Adverse effects of high-dose epinephrine on cerebral blood flow during experimental cardiopulmonary resuscitation

Masked Randomized Trial of Epinephrine versus Vasopressin in an Ovine Model of Perinatal Cardiac Arrest

BACKGROUND

Current neonatal resuscitation guidelines recommend the use of epinephrine for bradycardia/arrest not responding to ventilation and chest compressions. Vasopressin is a systemic vasoconstrictor and is more effective than epinephrine in postnatal piglets with cardiac arrest. There are no studies comparing vasopressin with epinephrine in newly born animal models with cardiac arrest induced by umbilical cord occlusion. Objective: To compare the effect of epinephrine and vasopressin on the incidence and time to return of spontaneous circulation (ROSC), hemodynamics, plasma drug levels, and vasoreactivity in perinatal cardiac arrest. Design/Methods: Twenty-seven term fetal lambs in cardiac arrest induced by cord occlusion were instrumented and resuscitated following randomization to epinephrine or vasopressin through a low umbilical venous catheter. Results: Eight lambs achieved ROSC prior to medication. Epinephrine achieved ROSC in 7/10 lambs by 8 ± 2 min. Vasopressin achieved ROSC in 3/9 lambs by 13 ± 6 min. Plasma vasopressin levels in nonresponders were much lower than responders after the first dose. Vasopressin caused in vivo increased pulmonary blood flow and in vitro coronary vasoconstriction. Conclusions: Vasopressin resulted in lower incidence and longer time to ROSC compared to epinephrine in a perinatal model of cardiac arrest supporting the current recommendations for exclusive use of epinephrine in neonatal resuscitation.

Establishing a multicenter, preclinical consortium in resuscitation: A pilot experimental trial evaluating epinephrine in cardiac arrest

BACKGROUND

Large animal studies are an important step in the translation pathway, but single laboratory experiments do not replicate the variability in patient populations. Our objective was to demonstrate the feasibility of performing a multicenter, preclinical, randomized, double-blinded, placebo-controlled cardiac arrest trial. We evaluated the effect of epinephrine on coronary perfusion pressure (CPP) as previous single laboratory studies have reported mixed results.

METHODS

Forty-five swine from 5 different laboratories (Ann Arbor, MI; Baltimore, MD; Los Angeles, CA; Pittsburgh, PA; Toronto, ON) using a standard treatment protocol. Ventricular fibrillation was induced and left untreated for 6 min before starting continuous cardiopulmonary resuscitation (CPR). After 2 min of CPR, 9 animals from each lab were randomized to 1 of 3 interventions given over 12 minutes: (1) Continuous IV epinephrine infusion (0.00375 mg/kg/min) with placebo IV normal saline (NS) boluses every 4 min, (2) Continuous placebo IV NS infusion with IV epinephrine boluses (0.015 mg/kg) every 4 min or (3) Placebo IV NS for both infusion and boluses. The primary outcome was mean CPP during the 12 mins of drug therapy.

RESULTS

There were no significant differences in mean CPP between the three groups: 14.4 ± 6.8 mmHg (epinephrine Infusion), 16.9 ± 5.9 mmHg (epinephrine bolus), and 14.4 ± 5.5 mmHg (placebo) (p = NS). Sensitivity analysis demonstrated inter-laboratory variability in the magnitude of the treatment effect (p = 0.004).

CONCLUSION

This study demonstrated the feasibility of performing a multicenter, preclinical, randomized, double-blinded cardiac arrest trials. Standard dose epinephrine by bolus or continuous infusion did not increase coronary perfusion pressure during CPR when compared to placebo.

Cerebrovascular and neurological perspectives on adrenoceptor and calcium channel modulating pharmacotherapies

Adrenoceptor and calcium channel modulating medications are widely used in clinical practice for acute neurological and systemic conditions. It is generally assumed that the cerebrovascular effects of these drugs mirror that of their systemic effects - and this is reflected in how these medications are currently used in clinical practice. However, recent research suggests that there are distinct cerebrovascular-specific effects of these medications that are related to the unique characteristics of the cerebrovascular anatomy including the regional heterogeneity in density and distribution of adrenoceptor subtypes and calcium channels along the cerebrovasculature. In this review, we critically evaluate existing basic science and clinical research to discuss known and putative interactions between adrenoceptor and calcium channel modulating pharmacotherapies, the neurovascular unit, and cerebrovascular anatomy. In doing so, we provide a rationale for selecting vasoactive medications based on lesion location and lay a foundation for future investigations that will define neuroprotective paradigms of adrenoceptor and calcium channel modulating therapies to improve neurological outcomes in acute neurological and systemic disorders.

The physiologic response to rescue therapy with vasopressin versus epinephrine during experimental pediatric cardiac arrest

Aim

Compare vasopressin to a second dose of epinephrine as rescue therapy after ineffective initial doses of epinephrine in diverse models of pediatric in-hospital cardiac arrest.

Methods

67 one- to three-month old female swine (10−30 kg) in six experimental cohorts from one laboratory received hemodynamic-directed CPR, a resuscitation method where high quality chest compressions are provided and vasopressor administration is titrated to coronary perfusion pressure (CoPP) ≥20 mmHg. Vasopressors are given when CoPP is <20 mmHg, in sequences of two doses of 0.02 mg/kg epinephrine separated by minimum one-minute, then a rescue dose of 0.4 U/kg vasopressin followed by minimum two-minutes. Invasive measurements were used to evaluate and compare the hemodynamic and neurologic effects of each vasopressor dose.

Results

Increases in CoPP and cerebral blood flow (CBF) were greater with vasopressin rescue than epinephrine rescue (CoPP: +8.16 [4.35, 12.06] mmHg vs. + 5.43 [1.56, 9.82] mmHg, p = 0.02; CBF: +14.58 [-0.05, 38.12] vs. + 0.00 [-0.77, 18.24] perfusion units (PFU), p = 0.005). Twenty animals (30%) failed to achieve CoPP ≥20 mmHg after two doses of epinephrine; 9/20 (45%) non-responders achieved CoPP ≥20 mmHg after vasopressin. Among all animals, the increase in CBF was greater with vasopressin (+14.58 [-0.58, 38.12] vs. 0.00 [-0.77, 18.24] PFU, p = 0.005).

Conclusions

CoPP and CBF rose significantly more after rescue vasopressin than after rescue epinephrine. Importantly, CBF increased after vasopressin rescue, but not after epinephrine rescue. In the 30% that failed to meet CoPP of 20 mmHg after two doses of epinephrine, 45% achieved target CoPP with a single rescue vasopressin dose.

Pralidoxime-Induced Potentiation of the Pressor Effect of Adrenaline and Hastened Successful Resuscitation by Pralidoxime in a Porcine Cardiac Arrest Model

PURPOSE

Pralidoxime potentiated the pressor effect of adrenaline and facilitated restoration of spontaneous circulation (ROSC) after prolonged cardiac arrest. In this study, we hypothesised that pralidoxime would hasten ROSC in a model with a short duration of untreated ventricular fibrillation (VF). We also hypothesised that potentiation of the pressor effect of adrenaline by pralidoxime would not be accompanied by worsening of the adverse effects of adrenaline.

