Disruption of the circadian rhythm of melatonin: A biomarker of critical illness severity

Circadian dysrhythmias occur commonly in critically ill patients reflecting variable effects of underlying illness, ICU environment, and treatments. We retrospectively analyzed the relationship between clinical outcomes and 24-h urinary 6-sulfatoxymelatonin (aMT6s) excretion profiles in 37 critically ill patients with shock and/or respiratory failure. Nonlinear regression was used to fit a 24-h cosine curve to each patient's aMT6s profile, with rhythmicity determined by the zero-amplitude test. From these curves we determined acrophase, amplitude, phase, and night/day ratio. After assessing unadjusted relationships, we identified the optimal multivariate models for hospital survival and for discharge to home (vs. death or transfer to another facility). Normalized aMT6s rhythm amplitude was greater (p = 0.005) in patients discharged home than in those who were not, while both groups exhibited a phase delay. Patients with rhythmic aMT6s excretion were more likely to survive (OR 5.25) and be discharged home (OR 8.89; p < 0.05 for both) than patients with arrhythmic profiles, associations that persisted in multivariate modelling. In critically ill patients with shock and/or respiratory failure, arrhythmic and/or low amplitude 24-h aMT6s rhythms were associated with worse clinical outcomes, suggesting a role for the melatonin-based rhythm as a novel biomarker of critical illness severity.

Effect of early mobilisation on long-term cognitive impairment in critical illness in the USA: a randomised controlled trial

BACKGROUND

Patients who have received mechanical ventilation can have prolonged cognitive impairment for which there is no known treatment. We aimed to establish whether early mobilisation could reduce the rates of cognitive impairment and other aspects of disability 1 year after critical illness.

METHODS

In this single-centre, parallel, randomised controlled trial, patients admitted to the adult medical-surgical intensive-care unit (ICU), at the University of Chicago (IL, USA), were recruited. Inclusion criteria were adult patients (aged ≥18 years) who were functionally independent and mechanically ventilated at baseline and within the first 96 h of mechanical ventilation, and expected to continue for at least 24 h. Patients were randomly assigned (1:1) via computer-generated permuted balanced block randomisation to early physical and occupational therapy (early mobilisation) or usual care. An investigator designated each assignment in consecutively numbered, sealed, opaque envelopes; they had no further involvement in the trial. Only the assessors were masked to group assignment. The primary outcome was cognitive impairment 1 year after hospital discharge, measured with a Montreal Cognitive Assessment. Patients were assessed for cognitive impairment, neuromuscular weakness, institution-free days, functional independence, and quality of life at hospital discharge and 1 year. Analysis was by intention to treat. This trial was registered with ClinicalTrials.gov, number NCT01777035, and is now completed.

FINDINGS

Between Aug 11, 2011, and Oct 24, 2019, 1222 patients were screened, 200 were enrolled (usual care n=100, intervention n=100), and one patient withdrew from the study in each group; thus 99 patients in each group were included in the intention-to-treat analysis (113 [57%] men and 85 [43%] women). 65 (88%) of 74 in the usual care group and 62 (89%) of 70 in the intervention group underwent testing for cognitive impairment at 1 year. The rate of cognitive impairment at 1 year with early mobilisation was 24% (24 of 99 patients) compared with 43% (43 of 99) with usual care (absolute difference -19·2%, 95% CI -32·1 to -6·3%; p=0·0043). Cognitive impairment was lower at hospital discharge in the intervention group (53 [54%] 99 patients vs 68 [69%] 99 patients; -15·2%, -28·6 to -1·7; p=0·029). At 1 year, the intervention group had fewer ICU-acquired weaknesses (none [0%] of 99 patients vs 14 [14%] of 99 patients; -14·1%; -21·0 to -7·3; p=0·0001) and higher physical component scores on quality-of-life testing than did the usual care group (median 52·4 [IQR 45·3-56·8] vs median 41·1 [31·8-49·4]; p<0·0001). There was no difference in the rates of functional independence (64 [65%] of 99 patients vs 61 [62%] of 99 patients; 3%, -10·4 to 16·5%; p=0·66) or mental component scores (median 55·9 [50·2-58·9] vs median 55·2 [49·5-59·7]; p=0·98) between the intervention and usual care groups at 1 year. Seven adverse events (haemodynamic changes [n=3], arterial catheter removal [n=1], rectal tube dislodgement [n=1], and respiratory distress [n=2]) were reported in six (6%) of 99 patients in the intervention group and in none of the patients in the usual care group (p=0·029).

INTERPRETATION

Early mobilisation might be the first known intervention to improve long-term cognitive impairment in ICU survivors after mechanical ventilation. These findings clearly emphasise the importance of avoiding delays in initiating mobilisation. However, the increased adverse events in the intervention group warrants further investigation to replicate these findings.

FUNDING

None.

Immunomodulatory fecal metabolites are associated with mortality in COVID-19 patients with respiratory failure

Respiratory failure and mortality from COVID-19 result from virus- and inflammation-induced lung tissue damage. The intestinal microbiome and associated metabolites are implicated in immune responses to respiratory viral infections, however their impact on progression of severe COVID-19 remains unclear. We prospectively enrolled 71 patients with COVID-19 associated critical illness, collected fecal specimens within 3 days of medical intensive care unit admission, defined microbiome compositions by shotgun metagenomic sequencing, and quantified microbiota-derived metabolites (NCT #04552834). Of the 71 patients, 39 survived and 32 died. Mortality was associated with increased representation of Proteobacteria in the fecal microbiota and decreased concentrations of fecal secondary bile acids and desaminotyrosine (DAT). A microbiome metabolic profile (MMP) that accounts for fecal secondary bile acids and desaminotyrosine concentrations was independently associated with progression of respiratory failure leading to mechanical ventilation. Our findings demonstrate that fecal microbiota composition and microbiota-derived metabolite concentrations can predict the trajectory of respiratory function and death in patients with severe SARS-Cov-2 infection and suggest that the gut-lung axis plays an important role in the recovery from COVID-19.

