A prospective study was conducted on 34 stable septic patients to determine whether mild hyperlactatemia is a marker of lactate overproduction or an indicator of lactate underutilization during sepsis. Plasma lactate clearance and lactate production were evaluated by modeling the lactate kinetic induced by an infusion of 1 mmol/kg L-lactate over 15 min. The patients were divided in two groups depending on their blood lactate: < or = 1.5 mmol/L (n = 20, lactate = 1.2+/-0.2 mmol/L) or > or = 2 mmol/L (n = 10, lactate = 2.6+/-0.6 mmol/L). The hyperlactatemic patients had a lower lactate clearance (473+/-102 ml/kg/h) than those with normal blood lactate (1,002+/-284 ml/kg/h, p < 0.001), whereas lactate production in the two groups was similar (1,194+/-230 and 1,181+/-325 micromol/kg/h, p = 0.90). A second analysis including all the patients confirmed that the blood lactate concentration was closely linked to the reciprocal of lactate clearance (r2 = 0.73, p < 0.001) but not to lactate production (r2 = 0.03, p = 0.29). We conclude that a mild hyperlactatemia occurring in a stable septic patient is mainly due to a defect in lactate utilization.

There is still controversy concerning the beneficial aspects of 'dynamic analgesia' (i.e. pain while coughing or moving) on the reduction of postoperative atelectasis. In this study, we tested the hypothesis that thoracic epidural analgesia (TEA) prevents these abnormalities as opposed to multimodal analgesia with i.v. patient controlled analgesia (i.v. PCA) after thoracotomy. Fifty-four patients undergoing thoracotomy (lung cancer) were randomly assigned to one of the two groups. Clinical respiratory characteristics, arterial blood gas, and pulmonary function tests (forced vital capacity and forced expiratory volume in 1 s) were obtained before surgery and on the next 3 postoperative days. Atelectasis was compared between the two groups by performing computed tomography (CT) scan of the chest at day 3. Postoperative respiratory function and arterial blood gas values were reduced compared with preoperative values (mean (SD) FEV1 day 0: 1.1 (0.3) litre; 1.3 (0.4) litre) but there was no significant difference between groups at any time. PCA and TEA provided a good level of analgesia at rest (VAS day 0: 21 (15/100); 8 (9/100)), but TEA was more effective for analgesia during mobilization (VAS day 0: 52 (3/100); 25 (17/100)). CT scans revealed comparable amounts of atelectasis (expressed as a percentage of total lung volume) in the TEA (7.1 (2.8)%) and in the i.v. PCA group (6.71 (3.2)%). There was no statistical difference in the number of patients presenting with at least one atelectasis of various types (lamellar, plate, segmental, lobar).

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