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Biomedical subjects

M A Warner

Publications and source records attributed to M A Warner.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effect of various lithotomy positions on lower-extremity blood pressure.

BACKGROUND: Compartment syndrome of a lower extremity from hypoperfusion is a rare but potentially devastating complication of the lithotomy position during surgery. The aim of this study is to determine the effects of various lithotomy positions on lower-extremity blood pressures. METHODS: Blood pressure in eight young, healthy people was studied for 10 lithotomy positions. Blood pressure measurements were taken in both the upper arm (brachial artery) and the lower extremity (dorsalis pedis). The heart-to-ankle height gradient in each position was measured, and a predicted lower-extremity systolic pressure was calculated. The measured and predicted lower-extremity systolic blood pressures were compared with repeated measures analysis of variance. RESULTS: As a group, the mean systolic blood pressures in the lower extremities correlated closely with the predicted values. However, the difference between measured and predicted pressures varied among the 10 positions (P < 0.05). CONCLUSIONS: Although lower-extremity systolic blood pressures in the young, healthy volunteers correlated with predicted values, there was an additional reduction in pressure associated with the lithotomy position. This surprising finding suggests that a lengthy procedure necessitating the use of a lithotomy position for only a portion should be planned so the remainder of the procedure can take place before establishing the position or so the position can be changed to an alternative position when it is no longer needed.

Adolescent↗
PubMed1998

Outcomes of anesthesia and surgery in people 100 years of age and older.

OBJECTIVE: To assess the outcomes of anesthesia and surgery for men and women 100 years of age and older. DESIGN: Retrospective cohort study in the 20-year time period from 1975 to 1994, with follow-up through 1995. SETTING: Mayo-affiliated hospitals and Olmsted Community Hospital, Rochester, Minnesota. PARTICIPANTS: All men and women 100 years of age and older who underwent surgery at a participating hospital. MEASUREMENTS: Forty-eight-hour and 30-day perioperative morbidity and mortality; long-term survival. RESULTS: Thirty-one men and women aged 100 to 107 years underwent 42 procedures. One major complication (3%) within 48 hours was observed. The 48-hour, 30-day, and 1-year mortality rates were 0%, 16.1%, and 35.5%, respectively. When compared with survival rates for age-, gender-, and calendar year of birth-matched peers from the general population, the survival rate for centenarians who underwent surgery and anesthesia was comparable to the rate expected. CONCLUSION: These data suggest that people 100 years of age and older who have operable diseases or injuries should not be denied surgical interventions because of perceived risks associated with their advanced age.

Age Factors↗
PubMed1998

Perioperative neuropathies.

Neuropathies are infrequent but potentially debilitating complications in surgical patients. Although the most common of these affect the peripheral ulnar and sciatic nerves, more centrally located sets of nerves such as the brachial plexus and lumbosacral nerve roots also can be affected perioperatively. Traditionally, these neuropathies have been considered avoidable and associated with inappropriate patient positioning intraoperatively. Recent epidemiologic and anatomic studies suggest, however, that various factors other than intraoperative positioning may contribute to the development of neuropathies. For example, it is now clear that a large proportion of surgical patients who subsequently have development of ulnar neuropathies are asymptomatic during the first several postoperative days. Further delineation of the epidemiology and causes of the various perioperative neuropathies should lead to innovative interventions and clinical trials of their effectiveness to decrease the frequency and severity of these complications in surgical patients.

Humans↗
PubMed1998

Outcomes of noncardiac surgical procedures in children and adults with congenital heart disease. Mayo Perioperative Outcomes Group.

