Accuracy of base excess--an in vitro evaluation of the Van Slyke equation

OBJECTIVES

To evaluate the precision, bias and CO2 invariance of base excess as determined by the Van Slyke equation over a wide P(CO2) range at normal and low hemoglobin concentrations.

DESIGN

Prospective in vitro study.

SETTING

University research laboratory.

SUBJECTS

Normal human blood, both undiluted and diluted with plasma.

INTERVENTIONS

Two experiments were conducted. In the first, blood unmodified or after adding HCl or sodium bicarbonate was rendered hypercarbic (P(CO2) >70 torr) by gas equilibration. Rapid Pco2 reduction in > or =10 steps to a final P(CO2) < or =20 torr was then performed. In the second experiment, blood unmodified or diluted to a hemoglobin concentration of approximately 4 G% was mixed anaerobically (9:1, vol:vol) with varying concentrations of lactic acid in saline (0-250 mmol/L).

MEASUREMENTS AND MAIN RESULTS

In the first experiment, blood gas analysis at each step during the progressive P(CO2) reduction revealed that base excess remained nearly constant (SD all specimens < or =0.6 mmol/L) whereas P(CO2) changed by >80 torr. In the second experiment, simultaneous blood gas and plasma lactate analyses showed that changes in base excess correlated closely with changes in both plasma and whole blood lactate concentrations (r2 > or = 0.91) despite concurrent P(CO2) elevations as great as 200 torr. Quantification by base excess of change in whole blood lactate concentration was precise with slight negative bias (mean negative bias, 1.1+/-1.9 mmol/L) in both diluted and undiluted blood. There was significant underestimation of change in plasma lactate concentration in undiluted blood, presumably because base excess is a whole blood variable.

CONCLUSIONS

Base excess calculated using the Van Slyke equation accurately quantifies metabolic (nonrespiratory) acid-base status in blood in vitro. This accuracy is little affected by large simultaneous alterations in P(CO2), or by very low hemoglobin concentrations similar to that used to calculate standard base excess.

Neighborhood poverty as a predictor of intimate partner violence among White, Black, and Hispanic couples in the United States: a multilevel analysis

PURPOSE

This study assessed the contribution of neighborhood poverty, measured at the census tract level, to the risk of male-to-female and female-to-male partner violence (MFPV, FMPV) among white, black, and Hispanic couples in the United States.

METHODS

As part of the 1995 National Alcohol Survey, a representative sample of married/cohabiting couples was obtained through a multistage, multicluster household probability sampling frame. The outcome variables, MFPV and FMPV, were measured through the Conflict Tactics Scale, Form R. Sociodemographic, psychosocial, and alcohol consumption covariates that were statistically significant through bivariate analysis were retained as individual-level predictors. Neighborhood poverty, indicating residence in a census tract where greater than 20% of the population lived below the Federal poverty line, was assessed by appending 1990 Census data to the primary data set. Multilevel logistic regression models were constructed, with separate analyses performed for each outcome (MFPV, FMPV) among the white, black, and Hispanic couples.

RESULTS

Couples residing in impoverished neighborhoods are at increased risk for both MFPV and FMPV. The association between residence in an impoverished neighborhood and MFPV was statistically significant for black couples (Odds Ratio [OR] 2.87; 95% Confidence Interval [CI] 1.36, 6.07). The association between residence in an impoverished neighborhood and FMPV was statistically significant for black couples and white couples.

CONCLUSIONS

Characteristics of the socioenvironment, such as neighborhood poverty, are associated with the risk of partner violence, particularly among black couples. Policies aimed at reducing community poverty may contribute to effective partner violence prevention strategies.

Preliminary evidence of an association between increased REM density and poor antidepressant response to partial sleep deprivation

BACKGROUND

One night of total sleep deprivation or of late-night partial sleep deprivation (PSD) produces a temporary remission in approximately 40-60% of patients with major depressive disorder; however, little is known about polysomnography (PSG) characteristics of responders to these types of sleep deprivation (SD).

METHODS

Twenty-three unmedicated unipolar patients (17-item Hamilton Depression Rating Scale (HDRS17) >16) and 14 normal controls underwent 1 night of late-night PSD (awake after 3 a.m.) Subjects underwent baseline PSG and received the HDRS17 at standard times before and after PSD. Clinical response was defined as a reduction of >30% in the modified HDRS17 (omitting sleep and weight loss items) following PSD.

