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Biomedical subjects

R W Hilwig

Publications and source records attributed to R W Hilwig.

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↗
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

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↗
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↗
PubMed1998

Efficacy of chest compression-only BLS CPR in the presence of an occluded airway.

Reluctance of the lay public to perform bystander CPR is becoming an increasingly worrisome problem in the USA. Most bystanders who admit such reluctance concede that fear of contagious disease from mouth-to-mouth contact is what keeps them from performing basic life support. Animal models of prehospital cardiac arrest indicates that 24-h survival is essentially as good with chest compression-only CPR as with chest compressions and assisted ventilation. This simpler technique is an attractive alternative strategy for encouraging more bystander participation. Such experimental studies have been criticized as irrelevant however secondary to differences between human and porcine airway mechanics. This study examined the effect of chest compression-only CPR under the worst possible circumstances where the airway was totally occluded. After 6 min of either standard CPR including ventilation with a patent airway or chest compressions-only with a totally occluded airway, no difference in 24 h survival was found (10/10 vs. 9/10). As anticipated arterial blood gases were not as good, but hemodynamics produced were better with chest compression-only CPR (P < 0.05). Chest compression-only CPR, even with a totally occluded airway, is as good as standard CPR for successful outcome following 6.5 min of cardiac arrest. Such a strategy for the first minutes of cardiac arrest, particularly before professional help arrives, has several advantages including increased acceptability to the lay public.

Airway Obstruction↗
PubMed1997

Assisted ventilation during 'bystander' CPR in a swine acute myocardial infarction model does not improve outcome.

BACKGROUND: Mouth-to-mouth rescue breathing is a barrier to the performance of bystander cardiopulmonary resuscitation (CPR). We evaluated the need for assisted ventilation during simulated single-rescuer bystander CPR in a swine myocardial infarction model of prehospital cardiac arrest. METHODS AND RESULTS: Steel cylinders were placed in the mid left anterior descending coronary arteries of 43 swine. Two minutes after ventricular fibrillation, animals were randomly assigned to 10 minutes of hand-bag-valve ventilation with 17% oxygen and 4% carbon dioxide plus chest compressions (CC+V), chest compressions only (CC), or no CPR (control group). Standard advanced life support was then provided. Animals successfully resuscitated received 1 hour of intensive care support and were observed for 24 hours. Five of 14 CC animals, 3 of 15 CC+V animals, and 1 of 14 controls survived for 24 hours (CC versus controls, P=.07). Myocardial oxygen delivery and consumption were greater among surviving animals than nonsurvivors but did not differ between CC and CC+V animals. CONCLUSIONS: In this acute myocardial infarction model of prehospital single-rescuer bystander CPR, assisted ventilation did not improve outcome.

Animals↗
PubMed1997

Postresuscitation left ventricular systolic and diastolic dysfunction. Treatment with dobutamine.

BACKGROUND: Global left ventricular dysfunction after successful resuscitation is well documented and appears to be a major contributing factor in limiting long-term survival after initial recovery from out-of-hospital sudden cardiac death. Treatment of such postresuscitation myocardial dysfunction has not been examined previously. METHODS AND RESULTS: Systolic and diastolic parameters of left ventricular function were measured in 27 swine before and after successful resuscitation from prolonged ventricular fibrillation cardiac arrest. Dobutamine infusions (10 micrograms.kg-1.min-1 in 14 animals or 5 micrograms.kg-1.min-1 in 5 animals) begun 15 minutes after resuscitation were compared with controls receiving no treatment (8 animals). The marked deterioration in systolic and diastolic left ventricular function seen in the control group after resuscitation was ameliorated in the dobutamine-treated animals. Left ventricular ejection fraction fell from a prearrest 58 +/- 3% to 25 +/- 3% at 5 hours after resuscitation in the control group but remained unchanged in the dobutamine (10 micrograms.kg-1.min-1) group (52 +/- 1% prearrest and 55 +/- 3% at 5 hours after resuscitation). Measurement of the constant of isovolumic relaxation of the left ventricle (tau) demonstrated a similar benefit of the dobutamine infusion for overcoming postresuscitation diastolic dysfunction. The tau rose in the controls from 28 +/- 1 milliseconds (ms) prearrest to 41 +/- 3 ms at 5 hours after resuscitation whereas it remained constant in the dobutamine-treated animals (31 +/- 1 ms prearrest and 31 +/- 5 ms at 5 hours after resuscitation). CONCLUSIONS: Dobutamine begun within 15 minutes of successful resuscitation can successfully overcome the global systolic and diastolic left ventricular dysfunction resulting from prolonged cardiac arrest and cardiopulmonary resuscitation.

