Spontaneous gasping produces carotid blood flow during untreated cardiac arrest

Hypoxia evokes a sequence of raphe-pontomedullary network operations for inspiratory drive amplification and gasping

Hypoxia can trigger a sequence of breathing-related behaviors, from tachypnea to apneusis to apnea and gasping, an autoresuscitative behavior that, via large tidal volumes and altered intrathoracic pressure, can enhance coronary perfusion, carotid blood flow, and sympathetic activity, and thereby coordinate cardiac and respiratory functions. We tested the hypothesis that hypoxia-evoked gasps are amplified through a disinhibitory microcircuit within the inspiratory neuron chain and a distributed efference copy mechanism that generates coordinated gasp-like discharges concurrently in other circuits of the raphe-pontomedullary respiratory network. Data were obtained from 6 decerebrate, vagotomized, neuromuscularly-blocked, and artificially ventilated adult cats. Arterial blood pressure, phrenic nerve activity, end-tidal CO2, and other parameters were monitored. Hypoxia was produced by ventilation with a gas mixture of 5% O2 in nitrogen (N2). Neuron spike trains were recorded at multiple pontomedullary sites simultaneously and evaluated for firing rate modulations and short-time scale correlations indicative of functional connectivity. Experimental perturbations evoked reconfiguration of raphe-pontomedullary circuits during tachypnea, apneusis and augmented bursts, apnea, and gasping. The functional connectivity, altered firing rates, efference copy of gasp drive, and coordinated step increments in blood pressure reported here support a distributed brain stem network model for amplification and broadcasting of inspiratory drive during autoresuscitative gasping that begins with a reduction in inhibition by expiratory neurons and an initial loss of inspiratory drive during hypoxic apnea.

Autoresuscitation and pheochromocytoma multisystem crisis in a dog

OBJECTIVE

To describe the clinical course of a dog with a pheochromocytoma multisystem crisis that exhibited autoresuscitation after cardiac arrest.

CASE SUMMARY

An approximately 10-year-old male neutered terrier mix dog presented for collapse. Abdominal imaging was suggestive of a pheochromocytoma, and clinical pathology data and thoracic imaging suggested the presence of a multisystem crisis. The dog developed cardiopulmonary arrest that was followed by autoresuscitation.

NEW OR UNIQUE INFORMATION PROVIDED

To the authors' knowledge, this is the first report of autoresuscitation in a dog. The phenomenon may have been associated with a pheochromocytoma multisystem crisis.

Association between serum lactate level during cardiopulmonary resuscitation and survival in adult out-of-hospital cardiac arrest: a multicenter cohort study

We aimed to investigate the association between serum lactate levels during cardiopulmonary resuscitation (CPR) and survival in patients with out-of-hospital cardiac arrest (OHCA). From the database of a multicenter registry on OHCA patients, we included adult nontraumatic OHCA patients transported to the hospital with ongoing CPR. Based on the serum lactate levels during CPR, the patients were divided into four quartiles: Q1 (≤ 10.6 mEq/L), Q2 (10.6-14.1 mEq/L), Q3 (14.1-18.0 mEq/L), and Q4 (> 18.0 mEq/L). The primary outcome was 1-month survival. Among 5226 eligible patients, the Q1 group had the highest 1-month survival (5.6% [74/1311]), followed by Q2 (3.6% [47/1316]), Q3 (1.7% [22/1292]), and Q4 (1.0% [13/1307]) groups. In the multivariable logistic regression analysis, the adjusted odds ratio of Q4 compared with Q1 for 1-month survival was 0.24 (95% CI 0.13-0.46). 1-month survival decreased in a stepwise manner as the quartiles increased (p for trend < 0.001). In subgroup analysis, there was an interaction between initial rhythm and survival (p for interaction < 0.001); 1-month survival of patients with a non-shockable rhythm decreased when the lactate levels increased (p for trend < 0.001), but not in patients with a shockable rhythm (p for trend = 0.72). In conclusion, high serum lactate level during CPR was associated with poor 1-month survival in OHCA patients, especially in patients with non-shockable rhythm.

The Pathophysiology of Dying

The pathophysiology of dying and death, related to veterinary patients, has warranted less attention than normal and abnormal physiologic processes related to life preservation. In addition, many veterinary patients are euthanized, which prevents observation of natural disease progression, while ameliorating suffering. Acute death in human medicine can serve as a model for understanding mechanisms of death in veterinary patients under certain conditions. The specific cause of cardiac arrest in several different models of disease elucidates end-stage disease processes. Understanding the path to death and dying in veterinary patients physiologically serves to guide best practices focused on alleviating suffering.

