Corrigendum: An extra-uterine system to physiologically support the extreme premature lamb.

This corrects the article DOI: 10.1038/ncomms15112.

An extra-uterine system to physiologically support the extreme premature lamb.

In the developed world, extreme prematurity is the leading cause of neonatal mortality and morbidity due to a combination of organ immaturity and iatrogenic injury. Until now, efforts to extend gestation using extracorporeal systems have achieved limited success. Here we report the development of a system that incorporates a pumpless oxygenator circuit connected to the fetus of a lamb via an umbilical cord interface that is maintained within a closed 'amniotic fluid' circuit that closely reproduces the environment of the womb. We show that fetal lambs that are developmentally equivalent to the extreme premature human infant can be physiologically supported in this extra-uterine device for up to 4 weeks. Lambs on support maintain stable haemodynamics, have normal blood gas and oxygenation parameters and maintain patency of the fetal circulation. With appropriate nutritional support, lambs on the system demonstrate normal somatic growth, lung maturation and brain growth and myelination.

Volume infusion cooling increases end-tidal carbon dioxide and results in faster and deeper cooling during intra-cardiopulmonary resuscitation hypothermia induction.

BACKGROUND: Intra-arrest hypothermia induction may provide more benefit than inducing hypothermia after return of spontaneous circulation. However, little is understood about the interaction between patient physiology and hypothermia induction technology choice during ongoing chest compressions. METHODS: After 10 min of untreated ventricular fibrillation, mechanical chest compressions were provided for 60 min (100 CPM, 1.25" deep) in 26 domestic swine (30.5 ± 1.7 kg) with concurrent hypothermia induction using one of eight cooling methods. Four cooling methods included volume infusion with cold saline or an ice particulate slurry through the femoral vein or carotid artery (volume infusion cooling group, VC); three included cooling via an intra-vascular heat exchange catheter, nasal cooling, or surface ice bags (no volume cooling group, NVC); and the other was a control group with no cooling (no cooling group, NC). Physiological monitoring included end-tidal carbon dioxide, aortic pressure, right atrial pressure, brain temperature, esophageal temperature, and rectal temperature. RESULTS: During cardiopulmonary resuscitation (CPR), the volume infusion cooling group cooled faster and to lower temperatures than the other groups (VC vs. NVC or NC; ∆T = -5.6 vs. -2.1 °C or -0.6 °C; p < 0.01). The aortic pressure and right atrial pressure were higher in the volume cooling group than the other groups (VC vs. NVC or NC; AOP = 23.6 vs. 16.7 mmHg or 14.7 mmHg; p < 0.02). End-tidal carbon dioxide measurements during CPR were also higher in the volume cooling group (VC vs. NVC; EtCO2 = 23.4 vs. 13.1 mmHg; p < 0.05). Intra-corporeal temperature gradients larger than 3 °C were created by volume cooling during ongoing chest compressions. CONCLUSIONS: Volume infusion cooling significantly altered physiology relative to other cooling methods during ongoing chest compressions. Volume cooling led to faster cooling rates, lower temperatures, higher end-tidal carbon dioxide levels, and higher central vascular pressures. IACUC protocol numbers: UPenn (803178), CHOP (997).

Developing a kinematic understanding of chest compressions: the impact of depth and release time on blood flow during cardiopulmonary resuscitation.

