Randomized trial of volume infusion during resuscitation of asphyxiated neonatal piglets

Femoral Occlusion during Neonatal Cardiopulmonary Resuscitation Improves Outcomes in an Ovine Model of Perinatal Cardiac Arrest

BACKGROUND

The goal of chest compressions during neonatal resuscitation is to increase cerebral and coronary blood flow leading to the return of spontaneous circulation (ROSC). During chest compressions, bilateral femoral occlusion may increase afterload and promote carotid and coronary flow, an effect similar to epinephrine. Our objectives were to determine the impact of bilateral femoral occlusion during chest compressions on the incidence and timing of ROSC and hemodynamics.

METHODOLOGY

In this randomized study, 19 term fetal lambs in cardiac arrest were resuscitated based on the Neonatal Resuscitation Program guidelines and randomized into two groups: femoral occlusion or controls. Bilateral femoral arteries were occluded by applying pressure using two fingers during chest compressions.

RESULTS

Seventy percent (7/10) of the lambs in the femoral occlusion group achieved ROSC in 5 ± 2 min and three lambs (30%) did not receive epinephrine. ROSC was achieved in 44% (4/9) of the controls in 13 ± 6 min and all lambs received epinephrine. The femoral occlusion group had higher diastolic blood pressures, carotid and coronary blood flow.

CONCLUSION

Femoral occlusion resulted in faster and higher incidence of ROSC, most likely due to attaining increased diastolic pressures, coronary and carotid flow. This is a low-tech intervention that can be easily adapted in resource limited settings, with the potential to improve survival and neurodevelopmental outcomes.

Role of Volume Replacement during Neonatal Resuscitation in the Delivery Room

Volume expanders are indicated in the delivery room when an asphyxiated neonate is not responding to the steps of neonatal resuscitation and has signs of shock or a history of acute blood loss. Fetal blood loss (e.g., feto-maternal hemorrhage) may contribute to perinatal asphyxia. Cord compression or a tight nuchal cord can selectively occlude a thin-walled umbilical vein, resulting in feto-placental transfusion and neonatal hypovolemia. For severe bradycardia or cardiac arrest secondary to fetal blood loss, Neonatal Resuscitation Program (NRP) recommends intravenous volume expanders (crystalloids such as normal saline or packed red blood cells) infused over 5 to 10 min. Failure to recognize hypovolemia and subsequent delay in volume replacement may result in unsuccessful resuscitation due to lack of adequate cardiac preload. However, excess volume load in the presence of myocardial dysfunction from hypoxic–ischemic injury may precipitate pulmonary edema and intraventricular hemorrhage (especially in preterm infants). Emergent circumstances and ethical concerns preclude the performance of prospective clinical studies evaluating volume replacement during neonatal resuscitation. Translational studies, observational data from registries and clinical trials are needed to investigate and understand the role of volume replacement in the delivery room in term and preterm neonates. This article is a narrative review of the causes and consequences of acute fetal blood loss and available evidence on volume replacement during neonatal resuscitation of asphyxiated neonates.

Singapore Neonatal Resuscitation Guidelines 2021

Neonatal resuscitation is a coordinated, team-based series of timed sequential steps that focuses on a transitional physiology to improve perinatal and neonatal outcomes. The practice of neonatal resuscitation has evolved over time and continues to be shaped by emerging evidence as well as key opinions. We present the revised Neonatal Resuscitation Guidelines for Singapore 2021. The recommendations from the International Liaison Committee on Resuscitation Neonatal Task Force Consensus on Science and Treatment Recommendations (2020) and guidelines from the American Heart Association and European Resuscitation Council were compared with existing guidelines. The recommendations of the Neonatal Subgroup of the Singapore Resuscitation and First Aid Council were derived after the work group discussed and appraised the current available evidence and their applicability to local clinical practice.

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.

Animal models in neonatal resuscitation research: What can they teach us?

