[A study of the clinical features and the effect of therapy on acute respiratory distress syndrome patients as a result of severe triphosgene poisoning]

OBJECTIVE

To investigate the clinical features and treatment strategy for acute respiratory distress syndrome (ARDS) caused by phosgene.

METHODS

Individualized therapy was carried out in 17 cases of severe phosgene poison patients. Blood routine, electrolytes, blood gas analysis, hepatic and renal function tests and cardiac enzymes were examined before and after treatment.

RESULTS

Vital signs, fluid, electrolytes and acid-base disturbances were improved after treatment. As compared to that of pre-treatment period, white blood cells [WBC, ×10(9)/L: 12.18 ± 4.76 vs. 21.93 ± 6.21], neutrophil percentage (0.87 ± 0.05 vs. 0.92 ± 0.03), hemoglobin (Hb, g/L: 128.12 ± 25.65 vs. 173.71 ± 23.53), blood platelet count [PLT,×10(9)/L:165.12 ± 31.70 vs. 254.47 ± 70.80], alanine transaminase (ALT, U/L: 70.71 ± 46.70 vs. 212.71 ± 141.34), aspartate aminotransferase (AST, U/L: 52.47 ± 34.68 vs. 82.41 ± 34.60), blood urea nitrogen (BUN, mmol/L: 5.83 ± 4.09 vs. 7.89 ± 5.96), serum creatinine (SCr, μmol/L: 48.13 ± 14.97 vs. 67.25 ± 24.29), lactate dehydrogenase (LDH, U/L: 280.10 ± 81.77 vs. 586.35 ± 186.71), creatine kinase (CK, U/L: 199.12 ± 106.75 vs. 683.00 ± 323.21), MB isoenzyme of creatine kinase (CK-MB, U/L: 26.94 ± 9.13 vs. 45.59 ± 11.21), serum chlorine anion [Cl(-), mmol/L: 95.88 ± 6.06 vs. 102.29 ± 7.28], respiratory rate (RR, beats/min: 20.88 ± 4.30 vs. 30.06 ± 5.78), heart rate (HR, beats/min: 82.76 ± 17.16 vs. 113.35 ± 16.90), blood pH value (7.34 ± 0.44 vs. 7.39 ± 0.03) were all decreased (P < 0.05 or P < 0.01). Serum sodium ion [Na(+),mmol/L:140.61 ± 6.69 vs. 134.06 ± 4.80], arterial partial pressure of oxygen [PO(2), mm Hg, 1 mm Hg = 0.133 kPa: 84.41 ± 30.58 vs. 59.88 ± 15.19] and pulse oxygen saturation [SpO(2): 0.91 ± 0.08 vs. 0.78 ± 0.15] were increased (P < 0.05 or P < 0.01). Sixteen patients totally recovered, 1 patient died, and the cure rate was 94.12%.

CONCLUSIONS

Respiratory system could be mainly injured as the result of exposure to phosgene and leading to ARDS. Early initial combination therapies with corticosteroids and respiratory support should be addressed.

[Phosgene poisoning: analysis of cases]

On April 9, 1998, there was a break-down in the Chemical Plant ZACHEM S.A. in Bydgoszcz, which resulted in two cases of lethal phosgene poisoning. Over ten years have passed since that accident. During that period there were new cases of exposure to phosgene, however, all of the victims recovered completely. The aim of this paper was to present stages and symptoms of phosgene poisoning and discuss the undertaken procedures, which led to the recovery of people exposed to toxic effect of phosgene.

[Observation on the protective effect of hyperoxia solution on the acute lung injury caused by phosgene poisoning.]

OBJECTIVE

To study the protective effect of hyperoxia solution on acute lung injury caused by phosgene poisoning by observing the changes of PaO2 and malondialdehyde (MDA) contents, superoxide dismutase (SOD) activity in serum and Glutathione (GSH/GSSG) contents in lung tissues.

METHODS

The rabbits were divided into normal control group, hyperoxia solution (H0) and balance salt (BS) groups. Group HO and Group BS inhaled phosgene and the former was given intravenously hyperoxia solution (which was replaced by balance salt solution in Group BS). The content of MDA and the activity of SOD in serum were observed at different time points, the amount of GSH and GSSG in lung tissue were also measured.

