Urinary creatinine excretion in the ICU: low excretion does not mean inadequate collection.

BACKGROUND: It has been assumed that a urinary creatinine excretion rate of less than 10 mg/kg per day means an inadequately collected urine sample. OBJECTIVE: To determine the frequency of a urinary creatinine excretion rate of less than 10 mg/kg per day in intensive care unit patients with an adequately collected urine sample. METHOD: In a prospective study of creatinine excretion rates, 24-hour urine samples were evaluated for urinary creatinine in 209 critically ill patients with indwelling Foley catheters. Patients from three adult intensive care units in New York City were divided into two groups. Group 1 patients excreted less than 10 mg/kg per day of urinary creatinine, and group 2 patients excreted at least 10 mg/kg per day. Groups 1 and 2 were first evaluated by dividing the creatinine excretion data by actual body weight. Since actual body weight may overestimate body weight in the critically ill patient, data from groups 1 and 2 were also evaluated using lean body weight. RESULTS: Urinary creatinine excretion was less than 10 mg/kg per day in 36.8% of patients using actual body weight and 29.7% of patients adjusted for lean body weight. The average age of patients in group 1 was 74 +/- 17 years for both actual body weight and lean body weight. The average age of group 2 patients was 60 +/- 19 years for actual body weight and 62 +/- 19 years for lean body weight. There was a significant difference in age between group 1 and group 2 patients for both actual body weight and lean body weight. The proportion of female vs male patients with reduced creatinine excretion was significantly greater, whether the actual body weight or lean body weight adjustment was used. CONCLUSIONS: A urinary creatinine excretion rate of less than 10 mg/kg per day occurs in about one third of critically ill patients, who are more likely to be elderly and female.

The effects of midazolam on the EEG during sedation of critically ill patients.

Patients who require mechanical ventilation are often sedated with midazolam. As clinical signs of sedation are often confusing or nonexistent, and there are few adverse side effects when large doses are infused over a period of days, substantial drug accumulation can result in these critically ill patients, despite the short half-life of midazolam. An objective monitor of sedation would help maintain sedation at a constant level despite changing pharmacokinetic values in patients. We undertook this study to describe the electroencephalographic changes which occur with intravenous midazolam in critically ill patients, and to determine if a relationship exists between these changes and the depth of sedation as measured using a clinical scoring method. A series of 31 critically ill patients who required intravenous midazolam during mechanical ventilation were studied. Four different levels of sedation were defined ranging from execution of verbal commands to no response to suctioning through the tracheal tube or sternal rub. Electroencephalographic recordings were obtained in patients on a daily basis and a concurrent sedation level was determined. High frequency electroencephalogram activity decreased as sedation level increased. This was reflected in decreases in the spectral edge (17.61 to 10.56 Hz (p = 0.0024)), the median frequency (4.27 to 2.56 Hz (p = 0.0278)), and the logarithm of the absolute power in the beta 1 (p = 0.0012), and beta 2 (p < 0.0001) bands. An incidental finding of asymmetry in power between right and left frontal electrodes was observed, with right-sided power being 9-18% greater (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction equation estimates of creatinine clearance in the intensive care unit.

OBJECTIVE: To assess the accuracy of 4 mathematical equations used to estimate creatinine clearance versus the 24-h creatinine clearance in ICU patients. DESIGN: Prospective study of renal function prediction. SETTING: The general adult ICUs of 3 metropolitan hospitals. PATIENTS: 199 critically ill patients with indwelling foley catheters. INTERVENTION AND MEASUREMENTS: Routine 24 h creatinine clearances were evaluated only in patients whose urine volume recorded by the nurses was within 10% of the laboratory's measured volume. Four mathematical equations utilizing age, sex, body weight, height, and plasma creatinine were used as a comparison. There was no difference in estimated creatinine clearance by 3 published methods when the 24 h creatinine clearance exceeded 100 ml/min. When the 24 h creatinine clearance was less than 100 ml/min, however, one prediction equation adjusted for lean body weight (LBW), was the most accurate. This equation accurately predicted creatinine clearance in the range of 30-100 ml/min and slightly overestimated creatinine clearance at 0-30 ml/min (p < 0.01, ANOVA all groups, p < 0.05 Fisher and Scheffé post-hoc tests) with a mean difference +/- 95% confidence interval of -5 +/- 3.1 ml/min. CONCLUSION: An initial rapid estimate of creatinine clearance in critically ill ICU patients with reduced renal function can be determined by an equation adjusted for LBW.

