a Pregnant Patient: Mother Died, Baby Survived

Carbon monoxide poisoning in pregnant women is a relatively rare condition. We report a 32-year-old woman in her 32nd week of pregnancy found unconscious in the bathroom. On arrival, her pulse and blood pressure were undetectable. Cardiopulmonary resuscitation was applied. The mother's carboxyhaemoglobin level was 57%. Due to foetal distress, Caesarean section was performed in the emergency department. The baby was intubated due to the absence of spontaneous respiration. The level of carboxyhaemoglobin in the cord blood was 32%. After staying in the newborn unit for 47 days, the baby was discharged with a sequela of cerebral palsy.

Carbon Monoxide Exposure During Pregnancy

IMPORTANCE

Carbon monoxide (CO) is the leading cause of poisoning in the United States and is associated with high maternal and fetal mortality rates. Given the nonspecific signs and symptoms of toxicity, cases may go unsuspected or attributed to other etiologies. As CO adversely affects both mother and fetus, it is important for practitioners to recognize and treat poisoning in a timely manner.

OBJECTIVE

We seek to assist practitioners with understanding the physiology and recognizing the presentations of both acute and chronic CO poisoning, as well as provide information on diagnosis and treatment options. We also conducted a review of cases described in the literature during the past half century to show varying presentations and treatment methodologies.

EVIDENCE ACQUISITION

A qualitative literature search was conducted using PubMed and Google Scholar for articles published between 1970 and 2014 that assessed cases of CO poisoning during pregnancy. Excluded studies were not in English or contained nonhuman subjects.

RESULTS

Nineteen published reports of CO poisoning during pregnancy described in varying levels of detail were found in the literature from 1971 to 2010.

CONCLUSIONS AND RELEVANCE

Carbon monoxide poisoning requires a high degree of suspicion. Diagnosis is made based on initial history and physical evaluation and assessment of environmental CO levels; presenting carboxyhemoglobin levels may be poor indicators of severity of disease. Oxygen therapy should be initiated promptly in all possible cases with consideration of hyperbaric oxygen therapy in cases of significant maternal exposure. Treatment requires a longer duration for fetal CO elimination than in the nonpregnant patients. Importantly, practitioners should educate pregnant patients on prevention.

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.

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.

Housing and child health

The connection between housing and health is well established. Physical, chemical, and biological aspects of the child's home, such as cleanliness, moisture, pests, noise, accessibility, injury risks, and other forms of housing environmental quality, all have the potential to influence multiple aspects of the health and development of children. Basic sanitation, reduced household crowding, other improvements in housing and expanded, and improved housing regulations have led to advances in children's health. For example, lead poisoning prevention policies have profoundly reduced childhood lead exposure in the United States. This and many other successes highlight the health benefits for families, particularly children, by targeting interventions that reduce or eliminate harmful exposures in the home. Additionally, parental mental health problems, food insecurity, domestic violence, and the presence of guns in children's homes all are largely experienced by children in their homes, which are not as yet considered part of the Healthy Homes agenda. There is a large movement and now a regulatory structure being put in place for healthy housing, which is becoming closely wedded with environmental health, public health, and the practice of pediatrics. The importance of homes in children's lives, history of healthy homes, asthma, and exposures to lead, carbon monoxide, secondhand/thirdhand smoke, radon, allergy triggers is discussed, as well as how changes in ambient temperature, increased humidity, poor ventilation, water quality, infectious diseases, housing structure, guns, electronic media, family structure, and domestic violence all affect children's health.

[Ten practical issues concerning acute poisoning with carbon monoxide in pregnant women]

BACKGROUND

The poisoning of carbon monoxide (CO) is the leading cause of death by poisoning in France. Its consequences are potentially serious to the fetus. Literature is ancient and little known.

PURPOSE AND METHOD

Make an inventory of knowledge about carbon monoxide poisoning during pregnancy.

RESULT

The CO causes maternal then fetal tissue hypoxia primarily by binding to hemoglobin with which it has a high affinity. Its transplacental passage may cause fetal harm, predominantly in the brain. Severity seems correlated with maternal symptoms during exposure. In the absence of maternal symptoms, however, the available data are reassuring. Hyperbaric oxygen therapy may reduce the risk to the fetus.

DISCUSSION

Oxygen therapy should be offered in all cases of CO poisoning, especially if there are maternal symptoms during exposure. In addition, a fetal echography directed on the cephalic pole - even a fetal magnetic resonance imaging three weeks after exposure - should also be proposed.