RESULTS

The 12 responders and 11 nonresponders did not differ from each other significantly on baseline HDRS17 or PSG variables. The only PSG variable correlating with percent decrease in modified HDRS17 was baseline REM density (Pearson's r=-0.52, n=23, P=0.01.) In other words, the lower the baseline REM density, the more robust the antidepressant response was.

LIMITATIONS

Subject numbers are relatively small.

CONCLUSIONS

Increased REM density, which reflects the number of rapid eye movements per epoch of REM sleep, may be a physiological marker for severity or poor prognosis in a variety of psychiatric disorders, including relapse in recovering alcoholics, suicidality in schizophrenia, and poor response to PSD or interpersonal psychotherapy in depression.

Epidemiologic typing of Salmonella enterica serotype enteritidis in a Canada-wide outbreak of gastroenteritis due to contaminated cheese

A major Canada-wide outbreak of gastroenteritis due to Salmonella enterica serotype Enteritidis phage type (PT) 8 occurred in 1998, and this was traced to contaminated cheese in a commercial lunch pack product. Phage typing and pulsed-field gel electrophoresis linked the clinical and cheese isolates of serotype Enteritidis but failed to differentiate outbreak from nonoutbreak PT 8 strains. Further differentiation was made by biotyping based on melibiose fermentation.

Nonoperative management of dens fracture nonunion in elderly patients without myelopathy

STUDY DESIGN

A retrospective review of elderly patients treated without surgery for chronic mobile nonunions of the odontoid process. Patients were observed on an annual basis with clinical examinations and flexion/extensions plain film radiographs.

OBJECTIVES

To evaluate the clinical and radiographic results of elderly patients without myelopathy treated without surgery for dens fracture nonunion.

SUMMARY OF BACKGROUND DATA

Because of the risk of progressive myelopathy or sudden neurologic injury, many surgeons recommend operative stabilization for patients with mobile dens nonunions who are able to withstand an operation. There is, however, a lack of information about the radiographic and neurologic progression of dens nonunions. Although a less aggressive surgical approach has been recommended by some authors for elderly or medically compromised patients with acute fractures, long-term follow-up evaluation of patients with resulting nonunions has not been reported.

METHODS

A series of elderly patients with chronic, unstable, dens nonunions without myelopathy were treated with a nonoperative treatment protocol. Patients were informed of the nature of their lesion, including the risk of acute or chronic spinal cord injury and the options for operative treatment. Patients were evaluated yearly for clinical and radiographic progression. No intervention to slow progression of atlantoaxial instability was undertaken.

RESULTS

None of the patients developed myelopathic symptoms during the follow-up period, and no patient experienced more than a 1 mm radiographic increase in atlantoaxial excursion. None of the reported patients had less than 14 mm available for the spinal cord in either flexion or extension at the start of clinical monitoring.

CONCLUSIONS

Although further follow-up evaluation is needed, the authors believe on the basis of this review that this treatment protocol may be considered for patients who are poor candidates for surgical fusion.

Narrowband TL-01 phototherapy for patch-stage mycosis fungoides

BACKGROUND

Although patch-stage mycosis fungoides (MF) has a generally good prognosis, and long-term survival rates with current therapies (UV-B, photochemotherapy, topical nitrogen mustards, electron-beam therapy) are similar, there is concern regarding their potential adverse effects. Narrowband or TL-01 UV-B phototherapy (311 nm), in use for more than 10 years, is more effective than broadband UV-B for the treatment of psoriasis, with an efficacy approaching that of psoralen UV-A. This open study assesses TL-01 as an alternative therapy for patch-stage MF.

OBSERVATIONS

Eight white patients (4 men, 4 women; age range, 66-83 years) with histologically proven patch-stage MF received TL-01 phototherapy 3 times weekly using a standard protocol. Complete clearance of MF was achieved in 6 cases in a mean of 9 weeks or 26 treatments (range, 20-37 weeks) and 4 patients have had prolonged remissions. Mean duration of clinical improvement has been 20 months (range, 11-40 months). Partial response to TL-01 or poor histologic improvement was associated with rapid relapse.

CONCLUSIONS

TL-01 is an effective, convenient therapy that may have less risk of long-term adverse effects than current alternatives. Although larger prospective studies are necessary, for some patients intermittent courses of TL-01 may offer effective long-term therapy.

