NONINVASIVE VENTILATION MAY IMPROVE COGNITION, QUALITY OF LIFE IN ALS PATIENTS

The cognitive deficits that some patients with amyotrophic lateral sclerosis (ALS) experience may be improved by noninvasive positive pressure ventilation. Although noninvasive positive pressure ventilation has been used for over a decade to treat sleep-related respiratory problems in patients with neuromuscular disease, its impact on cognition has only recently been investigated.

Respiratory muscle weakness in patients with ALS can lead to nocturnal hypoventilation, resulting in sleep disturbance and daytime somnolence, which occurs in as many as 44% of patients. It is suspected that this type of sleep deprivation may cause impairments in cognitive function—most notably memory and such executive functions as verbal fluency and visual attention.

A prospective study evaluated cognitive functioning in nine patients with ALS who had sleep disturbances caused by nocturnal hypoventilation and in a control group of ALS patients without hypoventilation. After six weeks of night treatment with noninvasive positive pressure ventilation, the ALS patients with sleep disturbances demonstrated significantly improved scores on two of seven cognitive tests, and showed a trend toward significant improvement for two other tests—improvements not seen in the control group.

Although the researchers acknowledge that nocturnal hypoventilation is not completely responsible for the cognitive deficits found in non-demented ALS patients, it is possible that respiratory difficulties may exacerbate cognitive impairment. Such impairment may also be a factor contributing to the decline in quality of life reported by ALS patients with hypoventilation.

The authors suggested that a large, randomized controlled study be conducted to test the hypothesis that the cognitive deficits are caused by impaired nocturnal ventilation and sleep disturbance in ALS, and that these deficits could be improved by use of noninvasive positive pressure ventilation.

Newsom-Davis IC, Lyall RA, Leigh PN, et al. The effect of non-invasive positive pressure ventilation (NIPPV) on cognitive function in amyotrophic lateral sclerosis (ALS): a prospective study. J Neurol Neurosurg Psychiatry. 2001;71:482-487.

HIGH–NORMAL BLOOD PRESSURE INCREASES HEART DISEASE RISK

High-normal blood pressure raises the risk of cardiovascular disease. Marked by systolic pressure between 130 and 139 mm Hg, which may or may not be coupled with diastolic pressure between 85 and 89 mm Hg, high-normal blood pressure increases a patient’s risk of stroke, congestive heart failure (CHF), and myocardial infarction (MI), and of dying of cardiovascular disease.

Vasan et al followed up on 6,859 patients in the Framingham Heart Study, none of whom had hypertension at baseline. The authors observed the incidence of stroke, CHF, MI, and death during 12-year follow-up. These subjects were categorized based on blood pressure at baseline: optimal (systolic, < 120 mm Hg, and diastolic, < 80 mm Hg), normal (systolic, 120-129 mm Hg, or diastolic, 80-84 mm Hg), or high-normal (systolic, 130-139 mm Hg, or diastolic, 85-89 mm Hg).

The researchers found that patients with high-normal blood pressure were older than those with optimal blood pressure, and they had higher body mass indices and serum cholesterol levels. Furthermore, the risk-factor–adjusted hazard ratio for patients with high-normal blood pressure (compared with those who had optimal blood pressure) was 1.6 among men and 2.5 among women. Normal blood pressure, when compared with optimal blood pressure, was associated with a hazard ratio of 1.3 among men and 1.5 among women.

Vasan et al cited previous work indicating that high-normal blood pressure has been associated with thickening of the carotid intima and media, alterations in cardiac morphology, and diastolic ventricular dysfunction. They suggested that their research outlined a need for further investigation of the benefits that decreases in high-normal blood pressure would deliver to high-risk patients, such as those with diabetes or the elderly.

Vasan RS, Larson MG, Leip EP, et al. Impact of high-normal blood pressure on the risk of cardiovascular disease. N Engl J Med. 2001;345:1291-1297.

DO LAB RESULTS VARY DEPENDING ON HOW VENOUS SAMPLES ARE OBTAINED?

Although venipuncture and aspiration from a peripheral venous catheter generally produce blood samples of similar quality from patients who appear healthy, venipuncture may be a more reliable means of obtaining samples when glucose, potassium, or bicarbonate measurements are needed.

Zlotowski et al evaluated 32 volunteers from the emergency department staff of a tertiary care teaching hospital. Subjects served as their own controls; venipuncture and withdrawal of a blood sample were performed on one upper extremity while a peripheral catheter was concurrently placed in the other. Through the peripheral catheter, subjects received a 200-mL bolus of normal saline solution during a 10-minute period. Following a two-minute waiting period, a 12-mL aspirate was taken through the saline solution lock. A second withdrawal of 12 mL through the lock followed.

