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Biomedical subjects

Karl B Kern

Publications and source records attributed to Karl B Kern.

14 recordsLinked to original sources
PubMed2003

Effect of amiodarone on haemodynamics during cardiopulmonary resuscitation in a canine model of resistant ventricular fibrillation.

OBJECTIVE: Amiodarone has been shown to be superior to both placebo and lidocaine in improving survival to hospital admission for victims of out-of-hospital refractory ventricular fibrillation. Concern had been expressed about the known vasodilatatory effects of amiodarone if given without precedent vasoconstrictive medications. The haemodynamic effects of intravenous amiodarone administered during ongoing CPR have not been systemically investigated. Our intention was to verify if amiodarone alone produced significantly lower resuscitation haemodynamics than did either adrenaline (epinephrine) alone or the combination of amiodarone and adrenaline. DESIGN: Prospective, randomized, comparative study. SETTING: Research laboratory of a medical school. SUBJECTS: Thirty mongrel dogs. INTERVENTIONS: After 8 min of untreated VF, defibrillation was attempted once at 3 J/kg and external chest compressions and ventilation started. Those animals resistant to the defibrillation attempt were randomized, ten to an adrenaline (0.02 mg/kg) group, ten to an amiodarone (5 mg/kg) group, and ten to a group receiving a combination of both drugs. MEASUREMENTS AND MAIN RESULTS: Aortic systolic and diastolic, and coronary perfusion pressures were all significantly lower in the group receiving amiodarone alone than in the other two groups. Amiodarone combined with adrenaline produced pressures during CPR similar to adrenaline alone. CONCLUSION: Amiodarone can be safely administered simultaneously in combination with adrenaline and such a combination results in similar haemodynamic support as adrenaline alone. Amiodarone administered alone produces significantly lower coronary perfusion pressure than when combined with adrenaline.

Amiodarone↗
PubMed2003

Cardiopulmonary Resuscitation Guidelines 2000 update: what's happened since?

PURPOSE OF REVIEW: To examine the literature for new resuscitation science since the publication of the Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiac Care. RECENT FINDINGS: The two and a half years since the publication of the Guidelines 2000 have seen the advent of a number of new and important resuscitation studies. Such studies highlight the importance of simplification of cardiopulmonary resuscitation techniques and guidelines, including the elimination of the layperson pulse check and the need for a simple form of basic life support cardiopulmonary resuscitation that decreases interruptions of chest compressions. Automatic external defibrillators, even in the hands of nontraditional first responders, are effective and safe. A second prospective, randomized clinical trial of amiodarone for refractory ventricular fibrillation has again shown positive results in improving survival to hospital admission. Finally, mild hypothermia appears to be the first effective therapy at decreasing central nervous system injury when administered after resuscitation. SUMMARY: In this report, we review these new studies and discuss how they corroborate or alter the published 2000 guidelines.

Amiodarone↗
PubMed2002

Importance of continuous chest compressions during cardiopulmonary resuscitation: improved outcome during a simulated single lay-rescuer scenario.

BACKGROUND: Interruptions to chest compression-generated blood flow during cardiopulmonary resuscitation (CPR) are detrimental. Data show that such interruptions for mouth-to-mouth ventilation require a period of "rebuilding" of coronary perfusion pressure to obtain the level achieved before the interruption. Whether such hemodynamic compromise from pausing to ventilate is enough to affect outcome is unknown. METHODS AND RESULTS: Thirty swine (weight 35 +/- 2 kg) underwent 3 minutes of untreated ventricular fibrillation before 12 minutes of basic life support CPR. Animals were randomized to receive either standard airway (A), breathing (B), and compression (C) CPR with expired-gas ventilation in a 15:2 compression-to-ventilation ratio or continuous chest compression CPR. Those randomized to the standard 15:2 group had no chest compressions for a period of 16 seconds each time the 2 ventilations were delivered. Defibrillation was attempted at 15 minutes of cardiac arrest. All resuscitated animals were supported in an intensive care environment for 1 hour, then in a maintenance facility for 24 hours. The primary end point of neurologically normal 24-hour survival was significantly better in the experimental group receiving continuous chest compression CPR (12 of 15 versus 2 of 15; P<0.0001). CONCLUSIONS: Mouth-to-mouth ventilation performed by single layperson rescuers produces substantial interruptions in chest compression-supported circulation. Continuous chest compression CPR produces greater neurologically normal 24-hour survival than standard ABC CPR when performed in a clinically realistic fashion. Any technique that minimizes lengthy interruptions of chest compressions during the first 10 to 15 minutes of basic life support should be given serious consideration in future efforts to improve outcome results from cardiac arrest.

