Structural and Volumetric Brain MRI Findings in Mild Traumatic Brain Injury

BACKGROUND AND PURPOSE

Routine MR imaging findings are frequently normal following mild traumatic brain injury and have a limited role in diagnosis and management. Advanced MR imaging can assist in detecting pathology and prognostication but is not readily available outside research settings. However, 3D isotropic sequences with ∼1-mm³ voxel size are available on community MR imaging scanners. Using such sequences, we compared radiologists' findings and quantified regional brain volumes between a mild traumatic brain injury cohort and non-brain-injured controls to describe structural imaging findings associated with mild traumatic brain injury.

MATERIALS AND METHODS

Seventy-one military personnel with persistent symptoms and 75 controls underwent 3T MR imaging. Three neuroradiologists interpreted the scans using common data elements. FreeSurfer was used to quantify regional gray and white matter volumes.

RESULTS

WM hyperintensities were seen in 81% of the brain-injured group versus 60% of healthy controls. The odds of ≥1 WM hyperintensity in the brain-injured group was about 3.5 times the odds for healthy controls (95% CI, 1.58-7.72; P = .002) after adjustment for age. A frontal lobe-only distribution of WM hyperintensities was more commonly seen in the mild traumatic brain injury cohort. Furthermore, 7 gray matter, 1 white matter, and 2 subcortical gray matter regions demonstrated decreased volumes in the brain-injured group after multiple-comparison correction. The mild traumatic brain injury cohort showed regional parenchymal volume loss.

CONCLUSIONS

White matter findings are nonspecific and therefore a clinical challenge. Our results suggest that prior trauma should be considered in the differential diagnosis of multifocal white matter abnormalities with a clinical history of mild traumatic brain injury, particularly when a frontal predilection is observed.

Combining multiple biomarkers differentiates between active SJIA, SJIA-MAS and EBV-HLH

Cytokine storm syndromes are a clinically heterogeneous group of conditions resulting from a maladaptive host response to an inflammatory trigger. These syndromes lead to rapid progression of immune-mediated damage to healthy tissues resulting in life-threatening multi-system organ failure. Prompt recognition of disease and medical intervention to limit damage to healthy tissues is essential to prevent cytokine storm morbidity and mortality. However, the diagnosis of cytokine storm syndromes is challenging, given the clinical heterogeneity in disease presentations. Therefore, expeditious and readily available tests to diagnose disease and differentiate between the various types of cytokine storm syndromes are of clinical utility. The recently published work of Shimizu and colleagues brings us closer to making this a reality.

Glycosylated hemoglobin and hyperbaric oxygen coverage denials

Some Medicaid and Medicare fiscal intermediaries are denying hyperbaric oxygen (HBO2) therapy for diabetic foot ulcer (DFU) patients if the glycosylated hemoglobin (HbA1c) > 7.0%. We performed multiple PubMed searches for any diabetic wound healing clinical trial that documented HbA1c and had a wound healing endpoint. We scrutinized 30 peer-reviewed clinical trials, representing more than 4,400 patients. The average HbA1c from the intervention side of the studies was 8.6% (7.2% - 9.9%) and the control/sham side was 8.3% (6.0% - 10.6%). Twelve studies made a direct attempt to link HbA1c and wound healing. Four retrospective studies and one prospective cohort study assert that lower HbA1c favors wound healing, but review of the studies reveal design flaws that invalidate these conclusions. In total, 25 studies showed no direct correlation between HbA1c levels and wound healing. There was no randomized controlled trial (RCT) data demonstrating that HbA1c < 7.0% improves diabetic wound healing. In every study reviewed, wounds healed with high HbA1c levels that would be considered poorly controlled by the American Diabetes Association (ADA). Frequently, patients lack optimal blood glucose control when they have a limb-threatening DFU. The evidence supports that denying hyperbaric oxygen to those with HbA1c > 7.0% is unfounded.

Carbon monoxide poisoning: a new incidence for an old disease

PURPOSE

While carbon monoxide (CO) poisoning is common in the USA, its incidence is uncertain. Fatal poisonings are counted with relative accuracy from death certificate data, but estimates of the more common nonfatal poisonings are either old or limited. This study was performed to estimate the number of emergency department (ED) visits annually in the USA for carbon monoxide poisoning.

BASIC PROCEDURES

ED visit rates in five states (Idaho, Maine, Montana, Utah, and Washington) from three prior studies, each using different methodology, were used to extrapolate independent estimates of national ED visits.

MAIN FINDINGS

After correcting for regional differences in CO poisoning incidence, estimates of national ED visits per year ranging from 32,413 to 56,037 were obtained. Excluding the estimate derived from the Maine rate because it did not include intentional and fire-related poisonings, the national average is 50,558 +/- 4,843 visits per year.

CONCLUSIONS

There are approximately 50,000 ED visits for CO poisoning in the USA annually, 3-5 times the numbers previously estimated. As this disease can result in significant long-term morbidity even when treated, enhanced prevention efforts are warranted.

Basal ganglia volumes following CO poisoning: A prospective longitudinal study

Carbon monoxide (CO) poisoning may result in focal and diffuse neuropathological changes, including basal ganglia lesions. The effect of CO poisoning on basal ganglia volumes over time is unclear. We assessed basal ganglia volumes longitudinally following CO poisoning. We prospectively enrolled 73 CO poisoned patients who underwent brain MR imaging on day 1 (baseline), 2 weeks, and 6 months post-CO poisoning. Basal ganglia volumes were obtained. One patient had bilateral globus pallidus lesions at two weeks and 6 months. Of the CO-poisoned patients 28% had volume reduction in at least one basal ganglia structure by 6 months, of which 21% had putamen, 15% had caudate, 15% had globus pallidus, and 16% had total basal ganglia volume reduction. Putamen volumes were significantly smaller from baseline to six months (p = 0.02). Verbal memory and mental processing speed correlated with smaller putamen and globus pallidus volumes. Carbon monoxide poisoning results in basal ganglia volume reduction 6 months post CO poisoning. Slow mental processing speed and impaired memory correlated with smaller putamen and globus pallidus volumes. Clinicians need to be aware of basal ganglia neuropathologic changes in the absence of observable lesions following CO poisoning.