BACKGROUND: Effective cardiopulmonary resuscitation is a critical component of the pre-hospital treatment of cardiac arrest victims. Mechanical chest compression (MCC) devices enable the delivery of MCC waveforms that could not be delivered effectively by hand. While chest compression generated blood flow has been studied for more than 50 years, the relation between sternum kinematics (depth over time) and the resulting blood flow have not been well described. Using a five parameter MCC model, we studied the effect of MCC depth, MCC release time, and their interaction on MCC generated blood flow in a highly instrumented swine model of cardiac arrest. METHODS: MCC hemodynamics were studied in 17 domestic swine (~30 kg) using multiple extra-vascular flow probes and standard physiological monitoring. After 10 min of untreated ventricular fibrillation, mechanical MCC were started. MCC varied such that sternal release occurred over 100, 200, or 300 ms. MCC were delivered at a rate of 100 per min and at a depth of 1.25″ (n = 9) or at a depth of 1.9″ (n = 8) for a total of 18 min. Transitions between release times occurred every 2 min and were randomized. Linear Mixed Models were used to estimate the effect of MCC depth, MCC release time, and the interaction between MCC depth and release time on physiological outcomes. RESULTS: Blood pressures were optimized by a 200 ms release. End tidal carbon dioxide (EtCO2) was optimized by a 100 ms release. Blood flows were significantly lower at a 300 ms release than at either a 100 or 200 ms release (p < 0.05). 1.9″ deep MCC improved EtCO2, right atrial pressure, coronary perfusion pressure, inferior vena cava blood flow, carotid blood flow, and renal vein blood flow relative to 1.25″ MCC. CONCLUSIONS: Deeper MCC improved several hemodynamic parameters. Chest compressions with a 300 ms release time generated less blood flow than chest compressions with faster release times. MCC release time is an important quantitative metric of MCC quality and, if optimized, could improve MCC generated blood flows and pressures.

Patient-centric blood pressure-targeted cardiopulmonary resuscitation improves survival from cardiac arrest.

RATIONALE: Although current resuscitation guidelines are rescuer focused, the opportunity exists to develop patient-centered resuscitation strategies that optimize the hemodynamic response of the individual in the hopes to improve survival. OBJECTIVES: To determine if titrating cardiopulmonary resuscitation (CPR) to blood pressure would improve 24-hour survival compared with traditional CPR in a porcine model of asphyxia-associated ventricular fibrillation (VF). METHODS: After 7 minutes of asphyxia, followed by VF, 20 female 3-month-old swine randomly received either blood pressure-targeted care consisting of titration of compression depth to a systolic blood pressure of 100 mm Hg and vasopressors to a coronary perfusion pressure greater than 20 mm Hg (BP care); or optimal American Heart Association Guideline care consisting of depth of 51 mm with standard advanced cardiac life support epinephrine dosing (Guideline care). All animals received manual CPR for 10 minutes before first shock. Primary outcome was 24-hour survival. MEASUREMENTS AND MAIN RESULTS: The 24-hour survival was higher in the BP care group (8 of 10) compared with Guideline care (0 of 10); P = 0.001. Coronary perfusion pressure was higher in the BP care group (point estimate +8.5 mm Hg; 95% confidence interval, 3.9-13.0 mm Hg; P < 0.01); however, depth was higher in Guideline care (point estimate +9.3 mm; 95% confidence interval, 6.0-12.5 mm; P < 0.01). Number of vasopressor doses before first shock was higher in the BP care group versus Guideline care (median, 3 [range, 0-3] vs. 2 [range, 2-2]; P = 0.003). CONCLUSIONS: Blood pressure-targeted CPR improves 24-hour survival compared with optimal American Heart Association care in a porcine model of asphyxia-associated VF cardiac arrest.

Hemodynamic directed CPR improves cerebral perfusion pressure and brain tissue oxygenation.