Immediate Effect of Mechanical Ventilation Mode and Sedative Infusion on Measured Diaphragm Thickness

Rationale: In patients who are mechanically ventilated, diaphragm thinning on ultrasound is thought to correlate with diaphragm atrophy and has been associated with prolonged intubation. Factors other than atrophy, however, may cause changes in diaphragm thickness, which may confound studies examining changes in diaphragm thickness over time. Objectives: To determine if changes in the mode of mechanical ventilation or an interruption of sedatives have immediate effects on diaphragm thickness measurements in adult patients in the intensive care unit who are mechanically ventilated. Methods: Adult patients receiving invasive mechanical ventilation for less than 48 hours were included. Diaphragm thickness was measured at end-expiration and peak inspiration using ultrasound while patients were receiving both volume assist-control and pressure-support modes in a randomized crossover fashion. In patients receiving sedatives, additional measurements were taken after an interruption of sedatives. Measurements were compared between modes and on assist-control before and after an interruption of sedatives. Results: Of 85 patients enrolled, 66 had measurements on assist-control and spontaneous modes, and 40 had measurements before and after an interruption of sedatives. End-expiratory diaphragm thickness increased by a median of 0.08 mm after an interruption of sedatives (95% confidence interval [CI], 0.002 mm to 0.164 mm; P = 0.017), corresponding to a median increase of 6.5%. No difference was seen when comparing measurements taken on volume assist-control and pressure support (median difference, 0 mm; 95% CI, -0.07 mm to 0.08 mm; P = 0.98). Conclusions: End-expiratory diaphragm thickness increased by 6.5% after an interruption of sedatives. The effect of sedatives on measured diaphragm thickness should be considered in future studies examining changes in diaphragm thickness over time. Clinical trial registered with Clinicaltrials.gov (NCT04319939).

Bedside estimates of dead space using end-tidal CO2 are independently associated with mortality in ARDS

Purpose

In acute respiratory distress syndrome (ARDS), dead space fraction has been independently associated with mortality. We hypothesized that early measurement of the difference between arterial and end-tidal CO₂ (arterial-ET difference), a surrogate for dead space fraction, would predict mortality in mechanically ventilated patients with ARDS.

Methods

We performed two separate exploratory analyses. We first used publicly available databases from the ALTA, EDEN, and OMEGA ARDS Network trials (N = 124) as a derivation cohort to test our hypothesis. We then performed a separate retrospective analysis of patients with ARDS using University of Chicago patients (N = 302) as a validation cohort.

Results

The ARDS Network derivation cohort demonstrated arterial-ET difference, vasopressor requirement, age, and APACHE III to be associated with mortality by univariable analysis. By multivariable analysis, only the arterial-ET difference remained significant (P = 0.047). In a separate analysis, the modified Enghoff equation ((P_aCO₂–P_ETCO₂)/P_aCO₂) was used in place of the arterial-ET difference and did not alter the results. The University of Chicago cohort found arterial-ET difference, age, ventilator mode, vasopressor requirement, and APACHE II to be associated with mortality in a univariate analysis. By multivariable analysis, the arterial-ET difference continued to be predictive of mortality (P = 0.031). In the validation cohort, substitution of the arterial-ET difference for the modified Enghoff equation showed similar results.

Conclusion

Arterial to end-tidal CO₂ (ETCO₂) difference is an independent predictor of mortality in patients with ARDS.

Characteristics of Critically Ill Adults With Sacrococcygeal Unavoidable Hospital-Acquired Pressure Injuries: A Retrospective, Matched, Case-Control Study

PURPOSE

To identify characteristics of critically ill adults with sacrococcygeal, unavoidable hospital-acquired pressure injuries (uHAPIs).

DESIGN

Retrospective, matched, case-control design.

SUBJECTS/SETTING

Patients admitted to adult intensive care units (ICUs) at an urban academic medical center from January 2014 through July 2016.

METHODS

Thirty-four patients without uHAPI were matched to 34 patients with sacrococcygeal uHAPI. Time points of interest included admission to the ICU, the week preceding the definitive assessment date, and hospital discharge status. Variables of interest included length of stay, any diagnosis of sepsis, severity of illness, degree of organ dysfunction/failure, supportive therapies in use (eg, mechanical ventilation), and pressure injury risk (Braden Scale score).

RESULTS

All 34 sacrococcygeal pressure injuries were classified as uHAPI using the pressure injury prevention inventory instrument. No statistically significant differences were noted between patients for severity of illness, degree of organ dysfunction/failure, or pressure injury risk at ICU admission. At 1 day prior to the definitive assessment date and at discharge, patients with uHAPI had significantly higher mean Sequential Organ Failure Assessment (SOFA) scores (greater organ dysfunction/failure) and lower mean Braden Scale scores (greater pressure injury risk) than patients without uHAPI. Patients with uHAPI had significantly longer lengths of stay, more supportive therapies in use, were more often diagnosed with sepsis, and were more likely to die during hospitalization.

CONCLUSION

Sacrococcygeal uHAPI development was associated with progressive multiorgan dysfunction/failure, greater use of supportive therapies, sepsis diagnosis, and mortality. Additional research investigating the role of multiorgan dysfunction/failure and sepsis on uHAPI development is warranted.

Impact of Vasoactive Medications on ICU-Acquired Weakness in Mechanically Ventilated Patients

BACKGROUND

Vasoactive medications are commonly used in the treatment of critically ill patients, but their impact on the development of ICU-acquired weakness is not well described. The objective of this study is to evaluate the relationship between vasoactive medication use and the outcome of ICU-acquired weakness.

METHODS

This is a secondary analysis of mechanically ventilated patients (N = 172) enrolled in a randomized clinical trial of early occupational and physical therapy vs conventional therapy, which evaluated the end point of ICU-acquired weakness on hospital discharge. Patients underwent bedside muscle strength testing by a therapist blinded to study allocation to evaluate for ICU-acquired weakness. The effects of vasoactive medication use on the incidence of ICU-acquired weakness in this population were assessed.