These three samples were evaluated for 19 laboratory values, including complete blood count; electrolyte, blood urea nitrogen, creatinine, and glucose measurements; liver function tests; and prothrombin time/international normalized ratio. The results obtained with the venipuncture sample were compared with those derived from the first and second aspirates.

The researchers noted that the first catheter aspirate could have been tainted by the normal saline in the catheter itself or affected by the infusion’s dilution of venous blood. Nevertheless, 16 of the 19 laboratory values were clinically equivalent (defined as having 99% agreement) in all three samples. However, the venipuncture sample produced different results for potassium, bicarbonate, and glucose than did either of the aspirates.

Zlotowski SJ, Kupas DF, Wood GC. Comparison of laboratory values obtained by means of routine venipuncture versus peripheral intravenous catheter after a normal saline solution bolus. Ann Emerg Med. 2001;38:497-504.

MITIGATING RISK FACTORS FOR PNEUMONIA IN LONG-TERM CARE

Patients in long-term care facilities who experience just one episode of pneumonia may face an increased risk of recurrent pneumonia and death for as long as two years after the event. However, it may be possible to mitigate at least two of the factors that increase these patients’ pneumonia risk: large-volume aspiration and tranquilizer use.

Vergis et al studied 104 patients who had developed pneumonia two days to one year after admission to a Veterans Affairs facility. Each patient was matched with a control based on age, levels of nursing care required, admission date, and dependence in activities of daily living. All subjects were followed up for two years or until death or discharge.

Fourteen-day mortality was 23% among the case patients and 0% among the controls. Mortality remained significantly higher in the case patients throughout most of the study; only at the end of the two years did mortality in the controls begin to approach that in the other group. During follow-up, pneumonia developed in 25% of the case patients and in 9% of the controls.

At the time of study entry, case patients were more likely than controls to have been fed enterally and to have pressure sores. They were also more likely than controls to have received tranquilizers, to have been physically restrained, and to have experienced an aspiration event during the 14 days before pneumonia onset. However, only receipt of tranquilizers and witnessed aspiration were identified as independent risk factors.

The researchers stated that although other risk factors for pneumonia had been identified in previous studies, those factors were not modifiable. But the two risk factors detected in this study are. The researchers suggested that many episodes of overt aspiration could be prevented; they proposed the use of a formal swallowing evaluation that could help identify a feeding prescription best suited to at-risk patients. The researchers also suggested that physicians could mitigate the risk associated with tranquilizers by using alternative management practices for anxiety and disruptive behavior.

Vergis EN, Brennen C, Wagener M, Muder RR. Pneumonia in long-term care: a prospective case-control study of risk factors and impact on survival. Arch Intern Med. 2001;161:2378-2381.

NEW MEANS OF PREDICTING ICU OUTCOMES

The recently developed sequential organ failure assessment (SOFA) scale offers physicians an alternative to other prediction models in anticipating morbidity and mortality in critically ill patients. A recent epidemiological study demonstrated that unlike SOFA, such current models as APACHE (Acute Physiology and Chronic Health Evaluation), SAPS (Simplified Acute Physiology Score), and MPM (mortality probability models) accounted for information relating only to a patient’s first 24 hours in the intensive care unit (ICU), and thus they ignored the dynamic nature of many of the factors that affect clinical outcomes.

Ferreira et al examined 352 patients admitted to a medicosurgical ICU during a four-month period. All patients remained in the ICU for more than 24 hours. The researchers collected demographic, laboratory, and clinical data to calculate each patient’s SOFA score within a scale of 0 to 24. Scores were assigned upon admission and every 48 hours thereafter until discharge; the specific values used to calculate SOFA score were derived from the worst values obtained in six measurements (PaO2/FiO2, platelet count, bilirubin level, blood pressure, Glasgow Coma Scale, and urine output or creatinine concentration) during a 24-hour period.

The researchers found that an initial SOFA score of up to 9 predicted mortality of less than 33%, whereas an initial score higher than 11 predicted mortality of 95%. However, subsequently obtained scores were also helpful in assessing outcome. When patients’ highest scores reached 10 (at any time during their ICU stay), their mortality rate approached 40%; when their highest scores were above 11, their average mortality rates reached 80%. Results for mean SOFA scores during the ICU stay were similar.

Ferreira et al concluded that the ability of the SOFA score to account for the dynamics of illness, as well as for the effects of therapy, made it a more valuable predictive tool than scales that assessed patient condition at ICU admission alone.

Ferreira F, Bota D, Bross A, et al. Serial evaluation of the SOFA score to predict outcome in critically ill patients. JAMA. 2001:286;1754-1758.