Biomedical subjects

M L Callaham

Publications and source records attributed to M L Callaham.

25 records · Page 2Linked to original sources

PubMed1994

Evaluation of active compression-decompression CPR in victims of out-of-hospital cardiac arrest.

OBJECTIVE--Active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) appears to improve ventilation and coronary perfusion when compared with standard CPR. The objective was to evaluate potential benefits of this new CPR technique in patients with out-of-hospital cardiac arrest in St Paul, Minn. DESIGN--Ten-month, prospective, randomized parallel-group design. SETTING--St Paul, Minn, population 270,000. PATIENTS--All normothermic victims of nontraumatic cardiac arrest older than 8 years who received CPR. MAIN OUTCOME MEASURES--Return of spontaneous circulation, admission to the intensive care unit (ICU), return of baseline neurological function (alert and oriented to person, place, and time), survival to hospital discharge, survival to hospital discharge with return of baseline neurological function, and complications. RESULTS--Seventy-seven patients received standard CPR and 53 patients received ACD CPR. The mean emergency medical services call response interval was less than 3.5 minutes. When all patients were considered, a higher percentage of ACD CPR patients had a return of spontaneous circulation and were admitted to the ICU vs standard CPR (45% vs 31%, and 40% vs 26%, respectively), but these trends were not statistically significant (P < .10 and P < .10). No statistically significant differences were found between hospital discharge rates (12 [23%] of 53 for ACD CPR vs 13 [17%] of 77 for standard CPR), return to baseline neurological function (10 [19%] of 53 for ACD CPR vs 13 [17%] of 77 for standard CPR), or return to baseline neurological function at hospital discharge (nine [17%] of 53 for ACD CPR vs 12 [16%] of 77 for standard CPR). Return of spontaneous circulation, ICU admission, and neurological recovery in both CPR groups were highly correlated with downtime (time from collapse to emergency medical system personnel arrival to the scene in witnessed arrests). With less than 10 minutes' downtime, survival to the ICU was 59% (19/32) with ACD CPR and 33% (16/49) with standard CPR (P < .02), return to baseline neurological function was 31% (10/32) with ACD CPR and 20% (10/49) with standard CPR (P = .27), and hospital discharge rate was 38% (12/32) with ACD CPR and 20% (10/49) with standard CPR (P = .17). Complication rates in patients admitted to the hospital were similar in both groups. CONCLUSIONS--This study demonstrates that ACD CPR appears to be more effective than standard CPR in a well-defined subset of victims of out-of-hospital cardiac arrest during the critical early phases of resuscitation. Based on this study, a larger study should be performed to evaluate the potential long-term benefits of ACD CPR.

Aged↗

PubMed1993

Physiology of blood flow during cardiopulmonary resuscitation. A transesophageal echocardiographic study.

BACKGROUND: There are two competing theories of the mechanism of blood flow during cardiopulmonary resuscitation. The "cardiac pump" theory postulates that blood flows because the heart is squeezed between the sternum and the spine. The "thoracic pump" theory postulates that blood flows from the thorax because intrathoracic pressure exceeds extrathoracic vascular pressure and that flow is restricted to the venous-to-arterial direction because of venous valves that prevent retrograde flow at the thoracic inlet. To determine which mechanism is operative during actual cardiopulmonary resuscitation, 20 patients were imaged with transesophageal echocardiography during resuscitation. METHODS AND RESULTS: Transesophageal two-dimensional and pulse Doppler echocardiography was begun within 7 minutes of initiation of cardiopulmonary resuscitation. In the 18 patients who could be analyzed, the mitral valve opened during the release phase (diastole) and closed during the compression phase (systole) of cardiopulmonary resuscitation. Mitral velocity-time integral measured 8 +/- 3 cm during diastole. There was compression of right and left ventricular cavities with significant reduction in measured left ventricular volume during cardiopulmonary resuscitation. In five patients, mitral regurgitation was present. CONCLUSIONS: Transesophageal echocardiography performed during actual cardiopulmonary resuscitation showing mitral valve opening during cardiac release, reduction of ventricular cavity size with compression, and atrioventricular regurgitation support the cardiac pump theory of cardiopulmonary resuscitation. This study demonstrates the feasibility and usefulness of transesophageal echocardiography during cardiopulmonary resuscitation.

Adult↗

PubMed1992

Active compression-decompression resuscitation: a novel method of cardiopulmonary resuscitation.