An Objective Exploration of Euthanasia and Adverse Events

Companion animal euthanasia is of great emotional, social, ethical, and medical significance because of the strong bond between pets and their owners. Few studies exist quantifying adverse events during and after euthanasia. Such events have profound effects on pet owners, veterinary professionals and veterinary patients. Best practices or standards of care have yet to be established. Companion animal euthanasia warrants further rigorous investigation regarding current veterinary medical practices due to its significant, complex, and far-reaching effects. Literature evaluating human euthanasia and assisted death in countries where such practices are legal can be a useful area of investigation and collaborative inquiry.

The presence of gasping predicts long-term survival in out-of-hospital cardiac arrest patients

BACKGROUND

The presence of gasping in out-of-hospital cardiac arrest (OHCA) patients predicts short-term prognosis. We performed a retrospective study to evaluate whether the presence of gasping at the time of Emergency Medical Service (EMS) arrival in the case OHCA patients of presumed cardian origin has any impact on six-month survival and/or sustained return of spontaneous circulation (ROSC).

METHODS

We collected and analyzed Utstein Style data for all patients resuscitated for OHCA of presumed cardiac origin by the EMS of the Central Bohemian Region from July 1^st, 2013 to June 30^th, 2014.

RESULTS

During the data collection period, 565 cases of OHCA of presumed cardiac origin were reported. Gasping at the time of EMS arrival was identified in 23.9%. The presence of gasping was associated with a significantly increased frequency of sustained ROSC (48.1 versus 20.7%, P<0.001) and six-month survival (40.7 versus 16.7%, P<0.001) than in non-breathing patients. Presence of gasping upon EMS arrival has been found to be an independent positive predictor of sustained ROSC (OR 2.51, CI 95% 1.59-3.98, P<0.001). The occurrence of gasping at the time of EMS arrival at the scene was significantly related to response time from EMS activation to arrival.

CONCLUSION

The presence of gasping upon arrival of the EMS for the patient with OHCA of presumed cardiac origin predicts both improves short-term and long-term prognoses.

Detection and quantification of gasping during resuscitation for out-of-hospital cardiac arrest

AIM

To detect and quantify gasping during cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest (OHCA) patients and to investigate whether gasping is associated with increased return of spontaneous circulation (ROSC).

MATERIALS AND METHODS

A prospective observational study in patients resuscitated and mechanically or manually ventilated for OHCA by emergency physicians of Ghent University Hospital. After intubation, pressure catheters were inserted in the endotracheal tube (ETT) and pressures were measured at the proximal and distal ends of the ETT. Gasping was analysed with custom-developed software and volumes were calculated based on pressure differences between the catheters. Data are expressed as median (interquartile range).

RESULTS

Data were collected in 292 resuscitated patients of whom 36.2% achieved ROSC. Seventy-six of 292 (26.0%) patients showed gasping on the pressure curves during resuscitation. The median gasping volume was 274ml (196-434). The median gasping rate was 3.7 gasps/min (1.5-7.3). Gasping occurred significantly more in patients displaying ventricular fibrillation as the initial rhythm compared to patients with pulseless electrical activity, pulseless ventricular tachycardia or asystole. The median gasping rate was significantly higher in the ROSC group compared to the non-ROSC group (11.8 gasps/min (95% CI [4.2, 13.9]) and 2.8 gasps/min (95% CI [1.7, 3.9]) respectively (P<0.001)). A gasping rate of >7.3 gasps/min appeared to be the optimal criterion value to herald ROSC. Deeper negative pressures were associated with an increased incidence of ROSC (P=0.011). There was no significant difference in ROSC between patients with gasping and those without.

CONCLUSION

The occurrence of gasping during CPR was high. Significant gasping volumes were measured. The presence or absence of gasping was not associated with ROSC, but higher gasping rate and deeper negative pressures were.