Animals↗
PubMed1997

Assisted ventilation does not improve outcome in a porcine model of single-rescuer bystander cardiopulmonary resuscitation.

BACKGROUND: Mouth-to-mouth rescue breathing is a barrier to the performance of bystander cardiopulmonary resuscitation (CPR). We evaluated the need for assisted ventilation during simulated single-rescuer bystander CPR in a swine model of prehospital cardiac arrest. METHODS AND RESULTS: Five minutes after ventricular fibrillation, swine were randomly assigned to 8 minutes of hand-bag-valve ventilation with 17% oxygen and 4% carbon dioxide plus chest compressions (CC + V), chest compressions only (CC), or no CPR (control group). Standard advanced life support was then provided. Animals successfully resuscitated received 1 hour of intensive care support and were observed for 24 hours. All 10 CC animals, 9 of the 10 CC + V animals, and 4 of the 6 control animals attained return of spontaneous circulation. Five of the 10 CC animals, 6 of the 10 CC + V animals, and none of the 6 control animals survived for 24 hours (CC versus controls, P = .058; CC + V versus controls, P < .03). All 24-hour survivors were normal or nearly normal neurologically. CONCLUSIONS: In this model of prehospital single-rescuer bystander CPR, successful initial resuscitation, 24-hour survival, and neurological outcome were similar after chest compressions only or chest compressions plus assisted ventilation. Both techniques tended to improve outcome compared with no bystander CPR.

Animals↗
PubMed1996

Myocardial dysfunction after resuscitation from cardiac arrest: an example of global myocardial stunning.

OBJECTIVES: This study investigated the effect of prolonged cardiac arrest and subsequent cardiopulmonary resuscitation on left ventricular systolic and diastolic function. BACKGROUND: Cardiac arrest from ventricular fibrillation results in cessation of forward blood flow, including myocardial blood flow. During cardiopulmonary resuscitation, myocardial blood flow remains suboptimal. Once the heart is defibrillated and successful resuscitation achieved, reversible myocardial dysfunction, or "stunning," may occur. The magnitude and time course of myocardial stunning from cardiac arrest is unknown. METHODS: Twenty-eight domestic swine (26 +/- 1 kg) were studied with both invasive and noninvasive measurements of ventricular function before and after 10 or 15 min of untreated cardiac arrest. Contrast left ventriculograms, ventricular pressures, cardiac output, isovolumetric relaxation time (tau) and transthoracic Doppler-echocardiographic studies were obtained. RESULTS: Twenty-three of 28 animals were successfully resuscitated and postresuscitation data obtained. Left ventricular ejection fraction showed a significant reduction 30 min after resuscitation (p < 0.05). Regional wall motion analysis revealed diffuse, global left ventricular systolic dysfunction. Left ventricular end-diastolic pressure increased significantly in the postresuscitation period (p < 0.05). Isovolumetric relaxation time (tau) was significantly increased over baseline by 2 h after resuscitation (p < 0.05). Similar findings were noted with the Doppler-echocardiographic analysis, including a reduction in fractional shortening (p < 0.05), a reduction in mitral valve deceleration time (p < 0.05) and an increase in left ventricular isovolumetric relaxation time at 5 h after resuscitation (p < 0.05> By 24 h, these invasive and noninvasive variables of systolic and diastolic left ventricular function had begun to improve. At 48 h, all measures of left ventricular function had returned to baseline levels. CONCLUSIONS: Myocardial systolic and diastolic dysfunction is severe after 10 to 15 min of untreated cardiac arrest and successful resuscitation. Full recovery of this postresuscitation myocardial stunning is seen by 48 h in this experimental model of ventricular fibrillation cardiac arrest.

Animals↗
PubMed1996

Active compression-decompression versus standard cardiopulmonary resuscitation in a porcine model: no improvement in outcome.

Active compression-decompression cardiopulmonary resuscitation (CPR) is a new innovative basic life-support technique during which the anterior chest wall is actively decompressed by a suction device. CPR techniques were studied in 36 swine to test the hypothesis that active compression-decompression CPR improves coronary perfusion pressure, myocardial blood flow during CPR, and 24-hour survival. After 30 seconds of untreated ventricular fibrillation, CPR was begun and continued for 12.5 minutes by one of the three following methods: (1) active compression-decompression CPR with a suction device modified to include a precision force transducer; (2) standard CPR performed with a force transducer device; and (3) standard manual CPR performed without a force transducer device. CPR-generated coronary perfusion pressure, myocardial blood flow, and the force of compression were measured at 3 and 10 minutes of resuscitation effort. Initial return of spontaneous circulation, 24-hour survival, and trauma scores were also evaluated. Active compression-decompression CPR produced consistently better results than did standard CPR performed with a force transducer, but not better than standard CPR performed manually without a force transducer. The use of a force-measuring device with standard CPR may compromise hemodynamic response and outcome.

