PubMed Health⌕ Search

Biomedical subjects

Daniel J Johnson

Publications and source records attributed to Daniel J Johnson.

12 recordsLinked to original sources
PubMed2006

Quantification of particle-bubble interactions using atomic force microscopy: A review.

The attachment of particles to bubbles in solution is of fundamental importance to several industrial processes, most notably in the process of froth flotation. During this process hydrophobic particles attach to air bubbles in solution, which allows them to be separated as froth at the surface. The addition of chemicals can help to modulate these interactions to increase the yield of the minerals of interest. Over the past decade the atomic force microscope (AFM) has been adapted for use in studying the forces involved in the attachment of single particles to bubbles in the laboratory. This allows the measurement of actual DLVO (Derjaguin, Landau, Vervey and Overbeek) forces and adhesive contacts to be measured under different conditions. In addition contact angles may be calculated from features of force versus distance curves. It is the purpose of this article to illustrate how the colloid probe technique can be used to make single particle-bubble interactions and to summarise the current literature describing such experiments.

Journal Article↗
PubMed2006

The safety of open inguinal herniorraphy in patients on chronic warfarin therapy.

BACKGROUND: The perioperative management of warfarin therapy increases the complexity of open inguinal herniorraphy. METHODS: One thousand consecutive patients undergoing open inguinal herniorraphy were retrospectively reviewed. Patients on warfarin therapy were categorized into 3 groups: continued warfarin (CW), discontinued warfarin (DW), and discontinued warfarin with anticoagulation bridge (DWB). RESULTS: Eighty-eight patients were on chronic warfarin therapy. Warfarin was continued in 19 patients, discontinued in 54, and discontinued with bridge in 15 patients. Operative times were similar between the 3 groups. Length of stay was longest in the discontinued warfarin with bridge group (CW 0.74, DW 0.54, and DWB 3.33 days; P < .0001). There was no significant difference in postoperative complications. The incidence of surgical site hematoma was higher in the continued warfarin and discontinued warfarin with bridge groups (CW 11%, DW 2%, and DWB 13%; P = .14). CONCLUSIONS: Continuation of warfarin may be a safe alternative to discontinuation of warfarin therapy in select patients undergoing open inguinal herniorraphy.

Aged↗
PubMed2006

Corticosteroids influence the mortality and morbidity of acute critical illness.

INTRODUCTION: Use of corticosteroids for adrenal supplementation and attenuation of the inflammatory and immune response is widespread in acute critical illness. The study hypothesis was that exposure to corticosteroids influences the mortality and morbidity in acute critical illness. METHODS: This case-control retrospective study was performed in a single multidisciplinary intensive care unit at a tertiary care institution and consisted of 10,285 critically ill patients admitted between 1 January 1999 and 31 December 2004. Demographics, comorbidities, acute illness characteristics including severity measured by Sequential Organ Failure Assessment, concurrent medications, therapeutic interventions and incidence of infections were obtained from electronic medical records, were examined with multiple regression analysis and were adjusted for propensity of corticosteroid exposure. The primary outcome was hospital death, and the secondary outcome was transfer to a care facility at hospital discharge. RESULTS: Corticosteroid exposure in 2,632 (26%) patients was characterized by younger age, more females, higher Charlson comorbidity and maximal daily Sequential Organ Failure Assessment scores compared with control patients. Corticosteroids potentiated metabolic and neuromuscular sequels of critical illness with increased requirements for diuretics, insulin, protracted weaning from mechanical ventilation, need for tracheostomy and discharge to a care facility. Early exposure to corticosteroids predisposed to recurrent and late onset of polymicrobial and fungal hospital-acquired infections. Corticosteroids increased the risk for death or disability after adjustments for comorbidities and acute illness characteristics. CONCLUSION: Corticosteroids increased the risk for death or disability in critical illness. Hospital-acquired infections and metabolic and neuromuscular sequels of critical illness were exacerbated by corticosteroids. Careful appraisal of the indications for use of corticosteroids is necessary to balance the benefits and risks from exposure in acute critical illness.

Acute Disease↗
PubMed2005

Cortisol levels and corticosteroid administration fail to predict mortality in critical illness: the confounding effects of organ dysfunction and sex.