Animals↗
PubMed2002

Optimizing ventilation in conjunction with phased chest and abdominal compression-decompression (Lifestick) resuscitation.

The best method for employment of phased chest and abdominal compression-decompression (Lifestick) cardiopulmonary resuscitation (CPR) has yet to be determined. Of particular concern with using this technique is the combining of ventilation with the phased compressions and decompressions. Twenty domestic swine (50+/-1 kg) were equally divided into four groups. Following 10 min of untreated VF, CPR was begun. Group 1 received Lifestick (LS) CPR with only passive ventilation ('passive'); Group 2 received LS-CPR with synchronized positive pressure ventilations (ppv) at a chest compression ratio of 15:2 (15:2 S); Group 3 had LS-CPR with synchronized ppv at 5:1 (5:1 S); and Group 4 received LS-CPR with asynchronous ppv at 5:1 (5:1 A). Endpoints included hemodynamics, blood gases, minute ventilation, and 24 h outcome. Asynchronous ventilation (5:1 A) had significantly worse hemodynamics including aortic and right atrial systolic, aortic diastolic, and coronary perfusion pressures than the other groups (P<0.05). Passive ventilation had the poorest arterial and mixed venous blood gases (P<0.05), but did not differ from 15:2 S in minute ventilation produced (8 vs 10 l/min). No differences in outcome were seen. The ventilation technique combined with LS-CPR can make a significant difference in hemodynamics as well as ventilation. Optimizing other forms of basic and advanced cardiac life support through different ventilation methods deserves new consideration, including a re-examination of the current single rescuer recommendation of a 15:2 ratio. Optimal ventilation strategy when using the LS device at 60 compressions per min appears to be 5:1 S. Such data is important for conducting clinical trials with this new CPR adjunct.

Abdomen↗
PubMed2002

Trials of teaching methods in basic life support (3): comparison of simulated CPR performance after first training and at 6 months, with a note on the value of re-training.

A randomised controlled trial comparing staged teaching of cardiopulmonary resuscitation (CPR) with conventional training provided the additional opportunity to investigate skill acquisition and retention in those attending conventional CPR classes. All subjects were tested immediately after their first instruction period and again at 6-9 months at an unheralded home visit. We were able to assess how far performance was related to poor acquisition of skills and how far it was related to skill decay. Out of 262 subjects who were randomised to receive conventional CPR instruction, 166 were available for home testing at 6-9 months. An invitation to attend for re-training had been accepted by 39 of them. The remaining 127 who attended only a single class comprise the principal study group, with additional comparative observations on the smaller re-trained cohort. Important failings were observed in the acquisition of skills in all modalities tested after the initial instruction. These were particularly marked in skills related to ventilation. Immediately after a class, 68% of trainees performed an effective check of breathing, but only 33% opened the airway as taught and no more than 18% provided an ideal ventilation volume. The technique of chest compression was also less than ideal. Although 80% of subjects placed their hands in an acceptable position, compression to an adequate depth and an adequate rate of compression were achieved by 54 and 63%, respectively. Seventy-eight percent demonstrated a careful approach, and 46% remembered to call for help. A carotid pulse check was simulated by 61% of trainees. When tested 6-9 months later, skill deterioration from this baseline was observed in all modalities tested except for the ventilation volume. The skill decay was significant (P<0.05) for the careful approach, performing an effective breathing check, the carotid pulse check, placing the hands in an acceptable position for chest compression, and compressing at an optimal rate. The minority who attended for re-training showed a trend to protection against skill decay for seven of the ten variables, compared with those who had attended only one training session. This improvement was significant for only two of them, but all were relatively small with limited practical value. Many who attend conventional CPR classes fail to acquire the necessary skills, and the skills that are acquired decline appreciably over the subsequent 6-9 months. The value of conventional re-training was modest in this study of community volunteers.

Adult↗
PubMed2002

Optimum compression to ventilation ratios in CPR under realistic, practical conditions: a physiological and mathematical analysis.

