Cerebrovascular reactivity in comatose patients resuscitated from a cardiac arrest

Associations of arterial carbon dioxide and arterial oxygen concentrations with hospital mortality after resuscitation from cardiac arrest

Introduction

Arterial concentrations of carbon dioxide (PaCO₂) and oxygen (PaO₂) during admission to the intensive care unit (ICU) may substantially affect organ perfusion and outcome after cardiac arrest. Our aim was to investigate the independent and synergistic effects of both parameters on hospital mortality.

Methods

This was a cohort study using data from mechanically ventilated cardiac arrest patients in the Dutch National Intensive Care Evaluation (NICE) registry between 2007 and 2012. PaCO₂ and PaO₂ levels from arterial blood gas analyses corresponding to the worst oxygenation in the first 24 h of ICU stay were retrieved for analyses. Logistic regression analyses were performed to assess the relationship between hospital mortality and both categorized groups and a spline-based transformation of the continuous values of PaCO₂ and PaO₂.

Results

In total, 5,258 cardiac arrest patients admitted to 82 ICUs in the Netherlands were included. In the first 24 h of ICU admission, hypocapnia was encountered in 22 %, and hypercapnia in 35 % of included cases. Hypoxia and hyperoxia were observed in 8 % and 3 % of the patients, respectively. Both PaCO₂ and PaO₂ had an independent U-shaped relationship with hospital mortality and after adjustment for confounders, hypocapnia and hypoxia were significant predictors of hospital mortality: OR 1.37 (95 % CI 1.17–1.61) and OR 1.34 (95 % CI 1.08–1.66). A synergistic effect of concurrent derangements of PaCO₂ and PaO₂ was not observed (P = 0.75).

Conclusions

The effects of aberrant arterial carbon dioxide and arterial oxygen concentrations were independently but not synergistically associated with hospital mortality after cardiac arrest.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1067-6) contains supplementary material, which is available to authorized users.

Are changes in cerebrovascular autoregulation following cardiac arrest associated with neurological outcome? Results of a pilot study

PURPOSE

To investigate the association between impaired cerebrovascular autoregulation (CVAR) and outcome in comatose survivors of cardiac arrest.

METHODS

The correlation in the time domain between cerebral tissue oxygenation (cStO2) using near infrared spectroscopy (NIRS) and mean arterial pressure was used to determine the tissue oxygenation index (TOx) as a reflection of normal (TOx<0) or impaired (TOx>0) CVAR. Daily measurements (>1h recording time) were performed in the first three days post cardiac arrest. Survival and neurological outcome was assessed at three months following cardiac arrest. A control group of healthy volunteers was also investigated.

RESULTS

23 patients and 28 volunteers were studied. All survivors (n=8) of cardiac arrest had a good neurological outcome. The TOx (median [interquartile range] for days 1-3) was higher (Mann Whitney test, p<0.001) in non-survivors (0.04 [-0.02 to -0.16]) compared to survivors (-0.11 [-0.19 to -0.02]) and healthy volunteers (-0.15 [-0.27 to -0.04]) on every day and for days 1-3 following cardiac arrest. The TOx was not significantly different between survivors and healthy volunteers. The cStO2 did not discriminate survivors (67 [62-72]%) from non-survivors (71 [65-75]%). Logistic regression analysis demonstrated TOx to be independently associated with survival at three months post cardiac arrest (odds ratio [95% confidence interval] 0.01 [0.01-0.50], p=0.04).

CONCLUSIONS

Early impairment of CVAR following cardiac arrest is independently associated with mortality at three months follow-up. Assessments of CVAR could add to the management and prognostication during post-resuscitation care and should be further investigated as a guide to optimise cerebral perfusion pressure.

Postcardiac Arrest Management

Cardiac arrest afflicts more than 300,000 persons annually in North America alone. Advances in systematic, regimented postresuscitation care have lowered mortality and improved neurologic outcomes in select cohorts of patients over the last decade. Postcardiac arrest care now comprises its own link in the chain of survival. For most patients, high-quality postcardiac arrest care begins in the Emergency Department. This article reviews the evidence and offers treatment strategies for the key components of postcardiac arrest care.