RESULTS

On logistic regression analysis, the use of vasoactive medications increased the odds of developing ICU-acquired weakness (odds ratio [OR], 3.2; P = .01) independent of all other established risk factors for weakness. Duration of vasoactive medication use (in days) (OR, 1.35; P = .004) and cumulative norepinephrine dose (μg/kg/d) (OR, 1.01; P = .02) (but not vasopressin or phenylephrine) were also independently associated with the outcome of ICU-acquired weakness.

CONCLUSIONS

In mechanically ventilated patients enrolled in a randomized clinical trial of early mobilization, the use of vasoactive medications was independently associated with the development of ICU-acquired weakness. Prospective trials to further evaluate this relationship are merited.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01777035; URL: www.clinicaltrials.gov.

Effect of Noninvasive Ventilation Delivered by Helmet vs Face Mask on the Rate of Endotracheal Intubation in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial

IMPORTANCE

Noninvasive ventilation (NIV) with a face mask is relatively ineffective at preventing endotracheal intubation in patients with acute respiratory distress syndrome (ARDS). Delivery of NIV with a helmet may be a superior strategy for these patients.

OBJECTIVE

To determine whether NIV delivered by helmet improves intubation rate among patients with ARDS.

DESIGN, SETTING, AND PARTICIPANTS

Single-center randomized clinical trial of 83 patients with ARDS requiring NIV delivered by face mask for at least 8 hours while in the medical intensive care unit at the University of Chicago between October 3, 2012, through September 21, 2015.

INTERVENTIONS

Patients were randomly assigned to continue face mask NIV or switch to a helmet for NIV support for a planned enrollment of 206 patients (103 patients per group). The helmet is a transparent hood that covers the entire head of the patient and has a rubber collar neck seal. Early trial termination resulted in 44 patients randomized to the helmet group and 39 to the face mask group.

MAIN OUTCOMES AND MEASURES

The primary outcome was the proportion of patients who required endotracheal intubation. Secondary outcomes included 28-day invasive ventilator-free days (ie, days alive without mechanical ventilation), duration of ICU and hospital length of stay, and hospital and 90-day mortality.

RESULTS

Eighty-three patients (45% women; median age, 59 years; median Acute Physiology and Chronic Health Evaluation [APACHE] II score, 26) were included in the analysis after the trial was stopped early based on predefined criteria for efficacy. The intubation rate was 61.5% (n = 24) for the face mask group and 18.2% (n = 8) for the helmet group (absolute difference, -43.3%; 95% CI, -62.4% to -24.3%; P < .001). The number of ventilator-free days was significantly higher in the helmet group (28 vs 12.5, P < .001). At 90 days, 15 patients (34.1%) in the helmet group died compared with 22 patients (56.4%) in the face mask group (absolute difference, -22.3%; 95% CI, -43.3 to -1.4; P = .02). Adverse events included 3 interface-related skin ulcers for each group (ie, 7.6% in the face mask group had nose ulcers and 6.8% in the helmet group had neck ulcers).

CONCLUSIONS AND RELEVANCE

Among patients with ARDS, treatment with helmet NIV resulted in a significant reduction of intubation rates. There was also a statistically significant reduction in 90-day mortality with helmet NIV. Multicenter studies are needed to replicate these findings.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01680783.

Impact of early mobilization on glycemic control and ICU-acquired weakness in critically ill patients who are mechanically ventilated

BACKGROUND

ICU-acquired weakness (ICU-AW) has immediate and long-term consequences for critically ill patients. Strategies for the prevention of weakness include modification of known risk factors, such as hyperglycemia and immobility. Intensive insulin therapy (IIT) has been proposed to prevent critical illness polyneuropathy. However, the effect of insulin and early mobilization on clinically apparent weakness is not well known.

METHODS

This is a secondary analysis of all patients with mechanical ventilation (N = 104) previously enrolled in a randomized controlled trial of early occupational and physical therapy vs conventional therapy, which evaluated the end point of functional independence. Every patient had IIT and blinded muscle strength testing on hospital discharge to determine the incidence of clinically apparent weakness. The effects of insulin dose and early mobilization on the incidence of ICU-AW were assessed.

RESULTS

On logistic regression analyses, early mobilization and increasing insulin dose prevented the incidence of ICU-AW (OR, 0.18, P = .001; OR, 0.001, P = .011; respectively) independent of known risk factors for weakness. Early mobilization also significantly reduced insulin requirements to achieve similar glycemic goals as compared with control patients (0.07 units/kg/d vs 0.2 units/kg/d, P < .001).

CONCLUSIONS

The duel effect of early mobilization in reducing clinically relevant ICU-AW and promoting euglycemia suggests its potential usefulness as an alternative to IIT.

Temporal disorganization of circadian rhythmicity and sleep-wake regulation in mechanically ventilated patients receiving continuous intravenous sedation

OBJECTIVES

Sleep is regulated by circadian and homeostatic processes and is highly organized temporally. Our study was designed to determine whether this organization is preserved in patients receiving mechanical ventilation (MV) and intravenous sedation.

DESIGN

Observational study.

SETTING

Academic medical intensive care unit.

PATIENTS

Critically ill patients receiving MV and intravenous sedation.

METHODS

Continuous polysomnography (PSG) was initiated an average of 2.0 (1.0, 3.0) days after ICU admission and continued ≥ 36 h or until the patient was extubated. Sleep staging and power spectral analysis were performed using standard approaches. We also calculated the electroencephalography spectral edge frequency 95% SEF₉₅, a parameter that is normally higher during wakefulness than during sleep. Circadian rhythmicity was assessed in 16 subjects through the measurement of aMT6s in urine samples collected hourly for 24-48 hours. Light intensity at the head of the bed was measured continuously.

MEASUREMENTS AND RESULTS

We analyzed 819.7 h of PSG recordings from 21 subjects. REM sleep was identified in only 2/21 subjects. Slow wave activity lacked the normal diurnal and ultradian periodicity and homeostatic decline found in healthy adults. In nearly all patients, SEF₉₅ was consistently low without evidence of diurnal rhythmicity (median 6.3 [5.3, 7.8] Hz, n = 18). A circadian rhythm of aMT6s excretion was present in most (13/16, 81.3%) patients, but only 4 subjects had normal timing. Comparison of the SEF₉₅ during the melatonin-based biological night and day revealed no difference between the 2 periods (P = 0.64).