Carbon monoxide poisoning

Carbon monoxide (CO) poisoning is the leading cause of death as a result of unintentional poisoning in the United States. CO toxicity is the result of a combination of tissue hypoxia-ischemia secondary to carboxyhemoglobin formation and direct CO-mediated damage at a cellular level. Presenting symptoms are mostly nonspecific and depend on the duration of exposure and levels of CO. Diagnosis is made by prompt measurement of carboxyhemoglobin levels. Treatment consists of the patient's removal from the source of exposure and the immediate administration of 100% supplemental oxygen in addition to aggressive supportive measures. The use of hyperbaric oxygen is controversial.

Clinical policy: critical issues in the management of adult patients presenting to the emergency department with acute carbon monoxide poisoning

This clinical policy focuses on critical issues concerning the management of adult patients presenting to the emergency department (ED) with acute symptomatic carbon monoxide (CO) poisoning. The subcommittee reviewed the medical literature relevant to the questions posed. The critical questions are: Should hyperbaric oxygen (HBO(2)) therapy be used for the treatment of patients with acute CO poisoning; and Can clinical or laboratory criteria identify CO-poisoned patients who are most or least likely to benefit from this therapy? Recommendations are provided on the basis of the strength of evidence of the literature. Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies that are based on preliminary, inconclusive, or conflicting evidence, or based on committee consensus. This clinical policy is intended for physicians working in hospital-based EDs.

Hyperbaric oxygen and carbon monoxide poisoning: a critical review

CO is likely to be the most common cause of poisoning worldwide and often results in persistent neuropathologic and cognitive sequelae. While the displacement of oxygen from hemoglobin by CO has overshadowed the myriad mechanisms by which CO causes injury, mere oxygen displacement has endured as the etiology of CO poisonings and perpetuated a cascade of misdiagnosis, misunderstandings and confusion regarding how and when to treat CO poisoning. Hyperbaric oxygen benefits the brain more than normobaric oxygen by, e.g. improving energy metabolism, preventing lipid peroxidation and decreasing neutrophil adherence. Randomized controlled trials have definitively shown hyperbaric oxygen as the only efficacious therapy for acute CO poisoning if delayed neurological sequelae are to be minimized. Normobaric oxygen should not be used between multiple hyperbaric oxygen treatments as this can contribute to toxicity. Hyperbaric oxygen seems to also have potential in the delayed treatment of CO poisoning using multiple treatments of low dose of oxygen; however, oxygen dosing issues are not yet fully understood for either acute or delayed treatment. It would behoove medical decision-makers to embrace this important tool and make it more accessible as well as helping to disseminate to the medical community what is now known from the available literature.

Toxicity Associated with Carbon Monoxide

Carbon monoxide is an insidious poison that accounts for thousands of deaths each year in North America. Clinical effects maybe diverse and include headache, dizziness, nausea, vomiting,syn-cope, seizures, coma, dysrhythmias, and cardiac ischemia. Children, pregnant women, and patients who have underlying cardiovascular disease are particularly at risk for adverse out-comes. Treatment consists of oxygen therapy, supportive care, and, in selected cases, hyperbaric oxygen therapy.

Carbon monoxide poisoning

CO is an ubiquitous poison with many sources of exposure. CO poisoning produces diverse signs and symptoms that are often subtle and may be easily misdiagnosed. Failure to diagnose CO poisoning may result insignificant morbidity and mortality and permit continued exposure to a dangerous environment. Treatment of CO poisoning begins with inhalation of supplemental oxygen and aggressive supportive care. HBOT accelerates dissociation of CO from hemoglobin and may also prevent DNS. Absolute indications forHBOT for CO poisoning remain controversial, although most authors would agree that HBOT is indicated in patients who are comatose or neurologically abnormal, have a history of LOC with their exposure, or have cardiac dysfunction. Pregnancy with an elevated CO-Hgb level(>15%-20%) is also widely, considered an indication for treatment.HBOT may be considered in patients who have persistent symptoms despite NBO, metabolic acidosis, abnormalities on neuropsychometric testing, or significantly elevated levels. The ideal regimen of oxygen therapy has yet to be determined, and significant controversy exists regarding HBOTtreatment protocols. Often the local medical toxicologist, poison control center, or hyperbaric unit may assist the treating physician with decisions regarding therapy.