Effects of PaCO2 derangements on clinical outcomes after cerebral injury: A systematic review

OBJECTIVE

Partial pressure of arterial carbon dioxide (PaCO2) is a major regulator of cerebral blood flow (CBF). Derangements in PaCO2 have been thought to worsen clinical outcomes after many forms of cerebral injury by altering CBF. Our aim was to systematically analyze the biomedical literature to determine the effects of PaCO2 derangements on clinical outcomes after cerebral injury.

METHODS

We performed a search of Cochrane Library, PUBMED, CINHAL, conference proceedings, and other sources using a comprehensive strategy. Study inclusion criteria were (1) human subjects; (2) cerebral injury; (3) mechanical ventilation post-injury; (4) measurement of PaCO2; and (5) comparison of a clinical outcome measure (e.g. mortality) between different PaCO2 exposures. We performed a qualitative analysis to collate and summarize effects of PaCO2 derangements according to the recommended methodology from the Cochrane Handbook.

RESULTS

Seventeen studies involving different etiologies of cerebral injury (six traumatic brain injury, six post-cardiac arrest syndrome, two cerebral vascular accident, three neonatal ischemic encephalopathy) met all inclusion and no exclusion criteria. Three randomized control trials were identified and only one was considered a high quality study as per the Cochrane criteria for assessing risk of bias. In 13/17 (76%) studies examining hypocapnia, and 7/10 (70%) studies examining hypercapnia, the exposed group (hypercapnia or hypocapnia) was associated with poor clinical outcome.

CONCLUSION

The majority of studies in this report found exposure to hypocapnia and hypercapnia after cerebral injury to be associated with poor clinical outcome. However, the optimal PaCO2 range associated with good clinical outcome remains unclear.

From door to recovery: a collaborative approach to the development of a post-cardiac arrest center

Out-of-hospital cardiac arrest remains common and, despite advances in resuscitation practices, continues to carry a high mortality that may be influenced by several factors, including where a patient is cared for after the cardiac arrest. Implementing a post-cardiac arrest care guideline for survivors of out-of-hospital and in-hospital cardiac arrest involves a multidisciplinary approach with short-term and long-term strategies. Physician and nursing leaders must work in synergy to guide the implementation of an evidence-based plan of care. A collaborative approach was used at a hospital to develop processes, build consensus for protocols, and provide support to staff and teams. A joint approach has allowed the hospital to move from traditional silos of individual departmental care to a continuum of patient-focused management after cardiac arrest. This care coordination is initiated in the emergency department and follows the patient through to discharge.

Global and regional differences in cerebral blood flow after asphyxial versus ventricular fibrillation cardiac arrest in rats using ASL-MRI

Both ventricular fibrillation cardiac arrest (VFCA) and asphyxial cardiac arrest (ACA) are frequent causes of CA. However, only isolated reports compared cerebral blood flow (CBF) reperfusion patterns after different types of CA, and even fewer reports used methods that allow serial and regional assessment of CBF. We hypothesized that the reperfusion patterns of CBF will differ between individual types of experimental CA. In a prospective block-randomized study, fentanyl-anesthetized adult rats were subjected to 8min VFCA or ACA. Rats were then resuscitated with epinephrine, bicarbonate, manual chest compressions and mechanical ventilation. After the return of spontaneous circulation, CBF was then serially assessed via arterial spin-labeling magnetic resonance imaging (ASL-MRI) in cortex, thalamus, hippocampus and amygdala/piriform complex over 1h resuscitation time (RT). Both ACA and VFCA produced significant temporal and regional differences in CBF. All regions in both models showed significant changes over time (p<0.01), with early hyperperfusion and delayed hypoperfusion. ACA resulted in early hyperperfusion in cortex and thalamus (both p<0.05 vs. amygdala/piriform complex). In contrast, VFCA induced early hyperperfusion only in cortex (p<0.05 vs. other regions). Hyperperfusion was prolonged after ACA, peaking at 7min RT (RT7; 199% vs. BL, Baseline, in cortex and 201% in thalamus, p<0.05), then returning close to BL at ∼RT15. In contrast, VFCA model induced mild hyperemia, peaking at RT7 (141% vs. BL in cortex). Both ACA and VFCA showed delayed hypoperfusion (ACA, ∼30% below BL in hippocampus and amygdala/piriform complex, p<0.05; VFCA, 34-41% below BL in hippocampus and amygdala/piriform complex, p<0.05). In conclusion, both ACA and VFCA in adult rats produced significant regional and temporal differences in CBF. In ACA, hyperperfusion was most pronounced in cortex and thalamus. In VFCA, the changes were more modest, with hyperperfusion seen only in cortex. Both insults resulted in delayed hypoperfusion in all regions. Both early hyperperfusion and delayed hypoperfusion may be important therapeutic targets. This study was approved by the University of Pittsburgh IACUC 1008816-1.