BACKGROUND: Corticosteroid supplementation based on plasma cortisol measurement was reported to decrease mortality in vasopressor-dependent critical illness. HYPOTHESIS: Random levels or maximal increments of plasma cortisol measured after short adrenal stimulation may predict mortality independent of concurrent organ dysfunction or sex, and corticosteroid supplementation may decrease mortality in vasopressor-dependent critical illness. DESIGN: An observational descriptive study. PATIENTS: Critically ill patients receiving vasopressors for treatment of hemodynamic instability. METHODS: Random levels (n = 522 patients) and maximal increments (n = 282 patients) of plasma cortisol were measured after 250 microg of adrenocorticotropic hormone was administered for short stimulation tests before patients received corticosteroid supplementation. The severity of acute illness was measured by sequential organ failure assessment. MAIN OUTCOME MEASURE: Hospital mortality. RESULTS: The overall mortality was 24%. A random plasma cortisol level of 15 microg/dL or less was associated with lower mortality than a random plasma cortisol level greater than 15 microg/dL in men (12% vs 26%, respectively; P<.01) and women (13% vs 31%, respectively; P<.01). A maximal plasma cortisol increment of 9 microg/dL or less increased mortality as compared with an increment greater than 9 microg/dL in men (31% vs 11%, respectively; P<.01) but not in women (30% vs 29%, respectively; P = .8). Random levels and maximal increments of plasma cortisol did not influence hospital mortality predicted by the sequential organ failure assessment score. Corticosteroids were given to 244 patients (47%) without an effect on mortality (mortality rate of 27% for patients given corticosteroids vs mortality rate of 22% for patients who did not receive corticosteroids; P = .6). Corticosteroids did not influence mortality when plasma cortisol was a random level of 15 microg/dL or less (mortality rate of 14% for patients who received corticosteroids vs mortality rate of 10% for those who did not receive corticosteroids; P = .4) or when plasma cortisol was a maximal increment of 9 microg/dL or less (mortality rate of 30% for patients who received corticosteroids vs mortality rate of 31% for patients who did not receive corticosteroids; P = .9). CONCLUSIONS: Remote organ dysfunction and sex influenced mortality associated with cortisol levels measured in critical illness. Corticosteroid supplementation guided by arbitrary levels or increments of plasma cortisol in critical illness did not improve survival. Better guidelines for corticosteroid supplementation in critical illness should be developed to avoid potential adverse effects from unwarranted treatment.

Adrenal Cortex Hormones↗
PubMed2005

Influence of individual characteristics on outcome of glycemic control in intensive care unit patients with or without diabetes mellitus.

OBJECTIVE: To clarify the relationship of patient and critical illness characteristics (including any history of diabetes mellitus) to glycemic control with insulin and hospital mortality. PATIENTS AND METHODS: A case-control descriptive study was performed of patients admitted to a tertiary-care center multidisciplinary closed intensive care unit (ICU) at Mayo Clinic Hospital in Phoenix, Ariz, between January 1, 1999, and December 31, 2003, after implementation of a glycemic management protocol. Hospital mortality, the primary outcome, was examined in nondiabetic and diabetic ICU patients receiving insulin and in patients not requiring insulin (control group). RESULTS: Of 7285 patients, 2826 (39%) required insulin, 1083 of whom (15% of total) had a history of diabetes mellitus. The control group had a median (10th-90th percentile) glucose level of 118 mg/dL (range, 97-153 mg/dL) and a 5% mortality rate. The median glucose level was 134 mg/dL (range, 110-181 mg/dL) in nondiabetic patients and 170 mg/dL (121-238 mg/dL) in diabetic patients (P<.001), whereas mortality rates were 10% and 6%, respectively (P<.001). Compared with nondiabetic survivors, nondiabetic nonsurvivors had longer periods with glucose levels greater than 144 mg/dL. Diabetic nonsurvivors vs diabetic survivors had longer periods with glucose levels greater than 200 mg/dL. Poor glycemic control in nondiabetic patients was associated with increased insulin requirement and increased mortality. Critical illness characteristics that predicted poor glycemic control were advanced age, history of diabetes, cardiac surgery, postoperative complications, severity of illness, nosocomial infections, prolonged mechanical ventilation, or concurrent medications. CONCLUSIONS: Critical illness characteristics determined glycemic control and clinical outcome in ICU patients. Acute insulin resistance was associated with worse outcomes in nondiabetic patients. Although critical illness characteristics influenced glycemic control, future evaluation of the effect of insulin administration and optimal glycemic control in ICU patients is necessary.