METHODS

After 5 min of VF, 20 pigs randomly received either pralidoxime (40 mg/kg) or saline, in combination with adrenaline, during cardiopulmonary resuscitation (CPR). Coronary perfusion pressure (CPP) during CPR, and ease of resuscitation were compared between the groups. Additionally, haemodynamic data, severity of ventricular arrhythmias, and cerebral microcirculation were measured during the 1-h post-resuscitation period. Cerebral microcirculatory blood flow and brain tissue oxygen tension (PbtO₂) were measured on parietal cortices exposed through burr holes.

RESULTS

All animals achieved ROSC. The pralidoxime group had higher CPP during CPR (P = 0.014) and required a shorter duration of CPR (P = 0.024) and smaller number of adrenaline doses (P = 0.024). During the post-resuscitation period, heart rate increased over time in the control group, and decreased steadily in the pralidoxime group. No inter-group differences were observed in the incidences of ventricular arrhythmias, cerebral microcirculatory blood flow, and PbtO₂.

CONCLUSION

Pralidoxime improved CPP and hastened ROSC in a model with a short duration of untreated VF. The potentiation of the pressor effect of adrenaline was not accompanied by the worsening of the adverse effects of adrenaline.

Comparative In Vitro Study of Various α2-Adrenoreceptor Agonist Drugs for Ticagrelor Reversal

Ticagrelor, an antiplatelet adenosine diphosphate (ADP)-P2Y₁₂ receptor antagonist, increases the risk of bleeding. Its management is challenging because platelet transfusion is ineffective and no specific antidote is currently available. Epinephrine, a vasopressor catecholamine prescribed during shock, restores platelet functions inhibited by ticagrelor through stimulation of α_2A-adrenoreceptors. It subsequently inhibits cyclic adenosine monophosphate (cAMP) pathway and PI3K signaling. However, since epinephrine may expose a patient to deleterious hemodynamic effects, we hypothesized that other α₂-adrenoreceptor agonist drugs used in clinical practice with fewer side effects could reverse the antiplatelet effects of ticagrelor. We compared in vitro the efficacy of clonidine, dexmedetomidine, brimonidine, and norepinephrine with epinephrine to restore ADP- and PAR-1-AP-induced washed platelet aggregation inhibited by ticagrelor, as well as resulting platelet cAMP levels. In ticagrelor-free samples, none of the α₂-adrenoreceptor agonists induced aggregation by itself but all of them potentiated ADP-induced aggregation. Compared with epinephrine, norepinephrine, and brimonidine partially restored ADP- and fully restored PAR-1-AP-induced aggregation inhibited by ticagrelor while clonidine and dexmedetomidine were ineffective. Indeed, this lack of effect resulted from a lower decrease in cAMP concentration elicited by these partial α₂-adrenoreceptor agonists, clonidine, and dexmedetomidine, compared with full α₂-agonists. Our results support the development of specific full and systemic α₂-adrenoreceptor agonists for ticagrelor reversal.

Drugs in the delivery room

The need for cardiopulmonary resuscitation in newborns is quite rare, as most non-vigorous infants respond well to effective ventilation. For the minority of babies who do not respond to adequate ventilation, chest compressions are necessary using the preferred two thumb technique. Since effective ventilation remains a key component to successful resuscitation, chest compressions are coordinated with ventilations in a 3:1 ratio. If despite adequate ventilation and compressions, the heart rate remains below 60 beats per minute, epinephrine is indicated. The intravenous route is preferred over the endotracheal route and the recommended dose of epinephrine is 0.01-0.03 mg/kg. This can be repeated every 3-5 min until return of spontaneous circulation is achieved. In rare instances, when there is no response to these above measures and in infants who show evidence of significant hypovolemia, volume replacement should be considered.

Molecular dynamic simulations reveal suboptimal binding of salbutamol in T164I variant of β2 adrenergic receptor

The natural variant C491T (rs1800088) in ADRB2 gene substitutes Threonine to Isoleucine at 164^th position in β2AR and results in receptor sequestration and altered binding of agonists. Present investigation pursues to identify the effect of T164I variation on function and structure of β2AR through systematic computational approaches. The study, in addition, addresses altered binding of salbutamol in T164I variant through molecular dynamic simulations. Methods involving changes in free energy, solvent accessibility surface area, root mean square deviations and analysis of binding cavity revealed structural perturbations in receptor to incur upon T164I substitution. For comprehensive understanding of receptor upon substitution, OPLS force field aided molecular dynamic simulations were performed for 10 ns. Simulations revealed massive structural departure for T164I β2AR variant from the native state along with considerably higher root mean square fluctuations of residues near the cavity. Affinity prediction by molecular docking showed two folds reduced affinity of salbutamol in T164I variant. To validate the credibility docking results, simulations for ligand-receptor complex were performed which demonstrated unstable salbutamol-T164I β2AR complex formation. Further, analysis of interactions in course of simulations revealed reduced ligand-receptor interactions of salbutamol in T164I variant. Taken together, studies herein provide structural rationales for suboptimal binding of salbutamol in T164I variant through integrated molecular modeling approaches.

Neural injury after use of vasopressin and adrenaline during porcine cardiopulmonary resuscitation

BACKGROUND

Our aim was to investigate cerebral and cardiac tissue injury subsequent to use of vasopressin and adrenaline in combination compared with vasopressin alone during cardiopulmonary resuscitation (CPR).

METHODS

In a randomized, prospective, laboratory animal study 28 anesthetized piglets were subject to a 12-min untreated cardiac arrest and subsequent CPR. After 1 min of CPR, 10 of the piglets received 0.4 U/kg of arg(8)-vasopressin (V group), and 10 piglets received 0.4 U/kg of arg(8)-vasopressin, 1 min later followed by 20 µg/kg body weight of adrenaline, and another 1 min later continuous administration (10 µg/kg/min) of adrenaline (VA group). After 8 min of CPR, the piglets were defibrillated and monitored for another 3 h. Then they were killed and the brain immediately removed pending histological analysis.

RESULTS

During CPR, the VA group had higher mean blood pressure and cerebral cortical blood flow (CCBF) but similar coronary perfusion pressure. After restoration of spontaneous circulation there was no difference in the pressure variables, but CCBF tended to be (36% ± 16%) higher in the V group. Neuronal injury and signs of a disrupted blood-brain barrier (BBB) were greater, 20% ± 4% and 21% ± 4%, respectively, in the VA group. In a background study of repeated single doses of adrenaline every third minute after 5 min arrest but otherwise the same protocol, histological measurements showed even worse neural injury and disruption of the BBB.

CONCLUSION

Combined use of vasopressin and adrenaline caused greater signs of cerebral and cardiac injury than use of vasopressin alone during experimental cardiopulmonary resuscitation.