Monoplace hyperbaric chamber use of U.S. Navy Table 6: a 20-year experience

We report a 20-year experience at LDS Hospital, Salt Lake City, UT using the U.S. Navy Treatment Table 6 (TT6) in an oxygen-filled monoplace hyperbaric chamber (1985-2004). Air breathing was provided via a demand regulator fitted with a SCUBA mouthpiece while the patient wore a nose clip. Intubated patients were mechanically ventilated with a Sechrist 500A ventilator, with a modified circuit providing air, when specified. We treated 90 patients: 72 divers (decompression sickness [DCS] = 67, arterial gas embolism [AGE] = 5), 10 hospital-associated AGE, and 8 miscellaneous conditions. They received a total of 118 TT6 (9 TT6 in intubated patients). Ninety-four percent of the TT6 schedules were tolerated and completed. The intolerance rate from two surveyed multiplace chambers was zero and 3% of 100 TT6 schedules each. Failure to complete the TT6 was due to oxygen toxicity (4) and claustrophobia (3). The U.S. Navy TT6 was well tolerated by patients with DCS or AGE treated in monoplace hyperbaric chambers, but tolerance may not be as high as when treated in the multiplace chamber.

Hypoxemia with air breathing periods in U.S. NAVY Treatment Table 6

Air breathing is used to lessen hyperbaric oxygen (HBO2) toxicity. Hypoxemia could occur during hyperbaric air breathing in patients with lung dysfunction, although this has not been previously reported. We report two cases of hypoxemia during air breathing with two patients treated with the US Navy Table 6. Patient 1 was an 11-year-old male with cerebral gas embolism (during cardiac transplantation), patient 2 was a 66-year-old female with cerebral gas embolism from a central venous catheter accident. Both were mechanically ventilated. We monitored arterial blood gas (ABG) during therapy. In both patients, ABG measurements showed hypoxia during the first air breathing period at 1.9 atm abs (192.5 kPa). If patients require > or = 40% inspired oxygen before HBO2 therapy, oxygenation monitoring is advisable during air breathing periods, especially at lower chamber pressures (< or = 2.0 atm abs).

Comparison of three intravenous infusion pumps for monoplace hyperbaric chambers

We compared the infusion accuracy of the Baxter Flo-Gard 6201, IVAC 530 and Abbott Lifecare 3HB pumps with saline and enteral formula at chamber pressures from 86.1 kPa (0.85 atm abs) to 304 kPa (3.0 atm abs). The Baxter pump infused +/- 10% saline at all tested pressures and rates (1-1,999 ml/hr). At 1 ml/hour, the IVAC infused 18% more saline than expected (86.1 kPa). The Abbott infused -15% and -23% than expected at 202.6 kPa (999 ml/hr) and 304 kPa (800 ml/hr), respectively. A 10-minute chamber compression and decompression (86.1-304-86.1 kPa) resulted in lower-than-expected measured volumes during compression (64-112%) and higher-than-expected measured volumes during decompression (62-114%) at rates of 1, 5, and 10 ml/hr for all pumps. Enteral infusions (100 ml/hour) resulted in -20% to +12% fluid volume discrepancies. In conclusion, the Baxter pump had the best overall performance. Changes observed during compression and decompression may be clinically important.

De novo cryptogenic hepatitis after sustained eradication of hepatitis C following liver transplantation

Patients with recurrent hepatitis C (HCV) after liver transplantation (OLT) are often treated with interferon and ribavirin in an attempt to eradicate HCV and prevent cirrhosis. We report four patients who developed de novo cryptogenic hepatitis following sustained eradication of recurrent HCV, which led to decompensated liver disease in two patients, both of whom required listing for retransplantation. Between September 2000 and October 2001, 38 consecutive patients with recurrent HCV were treated with interferon alpha 2b and ribavirin, of whom eight patients (21%) developed a sustained response to HCV eradication. Four of these patients developed cryptogenic hepatitis, which led to decompensated cirrhosis in two patients. Both patients were listed for retransplantation but died on the waiting list. No etiology for liver disease was identified despite extensive investigations in all four patients including postmortem analysis in the two patients. We hypothesize that these individuals developed an aberrant immune response leading to allograft injury whose severity may be determined by underlying haplotype, degree of immunosuppression, presence/absence of HCV, and duration of treatment. We have not found any similar reports in the literature but anticipate more cases to be reported given the universal use of antiviral therapy for recurrent HCV.

White matter hyperintensities and neuropsychological outcome following carbon monoxide poisoning

BACKGROUND

Carbon monoxide (CO) poisoning may result in white matter hyperintensities (WMH) and neurocognitive impairments.

OBJECTIVE

To assess in a prospective study WMH in CO-poisoned patients and their relationship to cognitive functioning.

METHODS

Seventy-three consecutive CO-poisoned patients were studied. MR scans and neurocognitive tests were administered on day 1 (within 36 hours after CO poisoning), 2 weeks, and 6 months. Age- and sex-matched control subjects for white matter analyses only were obtained from the authors' normative imaging database. MR scans were rated for WMH in the periventricular and centrum semiovale regions, using a 4-point rating scale. Two independent raters rated the scans, and a consensus was reached.

