Alvar Net

Nosocomial respiratory tract infections in multiple trauma patients. Influence of level of consciousness with implications for therapy.

A prospective study of 161 multiple trauma patients was carried out to determine the incidence, the causative agents, and the outcome of nosocomial respiratory tract infections in this highly selected population. Thirty-eight (23.6 percent) patients developed a nosocomial pneumonia (NP). In addition, there were four superinfections in three patients, representing an incidence of 26 percent (42 of 161). Incidence of NP was significantly greater among comatose patients (42.2 vs 13.3 percent, p less than 0.05). Furthermore, purulent tracheobronchitis was diagnosed in six patients. The causative agent of NP was identified in 36 (85.7 percent) episodes by means of fiberoptic bronchoscopies with protected specimen brush sampling. Staphylococcus aureus (55.8 percent) was the predominant pathogen isolated in multiple trauma patients in coma (Glasgow coma score [GCS] below 9 during a period greater than 24 h), while aerobic Gram-negative bacilli were responsible for the majority of cases in the remaining population studied. The overall mortality rate was 19.8 percent, but only five deaths were related to NP. We conclude that nosocomial respiratory tract infections are a frequent problem in multiple trauma patients, especially in those with GCS below 9, although this complication is associated with a relatively low mortality. Among patients with GCS below 9, S aureus was a frequent finding; consequently, antimicrobial therapy in this population needs to be different than that for the remaining multiple trauma patients with NP.

Risk factors for infection byPseudomonas aeruginosa in patients with ventilator-associated pneumonia

Objectiveto investigate the epidemiology of infection byPseudomonas aeruginosa in patients with ventilator-associated pneumonia (VAP).Designprospective clinical study.Settinga medical-surgical ICU in a university hospital.Patientswe followed-up 568 mechanically ventilated patients and 83 episodes of VAP with etiologic diagnosis in 72 patients were retained for analysis.ResultsPs. aeruginosa was isolated in 22 (26.5%) episodes in 18 patients. Of these episodes 7 were directly responsible for death. Using logistic regression analysis, the risk of VAP due toPs. aeruginosa was increased in patients with chronic obstructive pulmonary disease (relative risk (RR)=29.9, 95% confidence interval (CI)=4.86-184.53), a mechanical ventilation period longer than 8 days (RR=8.1, 95% CI=1.01-65.40) and prior use of antibiotics (RR=5.5, 95% CI=0.88-35.01).Conclusionspatients with VAP and these factors have a greater risk of infection byPs. aeruginosa and empirical therapy for these episodes should include anti-pseudomonal activity until etiologic diagnosis is established.

Nosocomial bacteremia in a medical-surgical intensive care unit: epidemiologic characteristics and factors influencing mortality in 111 episodes.

ObjectiveTo analyze the epidemiology and factors influencing mortality of ICU-acquired bacteremia.DesignProspective clinical study.SettingA medical-surgical ICU in an university hospital.PatientsWe recorded variables from 111 consecutive ICU-acquired episodes for a 3-year period.ResultsThe attack rate was 1.9 episodes per 100 patientdays. The commonest isolates were coagulase-negative staphylococci,Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Intravascular catheters were the most frequent source of infection. Overall mortality was 31.5%, and 65.7% of all deaths were directly attributable to infection. Bacteremia from intra-abdominal, lower respiratory tract or unknown origin were associated with a poor prognosis. A logistic regression analysis defined intraabdominal origin (p=0.01, OR=15.7) and presence of shock (p=0.04, OR=3.3) as independently influencing the risk of death. No significant differences were found for the remaining variables studied.Conclusions: Epidemiology and etiology of ICU-acquired bacteremia does not differ seriously in respect to nosocomial bacteremia among unselected populations, although it is associated with a greater incidence and overall mortality. Presence of shock is the most important modificable variable affecting the outcome.

Gentamicin volume of distribution in critically ill septic patients

Gentamicin intrapatient pharmacokinetics variations were studied in 40 critically ill medical patients, suffering gram-negative sepsis. These patients were studied in two phases throughout gentamicin treatment: firstly, on the second day of treatment, when aggressive fluid therapy was required, and secondly, five days later, when patients had achieved a more stable clinical condition. Pharmacokinetic parameters were determined using least squares linear regression analysis assuming a one-compartment model using the Sawchuk-Zaske method. The apparent volume of distribution (Vd) in the first phase of the study was 0.43±0.12 L/kg, while on the seventh day of treatment it was 0.29±0.17 L/kg (p<0.001). Statistically significant differences were also observed for peak serum concentration (p<0.001), total dosage recommended (p<0.001) and half-life (p<0.05), whilst differences were not found for trough levels. From the analysis of the results obtained, we recommend increasing the initial dosage and monitoring plasma levels within the first days of therapy in critically ill patients treated with gentamicin, since important variations in aminoglycoside Vd related to disease, fluid balance and renal function, commonly occur in these patients.

Clinical InvestigationsNosocomial Respiratory Tract Infections in Multiple Trauma Patients: Influence of Level of Consciousness with Implications for Therapy

A prospective study of 161 multiple trauma patients was carried out to determine the incidence, the causative agents, and the outcome of nosocomial respiratory tract infections in this highly selected population. Thirty-eight (23.6 percent) patients developed a nosocomial pneumonia (NP). In addition, there were four superinfections in three patients, representing an incidence of 26 percent (42 of 161). Incidence of NP was significantly greater among comatose patients (42.2 vs 13.3 percent, p less than 0.05). Furthermore, purulent tracheobronchitis was diagnosed in six patients. The causative agent of NP was identified in 36 (85.7 percent) episodes by means of fiberoptic bronchoscopies with protected specimen brush sampling. Staphylococcus aureus (55.8 percent) was the predominant pathogen isolated in multiple trauma patients in coma (Glasgow coma score [GCS] below 9 during a period greater than 24 h), while aerobic Gram-negative bacilli were responsible for the majority of cases in the remaining population studied. The overall mortality rate was 19.8 percent, but only five deaths were related to NP. We conclude that nosocomial respiratory tract infections are a frequent problem in multiple trauma patients, especially in those with GCS below 9, although this complication is associated with a relatively low mortality. Among patients with GCS below 9, S aureus was a frequent finding; consequently, antimicrobial therapy in this population needs to be different than that for the remaining multiple trauma patients with NP.