RESULTS

(1) The serum MDA contents increased and PaO2, SOD activity decreased significantly in Group HO and Group BS along with time increasing as compared with control group. The contents of GSH in lung tissue decreased in two groups compared with that in control group, however the contents of GSSG ascended instead. (2) At 3 and 8 h of the experiment, PaO2 of Group HO [(9.91 +/- 0.49), (9.15 +/- 0.46) mm Hg respectively] were significantly higher than those of Group BS [(9.03 +/- 0.76), (8.11 +/- 0.57) mm Hg respectively] (P < 0.01). The contents of MDA of Group HO (3.66 +/- 0.35), (5.31 +/- 0.15) micromol/L respectively] were lower than those of Group BS [(4.32 +/- 0.26), (7.4 +/- 0.33) micromol/L respectively] (P < 0.01). SOD activity in Group HO [(237.37 +/- 29.96), (208.10 +/- 18.80) NU/ml respectively] were higher than those of Group BS [(195.02 +/- 21.44), (144.87 +/- 21.26) NU/ml respectively] (P < 0.05 or P < 0.01). The content of GSSG lung tissue in Group HO (423.67 +/- 38.21) micromol/L were lower than those of Group BS (523.85 +/- 43.14) mol/L (P < 0.01). There were no significant differences in the content of GSH in lung tissues between Group HO and group BS.

CONCLUSION

Hyperoxia solution can reduce acute lung injury of rabbits following phosgene poisoning.

[Effect of acute phosgene inhalation on antioxidant enzymes, nitric oxide and nitric-oxide synthase in rats]

OBJECTIVE

To study the effect of acute phosgene inhalation on the antioxidant enzymes, nitric oxide (NO) and nitric oxide synthase (NOS) in rats.

METHODS

Phosgene was produced by decomposing bis (trichdomethyl) carbonate in the presence of N,N-dimethyl formamide. SD rats were randomly divided into two groups: control and phosgene exposure groups. In a special experimental device with equipment modulating the gas flow, phosgene exposed rats inhaled phosgene quantitatively for five minutes. Two hours later, all the rats were sacrificed and the ratio of wet weight to dried weight of lung (WW/DW) was calculated. Peripheral blood, serum and liver were collected to examine the activities of antioxidant enzymes including glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), NOS, and NO level. The total content of proteins were also determined.

RESULTS

The WW/DW ratio of lung in phosgene exposure group was much higher than that in control group (P < 0.01). The activities of GST in serum and liver of phosgene exposure group increased significantly (P < 0.05). The activities of SOD, CAT, GSHPx and NOS in serum or blood and liver of phosgene exposure group were also increased significantly (P < 0.05). But the content of NO was significantly decreased (P < 0.01).

CONCLUSION

Acute phosgene inhalation may cause a dramatically changes of several antioxidant enzyme activities, and acute injury of liver to some extent in rats. The latter is related to reactive oxygen species. But the elevation of antioxidant enzyme activities suggests that antioxidative treatment for acute phosgene poisoning should not be considered first.

Chemical and biological weapons. Implications for anaesthesia and intensive care

In the wake of recent atrocities there has been renewed apprehension regarding the possibility of chemical and biological weapon (CBW) deployment by terrorists. Despite various international agreements that proscribe their use, certain states continue to develop chemical and biological weapons of mass destruction. Of greater concern, recent historical examples support the prospect that state-independent organizations have the capability to produce such weapons. Indeed, the deliberate deployment of anthrax has claimed several lives in the USA since September 11, 2001. In the event of a significant CBW attack, medical services would be stretched. However, victim survival may be improved by the prompt, coordinated response of military and civil authorities, in conjunction with appropriate medical care. In comparison with most other specialties, anaesthetists have the professional academic background in physiology and pharmacology to be able to understand the nature of the injuries caused by CBWs. Anaesthetists, therefore, play a vital role both in the initial resuscitation of casualties and in their continued treatment in an intensive care setting. This article assesses the current risk of CBW deployment by terrorists, considers factors which would affect the severity of an attack, and discusses the pathophysiology of those CBWs most likely to be used. The specific roles of the anaesthetist and intensivist in treatment are highlighted.