RESULTS

Thirty percent of CO-poisoned patients had cognitive sequelae. Twelve percent of the CO-poisoned patients had WMH, with significantly more periventricular, but not centrum semiovale, WMH than control subjects. The WMH in CO-poisoned patients did not change from day 1 to 6 months. Centrum semiovale hyperintensities were related to worse cognitive performance. Duration of loss of consciousness correlated with cognitive impairment at all three times. Initial carboxyhemoglobin levels correlated with loss of consciousness but not with WMH or cognitive sequelae.

CONCLUSIONS

CO poisoning can result in brain injury manifested by WMH and cognitive sequelae. The WMH were not related to CO poisoning severity. The WMH occurred in both the periventricular and the centrum semiovale regions; however, only those in the centrum semiovale were significantly associated with cognitive impairments.

Pulmonary edema associated with hyperbaric oxygen therapy

We report three cases of pulmonary edema associated with hyperbaric oxygen therapy, including one fatality. All three patients had cardiac disease and reduced left ventricular (LV) ejection fractions (EFs). Two patients had diabetes, and one patient had severe aortic stenosis. Hyperbaric oxygen therapy may contribute to pulmonary edema by increasing LV afterload, increasing LV filling pressures, increasing oxidative myocardial stress, decreasing LV compliance by oxygen radical-mediated reduction in nitric oxide, altering cardiac output between the right and left hearts, inducing bradycardia with concomitant LV dysfunction, increasing pulmonary capillary permeability, or by causing pulmonary oxygen toxicity. We advise caution in the use of hyperbaric oxygen therapy in patients with heart failure or in patients with reduced cardiac EFs.

Verbal memory deficits associated with fornix atrophy in carbon monoxide poisoning

Magnetic resonance (MR) images and neuropsychological testing data of 69 carbon monoxide (CO) poisoned patients were prospectively obtained within 1 day of CO poisoning, two weeks and six months. CO patients' Day 1 cross-sectional fornix surface area measurements, corrected for head size by using a fornix-to-brain ratio (FBR), were compared to normal age and gender-matched controls. Additionally, a within-subjects analysis was performed comparing the mean areas between CO patients' Day 1, 2 weeks and 6-month FBR. The FBR was correlated with patients' neuropsychological data. There were no significant differences between CO patients' Day 1 fornix measurements compared to normal control subjects. However, significant atrophic changes in the fornix of CO poisoned patients occurred at two weeks with no progressive atrophy at 6 months. By 6 months, CO patients showed significant decline on tests of verbal memory (when practice effects were taken into account), whereas visual memory, processing speed and attention/concentration did not decline. This study indicates that CO results in brain damage and cognitive impairments in the absence of lesions and other neuroanatomic markers.

Acute psychosis associated with diving

There are only a few reported cases of psychiatric disorders presenting a s decompression sickness (DCS). Previous reports indicate that DCS can result in personality change, depression, Munchausen's syndrome, and pseudo stroke. We report two cases of acute psychoses that occurred following diving as suspected DCS and were treated with hyperbaric oxygen, which did not improve the psychotic features. One patient had symptoms of DCS including myalgias, weakness, and fatigue; however the symptoms were inconsistent. The symptom onset and nitrogen loading from his dive profiles made the diagnosis of DCS unlikely. The second patient exhibited mild joint pain, fatigue, and psychosis that was temporally associated with diving but no other symptoms of DCS. Following a detailed medical evaluation we determined that these two patients did not have DCS or arterial gas embolism (AGE). Although it is highly unlikely that a pure psychotic episode will arise as a result of DCS, physicians caring for divers with symptoms of DCS or AGE and acute psychosis may consider a trial of recompression therapy while completing the medical evaluation. Divers with acute psychosis without signs and symptoms and benign dive profiles are unlikely to have DCS or AGE.

Carbon monoxide poisoning: interpretation of randomized clinical trials and unresolved treatment issues

Since hyperbaric oxygen therapy (HBO2) appeared as a treatment for CO poisoning in 1960, whether and when to use it for CO poisoning have often been debated. HBO2 has been advocated to treat severe CO poisoning to limit delayed and permanent neurologic sequelae. Initially, inferences about efficacy were based on clinical experience and uncontrolled studies, but since1989, six prospective clinical trials have been reported comparing HBO2 and normobaric O2 administration to treat patients with acute CO poisoning. Of the six trials, four found better clinical outcomes among patients receiving HBO2 while two have shown no treatment effect. The most recent and best-designed randomized controlled clinical trial, performed in Salt Lake City, supports the efficacy of HBO2 in severe acute CO poisoning in accordance with scientific rationale and clinical experience. However, a number of important issues remain for future investigation, which could be addressed in a large multi-center trial. Such a trial should attempt to determine the optimal number of HBO2 treatments and the maximum treatment delay from CO poisoning for HBO2 to provide efficacy in patients with specific risk factors for a poor outcome.

Carboxyhemoglobin half-life in carbon monoxide-poisoned patients treated with 100% oxygen at atmospheric pressure

STUDY OBJECTIVES

There are large reported differences for the carboxyhemoglobin (COHb) half-life (COHb t(1/2)) in humans breathing 100% atmospheric O(2) following CO inhalation in tightly controlled experiments compared to the COHb t(1/2) observed in clinical CO poisoning (range, 36 to 131 min, respectively). Other reports have suggested that the COHb t(1/2) may be affected by gender differences, age, and lung function. We wished to test the hypothesis that the COHb t(1/2) might also be influenced by CO poisoning vs experimental CO exposure, by a history of loss of consciousness (LOC), concurrent tobacco smoking, and by PaO(2). The purpose of the present study was to measure the COHb t(1/2) in a cohort of CO-poisoned patients and to determine if those listed factors influenced the COHb t(1/2).