Bronchopulmonary and mediastinal leishmaniasis: an unusual clinical presentation of Leishmania donovani infection

We describe a case of unusual leishmaniasis in a Sudanese man with a history of progressively enlarging granulomatous mediastinal lymphadenopathy, worsening hemoptysis, and an intense mucosal granulomatous inflammatory response in the large bronchi. Leishmania donovani DNA was detected in bronchial biopsies by polymerase chain reaction. This is a novel description of human leishmanial infection in an immunocompetent patient involving this anatomical site. The patient's condition improved clinically, spirometrically, and radiologically after a course of treatment with amphotericin B. The cell-mediated immune response was analyzed before, during, and after successful antileishmanial chemotherapy.

Cultural diversity and transcultural nursing as they impact health care

This article examines and critiques what can be broadly defined as "culturally sensitive nursing practice." The authors argue that both past and present research on culturally sensitive nursing practice, regardless of which branch of such practice it subscribes to (transcultural, cross-cultural, multicultural, intercultural, international, and so forth), is not sufficiently based in a sociopolitical context. As a result, there is not significant positive improvement in health care outcomes for patients from traditionally under-represented social membership groups (i.e., groups based on race, gender, socioeconomic class, etc.). Realizing sincere and affective culturally sensitive nursing practice is contingent upon the development and implementation of a comprehensive, sociopolitically conceptualized multicultural nursing education curriculum and pedagogy.

Computerized left ventricular pressure-volume relationships (pV-loops) using disposable angiographic tip transducer pigtail catheters

Left ventricular pressure-volume relationships expressed as pV loops could yield important hemodynamic information in the cardiac catheterization laboratory. Many clinical situations might benefit from a quantitative assessment of left ventricular function. Potential applications of pV loops include the assessment of vasoactive and inotropic drugs, balloon valvuloplasty, coronary angioplasty, and surgical treatment of valvular heart disease. For many years the clinical use of pV loops has been hindered by logistical difficulties. The ability to merge on-line concurrent digital imaging data for computation of left ventricular volume and digital left ventricular pressure wave forms obtained from high fidelity tip-transducer angiocatheters has allowed us to develop a technique which can generate pV loops during cardiac catheterization procedures. The method offers an automated measurement of left ventricular volume independent of edge detection or an interactive technique for tracing endocardial borders by a trained operator. Illustrative case studies are included to demonstrate the potential of the method during ventricular angiographic procedures. Implementation and computational time requirements of the method are discussed. The concept and the value of pV loop generation to study left ventricular performance has been known for many years. Combining digital imaging and digital physiologic data obtained with disposable tip-transducer angiocatheters with modern networking technology, the technique can more easily be applied to catheterization procedures and could enhance invasive hemodynamic assessment of left ventricular function.

Comparison of flow in numerical and physical models of a ventricular assist device using low- and high-viscosity fluids

The flows in a model of a ventricular assist device (VAD) were investigated numerically and experimentally for two different Newtonian test fluids. These were a blood analogue fluid and a much higher viscosity fluid. A finite volume method was employed to solve the governing equations for a three-dimensional unsteady laminar flow on a transient grid. The numerical solutions were compared with experimental results from an identical physical model. The experimental flows were investigated by flow visualization and by laser Doppler velocity measurements at selected points in the flow field. The validation was based on comparisons of flow patterns and of non-component velocity-time histories. The maximum Reynolds numbers in the inflow tube of the model VAD were approximately 460 and 3300 using the high- and low-viscosity fluids respectively. The investigation showed that the flow patterns were better predicted for the high-viscosity fluid. However, the agreement between the velocity-time histories was found to be slightly better for the low-viscosity fluid. The discrepancies in the flow patterns may be due to intermittent turbulence with a further contribution from numerical diffusion.

Artifactual elevation of measured plasma L-lactate concentration in the presence of glycolate

OBJECTIVES

To determine whether glycolate, a toxic metabolite of ethylene glycol that is chemically similar to lactate, can cause artifactual elevation of measured L-lactate concentrations.

DESIGN

Prospective in vitro study.

SETTING

Intensive care unit and chemical pathology laboratory in a university-affiliated hospital.

SUBJECTS

Heparinized normal human blood and four commercially available L-lactate analyzers.