The effects of nitroglycerin during cardiopulmonary resuscitation

The outcome for both in-hospital and out-of hospital cardiac arrest remains dismal. Vasopressors are used to increase coronary perfusion pressure and thus facilitate return of spontaneous circulation during cardiopulmonary resuscitation. However, they are associated with a number of potential adverse effects and may decrease endocardial and cerebral organ blood flow. Nitroglycerin has a favourable haemodynamic profile which promotes forward blood flow. Several studies suggest that combined use of nitroglycerin with vasopressors during resuscitation, is associated with increased rates of resuscitation and improved post-resuscitation outcome. This article reviews the effects of nitroglycerin during cardiopulmonary resuscitation and postresuscitation period, as well as the beneficial outcomes of a combination regimen consisting of a vasopressor and a vasodilator, such as nitroglycerin.

Drugs during delivery room resuscitation--what, when and why?

Although seldom needed, the short list of medications used for delivery room resuscitation of the newborn includes epinephrine and volume expanders. Naloxone, sodium bicarbonate and the use of other vasopressors are no longer considered helpful during acute resuscitation and are more often administered in the post-resuscitative period under special circumstances. This review examines the existing literature for the two commonly used medications in neonatal resuscitation and identifies the many knowledge gaps requiring further research.

Medications in neonatal resuscitation: epinephrine and the search for better alternative strategies

Epinephrine remains the primary vasopressor for neonatal resuscitation complicated by asystole or prolonged bradycardia not responsive to adequate ventilation and chest compressions. Epinephrine increases coronary perfusion pressure primarily through peripheral vasoconstriction. Current guidelines recommend intravenous epinephrine administration (0.01-0.03 mg/kg). Endotracheal epinephrine administration results in unpredictable absorption. High-dose intravenous epinephrine poses additional risks and does not result in better long-term survival. Vasopressin has been considered an alternative to epinephrine in adults, but there is insufficient evidence to recommend its use in newborn infants. Future research will focus on the best sequence for epinephrine administration and chest compressions.

Potential negative effects of epinephrine on carotid blood flow and ETCO2 during active compression-decompression CPR utilizing an impedance threshold device

OBJECTIVES

This study examines the effects of IV epinephrine administration on carotid blood flow (CBF) and end tidal CO(2) (ETCO(2)) production in a swine model of active compression-decompression CPR with an impedance threshold device (ACD-CPR+ITD).

METHODS

Six female swine (32 ± 1 kg) were anesthetized, intubated and ventilated. Intracranial, thoracic aorta and right atrial pressures were measured via indwelling catheters. CBF was recorded. ETCO(2), SpO(2) and EKG were monitored. V-fib was induced and went untreated for 6 min. Three minutes each of standard CPR (STD), STD-CPR+impedance threshold device (ITD) and active compression-decompression (ACD)-CPR+ITD were performed. At minute 9 of the resuscitation, 40 μg/kg of IV Epinephrine was administered and ACD-CPR+ITD was continued for 1 min. Statistical analysis was performed with a paired t-test. p values of <0.05 were considered statistically significant and all values are reported in mmHg unless otherwise noted.

RESULTS

Aortic pressure, cerebral and coronary perfusion pressures increased from STD<STD+ITD<ACD-CPR+ITD (p<0.001). Epinephrine administered during ACD-CPR+ITD signficantly increased mean aortic pressure (29 ± 5 vs 42 ± 12, p = 0.01), cerebral perfusion pressure (12 ± 5 vs 22 ± 10, p = 0.01), and coronary perfusion pressure (8 ± 7 vs 17 ± 4, p = 0.02); however, mean CBF and ETCO(2) decreased (respectively 29 ± 15 vs 14 ± 7.0 ml/min, p = 0.03; 20 ± 7 vs 18 ± 6, p = 0.04).

CONCLUSIONS

In this model, administration of epinephrine during ACD-CPR+ITD significantly increased markers of macrocirculation, while significantly decreasing carotid blood flow and ETCO(2). This calls into question the ability of calculated perfusion pressures to accurately reflect oxygen delivery to end organs. The administration of epinephrine during ACD-CPR+ITD does not improve cerebral tissue perfusion.

Combination pharmacotherapy improves neurological outcome after asphyxial cardiac arrest

AIM

To study the effects of the combination of adrenaline (epinephrine) and vasopressin compared to adrenaline alone on initial resuscitation success, 24h survival, and neurological outcome in a swine model of asphyxial cardiac arrest (CA).

METHODS

This prospective randomized experimental study was conducted at a laboratory research department. Twenty female Landrace/Large-White pigs, 12-15 weeks of age, were investigated. Asphyxial CA was induced by clamping of the endotracheal tube. After 4min of untreated CA, resuscitation was initiated by unclamping the endotracheal tube, mechanical ventilation, chest compressions and adrenaline (Group A) or a combination of adrenaline with vasopressin (Group A+V) administered intravenously. In case of restoration of spontaneous circulation (ROSC), the animals were monitored for 30min and then observed for 24h.

RESULTS

Hemodynamic variables were measured at baseline during CPR and in the post-resuscitation period. Statistically significant difference was observed in groups A and A+V regarding coronary perfusion pressure (CPP) during the first minute of CPR. In both groups, ROSC and survival rates were comparable (p=NS). Neurological deficit score (NDS) was significantly higher in the combination group 24h following CA (p<0.001). Brain histological damage score (HDS) was also better in the combination group (p<0.001). Total HDS and NDS showed a statistical significant correlation (p<0.001).

CONCLUSIONS

In this porcine model of asphyxial CA, adrenaline alone as well as the combined administration of adrenaline and vasopressin resulted in similar ROSC and survival rates, but the combination of adrenaline and vasopressin resulted in improved neurological and cerebral histopathological outcomes.

Variable effects of high-dose adrenaline relative to standard-dose adrenaline on resuscitation outcomes according to cardiac arrest duration

AIM OF THE STUDY

Adjustment of adrenaline (epinephrine) dosage according to cardiac arrest (CA) duration, rather than administering the same dose, may theoretically improve resuscitation outcomes. We evaluated variable effects of high-dose adrenaline (HDA) relative to standard-dose adrenaline (SDA) on resuscitation outcomes according to CA duration.

METHODS

Twenty-eight male domestic pigs were randomised to the following 4 groups according to the dosage of adrenaline (SDA 0.02 mg/kg vs. HDA 0.2mg/kg) and duration of CA before beginning cardiopulmonary resuscitation (CPR): 6 min SDA, 6 min HDA, 13 min SDA, or 13 min HDA. After the predetermined duration of untreated ventricular fibrillation, CPR was provided.

RESULTS

All animals in the 6 min SDA, 6 min HDA, and 13 min HDA groups were successfully resuscitated, while only 4 of 7 pigs in the 13 min SDA group were successfully resuscitated (p=0.043). HDA groups showed higher right atrial pressure, more frequent ventricular ectopic beats, higher blood glucose, higher troponin-I, and more severe metabolic acidosis than SDA groups. Animals of 13 min groups showed more severe metabolic acidosis and higher troponin-I than animals of 6 min groups. All successfully resuscitated animals, except two animals in the 13 min HDA group, survived for 7 days (p=0.121). Neurologic deficit score was not affected by the dose of adrenaline.

