Venous-arterial PCO2 and pH gradients in acutely ill postsurgical patients.

OBJECTIVE: To investigate the venous-arterial PCO2 gradient, and the mixed venous blood acid-base status together with the oxygen transport variables in a group of acutely ill postsurgical patients. DESIGN: Retrospective, descriptive study of hemodynamic and acid-base data collected immediately after the patients' admission to the Postsurgical Intensive Care Unit. SETTING: Eight-bed, Postsurgical Intensive Care Unit in a University Hospital. PATIENTS: A total of one hundred and one postsurgical patients (87 male, 14 female; 14 to 86 years). INTERVENTIONS: None immediately before the first measurement. MEASUREMENTS AND MAIN RESULTS: Hemodynamic, oxygen transport variables, and arterial and mixed venous acid-base status measurements obtained immediately after the admission to the Postsurgical Intensive Care Unit. The venous-arterial PCO2 gradient was elevated (> 6 torr) in 23 patients and normal (< or = 6 torr) in 78 patients (respectively 9.1 +/- 3.3 vs 4.4 +/- 1.0 torr, p < 0.001). Patients with an increased venous-arterial PCO2 gradient had a higher arterial-venous pH gradient (0.05 +/- 0.03 vs 0.03 +/- 0.01 Unit, p < 0.001) and mixed venous PCO2 (47.5 +/- 8.0 vs 42.1 +/- 5.6 torr, p < 0.001). These patients had a lower cardiac index, oxygen delivery, mixed venous oxygen saturation, and a higher oxygen extraction index than the patients with normal venous-arterial PCO2 and pH gradients. For all the measurements, there was an inverse non linear significant relation between oxygen delivery, venous-arterial PCO2 (r = 0.74, p < 0.001) and pH (r = 0.57, p < 0.01) gradients. CONCLUSIONS: This study suggests that in acutely ill postoperative patients increased venous-arterial PCO2 and pH gradients are directly and principally related to the reduction in blood flow and are both suggestive of low-flow state.

Energy expenditure and gas exchange measurements in postoperative patients: thermodilution versus indirect calorimetry.

OBJECTIVE: To compare a method of measuring energy expenditure and gas exchange using the Fick principle with the standard indirect calorimetry technique. DESIGN: Prospective study of a consecutive sample of postoperative patients. Oxygen consumption (VO2), CO2 production (VCO2), respiratory quotient, and energy expenditure were derived from measurements of variables, including oxygen content and cardiac output. Energy expenditure and gas exchange were measured simultaneously by continuous indirect calorimetry over a 60-min period. SETTING: Surgical ICU in a university hospital. PATIENTS: Twenty-six consecutive patients (45 to 80 yrs) who underwent sustained surgical trauma. Excluded from the study entry were patients with time-related fluctuations of hemodynamic variables, poor cooperation, patients who required supplemental oxygen, or mechanical ventilation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: While the measurements of VO2 and VCO2 by calorimetry and thermodilution were significantly correlated with one another (for VO2, r2 = .93, p less than .001; for VCO2, r2 = .26, p less than .01), VO2 and VCO2 values by indirect calorimetry were consistently greater than VO2 and VCO2 values by the Fick method (p less than .01). The respiratory quotient calorimetric measurements ranged between 0.69 and 0.99, whereas the corresponding thermodilution measurements spread to impossible values, from 0.24 to 1.30 (0.821 +/- 0.07 vs. 0.740 +/- 0.24, p less than .05). There was an insignificant relationship (r2 = .06, p = .21) between the values of respiratory quotient by the two methods. A strong, positive correlation between energy expenditure measured by indirect calorimetry and energy expenditure measured by the Fick method was observed (r2 = .92, p less than .001). The limit of agreement between the two methods was -0.24 +/- 73 kcal/day/m2 (-1.00 +/- 305 kJ/day/m2). CONCLUSIONS: In postoperative patients, while VO2 and energy expenditure measurements by thermodilution are easy to perform and accurate for clinical purposes, VCO2, and respiratory quotient measurements are too imprecise and inaccurate to serve any useful function. Therefore, in those clinical situations in which an evaluation of respiratory quotient and substrate utilization may be useful for purposes of metabolic care of the surgical patient, precise measurements of gas exchange with indirect calorimetry are mandatory.

Diagnosis and differential diagnosis of lymphoepithelial carcinoma in lymph nodes: histological, cytological and electron-microscopic findings.

(1) Lymphoepithelial carcinoma, which occurs in the nasopharynx and palatine tonsils, is a special variant of squamous-cell carcinoma with a non-neoplastic lymphocytic component. (2) The morphology of lymphoepithelial carcinoma is very characteristic if not specific. Therefore, whenever lymphoepithelial carcinoma is diagnosed in a cervical lymph node, the clinician must try to find the primary tumour in the nasopharynx or tonsils, by blind biopsy if necessary. (3) The 'inflammatory' component of lymphoepithelial carcinoma is often very conspicuous. Tuberculoid lesions, with or without caseation necrosis, and marked eosinophilia and plasmacytosis are highly characteristic and help to confirm the diagnosis. (4) The 'inflammatory' component, including the lymphocytes among and around the tumour cells, is not fully understood; but it would appear that T lymphocytes are responsible for all, or most, of the cellular reactions against the tumour.