Pavlos Myrianthefs

Central Venous and Mixed Venous Oxygen Saturation in Critically Ill Patients

Background: Although mixed venous O₂ saturation (SvO₂) accurately indicates the balance of O₂ supply/demand and provides an index of tissue oxygenation, the use of a pulmonary artery (PA) catheter is associated with significant costs, risks and complications. Central venous O₂ saturation (ScvO₂), obtained in a less risky and costly manner, can be an attractive alternative to SvO₂. Objectives: To investigate whether the values of ScvO₂ and SvO₂ are well correlated and interchangeable in the evaluation of critically ill ICU patients and to create an equation that could estimate SvO₂ from ScvO₂. Methods: Sixty-one mechanically ventilated patients were catheterized upon admission and ScvO₂ and SvO₂ values were simultaneously measured in the lower part of the superior vena cava and PA respectively. Results: SvO₂ was 68.6 ± 1.2% (mean ± SEM) and ScvO₂ was 69.4 ± 1.1%. The difference is statistically significant (p < 0.03). The correlation coefficient r is 0.945 for the total population, 0.937 and 0.950 in surgical and medical patients, respectively. In 90.2% of patients the difference was <5%. When regression analysis was performed, among 11 models tested, power model [SvO₂ = b0(ScvO₂)^b1] best described the relationship between the two parameters (R² = 0.917). Conclusions: ScvO₂ and SvO₂ are closely related and are interchangeable for the initial evaluation of critically ill patients even if cardiac indices are different. SvO₂ can be estimated with great accuracy by ScvO₂ in 92% of the patients using a power model.

Sleep-Disordered Breathing in Nondialyzed Patients with Chronic Renal Failure

The prevalence and significance of sleep-disordered breathing (SDB) in dialysis-independent chronic renal failure (CRF) remains unknown. We studied the presence of SDB in nondialyzed CRF patients. Diagnostic polysomnography was performed in consecutive stable nondialyzed CRF patients. Inclusion criteria were age ≤70 years, absence of systolic dysfunction or history of pulmonary edema, FEV1 > 70% pr, absence of neurologic disease or hypothyroidism, and calculated creatinine clearance <40 ml/min. Thirty-five patients (19 male, 16 female) were studied. An apnea–hypopnea index (AHI) ≥5/h was present in 54.3% (almost exclusively obstructive events). AHI correlated with urea (r = 0.35, p = 0.037), age (r = 0.379, p = 0.025), and body mass index (BMI) (r = 0.351, p = 0.038), but not with creatinine clearance. AHI or SDB were unrelated to gender. In nondiabetics (n = 25), AHI correlated with urea (r = 0.608, p = 0.001) and creatinine clearance (r = −0.50, p = 0.012). Nondiabetics with severe CRF (calculated GFR < 15 ml/min/1.73 m2) had a significantly higher AHI compared with less severe CRF. Restless legs syndrome (RLS) was present in 37.1% and periodic limb movements in 28.6%. Daytime sleepiness was not associated with respiratory events, but was more common in patients with RLS. The prevalence of SDB and RLS is high in dialysis-independent CRF. SDB weakly correlates with indices of kidney function and this association becomes stronger in nondiabetics.

Serum and Cerebrospinal Fluid Concentrations of Linezolid in Neurosurgical Patients

ABSTRACT Linezolid is a new antimicrobial agent effective against drug-resistant gram-positive pathogens commonly responsible for central nervous system (CNS) infections in neurosurgical patients hospitalized in intensive care units. In order to study the penetration of this antimicrobial into the cerebrospinal fluid (CSF) of such patients, the disposition of linezolid in serum and CSF was studied in 14 neurosurgical patients given linezolid at 600 mg twice daily (1-h intravenous infusion) for the treatment of CNS infections caused by gram-positive pathogens or for prophylactic chemotherapy. Serum and CSF linezolid steady-state concentrations were analyzed by high-pressure liquid chromatography, and the concentration-time profiles obtained were analyzed to estimate pharmacokinetic parameters. The mean ± standard deviation (SD) linezolid maximum and minimum measured concentrations were 18.6 ± 9.6 μg/ml and 5.6 ± 5.0 μg/ml, respectively, in serum and 10.8 ± 5.7 μg/ml and 6.1 ± 4.2 μg/ml, respectively, in CSF. The mean ± SD areas under the concentration-time curves (AUCs) were 128.7 ± 83.9 μg · h/ml for serum and 101.6 ± 59.6 μg · h/ml for CSF, with a mean penetration ratio for the AUC for CSF to the AUC for serum of 0.66. The mean elimination half-life of linezolid in CSF was longer than that in serum (19.1 ± 19.0 h and 6.5 ± 3.6 h, respectively). The serum and CSF linezolid concentrations exceeded the pharmacodynamic breakpoint of 4 μg/ml for susceptible target pathogens for the entire dosing interval in the majority of patients. These findings suggest that linezolid may achieve adequate concentrations in the CSF of patients requiring antibiotics for the management or prophylaxis of CNS infections caused by gram-positive pathogens.