DESIGN

Retrospective chart review from 1985 to 1995. We calculated the COHb t(1/2) of CO-poisoned patients who were treated with high-flow supplemental atmospheric pressure O(2) delivered by nonrebreather face mask or endotracheal tube.

SETTING

Hyperbaric medicine department of a tertiary-care teaching hospital.

PATIENTS

Of 240 CO-poisoned patients, 93 had at least two COHb measurements > 2% (upper limit of normal) with recorded times of the measurements, permitting calculation of the COHb t(1/2).

RESULTS

The COHb t(1/2) was 74 +/- 25 min (mean +/- 1 SD) with a range from 26 to 148 min. By stepwise multiple linear regression analysis, the PaO(2) influenced the COHb t(1/2) (R(2) = 0.19; p < 0.001), whereas the COHb t(1/2) was not influenced by gender, age, smoke inhalation, history of LOC, concurrent tobacco smoking, degree of initial metabolic acidosis (base excess), or initial COHb level.

CONCLUSIONS

The COHb t(1/2) of 93 CO-poisoned patients treated with 100% O(2) at atmospheric pressure was 74 +/- 25 min, considerably shorter than the COHb t(1/2) reported in prior clinical reports (approximately 130 +/- 130 min) and was influenced only by the patient's PaO(2).

Performance of the Baxter Flo-Gard 6201 volumetric infusion pump for monoplace chamber applications

For non-hyperbaric purposes, the Baxter Flo-Gard 6201 volumetric pump is capable of infusing multiple types of fluids at rates of 1-1,999 ml x h(-1). We designed a study to determine flow accuracy of this pump at variable rates, fluid viscosities, and volumes over a range of chamber pressures. For hyperbaric use, the pump pressure sensor was adjusted. Sodium chloride solution 0.9% (NS), enteral formula, and packed red blood cells (PRBC) were infused at varying rates from 86.1 to 304 kPa (0.85 to 3.0 atm abs). For NS, measured compared to set flow rates ranged from 12.5% to -7.5% at settings of 1 and 5 ml x h(-1) from 86.1 to 304 kPa (0.85 to 3.0 atm abs) pressures, respectively. For NS infusions at a set rate of 100 ml x h(-1), the measured flow was identical to the set rate at all pressures. At flow settings of 1,999 ml x h(-1), the measured flow varied from the set flow by +/-4.9% Enteral infusion at 100 ml x h(-1) showed approximately a 3% increase in the measured vs. set flow rate. PRBC measured flow rates ranged from -0.4 to 6% of the set rate. During chamber compression and decompression, with set flow rates from 1 to 10 ml x h(-1), the measured flow was considerably less than expected during compression and more than expected during decompression. In conclusion, the Baxter Flo-Gard 6201 infusion pump demonstrated acceptable performance for infusing saline, enteral formula, and PRBC at low and high infusion rates into the pressurized monoplace hyperbaric chamber up to 304 kPa (3 atm abs), with the exception of low rates during compression and decompression.

Neuropsychological sequelae and impaired health status in survivors of severe acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a disease of acute respiratory failure manifested by severe hypoxemia with a high mortality rate. Previous outcome studies of ARDS have assessed survival and/or pulmonary function as the primary outcome variables. Cognitive or psychological outcomes following ARDS have not been described, despite the possibility that ARDS patients are at risk for brain injury through hypoxemia or other mechanisms. In the current study 55 consecutive ARDS survivors completed a battery of neuropsychological tests and questionnaires regarding health status, cognitive and psychological outcomes at the time of hospital discharge and 1 yr after onset of ARDS. At hospital discharge, 100% (55 of 55) of survivors exhibited cognitive and affective impairments, as well as problems with health status which affected their quality of life. At 1 yr after ARDS, 17 of 55 (30%) patients still exhibited generalized cognitive decline. Forty-three of 55 (78%) patients had all or at least one of the following: impaired memory, attention, concentration and/or decreased mental processing speed. One year after ARDS a substantial portion of ARDS survivors exhibit impaired health status and cognitive sequelae which may be due to hypoxemia, emboli, inflammation, drug toxicity, and/or other etiologies.

Carbon monoxide poisoning

Carbon monoxide (CO) poisoning is common and frequently unrecognized since the signs and symptoms are relatively nonspecific. CO poisoning causes tissue hypoxia. Additionally, various animal studies have demonstrated that CO interferes with myoglobin, P450, and other enzyme function; causes lipid peroxidation through neutrophil activation; produces oxidative stress manifested by peroxynitrate deposition in endothelium; binds to cytochrome aa3, disrupting intracellular oxygen utilization; can cause neuroexcitotoxicity; and contributes to hippocampal cellular death through apoptosis. Emergency treatment for CO poisoning is 100% oxygen. Hyperbaric oxygen therapy (HBO2) is accepted in CO poisoning, although data from randomized clinical trials regarding the efficacy of HBO2 in CO poisoning is conflicting. CO poisoning, even when treated with supplemental oxygen can leave the patient with permanent neurocognitive or affective problems. Unfortunately, there appears to be no marker or constellation of signs or symptoms at presentation that predicts long-term outcome following CO poisoning. Given the neurocognitive sequelae following CO poisoning, increased awareness and prevention of CO poisoning is imperative.

