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Biomedical subjects

K B Kern

Publications and source records attributed to K B Kern.

At least 19 recordsLinked to original sources
PubMed2001

Adverse hemodynamic effects of interrupting chest compressions for rescue breathing during cardiopulmonary resuscitation for ventricular fibrillation cardiac arrest.

BACKGROUND: Despite improving arterial oxygen saturation and pH, bystander cardiopulmonary resuscitation (CPR) with chest compressions plus rescue breathing (CC+RB) has not improved survival from ventricular fibrillation (VF) compared with chest compressions alone (CC) in numerous animal models and 2 clinical investigations. METHODS AND RESULTS: After 3 minutes of untreated VF, 14 swine (32+/-1 kg) were randomly assigned to receive CC+RB or CC for 12 minutes, followed by advanced cardiac life support. All 14 animals survived 24 hours, 13 with good neurological outcome. For the CC+RB group, the aortic relaxation pressures routinely decreased during the 2 rescue breaths. Therefore, the mean coronary perfusion pressure of the first 2 compressions in each compression cycle was lower than those of the final 2 compressions (14+/-1 versus 21+/-2 mm Hg, P<0.001). During each minute of CPR, the number of chest compressions was also lower in the CC+RB group (62+/-1 versus 92+/-1 compressions, P<0.001). Consequently, the integrated coronary perfusion pressure was lower with CC+RB during each minute of CPR (P<0.05 for the first 8 minutes). Moreover, at 2 to 5 minutes of CPR, the median left ventricular blood flow by fluorescent microsphere technique was 60 mL. 100 g(-1). min(-1) with CC+RB versus 96 mL. 100 g(-1). min(-1) with CC, P<0.05. Because the arterial oxygen saturation was higher with CC+RB, the left ventricular myocardial oxygen delivery did not differ. CONCLUSIONS: Interrupting chest compressions for rescue breathing can adversely affect hemodynamics during CPR for VF.

Animals↗
PubMed2001

Randomised controlled trials of staged teaching for basic life support: 2. Comparison of CPR performance and skill retention using either staged instruction or conventional training.

Teaching CPR in stages is a strategy designed to improve skill acquisition and retention. This method has been compared with conventional teaching in a randomised trial involving 495 volunteers. The first ('bronze') stage was simplified by omitting ventilation and giving compressions in sets of 50 with pauses to open the victim's airway; in the second ('silver') stage ventilation was introduced in a ratio of 50 compressions to five breaths, and in the third ('gold') stage, the volunteers were converted to conventional CPR. 51% of those taught by this method reattended for the second ('silver') stage compared with 25% who were taught conventional CPR and advised to return for a revision session. 38% of the staged group reattended for the third ('gold') compared with 8% for the conventional group. Modest improvement in skill acquisition has earlier been reported for the 'bronze' stage teaching, and this has been followed by better performance in some of the components tested after the subsequent stages. Comparisons after the 'gold' stage were limited by the small numbers who reattended for a third session of conventional training, but no special difficulties were noted in changing the ratio of compressions to ventilation that was necessary to convert the staged training volunteers to conventional CPR. The increased number of compressions that can be achieved by teaching 'bronze' stage CPR with no ventilation was retained, to a lesser degree, when the 'silver' ratio of 50 compressions to five breaths was compared with the conventional 15:2 ratio. Our observations suggest that during the first critical 8 min of a resuscitation attempt, 58% more compressions might be delivered by using the 50:5 ratio - an increase that is likely to result in a significant augmentation of blood flow with important clinical implications. More comparative information will become available when the results of unannounced home testing are analysed.

Adult↗
PubMed2001

Prehospital use of minimally invasive direct cardiac massage (MID-CM): a pilot study.