Association between initial prescribed minute ventilation and post-resuscitation partial pressure of arterial carbon dioxide in patients with post-cardiac arrest syndrome

BACKGROUND

Post-cardiac arrest hypocapnia/hypercapnia have been associated with poor neurological outcome. However, the impact of arterial carbon dioxide (CO2) derangements during the immediate post-resuscitation period following cardiac arrest remains uncertain. We sought to test the correlation between prescribed minute ventilation and post-resuscitation partial pressure of CO2 (PaCO2), and to test the association between early PaCO2 and neurological outcome.

METHODS

We retrospectively analyzed a prospectively compiled single-center cardiac arrest registry. We included adult (age ≥ 18 years) patients who experienced a non-traumatic cardiac arrest and required mechanical ventilation. We analyzed initial post-resuscitation ventilator settings and initial arterial blood gas analysis (ABG) after initiation of post-resuscitation ventilator settings. We calculated prescribed minute ventilation:MVmL/kg/min=tidalvolumeTV/idealbodyweightIBWxrespiratoryrateRRfor each patient. We then used Pearson's correlation to test the correlations between prescribed MV and PaCO2. We also determined whether patients had normocapnia (PaCO2 between 30 and 50 mmHg) on initial ABG and tested the association between normocapnia and good neurological function (Cerebral Performance Category 1 or 2) at hospital discharge using logistic regression analyses.

RESULTS

Seventy-five patients were included. The majority of patients were in-hospital arrests (85%). Pulseless electrical activity/asystole was the initial rhythm in 75% of patients. The median (IQR) TV, RR, and MV were 7 (7 to 8) mL/kg, 14 (14 to 16) breaths/minute, and 106 (91 to 125) mL/kg/min, respectively. Hypocapnia, normocapnia, and hypercapnia were found in 15%, 62%, and 23% of patients, respectively. Good neurological function occurred in 32% of all patients, and 18%, 43%, and 12% of patients with hypocapnia, normocapnia, and hypercapnia respectively. We found prescribed MV had only a weak correlation with initial PaCO2, R = -0.40 (P < 0.001). Normocapnia was associated with good neurological function, odds ratio 4.44 (95% CI 1.33 to 14.85).

CONCLUSIONS

We found initial prescribed MV had only a weak correlation with subsequent PaCO2 and that early Normocapnia was associated with good neurological outcome. These data provide rationale for future research to determine the impact of PaCO2 management during mechanical ventilation in post-cardiac arrest patients.

Duplex sonography of cerebral blood flow after cardiac arrest--a prospective observational study

AIM

Despite successful resuscitation, cardiac arrest (CA) often has a poor clinical prognosis. Different diagnostic tools have been established to predict patients' outcome. However, their sensitivity remains low. Assessment of cerebral perfusion by duplex ultrasound might provide additional information regarding the extent of neuronal damage. The aim of the present study was to analyse the changes of global cerebral blood flow (CBF) and intracranial blood flow parameters in the acute stage after CA and its correlation with patients' outcome.