Chest compression is an important part of cardiopulmonary resuscitation (CPR), but it only aids circulation during a portion of the compression cycle and has been shown to only minimally increase blood flow to vital organs. The purpose of this study was to quantitate the short-term hemodynamic effects of CPR with a hand-held suction device that incorporates both active compression and decompression of the chest. The suction device was applied to the middle of the sternum and compared with standard manual CPR in eight nonventilated anesthetized dogs. Coronary perfusion pressure, systolic and diastolic aortic pressures, right atrial diastolic pressure, and the velocity time integral (an analog of cardiac output), which were obtained by means of transesophageal pulsed wave Doppler echocardiography from the main pulmonary artery, were measured every 30 seconds during CPR. Minute ventilation was measured over the last minute of each CPR technique. Both active compression-decompression CPR and standard CPR were sequentially performed for 2 minutes in random order 30 seconds after induced ventricular fibrillation. The CPR techniques consisted of 100 compressions per minute, with a compression depth of 1.5 to 2 inches and a 50% duty cycle. Coronary perfusion pressure, velocity time integral (cardiac output analog), minute ventilation, and systolic arterial pressure were all significantly improved by active compression-decompression CPR when compared with standard CPR. We conclude that active compression-decompression CPR is a simple technique that appears to improve coronary perfusion pressure, systolic arterial pressure, cardiac output, and minute ventilation in nonventilated animals when compared with standard CPR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Prophylaxis with zidovudine (AZT) after exposure to human immunodeficiency virus: a brief discussion of the issues for emergency physicians.

Sound scientific information with which to determine the true efficacy of zidovudine for prophylaxis will probably not be available soon. Physicians should educate themselves thoroughly on the issues. It is highly recommended that thoughtful discussions of the issue of transmission of HIV from health personnel to patients as well as the key articles cited in this discussion be read. The details of a prophylaxis program, including laboratory evaluation, are provided in an article by Henderson and Gerberding and in greater detail in the article by Go et al. (Health care workers exposed to HIV can be enrolled in the Centers for Disease Control surveillance program by calling 404/639-1644. To enroll persons with large exposures to HIV in the zidovudine prophylaxis study, call 800/537-9978.) ED directors should work closely with local infectious disease specialists to determine if such a program is needed and how to implement it. Further details regarding the implementation of a prophylaxis program should be obtained from the literature and the Centers for Disease Control. All of the details of such a program should be worked out well in advance so that knowledgeable and immediate counseling can be provided to health care workers within one or two hours of exposure. Highly qualified individuals and institutions vary in their recommendations on prophylaxis, although most provide them. Zidovudine probably does not provide very effective protection, if it provides any. However, the medical, social, and economic consequences of HIV infection of health care workers are very real, and the serious irreversible adverse effects of zidovudine are very rare.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Effect of povidone-iodine and saline soaking on bacterial counts in acute, traumatic, contaminated wounds.

It is common practice to soak acute traumatic wounds in dilute povidone-iodine solution before definitive wound cleaning and debridement. The effectiveness of soaking wounds is unknown. Using quantitative wound bacterial counts as a measure of efficacy, we compared wounds soaked in 1% povidone-iodine solution or in normal saline with wounds receiving no treatment. Adult patients were eligible for the study if they were seen in the emergency department with visibly contaminated traumatic wounds within 12 hours of injury. Patients were excluded if they refused consent, were allergic to iodine, or had taken antibiotics within five days; if the wound did not require debridement; if the wound had been previously cleaned; or if subsequent cultures were sterile. Thirty-three heavily contaminated acute traumatic wounds in 29 patients were included in the study. Wounds were randomly assigned to one of three groups. Tissue samples were taken before and after a ten-minute period of soaking in either povidone-iodine or saline; controls were covered with gauze during the ten-minute period. The mean bacterial count per gram of tissue decreased 6.4 x 10(5) (standard deviation, 1.68 x 10(6)) after no soak, increased 3.39 x 10(7) (1.05 x 10(8)) after saline soak, and decreased 9.19 x 10(6) (1.72 x 10(7)) after povidone-iodine soak. Wounds with counts of less than 10(5) bacteria/g tissue are unlikely to become infected. Multiple regression analysis was used to analyze the changes in bacterial count after treatment as a function of experimental group and initial bacterial count. There was no significant difference between the control and povidone-iodine groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗

PubMed1990

High-dose epinephrine therapy and other advances in treating cardiac arrest.

These discussions are selected from the weekly staff conferences in the Department of Medicine, University of California, San Francisco. Taken from transcriptions, they are prepared by Homer A. Boushey, MD, Professor of Medicine, and Nathan M. Bass, MD, PhD, Associate Professor of Medicine, under the direction of Lloyd H. Smith, Jr, MD, Professor of Medicine and Associate Dean in the School of Medicine. Requests for reprints should be sent to the Department of Medicine, University of California, San Francisco, School of Medicine, San Francisco, CA 94143.

Animals↗

PubMed1978

Treatment of common dog bites: infection risk factors.

In a retrospective study of 106 patients with complete follow-up of dog bites treated in the emergency department the following factors greatly increased the risk of infection: age greater than 50 years, delay in seeking treatment, location on an upper extremity, and puncture wounds. Debridement and irrigation decreased the incidence of infection, and sutured wounds were not more likely to become infected than those left open. Prophylactic antibiotics provided no benefit in this series. In the literature, overall infection rates varied widely according to the various patient populations. Up to 50% of infections from dog bites are caused by pasturella multocida, and the remainder by a wide range of organisms, including streptococcus. Ninety-five percent of these organisms will be sensitive to penicillin.

Animals↗