CONCLUSION

HDA showed benefit in achieving restoration of spontaneous circulation in 13 min CA, when compared with 6 min CA. However, this benefit did not translate into improved long-term survival or neurologic outcome.

Terlipressin for Children with Extremely Low Cardiac Output After Open Heart Surgery

Background:

Terlipressin, a long-acting analog of vasopressin, has been used successfully in patients with extremely low cardiac output, but its application in children following open heart surgery is limited.

Objective:

To describe our experience using terlipressin in children with extremely low cardiac output after open heart surgery.

Methods:

Records were reviewed of all pediatric patients between January 2003 and December 2005 who had undergone open heart surgery, experienced extremely low cardiac output, and were treated with terlipressin as rescue therapy. Mean arterial blood pressure, heart rate, urine output, and lactate and oxygenation index values were retrieved and analyzed when available.

Results:

Twenty-nine children who were considered gravely ill despite conventional vasoactive agents received terlipressin as rescue therapy, which rapidly yielded significant improvements in all measured hemodynamic and respiratory indices. Mean ± SD arterial blood pressure increased significantly, from 49 ± 17 to 57 ± 16 mm Hg after 10 minutes (p = 0.004) and to 64 ± 15 mm Hg 24 hours after treatment onset (p = 0.001). Twenty-four hours following terlipressin administration, urine output increased from 1.5 ± 2.1 to 3.0 ± 2.3 mL/kg/h (p = 0.001), the oxygenation index decreased from 16.5 ± 27.9 to 9.5 ± 16.7 in the survivors (p = 0.023), and the inotropic score decreased from 41.9 ± 19.9 to 32.6 ± 18.8 (p = 0.009).

Conclusions:

Terlipressin caused significant improvement in hemodynamic, respiratory, and renal indices in children with extremely low cardiac output after open heart surgery. Further controlled studies are needed to confirm the drug's safety and efficacy in this population.

Analysis of prehospital care for cardiac arrest in an urban setting in Japan

BACKGROUND

In Japan, the management of prehospital care for cardiopulmonary arrest (CPA) has recently changed.

STUDY OBJECTIVES

The characteristics of prehospital care for CPA were analyzed to identify predictors of prehospital return of spontaneous circulation (PROSC) and good recovery.

METHODS

The characteristics of prehospital management of 713 out-of-hospital CPA patients in the First Western District of Saitama Prefecture, Japan, were retrospectively analyzed.

RESULTS

Overall, PROSC rate was 9.5% (n = 68), and 2.2% of patients (n = 16) made a good recovery. Significant positive predictors of PROSC were: duration from the first call to hospital arrival, witnessed collapse, ventricular fibrillation at scene, and epinephrine administration. Establishment of supraglottic airway was a significant negative predictor of PROSC. Significant positive predictors of good recovery were younger age, ventricular fibrillation at scene, and PROSC. Changes to the life support protocol based on 2005 guidelines did not affect the outcome.

CONCLUSIONS

Epinephrine was effective in increasing PROSC; however, it did not improve recovery of such patients. The findings also suggest that out-of-hospital care providers should not try to establish a supraglottic airway.

Vascular access and drug therapy in pediatric resuscitation

Using the evidence brought together through the 2005 International Liaison Committee on Resuscitation evidence evaluation process and the subsequent 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, the role for specific drug therapy in pediatric cardiac arrest is outlined. The drugs discussed include epinephrine, vasopressin, calcium, sodium bicarbonate, atropine, magnesium, and glucose. The literature addressing how best to deliver these drugs to the critically ill child is also presented, specifically looking at the use of intraosseous and endotracheal drug therapy.

Revised resuscitation guidelines: Adrenaline versus adrenaline/vasopressin in a pig model of cardiopulmonary resuscitation—A randomised, controlled trial

BACKGROUND

Synergistic effects of adrenaline (epinephrine) and vasopressin may be beneficial during cardiopulmonary resuscitation. However, it is unknown whether either adrenaline alone or an alternating administration of adrenaline and vasopressin is better for restoring vital organ perfusion following basic life support (BLS) according to the revised algorithm with a compression-to-ventilation (c/v) ratio of 30:2.

MATERIAL AND METHODS

After 4min of ventricular fibrillation, and 6min of BLS with a c/v ratio of 30:2, 16 pigs were randomised to receive either 45microg/kg adrenaline, or alternating 45microg/kg adrenaline and 0.4U/kg vasopressin, respectively.

RESULTS

Coronary perfusion pressure (mean+/-S.D.) 20 and 25min after cardiac arrest was 7+/-4 and 5+/-3mm Hg after adrenaline, and 25+/-2 and 14+/-3mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), respectively. Cerebral perfusion pressure was 23+/-7 and 19+/-9mm Hg after adrenaline, and 40+/-10 and 33+/-7mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), and cerebral blood flow was 30+/-10 and 27+/-11% of baseline after adrenaline, and 65+/-40 and 50+/-31% of baseline after adrenaline/vasopressin (p<0.05 versus adrenaline), respectively. Return of spontaneous circulation (ROSC) did not differ significantly between the adrenaline group (0/8) and the adrenaline/vasopressin group (3/8).

CONCLUSION

Adrenaline/vasopressin resulted in higher coronary and cerebral perfusion pressures, and cerebral blood flow, while ROSC was comparable.

Vasopressors are essential during cardiopulmonary resuscitation in rats: Is vasopressin superior to adrenaline?

BACKGROUND

Vasopressors are recommended for cardiopulmonary resuscitation (CPR) after cardiac arrest. In order to assess possible benefits regarding neurological recovery, vasopressin versus adrenaline and the combination of both was tested against placebo in a cardiac arrest model in rats.

METHODS

Under anaesthesia with halothane and N2O, cardiac arrest was initiated via transoesophageal electrical fibrillation. After 7 min of global ischaemia, CPR was performed by external chest compression combined with defibrillation. Animals were randomly assigned to three groups receiving adrenaline, vasopressin and a combination of both (n = 15 per group) versus placebo (n = 8). At 1, 3 and 7 days animals were tested according to a neurological deficit score (NDS). After 7 days of reperfusion, coronal brain sections were analysed by Nissl- and TUNEL-staining. Viable as well as TUNEL-positive neurons were counted in the hippocampal CA-1 sector. For statistical analysis, the log rank and the Kruskal-Wallis ANOVA test were used. All data are given as mean+/-S.D.; a p-value <0.05 was considered significant.