METHODS

We investigated 54 patients (17-85 years, mean age: 63±17 years) after CA with return of spontaneous circulation on an intensive care unit. All patients received therapeutic hypothermia (TH) for 24 h after CA and reanimation. Serial measurements of CBF as well as intracranial blood flow velocities and pulsatility indices of the middle cerebral artery and the basal vein of Rosenthal were performed within the first 10 days using duplex ultrasound. Clinical outcome was measured using the Cerebral Performance Category.

RESULTS

Measurements were successful in 53 patients. CBF values differed between 210 and 1100 ml/min. 24 patients (45%) attained a good outcome. No correlation between CBF or intracranial blood flow characteristics and outcome was found. Neither cerebral hypo- nor hyperperfusion was associated with a fatal outcome.

CONCLUSION

Cerebral perfusion varies widely after CA. Neither hypo- nor hyperperfusion seems to be an independent risk factor for poor outcome. Duplex ultrasound of cerebral haemodynamics after CA is suitable but probably of limited prognostic value.

Early oxygenation and ventilation measurements after pediatric cardiac arrest: lack of association with outcome

OBJECTIVES

To explore oxygenation and ventilation status early after cardiac arrest in infants and children. We hypothesize that hyperoxia is common and associated with worse outcome after pediatric cardiac arrest.

DESIGN

Retrospective cohort study.

SETTING

Fifteen hospitals within the Pediatric Emergency Care Applied Research Network.

PATIENTS

Children who suffered a cardiac arrest event and survived for at least 6 hours after return of circulation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Analysis of 195 events revealed that abnormalities in oxygenation and ventilation are common during the initial 6 hours after pediatric cardiac arrest. Hyperoxia was frequent, affecting 54% of patients. Normoxia was documented in 34% and hypoxia in 22% of patients. These percentages account for a 10% overlap of patients who had both hyperoxia and hypoxia. Ventilation status was more evenly distributed with hyperventilation observed in 38%, normoventilation in 29%, and hypoventilation in 46%, with a 13% overlap of patients who had both hyperventilation and hypoventilation. Derangements in both oxygenation and ventilation were common early after cardiac arrest such that both normoxia and normocarbia were documented in only 25 patients (13%). Neither oxygenation nor ventilation status was associated with outcome. After controlling for potential confounders, arrest location and rhythm were significantly associated with worse outcome; however, hyperoxia was not (odds ratio for good outcome, 1.02 [0.46, 2.84]; p = 0.96).

CONCLUSIONS

Despite recent resuscitation guidelines that advocate maintenance of normoxia and normoventilation after pediatric cardiac arrest, this is uncommonly achieved in practice. Although we did not demonstrate an association between hyperoxia and worse outcome, the small proportion of patients kept within normal ranges limited our power. Preclinical data suggesting potential harm with hyperoxia remain compelling, and further investigation, including prospective, large studies involving robust recording of physiological derangements, is necessary to further advance our understanding of this important topic.

[Post-resuscitation syndrome. Role of inflammation after cardiac arrest]

Cardiac arrest with subsequent cardiopulmonary resuscitation causes an ischemic reperfusion syndrome of the whole body resulting in localized damage of particularly sensitive organs, such as the brain and heart, together with systemic sequelae. The main factor is a generalized activation of inflammatory reactions resulting in symptoms similar in many aspects to those of sepsis. Systemic inflammation strengthens organ damage due to disorders in the macrocirculation and microcirculation due to metabolic imbalance as well as the effects of direct leukocyte transmitted tissue destruction. The current article gives an overview on the role of inflammation following cardiac arrest and presents in detail the underlying mechanisms, the clinical symptoms and possible therapeutic approaches.

RECOVER evidence and knowledge gap analysis on veterinary CPR. Part 7: Clinical guidelines

OBJECTIVE

To present a series of evidence-based, consensus guidelines for veterinary CPR in dogs and cats.