MRI, quantitative MRI, SPECT, and neuropsychological findings following carbon monoxide poisoning

Carbon monoxide (CO) poisoning has been shown to result in neuropathologic changes and cognitive impairments due to anoxia and other related biochemical mechanisms. The present study investigated brain-behaviour relationships between neuropsychological outcome and SPECT, MRI, and Quantitative magnetic resonance imaging (QMRI) in 21 patients with CO poisoning. Ninety-three per cent of the patients exhibited a variety of cognitive impairments, including impaired attention, memory, executive function, and mental processing speed. Ninety-five per cent of the patients experienced affective changes including depression and anxiety. The results from the imaging studies revealed that 38% of the patients had abnormal clinical MRI scans, 67% had abnormal SPECT scans, and 67% had QMRI findings including hippocampal atrophy and/or diffuse cortical atrophy evidenced by an enlarged ventricle-to-brain ratio (VBR). Hippocampal atrophy was also found on QMRI. SPECT and QMRI appear to be sensitive tools which can be used to identify the neuropathological changes and cerebral perfusion defects which occur following CO poisoning. Cerebral perfusion defects include frontal and temporal lobe hypoperfusion. Significant relationships existed between the various imaging techniques and neuropsychological impairments. The data from this study indicate that a multi-faceted approach to clinical evaluation of the neuropathological and neurobehavioural changes following CO poisoning may provide comprehensive information regarding the neuroanatomical and neurobehavioural effects of CO poisoning.

Operational use and patient care in the monoplace hyperbaric chamber

The author has made an attempt to describe presently available monoplace chambers, provide codes for their appropriate use in hospitals, and emphasize chamber safety. If appropriate safety precautions are not strictly adhered to, catastrophic accidents may occur, and have occurred. Critically ill patients may have indications for HBO and, indeed, can be treated with HBO in the monoplace chamber. This requires strict attention to detail and an understanding of critical care medicine as well as hyperbaric medicine. To facilitate care of these patients within the monoplace chamber several modifications have been implemented. Complete pulmonary and arterial hemodynamic monitoring, transcutaneous and laser Doppler monitoring, as well as vasopressors, sedation, paralysis, and mechanical ventilation can be supplied to patients treated with HBO within a monoplace chamber (Fig. 19). Suction within the monoplace chamber can be accomplished by adapting existing hospital equipment. Likewise, air breaks can be provided to all patients in the monoplace chamber, including those who are intubated and mechanically ventilated. These modifications have been presented here. Hemodynamic and intravenous access to the critically ill patient is important. Physiologic pressures, ECG, and typical intravenous setups have been described. Several techniques that the author has have personally found helpful have also been provided. The final section of this article presents clinical observations in a few critically ill patients. These anecdotes were only included to try to stimulate thought and hopefully an interchange of ideas that may help us deal more effectively with the management of these patients. This article also raises the question of what is the optimal arterial partial pressure of oxygen as opposed to merely treating the HBO patient with a standard protocol, particularly if the patient has a significant right-to-left shunt (anatomic or physiologic). It is hoped that further discussion, thought, and research can help elucidate answers to these questions.

Venous and arterial gas embolism associated with positive pressure ventilation

We report a 53-year-old woman with ARDS who required positive pressure ventilation with positive end-expiratory pressure. She sustained an acute right ventricular myocardial infarction associated with cardiovascular instability. The next day she sustained a fatal cerebral arterial gas embolism. Intravascular gas was documented within the cerebral, coronary, and pulmonary arterial circulations. Clinicians need to be aware of venous and arterial gas embolism as a complication of mechanical ventilation.

Neuropsychological impairments following hantavirus pulmonary syndrome

Recently an outbreak of acute respiratory infection associated with the hantavirus occurred in the southwestern United States. Hantavirus pulmonary syndrome (HPS) is a life threatening illness that carries with it a high mortality rate. Patients with HPS experience prolonged periods of hypoxemia requiring mechanical ventilation and treatment in intensive care units. We have recently seen 2 survivors of HPS. A neuropsychological test battery was administered immediately following their acute hospitalization and at 1 year postrecovery from HPS. Both patients exhibited cognitive impairments immediately following HPS as well as persistent cognitive impairments at 1 year. The cognitive impairments seen in these two HPS survivors are similar to those seen in other patients who have experienced brain anoxia, including memory impairments. It is also possible that hantavirus may directly cause brain injury with concomitant cognitive impairments. Additional research needs to be carried out in order to determine the extent and severity of the cognitive impairments in survivors of HPS.

A computer-assisted management program for antibiotics and other antiinfective agents

BACKGROUND AND METHODS

Optimal decisions about the use of antibiotics and other antiinfective agents in critically ill patients require access to a large amount of complex information. We have developed a computerized decision-support program linked to computer-based patient records that can assist physicians in the use of antiinfective agents and improve the quality of care. This program presents epidemiologic information, along with detailed recommendations and warnings. The program recommends antiinfective regimens and courses of therapy for particular patients and provides immediate feedback. We prospectively studied the use of the computerized antiinfectives-management program for one year in a 12-bed intensive care unit.

RESULTS

During the intervention period, all 545 patients admitted were cared for with the aid of the antiinfectives-management program. Measures of processes and outcomes were compared with those for the 1136 patients admitted to the same unit during the two years before the intervention period. The use of the program led to significant reductions in orders for drugs to which the patients had reported allergies (35, vs. 146 during the preintervention period; P<0.01), excess drug dosages (87 vs. 405, P<0.01), and antibiotic-susceptibility mismatches (12 vs. 206, P<0.01). There were also marked reductions in the mean number of days of excessive drug dosage (2.7 vs. 5.9, P<0.002) and in adverse events caused by antiinfective agents (4 vs. 28, P<0.02). In analyses of patients who received antiinfective agents, those treated during the intervention period who always received the regimens recommended by the computer program (n=203) had significant reductions, as compared with those who did not always receive the recommended regimens (n= 195) and those in the preintervention cohort (n = 766), in the cost of antiinfective agents (adjusted mean, $102 vs. $427 and $340, respectively; P<0.001), in total hospital costs (adjusted mean, $26,315 vs. $44,865 and $35,283; P<0.001), and in the length of the hospital stay days (adjusted mean, 10.0 vs. 16.7 and 12.9; P<0.001). CONCLUSIONS; A computerized antiinfectives-management program can improve the quality of patient care and reduce costs.