Animal models have made and continue to make important contributions to neonatal medicine. For example, studies in fetal sheep have taught us much about the physiology of the fetal-to-neonatal transition. However, whereas animal models allow multiple factors to be investigated in a logical and systematic manner, no animal model is perfect for humans and so we need to understand the fundamental differences in physiology between the species in question and humans. Although most physiological systems are well conserved between species, some small differences exist and so wherever possible the knowledge generated from preclinical studies in animals should be tested in clinical trials. However, with the rise of evidence-based medicine the distinction between scientific knowledge generation and evidence gathering has been confused and the two have been lumped together. This misunderstands the contribution that scientific knowledge can provide. Science should be used to guide the gathering of evidence by informing the design of clinical trials, thereby increasing their likelihood of success. While scientific knowledge is not evidence, in the absence of evidence it is likely to be the best option for guiding clinical practice.

Successful Resuscitation in a Model of Asphyxia and Hemorrhage to Test Different Volume Resuscitation Strategies. A Study in Newborn Piglets After Transition

Background: Evidence for recommendations on the use of volume expansion during cardiopulmonary resuscitation in newborn infants is limited. Objectives: To develop a newborn piglet model with asphyxia, hemorrhage, and cardiac arrest to test different volume resuscitation on return of spontaneous circulation (ROSC). We hypothesized that immediate red cell transfusion reduces time to ROSC as compared to the use of an isotonic crystalloid fluid. Methods: Forty-four anaesthetized and intubated newborn piglets [age 32 h (12-44 h), weight 1,220 g (1,060-1,495g), Median (IQR)] were exposed to hypoxia and blood loss until asystole occurred. At this point they were randomized into two groups: (1) Crystalloid group: receiving isotonic sodium chloride (n = 22). (2) Early transfusion group: receiving blood transfusion (n = 22). In all other ways the piglets were resuscitated according to ILCOR 2015 guidelines [including respiratory support, chest compressions (CC) and epinephrine use]. One hour after ROSC piglets from the crystalloid group were randomized in two sub-groups: late blood transfusion and infusion of isotonic sodium chloride to investigate the effects of a late transfusion on hemodynamic parameters. Results: All animals achieved ROSC. Comparing the crystalloid to early blood transfusion group blood loss was 30.7 ml/kg (22.3-39.6 ml/kg) vs. 34.6 ml/kg (25.2-44.7 ml/kg), Median (IQR). Eleven subjects did not receive volume expansion as ROSC occurred rapidly. Thirty-three animals received volume expansion (16 vs. 17 in the crystalloid vs. early transfusion group). 14.1% vs. 10.5% of previously extracted blood volume in the crystalloid vs. early transfusion group was infused before ROSC. There was no significant difference in time to ROSC between groups [crystalloid group: 164 s (129-198 s), early transfusion group: 163 s (162-199 s), Median (IQR)] with no difference in epinephrine use. Conclusions: Early blood transfusion compared to crystalloid did not reduce time to ROSC, although our model included only a moderate degree of hemorrhage and ROSC occurred early in 11 subjects before any volume resuscitation occurred.

Optimising Intravenous Volume Resuscitation of the Newborn in the Delivery Room: Practical Considerations and Gaps in Knowledge

Volume resuscitation (VR) for the treatment of newborn shock is a rare but potentially lifesaving intervention. Conducting clinical studies to assess the effectiveness of VR in the delivery room during newborn stabilization is challenging. We review the available literature and current management guidelines to determine which infants will benefit from VR, the frequency of VR, and the choice of agents used. In addition, the potential role for placental transfusion in the prevention of newborn shock is explored.

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.

Cellular biology of end organ injury and strategies for prevention of injury

The interruption of placental blood flow induces circulatory responses to maintain cerebral, cardiac, and adrenal blood flow with reduced renal, hepatic, intestinal, and skin blood flow. If placental compromise is prolonged and/or severe, total circulatory failure is likely with cerebral hypoperfusion and resultant hypoxic ischemic cerebral injury with collateral renal, cardiac, and hepatic injury. Management strategies should be targeted at restoring cerebral perfusion and oxygen delivery and minimizing the extent of secondary injury. Specifically, the focus should include the judicious use of supplemental oxygen, avoidance of hypoglycemia and elevated temperature in the delivery room, and the early administration of therapeutic hypothermia to high-risk infants.

