Karim Lakhal

The Feasibility of Ultrasound to Assess Subglottic Diameter

BACKGROUND:In healthy patients, the narrowest diameter of the subglottic upper airway is the width of the air-column at the level of the cricoid cartilage. This diameter governs the selection of the endotracheal tube size, as excessive tube diameter may damage the tracheal mucosa leading to postextubation stridor or subglottic stenosis. Unfortunately, selecting endotracheal tube size based on height, weight, or age does not reliably lead to the proper tube. The knowledge of airway diameter, especially using a bedside noninvasive tool, could therefore be helpful in anesthesia and intensive care. METHODS:We studied 19 healthy volunteers (27 ± 3 yr, nine females) to compare the transverse diameter of the cricoid lumen assessed by ultrasonography and magnetic resonance imaging. RESULTS:We found a strong correlation between the two techniques (r = 0.99, P < 0.05) confirmed by Bland–Altman analysis with a bias of 0.14 mm, a precision of 0.33 mm, and limits of agreement of −0.68 mm/0.96 mm. CONCLUSION:In young healthy adults, ultrasonography appeared to be a reliable tool to assess the diameter of the subglottic upper airway.

Respiratory pulse pressure variation fails to predict fluid responsiveness in acute respiratory distress syndrome

IntroductionFluid responsiveness prediction is of utmost interest during acute respiratory distress syndrome (ARDS), but the performance of respiratory pulse pressure variation (ΔRESPPP) has scarcely been reported. In patients with ARDS, the pathophysiology of ΔRESPPP may differ from that of healthy lungs because of low tidal volume (Vt), high respiratory rate, decreased lung and sometimes chest wall compliance, which increase alveolar and/or pleural pressure. We aimed to assess ΔRESPPP in a large ARDS population.MethodsOur study population of nonarrhythmic ARDS patients without inspiratory effort were considered responders if their cardiac output increased by >10% after 500-ml volume expansion.ResultsAmong the 65 included patients (26 responders), the area under the receiver-operating curve (AUC) for ΔRESPPP was 0.75 (95% confidence interval (CI95): 0.62 to 0.85), and a best cutoff of 5% yielded positive and negative likelihood ratios of 4.8 (CI95: 3.6 to 6.2) and 0.32 (CI95: 0.1 to 0.8), respectively. Adjusting ΔRESPPP for Vt, airway driving pressure or respiratory variations in pulmonary artery occlusion pressure (ΔPAOP), a surrogate for pleural pressure variations, in 33 Swan-Ganz catheter carriers did not markedly improve its predictive performance. In patients with ΔPAOP above its median value (4 mmHg), AUC for ΔRESPPP was 1 (CI95: 0.73 to 1) as compared with 0.79 (CI95: 0.52 to 0.94) otherwise (P = 0.07). A 300-ml volume expansion induced a ≥2 mmHg increase of central venous pressure, suggesting a change in cardiac preload, in 40 patients, but none of the 28 of 40 nonresponders responded to an additional 200-ml volume expansion.ConclusionsDuring protective mechanical ventilation for early ARDS, partly because of insufficient changes in pleural pressure, ΔRESPPP performance was poor. Careful fluid challenges may be a safe alternative.

Clinical relevance of pulse pressure variations for predicting fluid responsiveness in mechanically ventilated intensive care unit patients: the grey zone approach

IntroductionPulse pressure variation (PPV) has been shown to predict fluid responsiveness in ventilated intensive care unit (ICU) patients. The present study was aimed at assessing the diagnostic accuracy of PPV for prediction of fluid responsiveness by using the grey zone approach in a large population.MethodsThe study pooled data of 556 patients from nine French ICUs. Hemodynamic (PPV, central venous pressure (CVP) and cardiac output) and ventilator variables were recorded. Responders were defined as patients increasing their stroke volume more than or equal to 15% after fluid challenge. The receiver operating characteristic (ROC) curve and grey zone were defined for PPV. The grey zone was evaluated according to the risk of fluid infusion in hypoxemic patients.ResultsFluid challenge led to increased stroke volume more than or equal to 15% in 267 patients (48%). The areas under the ROC curve of PPV and CVP were 0.73 (95% confidence interval (CI): 0.68 to 0.77) and 0.64 (95% CI 0.59 to 0.70), respectively (P <0.001). A grey zone of 4 to 17% (62% of patients) was found for PPV. A tidal volume more than or equal to 8 ml.kg-1 and a driving pressure (plateau pressure - PEEP) more than 20 cmH2O significantly improved the area under the ROC curve for PPV. When taking into account the risk of fluid infusion, the grey zone for PPV was 2 to 13%.ConclusionsIn ventilated ICU patients, PPV values between 4 and 17%, encountered in 62% patients exhibiting validity prerequisites, did not predict fluid responsiveness.