Animals↗
PubMed1996

A randomized, blinded trial of high-dose epinephrine versus standard-dose epinephrine in a swine model of pediatric asphyxial cardiac arrest.

OBJECTIVE: To determine whether high-dose epinephrine administration during cardiopulmonary resuscitation (CPR) in a swine pediatric asphyxial cardiac arrest model improves outcome (i.e., resuscitation rate, survival rate, and neurologic function) compared with standard-dose epinephrine. DESIGN: A randomized, blinded study. SETTING: A large animal cardiovascular laboratory at a university. SUBJECTS: Thirty domestic piglets (3 to 4 months of age) were randomized to receive standard-dose epinephrine (0.02 mg/kg) or high-dose epinephrine (0.2 mg/kg) during CPR after 10 mins of cardiac standstill with loss of aortic pulsation after endotracheal tube clamping. INTERVENTIONS: Two minutes of CPR were provided, followed by advanced pediatric life support. Successfully resuscitated animals were supported in an intensive care unit (ICU) setting for 2 hrs and then observed for 24 hrs. MEASUREMENTS AND MAIN RESULTS: Electrocardiogram, thoracic aortic blood pressure, and right atrial blood pressure were monitored continuously until the intensive care period ended. Survival rate and neurologic outcome were determined. Return of spontaneous circulation was obtained in 13 of 15 high-dose epinephrine piglets vs. ten of 15 standard-dose epinephrine piglets (p < .20). Four of 13 high-dose piglets died in the ICU period after initial resuscitation vs. 0 of ten standard-dose piglets (p < or = .05). Nine high-dose piglets survived 2 hrs vs. ten standard-dose piglets. Three piglets in each group survived for 24 hrs, but all were severely neurologically impaired. Two minutes after resuscitation, piglets treated with high-dose epinephrine had higher heart rates (210 +/- 24 vs. 189 +/- 40 beats/min, p < .05) and higher aortic diastolic pressures (121 +/- 39 vs. 74 +/- 40 mm Hg, p < .01). Within 10 mins of return of spontaneous circulation, severe tachycardia (> 240 beats/min) was more frequently noted in the high-dose group than in the standard-dose group (p < .05). All four high-dose piglets that died in the ICU period experienced ventricular fibrillation within 10 mins of return of spontaneous circulation. CONCLUSIONS: High-dose epinephrine did not improve 2-hr survival rate, 24-hr survival rate, or neurologic outcome. High-dose epinephrine resulted in severe tachycardia and hypertension immediately after resuscitation and in a higher mortality rate immediately after resuscitation.

Animals↗
PubMed1996

Initial end-tidal CO2 is markedly elevated during cardiopulmonary resuscitation after asphyxial cardiac arrest.

OBJECTIVES: To compare the initial end-tidal CO2 (PetCO2) during cardiopulmonary resuscitation in asphyxial versus ventricular fibrillatory cardiac arrest. DESIGN: A cohort study. SETTING: University research laboratory. SUBJECTS: Forty domestic piglets. INTERVENTIONS: Asphyxial cardiac arrest was produced by clamping the endotracheal tube in 20 piglets and was continued for 10 minutes after loss of aortic pulsations occurred. Ventricular fibrillation (VF) was induced by applying 60 Hz of alternating current via a pacing wire to the myocardium of the other 20 piglets, and continued for a 15-minute downtime. Cardiopulmonary resuscitation (CPR) was then provided to each group for two minutes, followed by standard advanced cardiac life support protocols. MEASUREMENTS AND MAIN RESULTS: All piglets were instrumented for continuous monitoring of PetCO2, electrocardiogram, central venous pressure, and aortic pressure. PetCO2 of the first breath of CPR was 91 +/- 20 mmHg in the asphyxial group versus 34 +/- 14 mmHg in the VF group (P < 0.001). The asphyxial group continued to exhibit significantly greater PetCO2 for the first five breaths of resuscitation, after which there were no differences. The coronary perfusion pressures during the first breaths of CPR did not differ between the two groups. High initial PetCO2 did not correlate with return of spontaneous circulation. CONCLUSIONS: End-tidal CO2 during the first five breaths of CPR is much higher after an asphyxial cardiac arrest than VF. In each case, the initial PetCO2 appears to reflect alveolar CO2 prior to CPR. After one minute of CPR, PetCO2 is useful in monitoring the effectiveness of CPR.

