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Biomedical subjects

M A Warner

Publications and source records attributed to M A Warner.

At least 19 recordsLinked to original sources
PubMed1992

Sympathetic modulation of blood flow and O2 uptake in rhythmically contracting human forearm muscles.

This study tested the effects of sympathetically mediated changes in blood flow to active muscles on muscle O2 uptake (VO2) in humans. Four minutes of graded (15-80% of maximum voluntary contraction, MVC) rhythmic handgrip exercise were performed. Forearm blood flow (FBF) (plethysmography) and deep vein O2 saturation were measured each minute. Forearm O2 uptake was calculated using the Fick principle. In protocol 1, exercise was performed while supine and again while upright to augment sympathetic outflow to the active muscles. Standing reduced FBF at rest from 3.6 to 2.2 ml.100 ml-1.min-1 (P < 0.05). During light exercise (15-40% MVC) FBF was unaffected by body position. Standing reduced FBF (P < 0.05) from 36.0 to 25.2 ml.100 ml-1.min-1 and forearm VO2 from 38.2 to 28.1 ml.kg-1.min-1 during the final work load. In protocol 2, exercise was performed while supine before and after local anesthetic block of the sympathetic nerves to the forearm. Sympathetic block increased FBF at rest from 3.1 to 8.9 ml.100 ml-1.min-1 (P < 0.05), and FBF was higher during all work loads At 70-80% of MVC sympathetic block increased FBF from 35.4 to 50.7 ml.100 ml-1.min-1 (P < 0.05), and forearm VO2 from 45.5 to 54.2 ml.kg-1.min-1 (P < 0.05). These results suggest that in humans sympathetic nerves modulate blood flow to active muscles during light and heavy rhythmic exercise and that this restraint of flow can limit O2 uptake in muscles performing heavy rhythmic exercise.

Adolescent↗
PubMed1991

Narcotic-induced histamine release: a comparison of morphine, oxymorphone, and fentanyl infusions.

This study, using an improved histamine assay, repeated previous studies that demonstrated large doses of morphine for induction of anesthesia in patients undergoing coronary artery bypass grafting were associated with histamine release. Thirty randomized patients received infusions of either morphine, 1 mg/kg, oxymorphone, 0.2 mg/kg, or fentanyl, 50 micrograms/kg, over a 10-minute period for induction of anesthesia prior to surgery. There were no significant changes in plasma histamine levels in individual patients or among drug groups. The discrepancy between the present histamine results and those previously reported using similar protocols is due, in part, to variations in plasma histamine measurements that can occur using the less reproducible, older assays for histamine. During routine inductions, large doses of morphine, oxymorphone, or fentanyl administered by infusion do not appear to stimulate release of clinically significant plasma levels of histamine.

Aged↗
PubMed1991

Preoperative laboratory screening in healthy Mayo patients: cost-effective elimination of tests and unchanged outcomes.

We reviewed the results of preoperative screening laboratory tests in asymptomatic healthy patients who underwent elective surgical procedures at our institution in 1988. Substantially abnormal results were found in 160 of 3,782 patients. All such abnormalities involved five tests: aspartate aminotransferase, glucose, potassium, platelet count, and hemoglobin. Thirty of the abnormal test results were predictable on the basis of the history or physical examination. The abnormal test result prompted further assessment in 47 patients. No surgical procedure was delayed, and no association was noted between adverse outcome and any preoperative laboratory abnormality. Because of our findings in this analysis and similar studies on specific tests from other institutions, we no longer require preoperative laboratory screening tests for healthy patients.

Adult↗
PubMed1991

Regionally selective effects of NMDA receptor antagonists against ischemic brain damage in the gerbil.