Noninvasive monitoring of blood pressure in the critically ill: reliability according to the cuff site (arm, thigh, or ankle).

Objective:In the critically ill, blood pressure measurements mostly rely on automated oscillometric devices pending the intra-arterial catheter insertion or after its removal. If the arms are inaccessible, the cuff is placed at the ankle or the thigh, but this common practice has never been assessed. We evaluated the reliability of noninvasive blood pressure readings at these anatomic sites. Design:Prospective observational study. Setting:Medical–surgical intensive care unit. Patients:Patients carrying an arterial line with no severe occlusive arterial disease. Intervention:Each patient underwent a set of three pairs of noninvasive and intra-arterial measurements at each site (arm, ankle, thigh [if Ramsay sedation scale >4]) and, in case of circulatory failure, a second set of measurements after a cardiovascular intervention (volume expansion, change in catecholamine dosage). Measurements and Main Results:In 150 patients, whatever the cuff site, the agreement between invasive and noninvasive readings was markedly higher for mean arterial pressure than for systolic or diastolic pressure. For mean arterial pressure measurement, arm noninvasive blood pressure was reliable (mean bias of 3.4 ± 5.0 mm Hg, lower/upper limit of agreement of –6.3/13.1 mm Hg) contrary to ankle or thigh noninvasive blood pressure (mean bias of 3.1 ± 7.7 mm Hg and 5.7 ± 6.8 mm Hg and lower/upper limits of agreement of –12.1/18.3 mm Hg and –7.7/19.2 mm Hg, respectively). During acute circulatory failure (n = 83), arm noninvasive blood pressure but also ankle and thigh noninvasive blood pressure allowed a reliable detection of 1) invasive mean arterial pressure <65 mm Hg (area under the receiver operating characteristic curve of 0.98 [0.92–1], 0.93 [0.85–0.97], and 0.93 [0.85–0.98] for arm, ankle, and thigh noninvasive blood pressure, respectively); and 2) a significant (>10%) increase in invasive mean arterial pressure after a cardiovascular intervention (area under the receiver operating characteristic curve of 0.99 [0.92–1], 0.90 [0.80–0.97], and 0.96 [0.87–0.99], respectively). Conclusion:In our population, arm noninvasive mean arterial pressure readings were accurate. Either the ankle or the thigh may be reliable alternatives, only to detect hypotensive and therapy-responding patients. (Crit Care Med 2012; 40:–1213)

Tracking Hypotension and Dynamic Changes in Arterial Blood Pressure with Brachial Cuff Measurements

BACKGROUND: Arterial cannulation is strongly recommended during shock. Nevertheless, this procedure is associated with significant risks and may delay other emergent procedures. We assessed the discriminative power of brachial cuff oscillometric noninvasive blood pressure (NIBP) for identifying patients with an invasive mean arterial blood pressure (MAP) below 65 mm Hg or increasing their invasive MAP after cardiovascular interventions. METHODS: This prospective study, conducted in three intensive care units, included adults in circulatory failure who underwent 45° passive leg raising, 300 mL fluid loading, and additional 200 mL fluid loading. The collected data were four invasive and noninvasive MAP measurements at each study phase. RESULTS: Among 111 patients (50 septic, 15 cardiogenic, and 46 other source of shock), when averaging measurements of each study phase, NIBP measurements accurately predicted an invasive MAP lower than 65 mm Hg: area under the receiver operating characteristic curve 0.90 (95% CI: 0.71–1), positive and negative likelihood ratios 7.7 (95% CI: 5.4–11) and 0.31 (95% CI: 0.22–0.44) (cutoff 65 mm Hg). For identifying patients increasing their invasive MAP by more than 10%, the area under the receiver operating characteristic curve was 0.95 (95% CI: 0.92–0.96); positive and negative likelihood ratios (cutoff 10%) were 25.7 (95% CI: 10.8–61.4) and 0.26 (95% CI: 0.2–0.34). CONCLUSIONS: NIBP measurements have a good discriminative power for identifying hypotensive patients and performed even better in tracking MAP changes, provided that one averages four NIBP measurements.

Implementation of an evidence-based extubation readiness bundle in 499 brain-injured patients. a before-after evaluation of a quality improvement project.

