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Biomedical subjects

R I Hall

Publications and source records attributed to R I Hall.

At least 19 recordsLinked to original sources
PubMed2004

A phase II dose-response study of hemoglobin raffimer (Hemolink) in elective coronary artery bypass surgery.

BACKGROUND: We performed this study to determine the dose-response of hemoglobin raffimer administered in conjunction with intraoperative autologous donation in patients undergoing coronary artery bypass grafting surgery. A secondary objective was to evaluate hemoglobin raffimer for reducing the incidence of allogeneic red blood cell transfusions. METHODS: This was a phase II, single-blind, multicenter, placebo-controlled, open-label study. Patients undergoing coronary artery bypass grafting with cardiopulmonary bypass and intraoperative autologous donation were randomized to receive a single dose of hemoglobin raffimer or control (10% pentastarch). Patients were sequentially enrolled in a dose block of 250, 500, 750, and 1000 mL. RESULTS: Sixty patients received hemoglobin raffimer (n = 30) or control (n = 30). Hemoglobin raffimer was well tolerated. Most (98%) adverse events were mild or moderate in severity. There was an expected dose-dependent increase in the incidence of blood pressure increases and jaundice in hemoglobin raffimer-treated patients. In a dose-pooled analysis of hemoglobin raffimer versus control, increased blood pressure (43% vs 17%), nausea (37% vs 33%), and atrial fibrillation (37% vs 17%) were the most frequently reported adverse events. All serious adverse events were considered unrelated or unlikely to be related to study drug. No hemoglobin raffimer-treated patient required an intraoperative allogeneic red blood cell transfusion, compared with 5 (17%) pentastarch-treated patients (P =.052). This advantage of hemoglobin raffimer was maintained at 24 hours after surgery (7% vs 37%; P =.010) and up to 5 days after surgery (10% vs 47%; P =.0034). CONCLUSIONS: Hemoglobin raffimer was not associated with any serious adverse events in patients undergoing primary coronary artery bypass grafting with cardiopulmonary bypass and intraoperative autologous donation in a dose-response study up to 1000 mL. Hemoglobin raffimer was effective in facilitating decreased exposure or avoidance of allogeneic red blood cell transfusions when used in conjunction with intraoperative autologous donation.

Adult↗
PubMed2003

Experimental determination of the lifetime for the 2p3d(1P0) helium doubly excited state.

Two recent theoretical studies [C. Liu, Phys. Rev. A 64, 010501 (2001)]; M. Zitnik, ibid. 65, 032520 (2002)]] predict that the fluorescence lifetimes of helium doubly excited states converging to He+ N=2 should be longer than that of the He+ 2p ion state. This effect is caused by the electric field of the outer electron which, through Stark mixing, gives the inner fluorescing electron some series specific, stabilizing 2s character. We have obtained the first experimental evidence that confirms this effect by measuring the lifetime of the 2p3d(1P0) doubly excited state. This was determined to be 190+/-30 ps compared to 100 ps for the He+ 2p ion state. The measurements were performed using short pulses of synchrotron radiation to form doubly excited states and recording the arrival time of photons from fluorescence.

Journal Article↗
PubMed2003

Complete two-electron spectra in double photoionization: the rare gases Ar, Kr, and Xe.

A new spectroscopic technique, giving complete two-dimensional e(-)-e(-) coincidence spectra in single photon double photoionization, is presented. The technique resolves the states of doubly charged ions and provides spectra of the individual electrons emitted in formation of each final dication state. Complete spectra for double photoionization of Xe, Kr, and Ar at photon energies up to 51 eV have been recorded. Overall and surprisingly, the np(4) 3P, 1D, and 1S states are populated according to their statistical weights. When the evident autoionization is excluded, the supposedly favored 3P states are in fact disfavored. Detailed information on the autoionization processes is also made available.

Journal Article↗
PubMed2001

Dynamics and post-collision interaction effects in two electron decay from the Xenon 4d hole.

Two Auger electrons, one very slow, one fast, have been detected in coincidence following near threshold 4d photoionization of the Xe atom. The distribution in the energy the two electrons share has been measured for the first time revealing the presence of post-collision interaction effects that provide unique information on the decay dynamics of the 4d hole. Analysis of the distorted line shapes indicates that the dominant process is decay of Xe+(4d(-1)) to Xe3+ through cascade emission of a zero kinetic energy Auger electron followed by a fast Auger electron. The widths of the intermediate Xe2+* states are estimated to be about 60 meV.

Journal Article↗
PubMed2001

Observation of triplet doubly excited states in single photon excitation from ground state helium.

We have observed, for the first time, LS-forbidden triplet doubly excited states, in single photon excitation of ground state helium, below the second ionization threshold. These states are identified as (3)D(o) and (3)P(o) and their excitation is due to spin-orbit interaction that mixes them with the optically allowed (1)P(o) states. This observation is possible due to the very high efficiency in detecting metastable atoms created after the fluorescence decay of the doubly excited states, and the new capabilities of third generation synchrotron vacuum ultraviolet sources with high resolution beam lines.