Phosgene exposure: mechanisms of injury and treatment strategies

Phosgene (carbonyl chloride, CAS 75-44-5) is a highly reactive gas of historical interest and current industrial importance. Phosgene has also proved to be a useful model for the study of those biochemical mechanisms that lead to permeability-type pulmonary edema (adult respiratory distress syndrome). In turn, the study of phosgene-induced adult respiratory distress syndrome has provided insights leading to revised treatment strategies for exposure victims. We summarized recent findings on the mechanisms of phosgene-induced pulmonary edema and their implications for victim management. In light of that research, we also provide a comprehensive approach to the management and treatment of phosgene exposure victims.

Possible immediate and long-term health effects following exposure to chemical warfare agents

Agents of chemical warfare continue to pose a threat to human life. Organophosphorus compounds are possibly the best known and most used agents in recent times. These are known to produce acute ill health and death and, probably equally important, many diverse delayed effects, many of which are not clinically nor pathologically well defined. The immediate and delayed effects of organophosphorus compounds, in particular, and those of other known agents of chemical warfare, such as mustard gas, Lewisite, phosgene, cyanides and the newer crowd control agents, are reviewed. Environmental sequelae of these agents are gaining importance as probable causes of chronic ill health amongst those living in regions where these agents have been used. The need to study the pattern of disease in exposed populations is emphasised.

Post-exposure treatment with isoproterenol attenuates pulmonary edema in phosgene-exposed rabbits

This study investigated the post-treatment effect of isoproterenol (ISO) on pulmonary parameters in rabbits whole-body-exposed to a lethal dose of the toxic gas phosgene. Phosgene is widely used in industry as a chemical intermediate for the production of plastics, drugs and polyurethane products. The results of this study are from five study groups: 10-min perfused baseline; uninjured controls exposed to air; phosgene-exposed; phosgene-exposed isoproterenol-treated intravascularly and intratracheally (ISO i.v.+i.t.); and phosgene-exposed isoproterenol-treated intratracheally (ISO i.t.). Treatment with ISO was administered as either a continuous intravascular infusion (24 microg min(-1)) from the beginning to end of perfusion (i.v.) and a 24-microg intratracheal bolus (i.t.) or just an i.t. bolus immediately prior to the start of perfusion. Rabbits of 2.5-3 kg were exposed to a cumulative dose of phosgene to attain a concentration x time exposure-effect of 1500 ppm x min. Lungs were isolated in situ and perfused 50-60 min after the start of exposure with Krebs-Henseleit buffer at 40 ml min(-1). Pulmonary artery pressure (Ppa), tracheal pressure (Pt) and lung weight gain (lwg) were continuously measured. Leukotrienes (LT) C4/D4/E4 were measured in the perfusate every 20 min during perfusion. At the immediate conclusion of the experiment, lung tissue was frozen in liquid N2 and analyzed for glutathione (GSH) and cyclic 3',5'-adenosine monophosphate (cAMP). Post-treatment with ISO by either i.v.+i.t. or i.t. routes 50+ min after phosgene exposure significantly lowered Ppa, Pt and lwg. Phosgene-exposed rabbits post-treated with ISO i.t. had significantly higher levels of reduced GSH (3 +/- 0.4 nmol mg(-1) protein), GSH/GSSG ratios (3.3 +/- 0.6 nmol mg(-1) protein) and percentage of total as reduced GSH (75 +/- 2.5%) compared with phosgene-exposed rabbits: 1.9 +/- 0.3, 2 +/- 0.3 and 58 +/- 6.3%, respectively. The ISO (i.v.+i.t.) post-treatment route significantly increased reduced GSH (6.2 +/- 1.7 nmol mg(-1) protein), GSH/GSSG ratio (5.9 +/- 0.8 nmol mg(-1) protein) and percentage of total as reduced GSH (85 +/- 1.7%) when compared to the phosgene-only group. The ISO i.t. and ISO i.v.+i.t. treatments significantly reduced perfusate LTC4/D4/E4 150 min after the start of exposure by 90% and 48%, respectively. These data suggest that protective mechanisms for ISO involve reduced vascular pressure, decreased LTC4/D4/E4-mediated pulmonary capillary permeability and a favorable lung tissue redox state compared with untreated phosgene-exposed rabbits.