BACKGROUND: Internal cardiac compressions are more efficient than closed chest compressions (CCC) in cardiac arrest (CA). AIM OF THE STUDY: To evaluate the prehospital feasibility of performing a new method of minimally invasive direct cardiac massage (MID-CM TheraCardia Inc.). METHODS: Prospective non-randomized open study, after ethical committee approval. Inclusion of 18-85 years old patients in witnessed CA if BLS>5 min and unsuccessful ACLS>20 min after CA. The MID-CM is an atraumatic manual cardiac pumping system deployed in the thoracic cavity through a small incision. Evaluation of: ease of insertion and performing MID-CM, complications, end-tidal CO(2) (PETCO(2)), non invasive arterial blood pressure (NIBP) and return of spontaneous circulation (ROSC). Values are mean+/-SD (min-max). RESULTS: Twenty-five patients included. Mean age 59+/-16 years (26-85); BLS started at 8+/-5 min (0-20), compressions started at 47+/-10 min (29-74) after CA. Dissection and insertion was fast and easy (<1 min). Deployment of the MID-CM was difficult in two patients because of pericardium adhesions and cardiomegaly. In six patients compressions were more difficult because of a 'stone heart' phenomenon. Compressions were possible during ambulance transport of four patients. There was a good palpable carotid pulse in all patients receiving internal compressions. There was a trend in increase of PETCO(2) compared to CCC. NIBP could be measured during MID-CM compressions in 9 patients (systolic>85 mmHg), never during CCC. Seven patients had a ROSC, but only four patients were admitted alive. There was no long term survival. One patient had a serious complication (heart rupture). DISCUSSION: Prehospital use of MID-CM is possible, but it is not comparable to any other resuscitation technique. Training of medical teams is mandatory to obtain good skills and to avoid complications. Further studies are necessary to evaluate efficiency and survival compared to closed chest compressions.

Adult↗
PubMed2001

Incidence of coronary-subclavian steal syndrome in patients undergoing noncardiac surgery.

OBJECTIVE: To identify the incidence of coronary-subclavian steal syndrome in patients undergoing noncardiac surgery. DESIGN: Prospective. SETTING: Veterans Affairs Medical Center and university-affiliated medical center. PARTICIPANTS: Adult patients with prior coronary artery bypass graft surgery and documented use of an internal mammary artery. INTERVENTIONS: Bilateral simultaneous brachial blood pressures were determined noninvasively. The presumptive diagnosis of ipsilateral subclavian artery stenosis and coronary-subclavian steal syndrome was made if the systolic blood pressure differential was >20 mmHg. MEASUREMENTS AND MAIN RESULTS: The presumptive diagnosis of ipsilateral subclavian artery stenosis based on a blood pressure differential was made in 6 of 86 (5%) patients screened. The diagnosis of coronary-subclavian steal syndrome was confirmed at cardiac catheterization by observing retrograde internal mammary artery flow in 3 patients or lack of internal mammary artery flow in 1 patient (3.4%). All 4 patients with angiographic confirmation had either angina or silent ischemia. Three patients had successful carotid subclavian bypass, and 1 patient refused surgery. Two patients had no evidence of myocardial ischemia and underwent their planned procedure without incident. CONCLUSION: Coronary-subclavian steal syndrome occurs with relative frequency in noncardiac surgery patients with prior coronary artery bypass graft surgery using internal mammary artery conduits. Bilateral blood pressure measurements should be routinely performed during the preoperative evaluation. A pressure differential >20 mmHg should suggest the possibility of coronary-subclavian steal syndrome.

Aged↗
PubMed2000

Endothelin-1 vasoconstriction during swine cardiopulmonary resuscitation improves coronary perfusion pressures but worsens postresuscitation outcome.

BACKGROUND: Vasoconstriction during cardiopulmonary resuscitation (CPR) improves coronary perfusion pressure (CPP) and thereby outcome. The combination of endothelin-1 (ET-1) plus epinephrine improved CPP during CPR compared with epinephrine alone in a canine cardiac arrest model. The effect of the combination on outcome variables, such as successful resuscitation and survival, has not been investigated. METHODS AND RESULTS: Twenty-seven swine were randomly provided with 1 mg epinephrine (Epi group) or 1 mg epinephrine plus 0.1 mg ET-1 (ET-1 group) during a prolonged ventricular fibrillatory cardiac arrest. ET-1 resulted in substantially superior aortic relaxation pressure and CPP during CPR. These hemodynamic improvements tended to increase initial rates of restoration of spontaneous circulation (8 of 10 versus 8 of 17, P=0.12). However, continued intense vasoconstriction from ET-1 led to higher aortic diastolic pressure and very narrow pulse pressure after resuscitation. The mean pulse pressure 1 hour after resuscitation was 7+/-8 mm Hg with ET-1 versus 24+/-1 mm Hg with Epi, P<0.01. Most importantly, the postresuscitation mortality was dramatically higher in the ET-1 group (6 of 8 versus 0 of 8 in the Epi group, P<0.01). CONCLUSIONS: These data establish that administration of ET-1 during CPR can result in worse postresuscitation outcome. The intense vasoconstriction from ET-1 improved CPP during CPR but had detrimental effects in the postresuscitation period.