This study compared the ability of three N-methyl-D-aspartate (NMDA) receptor antagonists to prevent neuronal degeneration in an animal model of global cerebral ischemia. The model employed is characterized by damage to the striatum, hippocampus, and neocortex. Antagonists were administered to gerbils either before or after a 5-min bilateral carotid occlusion. The intraischemic rectal temperature was either maintained at 36-37 degrees C or allowed to fall passively to 28-32 degrees C. Antagonists and doses tested were 1 and 10 mg/kg of MK-801 (pre- or postischemia), 30 mg/kg of CGS 19755 preischemia, four 25 mg/kg doses of CGS 19755 administered between 0.5 and 6.5 h postischemia, and 40 mg/kg of MDL 27,266 (pre- or postischemia). All three NMDA receptor antagonists exhibited some degree of neuroprotective activity when the carotid occlusion was performed under normothermic conditions. Most of the treatments with antagonist markedly reduced striatal damage. CA1 hippocampal and neocortical pyramidal cells were spared by only three of the treatments, however, and the extent of neuroprotection varied widely from case to case. Toxic doses of antagonist were required to protect CA1 pyramidal cells from ischemic damage. Ischemic damage to hippocampal areas CA2-CA3a and CA4 appeared to be resistant to all of these treatments. Most CA1 pyramidal cells that were protected from degeneration by an NMDA receptor antagonist were histologically abnormal. The neuroprotective effects of MK-801 and intraischemic hypothermia appeared to be additive. MK-801 (10 mg/kg) consistently reduced the postischemic brain temperature, but only the magnitude of hypothermia produced soon after reperfusion correlated with its neuroprotective action. These results suggest that NMDA receptor antagonists are relatively poor neuroprotective agents against a moderately severe ischemic insult.

Animals↗
PubMed1990

Effects of referral bias on surgical outcomes: a population-based study of surgical patients 90 years of age or older.

During the 11-year period 1975 through 1985, 1,063 surgical procedures were performed on 795 Mayo Clinic patients 90 years of age or older. Preoperative conditions, surgical setting, and perioperative morbidity and mortality were analyzed in a comparison of the local residents of Olmsted County, Minnesota (N = 224), with patients from outside the county but within 250 miles (N = 456) or referrals from a distance of 250 miles or further (N = 115). In comparison with non-Olmsted County patients, Olmsted County patients were generally older, had more preoperative chronic diseases, and underwent more emergency operations. Patients who had traveled 250 miles or more to the Mayo Clinic were more likely to be men and referred for cancer-related surgical procedures. The risks of major morbidity and mortality within 48 hours postoperatively were increased in patients with more preoperative chronic diseases and those undergoing emergency procedures, characteristics most common in Olmsted County patients. Because of differences in these factors between groups, perioperative risks averaged over our entire patient series underestimated risks that would be expected from a population-based cohort such as Olmsted County residents. In general, data from tertiary medical centers probably do not accurately reflect overall practice or outcomes in community settings.

Academic Medical Centers↗
PubMed1990

Transfusion risks.

Hepatitis remains the most serious transfusion risk, in terms of incidence and severity. Transfusion-associated AIDS, hemolytic reactions, TRALI, and anaphylaxis are severe problems that occur relatively rarely, while febrile reactions and mild allergic reactions are common but not serious. The key to avoiding all these complications is autotransfusion (see the article "Autologous Transfusion" in this issue). Although intraoperative scavenging became available in many centers in the United States in the 1980s, it is hoped that pre-deposit autotransfusion will also become widely utilized in the next decade.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Outcomes of surgery in patients 90 years of age and older.

During the 11-year period 1975 through 1985, seven hundred ninety-five patients 90 years of age and older underwent operative procedures at the Mayo Clinic, Rochester, Minn. Overall serious morbidity within 48 hours after surgery was 9.4%, and the mortality was 1.6%. The 30-day, 1-year, and 5-year mortality rates were 8.4%, 31.4%, and 78.8%, respectively. Short-term morbidity and both short- and long-term mortality were highly associated with the American Society of Anesthesiologists physical status classification of the patient. Emergency procedures carried a significantly higher risk for morbidity and mortality within the 48-hour period and, to a lesser extent, for long-term mortality. Overall, poorer patient survival was associated with higher American Society of Anesthesiologists class; male sex; preoperative renal, liver, and central nervous system impairment; and surgery on the mouth, nose, or pharynx. When compared with age-, sex-, and calendar year--matched peers from the general population, there was a modest decrease in patient survival at 1 year that reversed by 2 years, with observed survival at 5 years comparable to the rate expected.