CONCLUSIONS

The circadian rhythms and PSG of patients receiving mechanical ventilation and intravenous sedation exhibit pronounced temporal disorganization. The finding that most subjects exhibited preserved, but phase delayed, excretion of aMT6s suggests that the circadian pacemaker of such patients may be free-running.

Patient-related factors associated with hospital discharge to a care facility after critical illness

BACKGROUND

Many critically ill patients are transferred to other care facilities instead of to home at hospital discharge.

OBJECTIVE

To identify patient-related factors associated with hospital discharge to a care facility after critical illness and to estimate the magnitude of risk associated with each factor.

METHODS

Retrospective cohort study of 548 survivors of critical illness in a medical intensive care unit. Multivariable logistic regression was used to identify independent risk factors for discharge to a care facility. Only the first 72 hours of intensive care were analyzed.

RESULTS

Approximately one-quarter of the survivors of critical illness were discharged to a care facility instead of to home. This event occurred more commonly in older patients, even after adjustment for severity of illness and comorbid conditions (odds ratio [OR] 1.8 for patients ≥ 65 years of age vs patients < 65 years; 95% confidence interval [CI], 1.1-3.1; P = .02). The risk was greatest for patients who received mechanical ventilation (OR, 3.4; 95% CI, 2.0-5.8; P < .001) or had hospitalizations characterized by severe cognitive dysfunction (OR, 8.1; 95% CI, 1.3-50.6; P = .02) or poor strength and/or mobility (OR, 31.7; 95% CI, 6.4-157.3; P < .001). The model showed good discrimination (area under the curve, 0.82; 95% CI, 0.77-0.86).

CONCLUSION

The model, which did not include baseline function or social variables, provided good discrimination between patients discharged to a care facility after critical illness and patients discharged to home. These results suggest that future research should focus on the debilitating effects of respiratory failure and on conditions with cognitive and neuromuscular sequelae.

Early physical and occupational therapy in mechanically ventilated, critically ill patients: a randomised controlled trial

BACKGROUND

Long-term complications of critical illness include intensive care unit (ICU)-acquired weakness and neuropsychiatric disease. Immobilisation secondary to sedation might potentiate these problems. We assessed the efficacy of combining daily interruption of sedation with physical and occupational therapy on functional outcomes in patients receiving mechanical ventilation in intensive care.

METHODS

Sedated adults (>/=18 years of age) in the ICU who had been on mechanical ventilation for less than 72 h, were expected to continue for at least 24 h, and who met criteria for baseline functional independence were eligible for enrolment in this randomised controlled trial at two university hospitals. We randomly assigned 104 patients by computer-generated, permuted block randomisation to early exercise and mobilisation (physical and occupational therapy) during periods of daily interruption of sedation (intervention; n=49) or to daily interruption of sedation with therapy as ordered by the primary care team (control; n=55). The primary endpoint-the number of patients returning to independent functional status at hospital discharge-was defined as the ability to perform six activities of daily living and the ability to walk independently. Therapists who undertook patient assessments were blinded to treatment assignment. Secondary endpoints included duration of delirium and ventilator-free days during the first 28 days of hospital stay. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00322010.

FINDINGS

All 104 patients were included in the analysis. Return to independent functional status at hospital discharge occurred in 29 (59%) patients in the intervention group compared with 19 (35%) patients in the control group (p=0.02; odds ratio 2.7 [95% CI 1.2-6.1]). Patients in the intervention group had shorter duration of delirium (median 2.0 days, IQR 0.0-6.0 vs 4.0 days, 2.0-8.0; p=0.02), and more ventilator-free days (23.5 days, 7.4-25.6 vs 21.1 days, 0.0-23.8; p=0.05) during the 28-day follow-up period than did controls. There was one serious adverse event in 498 therapy sessions (desaturation less than 80%). Discontinuation of therapy as a result of patient instability occurred in 19 (4%) of all sessions, most commonly for perceived patient-ventilator asynchrony.

INTERPRETATION

A strategy for whole-body rehabilitation-consisting of interruption of sedation and physical and occupational therapy in the earliest days of critical illness-was safe and well tolerated, and resulted in better functional outcomes at hospital discharge, a shorter duration of delirium, and more ventilator-free days compared with standard care.

FUNDING

None.

Efficacy and safety of a paired sedation and ventilator weaning protocol for mechanically ventilated patients in intensive care (Awakening and Breathing Controlled trial): a randomised controlled trial

BACKGROUND

Approaches to removal of sedation and mechanical ventilation for critically ill patients vary widely. Our aim was to assess a protocol that paired spontaneous awakening trials (SATs)-ie, daily interruption of sedatives-with spontaneous breathing trials (SBTs).

METHODS

In four tertiary-care hospitals, we randomly assigned 336 mechanically ventilated patients in intensive care to management with a daily SAT followed by an SBT (intervention group; n=168) or with sedation per usual care plus a daily SBT (control group; n=168). The primary endpoint was time breathing without assistance. Data were analysed by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00097630.

FINDINGS

One patient in the intervention group did not begin their assigned treatment protocol because of withdrawal of consent and thus was excluded from analyses and lost to follow-up. Seven patients in the control group discontinued their assigned protocol, and two of these patients were lost to follow-up. Patients in the intervention group spent more days breathing without assistance during the 28-day study period than did those in the control group (14.7 days vs 11.6 days; mean difference 3.1 days, 95% CI 0.7 to 5.6; p=0.02) and were discharged from intensive care (median time in intensive care 9.1 days vs 12.9 days; p=0.01) and the hospital earlier (median time in the hospital 14.9 days vs 19.2 days; p=0.04). More patients in the intervention group self-extubated than in the control group (16 patients vs six patients; 6.0% difference, 95% CI 0.6% to 11.8%; p=0.03), but the number of patients who required reintubation after self-extubation was similar (five patients vs three patients; 1.2% difference, 95% CI -5.2% to 2.5%; p=0.47), as were total reintubation rates (13.8%vs 12.5%; 1.3% difference, 95% CI -8.6% to 6.1%; p=0.73). At any instant during the year after enrolment, patients in the intervention group were less likely to die than were patients in the control group (HR 0.68, 95% CI 0.50 to 0.92; p=0.01). For every seven patients treated with the intervention, one life was saved (number needed to treat was 7.4, 95% CI 4.2 to 35.5).

