Relationship between arterial, mixed venous, and internal jugular carboxyhemoglobin concentrations at low, medium, and high concentrations in a piglet model of carbon monoxide toxicity.

OBJECTIVE: This study tested the hypothesis that mixed venous carboxyhemoglobin concentrations (V-COHb) and internal jugular carboxyhemoglobin concentrations (I-COHb) accurately predict arterial carboxyhemoglobin concentrations (A-COHb). In addition, this study tested the hypothesis that there is a high correlation at low (COHb, 0% to 10%), moderate (COHb, >10% to 40%), and high (COHb, >40%) concentrations between V-COHb, I-COHb, and A-COHb. DESIGN: The study was a prospective comparison of A-COHb, V-COHb, and I-COHb concentrations in piglets exposed to increasing concentrations of carbon monoxide over 6 hrs to achieve a concentration of > or =60% COHb. Carboxyhemoglobin measurements were evaluated by analysis of variance and correlation analysis. Agreement between V-COHb and A-COHb concentrations was examined by using a plot of arteriovenous differences against the mean of the two measurements. INTERVENTION: We simultaneously sampled arterial, mixed venous, and internal jugular blood every 30 mins over the 6-hr study period. RESULTS: Two hundred fifty arterial and mixed venous COHb concentrations were obtained, and 214 internal jugular COHb concentrations were obtained. One hundred additional arterial, mixed venous, internal jugular, and peripheral COHb concentrations were obtained. Correlation between samples at each concentration revealed r2 > = .94. CONCLUSION: Venous COHb concentrations predict arterial COHb concentrations with a high degree of accuracy and are correlated at low, moderate, and high concentrations of carbon monoxide exposure. Arterial or venous samples can be used to accurately measure COHb concentrations.

Effects of dantrolene on cooling times and cardiovascular parameters in an immature porcine model of heatstroke.

OBJECTIVE: To evaluate the effects of dantrolene on cooling times and cardiovascular parameters in an immature porcine model of heatstroke. DESIGN: Prospective, randomized, controlled, multigroup study. SETTING: Research animal laboratory. SUBJECTS: Yorkshire piglets (n = 16), 4 to 5 wks of age, 3.5 to 4.5 kg of body weight. INTERVENTIONS: Animals were slowly heated with a radiant heat source to 43 degrees C and then maintained at this temperature for 30 mins. The animals were then removed from the heat source and randomized into one of four groups to receive either conventional cooling methods consisting of fluid resuscitation with 0.9% sodium chloride solution, sponging with room temperature water, mechanical fanning, and gastric lavage with iced 0.9% sodium chloride solution (group 1), conventional cooling methods and dantrolene (group 2), conventional cooling methods and dantrolene's vehicle mannitol (group 3), or no treatment (group 4). Cooling times, defined as the time required to reach a core body temperature of 38.5 degrees C, and cardiovascular parameters for each group were then compared. MEASUREMENTS AND MAIN RESULTS: Animals in groups 1, 2, and 3 had significantly (p < .05) lower core body temperatures than animals that received no treatment at the conclusion of the experiment. Piglets in groups 2 and 3 had faster cooling times than piglets in group 1 (p < .05). However, there was no statistically significant difference in cooling times between the animals in groups 2 and 3. There were no statistically significant differences in heart rate, mean arterial pressure, central venous pressure, pulmonary artery occlusion pressure, or systemic vascular resistance index between animals in groups 1, 2, or 3. Group 3 piglets had higher cardiac indices and stroke indices than the piglets in the other groups (p < .05). CONCLUSIONS: Therapeutic interventions with conventional cooling or conventional cooling and dantrolene provided significant improvement in cardiovascular function in an immature porcine heatstroke model. Dantrolene, given with conventional cooling methods, offered no significant improvement in cardiovascular parameters compared with conventional cooling methods alone. Dantrolene significantly shortened the cooling time compared with conventional cooling but did not significantly shorten the cooling time compared with its vehicle, mannitol. Although dantrolene significantly shortened the cooling time, it did not appear to be superior compared with conventional cooling methods in treating heatstroke in this immature porcine heatstroke model.

Pulmonary complications following tricyclic antidepressant overdose in an adolescent.

OBJECTIVE: To report a case of pulmonary edema following a tricyclic antidepressant (TCA) overdose in an adolescent. CASE SUMMARY: A 14-year-old girl with a history of prior suicide attempts ingested 54 50-mg desipramine hydrochloride tablets (45 mg/kg ingestion). The patient developed a cardiac dysrhythmia and hypotension, which were successfully treated. She subsequently developed pulmonary edema and a clinical picture suggestive of adult respiratory distress syndrome (ARDS). She was successfully managed with fluid restriction, tracheal intubation, application of positive end-expiratory pressure (PEEP), and vasopressors. The patient was discharged without any clinical sequelae. DISCUSSION: Pulmonary complications secondary to TCA overdose have rarely been reported in children. We reviewed literature pertaining to the etiology, epidemiology, pathophysiology, and management of TCA-induced lung injury, as well as other case reports. We discuss the potential relationship between sequelae resulting from TCA ingestion (e.g., cardiac disturbances, hypotension, acidosis, gastric aspiration, pneumonia) and the development of ARDS and pulmonary edema, and relate this association to our patient. CONCLUSIONS: Pulmonary edema and a clinical picture suggestive of ARDS was noted in an adolescent girl who ingested a large quantity of desipramine. Her lung injury may have been the result of a variety of factors including hypotension, metabolic acidosis, possible aspiration, or a direct action on the lung parenchyma by desipramine. We attribute her favorable clinical outcome to early intervention consisting of tracheal intubation, PEEP, fluid restriction, and vasopressor therapy.

Plastic bronchitis: an unusual cause of respiratory distress in children.

This case illustrates an unusual cause of respiratory distress in the pediatric population. A high degree of suspicion is necessary to make the diagnosis of plastic bronchitis. Wheezing and cough will lead to the diagnosis of reactive airway disease and/or foreign body aspiration. Chest radiographs may yield additional information, but the diagnosis is made by bronchoscopy and removal of the casts. Any child with severe respiratory distress refractory to aggressive conventional medical therapy and with a history or radiograph suggestive of plastic bronchitis should be considered a candidate for bronchoscopy. As clinicians, we must always remember the dictum, "All that wheezes is not asthma."