OBJECTIVE: To develop and evaluate a practical formula for the optimum ratio of compressions to ventilations in cardiopulmonary resuscitation (CPR). The optimum value of a variable is that for which a desired result is maximized. Here the desired result is assumed to be either oxygen delivery to peripheral tissues or a combination of oxygen delivery and waste product removal. METHOD: Equations describing oxygen delivery and blood flow during CPR as functions of the number of compressions and the number of ventilations delivered over time were developed from principles of classical physiology. These equations were solved explicitly in terms of the compression/ventilation ratio and evaluated for a wide range of conditions using Monte Carlo simulations. RESULTS: As the compression to ventilation ratio was increased from 0 to 50 or more, both oxygen delivery and the combination of oxygen delivery with blood flow increased to maximum values and then gradually declined. For variables typical of standard CPR as taught and specified in international guidelines, maximum values occurred at compression/ventilation ratios near 30:2. For variables typical of actual lay rescuer performance in the field, maximal values occurred at compression/ventilation ratios near 60:2. CONCLUSION: Current guidelines overestimate the need for ventilation during standard CPR by two to four-fold. Blood flow and oxygen delivery to the periphery can be improved by eliminating interruptions of chest compression for these unnecessary ventilations.

Blood Gas Analysis↗
PubMed2002

Treatment of post resuscitation myocardial dysfunction: aortic counterpulsation versus dobutamine.

BACKGROUND: Post resuscitation myocardial stunning is well described and recognized as a significant contributor to poor long-term outcome following cardiac arrest. Optimal strategies for treatment have not been determined. METHODS: Ten domestic swine (49+/-3 kg) underwent 15 min of untreated ventricular fibrillation before being successfully resuscitated. Left ventricular systolic and diastolic function was measured at pre-arrest baseline, at 30 min and at 6 h post resuscitation. Five animals were treated immediately after resuscitation with intra-aortic balloon counterpulsation (IABP) and five were given dobutamine (5 mcg/kg per min). RESULTS: No baseline differences were found. At 30 min post resuscitation pulmonary capillary wedge pressure and LVEDP were significantly higher (16+/-3 vs. 7+/-1 and 20+/-2 vs. 11+/-1 mmHg) while LV isovolumic relaxation ('Tau') was significantly longer (34+/-2 vs. 20+/-2 ms) in the IABP treated versus the dobutamine treated animals. Likewise, at 6 h post resuscitation LV ejection fraction was significantly less (21+/-6 vs. 39+/-4%), and LVEDP significantly higher (18 vs. 10 mmHg) in the IABP group. Heart rate was not different between the groups at any time post resuscitation. CONCLUSION: Dobutamine was superior to IABP for treatment of post resuscitation left ventricular systolic and diastolic dysfunction. The hypothesized advantage of IABP for treatment of post resuscitation myocardial stunning without excessively raising the heart rate like dobutamine was not realized.

Animals↗
PubMed2002

Post-resuscitation right ventricular dysfunction: delineation and treatment with dobutamine.

BACKGROUND: Left ventricular dysfunction after resuscitation from cardiac arrest has been well described. Treatment with dobutamine improves post-resuscitation left ventricular function. Right ventricular function following resuscitation has not been investigated. The purposes of this study were to examine right ventricular function following resuscitation and determine whether dobutamine would improve post-resuscitation right ventricular function. METHODS AND RESULTS: Right ventricular function was measured in 28 swine (29+/-1 kg) before and after resuscitation from 15 min of untreated ventricular fibrillation. Twelve animals received dobutamine at 10 mcg/kg/min while 16 animals served as untreated controls. Among controls, right ventricular dysfunction post-resuscitation was demonstrated by a decrease in right ventricular ejection fraction and an increase in right ventricular end-diastolic pressure. Among animals treated with dobutamine, there was a significant improvement in right ventricular function post-resuscitation compared to untreated controls. CONCLUSIONS: This study establishes that right ventricular systolic and diastolic dysfunction does occur after prolonged cardiac arrest from ventricular fibrillation. Dobutamine can ameliorate post-resuscitation right ventricular dysfunction.

Animals↗
PubMed2002

Postresuscitation myocardial dysfunction.

Postresuscitation myocardial dysfunction is common after prolonged cardiac arrest and can have life-threatening consequences. Experimental data suggest that systolic and diastolic left ventricular function can be adversely effected following successful resuscitation. Such dysfunction can resolve and represents true global myocardial stunning. Identified factors contributing to postresuscitation myocardial dysfunction include prolonged CPR, use of vasoconstricting drugs, and high-energy defibrillation. Potential treatments include dobutamine, KATP channel activators, and 21-aminosteroids. In the author's efforts to improve long-term survival from cardiac arrest, more attention is needed to the postresuscitation period.

Animals↗
PubMed2002

Acute ischemic syndromes. Adjunctive therapy.

The acute coronary syndromes (ACS) represent a heterogeneous group of patients along a continuum of risk from unstable angina to non-ST-segment elevation myocardial infarction. ACS is a term that has been used to describe the constellation of clinical symptoms that represent acute myocardial ischemia. This article reviews the adjunctive medications that are used during emergency cardiovasculare care for the early management of patients experiencing the ACS. The adjunctive therapies are divided into early immediate treatment and then subsequent management in the acute care setting.