DESIGN

Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence and quality, and development of consensus on conclusions for application of the concepts to clinical practice. Questions in five domains were examined: Preparedness and Prevention, Basic Life Support, Advanced Life Support, Monitoring, and Post-Cardiac Arrest Care. Standardized worksheet templates were used for each question, and the results reviewed by the domain members, by the RECOVER committee, and opened for comments by veterinary professionals for 4 weeks. Clinical guidelines were devised from these findings and again reviewed and commented on by the different entities within RECOVER as well as by veterinary professionals.

SETTING

Academia, referral practice and general practice.

RESULTS

A total of 74 worksheets were prepared to evaluate questions across the five domains. A series of 101 individual clinical guidelines were generated. In addition, a CPR algorithm, resuscitation drug-dosing scheme, and postcardiac arrest care algorithm were developed.

CONCLUSIONS

Although many knowledge gaps were identified, specific clinical guidelines for small animal veterinary CPR were generated from this evidence-based process. Future work is needed to objectively evaluate the effects of these new clinical guidelines on CPR outcome, and to address the knowledge gaps identified through this process.

Improving outcomes from out-of-hospital cardiac arrest in young children and adolescents

Out-of-hospital cardiac arrest (OHCA) is an unusual but devastating occurrence in a young person. Years of life-lost are substantial and long-term health care costs of survivors can be high. However, there have been noteworthy improvements in cardiopulmonary resuscitation (CPR) standards, out-of hospital care, and postcardiac arrest therapies that have resulted in a several-fold improvement in resuscitation outcomes. Recent interest and research in resuscitation of children has the promise of generating improvements in the outcomes of these patients. Integrated and coordinated care in the out-of-hospital and hospital settings are required. This article will review the epidemiology of OHCA, the 2010 CPR guidelines, and developments in public access defibrillation for children.

Therapeutic hypothermia after cardiac arrest - cerebral perfusion and metabolism during upper and lower threshold normocapnia

BACKGROUND

During cardiac arrest and after successful resuscitation a continuum of ischaemia-reperfusion injury develops. Mild hypothermia exerts protective effects in the postresuscitation phase but also alters CO₂ production and solubility, which may lead to deleterious effects if overlooked when adjusting the ventilation of the resuscitated patient. Using a multimodality approach, the effects of different carbaemic states on cerebral perfusion and metabolism were evaluated during therapeutic hypothermia.

METHODS

Eight comatose survivors of prehospital cardiac arrest were cooled to 33°C for 24 h and underwent a 60 min phase of interventional lower threshold normocapnia according to temperature non-corrected pCO₂ (4.2 kPa) and higher threshold normocapnia according to corrected pCO₂ (6.0 kPa) in a random order. Prior to, during and after each phase, cerebral perfusion and metabolites via a microdialysis catheter were measured.

RESULTS

During upper-threshold pCO₂, an increase in middle cerebral artery mean flow velocity (MFV) and jugular bulb oxygen saturation (jSvO₂) were observed with a concomitant decrease in cerebral lactate concentration. Lower threshold normocapnia was associated with a decrease in MFV in most patients. In all patients jSvO₂ decreased but no change in cerebral lactate was observed. In seven patients jSvO₂ decreased below 55%. These changes were not reflected to intracranial pressure or cerebral oximetry.

CONCLUSIONS

During induced hypothermia, lower threshold normocapnia was associated with decreased cerebral perfusion/oxygenation but not reflected to interstitial metabolites. Upper threshold pCO₂ increased cerebral perfusion and reduced cerebral lactate. Vigilance over the ventilatory and CO₂ analysis regimen is mandatory during mild hypothermia.

Bench-to-bedside review: carbon dioxide

Carbon dioxide is a waste product of aerobic cellular respiration in all aerobic life forms. PaCO2 represents the balance between the carbon dioxide produced and that eliminated. Hypocapnia remains a common - and generally underappreciated - component of many disease states, including early asthma, high-altitude pulmonary edema, and acute lung injury. Induction of hypocapnia remains a common, if controversial, practice in both adults and children with acute brain injury. In contrast, hypercapnia has traditionally been avoided in order to keep parameters normal. More recently, advances in our understanding of the role of excessive tidal volume has prompted clinicians to use ventilation strategies that result in hypercapnia. Consequently, hypercapnia has become increasingly prevalent in the critically ill patient. Hypercapnia may play a beneficial role in the pathogenesis of inflammation and tissue injury, but may hinder the host response to sepsis and reduce repair. In contrast, hypocapnia may be a pathogenic entity in the setting of critical illness. The present paper reviews the current clinical status of low and high PaCO2 in the critically ill patient, discusses the insights gained to date from studies of carbon dioxide, identifies key concerns regarding hypocapnia and hypercapnia, and considers the potential clinical implications for the management of patients with acute lung injury.