OBJECTIVE: To assess the outcomes and risk factors for morbidity associated with anesthesia and noncardiac surgical procedures in children and adults with congenital heart disease. DESIGN: We conducted a retrospective cohort study of the 6-year period from January 1987 through November 1992 at one of the Mayo-affiliated hospitals in Rochester, Minnesota. MATERIAL AND METHODS: In all children and adults 50 years of age or younger with congenital heart disease who underwent one or more noncardiac surgical or diagnostic procedures and anesthesia, we analyzed the risk factors for 30-day perioperative morbidity and mortality. RESULTS: The overall frequency of complications among the 276 patients who underwent 480 noncardiac surgical procedures and anesthesia was 5.8% (28 of 480), and only 1 patient died intraoperatively. Major risk factors univariately associated with complications for the first procedures (15 of 276 patients or 5.4%) included the presence of cyanosis (P = 0.002), current treatment for congestive heart failure (P<0.001), poor general health (P<0.001), and younger age at the time of the procedure (P = 0.027). Procedures performed on the respiratory and nervous systems also were associated with high frequencies of complications. Complications in patients undergoing ambulatory surgical procedures were infrequent (1.7%). CONCLUSION: The frequency of perioperative complications in children and adults who have congenital heart disease and undergo noncardiac surgical procedures and anesthesia is low. Patients who have pulmonary hypertension, congestive heart failure, or cyanosis and children with congenital heart disease who are younger than 2 years of age have an increased frequency of perioperative morbidity.

Adolescent↗
PubMed1997

Effect of sucralfate and basic fibroblast growth factor on fibrovascular ingrowth into hydroxyapatite and porous polyethylene alloplastic implants using a novel rabbit model.

This study investigated the effects of sucralfate and basic fibroblast growth factor (bFGF) on fibrovascular ingrowth into porous implant materials. Seven white female New Zealand rabbits underwent bilateral abdominal incisions through which porous orbital spherical or and disc-shaped implants were inserted between their abdominal muscles. Eighty hydroxyapatite (HA) and porous polyethylene (PP) implants, each material of different pore sizes, were implanted. These implants were either uncoated or coated with suspensions of polyhydroxymethylmethacrylate (hydron); hydron and sucralfate; or hydron, sucralfate, and bFGF. Implants were harvested after 1, 3, or 6 weeks. Observers classified the extent of fibrovascular ingrowth in a blind manner using light microscopy. All discs and spheres showed fibrovascular ingrowth; at 6 weeks, almost all implants were fully vascularized. Although demonstrating different degrees of fibrovascular maturity, all 3- and 6-week discs showed complete cellular ingrowth. Overall, the most extensive and mature fibrovascularization was found in HA implants, regardless of shape, duration of implantation, or angiogenic enhancing agent used. Thus, this study indicates that fibrovascular ingrowth into porous implants is more greatly affected by implant porosity and composition than by addition of angiogenic enhancing agents. Further in vivo study, using other potential angiogenesis-promoting agents as well as implants with different pore characteristics, is warranted using this reliable and predictable animal model.

Abdominal Muscles↗
PubMed1997

Outcomes of patients with no laboratory assessment before anesthesia and a surgical procedure.

OBJECTIVE: To estimate the frequency of perioperative morbidities in patients who underwent anesthesia and a surgical procedure with no preoperative laboratory testing. MATERIAL AND METHODS: We conducted an electronic database search of medical records of 56,119 patients who underwent surgical or diagnostic procedures and anesthesia at Mayo Clinic Rochester in 1994 and found 5,120 who had no laboratory tests done within 90 days before the procedure. From this group, we randomly selected 1,044 patients (87 from each month) to document the absence of preoperative tests, the presence of preexisting disease (by organ system), the type of anesthetic agent, and the outcomes and tests intraoperatively and postoperatively. RESULTS: The 1,044 patients ranged in age from 0 to 95 years (median age, 21). No deaths or major perioperative morbidities occurred (0.0%; exact 95% confidence interval, 0.00 to 0.35%). Although 10 patients underwent blood typing and screening for antibodies immediately preoperatively, no blood transfusions were necessary. Intraoperatively, 17 laboratory tests and 1 electrocardiogram were obtained, and 3 results were abnormal. Postoperatively, 42 blood tests and 2 electrocardiographic procedures were performed. Five of the 42 blood tests showed abnormal results (hemoglobin levels in 3, serum sodium in 1, and arterial blood gases in 1). One electrocardiogram showed normal findings, and the other revealed normal results except for premature ventricular contractions. No laboratory test done intraoperatively or postoperatively was found to change surgical or medical management substantially. One patient who had unanticipated blood loss during an outpatient procedure was admitted to the hospital for observation. CONCLUSION: All 1,044 patients, 97% of whom were relatively healthy, with no recent laboratory testing safely underwent anesthesia and an operation. We conclude that patients who have been assessed by history and physical examination and determined to have no preoperative indication for laboratory tests can safely undergo anesthesia and operation with tests obtained only as indicated intraoperatively and post-operatively. Current anesthetic and medical practices rapidly identify perioperative indications for laboratory evaluation as they arise.