Adult↗
PubMed2004

Histologic severity of appendicitis can be predicted by computed tomography.

HYPOTHESIS: A regression model based on computed tomographic (CT) findings alone can accurately predict the histologic severity of acute appendicitis in patients who have a high disease likelihood. DESIGN: Retrospective study. SETTING: Mayo Clinic in Scottsdale, Ariz. PATIENTS: Consecutive sample of 105 patients (50 women and 55 men, aged 15-89 years) undergoing nonincidental appendectomy within 3 days of nonfocused abdominal CT. INTERVENTIONS: Computed tomographic scans and histologic features were retrospectively reinterpreted. Each patient's histologic and CT findings were scored by standardized criteria. An ordinal logistic regression model was constructed with a subset of CT findings that statistically correlated best with the final histologic features. Predicted severity values were then generated from the model. MAIN OUTCOME MEASURE: Agreement between predicted and actual histologic severity, using weighted kappa measurement. RESULTS: Computed tomography variables used in the model were fat stranding, appendix diameter, dependent fluid, appendolithiasis, extraluminal air, and the radiologist's overall confidence score. The weighted kappa measurement of agreement between predicted and actual histologic severity was 0.75, with a 95% confidence interval between the values of 0.59 and 0.90. CONCLUSIONS: Computed tomographic findings, when used with the regression model developed from this pilot study, can accurately predict the histologic severity of acute appendicitis in patients initially seen with a high clinical suspicion of the disease. These findings provide a platform from which to prospectively test the model.

Acute Disease↗
PubMed2004

Cardiac surgery for octogenarians: is it an informed decision?

BACKGROUND: Cardiac surgery is frequently performed to palliate cardiovascular symptoms in patients who are octogenarians, without controlled clinical trials to support its benefits. We hypothesized that death or discharge to a nursing care facility after cardiac surgery is similar in patients who are octogenarians and younger patients. METHODS: We conducted an inception cohort study in a tertiary care teaching hospital in patients who had undergone coronary grafting, valve surgery, or both over 36 months before. We collected data on preoperative disease, operation characteristics, postoperative complications, and outcome at hospital discharge. RESULTS: Of 783 patients who had cardiac surgery, 96 were octogenarians. Female sex, pulmonary hypertension, previous malignancy, cerebral vascular disease, valvular heart disease, and congestive heart failure were more frequent in patients who were octogenarians than in younger patients. Operative characteristics were similar in both age groups, except there were more frequent valve or combined with coronary grafts surgery and surgical re-exploration in octogenarians. The rate of postoperative complications including cardiovascular, neurological, renal, and nosocomial infections were higher in patients who were octogenarians than younger patients. Death or discharge to a nursing care facility was more frequent in patients who were octogenarians than younger patients (53% vs 14%, P <.002). Age > or =80 years, female sex, congestive heart failure, and surgical re-exploration were independent predictors for death or discharge to a nursing care facility after cardiac surgery. CONCLUSIONS: The rate of death or discharge to nursing care facility after cardiac surgery was high among patients who were octogenarians. Current operative outcome end points do not reflect such important differences between patients who are octogenarians and younger patients. Informed discussion of treatment options, potential for discharge to a nursing care facility, and quality of life expectations should precede a decision to undergo cardiac surgery in patients who are octogenarians. Randomized clinical trials of medical versus surgical palliation of cardiovascular symptoms in patients who are octogenarians are needed to justify cost-effectiveness and guide better use of relatively scarce Medicare resources.

Age Factors↗
PubMed2004

Admission to intensive care unit at the end-of-life: is it an informed decision?