Animals↗
PubMed1995

Failure of intravenous metoprolol to limit acute myocardial infarct size in a nonreperfused porcine model.

The usefulness of intravenous beta-adrenergic receptor blockade in limiting infarct size when neither reperfusion nor collateral flow occurs is unknown. The effect of intravenous metoprolol on limiting myocardial infarct size was therefore examined in a nonreperfused porcine model. Closed-chest techniques were used to occlude the left anterior descending coronary artery, after which animals were randomized at 20 minutes to receive intravenous metoprolol, 0.75 mg/kg, or placebo. Infarct size examined at 5 hours with Evans blue and triphenyltetrazolium staining techniques was expressed as a percentage of total ventricular myocardium at ischemic risk. This percentage was not significantly different between the groups (84% +/- 5% with metoprolol vs 90% +/- 4% with placebo; p = 0.4). Myocardial infarct size was not significantly decreased at 5 hours by early administration of intravenous metoprolol when the infarct artery remained occluded and collateral flow was minimal.

Animals↗
PubMed1995

The need for ventilatory support during bystander CPR.

STUDY OBJECTIVE: To compare CPR with chest compressions plus ventilatory support (CC+V) and chest compressions alone (CC). DESIGN: Prospective, randomized study. SETTING: Research laboratory. INTERVENTIONS: After 2 minutes of ventricular fibrillation, 18 domestic swine (20 to 35 kg) were treated first with CC or CC+V for 10 minutes, then with standard advanced cardiac life support. RESULTS: Hemodynamics, survival, and neurologic outcome were determined. All 8 swine subjected to CC+V and all 10 subjected to CC showed return of spontaneous circulation. One animal in each group died within 1 hour. Seven of 8 animals in the CC+V group survived for 24 and 48 hours, compared with 9 of 10 CC animals at 24 hours and 8 of 10 at 48 hours. All 48-hour survivors were neurologically normal. CONCLUSION: In this experimental model of bystander CPR, we could not detect a difference in hemodynamics, 48-hour survival, or neurologic outcome when CPR was applied with and without ventilatory support.

Animals↗
PubMed1994

High-dose epinephrine results in greater early mortality after resuscitation from prolonged cardiac arrest in pigs: a prospective, randomized study.

OBJECTIVE: To determine whether high-dose epinephrine (0.2 mg/kg) during cardiopulmonary resuscitation (CPR) results in improved outcome, compared with standard-dose epinephrine (0.02 mg/kg). DESIGN: A prospective, randomized, blinded study. SETTING: Research laboratory of a university medical center. SUBJECTS AND INTERVENTIONS: Thirty domestic swine were randomized to receive standard- or high-dose epinephrine during CPR after 15 mins of fibrillatory cardiac arrest. Three minutes of CPR were provided, followed by advanced cardiac life support per American Heart Association guidelines. Animals that were successfully resuscitated were supported for 2 hrs in an intensive care unit (ICU) setting, and then 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. Survival and neurologic outcome were determined. Return of spontaneous circulation was attained in 14 of 15 animals in each group. Four of 14 high-dose epinephrine pigs died during the ICU period after return of spontaneous circulation vs. zero of the 14 standard-dose pigs (p < .05). Six standard-dose pigs survived 24 hrs vs. four high-dose pigs. Twenty-four-hour survival rate and neurologic outcome were not significantly different. Within 10 mins of defibrillation, severe hypertension (diastolic pressure > 120 mmHg) occurred in 12 of 14 high-dose pigs vs. two of 14 standard-dose pigs (p < .01). Severe tachycardia (heart rate > 250 beats/min) occurred in seven of 14 high-dose pigs vs. zero of 14 standard-dose pigs (p < .01). All four high-dose epinephrine pigs that died during the ICU period experienced both severe hypertension and tachycardia immediately postresuscitation. CONCLUSIONS: High-dose epinephrine did not improve 24-hr survival rate or neurologic outcome. Immediately after return of spontaneous circulation, most animals in the high-dose epinephrine group exhibited a hyperadrenergic state that included severe hypertension and tachycardia. High-dose epinephrine resulted in a greater early mortality rate.

Animals↗