Occupational phosgene poisoning: a case report and review

Phosgene is a highly toxic gas to which some workers may be occupationally exposed. This case report demonstrates the possibility of refrigeration workers suffering phosgene poisoning after heating certain chlorinated fluorocarbons ('freons'). The need to suspect phosgene exposure and observe such patients is emphasized, especially in view of the delay in clinical deterioration observed in some patients who subsequently develop adult respiratory distress syndrome.

Protective effects of N-acetylcysteine treatment after phosgene exposure in rabbits

We examined the effects of treatment with N-acetylcysteine (NAC) on pulmonary edema formation in isolated perfused rabbit lungs following in vivo phosgene exposure. This study focused on posttreatment intratracheal administration of NAC after exposure. Rabbits, 2 to 3 kg, were exposed to a cumulative dose of phosgene to attain a concentration x time exposure effect of 1,500 ppm/min. Lungs were perfused with Krebs-Henseleit buffer at 40 ml/min from 70 to 150 min after exposure. Pulmonary artery pressure (Ppa), tracheal pressure (Pt), and the rate of lung weight gain (LWG) were measured continuously. Perfusate concentration of peptide leukotrienes LTC4, D4, and E4 were measured every 20 min during perfusion. At the conclusion of the experiment, lung tissue was analyzed for reduced and oxidized glutathione (GSH and GSSG) and lipid peroxidation (thiobarbituric acid-reactive substances, TBARS). Exposure to phosgene significantly increased Pt, LWG, LTC4, D4, and E4, TBARS, and GSSG over time compared with controls. Compared with phosgene, intratracheal NAC lowered Ppa, LWG, LTC4, D4, and E4, TBARS, and GSSG. We conclude that NAC protected against phosgene-induced lung injury by acting as an antioxidant by maintaining protective levels of glutathione, reducing both lipid peroxidation and production of arachidonic acid metabolites.

[Clinical and radiological studies on 15 cases of acute phosgene poisoning]

A clinical and radiological observation on 15 cases of acute phosgene poisoning were reported. The pulmonary edema after acute phosgene poisoning can be classified into two types: interstitial and alveolar. The X-ray findings were described in detail in correlation with the clinical symptoms. Taking X-ray early can benefit on preventing and treating acute pulmonary edema. Meanwhile, the patients with chronic respiratory or digestive diseases can develop pulmonary encephalopathy or upper gastrointestinal bleeding after acute phosgene poisoning.

Pulmonary toxicity following exposure to methylene chloride and its combustion product, phosgene

Chemical paint removers containing methylene chloride are widely used in domestic and industrial settings where exposure to a heat source with conversion to phosgene is possible. We describe a case of noncardiogenic pulmonary edema and subsequent hyperreactive airways following such an exposure. In addition, the various problems that have been associated with exposure to methylene chloride and phosgene are reviewed.

Mechanism of phosgene-induced lung toxicity: role of arachidonate mediators

We have previously shown that phosgene markedly increases lung weight gain and pulmonary vascular permeability in rabbits. The current experiments were designed to determine whether cyclooxygenase- and lipoxygenase-derived mediators contribute to the phosgene induced lung injury. We exposed rabbits to phosgene (1,500 ppm/min), killed the animals 30 min later, and then perfused the lungs with a saline buffer for 90 min. Phosgene markedly increased lung weight gain, did not appear to increase the synthesis of cyclooxygenase metabolites, but increased 10-fold the synthesis of lipoxygenase products. Pre- or posttreatment with indomethacin decreased thromboxane and prostacyclin levels without affecting leukotriene synthesis and partially reduced the lung weight gain caused by phosgene. Methylprednisolone pretreatment completely blocked the increase in leukotriene synthesis and lung weight gain. Posttreatment with 5,8,11,14-eicosatetraynoic acid (ETYA), a nonmetabolized competitive inhibitor of arachidonic acid metabolism, or the leukotriene receptor blockers, FPL 55712 and LY 171883, also dramatically reduced the lung weight gain caused by phosgene. These results suggest that lipoxygenase products contribute to the phosgene-induced lung damage. Because phosgene exposure did not increase cyclooxygenase synthesis or pulmonary arterial pressure, we tested whether phosgene affects the lung's ability to generate or to react to thromboxane. Infusing arachidonic acid increased thromboxane synthesis to the same extent in phosgene-exposed lungs as in control lungs; however, phosgene exposure significantly reduced pulmonary vascular reactivity to thromboxane but not to angiotension II and KCl.