Antioxidant protects against increases in low molecular weight hyaluronan and inflammation in asphyxiated newborn pigs resuscitated with 100% oxygen

BACKGROUND

Newborn resuscitation with 100% oxygen is associated with oxidative-nitrative stresses and inflammation. The mechanisms are unclear. Hyaluronan (HA) is fragmented to low molecular weight (LMW) by oxidative-nitrative stresses and can promote inflammation. We examined the effects of 100% oxygen resuscitation and treatment with the antioxidant, N-acetylcysteine (NAC), on lung 3-nitrotyrosine (3-NT), LMW HA, inflammation, TNFα and IL1ß in a newborn pig model of resuscitation.

METHODS & PRINCIPAL FINDINGS

Newborn pigs (n = 40) were subjected to severe asphyxia, followed by 30 min ventilation with either 21% or 100% oxygen, and were observed for the subsequent 150 minutes in 21% oxygen. One 100% oxygen group was treated with NAC. Serum, bronchoalveolar lavage (BAL), lung sections, and lung tissue were obtained. Asphyxia resulted in profound hypoxia, hypercarbia and metabolic acidosis. In controls, HA staining was in airway subepithelial matrix and no 3-NT staining was seen. At the end of asphyxia, lavage HA decreased, whereas serum HA increased. At 150 minutes after resuscitation, exposure to 100% oxygen was associated with significantly higher BAL HA, increased 3NT staining, and increased fragmentation of lung HA. Lung neutrophil and macrophage contents, and serum TNFα and IL1ß were higher in animals with LMW than those with HMW HA in the lung. Treatment of 100% oxygen animals with NAC blocked nitrative stress, preserved HMW HA, and decreased inflammation. In vitro, peroxynitrite was able to fragment HA, and macrophages stimulated with LMW HA increased TNFα and IL1ß expression.

CONCLUSIONS & SIGNIFICANCE

Compared to 21%, resuscitation with 100% oxygen resulted in increased peroxynitrite, fragmentation of HA, inflammation, as well as TNFα and IL1ß expression. Antioxidant treatment prevented the expression of peroxynitrite, the degradation of HA, and also blocked increases in inflammation and inflammatory cytokines. These findings provide insight into potential mechanisms by which exposure to hyperoxia results in systemic inflammation.

Resuscitation of the term and preterm infant

Resuscitation is one of the most frequently performed procedures in the neonatal period. Since the most recent guidelines from the International Liaison Committee on Resuscitation (ILCOR) appeared in 2005, experimental and clinical research has introduced changes regarding the different components of the procedure, with the common denominator being the least aggressive to the baby. Babies should be kept warm, avoiding suctioning as a general rule, adjusting pressure, volume and oxygen to the minimum to achieve stabilisation without causing harm to the airways or oxidative stress, and applying all the available technology in the delivery room before transportation to the neonatal intensive care unit. The response to ventilation should primarily be assessed by the heart rate. Babies of gestational age >or=32 weeks should be ventilated initially with 21% oxygen and if <32 weeks with 21-30% oxygen. Intubation, chest compressions, use of drugs or volume therapy are rarely needed in term or near term babies in need of resuscitation. The first minutes of life are decisive, and what we do during these minutes will have unequivocal influence later on.