INTERPRETATION

Our results suggest that a wake up and breathe protocol that pairs daily spontaneous awakening trials (ie, interruption of sedatives) with daily spontaneous breathing trials results in better outcomes for mechanically ventilated patients in intensive care than current standard approaches and should become routine practice.

Daily sedative interruption in mechanically ventilated patients at risk for coronary artery disease*

OBJECTIVES

To determine the prevalence of myocardial ischemia in mechanically ventilated patients with coronary risk factors and compare periods of sedative interruption vs. sedative infusion.

DESIGN

Prospective, blinded observational study.

SETTING

Medical intensive care unit of tertiary care medical center.

PATIENTS

Intubated, mechanically ventilated patients with established coronary artery disease risk factors.

INTERVENTIONS

Continuous three-lead Holter monitors with ST-segment analysis by a blinded cardiologist were used to detect myocardial ischemia. Ischemia was defined as ST-segment elevation or depression of >0.1 mV from baseline.

MEASUREMENTS AND MAIN RESULTS

Comparisons between periods of awakening from sedation vs. sedative infusion were made. Vital signs, catecholamine levels, and time with ischemia detected by Holter monitor during the two periods were compared. Heart rate, mean arterial pressure, rate-pressure product, respiratory rate, and catecholamine levels were all significantly higher during sedative interruption. Eighteen of 74 patients (24%) demonstrated ischemic changes. Patients with myocardial ischemia had a longer intensive care unit length of stay (17.4+/-17.5 vs. 9.6+/-6.7 days, p=.04). Despite changes in vital signs and catecholamine levels during sedative interruption, fraction of ischemic time did not differ between the time awake vs. time sedated [median [interquartile range] of 0% [0, 0] compared with 0% [0, 0] while they were sedated [p=.17]). The finding of similar fractions of ischemic time between awake and sedated states persisted with analysis of the subgroup of 18 patients with ischemia.

CONCLUSIONS

Myocardial ischemia is common in critically ill mechanically ventilated patients with coronary artery disease risk factors. Daily sedative interruption is not associated with an increased occurrence of myocardial ischemia in these patients.

Usefulness of the External Jugular Vein Examination in Detecting Abnormal Central Venous Pressure in Critically Ill Patients

BACKGROUND

Central venous pressure (CVP) provides important information for the management of critically ill patients. The external jugular vein (EJV) is easier to visualize than the internal jugular vein and may give a reliable estimate of CVP.

METHODS

To determine the usefulness of the EJV examination in detecting abnormal CVP values, we performed a prospective blinded evaluation comparing it with CVP measured using an indwelling catheter in critically ill patients with central venous catheters. Blinded EJV examinations were performed by clinicians with 3 experience levels (attending physicians, residents and fellows, and interns and fourth-year medical students) to estimate CVP (categorized as low [</=5 cm of water] or high [>/=10 cm of water]). The usefulness of the EJV examination in discriminating low vs high CVP was measured using receiver operating characteristic curve analysis.

RESULTS

One hundred eighteen observations were recorded among 35 patients. The range of CVP values was 2 to 20 cm of water. The EJV was easier to visualize than the internal jugular vein (mean visual analog scale score, 8 vs 5; P<.001). The reliability for determining low and high CVP was excellent, with areas under the curve of 0.95 (95% confidence interval [CI], 0.88-1.00) and 0.97 (95% CI, 0.92-1.00), respectively, for attending physicians and 0.86 (95% CI, 0.78-0.95) and 0.90 (95% CI, 0.84-0.96), respectively, for all examiners.

CONCLUSION

The EJV examination correlates well with catheter-measured CVP and is a reliable means of identifying low and high CVP values.

The relationship between sedative infusion requirements and permissive hypercapnia in critically ill, mechanically ventilated patients

OBJECTIVE

Permissive hypercapnia (PH) may result from mechanical ventilation (MV) strategies that intentionally reduce minute ventilation. Sedative doses required to tolerate PH have not been well characterized. With increased attention to lung-protective ventilation, characterization of sedative requirements with PH and determination of sedative dose changes with PH are needed.

DESIGN

Retrospective analysis.

SETTING

Tertiary care university hospital.

PATIENTS

We evaluated 124 patients randomized in a previous study to either propofol or midazolam. PH was employed in ten of 60 patients receiving propofol and 13 of 64 patients receiving midazolam.

INTERVENTIONS

We analyzed dosing of propofol and midazolam in patients undergoing PH through a retrospective analysis of an existing database on MV patients. Total sedative (propofol and midazolam) dose was recorded for the first three days of MV. Linear regression analysis (dependent variable: sedative dose) was used to analyze the following independent variables: PH, age, gender, daily sedative interruption, type of respiratory failure, presence of hepatic and/or renal failure, Acute Physiology and Chronic Health Evaluation II score, morphine dose, and Ramsay sedation score.

MEASUREMENTS AND MAIN RESULTS

Propofol dose was higher in PH patients (42.5+/-16.2 vs. 27.0+/-15.3; p=.02); Midazolam dose did not differ between PH and non-PH patients (0.05 [0.04, 0.14] vs. 0.05 [0.03, 0.07]; p=.17). By univariate linear regression analysis, propofol dose was significantly dependent on PH, age, type of respiratory failure, morphine dose, and Ramsay score, with PH (regression coefficient, 11.7; 95% confidence interval, 1.2-22.7; p=.03) and age (regression coefficient, -0.3; 95% confidence interval -0.5 to -0.08; p=.005) remaining significant by multivariate linear regression. By univariate linear regression analysis, midazolam dose was dependent on age, morphine dose, and Ramsay score, but not PH; only morphine dose (regression coefficient, 0.44; 95% confidence interval, 0.22-0.67 for a 0.1-unit increase in morphine dose; p<.001) was significant by multivariate linear regression.