A literature review: therapy for phosgene poisoning

A literature search designed to collect information on therapy for phosgene poisoning has been conducted for the period 1920-1982. To achieve this goal, literature services were consulted, cross references were carefully followed and, whenever possible, unpublished reports (e.g., from Edgewood Arsenal and Porton Research Station) were evaluated. The various therapeutic agents and measures described in the literature are presented in alphabetical order. When available, detailed data are given for the phosgene dose, interval of time between exposure and institution of therapy, therapeutic effect and parameters used to assess efficacy. A final summary presents general recommendations for therapy and for further research.

Review of clinical experience in handling phosgene exposure cases

In summary, we have described our method of treating phosgene inhalation injury. We have presented two serious cases in detail which demonstrate that survival was associated with aggressive therapy. Several points should be mentioned. The pulmonary edema and resulting fluid and foam production can be so copious as to overwhelm efforts to place an endotracheal tube. The solution is early intubation by the nearest experienced person at the first hint of edema or pulmonary failure. Adequate support of the patient's blood volume is imperative to avert hypovolemic shock and renal failure. A balloon flotation catheter is desirable to monitor pulmonary wedge pressure and avoid overload. Follow-up pulmonary function studies and chest x-rays are recommended 2-3 months after hospital discharge. We have not yet found a reliable test to determine which cases will progress to pulmonary edema. The LDH appears to be the only consistently elevated sign in more serious cases. Finally, we would like to make a plea for the sharing of information from instances of fatal phosgene injury so that the facts can be studied and applied to future cases.

Mortality and causes of death among workers exposed to phosgene in 1943-45

Mortality and causes of death from death certificates were analyzed among workers exposed to phosgene while working at a uranium-processing plant in Tennessee in 1943-45. Standardized mortality ratios (SMRs) were calculated by using death rates for U.S. white males. As of 1979, SMRs for all causes and for various selected causes were similar in 694 male chemical workers chronically exposed to low levels of phosgene in 1943-45 and in 9280 male controls who worked at the same plant. SMRs for diseases of the respiratory system were 107 (14 observed vs. 13.07 expected) in the chemical workers and 119 (292 observed vs. 245.75 expected) in the controls. In a group of 106 males who were acutely exposed to high levels of phosgene, there were 41 deaths observed vs. 33.87 expected (SMR = 121; 95% confidence limits = 86 and 165). One death, occurring within 24 hours of exposure, was from pulmonary edema due to phosgene poisoning (coded to "accidental causes"). Five deaths were coded to diseases of the respiratory system (SMR = 266; 95% CL = 86 and 622); in 2 of these 5 deaths, "bronchitis" due to phosgene exposure had been reported in 1945. Among 91 female workers with acute high-level phosgene exposure, frequencies of symptoms and early health effects (pneumonitis and bronchitis) differed from those reported for the 106 male cases; preliminary data on vital status of these females are too incomplete for analysis, and further follow-up is needed.

Therapeutic strategy in phosgene poisoning

For the treatment of phosgene poisoning, glucocorticoids and positive pressure ventilation can be recommended as well as supporting measures such as physical rest, antitussives, buffers, sedatives, antibiotics, antispasmodics and possibly diuretics. Roentgenological evaluation of the lungs is advisable. A therapeutic strategy is presented which is based on the phosgene exposure intensity.