Post-neurosurgical and spontaneous gram-negative bacillary meningitis in adults.

In order to evaluate the clinical aspects of gram-negative bacillary meningitis (GNBM) we reviewed the charts of 20 adult patients with the discharge diagnosis of meningitis caused by gram-negative bacilli (bacteriologically proved) seen between 1973 and 1984. Nine patients had post-neurosurgical (post-NS) GNBM and 11 patients spontaneous (S) GNBM; the mean age of the former was 42 +/- 16 years and of the latter 56 +/- 14 years (p less than 0.05). The overall mortality rate was 50% (33% in the post-NS group and 64% in the S group). The glucose levels in CSF were significantly lower in the patients who died. Patients treated with combined aminoglycoside therapy presented a lower mortality rate than those treated with intravenous aminoglycoside only (25% versus 70%). We suggest that if aminoglycoside therapy is employed, these antibiotics must be administered both intravenously and directly into CNS.

Polymicrobial bacteremia in critically ill patients

ObjectiveTo characterize the epidemiology of polymicrobial bacteremia (PMB) among critically ill patients.DesignProspective clinical study.SettingUniversity medical center.PatientsAll patients with positive blood cultures in a medical-surgical ICU.MeasurementsPMB represents 8.4% of all true bacteremia in our ICU. Most of these patients were post-operative but none had malignancies or significant immunodepression. Over three-quarters of the episodes were nosocomial. No significant differences in factors associated with PMB were found when they were compared with a cohort of 154 monomicrobial episodes. Enterobacteriaceae were the most common organisms. Intravascular devices (42.8%) were the most common source of PMB, followed by intra-abdominal origin (21.4%). The overall mortality was 7.1%, a lower rate than has previously been described.ConclusionsWe suggest catheter replacement in patients who develop PMB and improving techniques of catheter maintenance in order to reduce its incidence.

Inspiratory effort and occlusion pressure in triggered mechanical ventilation

We have studied eleven patients ventilated in the assisted mode during recovery from acute respiratory failure. We have measured the effort required to trigger the pressure demand valve for 3 different ventilators, and have measured the occulusion pressure as an index of neuromuscular inspiratory drive. We found a delay in the opening of the demand valve, as previously described by other authors. We also found a close correlation between the effort required to open the demand valve and the occlusion pressure. We conclude that the inspiratory effort required to open the demand valve, in the assist mode, is greater than the preset trigger level and that it is well correlated with the neuromuscular inspiratory drive. This inspiratory effort against the closed demand valve, allows the measurement of the occlusion pressure.

Acute renal failure following massive mannitol infusion.

Mannitol is an osmotic diuretic agent widely used in the treatment of cerebral edema and in the prophylaxis of acute renal failure [1]. The kidneys are the major source of excretion of mannitol (90% excreted within 24 h of intravenous administration) [2]. Renal insufficiency will markedly impair excretion, leading to accumulation in extracellular fluid space [1, 2]. Thus, mannitol intoxication has been reported to be a potentially life-threatening complication when mannitol is used unrestrictedly in patients with established renal failure [3, 4]. The aim of this letter is to report on a patient with diabetic nephropa-thy and no known other predisposing factors in whom acute oliguric renal failure occurred as a consequence of infusion of massive quantities of mannitol. A 50 year-old woman arrived at the emergency room with progressive obnubilation and right hemiparesis. She had a history of diabetic nephropathy, and 6 months earlier suffered an episode of acute renal failure due to iodic contrast medium, remaining with a creatinine clearance of 18 ml/min. Intracranial haemorrage was suspected, and 200 g of mannitol was administered as well as thiopental sodium, insulin, ranitidine, and dexamethasone. A computerized tomography scan without contrast medium did not show signs of cerebral bleeding. Serum creatinine was 248 μmol/l, urea 27 mmol/l, Na 130, and K 4.5 mmol/l. Within the first 2 h the patient presented diuresis of 758 ml, though later she was anuric and did not respond to furosemide. Morever, consciousness decreased progressively until the patient entered profound coma. Haemodynamic stability was maintained throughout. During the following 48 h the patient was anuric and presented hypervolaemic signs which led to the institution of peritoneal dialysis. The patient required mechanical ventilation due to Cheyne-Stokes respiration. Twelve hours after Table 1. Laboratory data

Accuracy of an indirect carbon dioxide Fick method in determination of the cardiac output in critically ill mechanically ventilated patients

We evaluated the accuracy of an indirect CO2 Fick method for measuring cardiac output in 30 critically ill mechanically ventilated patients. When the Fick principle was applied to CO2 using estimated PaCO2, the cardiac output obtained underestimated the thermodilution technique showing a lack of accuracy. However, there was a significant correlation between thermodilution and CO2 rebreathing methods using measured (r=0.92; p<0.001) and estimated (r=0.60; p<0.01) arterial PCO2. The regression equation using measured arterial PCO2 was y=0.59+0.91x, and for estimated arterial PCO2 was y=1.7+0.33x. The results suggest that the CO2 rebreathing method using measured arterial PCO2 may be useful to determine cardiac output in those seriously ill patients on artificial ventilation not requiring right heart catheterization.