Three dimensional image reconstruction of neuroanatomical structures: methods for isolation of the cortex, ventricular system, hippocampus, and fornix

Magnetic Resonance (MR) imaging allows volumetric quantification of a variety of neuroanatomical structures using two dimensional (2D) images as well as three-dimensional (3D) reconstruction of the brain and any of its constituent parts. Three-dimensional analysis permits integration of the neuroanatomical changes which occur in pathologic states, with the cognitive and behavioral changes elucidated through neuropsychological assessment. This paper describes uniform methods for 3D neuroanatomical isolation of the neocortex, ventricular system, and hippocampus in both normal and pathologic states. The 3D methods are described in detail using two different software programs, ANALYZE and IMAGE. Three-dimensional neuroanatomical reconstructions were carried out on a patient who sustained a very severe traumatic brain injury. The 3D image analysis in the patient with traumatic brain injury, revealed structural changes in frontal and temporal cortex, ventricular dilation, and hippocampal atropy. The neuropsychological impairments in this patient, were consistent with the observed neuroanatomical changes revealed on 3D image reconstruction. This technology permits precise determinations of the extent and severity of the neuroanatomical changes which follow neurological injury disease.

Neuropsychologic and functional recovery from severe carbon monoxide poisoning without hyperbaric oxygen therapy

STUDY OBJECTIVE

To test the hypothesis that neuropsychologic test results and functional outcome will be abnormal if hyperbaric oxygen (HBO) is not used in patients with severe carbon monoxide (CO) poisoning.

METHODS

For a 1-year interval, we retrospectively identified all CO-poisoned patients who were comatose on presentation at a large, urban tertiary hospital and did not receive HBO therapy. Prospectively, 6 and 12 months after CO poisoning, we administered standardized questionnaires to assess functional outcome. At 6 months, we performed extensive neuropsychologic testing.

RESULTS

All four patients exhibited normal performance on a neuropsychologic test battery at 6 months. The Folstein Mini-Mental Status Examination was normal in all patients. All patients had normal functional outcomes.

CONCLUSION

Normal neuropsychologic and functional outcomes are possible after severe CO poisoning without the use of HBO therapy.

Severe anoxia with and without concomitant brain atrophy and neuropsychological impairments

Significant anoxia may cause a variety of neuropathologic changes as well as cognitive deficits. We have recently seen 3 patients who have suffered severe anoxic episodes all with initial Glasgow Coma Scores (GCS) of 3 with sustained coma for 10-14 d. All 3 patients had extended hospitalizations and rehabilitation therapy. A neuropsychological test battery was administered and volumetric analyses of MRI scans were carried out in each case at least 6 mo postinjury. Two of the patients display distinct residual cognitive and neuropathologic changes while 1 patient made a remarkable recovery without evidence of significant morphological abnormality. These three cases demonstrate, that even with similar admission GCS, the outcome is variable and the degree of neuropsychological impairment appears to match the degree of morphologic abnormalities demonstrated by quantitative MR image analysis. An important finding of this study is that even though subjects with an anoxic insult exhibit severe cognitive and memory impairments along with concomitant morphologic changes, their attention/concentration abilities appear to be preserved. MR morphometry provides an excellent means by which neural structural changes can be quantified and compared to neuropsychological and behavioral outcomes.

A decision support tool for antibiotic therapy

We developed a decision support tool to assist physicians anticipating the need for antibiotic therapy. The initial screen alerts physicians of pertinent patient information, provides direct access to other essential medical information, and stimulates clinical judgment by suggesting an antibiotic regimen. The decision support tool also suggests the dose and interval for any ordered antibiotics selected by the physicians. During a 7-month pilot study, all antibiotics for patients admitted to the Shock/Trauma/Respiratory Intensive Care Unit (STRICU) were ordered using the decision support tool. Clinical data from the study period and a 12-month control period (the previous year) were collected and compared. The decision support tool was used to order antibiotics 588 times during the study period and the suggested antibiotics were used 218 (37%) times. The computer suggested dosages were used over 90% of the time. The mean cost of antibiotics was $87.00 (p < 0.04) less per patient during the study period as compared to the control period. Prospective assessment revealed only 3 antibiotic adverse drug events (ADEs) (0.9%) among 336 study patients as compared to 15 ADEs (2.4%) among 626 control patients (p = 0.164).

Arterial oxygen tension of patients with abnormal lungs treated with hyperbaric oxygen is greater than predicted

The arterial oxygen (O2) tension (PaO2) of patients with normal gas exchange treated with hyperbaric oxygen (HBO2) can be predicted from their pre-HBO2 arterial to alveolar O2 tension ratio (a/A) which remains constant up to a PaO2 of 2,000 mm Hg. We observed that the a/A could not be used to predict the PaO2 of patients with impaired gas exchange (reduced pre-HBO2 a/As) treated with HBO2. Our study provides information about the PaO2 of patients with abnormal lungs treated with HBO2. For clinical reasons, we measured the PaO2 of 24 patients treated with HBO2. We obtained arterial blood gas values from patients with lung dysfunction (a/A < 0.75) prior to, during, and after HBO2. The pre-HBO2 a/A = 0.45 +/- 0.17 (mean +/- 1 SD). During HBO2 the a/A ranged from 0.7 to 0.8 depending on chamber pressure and returned to the pre-HBO2 baseline after HBO2. We conclude the following: (1) The hyperbaric PaO2s of patients with a/A < 0.75 is greater than expected. (2) However, the PaO2 is lower than in patients with normal lung function (a/A > 0.75). Possible explanations include improvement in ventilation/perfusion matching, reduction of venous admixture, and/or extra-alveolar uptake of O2. (3) Exposures to HBO2 treatment pressures greater than recommended by existing protocols may be required in patients with impaired transfer of O2 across the lung to achieve PaO2s similar to patients with normal lung function treated with HBO2.