Acute Disease↗
PubMed2002

Survival and neurologic outcome after cardiopulmonary resuscitation with four different chest compression-ventilation ratios.

STUDY OBJECTIVE: The optimal ratio of chest compressions to ventilations during cardiopulmonary resuscitation (CPR) is unknown. We determine 24-hour survival and neurologic outcome, comparing 4 different chest compression-ventilation CPR ratios in a porcine model of prolonged cardiac arrest and bystander CPR. METHODS: Forty swine were instrumented and subjected to 3 minutes of ventricular fibrillation followed by 12 minutes of CPR by using 1 of 4 models of chest compression-ventilation ratios as follows: (1) standard CPR with a ratio of 15:2; (2) CC-CPR, chest compressions only with no ventilations for 12 minutes; (3) 50:5-CPR, CPR with a ratio of 50:5 compressions to ventilations, as advocated by authorities in Great Britain; and (4) 100:2-CPR, 4 minutes of chest compressions only followed by CPR with a ratio of 100:2 compressions to ventilations. CPR was followed by standard advanced cardiac life support, 1 hour of critical care, and 24 hours of observation, followed by a neurologic evaluation. RESULTS: There were no statistically significant differences in 24-hour survival among the 4 groups (standard CPR, 7/10; CC-CPR, 7/10; 50:5-CPR, 8/10; 100:2-CPR, 9/10). There were significant differences in 24-hour neurologic function, as evaluated by using the swine cerebral performance category scale. The animals receiving 100:2-CPR had significantly better neurologic function at 24 hours than the standard CPR group with a 15:2 ratio (1.5 versus 2.5; P =.007). The 100:2-CPR group also had better neurologic function than the CC-CPR group, which received chest compressions with no ventilations (1.5 versus 2.3; P =.027). Coronary perfusion pressures, aortic pressures, and myocardial and kidney blood flows were not significantly different among the groups. Coronary perfusion pressure as an integrated area under the curve was significantly better in the CC-CPR group than in the standard CPR group (P =.04). Minute ventilation and PaO (2) were significantly lower in the CC-CPR group. CONCLUSION: In this experimental model of bystander CPR, the group receiving compressions only for 4 minutes followed by a compression-ventilation ratio of 100:2 achieved better neurologic outcome than the group receiving standard CPR and CC-CPR. Consideration of alternative chest compression-ventilation ratios might be appropriate.

Animals↗
PubMed2002

Precountershock cardiopulmonary resuscitation improves ventricular fibrillation median frequency and myocardial readiness for successful defibrillation from prolonged ventricular fibrillation: a randomized, controlled swine study.

STUDY OBJECTIVE: After prolonged ventricular fibrillation (VF), precountershock cardiopulmonary resuscitation (CPR) will improve myocardial "readiness" for defibrillation compared with immediate defibrillation. METHODS: After 10 minutes of untreated VF, 32 swine (27+/-1 kg) were randomly assigned to receive immediate countershocks (DEFIB), CPR for 3 minutes followed by countershocks (CPR), or CPR for 3 minutes plus intravenous epinephrine followed by countershocks (CPR+EPI). VF waveform was evaluated by fast Fourier transformation. RESULTS: VF amplitude and median frequency by fast Fourier transformation decreased during the untreated VF interval in all groups, and the median frequency subsequently increased during each minute of precountershock CPR. Although the VF median frequency in the 3 groups did not differ after 10 minutes of untreated VF (8.9+/-0.8 Hz versus 8.4+/-0.5 Hz versus 7.3+/-0.5 Hz, respectively), immediately before the first shock the VF median frequency was much lower in the DEFIB group than in either the CPR or CPR+EPI groups (8.9+/-0.8 Hz versus 13.1+/-0.8 Hz versus 13.8+/-0.9 Hz, respectively; P <.01). None of the 10 animals in the DEFIB group attained return of spontaneous circulation after the first set of shocks versus 5 of 10 animals in the CPR group and 6 of 12 animals in the CPR+EPI group (DEFIB versus each CPR group; P <.05). Cardiac output 1 hour after resuscitation was substantially worse in the DEFIB group than in the CPR or CPR+EPI groups (74+/-7 mL/kg per minute versus 119+/-7 mL/kg per minute versus 104+/-15 mL/kg per minute; P <.05). CONCLUSION: Precountershock CPR can result in substantial physiologic benefits compared with immediate defibrillation in the setting of prolonged VF. Moreover, these benefits can be attained with or without the addition of intravenous epinephrine.

Animals↗