INTERVENTIONS

Four analyzers were tested, three of which used L-lactate oxidase and one of which used L-lactate dehydrogenase. Glycolic acid (10 g/L) in saline was added to blood in a series of aliquots. Corresponding plasma L-lactate concentrations and blood pH, PCO2, and hemoglobin concentrations were measured and base excess was calculated initially and after the addition of each aliquot. One of the two L-lactate oxidase-type analyzers, which was found to show interference, was then used to measure plasma L-lactate and glucose concentrations in blood with glycolic, oxalic, or formic acid added until the base excess was reduced by >15 mmol/L.

MEASUREMENTS AND MAIN RESULTS

Artifactual plasma L-lactate elevations were observed in two analyzers, both of the L-lactate oxidase type. Small concentrations of glycolic acid (causing reductions of base excess of 2-5 mmol/L) were accompanied by artifactual plasma L-lactate elevations of 4-8 mmol/L. Artifactual plasma L-lactate elevations increased with further glycolic acid-induced reductions in base excess. Oxalate and formate did not interfere with plasma L-lactate measurements, and measured plasma glucose concentrations were unaffected by all three acids.

CONCLUSIONS

Glycolate causes large artifactual elevations in plasma L-lactate measurements by two analyzers in common use, with potential for misdiagnosis of lactic acidosis in ethylene glycol poisoning. A possible cause of the interference is incomplete specificity of the analytical reagent L-lactate oxidase, allowing cross-reaction with glycolate.

The pre-operative ECG in day surgery: a habit?

As the population presenting for day-case surgery and anaesthesia increases, so does the challenge of adequate pre-operative assessment. Although an electrocardiogram is frequently performed, its value in day-case surgery remains unproven. One thousand, one hundred and eighty-five patients presenting for day-case surgery were assessed. One hundred and fifty-four (13%) were referred for electrocardiogram according to well-recognised criteria for the prediction of coronary artery disease. They were read independently by the anaesthetist responsible for the case and by an experienced cardiologist. A significant abnormality was noted in 26% of electrocardiograms, most frequently in patients referred with hypertension. There was a good correlation between the reports of the anaesthetist and cardiologist. Only 20% of those patients with an abnormal electrocardiogram had their surgery postponed. No adverse events occurred in patients proceeding to surgery despite the abnormalities. We conclude that a resting electrocardiogram is of limited value in risk stratification of patients undergoing day-case surgery.

Novel PCR-based diagnostic tools for Charcot-Marie-Tooth type 1A and hereditary neuropathy with liability to pressure palsies

The majority of cases of Charcot-Marie-Tooth type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are the result of DNA duplications and deletions respectively of a 1.5 Mb region on 17p11.2. The region contains the peripheral myelin protein 22 gene (PMP-22) and is flanked by homologous proximal and distal CMT1A-REP elements. The majority of duplications and deletions arise during meiotic recombination following misalignment and unequal crossing-over between the proximal and distal CMT1A-REP elements. The cross-over breakpoints are most frequently located within a 1.7 Kb hotspot of recombination and produce novel duplication or deletion junctional CMT1A-REPs with unique restriction patterns. Here we describe the use of PCR based tests, which amplify a 3.6 Kb region including the 1.7 Kb hotspot from specific CMT1A-REPs, for the rapid diagnosis of CMT1A and HNPP patients. In an analysis of 96 CMT1A and 30 HNPP patients, duplication and deletion events were detected in all samples with cross-over breakpoints known to be within the region amplified by PCR.

The identification of three biologically relevant globotriaosyl ceramide receptor binding sites on the Verotoxin 1 B subunit

The Verotoxin 1 (VT1) B subunit binds to the glycosphingolipid receptor globotriaosylceramide (Gb3). Receptor-binding specificity is associated with the terminally linked Galalpha(1-4) Galbeta disaccharide sequence of the receptor. Recently, three globotriose (Galalpha[1-4] Galbeta [1-4] Glcbeta) binding sites per B-subunit monomer were identified by crystallography. Two of these sites (sites I and II) are located adjacent to phenylalanine-30. Site I was originally predicted as a potential Gb3 binding site on the basis of sequence conservation, and site II was additionally predicted based on computer modelling and receptor docking. The third (site III) was also identified by crystallography and is located at the N-terminal end of the alpha-helix. To determine the biological significance of sites II and III, and to support our previous findings of the significance of site I, we examined the binding properties and cytotoxicity of VT1 mutants designed to block Gb3 binding at each site selectively. The Scatchard analysis of saturation-binding data for each mutant revealed that only the amino acid substitutions predicted to affect site I (D-17E) or site II (G-62T) caused reductions in the binding affinity and capacity of VT1 for Gb3. Similarly, those mutations at sites I and II also caused significant reductions in both Vero and MRC-5 cell cytotoxicity (by seven and five logs, respectively, for G-62T and by four and two logs, respectively, for D-17E). In contrast, the substitution of alanine for W-34 at site III did not reduce the high-affinity binding of the B subunit, despite causing a fourfold reduction in the receptor-binding capacity. The corresponding mutant W-34A holotoxin had a two-log reduction in cytotoxicity on Vero cells and no statistically significant reduction on MRC-5 cells. We conclude that the high-affinity receptor binding most relevant for cell cytotoxicity occurs at sites I and II. In contrast, site III appears to mediate the recognition of additional Gb3 receptor epitopes but with lower affinity. Our results support the significance of the indole ring of W-34 for binding at this site.