Hypoxemia during hyperbaric oxygen therapy

This report describes a patient with mucormycosis treated with hyperbaric oxygen therapy (HBO2). Arterial O2 tension (PaO2) during HBO2 was considerably lower (346 mm Hg) than expected (1,500 mm Hg) due to an inadvertent right main-stem intubation, which was not otherwise clinically evident. This case illustrates the influence of a large right-to-left shunt (Qs/Qt) on O2 loading during HBO2. We raise the question if routine hyperbaric treatment protocols are adequate to raise PaO2 in patients with large Qs/Qts.

Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome

The impact of a new therapy that includes pressure-controlled inverse ratio ventilation followed by extracorporeal CO2 removal on the survival of patients with severe ARDS was evaluated in a randomized controlled clinical trial. Computerized protocols generated around-the-clock instructions for management of arterial oxygenation to assure equivalent intensity of care for patients randomized to the new therapy limb and those randomized to the control, mechanical ventilation limb. We randomized 40 patients with severe ARDS who met the ECMO entry criteria. The main outcome measure was survival at 30 days after randomization. Survival was not significantly different in the 19 mechanical ventilation (42%) and 21 new therapy (extracorporeal) (33%) patients (p = 0.8). All deaths occurred within 30 days of randomization. Overall patient survival was 38% (15 of 40) and was about four times that expected from historical data (p = 0.0002). Extracorporeal treatment group survival was not significantly different from other published survival rates after extracorporeal CO2 removal. Mechanical ventilation patient group survival was significantly higher than the 12% derived from published data (p = 0.0001). Protocols controlled care 86% of the time. Average PaO2 was 59 mm Hg in both treatment groups. Intensity of care required to maintain arterial oxygenation was similar in both groups (2.6 and 2.6 PEEP changes/day; 4.3 and 5.0 FIO2 changes/day). We conclude that there was no significant difference in survival between the mechanical ventilation and the extracorporeal CO2 removal groups. We do not recommend extracorporeal support as a therapy for ARDS. Extracorporeal support for ARDS should be restricted to controlled clinical trials.

Normobaric measurement of arterial oxygen tension in subjects exposed to hyperbaric oxygen

This study demonstrates the ability of an automated blood gas analyzer (Radiometer ABL 330) operated at atmospheric pressure to measure the arterial oxygen tension (PaO2) of ten healthy volunteers exposed to hyperbaric oxygen (HBO2) up to 3.0 atmospheres absolute. Arterial blood samples were aspirated from subjects compressed in a single-person hyperbaric chamber and were analyzed immediately in the blood gas analyzer. The subjects' values for PaO2 correlated with the calculated alveolar O2 tension (PAO2) (measured PaO2 = 0.827 x PAO2-15.1) (r2 = 0.97). Tonometric experiments indicated a difference between saline and blood PO2 measurements. We therefore derived a correction factor for blood measurements (corrected PaO2 = 0.908 x PAO2-52.4) (r2 = 0.98). These results compared favorably with PaO2 measurements made with blood gas analyzers calibrated inside walk-in hyperbaric chambers. We conclude that the PaO2 of normal subjects exposed to HBO2 can be measured accurately at atmospheric pressure with this automated blood gas analyzer. Prior to this study, hyperbaric PaO2 measurements could only be performed within walk-in chambers. Our observations generalize the normobaric measurement of hyperbaric PaO2 to patients treated in single-person and walk-in chambers.

The adult respiratory distress syndrome. A report of survival and modifying factors

The adult respiratory distress syndrome (ARDS) is a form of acute lung injury characterized by arterial hypoxemia, reduced thoracic compliance, normal pulmonary capillary wedge pressure, and diffuse infiltrates on chest roentgenograms. Mortality remains high and has been associated with sepsis, organ failure, age, and predisposing factors. We prospectively identified 215 ARDS patients over 34 months to examine how these factors influence outcome. One hundred two (47 percent) of 215 patients survived. Age 65 years or older was associated with a survival of 34 percent, which was statistically different from the 53 percent survival of those patients younger than 65 years (p = 0.02). Aspiration pneumonia as a predisposing factor of ARDS was associated with a better survival (p = 0.04). Survivors had statistically less organ failure and sepsis than did nonsurvivors (p less than 0.05). Cause of death was determined using the criteria of Montgomery et al for irreversible organ dysfunction. Forty-five (40 percent) of our patients died of respiratory failure (not sepsis). We conclude the following: (1) survival in our ARDS patients is different from previous reports; (2) the cause of death in our ARDS patients is different from that reported by Montgomery et al in 1985; and (3) multisystem organ failure, sepsis, age, and some predisposing factors of ARDS continue to be associated with decreased survival of ARDS patients.