Cost-effectiveness of monoclonal antibodies to gram-negative endotoxin in the treatment of gram-negative sepsis in ICU patients.

OBJECTIVE: To evaluate the fiscal impact and the cost-effectiveness of monoclonal antibodies against gram-negative endotoxin (MAbGNE) in the treatment of presumed gram-negative sepsis. DESIGN: A decision analysis model was developed from (1) data from two phase III trials that studied the E5 or HA-1A MAbGNE, and (2) financial data from 1405 septic patients who required intensive care at a large tertiary hospital. SETTING: Intensive care unit (ICU) patients with presumed gram-negative sepsis. PATIENTS: The E5 trial evaluated 468 patients, and the HA-1A study enrolled 543 patients with presumed gram-negative sepsis. INTERVENTIONS: The addition of MAbGNE to standard regimens or standard regimens alone. MAIN OUTCOME MEASURES: Total expected charges and the expected probability of survival were determined for each option. Cost-effectiveness and marginal cost-effectiveness ratios were also derived. Multiple sensitivity and Monte Carlo analyses were performed to test the underlying assumptions. RESULTS: MAbGNE therapy always resulted in higher expected charges; however, these differences were less than its acquisition cost by $870. The cost-effectiveness ratio for MAbGNE, for $2000 and $4000 acquisition costs, was $71,674 and $74,900 per probability of survival, respectively. Sensitivity analysis showed that cost-effectiveness was most affected by diagnostic accuracy, patient selection, and acquisition cost. Monte Carlo analysis showed that MAbGNE was more costly for 71% of simulations, yet the most efficacious option for 79% of simulations. CONCLUSIONS: From the perspective of acute care institutions, MAbGNE is expensive and cannot be justified on a cost-saving basis. However, it may be cost-effective throughout a reasonable range of assumptions.

Ventilatory support during magnetic resonance imaging.

Ventilatory support during magnetic resonance imaging is difficult because metallic objects on ventilatory support devices can interfere with the imaging field and/or become magnetized and move inside the patient or become flying projectiles. We report the successful MRI examination of an intubated respirator-dependent pediatric patient. Ventilatory support was carried out with a plastic ambu bag, exhalation valve circuit, and tubing.

Room-temperature thermodilution cardiac output: central venous vs right ventricular port.

OBJECTIVE: To assess the accuracy of room-temperature thermodilution cardiac output measurements from the right ventricular port. In addition, waveform patterns were evaluated to determine the actual location of the right ventricular port. DESIGN: Central venous port cardiac output measurements were compared with right ventricular port cardiac output measurements using the same right-heart catheter. SETTING: The general intensive care unit of Memorial Sloan-Kettering Cancer Center. PATIENTS: Thirty-seven critically ill cancer patients with 38 different right-heart catheters were evaluated. INTERVENTION: Four injections of 10 mL normal saline at room temperature were made through each port; the results of the last three injections were averaged. Cardiac output determinations from both ports were completed in less than 10 minutes. The order of port injection was random. RESULTS: No difference was noted between cardiac output determinations from the two ports in a paired t test. Of 38 right-heart catheters, 17 were in the right ventricle and the other 21 in the right atrium. A comparison of ports in the 17 right ventricle catheters showed no difference with a significant (P < .01; R2 = 0.96) correlation. CONCLUSION: Thermodilution cardiac output measurements using 10 mL normal saline at room temperature can be determined accurately using the right ventricular port if the central venous port becomes nonfunctional.

Successful management of CMV pneumonia in a mechanically ventilated patient.

We report a case of severe respiratory failure due to cytomegalovirus pneumonitis in a patient who underwent an allogeneic bone marrow transplant, who was successfully treated with the combination of ganciclovir and high-dose intravenous immune globulin. We also reviewed the rationale for the use of combination therapy with an antiviral agent and immunotherapy. Because of the bone marrow toxicity of ganciclovir, an aggressive diagnostic approach, including bronchoalveolar lavage and open lung biopsy, may be necessary to establish a definitive diagnosis prior to institution of therapy.