Adolescent↗
PubMed1996

Prior intra-operative hypotension is not a risk factor for development of Alzheimer's disease.

OBJECTIVE: A retrospective, population-based, case-control study was carried out to evaluate episodes of prior intra-operative hypotension as a potential risk factor for Alzheimer's disease (AD). METHODS: Patients were all incident cases of AD from 1975-1984 who resided for 40 years or more in Olmsted County prior to their onset of dementia (N = 252). One age and gender-matched control for each case was selected from all registrations for care at Mayo Clinic during the year of onset in the incident case. Each case and control group had 252 individuals. RESULTS: Of these, 27 cases and 32 controls had at least one ten minute or longer episode of intra-operative hypotension of a systolic blood pressure of less than 90 mm Hg prior to the year of onset of dementia in the matched AD patient. We did not find a significantly increased risk of AD for hypotensive episodes of less than 75 or 90 mm Hg. CONCLUSIONS: It is unlikely that intra-operative hypotensive events of this degree increase the risk of AD.

Alzheimer Disease↗
PubMed1996

Blood substitutes: fluids, drugs, or miracle solutions?

Oxygen-carrying volume-expanding solutions that can sustain life in the absence of red blood cells have been developed. Concerns about side effects, sources of hemoglobin, and the ultimate demonstration of efficacy will have to be satisfactorily addressed before anesthesiologists routinely administer such solutions in place of red cells during surgery.

Animals↗
PubMed1996

Mechanical significance of respiratory muscle activity in humans during halothane anesthesia.

BACKGROUND: Prior human studies have shown that halothane attenuates activity in the parasternal intercostal muscle and enhances phasic activity in respiratory muscles with expiratory actions. This expiratory muscle activity could contribute to reductions in the functional residual capacity produced by anesthesia. Termination of this activity could contribute to the maintenance of inspiratory rib cage expansion. The purpose of this study was to estimate in humans the mechanical significance of expiratory muscle activity during halothane anesthesia and to search for the presence of scalene muscle activity during halothane anesthesia that might contribute to inspiratory rib cage expansion. METHODS: Six subjects (3 males, 3 females) were studied while awake and during 1.2 MAC halothane anesthesia, both during quiet breathing and during carbon dioxide rebreathing. Respiratory muscle activity was measured using fine-wire electromyography electrodes. Chest wall configuration was determined using images of the thorax obtained by three-dimensional, fast computed tomography and respiratory impedance plethysmography. Functional residual capacity was measured by a nitrogen dilution technique. Measurements were obtained after paralysis with 0.1 mg/kg vecuronium and mechanical ventilation. RESULTS: Phasic inspiratory activity was present in the scalene muscle of four anesthetized subjects during quiet breathing and all anesthetized subjects during rebreathing. Phasic inspiratory activity was present in the parasternal intercostal muscle during halothane anesthesia in only the three female subjects and was enhanced by rebreathing; parasternal intercostal muscle activity was never present in anesthetized males. During anesthesia with quiet breathing, phasic expiratory activity was observed in the transversus abdominis muscles of only the three male subjects. Despite these differences in the pattern of respiratory muscle use, the pattern of chest wall responses to rebreathing was similar between males and females. When expiratory muscle activity was present, paralysis increased the end-expiratory thoracic volume by expanding the rib cage, demonstrating that this activity reduced thoracic volume in these subjects. Changes in thoracic blood volume were significant determinants of the change in functional residual capacity produced by paralysis. CONCLUSIONS: In humans anesthetized with 1.2 MAC end-tidal halothane, there are marked interindividual differences in respiratory muscle use during quiet breathing that may be related to sex; phasic inspiratory scalene muscle and parasternal intercostal muscle activity may contribute to inspiratory rib cage expansion in some subjects; and when present, expiratory muscle activity significantly constricts the rib cage and contributes to reductions in functional residual capacity caused by halothane anesthesia.