Journal Article↗
PubMed2001

Comparison of cisapride and metoclopramide for facilitating gastric emptying and improving tolerance to intragastric enteral nutrition in critically III, mechanically ventilated adults.

BACKGROUND: Placebo-controlled studies have indicated that both cisapride and metoclopramide promote gastric motility in critically ill patients. OBJECTIVE: This study was conducted to compare cisapride and metoclopramide for facilitating gastric emptying and improving tolerance to intragastric enteral nutrition (EN) and to evaluate the relationship between aspirated gastric residual volume and gastric emptying function in this patient population. METHODS: In this double-blind study, critically ill, mechanically ventilated patients with an aspirated gastric residual volume > or = 150 mL while receiving intragastric EN were randomized to receive enteral cisapride 10 mg or metoclopramide 10 mg every 6 hours for a total of 7 doses. The acetaminophen-absorption method was used to assess gastric emptying at baseline and 30 minutes after the seventh dose by determining the area under the plasma concentration-time curve at 240 minutes (AUC240), maximum concentration (Cmax), and time to Cmax (Tmax). Gastric residual volume was measured every 6 hours before dosing. RESULTS: Fourteen patients were included in the study, 7 in each group. Patient characteristics were similar in the 2 groups. Compared with baseline, metoclopramide significantly accelerated Tmax (39.00 +/- 15.56 min with metoclopramide vs 103.71 +/- 47.35 min at baseline; P = 0.018) and increased Cmax (12.94 +/- 6.68 mg/L vs 6.97 +/- 4.78 mg/L; P = 0.018) and AUC240 (1,421.43 +/- 780.31 mg/L x min vs 839.00 +/- 545.58 mg/L x min; P = 0.043). Cisapride increased Cmax from baseline (12.27 +/- 8.95 mg/L vs 4.53 +/- 2.37 mg/L, respectively), but the difference was not statistically significant. Gastric residual volume was significantly reduced from baseline after 3 doses of metoclopramide (from 268.7 +/- 112.3 mL to 57.0 +/- 23.1 mL; P < 0.05) and was significantly lower after the seventh dose of metoclopramide than after the seventh dose of cisapride (5.3 +/- 8.2 mL vs 41.4 +/- 39.7 mL, respectively; P = 0.05). Cmax at baseline and residual volume at study entry were inversely correlated (r = -0.50; P = 0.049). CONCLUSIONS: Both cisapride and metoclopramide enhanced gastric motility and improved tolerance to intragastric EN. Metoclopramide reduced gastric residual volume to a significantly greater extent than did cisapride. Only Cmax at baseline was inversely associated with residual volume.

Adolescent↗
PubMed2001

Propofol vs midazolam for ICU sedation : a Canadian multicenter randomized trial.

STUDY OBJECTIVES: To determine whether sedation with propofol would lead to shorter times to tracheal extubation and ICU length of stay than sedation with midazolam. DESIGN: Multicenter, randomized, open label. SETTING: Four academic tertiary-care ICUs in Canada. PATIENTS: Critically ill patients requiring continuous sedation while receiving mechanical ventilation. INTERVENTIONS: Random allocation by predicted requirement for mechanical ventilation (short sedation stratum, < 24 h; medium sedation stratum, > or = 24 and < 72 h; and long sedation stratum, > or = 72 h) to sedation regimens utilizing propofol or midazolam. MEASUREMENTS AND RESULTS: Using an intention-to-treat analysis, patients randomized to receive propofol in the short sedation stratum (propofol, 21 patients; midazolam, 26 patients) and the long sedation stratum (propofol, 4 patients; midazolam, 10 patients) were extubated earlier (short sedation stratum: propofol, 5.6 h; midazolam, 11.9 h; long sedation stratum: propofol, 8.4 h; midazolam, 46.8 h; p < 0.05). Pooled results showed that patients treated with propofol (n = 46) were extubated earlier than those treated with midazolam (n = 53) (6.7 vs 24.7 h, respectively; p < 0.05) following discontinuation of the sedation but were not discharged from ICU earlier (94.0 vs 63.7 h, respectively; p = 0.26). Propofol-treated patients spent a larger percentage of time at the target Ramsay sedation level than midazolam-treated patients (60.2% vs 44.0%, respectively; p < 0.05). Using a treatment-received analysis, propofol sedation either did not differ from midazolam sedation in time to tracheal extubation or ICU discharge (sedation duration, < 24 h) or was associated with earlier tracheal extubation but longer time to ICU discharge (sedation duration, > or = 24 h, < 72 h, or > or = 72 h). CONCLUSIONS: The use of propofol sedation allowed for more rapid tracheal extubation than when midazolam sedation was employed. This did not result in earlier ICU discharge.

Aged↗
PubMed2000

Stroke.

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Acute Disease↗
PubMed2000

End-of-life care in the ICU: treatments provided when life support was or was not withdrawn.