Carbon monoxide poisoning in a parturient and the use of hyperbaric oxygen for treatment

We report a case of carbon monoxide (CO) intoxication in a pregnant woman who presented with acute non-specific symptoms and fetal distress. She was scheduled for urgent caesarean section but this was averted after consultation, advice and discussion from a National Poisons Centre, obstetricians and physicians managing the local hyperbaric oxygen facility. Hyperbaric oxygen (HBO) was used successfully to treat both the woman and her fetus. This resulted in a normal reactive fetal cardiotochograph (CTG) trace after treatment and the fetus was delivered 6 weeks later by normal vaginal delivery. The effects of CO intoxication and the use of HBO on the pregnant woman and her fetus are discussed.

Carbon monoxide poisoning

CO is an insidious poison with many sources of exposure. CO poisoning produces diverse signs and symptoms, which often are subtle and can be misdiagnosed easily. Failure to diagnose CO poisoning may result insignificant morbidity and mortality and allow continued exposure to a dangerous environment. In the ED, a high index of suspicion must be maintained for occult CO exposure. Headache, particularly when associated with certain environments, and flulike illness in the wintertime with symptomatic cohabitants should raise the index of suspicion in the ED significantly for occult CO poisoning. Emergency treatment of CO poisoning begins with inhalation of supplemental oxygen and aggressive supportive care. HBOT accelerates dissociation of CO from hemoglobin and may prevent DNS. Absolute indications for HBOT for CO poisoning remain controversial, although most would agree that HBOT is indicated in patients who are comatose, are neurologically abnormal, have a history of loss of consciousness with their exposure, or have cardiac dysfunction. Pregnancy with an elevated CO-Hgb level (>15-20%) also is widely considered an indication for treatment. HBOT may be considered in patients who have persistent symptoms despite NBO, metabolic acidosis, abnormalities on neuropsychometric testing, or significantly elevated levels. The ideal regimen of oxygen therapy has yet to be determined, and significant controversy exists regarding HBOT protocols. The emergency physician may be confronted with the difficult decision regarding disposition and even transfer to a hyperbaric facility. Often the local medical toxicologist, poison control center, or hyperbaric unit can assist the emergency physician with the decision-making process.

Carbon monoxide poisoning. Early awareness and intervention can save lives

Each year, particularly during the heating season, thousands of people are poisoned by carbon monoxide, with potentially devastating outcomes. Initial diagnosis can be difficult because symptoms closely resemble those of influenza and are often misinterpreted. Dr Tomaszewski discusses diagnosis and treatment, including the benefits and risks of hyperbaric oxygen therapy.

Hyperbaric oxygen therapy in the pediatric patient: the experience of the Israel Naval Medical Institute

The pediatric patient is to be found in hyperbaric facilities throughout the world, receiving hyperbaric oxygen (HBO) therapy for both life-threatening and chronic diseases.

OBJECTIVE

To review the experience accumulated at the Israel Naval Medical Institute in the treatment of pediatric patients.

DESIGN

A retrospective analysis and review of all records of patients younger than age 18 years.

RESULTS

Between 1980 and 1997, 139 pediatric patients age 2 months to 18 years (mean, 7.7 years) received HBO treatment at the Israel Naval Medical Institute. Of the children, 111 (79%) suffered from acute carbon monoxide (CO) poisoning; 13 (9.2%) were treated after crush injury, traumatic ischemia, or compartment syndrome; 4 (2.8%) had clostridial myonecrosis; 1 (0.7%) had necrotizing fasciitis; 5 (3.6%) had refractory osteomyelitis; 2 (1.4%) had suffered massive air embolism; 2 (1.4%) had purpura fulminans; and 1 (0.7%) suffered from decompression sickness. Outcome, judged by neurologic sequelae, mortality, and extent of soft tissue loss and limb amputation, was favorable in 129 patients (93%). Two patients (1.4%) died, 1 as a result of CO poisoning and the other, gas gangrene; 2 of the patients in the CO group (1.4%) remained with neurologic sequelae, and 6 patients in the acute traumatic ischemia group (4.3%) underwent limb amputation.

CONCLUSIONS

We had a favorable experience with 129 of a total 139 pediatric patients treated at our facility for the indications listed. A basic knowledge of HBO therapy is needed to refer the pediatric patient for treatment when indicated. The needs of the pediatric patient, especially the critically ill, require specific skills and equipment inside the hyperbaric chamber. Close collaboration between the pediatrician and the hyperbaric medicine physician is essential to ensure adequate care for infants and children.

