PubMed · 4756384
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L B Berman. 1973. Azotemia.. https://pubmed.ncbi.nlm.nih.gov/4756384/
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The authors analyzed data on 59 hemodialyzed patients who did not have significant disorders of calcium and phosphate metabolism and found that more than 60% suffered from disabling pruritus possibly related to chronic uremia. Both biochemical correlates of the prevalence of pruritus and dialysis efficacy calculated by urea kinetics were investigated. Significantly higher values of blood urea nitrogen and plasma beta 2-microglobulin just before the dialysis session were observed in pruritic patients with lower dialysis efficacy estimated by Kt/V urea and normalized protein catabolic rate (nPCR). After 3 months without changing the dialysis prescriptions, 16 patients with a mean Kt/V urea and a normalized protein catabolic rate (nPCR) of 1.28 and 1.22 g/kg/d, respectively, experienced significant reductions in the degree of pruritus estimated by the pruritic score, from 12.6 +/- 5.1 to 6.3 +/- 3.2. Twenty-two patients with a mean Kt/V urea and an nPCR of 1.09 and 1.01, respectively, continued to have severe pruritus (score: 12.3 +/- 4.7 to 12.7 +/- 6.4). In 9 of 22 patients with prolonged severe pruritus, dialysis efficacy was heightened with an increase in dialyzer membrane area of more than 0.3 m2. Seven of nine patients with increased dialysis prescriptions had significant reductions of the mean pruritic score, from 12.6 +/- 4.8 to 6.3 +/- 2.4, which inversely related to the significant increase of Kt/V urea from 1.05 +/- 0.25 to 1.24 +/- 0.33; among patients whose dialysis prescriptions were not changed, only one had a significant reduction in score. The authors concluded that higher dialysis efficacy with good nutritional state reduces the prevalence and degree of pruritus in hemodialyzed patients.
STUDY OBJECTIVE: To further define the efficacy of routine central venous catheter placement for major head and neck surgery from the standpoint of fluid and blood administration, and various other parameters of perioperative management. DESIGN: Randomized, retrospective chart review. SETTING: University-affiliated medical center. PATIENTS: 104 patients who had undergone major head and neck surgery (defined as surgery lasting longer than 4 hours with a predicted blood loss of 500 ml or greater) at the University of Iowa Hospitals and Clinics between 1985 and 1992. MEASUREMENTS AND MAIN RESULTS: Central venous monitoring was used in 51 of the 104 (49%) procedures. Patients with and without central monitors did not differ in age, weight, preoperative laboratory values [i.e., hemoglobin (Hb), blood urea nitrogen (BUN), creatinine), incidence of significant cardiac or renal disease, or a smoking history exceeding 30 pack years. In addition, these patients did not differ with respect to the following intraoperative characteristics: general type of anesthetic; duration of surgery; estimate of blood loss; Hb values; lowest urine output per hour; development of oliguria; total urine output; amount of replacement of blood, colloid, or crystalloid; development of systolic blood pressure less than 70 mmHg; or use of a myocutaneous flap. Patients also did not differ with respect to the following postoperative characteristics: duration of stay in the surgical intensive care unit or hospital, BUN or creatinine values on days 1 and 2, total urine output or the development of oliguria on days 1 through 3, incidence of reintubation, fever on days 1 through 5, wound dehiscence, death, myocardial infarction, or the development of pneumonia, pulmonary edema, or sepsis. Patients with central monitors had a greater incidence of having a tracheostomy performed and a slightly lower Hb level on the first postoperative day than those without central monitors. CONCLUSIONS: The study raises doubt about the efficacy of routine central venous catheter placement as a necessary guide for fluid and blood administration for these procedures, or as a necessary adjunct for several other parameters of perioperative management. It suggests the need for a randomized, prospective evaluation.
In this paper a time-varying volume, double-pool urea kinetics model is considered and a sensitivity analysis is carried out to determine those patient parameters that have greater influence on the time course of blood urea nitrogen concentration (BUN) during and between dialysis treatment. The model parameters include the urea generation rate, the initial distribution volume of the urea, the ratio between intracellular and extracellular volumes, and the mass transfer coefficient between the two pools. The analysis demonstrates that BUN is highly sensitive to the urea generation rate and total distribution volume whereas it is influenced by the remaining parameters to a much lesser extent. In addition, the location of the absolute maxima of BUN sensitivity functions suggests the rational placement of a reduced number of blood samples that may still allow sufficiently accurate estimates for the parameters of clinical interest, such as the urea generation rate, total distribution volume, and the ratio between intracellular and extracellular volumes. This conclusion has been confirmed by simulation studies where parameter estimation has been performed with a varying number of observation points.