STUDY OBJECTIVE: To compare and contrast use of technology, pharmacology, and physician variability in end-of-life care of ICU patients dying with or without active life support. DESIGN: Retrospective cohort study. SETTING: Two medical-surgical tertiary-care ICUs in a Canadian regional referral teaching hospital. PARTICIPANTS: One hundred seventy-four patients who died between July 1, 1996, and June 30, 1997. INTERVENTION: Data abstraction from medical records. RESULTS: Patients in whom life support was withheld or withdrawn (138 of 174, 79%) were older (65 +/- 16 years vs 55 +/- 18 years; p < 0.05 [mean +/- SD]). Once the decision to withdraw life support was made, death occurred in 4.3 h (2.1 to 6.5 h; mean [95% confidence interval]). Patients who had active life support treatment until death received more support measures including inotropic agents (36 of 36 vs 21 of 138; p < 0.05), dialysis (4 of 36 vs 2 of 138; p < 0.05), and mechanical ventilation at the time of death (36 of 36 vs 81 of 138; p < 0.05). Physician differences (> 10-fold) were detected for prescribed doses of morphine and sedative agents whether or not life support was withheld or withdrawn. The median cumulative dose of morphine prescribed during the final 12 h was larger (fivefold) in patients undergoing withdrawal of life support. No documented discussion of life support withdrawal was noted in one case. In the remaining patients, the 10 staff physicians were documented to be involved in 77% (range, 54 to 94%) of the end-of-life discussions. CONCLUSIONS: Differences were evident in technologic and pharmacologic support and in physician prescribing habits in patients for whom life support was or was not withheld or withdrawn. Substantial variability was noted in physician documentation of physician-family interactions surrounding the withdrawal of life support.

Age Factors↗
PubMed2000

A prospective evaluation of empiric versus protocol-based sedation and analgesia.

STUDY OBJECTIVE: To compare empiric and protocol-based therapies of sedation and analgesia in terms of pharmacologic cost, effects on mechanical ventilation and intensive care unit (ICU) stay, and quality of sedation and analgesia. DESIGN: Prospective study. SETTING: A 24-bed medical-surgical-neurologic ICU. PATIENTS: Seventy-two patients evaluated during empiric therapy and 86 during protocol-based therapy. INTERVENTION: Assessment of data collected for 4 months before and 5 months after an evidence-based sedation and analgesia protocol was implemented. MEASUREMENTS AND MAIN RESULTS: Protocol adherence rate was 83.7%. The hourly cost (Canadian dollars) of sedation was less with protocol-based therapy ($5.68 +/- 4.27 vs $7.69 +/- 5.29, p<0.01) likely due to increased lorazepam use. Pharmacologic cost savings may be negated since sedation duration tended to be longer (122.7 +/- 142.8 vs 88.0 +/- 94.8 hrs, p<0.1) and extubation may have been delayed (61.6 +/- 97.4 vs 39.1 +/- 54.7 hrs, p=0.13) with protocol use. Duration of ICU stay after sedation was discontinued was not significantly different before and after protocol implementation. With the protocol, however, the percentage of modified Ramsay sedation scores representing discomfort decreased from 22.4 to 11% (p<0.001) and the percentage at a score of 4 increased from 17.2% to 29.6% (p<0.01). The percentage of modified visual analog measurements representing pain decreased from 9.6 to 5.9% (p<0.05) with the protocol. When data were stratified according to duration of sedation, the benefits and delayed extubation associated with protocol-based therapy were limited to patients requiring long-term sedation. CONCLUSION: Compliance with this protocol reduced drug costs and enhanced the quality of sedation and analgesia for patients requiring long-term sedation. Protocol-based therapy with lorazepam may have delayed extubation but did not delay ICU discharge.

Analgesia↗
PubMed1999

Limited resuscitation with hypertonic saline, hypertonic sodium acetate, and lactated Ringer's solutions in a model of uncontrolled hemorrhage from a vascular injury.

BACKGROUND: Hypertonic sodium acetate-dextran solution (HAD) causes vasodilatation and buffers metabolic acidosis. In controlled hemorrhage models, HAD in small volumes increases cardiac output without increasing blood pressure, thus creating a "high flow-low pressure" state. The objective of this study was to determine whether limited resuscitation of uncontrolled hemorrhage with HAD solution improves gut perfusion as measured by intestinal mucosal tonometry. METHODS: Three groups of 10 swine were bled 25 mL/kg by means of a femoral artery catheter to produce a mean blood pressure of 30 mm Hg. A 4-mm abdominal aortic laceration was then produced by pulling out a preimplanted wire loop. Groups were then randomly assigned to be resuscitated with either lactated Ringer's solution, a hypertonic saline-dextran solution or HAD solution sufficient to maintain a mean blood pressure of 45 mm Hg for 5 hours or until death. Outcomes were measured by survival, intraperitoneal blood loss, hemodynamic monitoring, and ileal mucosal tonometry. RESULTS: HAD infusions caused transient worsening of hypotension and were associated with increased mortality (p = 0.038). Blood loss and volumes required for resuscitation were significantly increased in the lactated Ringer's solution group. HAD showed significant buffering effect against metabolic acidosis in arterial blood only, but intestinal ileal mucosal tonometry was not different among the groups. CONCLUSION: HAD did not improve gut perfusion despite buffering the systemic acidosis of shock and caused increased mortality. Limited resuscitation with any of these solutions is associated with significant mucosal acidosis.

Acid-Base Equilibrium↗