Adult↗
PubMed1996

Atelectasis and chest wall shape during halothane anesthesia.

BACKGROUND: Anesthesia produces atelectasis in the dependent areas of the lungs by mechanisms that remain unknown. It has been proposed that anesthesia produces a cephalad shift in the end-expiratory position of the diaphragm, which compresses the lungs and produces atelectasis. This study tested the hypothesis that the extent of atelectasis is correlated with the cephalad displacement of the dependent portion of the diaphragm produced by halothane anesthesia in healthy young human subjects. METHODS: Twelve volunteers (mean age 34 yr) were studied while awake and during approximately 1.2 minimum alveolar concentration halothane anesthesia. Chest wall configuration was determined using images of the thorax obtained by three-dimensional fast computed tomography. Functional residual capacity was measured by a nitrogen dilution technique. Measurements were performed during quiet breathing in all subjects and after paralysis with 0.1 mg/kg vecuronium and mechanical ventilation in six subjects. Atelectasis was assumed to be present in regions of the lung that showed radiographic attenuation values similar to solid organs such as the liver. RESULTS: Atelectasis in dependent lung regions was not apparent in scans performed while the subjects were awake. Anesthesia with spontaneous breathing increased the volume of atelectasis measured at end-expiration by more than 1 ml in 9 of 12 subjects. For all subjects, the volume of atelectasis was 29 +/- 10 ml (M +/- SE), representing 0.67 +/- 0.23% of the total thoracic volume. The distribution of atelectasis varied along the cephalocaudal axis, with less atelectasis in more cephalad transverse sections. Paralysis and mechanical ventilation significantly decreased the volume of atelectasis present at end-expiration. There was no correlation between the average amount of cephalad displacement of the most dependent region of the diaphragm and the amount of atelectasis, nor was there any correlation between the amount of atelectasis and anesthesia-induced changes in the end-expiratory position of any chest wall structure. CONCLUSIONS: The dependent lung atelectasis produced by halothane anesthesia does not appear to be related to changes in the position of any single chest wall structure in these healthy young subjects, but rather to an interaction of several factors that remain to be identified.

Adult↗
PubMed1996

Perioperative respiratory complications in patients with asthma.

BACKGROUND: Patients with asthma are thought to be at high risk for pulmonary complications to develop during the perioperative period, and these complications may lead to serious morbidity. Existing medical records were reviewed to determine the frequency of and risk factors for perioperative pulmonary complications in a cohort of residents of Rochester, Minnesota, who had asthma and who underwent anesthesia and surgery at the Mayo Clinic in Rochester. METHODS: Medical records were reviewed for all residents of Rochester, Minnesota, who were initially diagnosed as having definite asthma according to strict criteria from 1 January 1964 through 31 December 1983 who subsequently had at least one surgical procedure involving a general anesthetic or central neuroaxis block at the Mayo Clinic (n = 706). RESULTS: Bronchospasm was documented in the perioperative records of 12 patients (1.7% [exact 95% confidence interval, 0.9 to 3%]). Postoperative respiratory failure developed in one of these patients. Laryngospasm developed in two additional patients during operation. All episodes of bronchospasm and laryngospasm in the immediate perioperative period were treated successfully. No episodes of pneumothorax, pneumonia, or death in the hospital were noted. For univariate analysis, characteristics associated with complications included the recent use of antiasthmatic drugs, recent asthma symptoms, and recent therapy in a medical facility for asthma. Patients in whom complications developed were significantly older at diagnosis and at surgery. CONCLUSIONS: The frequency of perioperative bronchospasm and laryngospasm was surprisingly low in this cohort of persons with asthma. These complications did not lead to severe respiratory outcomes in most patients. The frequency of complications was increased in older patients and in those with active asthma.