RESULTS

Mean arterial blood pressure (MAP) measured in the aorta did not differ between the vasopressor groups, whereas placebo animals had significantly lower levels. Survival to 7 days revealed significant differences between the placebo (n = 0/8) and all vasopressor groups (adrenaline, 10/15; adrenaline/vasopressin, 8/15; vasopressin, 12/15). Histological deficit scoring by quantitative analysis of the Nissl- and TUNEL-staining showed no difference in the amount of viable and apoptotic neurons in the vasopressin group (viable: 33+/-18; apoptotic: 63+/-23) versus the adrenaline group (viable: 21+/-12; apoptotic: 67+/-17) and the adrenaline/vasopressin group (viable: 31+/-26; apoptotic: 61+/-27). Neurological deficit scoring did not show any differences between the vasopressor groups.

CONCLUSION

Administration of arginine-vasopressin during CPR does not improve behavioural and cerebral histopathological outcome, compared to the use of adrenaline or the combination of both vasopressors, after cardiac arrest in rats.

Cerebral metabolism assessed with microdialysis in uncontrolled hemorrhagic shock after penetrating liver trauma

In a porcine model of uncontrolled hemorrhagic shock, we evaluated the effects of fluid resuscitation versus arginine vasopressin (AVP) combined with hypertonic-hyperoncotic hydroxyethyl starch solution (HHS) on cerebral perfusion pressure (CPP) and on cerebral metabolism using intracerebral microdialysis. Sixteen anesthetized pigs were subjected to uncontrolled liver bleeding until hemodynamic decompensation, followed by resuscitation using either fluid (n = 8) or AVP/HHS (n = 8). Thirty minutes after drug administration, bleeding was controlled by manual compression, and colloid and crystalloid solutions were administered in both groups. All surviving animals were observed for one hour. After hemodynamic decompensation, fluid resuscitation resulted in a smaller increase of CPP than did AVP/HHS (mean +/- sem; 24 +/- 5 vs 45 +/- 7 mm Hg; P < 0.01). Mean (+/- sem) cerebral venous partial pressure of oxygen was significantly decreased (P < 0.01) 5 min after fluid compared with 5 min after AVP/HHS administration (36 +/- 3 vs 64 +/- 4 torr). Cerebral metabolism was comparable in both groups. In conclusion, AVP/HHS proved to be superior to fluid in the initial phase of therapy with respect to CPP and cerebral oxygenation, but was comparable to fluid regarding cerebral metabolism and secondary cell damage in surviving animals.

Brain tissue oxygen pressure and cerebral metabolism in an animal model of cardiac arrest and cardiopulmonary resuscitation

OBJECTIVE

Direct measurement of brain tissue oxygenation (PbtO2) is established during spontaneous circulation, but values of PbtO2 during and after cardiopulmonary resuscitation (CPR) are unknown. The purpose of this study was to investigate: (1) the time-course of PbtO2 in an established model of CPR, and (2) the changes of cerebral venous lactate and S-100B.

METHODS

In 12 pigs (12-16 weeks, 35-45 kg), ventricular fibrillation (VF) was induced electrically during general anaesthesia. After 4 min of untreated VF, all animals were subjected to CPR (chest compression rate 100/min, FiO2 1.0) with vasopressor therapy after 7, 12, and 17 min (vasopressin 0.4, 0.4, and 0.8 U/kg, respectively). Defibrillation was performed after 22 min of cardiac arrest. After return of spontaneous circulation (ROSC), the pigs were observed for 1h.

RESULTS

After initiation of VF, PbtO2 decreased compared to baseline (mean +/- SEM; 22 +/- 6 versus 2 +/- 1 mmHg after 4 min of VF; P < 0.05). During CPR, PbtO2 increased, and reached maximum values 8 min after start of CPR (25 +/- 7 mmHg; P < 0.05 versus no-flow). No further changes were seen until ROSC. Lactate, and S-100B increased during CPR compared to baseline (16 +/- 2 versus 85 +/- 8 mg/dl, and 0.46 +/- 0.05 versus 2.12 +/- 0.40 microg/l after 13 min of CPR, respectively; P < 0.001); lactate remained elevated, while S-100B returned to baseline after ROSC.

CONCLUSIONS

Though PbtO2 returned to pre-arrest values during CPR, PbtO2 and cerebral lactate were lower than during post-arrest reperfusion with 100% oxygen, which reflected the cerebral low-flow state during CPR. The transient increase of S-100B may indicate a disturbance of the blood-brain-barrier.

Use of high-dose epinephrine and sodium bicarbonate during neonatal resuscitation: is there proven benefit?

For adults and pediatric age patients, high-dose intravenous epinephrine was recommended if standard-dose epinephrine failed to achieve return of spontaneous circulation. More recent trials suggest that high-dose epinephrine is not beneficial and may result in increased harm. There are no randomized clinical studies of high-dose versus standard-dose intravenous epinephrine in neonates. Routine use of high-dose epinephrine during neonatal resuscitation cannot be recommended. Although sodium bicarbonate has been used during neonatal resuscitation, the only randomized controlled trial of its use during brief neonatal resuscitation showed no benefit. Sodium bicarbonate infusion during neonatal cardiopulmonary resuscitation (CPR) has several known and potential side effects. The use of sodium bicarbonate infusion should be discouraged during brief CPR. Whether sodium bicarbonate is beneficial for infants who require prolonged CPR despite adequate ventilation is unknown.

Increased cortical cerebral blood flow with LUCAS; a new device for mechanical chest compressions compared to standard external compressions during experimental cardiopulmonary resuscitation

OBJECTIVE

LUCAS is a new device for mechanical compression and decompression of the chest during cardiopulmonary resuscitation (CPR). The aim of this study was to compare the efficacy of this new device with standard manual external chest compressions using cerebral cortical blood flow, cerebral oxygen extraction, and end-tidal CO2 for indirect measurement of cardiac output. Drug therapy, with adrenaline (epinephrine) was eliminated in order to evaluate the effects of chest compressions alone.

METHODS

Ventricular fibrillation (VF) was induced in 14 anaesthetized pigs. After 8 min non-intervention interval, the animals were randomized into two groups. One group received external chest compressions using a new mechanical device, LUCAS. The other group received standard manual external chest compressions. The compression rate was 100 min(-1) and mechanical ventilation was resumed with 100% oxygen during CPR in both groups. No adrenaline was given. After 15 min of CPR, external defibrillatory shocks were applied to achieve restoration of spontaneous circulation (ROSC). Cortical cerebral blood flow was measured continuously using Laser-Doppler flowmetry. End-tidal CO2 was measured using mainstream capnography.

RESULTS

During CPR, the cortical cerebral blood flow was significantly higher in the group treated with LUCAS (p = 0.041). There was no difference in oxygen extraction between the groups. End-tidal CO2, an indirect measurement of the achieved cardiac output during CPR, was significantly higher in the group treated with the LUCAS device (p = 0.009). Restoration of spontaneous circulation was achieved in two animals, one from each group.

CONCLUSIONS

Chest compressions with the LUCAS device during experimental cardiopulmonary resuscitation resulted in higher cerebral blood flow and cardiac output than standard manual external chest compressions. These results strongly support prospective randomised studies in patients to evaluate this new device.