Age Factors↗
PubMed1989

Extracorporeal shock-wave lithotripsy and methyl tert-butyl ether for partially calcified gallstones.

To explore the possibility that gallbladder stone fragments might be able to be safely dissolved using methyl tert-butyl ether immediately after extracorporeal shock-wave lithotripsy (ESWL), a feasibility study in 8 patients with one to four partially calcified gallbladder stones was performed. The gallstones averaged 2.2 cm in diameter (range 1.3-3 cm) and contained layered or diffuse calcium detectable by computed tomography scan only (7 patients) or plain film (1 patient). After a 5F (1.7 mm) pigtail catheter was placed percutaneously into the gallbladder, ESWL fragmentation was performed using a renal stone lithotriptor. The patients were under general anesthesia and in the prone position on a support gantry designed for gallbladder stone ESWL. Following ESWL, methyl tert-butyl ether was infused and aspirated via the gallbladder catheter until no further stone material was radiologically detectable or could be dissolved. After 8-26 h (mean = 13 h) of methyl tert-butyl ether therapy, no radiologically detectable gallstones remained in 6 of 8 patients. Shell fragments of three peripherally calcified stones in 1 patient and the densely calcified, predominantly pigment stone in a second patient were refractory to combined therapy. Both ESWL and treatment with methyl tert-butyl ether were well tolerated in all patients, although bile leakage after catheter removal occurred in 3 patients, one of whom was treated by cholecystectomy. Additional measures to prevent bile leakage may be advisable if these two modalities are to be used in tandem. We found no evidence, however, that predissolution stone fragmentation with ESWL predisposed the gallbladder to either mucosal damage by methyl tert-butyl ether or increased absorption of it.

Aged↗
PubMed1989

Role of preoperative cessation of smoking and other factors in postoperative pulmonary complications: a blinded prospective study of coronary artery bypass patients.

The association between preoperative smoking cessation and postoperative pulmonary morbidity was studied prospectively in 200 consecutive patients undergoing an elective coronary artery bypass surgical procedure. Detailed respiratory, cardiovascular, and smoking histories were elicited. Preoperative arterial blood gas analyses and bedside spirometry were performed. Urinary cotinine levels were measured to verify smoking histories. During spirometry, severe angina developed in seven patients, who were hence excluded from the study; one patient died of hemorrhage intraoperatively. An observer unaware of patients' preoperative histories assessed the remaining 192 patients throughout the intraoperative and postoperative periods for pulmonary complications. Postoperative pulmonary complications occurred in a third of the current smokers. Patients who had stopped smoking for 2 months or less had a pulmonary complication rate almost 4 times that of patients who had stopped for more than 2 months (57.1% versus 14.5%). Patients who had stopped smoking for more than 6 months had rates similar to those who had never smoked (11.1% and 11.9%, respectively). Preoperative pulmonary dysfunction, increased pack-years of smoking, prolonged surgical time, and the use of enflurane were independently associated with postoperative pulmonary morbidity (P less than 0.05). We concluded that smoking cessation should occur at least 2 months preoperatively to maximize the reduction of postoperative respiratory complications.

Aged↗
PubMed1989

Anaesthesia for patients over 90 years of age. Outcomes after regional and general anaesthetic techniques for two common surgical procedures.

Peri-operative morbidity and mortality and long term outcome of patients over 90 years of age who underwent either total hip arthroplasty or transurethral prostate resection were studied retrospectively. The outcomes of patients who received regional or general anaesthesia were compared. One hundred and forty-one patients underwent total hip arthroplasty and 44 patients underwent transurethral prostate resection during the study period (1975-1985). Overall in-hospital mortality was 4.9% Mortality at 30 days was 5.3% in patients who underwent hip arthroplasty during regional anaesthesia, compared with 6.8% in those who received general anaesthesia. Long term survival was similar for these two groups and was longer than projected for age and gender-matched general population cohorts. The 30-day mortality rate was 3.2% for patients who underwent prostatic resection under regional anaesthesia; no deaths occurred in the general anaesthesia group. This difference was not statistically significant. Long term survival was similar for patients in both groups and was better than predicted. Anaesthetic technique did not influence short term morbidity and mortality or long term outcome for these procedures.