Reducing the burden of diabetes: managing cardiovascular disease

Of the threats to health and life that beset the person with diabetes, cardiovascular disease (CVD), particularly coronary heart disease (CHD) but also cerebrovascular and peripheral vascular disease, represent the heaviest burden. The relative risk for CVD is very high for Type 1 diabetes, but the absolute risk, in terms of numbers, is much higher for Type 2. In all societies, diabetes increases cardiovascular risk twofold or more, compared with the local non-diabetic population. Some of the evidence for this diabetes-related increase in cardiovascular risk is reviewed and its relationship to recognised cardiovascular risk factors considered. The explanation of the enhanced susceptibility to atherosclerotic disease in diabetes remains a matter of contention. How much can be explained by greater prevalence in diabetes of such risk factors as hypertension and dyslipidaemia? To what extent is the impact of a given level of risk factor magnified by a co-existing diabetic state? Is the increased cardiovascular morbidity and mortality secondary to risk factors specifically related to the diabetic state itself? Does the explanation lie in altered coagulability due to changes in platelet activation and aggregability, fibrinogen levels, Factor VII, von Willebrand factor or PAI-1, in the concentration or composition of plasma lipoproteins, in defective endothelial cell function or other metabolic abnormalities of the arterial wall? To what extent is cardiovascular risk related to the degree of hyperglycaemia, protein glycation, relative hyperinsulinaemia and insulin resistance? Data from recent epidemiological, intervention and laboratory investigations bearing on causation, management and prevention of CVD in diabetes are reviewed. Evidence for the impact of correction of glycaemia, dyslipidaemia and raised arterial pressure is considered and reasons are adduced for a broad and proactive therapeutic approach with early identification and vigorous correction of key risk factors.

Methodological issues in performance improvement in integrated systems

This article presents an overview of processes necessary for effective performance improvement (PI) projects and includes a discussion of methodological issues that affect the quality of PI projects. Issues related to project design, project purpose, selection of a representative population for the project, and issues of sampling are presented. Data collection methods and instruments are analyzed and issues related to connecting the problem, the intervention, and the outcome are described. The final sections address strategies related to data analysis procedures and interpretation.

Baylor profound mental status examination: a brief staging measure for profoundly demented Alzheimer disease patients

There is no brief patient-derived rating scale for staging and following profoundly demented Alzheimer disease (AD) patients. We developed the Baylor Profound Mental Status Examination (BPMSE) modeled after the Mini-Mental State Examination (MMSE) to meet this need. The BPMSE consists of 25 cognitive questions that assess orientation, language, attention, and motor functioning; 10 examiner ratings of presence or absence of problem behaviors; and 2 qualitative observations of language and social interaction. Two hundred eight probable or possible AD patients (MMSE scores of 20 or less) received the BPMSE. Some were also rated on the clinical dementia rating (CDR) and Lawton activities of daily living (ADL). A ceiling effect occurred at MMSE scores above 11. BPMSE cognitive scores and MMSE scores correlated significantly (r = 0.76, p < 0.0001). Subareas of the BPMSE also intercorrelated significantly. The BPMSE correlated with both CDR and ADL scores (p < 0.001). Internal consistency, interrater reliability, and test-retest stability were excellent. There was no floor effect, and BPMSE scores continued to decline after the MMSE reached 0. The BPMSE is a quick and easy staging tool with excellent validity and test-retest stability that measures cognitive function successfully in patients with MMSE scores below 12. The scale is sensitive to longitudinal change and continues to assess decline when performance has reached the lowest levels on conventional measures.