Thermodilution cardiac output: proximal lumen versus right ventricular port.

OBJECTIVE: To assess the accuracy of thermodilution cardiac output measurements from the right ventricular port vs. the central venous port. In addition, waveform patterns were evaluated in 50 right-heart catheters to determine the actual location of the right ventricular port. DESIGN: Central venous port cardiac output measurements were compared with right ventricular port cardiac output measurements using the same right-heart catheter. SETTING: The general ICU of Memorial Sloan-Kettering Cancer Center. PATIENTS: Forty-seven critically ill cancer patients with 60 different right-heart catheters were evaluated. INTERVENTION: Four injections of 10 mL of iced normal saline were made through each port, with the results of the last three injections averaged. Cardiac output determinations from both ports were completed in less than 10 min. The order of port injection was random. RESULTS: No difference was noted between cardiac output determinations from the two ports (paired t-test). Twenty-five of 50 right-heart catheters were in the right ventricle, with the other 25 in the right atrium. A comparison of ports in the 25 catheters that were in the right ventricle showed no difference with a significant (p less than .01, r2 = .94) correlation. CONCLUSION: Thermodilution cardiac output measurements using 10 mL of iced saline can be determined accurately using the right ventricular port if the central venous port becomes nonfunctional.

Hypertonic nasogastric tube feedings: do they cause diarrhea?

Hypertonic NG tube feeding in hospitalized patients, whether on the hospital ward or in the ICU, is considered a common etiology of diarrhea. To evaluate the accuracy of this assumption, five normal volunteers, ten hospitalized postoperative patients with head and neck cancer, and 24 ICU patients were given hypertonic (690 mosm), low residue, lactose-free tube feedings starting at 30 kcal/kg.day. There was no prior history of diarrhea in any of the groups studied. There was a significant difference in albumin levels between the three groups, with an average albumin of 2.8 g/dl in the ICU patient group; different from 4.5 g/dl present in both the normal volunteer and non-ICU hospitalized patient groups (general linear models procedure from SAS, p less than .05) (Duncan test). Diarrhea was not present in the normal volunteers or non-ICU patients during the feedings, but did occur in 3/24 ICU patients. This difference was not significant. The three patients with diarrhea had an average albumin level of 3.0 g/dl, while the other ICU patients had an average albumin of 2.7 g/dl. We conclude that hypertonic NG tube feedings do not cause diarrhea in normal volunteers or postoperative head and neck cancer patients. However, in a small statistically insignificant percent of mechanically ventilated ICU patients, this regimen may cause diarrhea although no risk factors can be identified.

Age and utilization of intensive care unit resources of critically ill cancer patients.

Older patients, patients with malignancies, and those admitted to ICUs utilize a disproportionate amount of hospital resources. To evaluate the combined impact of age and a diagnosis of malignancy on ICU utilization and outcome, we reviewed the care provided to all 1,212 patients admitted to a medical/surgical ICU in a hospital specializing in the treatment of cancer between January 1, 1986 and December 31, 1987. Patients between 19 and 64 yr (young) were compared with those between 65 and 74 yr (young-old) and with those greater than or equal to 75 yr (old-old) with respect to utilization of nutritional support (total parenteral nutrition [TPN]), mechanical ventilation (MV), pulmonary artery (PA) catheterization, dialysis (D), and blood products (B). Mean length of stay (LOS) in the ICU, primary diagnosis, outcome, and average daily severity of illness scores (ADTIS) were also compared. Old-old patients represented 14% of all ICU patients and young-old patients represented 28%; 64% of old-old and 61% of young-old patients had solid tumors, compared with 36% of younger patients. The ICU mortality of the two older groups was significantly lower than that of the younger patients (17%, 27%, and 30%, respectively). The use of TPN, PA catheters, and D was similar for all three groups, but older patients used less MV and B than the younger patients (p less than .0001, chi2 analysis). The two older groups also had similar LOS and lower average daily Therapeutic Intervention Scoring Systems (TISS) scores than their younger cohort.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency response of the peripheral sampling sites of a clinical mass spectrometer.