A successful computerized protocol for clinical management of pressure control inverse ratio ventilation in ARDS patients

We have developed a computerized protocol that provides a systematic approach for management of pressure control-inverse ratio ventilation (PCIRV). The protocols were used for 1,466 h in ten around-the-clock PCIRV evaluations on seven patients with severe adult respiratory distress syndrome (ARDS). Patient therapy was controlled by protocol 95 percent of the time (1,396 of 1,466 h) and 90 percent of the protocol instructions (1,937 of 2,158) were followed by the clinical staff. Of the 221 protocol instructions, 88 (39 percent) not followed were due to invalid PEEPi measurements. Compared with preceding values during CPPV, the expired minute ventilation was reduced by 27 percent during PCIRV while maintaining a pH that was not clinically different (mean difference in pH = 0.02). There was no difference in the PaO2, PEEPi, or the FIO2 between PCIRV and CPPV. The PEEP setting was reduced by 33 percent from 9 +/- 0.05 to 6 +/- 0.6 and the I:E ratio increased from 0.64 +/- 0.04 to 2.3 +/- 0.10. Peak airway pressure was reduced by 24 percent (from 59 +/- 1.5 to 45 +/- 0.6) and mean airway pressure increased by 27 percent (from 22 +/- 0.8 to 28 +/- 0.6) in PCIRV. Right atrial and pulmonary artery pressures were higher and cardiac output lower in PCIRV but blood pressure was unchanged. The success of this protocol has demonstrated the feasibility of using PEEPi as a primary control variable for oxygenation. This computerized PCIRV protocol should make the future use of PCIRV less mystifying, simpler, and more systematic.

A strategy for development of computerized critical care decision support systems

It is not enough to merely manage medical information. It is difficult to justify the cost of hospital information systems (HIS) or intensive care unit (ICU) patient data management systems (PDMS) on this basis alone. The real benefit of an integrated HIS or PDMS is in decision support. Although there are a variety of HIS and ICU PDMS systems available there are few that provide ICU decision support. The HELP system at the LDS Hospital is an example of a HIS which provides decision support on many different levels. In the ICU there are decision support tools for antibiotic therapy, nutritional management, and management of mechanical ventilation. Computer protocols for the management of mechanical ventilation (respiratory evaluation, ventilation, oxygenation, weaning and extubation) in patients with adult respiratory distress syndrome ((ARDS) have already been developed and clinically validated at the LDS Hospital. These protocols utilize the bedside intensive care unit (ICU) computer terminal to prompt the clinical care team with therapeutic and diagnostic suggestions. The protocols (in paper flow diagram and computerized form) have been used for over 40,000 hours in more than 125 adult respiratory distress syndrome (ARDS) patients. The protocols controlled care for 94% of the time. The remainder of the time patient care was not protocol controlled was a result of the patient being in states not covered by current protocol logic (e.g. hemodynamic instability, or transport for X-Ray studies). 52 of these ARDS patients met extra corporal membrane oxygenation (ECMO) criteria. The survival of the ECMO criteria ARDS patients was 41%, four times that expected (9%) from historical data (p less than 0.0002).(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive Doppler blood pressure monitoring in the monoplace hyperbaric chamber

We describe a noninvasive method of monitoring blood pressure in the monoplace hyperbaric chamber. A standard blood pressure cuff was placed on the patient's arm. A Doppler probe, linked to an ultrasonic Doppler flow detector outside the chamber, was secured over the patient's radial artery. Cuff inflation tubing and the Doppler probe wires were passed into the chamber by modifying a standard disposable hyperbaric intravenous pass-through. Blood pressure readings were determined by inflating and slowly deflating the cuff from outside the chamber while observing the sphygmomanometer within the chamber and listening for the first audible flow signal from the Doppler detector, corresponding to the systolic blood pressure. To minimize the risk of fire in the oxygen-filled monoplace hyperbaric chamber, the patient, Doppler detector, and chamber were grounded. Doppler readings obtained from nine normal subjects whose arterial pressures were being measured with indwelling radial arterial catheters (approved as part of another study by the hospital's Investigational Review Board) compare closely with the subject's blood pressures measured with this noninvasive method: 114 +/- 7.6 mm Hg (mean +/- 1 SD) compared to 112 +/- 8.1 mm Hg, respectively (n = 92 measurements in 8 subjects). We conclude that this noninvasive method of monitoring blood pressure within the monoplace hyperbaric chamber is accurate and suitable for monoplace clinical purposes.

A computerized laboratory alerting system

A computerized laboratory alerting system (CLAS) has been developed as part of an ongoing effort to improve the quality of care at LDS Hospital. The system identifies potentially life-threatening conditions on the basis of laboratory findings and then generates appropriate warnings and transmits them to clinicians. Use of the system has led to a significant increase in the proportion of patients in life-threatening situations who have received appropriate care (50.8% before implementation vs. 62.5% afterward, P less than 0.05). Among patients with hypokalemia, falling potassium levels, hyperkalemia, hypokalemia during treatment with digoxin, hyponatremia, falling sodium levels, hypernatremia, hypoglycemia, or hyperglycemia, the average length of time spent in the life-threatening situation has decreased from 30.4 to 15.7 hours (P less than 0.05) and the average length of stay has decreased from 14.6 to 8.8 days (P less than 0.05). There has been little change in the proportion of patients with findings indicating metabolic acidosis who have received appropriate care (32.3 vs. 34.6%). We conclude that CLAS has an important role in patient care at our hospital.

Bilateral otorrhagia associated with continuous positive airway pressure

A patient had bilateral tympanic membrane rupture and otorrhagia, an unusual complication of continuous positive airway pressure (CPAP). CPAP, applied by a bag/mask system using disposable spring valves, was used to treat acute pulmonary edema during volume resuscitation and vasopressin therapy for bleeding from esophageal varices.

Phenytoin sodium in oxygen-toxicity-induced seizures

A case of cerebral air embolism complicated by oxygen-induced seizures in the hyperbaric environment is presented. Phenytoin sodium (Dilantin) was used during recompression treatment in an attempt to suppress the occurrence of seizure activity. It appeared to inhibit seizure activity, subsequently allowing the patient to be treated with hyperbaric oxygen.