The dosing frequency of aminoglycoside antibiotics may alter efficacy and toxicity independent of total daily dose. Once-daily tobramycin dosing was compared with continuous infusion in three models of efficacy. Acute pneumonia due to Pseudomonas aeruginosa in guinea pigs responded better to once-daily dosing, and chronic pneumonia in rats and endocarditis in rabbits responded equally to both regimens. Dogs given gentamicin, tobramycin, or netilmicin once daily, with maximum serum concentrations of greater than 100 mg/liter, had less nephrotoxicity than dogs given continuous infusions. Tobramycin was given once daily or continuously to 52 patients with cystic fibrosis who in 10 days had no change in creatinine clearance or hearing despite maximum serum tobramycin concentrations of 40 mg/liter. Intermittent dosing of aminoglycosides, causing infrequent large maximum serum concentrations, may be less toxic and equally efficacious as frequent dosing.

The accuracies of physicians' predictions of mortality for 523 patients in a medical intensive care unit were compared with estimates derived from a logistic model. The model utilized a popular severity-of-illness measure, the APACHE II. Accuracy was assessed through its components resolution (discrimination) and calibration. Physicians could better discriminate survivors from nonsurvivors, as measured by the area under the receiver operating characteristic curve (0.89 for physicians vs 0.83 for APACHE II model, p less than 0.001) and by resolution (0.103 for physicians vs 0.130 for APACHE II model, p less than 0.001). Overall, the APACHE II model was better calibrated (0.003 for APACHE II vs 0.021 for physicians, p less than 0.001). While the APACHE II model was better calibrated in the central probability ranges, physicians could more accurately identify those most likely to die. Decisions on withholding or withdrawing treatment are being made daily in intensive care units based on physicians' subjective prognostic estimates. At least for experienced physicians at a major medical center, these estimates are comparable in accuracy to quantitative models.

The impact of age on admission practices and pattern of care were examined in 599 admissions to a medical intensive care unit (MICU) and 290 patients on the conventional medical care divisions of the same hospital. Four age groups were compared: under 55, 55 to 64, 65 to 74, and 75 years of age and over. Severity of illness and prior health were assessed using the Acute Physiology Score (APS) and the Chronic Health Evaluation (CHE) instruments. Resource utilization was assessed using the Therapeutic Intervention Scoring System (TISS) and hospital charges. Patients 65 years of age and over comprised 48% of the MICU sample. The distribution of CHE was different among the four groups. Twenty-one percent of patients under 55 years of age had no prior chronic illness, as compared to less than 8% of older patients. The APS at admission was similar for all age groups, as was admission, daily, and total TISS. Hospital survival declined with age from 85% to 70%, while the likelihood of being designated do not resuscitate (DNR) increased from 10% to 24%. Differences in hospital survival disappeared when controlling for severity of illness and prior health, but differences in DNR status did not. Still, elderly DNR patients received as much resources as younger DNR patients and this was more than non-DNR patients. The sample of patients treated on conventional medical divisions had age distribution similar to the MICU sample. There was some evidence that admission APS (median, 5, 5, 6, 6, respectively, P = .055) and maximum APS (median, 5, 5, 7, 8, respectively, P = .023) differed slightly across age groups.(ABSTRACT TRUNCATED AT 250 WORDS)