These values are total concentrations, both bound and free lidocaine, and give no information about free fraction, which we did not investigate. The major plasma protein which binds lidocaine and several other basic drugs, alpha!-acid glycoprotein is an acute-phase protein that is elevated in certain situations such as stress, neoplastic disease, acute and chronic inflammatory diseases, hepatic damage, and trauma. The free fraction of lidocaine in plasma is inversely related to plasma AAG concentrations. This patients adenocarcinoma and trauma associated with chest tube insertion might have elevated his AAG concentrations and decreased the free fraction of lidocaine. That physiologic change might explain the absence of signs or symptoms of lidocaine toxicity. …Read the rest of this article
This case is remarkable in that lidocaine solution and jelly applied to the oropharynx and bronchial tree were rapidly and extensively absorbed attaining a peak plasma concentration of 7.1 μg/ml within 0.67 hour of the start of drug administration (Fig 1). Furthermore, for four hours after the procedure, the plasma levels remained greater than 1.5 μg/ ml, which is within the antiarrhythmic “therapeutic” range of 1.5 to 5.5 μml. These plasma concentrations are greater than most literature reports of 1 to 4 μg/ml during bronchoscopy and higher than what we observed in a study of 19 bronchoscopy patients receiving a total average lidocaine dosage of 1,240 mg administered in a regimen similar to the regimen described here. In that study, the average peak plasma concentration was 2.6 ± 1.0 μg/ml. …Read the rest of this article
Systemic absorption of lidocaine following its topical application during diagnostic procedures can produce central nervous system or cardiac toxicity. Objective signs of toxicity are more likely at plasma concentrations above 6 μml, which are only rarely reported during bronchoscopy. It is useful, therefore, to identify patient populations at risk for developing these undesired effects due to high plasma concentrations.
A 55-year-old white man weighing 65 kg was admitted with the chief complaint of increasing shortness of breath, chest pain, and an 18 kg weight loss over the prior eight months. He had an 80 pack-year smoking history. The admission chest x-ray film was suggestive of a right-sided empyema and a thoracentesis was performed. Pleural fluid was cultured and grew out Streptococcus pneumoniae, for which benzylpenicillin, 2 million units IV q 4 h was given. A chest tube was placed in the right chest for drainage. The patient was also noted to have candidiasis in the oral cavity for which topical nystatin suspension was prescribed, lo rule out the possibility of a neoplasm causing a postobstructive pneumonia, bronchoscopy was conducted. On the prior day, remarkable serum chemistry values were a slightly elevated alkaline phosphatase of 163 U/L (normal range: 50 to 145 U/L) and low serum protein, with 4.7 g/dL total protein (6.5 to 8.4 g/dL), 2.0 albumin (3.5 to 5.0 g/ dL), and 2.7 globulin (3.2 to 4.8 g/dL). Other liver function tests were normal. …Read the rest of this article