Animals↗
PubMed2000

"Bystander" chest compressions and assisted ventilation independently improve outcome from piglet asphyxial pulseless "cardiac arrest".

BACKGROUND: Bystander cardiopulmonary resuscitation (CPR) without assisted ventilation may be as effective as CPR with assisted ventilation for ventricular fibrillatory cardiac arrests. However, chest compressions alone or ventilation alone is not effective for complete asphyxial cardiac arrests (loss of aortic pulsations). The objective of this investigation was to determine whether these techniques can independently improve outcome at an earlier stage of the asphyxial process. METHODS AND RESULTS: After induction of anesthesia, 40 piglets (11.5+/-0.3 kg) underwent endotracheal tube clamping (6.8+/-0.3 minutes) until simulated pulselessness, defined as aortic systolic pressure <50 mm Hg. For the 8-minute "bystander CPR" period, animals were randomly assigned to chest compressions and assisted ventilation (CC+V), chest compressions only (CC), assisted ventilation only (V), or no bystander CPR (control group). Return of spontaneous circulation occurred during the first 2 minutes of bystander CPR in 10 of 10 CC+V piglets, 6 of 10 V piglets, 4 of 10 CC piglets, and none of the controls (CC+V or V versus controls, P<0.01; CC+V versus CC and V combined, P=0.01). During the first minute of CPR, arterial and mixed venous blood gases were superior in the 3 experimental groups compared with the controls. Twenty-four-hour survival was similarly superior in the 3 experimental groups compared with the controls (8 of 10, 6 of 10, 5 of 10, and 0 of 10, P<0.05 each). CONCLUSIONS: Bystander CPR with CC+V improves outcome in the early stages of apparent pulseless asphyxial cardiac arrest. In addition, this study establishes that bystander CPR with CC or V can independently improve outcome.

Animals↗
PubMed2000

Randomised controlled trials of staged teaching for basic life support. 1. Skill acquisition at bronze stage.

We have investigated a method of teaching community CPR in three stages instead of in a single session. These have been designated bronze, silver, and gold stages. The first involves only opening of the airway and chest compression with back blows for choking, the second adds ventilation in a ratio of compressions to breaths of 50:5, and the third is a conversion to conventional CPR. In a controlled randomised trial of 495 trainees we compared the performance in tests immediately after instruction of those who had received a conventional course and those who had had the simpler bronze level tuition. The tests were based on video recordings of simulated resuscitation scenarios and the readouts from recording manikins. Differences occurred as a direct consequence of ventilation being required in one group and not the other, some variation probably followed from unforeseen minor changes in the way that instruction was given, whilst others may have followed from the greater simplicity in the new method of training. A careful approach was followed by slightly more trainees in the conventional group whilst appreciably more in the bronze group remembered to shout for help (44% vs. 71%). A clear advantage was also seen for bronze level training in terms of those who opened the airway as taught (35% vs. 56%), for checking breathing (66% vs. 88%), and for mentioning the need to phone for an ambulance (21% vs. 32%). Little difference was observed in correct or acceptable hand position between the conventional group who were given detailed guidance and the bronze group who were instructed only to push on the centre of the chest. The biggest differences related to the number of compressions given. The mean delay to first compression was 63 s and 34 s, and the mean duration of pauses between compressions was 16 s and 9 s, respectively. Average performed rates were similar in the two groups, but more in the conventional group compressed too slowly whereas more in the bronze group compressed too rapidly. Observations were made for only three cycles of compression, but extrapolating these to the 8 min often considered a watershed for chances of survival for victims of cardiac arrest, an average of 308 compressions would be expected from those using conventional CPR compared with 675 for those using bronze level CPR. The implications of this difference are discussed.

Adult↗
PubMed2000

Minimally invasive direct cardiac massage versus closed-chest cardiopulmonary resuscitation in a porcine model of prolonged ventricular fibrillation cardiac arrest.

Open chest cardiac massage has been shown to be superior to closed-chest cardiopulmonary resuscitation for both hemodynamics produced during resuscitation and ultimate resuscitation success. The inexperience of many rescuers with emergency thoracotomy, along with the associated morbidity contributes to the continued reluctance in the use of invasive cardiopulmonary resuscitation techniques. A device has been developed for performing 'minimally invasive' direct cardiac massage. This technique was compared to standard closed-chest CPR for resuscitation results in 20 swine during prolonged ventricular fibrillation cardiac arrest. Minimally invasive direct cardiac massage was superior to closed-chest CPR for return of spontaneous circulation (7/10 vs. 2/10; P<0.02) and coronary perfusion pressure at 30 min of CPR (17+/-9 vs. 6+/-6 mmHg; P<0.05). No significant injuries altering outcome were found with the invasive device. Throughout most of the time course of the study no significant differences in end-tidal expired carbon dioxide levels were noted. Nor were there any differences in 24-h survival. Improvements in assuring proper placement of the device on the epicardium should make this technique a potent advanced cardiac life support adjunct.