Aged↗
PubMed1988

Clinical efficacy of high frequency jet ventilation during extracorporeal shock wave lithotripsy of renal and ureteral calculi: a comparison with conventional mechanical ventilation.

The use of high frequency jet ventilation compared to conventional mechanical ventilation during general anesthesia for extracorporeal shock wave lithotripsy of renal or ureteral calculi can reduce stone movement. This decrease in stone movement theoretically lessens the total shock and energy requirements for stone fragmentation and perirenal tissue damage. To assess these theoretical advantages of high frequency jet ventilation, we studied patients undergoing extracorporeal shock wave lithotripsy to determine differences in stone movement during high frequency jet and conventional mechanical ventilation (30 patients), and in total shock requirements (1,174 patients). Mean stone movement in the 30 patients was 34.3 +/- 4.3 mm. during conventional mechanical ventilation compared to 4.1 +/- 1.9 mm. during high frequency jet ventilation (p less than 0.001). Mean total shocks were 1,542 +/- 212 (452 patients) during conventional mechanical ventilation compared to 1,217 +/- 165 (722 patients) during high frequency jet ventilation (p less than 0.001). Only 1 patient in the study had clinically significant perirenal tissue damage. We conclude that high frequency jet ventilation when compared to conventional mechanical ventilation results in clinically and economically beneficial decreases in total shocks for extracorporeal shock wave lithotripsy fragmentation of renal or ureteral calculi.

Anesthesia, General↗
PubMed1988

Surgical procedures among those greater than or equal to 90 years of age. A population-based study in Olmsted County, Minnesota, 1975-1985.

Persons greater than or equal to 90 years of age represent a rapidly growing subset of the population, but little data exist on their utilization of the health care system. Population-based data capabilities of the Rochester/Olmsted County Epidemiology Project were used to study the performance of surgery among persons greater than or equal to 90 years of age for the 11-year period, 1975-1985. During this time, 224 residents of Olmsted County, Minnesota underwent 301 separate operations. The annual operation rate increased over the course of the study (trend test, p less than 0.001), reaching a plateau of 89.0 per 1000 person-years. This suggests a potential for nearly 91,000 operations annually in this age group based on 1987 U.S. Census estimates. Ninety-two per cent were discharged from the hospital alive, and 5-year survival was consistent with that expected (23% vs. 17%). Increased longevity of the general population, combined with increased performance of surgery in this rapidly growing segment of the population, may have significant implications for health care planning.

Aged↗
PubMed1988

Open lung biopsy in patients with diffuse pulmonary infiltrates and acute respiratory failure.

Patients with diffuse pulmonary infiltrates and acute respiratory failure (ARF) potentially can benefit from diagnostic information provided by open lung biopsy (OLB). To better quantify possible benefits and risks, we reviewed an 11-yr experience with 80 such patients. Although OLB did provide a specific etiologic diagnosis in 53 patients (66%) and did influence therapy in 56 patients (70%), only 24 patients (30%) survived to hospital discharge, and 9 patients (11%) survived for 1 yr or more. Survival rates did not depend on the availability of a specific diagnosis, changes in diagnosis, or changes in therapy. Survival was improved in younger patients and patients not requiring preoperative mechanical ventilation. Fifteen patients (19%) suffered complications possibly related to OLB; the survival rate to discharge was decreased in these patients, although not significantly. We conclude that OLB provides a specific etiologic diagnosis in many patients with diffuse pulmonary infiltrates and ARF, but that its utility in these patients is limited by current shortcomings of therapy.

Acute Disease↗