Late sequelae after phosgene poisoning: a literature review

The vast majority of phosgene intoxications (including cases with pulmonary edema) have a good prognosis. However, nearly all patients complain of exertional dyspnea and reduced physical fitness for several months to years after the accident; normalization of lung function values, too, may require several years. Occasional impairment of pulmonary function appears to be dependent more on smoking habits than on the severity of the original intoxication. Pre-existing chronic bronchitis may undergo severe and progressive deterioration after toxic pulmonary edema due to phosgene. Occupational health check-ups (including pulmonary function tests) are recommended for all persons handling irritant gases. Every patient having undergone the inhalation of phosgene or other irritants will ask the question of possible late sequelae. Due to new forms of treatment (glucocorticoids, positive pressure ventilation) the prognosis of severe cases has considerably improved during the last decades. The paper tries to summarize the present state of our knowledge.

Pathogenesis of phosgene poisoning

Phosgene inhalation in concentrations greater than 1 ppm may produce a transient bioprotective vagus reflex with rapid shallow breathing in some individuals. Phosgene concentrations greater than 3 ppm are moderately irritating to eyes and upper airways. Toxic phosgene doses (greater than or equal to 30 ppm X min) inhaled into the terminal respiratory passages render the blood-air-barrier more permeable to blood plasma, which gradually collects in the lung. Some time passes, however, until the collection of fluid provokes signs and symptoms. This period in which the patient experiences relative well-being is known as the clinical latent phase. The clinical symptoms which follow and the pathological changes underlying them are discussed in detail; dose-effect relationships are demonstrated. The regression phase after poisoning has been overcome is briefly sketched.

Early diagnosis of phosgene overexposure

At the present time, the following parameters can be recommended for "early diagnosis" of phosgene overexposure: Phosgene indicator paper badges, to be worn by all persons involved in handling phosgene (these badges permit immediate estimation of the exposure dose in each individual case); Observation of the initial irritative symptoms of the eye and the upper respiratory tract after phosgene inhalation can provide a rough indication of the inhalation concentration and dose; X-ray photographs of the lungs make it possible to detect incipient toxic pulmonary edema at an early stage, during the clinical latent period. A number of additional parameters require further critical investigation.

Phosgene: a practitioner's viewpoint

Clinical experience with five patients exposed to phosgene is described. The treatment of phosgene poisoning was focused upon the presenting problem, pulmonary edema. Arterial hypoxemia was treated with a face mask with 10 cm CPAP with the FiO2 adjusted as needed or with a volume ventilator with controlled ventilation. Ventilation was controlled to reduce the work of breathing. Metabolic acidosis was treated with NaCHO3 to produce a normal pH. A vigorous program of diuresis was used to treat the pulmonary edema. Lasix was administered to produce a negative fluid balance while maintaining a good urinary output. The negative fluid balance correlated well with reduced oxygen requirements.

[Phosgene poisoning]

Phosgene, a combat gaz of the first world war is now very used in industry. Authors report a few observations about acute intoxications in the manufacture of this gaz in Toulouse. They insist about the risks of slow coming out lung oedema when safety instructions are not correctly followed. However better knowledge and observance of these instructions permitted a reduction of these intoxications in number and gravity.

The methenamine misunderstanding in the therapy of phosgene poisoning

A thorough analysis of the pertinent literature leads to the conclusion that there is no justification for the use of methenamine (hexamethylene tetramin, Urotropin) for the therapy of phosgene poisoning.

[Radiological changes of the lungs induced by inhalation of irritating gases (author's transl)]

The radiological changes and clinical symptoms induced by in 109 persons by inhalation of irritant gases are described. Seven persons developed pulmonary oedema, abnormal radiological manifestations were observed in 19 while 81 persons there were no detectable radiological changes. Toxic pulmonary oedema is frequently detected earlier by roentgenologic means than clinically. The length of the radiological latent period depends not only on the concentration of the irritant but also on the type of the gaseous substance. The first roentgenologic signs of toxic pulmonary oedema are broadening and blurring of the outline of the hilar vessels. The pulmonary changes are characterized initially by disseminated small to medium sized shadows in the central portion and base of the lungs; later they tend to spread and merge.