TERLIPRESSIN AS RESCUE THERAPY FOR INTRACTABLE HYPOTENSION DUE TO SEPTIC SHOCK IN CHILDREN

Intractable hypotension due to septic shock is associated with high mortality rates in critically ill children worldwide. The use of terlipressin (triglycyl-lysine-vasopressin), an analog of vasopressin with a longer duration of action, recently emerged as a treatment of hypotension not responsive to vasopressors and inotropes. This was a retrospective study set in an 18-bed pediatric critical care department in a tertiary care children's hospital. We reviewed the files of all children with septic shock who were treated with terlipressin between January 2003 and February 2004. Fourteen children (mean age, 5.6 years; range, 4 days to 17.7 years) were treated with terlipressin in 16 septic shock episodes. Significant improvements in respiratory and hemodynamic indices were noted shortly after treatment. Mean arterial blood pressure increased significantly from 54 +/- 3 to 72 +/- 5 mmHg 10 min after terlipressin administration (P = 0.001). Heart rate decreased from 153.0 +/- 6.5 beats/min to 138.0 +/- 7.5 beats/min 12 h after treatment onset (P = 0.003). Epinephrine infusion was decreased or stopped in eight patients after terlipressin administration. Urine output increased from 1.6 +/- 0.5 mL/kg/h to 4.3 +/- 1.2 mL/kg/h 1 h after treatment onset (P = 0.011). PaO2 increased from 95.1 +/- 12.3 mmHg to 110.1 +/- 20.5 mmHg, and the oxygenation index decreased from 10.2 +/- 2.2 to 9.2 +/- 1.7. Terlipressin treatment of hypotension due to septic shock was successful in eight out of 16 episodes. Six of the 14 patients with poor prognosis for survival recovered. We conclude that terlipressin improves hemodynamic indices and renal function in critically ill children. Terlipressin should be considered as a rescue therapy in intractable shock not responsive to catecholamines in children.

INTRAVENOUS ARGININE VASOPRESSIN IN CRITICALLY ILL CHILDREN: IS IT BENEFICIAL?

Arginine-vasopressin (AVP) may be more effective than epinephrine in shock states and as an end-of-life salvage maneuver. However, there is only limited experience using AVP in children. Our study aim was to evaluate the effect of AVP administration on hemodynamic and ventilatory parameters in critically ill children. Eight critically ill children (1 month to 12 years old) were treated with AVP during the years 2000-2001. Two patients had had head trauma, and six had surgical correction of congenital heart disease. All patients suffered severe septic or cardiogenic shock with a low cardiac output state and were considered to be near death. AVP was administered continuously at a dose of 0.0003-0.002 U/kg/min. Hemodynamic and ventilatory parameters and vasopressor doses were compared before and after AVP initiation. One patient survived with a good neurologic outcome. Seven patients succumbed while receiving AVP. Systolic and diastolic blood pressure increased significantly (P < 0.03) following AVP initiation. The epinephrine requirement decreased from 2.3 to 1.7 microg/kg/min. Blood gases improved with a significant (P < 0.05) increase of PaO2. Oxygenation index and PaO2/FiO2 ratio improved significantly, and ventilatory support requirements and positive inspiratory pressure (PIP) decreased significantly. Despite a significant improvement in hemodynamic and ventilatory support parameters, survival to hospital discharge was not achieved when AVP was used in critically ill pediatric patients. We hypothesize that earlier administration of AVP may be more beneficial.

Adrenaline administration during cardiopulmonary resuscitation: poor adherence to clinical guidelines

BACKGROUND

Adrenaline does not appear to improve the outcome after cardiac arrest in clinical trials in spite of beneficial effects in experimental studies. The objective of this study was to determine whether adrenaline was administered in accordance with advanced cardiac life support (ACLS) guidelines during adult cardiopulmonary resuscitation (CPR).

METHODS

From 15 January to 31 December 2000, all patients at Uppsala University Hospital in whom CPR was attempted were registered prospectively. The duration of CPR was documented in the register and the total dose of adrenaline was retrieved retrospectively from patient records. From these data the average interval between adrenaline doses was calculated.

RESULTS

Data for evaluation of the between-dose interval of adrenaline was available in 53 of 107 registered cardiac arrests. In 68% (36/53) the average between-dose interval was longer than the 3-5 min recommended in the guidelines, and 8% (4/53) received no adrenaline. The median interval between adrenaline doses during CPR was 6.5 min (25th-75th percentile: 5.1-10.4). Adherence to guidelines was lower in out-of-hospital cardiac arrest than in in-hospital cardiac arrest (P = 0.01).

CONCLUSIONS

In the majority of cases adrenaline did not appear to be administered according to current ACLS guidelines.

Vasopressin versus continuous adrenaline during experimental cardiopulmonary resuscitation

OBJECTIVE

To evaluate the effects of a bolus dose of vasopressin compared to continuous adrenaline (epinephrine) infusion on vital organ blood flow during cardiopulmonary resuscitation (CPR).

METHODS

Ventricular fibrillation was induced in 24 anaesthetised pigs. After a 5-min non-intervention interval, CPR was started. After 2 min of CPR the animals were randomly assigned to receive either vasopressin (0.4 U/kg) or adrenaline (bolus of 20 microg/kg followed by continuous infusion of 10 microg/(kg min)). Defibrillation was attempted after 9 min of CPR.

RESULTS

Vasopressin generated higher cortical cerebral blood flow (P < 0.001) and lower cerebral oxygen extraction (P < 0.001) during CPR compared to continuous adrenaline. Coronary perfusion pressure during CPR was higher in vasopressin-treated pigs (P < 0.001) and successful resuscitation was achieved in 12/12 in the vasopressin group versus 5/12 in the adrenaline group (P = 0.005).

CONCLUSIONS

In this experimental model, vasopressin caused a greater increase in cortical cerebral blood flow and lower cerebral oxygen extraction during CPR compared to continuous adrenaline. Furthermore, vasopressin generated higher coronary perfusion pressure and increased the likelihood of restoring spontaneous circulation.

Pediatric cardiopulmonary-cerebral resuscitation: an overview and future directions

The evolving understanding of pathophysiologic events during and after pediatric cardiac arrest has not yet resulted in significantly improved outcome. Exciting breakthroughs in basic and applied science laboratories are, however, on the immediate horizon for study in specific subpopulations of cardiac arrest victims. Strategically focusing therapies to specific phases of cardiac arrest and resuscitation and evolving pathophysiologic events offers great promise that critical care interventions will lead the way to more successful cardiopulmonary and cerebral resuscitation in children.

Increased cortical cerebral blood flow by continuous infusion of adrenaline (epinephrine) during experimental cardiopulmonary resuscitation

OBJECTIVE

To study the effects of continuously administered adrenaline (epinephrine), compared to bolus doses, on the dynamics of cortical cerebral blood flow during experimental cardiopulmonary resuscitation (CPR), and after restoration of spontaneous circulation (ROSC).