Mass spectrometers are used in ICUs and ORs to measure the concentration of medical and anesthetic gases gathered from multiple sites. This investigation was designed to determine the accuracy of a clinical system, which included 12 ICU bedside stations monitored by a medical mass spectrometer (Perkin-Elmer RMS III, Pomona, CA). Each site station was connected to the analyzing unit via two Teflon tubes, one permanently installed, 30-m long, and the second disposable, 2.4-m long. A gas mixture containing 95% O2 and 5% CO2, alternating with room air, was delivered to a solenoid valve and from there to the connecting tubes. Gas flow-rate, delay time, rise time, and peak and trough concentrations were determined for each gas at solenoid cycling frequencies of 25, 50, and 100/min. After the first set of measurements, the 30-m tubes were thoroughly cleaned and all measurements repeated. In addition, the authors also measured CO2 delay and rise times when the gas was delivered to the mass spectrometer through an unused 30-m tube or a new 2.4-m tube. Gas flow-rate increased from 143 +/- 12 ml/min (mean +/- SD) to 238 +/- 9 ml/min after the tubes were cleaned. Delay time was identical for all gases at all solenoid cycling rates but decreased significantly (P less than 0.05), from 11.5 +/- 0.3 to 4.8 +/- 0.7 s after the ceiling tubes were cleaned. As solenoid valve rate increased, the difference between measured and actual gas concentration increased. The lowest accuracy was 63.6 +/- 2.1%, for CO2 at 100 cycles/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Isotonic nasogastric tube feedings: do they cause diarrhea?

NG tube feedings in hospitalized patients, whether in a ward or ICU, are considered a common etiology of diarrhea. To evaluate the accuracy of this assumption, 13 hospitalized postoperative patients with head and neck cancer, 11 ICU patients, and five healthy volunteers were given isotonic, low-residue, lactose-free tube feedings starting at 30 kcal/kg.day. There was no prior history of diarrhea in any patient studied. There was a significant difference in both albumin levels and diarrhea incidence in the three groups (analysis of variance, p less than .05). Diarrhea occurred in four of 11 ICU patients while receiving feedings, but not in the healthy volunteers or non-ICU patients. The four patients with diarrhea had an average albumin level of 2.8 g/dl, while the other ICU patients had an average albumin of 2.6 g/dl. We conclude that isotonic NG tube feedings do not cause diarrhea in healthy volunteers or postoperative head and neck cancer patients. However, in some mechanically ventilated ICU patients, this regimen may cause diarrhea even though no risk factors can be clearly identified.

Assist control versus synchronized intermittent mandatory ventilation during acute respiratory failure.

Controversy persists as to the relative advantages and disadvantages of synchronized intermittent mandatory ventilation (SIMV) vs. assist/control ventilation (A/C) in the management of acute respiratory failure. In an effort to resolve these differences, we evaluated differences in hemodynamic, metabolic, ventilatory, and oxygenation variables during ventilation with both SIMV and A/C using a crossover protocol in critically ill patients without chronic obstructive pulmonary disease. Despite differences in ventilation, resting energy expenditure, and oxygen delivery in specific subgroups of patients, we found no evidence to support any clear-cut advantage of SIMV or A/C in the acute management of respiratory failure. Careful assessment of individual patients may indicate which patient might benefit from each modality of support.

An automated mechanism for protection of mass spectrometry sampling tubing.

The usefulness of medical mass spectrometers in intensive care units can be limited by too frequent obstruction of the tubing that transports gases from the patients to the analyzing unit. To overcome this problem, we developed an automated system consisting of an infrared light sensor and a three-way valve. One port of the three-way valve connects to 2.4-m disposable tubing that collects gases from the patient's airway. The second port is connected to a mass spectrometer analyzing unit through 30-m permanently installed tubing. The third port is connected to a pressurized oxygen source. An infrared light sensor is placed on the shorter tubing, between the patient and the three-way valve. When increased optical density is detected, due to entrainment of respiratory secretions, the three-way valve is activated. Gas flow is closed between the patient and the mass spectrometer and opened between the pressurized oxygen source and patient tubing to flush its contents. During the six years that the protection system has been in use, the frequency with which the disposable gas collection tubing is changed has been halved. Furthermore, periodic tests of delay and response times, performed at each bedside station, indicate that permanent connection tubing only needed cleaning at 2- to 3-year intervals. The system has decreased the cost of operating our mass spectrometers while also reducing periods of unavailability due to equipment failure.