CONCLUSIONS

We conclude that higher doses of propofol but not midazolam are required to sedate patients managed with PH.

Daily interruption of sedative infusions and complications of critical illness in mechanically ventilated patients

OBJECTIVE

In critically ill patients receiving mechanical ventilation, daily interruption of sedative infusions decreases duration of mechanical ventilation and intensive care unit length of stay. Whether this sedation strategy reduces the incidence of complications commonly associated with critical illness is not known.

DESIGN

Blinded, retrospective chart review.

SETTING

University-based hospital in Chicago, IL.

PATIENTS

One hundred twenty-eight patients receiving mechanical ventilation and continuous infusions of sedative drugs in a medical intensive care unit.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We performed a blinded, retrospective evaluation of the database from our previous trial of 128 patients randomized to daily interruption of sedative infusions vs. sedation as directed by the medical intensive care unit team without this strategy. Seven distinct complications associated with mechanical ventilation and critical illness were identified: a) ventilator-associated pneumonia; b) upper gastrointestinal hemorrhage; c) bacteremia; d) barotrauma; e) venous thromboembolic disease; and f) cholestasis or g) sinusitis requiring surgical intervention. The incidence of complications was evaluated for each patient's hospital course. One hundred twenty-six of 128 charts were available for review. Patients undergoing daily interruption of sedative infusions experienced 13 complications (2.8%) vs. 26 (6.2%) in those subjected to conventional sedation techniques (p =.04).

CONCLUSIONS

Daily interruption of sedative infusions in critically ill patients undergoing mechanical ventilation reduces intensive care unit length of stay and, in turn, decreases the incidence of complications of critical illness associated with prolonged intubation and mechanical ventilation.

The Long-term Psychological Effects of Daily Sedative Interruption on Critically Ill Patients

Critically ill patients often receive sedatives, which may delay liberation from mechanical ventilation and intensive care unit discharge. Daily interruption of sedatives alleviates these problems, but the impact of this practice on long-term psychological outcomes is unknown. We compared psychological outcomes of intensive care unit patients undergoing daily sedative interruption (intervention) with those without this protocol (control). Assessments using (1) the Revised Impact of Event Scale (evaluates signs of posttraumatic stress disorder [PTSD]), (2) the Medical Outcomes Study 36 item short-form health survey, (3) the State-Trait Anxiety Inventory, (4) the Beck Depression Inventory-2, (5) and the Psychosocial Adjustment to Illness score (overall quality of adjustment to current or residual effects of illness) were done by blinded observers. The intervention group had a better total Impact of Events score (11.2 vs. 27.3, p=0.02), a trend toward a lower incidence of PTSD (0% vs. 32%, p=0.06), and a trend toward a better total Psychosocial Adjustment to Illness score (46.8 vs. 54.3, p=0.08). We conclude that daily sedative interruption does not result in adverse psychological outcomes, reduces symptoms of PTSD, and may be associated with reductions in posttraumatic stress disorder.

The utility of albuterol nebulized with heliox during acute asthma exacerbations

Heliox improves lung deposition of inhaled particles when compared with air or oxygen inhalation. We studied the spirometric effects of albuterol nebulized with heliox during emergency room visits for asthma exacerbations. Forty-five patients were randomized to receive albuterol nebulized with oxygen (control) versus heliox (n = 22 control and 23 heliox subjects). At baseline, demographics, outpatient asthma medications, vital signs, oxygen saturation, and forced expiratory volume in one second were not different between the two groups. Three consecutive albuterol treatments were given to each group. The heliox group had a significantly higher heart rate after albuterol nebulization compared with the control group. Following albuterol Treatment 1, the median change in forced expiratory volume in one second was 14.6% in the control group and 32.4% in the heliox group (p = 0.007). After Treatment 2, the results were 22.7% versus 51.5%, respectively (p = 0.007). After Treatment 3, the results were 26.6% versus 65.1%, respectively (p = 0.016). We conclude that during acute asthma exacerbations, albuterol nebulized with heliox leads to a more significant improvement in spirometry when compared with albuterol nebulized with oxygen. This is likely due to the low-density gas improving albuterol deposition in the distal airways.

Outcomes of critically ill patients denied consideration for liver transplantation

Patients with advanced liver disease (ALD) leading to admission to the ICU are often evaluated for possible orthotopic liver transplantation (OLT). Those deemed ineligible for listing for OLT must be managed by medical therapy. The number of patients not eligible for OLT listing will likely increase given the current organ transplant shortage. We performed a retrospective multivariate analysis of mortality predictors for patients denied listing for OLT. One hundred and eighty-three patients denied OLT listing were evaluated over a 3(1)/(2)-yr period, beginning in 1994. Overall mortality was 56% for those not listed versus 12% for those listed for OLT (p < 0.001). Independent predictors of increased mortality among those not listed were APACHE II score (p = 0.001; OR 1.11), sepsis (p = 0.04; OR 2.41), and the need for mechanical ventilation (p = 0.001; OR 3.71). Gastrointestinal (GI) bleeding was associated with decreased mortality (p = 0.02; OR 0.44). We conclude that critically ill patients with ALD denied OLT listing have substantially higher mortality than those listed for OLT. APACHE II score, sepsis, and the need for mechanical ventilation predict increased mortality in this group. Conversely, GI bleeding predicts decreased mortality; therefore, aggressive resuscitative measures seem merited in these patients.

Daily interruption of sedative infusions in critically ill patients undergoing mechanical ventilation

BACKGROUND

Conous infusions of sedative drugs in the intensive care unit may prolong the duration of mechanical ventilation, prolong the length of stay in the intensive care unit and the hospital, impede efforts to perform daily neurologic examinations, and increase the need for tests to assess alterations in mental status. Whether regular interruption of such infusions might accelerate recovery is not known.