Efficacy of CPR in a general, adult ICU

AIM To investigate the initial cardiopulmonary resuscitation (CPR) success rate and long term survival in an Intensive care unit (ICU) population. PATIENTS All patients with cardiac arrest over a 2-year-period (1999-2000) in a general, adult ICU of a general hospital of Athens. METHODS Retrospective collection of clinical data concerning patients, CPR characteristics and survival rates. RESULTS We examined 111 ICU patients, aged 56.4+/-1.9 years (72 males). SAPS II score was 43.9+/-3.8. CPR was performed in 98.2% of the patients within 30 s. Initial restoration of cardiac function (RCF) and successful CPR rate was 100% while 24 h survival was 9.2%. Survivors at 24 h were younger, mainly males, with lower SAPS II score, mainly with pulmonary disease, ventricular fibrillation or ventricular tachycardia (8/10) and initial pupil reactivity (5/10). Four patients required more than one cycle of CPR. Survival to discharge was zero. CONCLUSION Although the initial successful CPR rate in ICU patients may be high, long term survival and hospital discharge is disappointing. Although ICU patients are better monitored and treated in a timely fashion, they are disadvantaged by chronic underlying diseases, severe current medical illnesses and multi organ dysfunction syndrome (MODS) leads to worst outcome after CPR compared with in-ward patients.

Patient to Nurse Ratio and Risk of Ventilator-Associated Pneumonia in Critically Ill Patients

OBJECTIVE To determine how the patient to nurse ratio affects risk for ventilator-associated pneumonia. METHODS Data from an earlier study in 27 intensive care units in 9 European countries were examined in a secondary analysis. The initial cohort included 2585 consecutive patients who had mechanical ventilation (1) after admission for treatment of pneumonia or (2) for more than 48 hours irrespective of the diagnosis at admission. In units with variable staffing levels, the highest patient to nurse ratio in a 24-hour period was considered. Patients from 6 units that did not provide data on nurse staffing levels were excluded from the analysis. RESULTS Ventilator-associated pneumonia developed in 393 of the 1658 patients (23.7%) in the secondary cohort. In units with patient to nurse ratios of 1 to 1, 2 to 1, 2.5 to 1, and 3 to 1, rates were 9.3%, 25.7%, 18.7%, and 24.2%, respectively (P = .003). Rates were significantly lower (P = .002) in units with a ratio of 1 to 1 (9.3%) than in units with a ratio of more than 1 patient to 1 nurse (24.4%). After adjustments for confounding covariates, ratios of more than 1 patient to 1 nurse were no longer associated with increased risk for ventilator-associated pneumonia. CONCLUSIONS A patient to nurse ratio of 1 to 1 appears to be associated with a lower risk for ventilator-associated pneumonia, but after adjustments for confounding covariates, the difference is not significant.

Severity of illness and outcome in adult patients with Primary Varicella pneumonia

Background: Varicella pneumonia is a serious complication of primary varicella infection in adults that often results in respiratory failure and death. Objective: To analyze the clinical and laboratory manifestations of primary varicella pneumonia in patients admitted to our intensive care unit (ICU). Methods: Retrospective study on patients treated in our ICU with a diagnosis of primary varicella pneumonia during a period of 15 years. We recorded age, gender, smoking habits, clinical and laboratory findings, arterial blood gases, chest radiograph, illness severity (SAPS II), length of stay, necessity for mechanical ventilation, complications, therapy and survival. We examined the influence of the duration of respiratory symptoms and rash prior to admission, and the influence of illness severity on outcome. Results: There was a statistically significant difference in duration of respiratory symptoms, duration of rash and SAPS II on admission between: (a) mechanically ventilated patients vs. spontaneously breathing patients (p < 0.007, p < 0.00, p < 0.00), (b) patients who survived vs. patients with poor outcome (p < 0.001, p < 0.000, p < 0.000), and (c) mechanically ventilated patients with poor outcome vs. mechanically ventilated patients who survived (p < 0.001, p < 0.00, p < 0.000). Overall mortality was 13.6%; death occurred only in mechanically ventilated patients (mortality 33.3%). Conclusions: Primary varicella pneumonia remains a critical problem with significant mortality. When recognized before respiratory failure ensues and mechanical ventilation becomes mandatory, patients could have an excellent outcome. Adult patients who delay asking for medical support, the disease may lead to the need for mechanical ventilation and severe complications with a fatal outcome.