Circulatory Failure During Noninhaled Forms of Cyanide Intoxication

Our objective was to determine how circulatory failure develops following systemic administration of potassium cyanide (KCN). We used a noninhaled modality of intoxication, wherein the change in breathing pattern would not influence the diffusion of CN into the blood, akin to the effects of ingesting toxic levels of CN. In a group of 300 to 400 g rats, CN-induced coma (CN i.p., 7 mg/kg) produced a central apnea within 2 to 3 min along with a potent and prolonged gasping pattern leading to autoresuscitation in 38% of the animals. Motor deficits and neuronal necrosis were nevertheless observed in the surviving animals. To clarify the mechanisms leading to potential autoresuscitation versus asystole, 12 urethane-anesthetized rats were then exposed to the lowest possible levels of CN exposure that would lead to breathing depression within 7 to 8 min; this dose averaged 0.375 mg/kg/min i.v. At this level of intoxication, a cardiac depression developed several minutes only after the onset of the apnea, leading to cardiac asystole as PaO2 reached value approximately 15 Torr, unless breathing was maintained by mechanical ventilation or through spontaneous gasping. Higher levels of KCN exposure in 10 animals provoked a primary cardiac depression, which led to a rapid cardiac arrest by pulseless electrical activity (PEA) despite the maintenance of PaO2 by mechanical ventilation. These effects were totally unrelated to the potassium contained in KCN. It is concluded that circulatory failure can develop as a direct consequence of CN-induced apnea but in a narrow range of exposure. In this "low" range, maintaining pulmonary gas exchange after exposure, through mechanical ventilation (or spontaneous gasping), can reverse cardiac depression and restore spontaneous breathing. At higher level of intoxication, cardiac depression is to be treated as a specific and spontaneously irreversible consequence of CN exposure, leading to a PEA.

Microcirculatory blood flow during cardiac arrest and cardiopulmonary resuscitation does not correlate with global hemodynamics: an experimental study

Background

Current research highlights the role of microcirculatory disorders in post-cardiac arrest patients. Affected microcirculation shows not only dissociation from systemic hemodynamics but also strong connection to outcome of these patients. However, only few studies evaluated microcirculation directly during cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). The aim of our experimental study in a porcine model was to describe sublingual microcirculatory changes during CA and CPR using recent videomicroscopic technology and provide a comparison to parameters of global hemodynamics.

Methods

Cardiac arrest was induced in 18 female pigs (50 ± 3 kg). After 3 min without treatment, 5 min of mechanical CPR followed. Continuous hemodynamic monitoring including systemic blood pressure and carotid blood flow was performed and blood lactate was measured at the end of baseline and CPR. Sublingual microcirculation was assessed by the Sidestream Dark Field (SDF) technology during baseline, CA and CPR. Following microcirculatory parameters were assessed off-line separately for capillaries (≤20 µm) and other vessels: total and perfused vessel density (TVD, PVD), proportion of perfused vessels (PPV), microvascular flow index (MFI) and heterogeneity index (HI).

Results

In comparison to baseline the CA small vessel microcirculation was only partially preserved: TVD 15.64 (13.59–18.48) significantly decreased to 12.51 (10.57–13.98) mm/mm², PVD 15.57 (13.56–17.80) to 5.53 (4.17–6.60) mm/mm², PPV 99.64 (98.05–100.00) to 38.97 (27.60–46.29) %, MFI 3.00 (3.00–3.08) to 1.29 (1.08–1.58) and HI increased from 0.08 (0.00–0.23) to 1.5 (0.71–2.00), p = 0.0003 for TVD and <0.0001 for others, respectively. Microcirculation during ongoing CPR in small vessels reached 59–85 % of the baseline values: TVD 13.33 (12.11–15.11) mm/mm², PVD 9.34 (7.34–11.52) mm/mm², PPV 72.34 (54.31–87.87) %, MFI 2.04 (1.58–2.42), HI 0.65 (0.41–1.07). The correlation between microcirculation and global hemodynamic parameters as well as to lactate was only weak to moderate (i.e. Spearman’s ρ 0.02–0.51) and after adjustment for multiple correlations it was non-significant.

Conclusions

Sublingual microcirculatory parameters did not correlate with global hemodynamic parameters during simulated porcine model of CA and CPR. SDF imaging provides additional information about tissue perfusion in the course of CPR.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0934-5) contains supplementary material, which is available to authorized users.

The association of gasping and outcome, in out of hospital cardiac arrest: A systematic review and meta-analysis

OBJECTIVE

Gasping is common after cardiac arrest, and its frequency decreases over time. The aim of this study was to conduct a meta-analysis to evaluate the association of gasping and survival to discharge in patients who suffered out-of-hospital cardiac arrest.

METHODS

Relevant studies were identified by searching in PubMed, Medline, Embase, OVID, Web of Science and Google Scholar. Risk ratios (RR) and 95% confidence intervals (CI) were calculated to assess the association of gasping and on out-of-hospital cardiac arrest outcomes. Heterogeneity, subgroup analysis, sensitivity analysis and publication bias were explored.