AIM: Advances in cardiopulmonary resuscitation (CPR) have focused on the generation and maintenance of adequate myocardial blood flow to optimize the return of spontaneous circulation and survival. Much of the morbidity associated with cardiac arrest survivors can be attributed to global brain hypoxic ischemic injury. The objective of this study was to compare cerebral physiological variables using a hemodynamic directed resuscitation strategy versus an absolute depth-guided approach in a porcine model of ventricular fibrillation (VF) cardiac arrest. METHODS: Intracranial pressure and brain tissue oxygen tension probes were placed in the frontal cortex prior to induction of VF in 21 female 3-month-old swine. After 7 min of VF, animals were randomized to receive one of three resuscitation strategies: (1) hemodynamic directed care (CPP-20): chest compressions (CCs) with depth titrated to a target systolic blood pressure of 100 mmHg and titration of vasopressors to maintain coronary perfusion pressure (CPP)>20 mmHg; (2) depth 33 mm (D33): target CC depth of 33 mm with standard American Heart Association (AHA) epinephrine dosing; or (3) depth 51 mm (D51): target CC depth of 51 mm with standard AHA epinephrine dosing. RESULTS: Cerebral perfusion pressures (CerePP) were significantly higher in the CPP-20 group compared to both D33 (p<0.01) and D51 (p=0.046), and higher in survivors compared to non-survivors irrespective of treatment group (p<0.01). Brain tissue oxygen tension was also higher in the CPP-20 group compared to both D33 (p<0.01) and D51 (p=0.013), and higher in survivors compared to non-survivors irrespective of treatment group (p<0.01). Subjects with a CPP>20 mmHg were 2.7 times more likely to have a CerePP>30 mmHg (p<0.001). CONCLUSIONS: Hemodynamic directed resuscitation strategy targeting coronary perfusion pressure>20 mmHg following VF arrest was associated with higher cerebral perfusion pressures and brain tissue oxygen tensions during CPR.

Hemodynamic-directed cardiopulmonary resuscitation during in-hospital cardiac arrest.

Cardiopulmonary resuscitation (CPR) guidelines assume that cardiac arrest victims can be treated with a uniform chest compression (CC) depth and a standardized interval administration of vasopressor drugs. This non-personalized approach does not incorporate a patient's individualized response into ongoing resuscitative efforts. In previously reported porcine models of hypoxic and normoxic ventricular fibrillation (VF), a hemodynamic-directed resuscitation improved short-term survival compared to current practice guidelines. Skilled in-hospital rescuers should be trained to tailor resuscitation efforts to the individual patient's physiology. Such a strategy would be a major paradigm shift in the treatment of in-hospital cardiac arrest victims.

Hemodynamic directed cardiopulmonary resuscitation improves short-term survival from ventricular fibrillation cardiac arrest.

OBJECTIVES: During cardiopulmonary resuscitation, adequate coronary perfusion pressure is essential for establishing return of spontaneous circulation. Current American Heart Association guidelines recommend standardized interval administration of epinephrine for patients in cardiac arrest. The objective of this study was to compare short-term survival using a hemodynamic directed resuscitation strategy versus chest compression depth-directed cardiopulmonary resuscitation in a porcine model of cardiac arrest. DESIGN: Randomized interventional study. SETTING: Preclinical animal laboratory. SUBJECTS: Twenty-four 3-month-old female swine. INTERVENTIONS: After 7 minutes of ventricular fibrillation, pigs were randomized to receive one of three resuscitation strategies: 1) Hemodynamic directed care (coronary perfusion pressure-20): chest compressions with depth titrated to a target systolic blood pressure of 100 mm Hg and titration of vasopressors to maintain coronary perfusion pressure greater than 20 mm Hg; 2) Depth 33 mm: target chest compression depth of 33 mm with standard American Heart Association epinephrine dosing; or 3) Depth 51 mm: target chest compression depth of 51 mm with standard American Heart Association epinephrine dosing. All animals received manual cardiopulmonary resuscitation guided by audiovisual feedback for 10 minutes before first shock. MEASUREMENTS AND MAIN RESULTS: Forty-five-minute survival was higher in the coronary perfusion pressure-20 group (8 of 8) compared to depth 33 mm (1 of 8) or depth 51 mm (3 of 8) groups; p equals to 0.002. Coronary perfusion pressures were higher in the coronary perfusion pressure-20 group compared to depth 33 mm (p = 0.004) and depth 51 mm (p = 0.006) and in survivors compared to nonsurvivors (p < 0.01). Total epinephrine dosing and defibrillation attempts were not different. CONCLUSIONS: Hemodynamic directed resuscitation targeting coronary perfusion pressures greater than 20 mm Hg during 10 minutes of cardiopulmonary resuscitation for ventricular fibrillation cardiac arrest improves short-term survival, when compared to resuscitation with depth of compressions guided to 33 mm or 51 mm and standard American Heart Association vasopressor dosing.