RATIONALE Mechanical ventilation is associated with morbidity in patients with brain injury. OBJECTIVES This study aims to assess the effectiveness of an extubation readiness bundle to decrease ventilator time in patients with brain injury. METHODS Before-after design in two intensive care units (ICUs) in one university hospital. Brain-injured patients ventilated more than 24 hours were evaluated during two phases (a 3-yr control phase followed by a 22-mo intervention phase). Bundle components were protective ventilation, early enteral nutrition, standardization of antibiotherapy for hospital-acquired pneumonia, and systematic approach to extubation. The primary endpoint was the duration of mechanical ventilation. MEASUREMENTS AND MAIN RESULTS A total of 299 and 200 patients, respectively, were analyzed in the control and the intervention phases of this before-after study. The intervention phase was associated with lower tidal volume (P < 0.01), higher positive end-expiratory pressure (P < 0.01), and higher enteral intake in the first 7 days (P = 0.01). The duration of mechanical ventilation was 14.9 ± 11.7 days in the control phase and 12.6 ± 10.3 days in the intervention phase (P = 0.02). The hazard ratio for extubation was 1.28 (95% confidence interval [CI], 1.04-1.57; P = 0.02) in the intervention phase. Adjusted hazard ratio was 1.40 (95% CI, 1.12-1.76; P < 0.01) in multivariate analysis and 1.34 (95% CI, 1.03-1.74; P = 0.02) in propensity score-adjusted analysis. ICU-free days at Day 90 increased from 50 ± 33 in the control phase to 57 ± 29 in the intervention phase (P < 0.01). Mortality at Day 90 was 28.4% in the control phase and 23.5% in the intervention phase (P = 0.22). CONCLUSIONS The implementation of an evidence-based extubation readiness bundle was associated with a reduction in the duration of ventilation in patients with brain injury.

Acute Kidney Injury in the Critically Ill: Is Iodinated Contrast Medium Really Harmful?*

Objectives:To assess whether the use of iodinated contrast medium increases the incidence of acute kidney injury in ICU patients, compared with patients not receiving iodinated contrast medium. Design:Prospective observational matched cohort study. Setting:Two ICUs in two tertiary teaching hospitals. Patients:A total of 380 adults were included (20% more than once), before an iodinated contrast medium infusion (contrast inclusions, n = 307) or before an intrahospital transfer without iodinated contrast medium infusion (control inclusions, n = 170). Interventions:None. Measurements and Main Results:Among contrast inclusions, iodinated contrast medium–associated acute kidney injury occurred after 23 administrations (7.5%) according to the Acute Kidney Injury Network definition (stage ≥ 1, over 48 hr). As expected, a broader definition (≥ 25% increase in serum creatinine over 72 hr) yielded a greater incidence (16%). In 146 pairs of contrast and control inclusions, matched on propensity for iodinated contrast medium infusion, the incidence of acute kidney injury was similar (absolute difference in incidence, 0%; 95% confidence interval, –5.2; 5.2%), Acute Kidney Injury Network definition). Hospital mortality was also similar in 71 contrast and 71 control patients included only once and matched the same way. Contrary to iodinated contrast medium infusion (odds ratio, 1.57; 95% confidence interval, 0.69–3.53), the Sequential Organ Failure Assessment score at inclusion (odds ratio, 1.18; 95% confidence interval, 1.07–1.31) and the number of other nephrotoxic agents (odds ratio, 1.38; 95% confidence interval, 1.03–1.85) were independent risk factors for acute kidney injury. Conclusions:The specific toxic effect of monomeric nonionic low-osmolar iodinated contrast medium in ICU patients with multiple renal aggressions seemed minimal. Severity of disease and the global nephrotoxic burden were risk factors for acute kidney injury, regardless of iodinated contrast medium infusion.

Blood pressure monitoring during arrhythmia: agreement between automated brachial cuff and intra-arterial measurements