RESULTS

Individual patient data was obtained from 10,797 participants suffered out-of-hospital cardiac arrest in five cohort studies of 4 articles. A fixed effects model suggested that patients with gasping were 3.525 times (95% CI: 3.028-4.104; P<0.01) more likely to survive to discharge than those without gasping, and there was no heterogeneity among studies (P=0.564). Also it may be a favorable factor for return of spontaneous circulation (RR: 2.170; 95% CI: 1.691, 2.785) with high heterogeneity (Q=5.26; P=0.022).

CONCLUSIONS

Findings of this meta-analysis demonstrated that gasping is common after cardiac arrest, and is associated with increased survival to discharge. Patients who are cardiac arrest with gasping should be promptly resuscitated.

[Broncho-pulmonary aspiration of brain and cartilage tissue in a context of gasping]

Evidence of post-mortem breath movements are rarely reported. We present two cases of broncho-pulmonary aspiration of brain and cartilage tissue following two fatal suicidal gunshots to the head. We also discuss the physiopathological implications for the agony.

Resuscitation and auto resuscitation by airway reflexes in animals

Various diseases often result in decompensation requiring resuscitation. In infants moderate hypoxia evokes a compensatory augmented breath - sigh and more severe hypoxia results in a solitary gasp. Progressive asphyxia provokes gasping respiration saving the healthy infant - autoresuscitation by gasping. A neonate with sudden infant death syndrome, however, usually will not survive. Our systematic research in animals indicated that airway reflexes have similar resuscitation potential as gasping respiration. Nasopharyngeal stimulation in cats and most mammals evokes the aspiration reflex, characterized by spasmodic inspiration followed by passive expiration. On the contrary, expiration reflex from the larynx, or cough reflex from the pharynx and lower airways manifest by a forced expiration, which in cough is preceded by deep inspiration. These reflexes of distinct character activate the brainstem rhythm generators for inspiration and expiration strongly, but differently. They secondarily modulate the control mechanisms of various vital functions of the organism. During severe asphyxia the progressive respiratory insufficiency may induce a life-threatening cardio-respiratory failure. The sniff- and gasp-like aspiration reflex and similar spasmodic inspirations, accompanied by strong sympatho-adrenergic activation, can interrupt a severe asphyxia and reverse the developing dangerous cardiovascular and vasomotor dysfunctions, threatening with imminent loss of consciousness and death. During progressive asphyxia the reversal of gradually developing bradycardia and excessive hypotension by airway reflexes starts with reflex tachycardia and vasoconstriction, resulting in prompt hypertensive reaction, followed by renewal of cortical activity and gradual normalization of breathing. A combination of the aspiration reflex supporting venous return and the expiration or cough reflex increasing the cerebral perfusion by strong expirations, provides a powerful resuscitation and autoresuscitation potential, proved in animal experiments. They represent a simple but unique model tested in animal experiments.

Hemodynamic and Metabolic Parameters During Prolonged Cardiac Arrest and Reperfusion by Extracorporeal Circulation

Extracorporeal membranous oxygenation (ECMO) is increasingly used in the management of refractory cardiac arrest. Our aim was to investigate early effects of ECMO after prolonged cardiac arrest. In fully anesthetized swine (48 kg, N=18) ventricular fibrillation (VF) was induced and untreated period (20 min) of cardiac arrest commenced, followed by 60 min extracorporeal reperfusion (ECMO flow 100 ml/kg.min). Hemodynamics, arterial blood gasses, plasma potassium, tissue oximetry (StO2) and cardiac (EGM) and cerebral (BIS) electrophysiological parameters were continuously recorded and analyzed. Within 3 minutes of VF hemodynamic and oximetry parameters fall abruptly while metabolic parameters destabilize gradually over 20 minutes peaking at pH 7.04±0.05, pCO2 89±14 mmHg, K+ 8.5±1.6 mmol/l. During reperfusion most parameters restore rapidly: within 3-5 minutes mean arterial pressure reaches >40 mmHg, StO2>50 %, paO2>100 mmHg, pCO2<50 mmHg, K+<5 mmol/l. EGMs mean amplitude peaks at 4.5±2.4 min. Cerebral activity (BIS>60) reappeared in 5 animals after 87±21 min. In 12/18 animals return of spontaneous circulation was achieved. In conclusions, ECMO provides rapid restitution of internal milieu even after prolonged arrest. However, despite normalization of global parameters full recovery was not guaranteed since cardiac and cerebral electrical activities were sufficiently restored only in some animals. More sensitive and organ specific indicators need to be identified in order to estimate adequacy of cardiac support devices.