Adolescent↗
PubMed1996

Human chest wall function during epidural anesthesia.

BACKGROUND: Although epidural anesthesia (EA) can significantly disrupt the function of the respiratory system, data concerning its effects on respiratory muscle activity and the resulting motion of the chest wall are scarce. This study aimed to determine the effects of lumbar EA on human chest wall function during quiet breathing. METHODS: Six persons were studied while awake and during mid-thoracic (approximately a T6 sensory level) and high (approximately a T1 sensory level) lumbar EA produced by either 2% lidocaine (two persons) or 1.5% etidocaine (four persons) with 1:200,000 epinephrine. Respiratory muscle activity was measured using fine-wire electromyography electrodes. Chest wall configuration during high EA was determined using images of the thorax obtained by three-dimensional, fast computed tomography. The functional residual capacity was measured using a nitrogen dilution technique. RESULTS: High EA abolished activity in the parasternal intercostal muscles of every participant but one, whereas the mean phasic activity of the scalene muscles was unchanged. High EA significantly decreased the inspiratory volume displacement of the rib cage compared with intact breathing but did not have a significant effect on diaphragm displacement. Therefore, high EA decreased the percentage contribution of rib cage expansion to inspiratory increases in thoracic volume (delta Vth) (from 27 +/- 2 [MSE] to 10 +/- 11% of delta Vth). Paradoxic rib cage motion during inspiration (i.e., a net inward motion during inspiration) developed in only one participant. High EA substantially increased the functional residual capacity (by 295 +/- 89 ml), with a significant net caudad motion of the end expiratory position of the diaphragm. In addition, high EA significantly decreased the volume of liquid in the thorax at end expiration in five of the six participants, a factor that also contributed to the increase in functional residual capacity in these persons. CONCLUSIONS: Rib cage expansion continues to contribute to tidal volume during high EA in most subjects, even when most of the muscles of the rib cage are paralyzed; the mean phasic electrical activity of unblocked respiratory muscles such as scalenes does not increase in response to rib cage muscle paralysis produced by EA; and high EA increases the functional residual capacity, an increase produced in most participants by a caudad motion of the diaphragm and a decrease in intrathoracic blood volume.

Adult↗
PubMed1996

Benign and malignant tumors of the orbital cavity including the lacrimal gland.

CT and MR imaging are the modalities of choice in the assessment of orbital neoplasia. When combined with the clinical history and examination, radiologic imaging can provide valuable information regarding tumor diagnosis. Imaging studies thus enable the clinician to delineate the extent of disease and plan the surgical approach for biopsy or excision. In some cases, serial orbital imaging is used to monitor for tumor growth or recurrence.

Adolescent↗
PubMed1995

Human chest wall function while awake and during halothane anesthesia. I. Quiet breathing.

BACKGROUND: Data concerning chest wall configuration and the activities of the major respiratory muscles that determine this configuration during anesthesia in humans are limited. The aim of this study was to determine the effects of halothane anesthesia on respiratory muscle activity and chest wall shape and motion during spontaneous breathing. METHODS: Six human subjects were studied while awake and during 1 MAC halothane anesthesia. Respiratory muscle activity was measured using fine-wire electromyography electrodes. Chest wall configuration was determined using images of the thorax obtained by three-dimensional fast computed tomography. Tidal changes in gas volume were measured by integrating respiratory gas flow, and the functional residual capacity was measured by a nitrogen dilution technique. RESULTS: While awake, ribcage expansion was responsible for 25 +/- 4% (mean +/- SE) of the total change in thoracic volume (delta Vth) during inspiration. Phasic inspiratory activity was regularly present in the diaphragm and parasternal intercostal muscles. Halothane anesthesia (1 MAC) abolished activity in the parasternal intercostal muscles and increased phasic expiratory activity in the abdominal muscles and lateral ribcage muscles. However, halothane did not significantly change the ribcage contribution to delta Vth (18 +/- 4%). Intrathoracic blood volume, measured by comparing changes in total thoracic volume and gas volume, increased significantly during inspiration both while awake and while anesthetized (by approximately 20% of delta Vth, P < 0.05). Halothane anesthesia significantly reduced the functional residual capacity (by 258 +/- 78 ml), primarily via an inward motion of the end-expiratory position of the ribcage. Although the diaphragm consistently changed shape, with a cephalad displacement of posterior regions and a caudad displacement of anterior regions, the diaphragm did not consistently contribute to the reduction in the functional residual capacity. Halothane anesthesia consistently increased the curvature of the thoracic spine measured in the saggital plane. CONCLUSIONS: The authors conclude that (1) ribcage expansion is relatively well preserved during halothane anesthesia despite the loss of parasternal intercostal muscle activity; (2) an inward displacement of the ribcage accounts for most of the decrease in functional residual capacity caused by halothane anesthesia, accompanied by changes in diaphragm shape that may be related to motion of its insertions on the thoracoabdominal wall; and (3) changes in intrathoracic blood volume constitute a significant fraction of delta Vth during tidal breathing.