METHODS

Ventricular fibrillation was induced in 24 anaesthetised pigs. After a 5-min non-intervention interval, closed-chest CPR was started. The animals were randomised into two groups. One group received three boluses of adrenaline (20 microg/kg) at 3-min intervals. The other group received an initial bolus of adrenaline (20 microg/kg) followed by an infusion of adrenaline (10 microg/kg x min). After 9 min of CPR, defibrillation was attempted, and if spontaneous circulation was achieved the adrenaline infusion was stopped. Cortical cerebral blood flow was measured continuously using Laser-Doppler flowmetry. Jugular bulb oxygen saturation was measured to reflect global cerebral oxygenation. Repeated measurements of 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) in jugular bulb plasma were performed to evaluate cerebral oxidative injury.

RESULTS

During CPR mean cortical cerebral blood flow was significantly higher (P=0.009) with a continuous adrenaline infusion than with repeated bolus doses. Following ROSC there was no significant difference in cortical cerebral blood flow between the two study groups. No differences in coronary perfusion pressure, rate of ROSC, jugular bulb oxygen saturation or 8-iso-PGF(2alpha) were seen between the study groups.

CONCLUSIONS

Continuous infusion of adrenaline (10 microg/kg x min) generated a more sustained increase in cortical cerebral blood flow during CPR as compared to intermittent bolus doses (20 microg/kg every third minute). Thus, continuous infusion might be a more appropriate way to administer adrenaline as compared to bolus doses during CPR.

Survival with full neurologic recovery after prolonged cardiopulmonary resuscitation with a combination of vasopressin and epinephrine in pigs

We sought to determine the effects of a combination of vasopressin and epinephrine on neurologic recovery in comparison with epinephrine alone and saline placebo alone in an established porcine model of prolonged cardiopulmonary resuscitation (CPR). After 4 min of cardiac arrest, followed by 3 min of basic life support CPR, 17 animals were randomly assigned to receive, every 5 min, either a combination of vasopressin and epinephrine (vasopressin [IU/kg]/epinephrine [ micro g/kg]: 0.4/45, 0.4/45, and 0.8/45; n = 6), epinephrine alone (45, 45, and 200 micro g/kg; n = 6), or saline placebo alone (n = 5). After 22 min of cardiac arrest, including 18 min of CPR, defibrillation was attempted to achieve the return of spontaneous circulation. Aortic diastolic pressure was significantly (P < 0.01) increased 90 s after each of 3 vasopressin/epinephrine injections versus epinephrine alone versus saline placebo alone (mean +/- SEM: 69 +/- 3 mm Hg versus 45 +/- 3 mm Hg versus 29 +/- 2 mm Hg, 63 +/- 4 mm Hg versus 27 +/- 3 mm Hg versus 23 +/- 1 mm Hg, and 52 +/- 4 mm Hg versus 21 +/- 3 mm Hg versus 16 +/- 3 mm Hg, respectively). Spontaneous circulation was restored in six of six vasopressin/epinephrine pigs, whereas six of six epinephrine and five of five saline placebo pigs died (P < 0.01). Neurologic evaluation 24 h after successful resuscitation revealed only an unsteady gait and was normal 5 days after the experiment in all vasopressin/epinephrine-treated animals. In conclusion, in this porcine model of prolonged CPR, repeated vasopressin/epinephrine administration, but not epinephrine or saline placebo alone, ensured long-term survival with full neurologic recovery.

IMPLICATIONS

We present a study to evaluate the effects of a combination of vasopressin and epinephrine during prolonged cardiopulmonary resuscitation on neurological outcome in pigs. We found that all pigs treated with a combination of vasopressin and epinephrine could be resuscitated and had full neurologic recovery observed over an entire period of 5 days.

Effects of epinephrine and vasopressin in a piglet model of prolonged ventricular fibrillation and cardiopulmonary resuscitation

OBJECTIVE

We recently demonstrated that vasopressin alone resulted in a poorer outcome in a pediatric porcine model of asphyxial cardiac arrest when compared with epinephrine alone or with epinephrine plus vasopressin in combination. Accordingly, this study was designed to differentiate whether the inferior effects of vasopressin in pediatrics were caused by the type of cardiac arrest.

DESIGN

Prospective, randomized laboratory investigation that used an established porcine model for measurement of hemodynamic variables and organ blood flow.

SETTING

University hospital laboratory.

SUBJECTS

Eighteen piglets weighing 8-11 kg.

INTERVENTIONS

After 8 mins of ventricular fibrillation and 8 mins of cardiopulmonary resuscitation, either 0.4 units/kg vasopressin (n = 6), 45 microg/kg epinephrine (n = 6), or a combination of 45 microg/kg epinephrine with 0.8 units/kg vasopressin (n = 6) was administered. Six minutes after drug administration, a second respective bolus dose of 0.8 units/kg vasopressin, 200 microg/kg epinephrine, or a combination of 200 microg/kg epinephrine with 0.8 units/kg vasopressin was given. Defibrillation was attempted 20 mins after initiating cardiopulmonary resuscitation.

MEASUREMENTS AND MAIN RESULTS

Mean +/- sem left ventricular myocardial blood flow 2 mins after each respective drug administration was 65 +/- 4 and 70 +/- 13 mL x min(-1) x 100 g(-1) in the vasopressin group; 83 +/- 42 and 85 +/- 41 mL x min(-1) x 100 g(-1) in the epinephrine group; and 176 +/- 32 and 187 +/- 29 mL x min(-1) x 100 g(-1) in the epinephrine-vasopressin group (p <.006 after both doses of epinephrine-vasopressin vs. vasopressin and after the first dose of epinephrine-vasopressin vs. epinephrine, respectively). At the same times, mean +/- sem total cerebral blood flow was 73 +/- 3 and 47 +/- 5 mL x min(-1) x 100 g(-1) after vasopressin; 18 +/- 2 and 12 +/- 2 mL x min(-1) x 100 g(-1) after epinephrine; and 79 +/- 21 and 41 +/- 8 mL x min(-1) x 100 g(-1) after epinephrine-vasopressin (p <.025 after both doses of vasopressin and epinephrine-vasopressin vs. epinephrine). Five of six vasopressin-treated, two of six epinephrine-treated, and six of six epinephrine-vasopressin treated animals had return of spontaneous circulation (nonsignificant).

CONCLUSIONS

In this pediatric porcine model of ventricular fibrillation, the combination of epinephrine with vasopressin during cardiopulmonary resuscitation resulted in significantly higher levels of left ventricular myocardial blood flow than either vasopressin alone or epinephrine alone. Both vasopressin alone and the combination of epinephrine with vasopressin, but not epinephrine alone, improved total cerebral blood flow during cardiopulmonary resuscitation. In stark contrast to asphyxial cardiac arrest, vasopressin alone or in combination with epinephrine appears to be of benefit after ventricular fibrillation in the pediatric porcine model.

