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Biomedical subjects

L K Weaver

Publications and source records attributed to L K Weaver.

At least 37 records · Page 2Linked to original sources
PubMed1996

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.

Activities of Daily Living↗
PubMed1995

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.

Adult↗
PubMed1995

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).

Anti-Bacterial Agents↗
PubMed1994

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.

Adult↗
PubMed1994

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.

Adult↗
PubMed1994

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.

Adult↗
PubMed1992

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.

Adult↗
PubMed1992

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.

Age Factors↗
PubMed1992

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.

Adult↗
PubMed1991

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.

Blood Pressure↗
PubMed1988

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.

Cough↗