Role of phenylalanine B10 in plant nonsymbiotic hemoglobins.

All plants contain an unusual class of hemoglobins that display bis-histidyl coordination yet are able to bind exogenous ligands such as oxygen. Structurally homologous hexacoordinate hemoglobins (hxHbs) are also found in animals (neuroglobin and cytoglobin) and some cyanobacteria, where they are thought to play a role in free radical scavenging or ligand sensing. The plant hxHbs can be distinguished from the others because they are only weakly hexcacoordinate in the ferrous state, yet no structural mechanism for regulating hexacoordination has been articulated to account for this behavior. Plant hxHbs contain a conserved Phe at position B10 (Phe(B10)), which is near the reversibly coordinated distal His(E7). We have investigated the effects of Phe(B10) mutation on kinetic and equilibrium constants for hexacoordination and exogenous ligand binding in the ferrous and ferric oxidation states. Kinetic and equilibrium constants for hexacoordination and ligand binding along with CO-FTIR spectroscopy, midpoint reduction potentials, and the crystal structures of two key mutant proteins (F40W and F40L) reveal that Phe(B10) is an important regulatory element in hexacoordination. We show that Phe at this position is the only amino acid that facilitates stable oxygen binding to the ferrous Hb and the only one that promotes ligand binding in the ferric oxidation states. This work presents a structural mechanism for regulating reversible intramolecular coordination in plant hxHbs.

Bis-histidyl hexacoordination in hemoglobins facilitates heme reduction kinetics.

Hexacoordinate hemoglobins are a class of proteins that exhibit reversible bis-histidyl coordination of the heme iron while retaining the ability to bind exogenous ligands. One hypothesis for their physiological function is that they scavenge nitric oxide, a reaction that oxidizes the protein and requires reduction of the heme iron to continue. Reduction kinetics of hexacoordinate hemoglobins, including human neuroglobin and cytoglobin, and those from Synechocystis and rice, are compared to myoglobin, soybean leghemoglobin, and several relevant mutant proteins. In all cases, bis-histidyl coordination greatly increases the rate of reduction by sodium dithionite when compared to pentacoordinate hemoglobins. In myoglobin and leghemoglobin, reduction is limited by the rate constant for electron transfer, whereas in the hexacoordinate hemoglobins reduction is limited only by bimolecular binding of the reductant. These results can be explained by differences in the reorganization energy for reduction between hexacoordinate and pentacoordinate hemoglobins.

Amphotericin B binds to amyloid fibrils and delays their formation: a therapeutic mechanism?

The membrane-active antifungal agent amphotericin B (AmB) is one of the few agents shown to slow the course of prion diseases in animals. Congo Red and other small molecules have been reported to directly inhibit amyloidogenesis in both prion and Alzheimer peptide model systems via specific binding. We propose that it is possible that AmB may act similarly to physically prevent conversion of the largely alpha-helical prion protein (PrP) to the pathological beta-sheet aggregate protease-resistant isoform (PrP(res)) in prion disease and by analogy prevent fibrillization in amyloid diseases. To assess whether AmB is capable of binding specifically to amyloid fibrils as does Congo Red, we have used the insulin fibril and Abeta 25-35 amyloid model fibril system. We find that AmB does bind strongly to both insulin (K(d) = 1.1 microM) and Abeta 25-35 amyloid (K(d) = 6.4 microM) fibrils but not to native insulin. Binding is characterized by a red-shifted AmB spectrum indicative of a more hydrophobic environment. Thus AmB seems to have a complementary face for amyloid fibrils but not the native protein. In addition, AmB interacts specifically with Congo Red, a known fibril-binding agent. In kinetic fibril formation studies, AmB was able to significantly kinetically delay the formation of Abeta 25-35 fibrils at pH 7.4 but not insulin fibrils at pH 2.