R W Hilwig

The University of Arizona, Tucson, AZ, United States

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Publications (38)219.74 Total impact

  • Free Radical Biology and Medicine - FREE RADICAL BIOL MED. 01/2010; 49.
  • Journal of Cardiac Failure - J CARD FAIL. 01/2009; 15(6).
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    ABSTRACT: Introduction: Mild induced hypothermia is now the recommended treatment for per-sistently comatose adults after resuscitation from out-of-hospital ventricular fibrilla-tion (VF) cardiac arrest. The cardio-protective benefits of induced mild hypothermia are still unclear. Although induced mild hypothermia is a well-established effective therapy for improving neurological outcomes, its effects on early ventricular dilata-tion or late stone heart development, secondary to untreated VF, are unknown. Hypothesis: Pre-arrest induced mild hypothermia in sustained VF substantially extends the time interval from commencement of cardiac arrest until the development of stone heart, thereby prolonging the limit of rescusitability. Method: Fourteen female swine (27 6 1 kg) were used in this study. Animals were randomized to 2 groups, normothermia (n56) and hypothermia (n58). Mild hypothermia (32-34 oC) was induced by surrounding the swine body with ice packs for prior to imaging. After achieving a rectal temperature of 32-34 oC, routine CMR images in normal sinus rhythm were obtained. A pacing catheter electrode was placed temporarily into the RV to induce VF with 100Hz alternating current. Before fibrillation, a set of short-axis views were acquired. Data collection started immediately after the initiation of VF, every minute for the first 5 minutes, and every 5 minutes thereafter until the development of stone heart (2/3 reduction in the baseline mean LV volume). Results: Time to stone heart occurred at 52 6 4 minutes in the hypothermia animals compared to 29 6 3 minutes in the normothermia animals (P!0.001). During the first 5 minutes of untreated VF, mean LV volume increased by 11% in the hypother-mia group compared to 34% increase in the normothermia group (P!0.05). Between 10 and 30 minutes of untreated VF, there were no significant changes in LV volumes in the hypothermia group versus 75% decrease in LV volume in the normothermia group. Conclusion: Stone heart, or severe LV myocardial ischemic contracture, is an irreversible phenomenon and marks the limit of myocardial resuscitability. This study demonstrates that in a closed-chest whole animal model of untreated prolonged VF cardiac arrest, pre-arrest induced mild hypothermia substantially delays the de-velopment of stone heart. This adds to our current understanding of the beneficial mechanism of mild hypothermia and suggests that morphologic changes are at least in part responsible for or an important by-product of this practice. Introduction: Cardiac resynchronization therapy(CRT) has proven effective in patients with EF ! 35%, wide QRS, and advanced heart failure. We sought to deter-mine the extent of change for measures of intracardiac conduction over time and how these measures relate to structural and clinical variables. Methods: Data was col-lected from 30 pts. who were enrolled in the Boston Scientific DECREASE-HF trial. NYHA class and measures of intracardiac conduction; intrinsic AV and V-V delays, QRS duration, and AV delay during AAI pacing were collected at baseline and at 3 mth intervals. Echocardiographic measures of left ventricular end-systolic(LVESV) and end-diastolic(LVEDV) volumes were collected at baseline, 3 and 6 mths. The data was analyzed using paired t-tests and linear regression models, adjusting for repeated measures within each patient. Results: LVESV was significantly reduced at 6 mths. NYHA improved at least 1 class in 57% and 63% of pts. at 6 mths and final visit. Within the overall group there were no significant changes in any measures of intracardiac conduction between the baseline and 6 mth visit or the last visit (Table 1) but changes were observed in individual patients. Both LVEDV and LVESV were significantly associated with AV delay (p!.01 for both, effect size: -.23ms change in AV for a 1 ml decrease in LVEDV, -.22ms for LVESV). Conclusions: In these patients, CRT induced structural and clinical improvements. While there was no over-all average difference in intracardiac conduction intervals, individual patient change and fluctuation from visit to visit was observed.
  • Resuscitation 01/2008; 77. · 4.10 Impact Factor
  • Resuscitation 01/2008; 77. · 4.10 Impact Factor
  • Prehospital Emergency Care - PREHOSP EMERG CARE. 01/2004; 8(1):82-82.
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    Journal of The American College of Cardiology - J AMER COLL CARDIOL. 01/2002; 39:282-282.
  • Der Anaesthesist 01/2002; 51(8):659-660. · 0.85 Impact Factor
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    ABSTRACT: 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. 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. Interrupting chest compressions for rescue breathing can adversely affect hemodynamics during CPR for VF.
    Circulation 12/2001; 104(20):2465-70. · 15.20 Impact Factor
  • Resuscitation 11/2000; 47(2):203-8. · 4.10 Impact Factor
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    ABSTRACT: 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.
    Resuscitation 11/2000; 47(3):287-99. · 4.10 Impact Factor
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    R W Hilwig, R A Berg, K B Kern, G A Ewy
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    ABSTRACT: 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. 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). 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.
    Circulation 05/2000; 101(17):2097-102. · 15.20 Impact Factor
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    R A Berg, R W Hilwig, K B Kern, G A Ewy
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    ABSTRACT: 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. 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). 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.
    Circulation 04/2000; 101(14):1743-8. · 15.20 Impact Factor
  • R A Berg, R W Hilwig, K B Kern, I Babar, G A Ewy
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    ABSTRACT: 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. Prospective, randomized study. Thirty-nine anesthetized domestic piglets. 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. 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). 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.
    Critical Care Medicine 10/1999; 27(9):1893-9. · 6.12 Impact Factor
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    ABSTRACT: 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.
    Resuscitation 08/1999; 41(2):185-92. · 4.10 Impact Factor
  • K B Kern, R W Hilwig, R A Berg, G A Ewy
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    ABSTRACT: 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.
    Resuscitation 12/1998; 39(3):179-88. · 4.10 Impact Factor
  • R A Berg, K B Kern, R W Hilwig, G A Ewy
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    ABSTRACT: 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. 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. In this acute myocardial infarction model of prehospital single-rescuer bystander CPR, assisted ventilation did not improve outcome.
    Circulation 01/1998; 96(12):4364-71. · 15.20 Impact Factor
  • Critical Care Medicine - CRIT CARE MED. 01/1998; 26.
  • Robert Berg, Ronald Hilwig, Karl Kem, Gordon Ewy
    Critical Care Medicine 12/1997; 26(1):56A. · 6.12 Impact Factor
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    ABSTRACT: 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. 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). 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.
    Circulation 07/1997; 95(12):2610-3. · 15.20 Impact Factor