Post-resuscitation strategies to avoid ongoing injury following intrapartum hypoxia-ischemia

The interruption of placental blood flow during labor with redistribution of cardiac output resulting in increased flow to brain, heart, and adrenal glands at the expense of flow to kidney, gut, and skin can result in systemic organ as well as cerebral injury. Thus, post-resuscitation strategies should focus on both the management of potential systemic organ dysfunction and on methods of preventing ongoing brain injury in high-risk infants. General management strategies should include ventilator management to maintain pCO(2) values in the normal range, close attention to blood pressure to avoid hypotension, striving to avoid hypoglycemia, and control of seizures. Modest hypothermia administered within the first 6 hours has been shown to reduce neurodevelopmental deficits and death in those infants at highest-risk infants for developing hypoxic-ischemic brain injury.

Ubiquitin enhances the Th2 cytokine response and attenuates ischemia-reperfusion injury in the lung

OBJECTIVE

To determine whether ubiquitin treatment modulates the lung cytokine response and attenuates lung ischemia-reperfusion injury.

DESIGN AND SETTING

Randomized and blinded treatment of unilateral lung ischemia-reperfusion injury in a research laboratory.

SUBJECTS

Twenty anesthetized and mechanically ventilated Brown Norway rats.

INTERVENTIONS

Unilateral clamping of the left lung for 90 mins followed by 60 mins of reperfusion. Intravenous administration of 1.5 mg/kg of ubiquitin (n = 10) or albumin (n = 10) 5 mins before reperfusion.

MEASUREMENTS AND MAIN RESULTS

Blood pressure was measured by the tail-cuff method. Oxygenation via the ischemic lung was assessed by PaO2 measurements after right lung exclusion. Wet-to-dry weight ratios of the ischemic lungs were determined gravimetrically. Tissue homogenates (n = 5/group) were prepared from ischemic lungs at the end of reperfusion and assayed for malondialdehyde in combination with 4-hydroxyalkenals to assess lipid peroxidation, and for a panel of 22 cytokines/chemokines using a multiplex assay. Ubiquitin serum levels were determined by enzyme-linked immunosorbent assay.All animals were hemodynamically stable during the experimental procedure. Ubiquitin serum levels (mean +/- SD) were 650 +/- 40 ng/mL in controls and 1206 +/- 181 ng/mL in the ubiquitin treatment group at the end of the experiment. PaO2 after right lung exclusion was 45 (32-72) mm Hg with albumin and 61 (range, 36-132) mm Hg with ubiquitin (p = .0185). Wet-to-dry weight ratios of the injured lungs were 8.7 (range, 5.5-19.1) and 7.8 (range, 5.7-8.3) in the albumin and ubiquitin groups, respectively (p = .035). Malondialdehyde/4-hydroxyalkenals concentrations (mean +/- SD, nmol/mg protein) were 2.5 +/- 0.4 with ubiquitin and 3.0 +/- 0.3 with albumin (p > .05). Concentrations of the interleukins 4, 10, and 13 were significantly increased in lung homogenates after ubiquitin treatment (p < .05).

CONCLUSION

Ubiquitin treatment enhances the Th2 cytokine response in postischemic lungs during reperfusion, reduces lung edema formation, and improves pulmonary function during lung ischemia-reperfusion injury. This study further defines ubiquitin's anti-inflammatory properties, and suggests that it could be used therapeutically to improve function of postischemic lungs.

Moving from experience to evidence: changes in US Neonatal Resuscitation Program based on International Liaison Committee on Resuscitation Review

The Neonatal Workgroup of the International Liaison Committee on Resuscitation recently made available their rigorous review of the scientific evidence base for selected neonatal resuscitation issues. The Neonatal Resuscitation Program guidelines have been recently revised based on that review and published as the Textbook of Neonatal Resuscitation, 5th edn. This review article highlights pertinent changes in recommendations, including revisions in: oxygen use; CO(2) detectors for confirmation of intubation; management of the infant born through meconium-stained amniotic fluid; initial ventilation devices and strategies; thermal protection of very small preterm infants; medications, including doses and routes of delivery; postresuscitation therapies for consideration and ethical issues in initiation and discontinuation of resuscitation. Journal of Perinatology (2008) 28, S35-S40; doi:10.1038/jp.2008.48.