UNLABELLED: There is a major deficiency in the end-of-life care offered to patients dying in the intensive care unit (ICU). HYPOTHESIS: Hospitalized dying patients had informed discussions on end-of-life and palliative care options before admission to ICU. PATIENTS AND METHODS: A descriptive non-interventional study was performed at a teaching hospital to examine if patients who died in hospital had informed discussions on end-of-life care before admission to ICU. The impact of these discussions on subsequent patient care: aggressive therapy in the ICU, the quality of palliation, use of hospice care services and utilization of hospital resources were examined. Data were collected from medical records for all hospital deaths over 24 months. RESULTS: Of 252 hospital deaths, 196 (78%) were treated and subsequently 165 (65%) died in the ICU. Patients treated either in the ICU or general hospital wards had similar frequency of ultimately or rapidly fatal pre-existing disease (47% versus 62%, P: ns) and readmission to hospital within one year before death (43% versus 57%, P, ns). The median age (10-90% percentile) was slightly younger for the ICU than hospital wards patients: 73 (45-85) versus 76 (55-91) years, P < 0.01. Of the 156 patients who were transferred to ICU from hospital wards: 136 (87%) were managed by house staff on teaching services and 20 (13%) were managed by attending staff hospitalists, P < 0.01. None of those transferred to the ICU who subsequently died had discussion of palliation or end-of-life care as an alternative treatment. Of those who died who were treated on general wards, 14 (25%) patients had discussion of palliation as an alternative treatment option before death. Do-not-resuscitate decisions were made in 48% of cases two days before death. Patients who were treated in the ICU had more invasive tests performed on them and were less likely to have adequate pain control or referral to hospice care services than on a general ward. Median hospital charge was much higher for patients who received ICU versus general ward care (33,252 dollars versus 8549 dollars, P < 0.001). CONCLUSIONS: Patients who died in the ICU did not have informed discussions of end-of-life or palliative care as an alternative treatment option before admission. The quality of end-of-life care was disrupted for patients with fatal pre-existing chronic disease who were admitted to the ICU before death. Lack of clinical experience, knowledge and competency with end-of-life care influenced admission of patients to ICU regardless of poor prognosis. Decisions regarding the pursuit of aggressive therapy versus palliative care must be addressed with patients by physicians who are competent and experienced in end-of-life care as this will have a profound impact on both the quality of care delivered and effective use of limited hospital resources.

Aged↗
PubMed2004

Hospital discharge to care facility: a patient-centered outcome for the evaluation of intensive care for octogenarians.

INTRODUCTION: Hospital survival and length of stay are commonly used for the evaluation of intensive care outcome for the young and octogenarian patients (>/= 80 years old). HYPOTHESIS: Hospital discharge to a care facility should be considered for more accurate evaluation of intensive care outcome, especially for octogenarian patients. DESIGN: An observational descriptive study. PATIENTS: A total of 6,154 consecutive hospital admissions requiring intensive care over 4 years. MEASUREMENTS: Demographics, preadmission comorbidities, severity of illness, acute hospital diagnosis categories, charges and destination after discharge, and postdischarge survival for up to 42 months. RESULTS: Octogenarians represented 15% of intensive care admissions (900 admissions). The interventions performed in the ICU, the severity of illness measured by sequential organ failure assessment (SOFA), and hospital length of stay were similar for octogenarian and younger patients. Octogenarians had higher hospital mortality (10% vs 6%, p < 0.01) and discharge to care facility (35% vs 18%, p < 0.01) than younger patients. The average hospital charge per octogenarian hospital survivor discharged to home was $128,000, compared to $100,000 for a younger hospital survivor. At follow-up, octogenarian hospital survivors who were discharged to a care facility had higher mortality than hospital survivors discharged to home (31% vs 17%, p < 0.01). On multiple logistic regression, older age, female gender, preadmission comorbidities, type of admission, SOFA score >/= 4, mechanical ventilation >/= 96 h, requirement for tracheotomy, and hospital diagnosis categories were independent factors for discharge of hospital survivors to a care facility. CONCLUSIONS: Hospital survival and length of stay did not accurately measure intensive care outcome for octogenarians. Care dependency among octogenarians who survived intensive care was prevalent and decreased their long-term survival. Care dependency and functional disability among hospital survivors should be considered for more accurate evaluation of intensive care outcome in that age group.

Adult↗
PubMed2002

Stercoral perforation of the colon in a heroin addict.

BACKGROUND AND AIMS: Stercoral perforation of the colon is rare. Narcotics are well known to produce chronic constipation resulting in stercoral perforation, however, only one case of a heroin addict developing stercoral perforation has been reported. PATIENTS AND METHODS: We present a case of a 67 year-old man with chronic heroin use and stercoral perforation requiring sigmoidectomy and Hartmann's procedure. Computed tomography was performed prior to exploration. RESULTS: This is the first case of computed tomography findings, prior to laparotomy, that have been published for stercoral perforation.

Aged↗