Analysis of Variance↗
PubMed2000

Differential effects of right versus left stellate ganglion block on left ventricular function in humans: an echocardiographic analysis.

STUDY OBJECTIVES: To evaluate the effects of unilateral stellate ganglion blockade on left ventricular function. DESIGN: Prospective cohort of patients with chronic regional pain syndrome type I and II of the upper extremity requiring therapeutic stellate ganglion blockade. SETTING: University-affiliated hospital. PATIENTS: Fifteen adult ASA physical status I and II patients with the diagnosis of chronic regional pain syndrome type I and II of the arm were studied. Right stellate ganglion block was performed in nine subjects and a left in six. INTERVENTIONS: Stellate ganglion block was performed with 10 mL of 1% plain Xylocaine. Transthoracic echocardiograms were performed immediately prior and 30 min following the block. MEASUREMENTS: Heart rate and blood pressure were monitored at regular intervals. Global systolic function was determined by calculating ejection fraction. Regional systolic motion was evaluated on the short axis and four-chamber views using the American Society of Echocardiography criteria. Diastolic function was assessed with pulsed-wave Doppler of the left ventricular outflow tract and the mitral valve. Data collected included isovolumic relaxation time and early and atrial velocity patterns. MAIN RESULTS: A successful stellate ganglion block was achieved in all patients. Blood pressure and heart rate were not significantly different during data collection. Patients who underwent a right stellate ganglion block showed no significant differences in systolic or diastolic function. Following a left stellate ganglion block, global and regional systolic function remained unchanged. Isovolumic relaxation time was increased but did not reach statistical significance (80 +/- 13 ms to 88 +/- 9 ms; p = 0.09). Left ventricular end-diastolic (LVEDV) and end-systolic volumes (LVESV) were significantly increased (LVEDV from 73 +/- 9 mL to 100 +/- 9 mL, p < 0.02; LVESV from 31 +/- 4 mL to 37 +/- 4 mL, p < 0.03). CONCLUSIONS: In patients without cardiovascular disease, unilateral denervation of the left ventricle after stellate ganglion block produces no clinical deleterious effects on left ventricular function.

Adult↗
PubMed2000

Cardiopulmonary resuscitation without ventilation.

Current resuscitation methods, although occasionally effective, rarely perform as well as initially anticipated. Some of the disappointment can be attributed to the difficulty of the task for many, including both professional and lay first responders. Significant attention has been paid recently to the need to simplify both the technique and the teaching of resuscitation. In considering simplification of the current resuscitation scheme, a logical start is an honest reappraisal of the importance and priorities of each of the once sacrosanct ABCs, specifically, establishment of an Airway, artificial Breathing (mouth-to-mouth breathing), and chest compressions for temporary Circulation. Experimental data continue to accumulate indicating that most important within this triad is circulation. Adequate oxygen exists within the blood during at least the first 10 mins of cardiac arrest. If circulation is provided to distribute such oxygen, no survival disadvantage results with chest compression-only basic life support (BLS) efforts. Even a totally occluded airway during the first 6 mins of cardiac arrest does not compromise survival if reasonable circulation is provided with chest compressions. Clinical studies support the same conclusion that what most influences survival in any BLS effort is circulation, not ventilation. Belgium investigators have shown equal survival rates among those treated with chest compressions plus ventilation and those who received chest compressions alone. Telephone dispatcher-guided BLS cardiopulmonary resuscitation (CPR) has likewise shown no survival disadvantage to chest compression-only CPR when compared with telephone-guided standard BLS CPR. Based on this reasoning, a new simplified BLS method has been proposed. "Staged" CPR consists of a strategy to initially teach laypersons a simplified approach to BLS, which requires only chest compressions and not mouth-to-mouth breathing. "Bronze" CPR, in which chest compression-only BLS is taught, was compared with the standard European Resuscitation Council BLS course for laypersons. Manikin "exit testing" at course completion has revealed significant advantages of the simplified approach compared with standard CPR courses for the lay public.

Animals↗
PubMed1999

Vasopressin versus epinephrine during cardiopulmonary resuscitation: a randomized swine outcome study.