Effect of timing and route of administration of furosemide on pulmonary hemorrhage and pulmonary arterial pressure in exercising thoroughbred racehorses

OBJECTIVES

To examine effect of pre-exercise administration of furosemide (FUR) on mean pulmonary arterial pressure (PAP) during work and RBC concentration in bronchoalveolar lavage fluid (BALF) collected 40 minutes after exercise.

ANIMALS

10 adult Thoroughbreds.

PROCEDURE

A modified 10 X 10 crossover design comprising 10 horses during 10 weeks was used. Each horse received each of 5 treatments twice. Treatment structure included a control plus a 2 X 2 factorial and consisted of the following: A, control; B, FUR, 250 mg, IV, 30 minutes before exercise; C, FUR, 250 mg, IV, 240 minutes before exercise; D, FUR, 250 mg, nebulized, 30 minutes before exercise; and E, FUR, 250 mg, nebulized, 240 minutes before exercise. Mean PAP data were collected, and each horse, after a 500-m warm-up, was galloped at maximal speed for 1,600 m. BALF RBC concentration was determined by hemocytometer.

RESULTS

Interaction between treatment method and time of administration was significant (P = 0.04). Treatment B resulted in significantly (P = 0.01) lower BALF RBC concentration than did treatment C. Only BALF RBC count after treatment B was significantly lower than the control value. Horses that received FUR IV had significantly lower peak mean PAP than did those that received the drug by nebulization, regardless of administration time. Only treatment B resulted in peak mean PAP that was significantly lower than that of control. Exercise time was not influenced by treatment.

CONCLUSIONS

FUR, administered IV 30 minutes before exercise, significantly reduced peak mean PAP and BALF RBC concentration.

Investigation of unsteady flow in a model of a ventricular assist device by numerical modelling and comparison with experiment

Prior to this study, a clinical prototype of a sac-type ventricular assist device (VAD) was investigated experimentally, using both flow visualisation and Laser Doppler anemometry (LDA), in order to optimise its geometry. As poor optical access precluded the experimental investigation of the flow in some areas of the prototype VAD, computational fluid dynamics (CFD) was used in the present work. Flow patterns during one full pumping cycle were investigated in a simplified model of the VAD. The numerical solutions were compared with experimental results from an identical physical model. The model consists of the hemispherical cylinder and two attached tubes for the inflow and outflow. Instead of a diaphragm in the clinical device, which deforms non-uniformly during pumping, a piston with a matching hemispherical crown was used. A finite volume method was employed to solve the governing equations for the three-dimensional, unsteady, laminar flow of an incompressible, Newtonian fluid. The general flow features were predicted very well by the simulation, with some differences in the details of the flow structures. This allows the conclusion that CFD can be used to facilitate improvement of the design of the clinical device. The comparison of one-component velocity time histories at selected points showed that the predicted velocities were approximately 20-50% lower than those measured by LDA. Such underprediction would lead to erroneous results for particle residence times and may result in an underestimation of wall shear stresses.

Is there a relationship between delta sleep at night and afternoon cerebral blood flow, assessed by HMPAO-SPECT in depressed patients and normal control subjects? Preliminary data

We wished to explore the relationships between waking HMPAO uptake and visually scored polysomnography. We hypothesized that HMPAO activity would correlate positively with slow wave sleep measures the same night. Eight unmedicated unipolar patients with current DSM-IV major depression (17-item Hamilton Depression Rating Scale score 21.5+/-2.9) and seven control subjects received polysomnography on 2 consecutive nights. On the afternoon following the adaptation night, subjects received cerebral SPECT, with 15 mCi Tc-99m-HMPAO injected while subjects performed the Continuous Performance Task. Patients and control subjects did not significantly differ on demographic, polysomnographic, and SPECT variables. Slow wave sleep measures correlated positively (Spearman's) with global and regional tracer activity for depressed (n = 8), control (n = 7) and combined groups (n = 15); in other words, the greater the global or regional afternoon HMPAO uptake, the greater the slow wave sleep measures were the same night. In addition, the greater the waking afternoon global or regional HMPAO activity, the faster subjects fell asleep and the less Stage 2% they had. In patients, global and regional HMPAO activity correlated positively with REM density. Positive correlations between waking tracer activity and subsequent slow wave measures are consistent with previous hypotheses linking slow wave sleep with brain energy conservation and restoration. Further study is needed to determine whether these functional relationships differ in depression.