METHODS

We conducted a randomized, controlled trial involving 128 adult patients who were receiving mechanical ventilation and continuous infusions of sedative drugs in a medical intensive care unit. In the intervention group, the sedative infusions were interrupted until the patients were awake, on a daily basis; in the control group, the infusions were interrupted only at the discretion of the clinicians in the intensive care unit.

RESULTS

The median duration of mechanical ventilation was 4.9 days in the intervention group, as compared with 7.3 days in the control group (P=0.004), and the median length of stay in the intensive care unit was 6.4 days as compared with 9.9 days, respectively (P=0.02). Six of the patients in the intervention group (9 percent) underwent diagnostic testing to assess changes in mental status, as compared with 16 of the patients in the control group (27 percent, P=0.02). Complications (e.g., removal of the endotracheal tube by the patient) occurred in three of the patients in the intervention group (4 percent) and four of the patients in the control group (7 percent, P=0.88).

CONCLUSIONS

In patients who are receiving mechanical ventilation, daily interruption of sedative-drug infusions decreases the duration of mechanical ventilation and the length of stay in the intensive care unit.

Outcomes of critically ill cancer patients in a university hospital setting

Critically ill cancer patients constitute a large percentage of admissions to tertiary care medical intensive care units (ICUs). We sought to describe outcomes of such patients, and to evaluate how conditions commonly seen in these patients impact mortality. A total of 348 consecutive medical ICU cancer patients were evaluated. Subgroup comparisons included the three most common cancer types (leukemia, lymphoma, lung cancer), as well as three different treatments/conditions (bone marrow transplant [BMT] versus non-BMT, mechanical ventilation [MV] versus non-MV, neutropenic versus non-neutropenic). There were no mortality differences between patients with leukemia, lymphoma, or lung cancer. By logistic regression, mortality predictors were: MV, hepatic failure, and cardiovascular failure for the group as a whole (41% overall mortality); MV and allogeneic (as compared with autologous) BMT for the BMT group (39% overall mortality); hepatic failure, cardiovascular failure, and persistent acute respiratory distress syndrome (ARDS) for the MV group (67% overall mortality); and MV for the neutropenic group (53% overall mortality). Neutropenia showed no independent association with mortality in the group as a whole or any subgroup analyzed. We conclude that respiratory, hepatic, and cardiovascular failure predict mortality, whereas neutropenia does not. Additionally, we have noted an encouraging improvement in survival in many groups of critically ill cancer patients.

The impact of morbid obesity on oxygen cost of breathing (VO(2RESP)) at rest

Oxygen consumption dedicated to respiratory work (V O(2RESP)) during quiet breathing is small in normal patients. In the morbidly obese, at high minute ventilations, VO(2RESP) is greater than in normal patients, but VO(2RESP) during quiet breathing in these patients is not known. We postulated that such patients have increased VO(2RESP) at rest which may predispose them to respiratory failure when additional respiratory workloads are imposed. We measured baseline VO(2) in morbidly obese patients immediately prior to gastric bypass surgery and again after intubation, mechanical ventilation, and paralysis, and compared their change in VO(2) to nonobese patients scheduled for elective abdominal surgery. Baseline VO(2) was higher in the obese patients compared with control patients (354.6 versus 221.4 ml/min; p = 0.0001) and the change in VO(2) from spontaneous breathing to mechanical ventilation was significant in the obese patients (354.6 versus 297.2 ml/min; p = 0.0002) but not the control patients (221.4 versus 219.8 ml/min; p = 0.86). We conclude that morbidly obese patients dedicate a disproportionately high percentage of total VO(2) to conduct respiratory work, even during quiet breathing. This relative inefficiency suggests a decreased ventilatory reserve and a predisposition to respiratory failure in the setting of even mild pulmonary or systemic insults.

Determination of hemoglobin saturation in patients with acute sickle chest syndrome: a comparison of arterial blood gases and pulse oximetry

STUDY OBJECTIVES

To evaluate three different methods of measuring oxygen saturation in patients suffering from acute sickle chest syndrome.

DESIGN

A prospective, descriptive study of 9 months' duration.

SETTING

A tertiary care university hospital.

PATIENTS

Adult patients with acute sickle chest syndrome scheduled to undergo RBC exchange transfusion.

INTERVENTIONS

None.

MEASUREMENTS

Baseline hemoglobin oxygen saturation was determined simultaneously by (1) calculation based on PaO2 and an oxyhemoglobin dissociation curve algorithm, (2) co-oximetry, and (3) pulse oximetry. These same measures were repeated after exchange transfusion. Baseline and postexchange hemoglobin electrophoresis was performed in all patients.

RESULTS

Baseline calculated saturation overestimated true saturation (determined by co-oximetry) with a baseline mean bias (co-oximetry minus calculated saturation) of -6.78 +/- 2.63% (95% confidence interval for bias: -8.37% to -5.19%). Pulse oximetry was not different than co-oximetry at baseline with a baseline bias of +1.86 +/- 3.25% (95% confidence interval: -0.1% to 3.82%). After exchange transfusion, there was no bias between either co-oximetry and calculated saturation (mean difference: -0.17 +/- 1.31% [95% confidence interval: -0.95% to 0.61%]), or co-oximetry and pulse oximetry (mean difference: +0.3 +/- 1.53% [95% confidence interval: -0.62% to 1.22%]).

CONCLUSIONS

Calculated saturation overestimates true saturation during acute sickle chest syndrome. This discrepancy abates after exchange transfusion. Pulse oximetry more closely follows co-oximetry than does calculated saturation during acute sickle chest syndrome.

The incidence of and clinical variables associated with vancomycin-resistant enterococcal colonization in mechanically ventilated patients

STUDY OBJECTIVES

(1) To determine in our ICU the incidence of vancomycin-resistant enterococcus (VRE) colonization in mechanically ventilated patients without a history of VRE infection or colonization; and (2) to determine the risk factors and outcome variables associated with VRE colonization in these patients.

DESIGN

A prospective cohort study conducted between January 1996 and March 1998.

SETTING

Medical and cardiac critical care units in a tertiary care urban university hospital.