Continued breathing followed by gasping or apnea in a swine model of ventricular fibrillation cardiac arrest

BACKGROUND

Continued breathing following ventricular fibrillation has here-to-fore not been described.

METHODS

We analyzed the spontaneous ventilatory activity during the first several minutes of ventricular fibrillation (VF) in our isoflurane anesthesized swine model of out-of-hospital cardiac arrest. The frequency and type of ventilatory activity was monitored by pneumotachometer and main stream infrared capnometer and analyzed in 61 swine during the first 3 to 6 minutes of untreated VF.

RESULTS

During the first minute of VF, the air flow pattern in all 61 swine was similar to those recorded during regular spontaneous breathing during anesthesia and was clearly different from the patterns of gasping. The average rate of continued breathing during the first minute of untreated VF was 10 breaths per minute. During the second minute of untreated VF, spontaneous breathing activity either stopped or became typical of gasping. During minutes 2 to 5 of untreated VF, most animals exhibited very slow spontaneous ventilatory activity with a pattern typical of gasping; and the pattern of gasping was crescendo-decrescendo, as has been previously reported. In the absence of therapy, all ventilatory activity stopped 6 minutes after VF cardiac arrest.

CONCLUSION

In our swine model of VF cardiac arrest, we documented that normal breathing continued for the first minute following cardiac arrest.

Breathing patterns during cardiac arrest

The absence of respiratory movements is a major criterion recommended for use by bystanders for recognizing an out-of-hospital cardiac arrest (CA), as the persistence of eupneic breathing is considered to be incompatible with CA. The basis for CA-related apnea is, however, uncertain, since brain stem Po2 is not expected to drop immediately to the critical level where anoxic apnea occurs. It is therefore essential on both clinical and physiological grounds to determine whether and when breathing stops after the onset of CA. In eight patients, we measured the ventilatory response at the onset of ventricular fibrillation (VF) for 12–15 s during the placement of an implantable cardioverter-defibrillator device. We found that regular eupneic breathing was maintained unchanged despite the cessation of systemic and pulmonary blood flow generated by the heart. We extended these findings in adult sheep and found that, as in humans, the normal ventilatory pattern persists unchanged for the first 15 s despite the drop in blood pressure, followed by a progressive increase in minute ventilation, which was sustained for up to 164 s. The ensuing apnea was disrupted by typical gasps occurring at a very slow frequency. These observations suggest a complete “decoupling” between the return of CO2 to the pulmonary circulation and continued effective respiratory activity, contrary to what we predicted. This delayed cessation of eupneic breathing during the absence of cardiac pump function is likely related to the time needed for brain stem anoxia to develop. These findings challenge the notions that 1) ventilation stops as pulmonary blood flow/cardiac output ceases and 2) the presence of eupneic breathing is a reliable sign of effective cardiac pumping activity.

Gasping in response to basic resuscitation efforts: observation in a Swine model of cardiac arrest

Objective. To analyze the effect of basic resuscitation efforts on gasping and of gasping on survival. Methods. This is secondary analysis of a previously reported study comparing continuous chest compressions (CCC CPR) versus chest compressions plus ventilation (30:2 CPR) on survival. 64 swine were randomized to 1 of these 2 basic CPR approaches after either short (3 or 4 minutes) or long (5 or 6 minutes) durations of untreated VF. At 12 minutes of VF, all received the same Guidelines 2005 Advanced Cardiac Life Support. Neurologically status was evaluated at 24 hours. A score of 1 is normal, 2 is abnormal, such as not eating or drinking normally, unsteady gait, or slight resistance to restraint, 3 severely abnormal, where the animal is recumbent and unable to stand, 4 is comatose, and 5 is dead. For this analysis a neurological outcome score of 1 or 2 was classified as “good”, and a score of 3, 4, or 5 was classified as “poor.” Results. Gasping was more likely to continue or if absent, to resume in the animals with short durations of untreated VF before basic resuscitation efforts. With long durations of untreated VF, the frequency of gasping and survival was better in swine receiving CCC CPR. In the absence of frequent gasping, intact survival was rare in the long duration of untreated VF group. Conclusions. Gasping is an important phenomenon during basic resuscitation efforts for VF arrest and in this model was more frequent with CCC-CPR.