Role of epinephrine in acute stress

This article presents the likely pathway of stimuli generated by the recognition of high-intensity stressors to ultimately produce a fight-or-flight response. A key element is the recognition that psychological stressors that do not directly alter the internal environment represent the most important etiology of a fight-or-flight response. Adrenomedullary secretion is a critical component of that response; impromptu stimulation of the adrenal medulla can produce plasma epinephrine concentrations greater than 10,000 pg/mL. When these plasma levels reach the hypothalamus to act on the CNS, the result is facilitation of the decision making, and decision execution processes (fight-or-flight), and perhaps further sympathetic stimulation and vasopressin release. Subjects with underlying cardiovascular and/or metabolic pathology may be particularly susceptible to potentially lethal reactions to this neuroendocrine response. Additionally, since this biological reaction may be triggered by sudden changes in the social environment, the coordinated actions of epinephrine, sympathetic stimulation and vasopressin must be directed at not only optimizing the chances for survival, but also at attaining maximal preservation of the individual environmental and social domains.

Anesthesia-related cardiac arrest in children. An update

The improvement in mortality rates for anesthetized children over the past 50 years reflects the many improvements that have been made in pediatric perioperative care. The modern pediatric anesthesiologist is better trained than the predecessors of half a century ago, and has a vastly improved arsenal of monitoring devices and anesthetic agents from which to choose. The modern pediatric perioperative environment is better equipped to meet the unique needs of children. Techniques practiced by surgeons, nurses, radiologists, and pharmacologists help create a far more sophisticated infrastructure than existed 50 years ago. Given these changes, it is not surprising that outcomes for patients have improved.

Cerebral ischaemia in experimental cardiopulmonary resuscitation--comparison of epinephrine and aortic occlusion

The apparent inability of epinephrine to improve outcome after cardiopulmonary resuscitation (CPR) could be caused by direct negative effects on the cerebral circulation. Constant aortic occlusion with a balloon catheter could be an alternative way to improve coronary and cerebral perfusion during CPR. The objective of the present study was to compare the effects of standard-dose epinephrine with balloon occlusion of the descending aorta on cortical cerebral blood flow augmentation during CPR. Ventricular fibrillation was induced in 24 anaesthetised piglets. A non-intervention interval of 9 min was followed by open-chest CPR. The animals were randomised to receive repeated intravenous bolus doses of epinephrine 20 microg/kg or balloon occlusion of the descending aorta. Focal cortical cerebral blood flow was measured continuously using laser-Doppler flowmetry. Balloon occlusion of the aorta resulted in a significantly higher mean cortical cerebral blood flow and a lower cerebral oxygen extraction ratio than epinephrine during CPR. After restoration of spontaneous circulation the cerebral perfusion appeared compromised to the same extent in both groups, with lower blood flow compared to baseline, high cerebral oxygen extraction and cerebral tissue acidosis. No difference in cerebral cortical vascular resistance between the two groups could be detected. It is concluded that aortic balloon occlusion was superior to epinephrine in cerebral blood flow augmentation during resuscitation and did not generate adverse effects on cerebral blood flow, oxygenation or tissue pH after restoration of spontaneous circulation. No evidence of cerebral vasoconstriction induced by standard-dose epinephrine was found.

Medications during resuscitation -- what is the evidence?

Medication use during neonatal resuscitation is uncommon. The infrequent use of resuscitation medications has impeded rigorous investigations to determine the most effective agents and/or dosing regimens. The medications most commonly used during delivery room resuscitation include epinephrine, sodium bicarbonate, naloxone hydrochloride and volume expanders. The available evidence for each of these medications is reviewed in this article.

Differences in the pharmacodynamics of epinephrine and vasopressin during and after experimental cardiopulmonary resuscitation

Vasopressin has been investigated as a possible alternative to epinephrine during cardiopulmonary resuscitation (CPR). We tested the hypothesis that vasopressin, in comparison with epinephrine, would improve cerebral blood flow and metabolism during CPR as well as after restoration of spontaneous circulation (ROSC). A total of 22 anaesthetised piglets were subjected to 5 min of ventricular fibrillation followed by 8 min of closed-chest CPR. The piglets were randomly allocated to receive repeated boluses of either 45 microg/kg epinephrine or 0.4 U/kg vasopressin IV. Haemodynamic parameters, cerebral cortical blood flow and cerebral tissue pH and PCO(2) were continuously monitored during CPR and up to 4 h after ROSC. Cerebral oxygen extraction ratio was calculated. Cerebral cortical blood flow increased transiently after each bolus of epinephrine, while only the first bolus of vasopressin resulted in a sustained increase. The peak in cerebral cortical blood flow was reached approximately 30 s later with vasopressin. During the initial 5 min following ROSC, cerebral cortical blood flow was greater in the vasopressin group. In conclusion, there is a difference between epinephrine and vasopressin in the time from injection to maximal clinical response and the duration of their effect, but their overall effects on blood pressures and cerebral perfusion do not differ significantly during CPR. In contrast, vasopressin results in a greater cerebral cortical blood flow during a transient period after ROSC.

Intra-aortic administration of epinephrine above an aortic balloon occlusion during experimental CPR does not further improve cerebral blood flow and oxygenation

Balloon occlusion of the descending aorta during cardiopulmonary resuscitation (CPR) improves coronary and cerebral blood flow. In comparison with an equivalent dose administered through a central venous catheter it has been suggested that epinephrine administration above the aortic occlusion might produce a more rapid increase in coronary perfusion pressure and a shorter time to restoration of spontaneous circulation (ROSC). In a recent study, however, outcome was not improved after intra-aortic epinephrine administration. We hypothesised that epinephrine administered above the aortic occlusion could impose adverse effects on cerebral blood flow and oxygenation, possibly because of an alpha-adrenergic mediated vasoconstriction in the cerebral vascular beds. Twenty-six piglets underwent 5 min of non intervention cardiac arrest followed by 8 min of closed-chest CPR. They were randomised to receive bolus doses of 45 microg/kg epinephrine either above the aortic occlusion or through a central venous catheter. Cerebral cortical blood flow was continuously measured using laser-Doppler technique. Cerebral tissue pH and PCO(2) were also measured using a multi-parameter fiberoptic device and cerebral oxygen extraction was calculated. Balloon inflation resulted in an immediate enhancement of cerebral cortical blood flow. Each of the epinephrine boluses through the central venous catheter resulted in a transient increase in cerebral cortical blood flow. When administered above the aortic balloon occlusion, epinephrine did not result in a further increase in cerebral cortical blood flow, though a significant increase in cerebral perfusion pressure was recorded throughout the CPR period. Cerebral tissue pH monitoring revealed severe acidosis during CPR and long after ROSC, which was refractory to buffering. No differences in the cerebral oxygen extraction ratio were observed between the groups. In conclusion, epinephrine administration above an aortic balloon occlusion was unable to improve cerebral blood flow and oxygenation. In fact, it may even attenuate the beneficial effects of aortic balloon occlusion on cerebral blood flow due to an alpha-adrenergic mediated cerebral vasoconstriction. Further studies, including dose-response and volumes of distribution, are needed to identify the effective beneficial dosage of epinephrine during aortic occlusion with the least possible adverse effects.