Methaemoglobinemia after Liposuction under Tumescent Local Anaesthesia - Diagnostic Value of Pulse Oximetry.

Background: Tumescent local anaesthesia with prilocain can lead to clinically significant methemoglobin levels. New generation multiple wavelength pulse oximeters (e. g. Masimo Radical 7®) can measure methemoglobin levels. Methods: In this prospective observational study we compared the venous methemoglobin levels and the corresponding pulse oximetric values of the Radical 7® in patients undergoing tumescent local anaesthesia for liposuction procedures. The measurements were performed in Hanseklinik, Luebeck, Germany between 2008 and 2011. Results: In 133 patients, we measured a maximum methemoglobin level of 18 per cent. In a Bland-Altman analysis we found a mean bias of +2.2 % (-4.1 to 8.4 limits of agreement) for pulse oximetric values compared to hemoximetry. Conclusion: Pulse oximetric measurement of methemoglobin is an early-warning tool for the detection of clinically significant methaemoglobinemia in patients with tumescent local anaesthesia.

Evaluation and application of a high performance liquid chromatographic method for prilocaine analysis in human plasma.

BACKGROUND: Prilocaine, a local anesthetic of the amide type, is frequently applied in substantial doses during tumescent liposuction. Although it cannot be excluded that the subcutaneously infiltrated narcotic may enter the circulation and trigger adverse systemic reactions, prilocaine plasma levels have rarely been measured during routine tumescent surgery. We established and evaluated a high performance liquid chromatography (HPLC) method for analysis of this narcotic and used it to measure the drug in plasma samples drawn in the course of tumescent liposuction with prilocaine local anesthesia. METHODS: After approval by the local ethics committee and written informed consent, 283 heparin plasma samples were collected from 132 patients during and about 6, 12, and 24 hours after tumescent liposuction with prilocaine infused at doses of 19 +/- 5 mg/kg body weight. Calibrators and controls were prepared by spiking blank plasma with prilocaine. Following addition of internal standard and sodium hydroxide, plasma was extracted with diisopropyl ether. For HPLC analysis, dried extracts were dissolved in methanol - 4.35 mmol/L ammonium phosphate, pH7.0, (60:40 v/v) and applied to a Synergy 4 microm Fusion-RP column (250 x 4.6 mm) rinsed with the same buffer. Analytes were detected by absorption at 237 nm. For liquid chromatography mass spectrometry (LC-MS), extracts were dissolved in acetonitrile - 2 mmol/L ammonium acetate - formic acid (5:95:0.2 v/v/v), applied to a Synergy 4 microm Polar-RP column (75 x 2 mm), and eluted with a gradient of acetonitrile in 2 mmol/L ammonium acetate - formic acid. Analytes were detected by an ion trap mass spectrometer with electrospray ionization run in a MS/MS mode. RESULTS: In the HPLC assay established, prilocaine and the internal standard lidocaine eluted at about 14 and 25 minutes, respectively. The limit of detection of prilocaine was 0.002 mg/L, the measurable range extended to 30 mg/L. At prilocaine concentrations between 0.08 and 10.0 mg/L, inter-assay coefficients of variation of 6.2 to 9.9% were obtained. Analyses of plasma pools spiked with variable amounts of prilocaine showed recoveries of 91-101%. Results measured in 20 plasma samples by both HPLC and an independent LC-MS assay agreed acceptably (Y(HPLC) = 0.07 + 1.19x(LC-MS), R 0.98). Prilocaine plasma concentrations measured by HPLC in 132 plasma samples drawn in the late phase of liposuction ranged between 0.01 and 32.0 mg/L, roughly one third of all samples exhibiting levels above 5 mg/L. About 6 hours later, prilocaine levels measured in 46 plasma samples were lower (0.13 - 1.56 mg/L) and decreased further in the evening of the operative day (n = 49, 0.10 - 0.62 mg/L) and on the morning of the first postoperative day (n = 55, 0.03 - 0.25 mg/L). CONCLUSIONS: An HPLC method for determination of prilocaine was established and successfully applied to analysis of this drug in human plasma. Our results clearly indicate that during tumescent liposuction a significant portion of the subcutaneously infiltrated prilocaine enters the circulation, resulting in potentially harmful blood levels in about one third of the patients studied. 6 hours after liposuction, however, all samples exhibited prilocaine plasma levels far below a critical concentration and these levels further decreased in the evening of the day of treatment and on the next morning.

Pathological uterine perfusion in the second trimester is not associated with neutrophil activation.

OBJECTIVE: Preeclampsia and intrauterine growth retardation (IUGR) are associated with elevated concentrations of myeloperoxidase (MPO) and polymorphonuclear (PMN) elastase, which indicate maternal neutrophil activation. The aim of the study was to measure maternal MPO and PMN elastase plasma concentrations in second trimester pregnancies with pathological uterine perfusion that are a high risk group for preeclampsia and IUGR, and compare them to normal controls. METHODS: The study includes 25 pregnancies with normal and 25 pregnancies with pathological uterine perfusion. In both groups, doppler-sonographic measurement of uterine perfusion was performed in the twenty-first week of gestation. Maternal plasma concentrations of MPO and PMN elastase were measured using a specific ELISA for both enzymes. RESULTS: The plasma MPO concentration of pregnant women with normal perfusion did not differ significantly from that of the group with pathological perfusion (27.4 +/- 3.3 vs. 23.7 +/- 2.0 ng/mL). Likewise, the plasma PMN elastase-concentration also did not show a significant difference between the groups (5.7 +/- 0.5 ng/mL normal vs. 8.0 +/- 1.0 ng/mL pathological). Patients with pathological perfusion that later developed preeclampsia or IUGR (9/25) showed unchanged MPO and PMN elastase values in the second trimenon compared to those with pathological perfusion and normal outcome. CONCLUSIONS: Pathological uterine perfusion in the second trimester was not associated with maternal neutrophil activation. The measurement of the MPO and PMN elastase concentration suggested that neutrophil activation in preeclampsia or IUGR is a secondary effect of the disease rather than a primary pathophysiological factor.