PATIENTS

Mechanically ventilated patients without evidence of pneumonia at the onset of ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Patients underwent rectal cultures by standard methods on day 1, day 3 or 4, day 6 or 7, and day 14 of intubation to detect VRE. Thirteen of 83 patients (16%) had rectal cultures positive for VRE (VRE+) at some point while being mechanically ventilated during their stay in the ICU. In comparison, approximately 15 of 2,100 medical ICU patients (0.7%) had clinical VRE infections as determined by the hospital's infection control program during a 2-year period. VRE+ patients had a higher incidence of immunosuppression than patients who had rectal cultures negative for VRE (VRE-) (9 of 13 [69%] vs 16 of 70 [23%], respectively; p < 0.01) and neutropenia (4 of 13 [31%] vs 5 of 70 [7%], respectively; p < 0.01). Hospital length of stay (LOS) was longer in VRE+ patients than in VRE- patients (27+/-17 days vs 17+/-14 days, respectively; p = 0.05), whereas pre-ICU hospital LOS and ICU LOS were similar in both patient groups. Five of 67 patients (7%) were VRE+ on day 1 of intubation, suggesting colonization at a prior site of care. Three of 29 patients who had subsequent rectal cultures converted to VRE+ while in the ICU. This group had a higher incidence of immunosuppression and neutropenia, and received more vancomycin compared with the patients who remained VRE- (p < 0.01). However, there was no significant difference in the use of other broad-spectrum antibiotics (such as antipseudomonal penicillins, third-generation cephalosporins, quinolones, and clindamycin), enteral tube feedings, or sucralfate between the two groups. In addition, a topical antibiotic paste (a gentamicin, nystatin, polymixin slurry) that was placed in the oropharynx to prevent bacterial overgrowth was not found to increase the incidence of VRE colonization in this patient population.

CONCLUSIONS

The incidence of VRE colonization was surprisingly high: 16% in mechanically ventilated patients in a hospital in which VRE was not previously known to be endemic. Risk factors for the acquisition of VRE colonization included immunosuppression, neutropenia, and vancomycin use. Increased LOSs and hospital costs were seen in VRE+ patients compared to VRE- patients. Whether VRE colonization is a contributor to severe disease that leads to prolonged hospitalization and increased resource allocation or whether it is simply a marker of disease severity cannot be determined from this study. To the extent that specific antibiotic protocols are used to reduce antibiotic-resistant flora in the ICU, monitoring the incidence of VRE in the stool specimens of immunocompromised, mechanically ventilated patients can be a simple and useful tool to assess one effect of these strategies.

Sedation of critically ill patients during mechanical ventilation. A comparison of propofol and midazolam

Propofol (P) and midazolam (M) are frequently given by continuous infusion for sedation in critically ill, mechanically ventilated patients. We compared these drugs with regard to: (1) time-to-awaken; (2) reproducibility of bedside assessments of level of sedation; (3) time-to-sedation; and (4) change in oxygen consumption (V O2) from awake to sedated state. Seventy-three patients were prospectively randomized to receive either P (n=37) or M (n=36). Wake-up times after stopping the drug were assessed by blinded and unblinded observers, by asking patients to perform simple tasks. Times to sedate were assessed by consensus agreement among nurses and investigators. Demographics and APACHE II scores were not different between P and M. The P group had a significantly narrower range of wake-up times with a higher likelihood of waking in less than 60 min. Blinded versus unblinded observations had excellent correlation. Average time to sedate and decrease in V O2 were not different. We conclude that in this patient population: (1) both P and M achieved optimal sedation in a large fraction of patients when administered by specified dosing protocols; (2) P had a faster, more reliable, wake-up time; (3) assessments of time-to-awaken were objective and reproducible; (4) time to sedation was not significantly different; (5) V O2 decreased similarly with both.

Continuous intravenous infusions of lorazepam versus midazolam for sedation during mechanical ventilatory support: a prospective, randomized study

OBJECTIVE

To evaluate the efficacy of continuous infusions of lorazepam vs. midazolam for sedation in the intensive care unit (ICU).

DESIGN

Prospective, randomized study.

SETTING

Large, urban university hospital.

PATIENTS

Twenty adult medical ICU patients receiving mechanical ventilatory support.

INTERVENTIONS

Patients were randomized to receive either lorazepam or midazolam. The infusion rate was adjusted at the bedside by the ICU nurse according to a standardized study protocol to achieve and maintain sedation at Ramsay's sedation level 2 or 3.

MEASUREMENTS AND MAIN RESULTS

Ten patients were randomized to receive lorazepam and ten to receive midazolam. The groups were similar in demographics, Acute Physiology and Chronic Health Evaluation (APACHE) II scores, ICU admission diagnosis, underlying disease processes, and supplemental analgesic administration. The mean time to achieve initial adequate sedation was 124 mins for lorazepam and 105 mins for midazolam. The mean infusion rate at the point of initial sedation was 0.06 mg/kg/hr for lorazepam and 0.15 mg/kg/hr for midazolam. The maximum and mean infusion rates for the entire study period were 0.1 and 0.06 mg/kg/hr, respectively, for lorazepam and 0.29 and 0.24 mg/kg/hr, respectively, for midazolam. The number of infusion rate adjustments per day was 1.9 mg/kg/hr for lorazepam and 3.6 mg/kg/hr for midazolam. Of the surviving patients, the mean time to return to baseline mental status after discontinuation of the benzodiazepine infusion was 261 mins for lorazepam and 1815 mins for midazolam. The mean volume of fluid per day required to deliver the maximum dose of benzodiazepine was 1.2 L for lorazepam (maximum 2.4 L) and 1.3 L for midazolam (maximum 3.6 L).

CONCLUSIONS

While there was a tendency to a longer time required for return to baseline mental status in patients receiving midazolam, this was not statistically significant. Findings of interest concerning both midazolam and lorazepam were: a) time to achieve sedation in medical ICU patients is often prolonged; b) actual dose requirements necessary to maintain sedation in this patient population are larger than the current literature describes; c) time to awaken after discontinuation of the infusion was occasionally delayed for > 24 hrs; d) large volumes of fluid were required to deliver these doses of drug via this route of administration.