Increased blood troponin levels in ICU patients.

Purpose of reviewCardiac troponins in serum have become the biomarkers of choice for the diagnosis of myocardial infarction. Yet, troponin can also be elevated by a multitude of causes in the absence of overt myocardial ischemia. Such nonspecific elevations are particularly common in the critically ill. This article aims to provide information on the significance of troponin elevations in unselected critically ill patients and in patients with sepsis or septic shock. Recent findingsRecent studies reconsider the possible association of troponin elevations with myocardial infarction in unselected critically ill patients. There are also more data on the prognostic significance of troponin in this population. In patients with sepsis, recent studies suggest that troponin may be a reliable index of sepsis-induced myocardial dysfunction, although the implications of this finding in the management of sepsis remain unclear for the time being. Troponin also appears to be a predictor of short and possibly also long-term outcome in septic patients. The advent of newer assays with even higher sensitivity, may lead to further redefinition of the role of troponin in the ICU. SummaryTroponin is frequently elevated in critically ill patients. More research is needed on the diagnostic and prognostic significance and possible clinical applications of troponin measurements in patients with sepsis and critical illness.

Monitoring plasma voriconazole levels following intravenous administration in critically ill patients: an observational study

Data relating to the pharmacokinetics of voriconazole in critically ill patients are lacking. A prospective observational study was conducted on 18 non-consecutive critically ill patients aged 24-97 years, comprising 12 patients with normal renal function (NRF) [creatinine clearance (CL(Cr)) > or = 60 mL/min] and 6 patients with moderate renal impairment (MRI) (CL(Cr) 40-55 mL/min), administered voriconazole intravenously (6 mg/kg loading dose and 3-4 mg/kg twice daily thereafter) in order to determine the suitability of these doses in this patient population. Steady-state blood levels were monitored and liver and renal function were recorded throughout treatment. Large variability in patient plasma levels was observed, ranging from 37% at < or = 1 mg/L (minimum inhibitory concentration at which, for most fungal pathogens, 90% of isolates are susceptible) to 19% at >5.5mg/L. Moreover, maintaining trough concentrations above clinical breakpoints was not consistently achieved because 16/30 (53%) were < or = 1 mg/L. In a few MRI patients, average concentrations were found to be significantly different compared with those of NRF patients administered the same dose, however this difference was not noted in pharmacokinetic parameters following dose normalisation. None of the patients experienced deterioration in renal or liver function. Recommended voriconazole doses are inadequate to achieve drug concentrations >1 microg/mL over the entire dosing interval in some critically ill patients.

The Effect of Physiotherapy-Based Breathing Retraining on Asthma Control

Background. The mechanism of the breathing retraining effect on asthma control is not adequately based on evidence. Objective. The present study was designed to evaluate the effect of physiotherapy-based breathing retraining on asthma control and on asthma physiological indices across time. Study design. A 6-month controlled study was conducted. Adult patients with stable, mild to moderate asthma (n = 40), under the same specialist’s care, were randomized either to be trained as one group receiving 12 individual breathing retraining sessions (n = 20), or to have usual asthma care (n = 20). The main outcome was the Asthma Control Test score, with secondary outcomes the end-tidal carbon dioxide, respiratory rate, spirometry, and the scores of Nijmegen Hyperventilation Questionnaire, Medical Research Council scale, and SF-36v2 quality-of-life questionnaire. Results. The 2 × 4 ANOVA showed significant interaction between intervention and time in asthma control (F = 9.03, p < .001, η2 = 0.19), end-tidal carbon dioxide (p < .001), respiratory rate (p < .001), symptoms of hypocapnia (p = .001), FEV1% predicted (p = .022), and breathlessness disability (p = .023). The 2 × 4 MANOVA showed significant interaction between intervention and time, with respect to the two components of the SF-36v2 (p < .001). Conclusion. Breathing retraining resulted in improvement not only in asthma control but in physiological indices across time as well. Further studies are needed to confirm the benefits of this training in order to help patients with stable asthma achieve the control of their disease.

Respiratory failure: an overview.

Respiratory failure is defined as a failure in gas exchange due to an impaired respiratory system--either pump or lung failure, or both. The hallmark of respiratory failure is impairment in arterial blood gases. This review describes the mechanisms leading to respiratory failure, the indices that can be used to better describe gas exchange abnormalities and the physiologic and clinical consequences of these abnormalities. The possible causes of respiratory failure are then briefly mentioned and a quick reference to the clinical evaluation of such patients is made. Finally treatment options are briefly outlined for both acute and chronic respiratory failure.