In animal models, vasopressin improves short-term outcome after cardiopulmonary resuscitation (CPR) for ventricular fibrillation compared to placebo, and improves myocardial and cerebral hemodynamics during CPR compared to epinephrine. This study was designed to test the hypothesis that vasopressin would improve 24-h neurologically intact survival compared to epinephrine. After a 2-min untreated ventricular fibrillation interval followed by 6 min of simulated bystander CPR, 35 domestic swine (weight, 25+/-1 kg) were randomly provided with a single dose of vasopressin (20 U or approximately 0.8 U kg(-1) intravenously) or with epinephrine (0.02 mg kg(-1) intravenously every 5 min). Ten minutes after initial medication administration (18 min after induction of ventricular fibrillation), standard advanced life support was provided, starting with defibrillation. Animals that were successfully resuscitated received 1 h of intensive care support and were observed for 24 h. Coronary perfusion pressures were higher in the vasopressin group 2 and 4 min after vasopressin administration (28+/-2 versus 18+/-1 mm Hg, P<0.01, and 26+/-3 versus 18+/-2 mm Hg, P<0.05, respectively). The vasopressin group tended to be successfully defibrillated on the first attempt more frequently (8/18 versus 3/17, P = 0.15). Return of spontaneous circulation (ROSC) was attained in 12/18 (67%) vasopressin-treated pigs versus 8/17 (47%) epinephrine-treated pigs, P = 0.24. Twenty-four hour neurologically normal survival occurred in 11/18 (61%) versus 7/17 (41%), respectively, P = 0.24. In conclusion, vasopressin administration during CPR improved coronary perfusion pressure, but did not result in statistically significant outcome improvement.

Animals↗
PubMed1999

Simulated mouth-to-mouth ventilation and chest compressions (bystander cardiopulmonary resuscitation) improves outcome in a swine model of prehospital pediatric asphyxial cardiac arrest.

OBJECTIVE: To compare the efficacy of four methods of simulated single-rescuer bystander cardiopulmonary resuscitation (CPR) in a clinically relevant swine model of prehospital pediatric asphyxial cardiac arrest. DESIGN: Prospective, randomized study. SUBJECTS: Thirty-nine anesthetized domestic piglets. INTERVENTIONS: Asphyxial cardiac arrest was produced by clamping the endotracheal tubes of the piglets. For 8 mins of simulated bystander CPR, animals were randomly assigned to the following groups: group 1, chest compressions and simulated mouth-to-mouth ventilation (FI(O2) = 0.17, FI(CO2) = 0.04) (CC+V); group 2, chest compressions only (CC); group 3, simulated mouth-to-mouth ventilation only (V); and group 4, no CPR (control group). Standard advanced life support was then provided, simulating paramedic arrival. Animals that were successfully resuscitated received 1 hr of intensive care support and were observed for 24 hrs. MEASUREMENTS AND MAIN RESULTS: Electrocardiogram, aortic blood pressure, right atrial blood pressure, and end-tidal CO2 were monitored continuously until the intensive care period ended. Arterial and mixed venous blood gases were measured at baseline, 1 min after cardiac arrest, and 7 mins after cardiac arrest. Minute ventilation was determined during each minute of bystander CPR. Survival and neurologic outcome were determined. Twenty-four-hour survival was attained in eight of 10 group 1 (CC+V) piglets vs. three of 14 group 2 (CC) piglets (p < or = .01), one of seven group 3 (V) piglets (p < or = .05), and two of eight group 4 (control) piglets (p < or = .05). Twenty-four-hour neurologically normal survival occurred in seven of 10 group 1 (CC+V) piglets vs. one of 14 group 2 (CC) piglets (p < or = .01), one of seven group 3 (V) piglets (p < or = .05), and none of eight group 4 (control) piglets (p < or = .01). Arterial oxygenation and pH were markedly better during CPR in group 1 than in group 2. Within 5 mins of bystander CPR, six of 10 group 1 (CC+V) piglets attained sustained return of spontaneous circulation vs. only two of 14 group 2 (CC) piglets and none of the piglets in the other two groups (p < or = .05 for all groups). CONCLUSIONS: In this pediatric asphyxial model of prehospital single-rescuer bystander CPR, chest compressions plus simulated mouth-to-mouth ventilation improved systemic oxygenation, coronary perfusion pressures, early return of spontaneous circulation, and 24-hr survival compared with the other three approaches.

Analysis of Variance↗