Adult↗
PubMed1995

Human chest wall function while awake and during halothane anesthesia. II. Carbon dioxide rebreathing.

BACKGROUND: Changes in the distribution of respiratory drive to different respiratory muscles may contribute to respiratory depression produced by halothane. The aim of this study was to examine factors that are responsible for halothane-induced depression of the ventilatory response to carbon dioxide rebreathing. METHODS: In six human subjects, respiratory muscle activity in the parasternal intercostal, abdominal, and diaphragm muscles was measured using fine-wire electromyography electrodes. Chest wall motion was determined by respiratory impedance plethysmography. Electromyography activities and chest wall motion were measured during hyperpnea produced by carbon dioxide rebreathing while the subjects were awake and during 1 MAC halothane anesthesia. RESULTS: Halothane anesthesia significantly reduced the slope of the response of expiratory minute ventilation to carbon dioxide (from 2.88 +/- 0.73 (mean +/- SE) to 2.01 +/- 0.45 l.min-1.mmHg-1). During the rebreathing period, breathing frequency significantly increased while awake (from 10.3 +/- 1.4 to 19.7 +/- 2.6 min-1, P < 0.05) and significantly decreased while anesthetized (from 28.8 +/- 3.9 to 21.7 +/- 1.9 min-1, P < 0.05). Increases in respiratory drive to the phrenic motoneurons produced by rebreathing, as estimated by the diaphragm electromyogram, were enhanced by anesthesia. Anesthesia attenuated the response of parasternal electromyography and accentuated the response of the transversus abdominis electromyography to rebreathing. The compartmental response of the ribcage to rebreathing was significantly decreased by anesthesia (from 1.83 +/- 0.58 to 0.48 +/- 0.13 l.min-1.mmHg-1), and marked phase shifts between ribcage and abdominal motion developed in some subjects. However, at comparable tidal volumes, the ribcage contribution to ventilation was similar while awake and anesthetized in four of the six subjects. CONCLUSIONS: Halothane anesthesia enhances the rebreathing response of neural drive to the primary respiratory muscle, the diaphragm. These findings provide direct evidence that, at the dose examined in this study, halothane-induced respiratory depression is caused by alterations in the distribution and timing of neural drive to the respiratory muscles, rather than a global depression of respiratory motoneuron drive.

Adult↗
PubMed1995

Orbit and adnexal neoplasia.

This article reviews the major orbital and adnexal tumors and focuses on clinical diagnosis and management. It emphasizes recent reports and reviews. Orbital tumors can be divided into vascular, mesenchymal, neural, epidermal, lymphoid, and metastatic lesions. Although derived from similar elements, the tumors of the lacrimal gland and eyelid form a separate category. Within the realm of vascular tumors, this article reviews recent literature regarding the treatment of capillary hemangiomas. It summarizes important information concerning the treatment of rhabdomyosarcomas published during the preceding year. The article also reviews case reports and studies of orbital tumors derived from neural, epithelial, and lymphoid elements. It provides general information regarding orbital metastatic disease and presents several recent case reports on lacrimal and adnexal tumors.

Eyelid Neoplasms↗