BACKGROUND Since arrhythmia induces irregular pulse waves, it is widely considered to cause flawed oscillometric brachial cuff measurements of blood pressure (BP). However, strong data are lacking. We assessed whether the agreement of oscillometric measurements with intra-arterial measurements is worse during arrhythmia than during regular rhythm. METHODS Among patients of three intensive care units (ICUs), a prospective comparison of three pairs of intra-arterial and oscillometric BP readings was performed among patients with arrhythmia and an arterial line already present. After each inclusion in the arrhythmia group, one patient with regular rhythm was included as a control. International Organization for Standardization (ISO) standard validation required a mean bias <5 (sd 8) mm Hg. RESULTS In 135 patients with arrhythmia, the agreement between oscillometric and intra-arterial measurements of systolic, diastolic and mean BP was similar to that observed in 136 patients with regular rhythm: for mean BP, similar mean bias [-0.1 (sd 5.2) and 1.9 (sd 5.9) mm Hg]. In both groups, the ISO standard was satisfied for mean and diastolic BP, but not for systolic BP (sd >10 mm Hg) in our ICU population. The ability of oscillometry to detect hypotension (systolic BP <90 mm Hg or mean BP <65 mm Hg), response to therapy (>10% increase in mean BP after cardiovascular intervention) and hypertension (systolic BP >140 mm Hg) was good and similar during arrhythmia and regular rhythm (respective areas under the receiver operating characteristic curves ranging from 0.89 to 0.96, arrhythmia vs regular rhythm between-group comparisons all associated with P>0.3). CONCLUSIONS Contrary to widespread belief, arrhythmia did not cause flawed automated brachial cuff measurements.

The CNAP™ Finger Cuff for Noninvasive Beat-To-Beat Monitoring of Arterial Blood Pressure: An Evaluation in Intensive Care Unit Patients and a Comparison with 2 Intermittent Devices.

BACKGROUND:Continuous and intermittent noninvasive measurements of arterial blood pressure (BP) have not been compared in the same population. In a large panel of intensive care unit patients, we assessed the agreement between CNAP™ (Continuous Noninvasive Arterial Pressure) finger cuff beat-to-beat monitoring of BP and reference intraarterial measurements. Two automated oscillometric brachial cuff devices were also tested: CNAP brachial cuff (used for CNAP finger cuff calibration) and an alternative device. The performance for detecting hypotension (intraarterial mean BP <65 mm Hg or systolic BP <90 mm Hg), response to therapy (therapy-induced increase in mean BP >10%), and hypertension (intraarterial systolic BP >140 mm Hg) was evaluated. We also assessed the between-calibration drift of CNAP finger cuff BP in specific situations: cardiovascular intervention or no intervention. METHODS:With each device, 3 pairs of noninvasive and intraarterial measurements were prospectively collected and analyzed according to current guidelines, the International Organization for Standardization (ISO) standard. The trending ability and drift of the CNAP finger cuff BP were assessed over a 15-minute observation period. RESULTS:In 182 patients, CNAP finger cuff and CNAP brachial cuff readings did not conform to ISO standard requirements (mean bias ± SD exceeding the maximum tolerated 5 ± 8 mm Hg), whereas the alternative automated brachial cuff succeeded for mean and diastolic BP. CNAP finger cuff trending ability was poor (concordance rate <70% over a 15-minute period) owing to a significant drift since calibration, especially if a cardiovascular intervention was performed (n = 75, −7.5 ± 10.2 mm Hg at the 14th minute, ie, before recalibration, versus −2.9 ± 7.9 mm Hg if no cardiovascular intervention occurred, n = 103, P = 0.0008). However, a similar and reliable performance was observed for the detection of hypotension with the CNAP finger cuff (within 4 minutes after calibration) and with the 2 automated brachial cuffs (area under the receiver operating characteristic curve ≥0.91, positive and negative likelihood ratios ≥5 and ⩽0.20, respectively). The performance for the detection of response to therapy or of hypertension was slightly lower. CONCLUSIONS:In a large population of intensive care unit patients, CNAP did not fulfill the ISO criteria and exhibited a relevant between-calibration drift. However, CNAP measurements collected within 4 minutes after calibration were reliable for detecting hypotension, as were oscillometric devices, while providing beat-to-beat measurements. Interestingly, an alternative automated brachial cuff was more reliable than the native one, used for calibration. This information is important to clinicians using those devices and for further development of the CNAP technology.

Povidone iodine: features of critical systemic absorption.

Povidone iodine (PI), a skin antiseptic, is sometimes used internally but this procedure exposes to potentially lethal iodine absorption. Indeed, a 41-year-old woman, with no relevant medical history, developed a transient hypotension, anuric renal failure, hemolysis, coagulopathy and uterine infarction after intra-uterine injection of PI as a dye to check the fallopian tube patency (hydrotubation). Iodemia peaked at 6929 μg/dL (normal range 3.4-8.0 μg/dL), and decreased over the 9 days of renal replacement therapy. Extreme caution should be exercised when PI is in contact with a mucosa, the early recognition of iodine toxicity being of utmost importance to rapidly prompt renal replacement therapy. The main purpose of this report is to highlight the clinical features of PI absorption, whatever the route of administration.