Carbon monoxide poisoning: easy to treat but difficult to recognise

Carbon monoxide (CO) poisoning is a common medical emergency and a frequent cause of deliberate or accidental death. It can cause acute and chronic central nervous system damage which may be minimised by prompt treatment with 100% oxygen or hyperbaric oxygen therapy. However, recognition of this intoxication can be difficult. Failure to diagnose it may have disastrous effects on the patient, and other members of the household who could subsequently become intoxicated. Guidance on the correct diagnosis of this condition is provided in the light of a number of studies screening emergency room populations. Guidelines for treatment with hyperbaric oxygen therapy are also reviewed.

Diving and pregnancy

Scuba diving during pregnancy has increased in incidence as a result of substantial growth in the number of young females attracted to sport diving. This review summarizes the physiological changes induced by immersion, diving and decompression, on male and female divers. Furthermore, it extends to literature review, in animal models, of the susceptibility of a pregnant animal to diving decompression injury. Publications regarding reports of diving injury in pregnant humans are also reviewed, comprising very recent material from the sport diving community. It is concluded that there is no countraindication to diving for the normal, healthy, nonpregnant female. However, pregnant females should refrain from diving, because the fetus is not protected from decompression problems and is at risk of malformation and gas embolism after decompression disease. It is prudent to advise pregnant patients of the increased risk of diving problems for the fetus during pregnancy. However, should a woman have completed a dive during early pregnancy because she was unaware she was pregnant, the present evidence is not to recommend an abortion, because several normal pregnancies have been documented even if diving is continued. Snorkeling can still be practiced during pregnancy, but scuba diving should be discontinued until after the birth period.

Carbon monoxide intoxication during pregnancy: a case presentation and pathophysiologic discussion, with emphasis on molecular mechanisms

In carbon monoxide (CO) poisoning, the mortality and morbidity risk does not always correlate with the level of carboxyhemoglobin (COHb). Recent studies confirm that the mitochondrial cytochrome portion of the respiratory chain is susceptible to CO toxicity at concentrations traditionally considered nontoxic. These laboratory findings correlate with subtle neurologic symptoms detected by psychometric studies in individuals many days from the time of acute intoxication. Additionally, in the pregnant patient, a time lag for both uptake and elimination of CO between the mother and fetus has been demonstrated, with the fetus at risk for hypoxia even when the mother's blood level of CO is nontoxic. Hyperbaric oxygen (HBO) therapy in pregnant patients has not been shown to have adverse effects on the fetus. We present a case of CO intoxication in late pregnancy treated with HBO therapy without adverse consequences.

Carbon monoxide controversies: neuropsychologic testing, mechanism of toxicity, and hyperbaric oxygen

Recent animal and clinical data require a reevaluation of the traditional approach to the patient exposed to carbon monoxide. Unfortunately, these new data are inconclusive and generate controversies regarding the indications and value of neuropsychologic testing, cause of carbon monoxide toxicity, and indications (if any) for hyperbaric oxygen therapy. These controversies and their implications for the emergency physician are discussed.

Pathophysiology and treatment of carbon monoxide poisoning

Carbon monoxide poisoning is the leading cause of poisoning deaths in the US, and published reports of carbon monoxide related morbidity and mortality can vary widely. Common morbidity involves myocardial and/or neurologic injury including delayed neurologic sequelae. The pathophysiology of this entity is complex, involving hypoxic stress on the basis of interference with oxygen transport to the cells and possibly impairing electron transport. Carbon monoxide can also affect leukocytes, platelets and the endothelium, inducing a cascade of effects resulting in oxidative injury. Carboxyhemoglobin levels are valuable for confirming carbon monoxide exposure but cannot be used to stratify severity of poisoning, predict prognosis, or indicate a specific treatment plan. Oxygen therapy is the key treatment of carbon monoxide intoxication, and hyperbaric oxygen has been shown to interdict and improve clinical outcome in some patients. Immediate treatment with a high fraction of inspired oxygen and careful clinical evaluation are mandatory. Timely referral for hyperbaric oxygen is indicated for patients with any history of unconsciousness, cardiovascular instability or ischemia, and persistent mental and/or neurologic deficits. Hyperbaric oxygen should also be considered in certain other patient subsets.