[Transcranial Doppler ultrasonography usefulness in cardiac arrest resuscitation]

An effective tissue perfusion has decisive influence on the final prognosis both during cardiopulmonary resuscitation (CPR) and after recovery of spontaneous circulation (ROSC). The transcranial Doppler ultranosography (TCD) examines the velocity and pulsatility of cerebral blood flow, making it possible to perform "beat to beat" hemodynamic analysis. During CPR, TCD peak systolic velocity reflects cerebral perfusion of the chest compressions. Beyond 2 hours after ROSC, persistence in the cerebral arteries of a hemodynamic TCD pattern (low velocities with high pulsatilities) predicts poor neurological prognosis. Early or delayed presence of a hyperemic TCD pattern (high velocities with low pulsatilities) is associated conclusively with evolution to intracranial hypertension and its appearance during the rewarming process should lead to immediate return to therapeutic hypothermia. The coincidence of hypodynamic cerebral arteries and others with normal or hyperemic TCD patterns may indicate the presence of focal hypoperfusion that could predict stroke after ROSC.

[Managing the post-cardiac arrest syndrome. Directing Committee of the National Cardiopulmonary Resuscitation Plan (PNRCP) of the Spanish Society for Intensive Medicine, Critical Care and Coronary Units (SEMICYUC)]

Since the advent of cardiopulmonary resuscitation more than 40 years ago, we have achieved a return to spontaneous circulation in a growing proportion of patients with cardiac arrest. Nevertheless, most of these patients die in the first few days after admission to the intensive care unit (ICU), and this situation has not improved over the years. Mortality in these patients is mainly associated to brain damage. Perhaps recognizing that cardiopulmonary resuscitation does not end with the return of spontaneous circulation but rather with the return of normal brain function and total stabilization of the patient would help improve the therapeutic management of these patients in the ICU. In this sense, the term cardiocerebral resuscitation proposed by some authors might be more appropriate. The International Liaison Committee on Resuscitation recently published a consensus document on the "Post-Cardiac Arrest Syndrome" and diverse authors have proposed that post-arrest care be integrated as the fifth link in the survival chain, after early warning, early cardiopulmonary resuscitation by witnesses, early defibrillation, and early advanced life support. The therapeutic management of patients that recover spontaneous circulation after cardiopulmonary resuscitation maneuvers based on life support measures and a series of improvised actions based on "clinical judgment" might not be the best way to treat patients with post-cardiac arrest syndrome. Recent studies indicate that using goal-guided protocols to manage these patients including therapeutic measures of proven efficacy, such as inducing mild therapeutic hypothermia and early revascularization, when indicated, can improve the prognosis considerably in these patients. Given that there is no current protocol based on universally accepted evidence, the Steering Committee of the National Cardiopulmonary Resuscitation Plan of the Spanish Society of Intensive Medicine and Cardiac Units has elaborated this document after a thorough review of the literature and an online discussion involving all the members of the committee and a consensus meeting with the aim of providing a platform for the development of local protocols in different ICSs in our country to fit their own means and characteristics.

Post-cardiac arrest syndrome: Epidemiology, pathophysiology, treatment, and prognostication: A scientific statement from the International Liaison Committee on Resuscitation; the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; the Council on Stroke (Part 1)

AIM OF THE REVIEW

To review the epidemiology, pathophysiology, treatment and prognostication in relation to the post-cardiac arrest syndrome.

METHODS

Relevant articles were identified using PubMed, EMBASE and an American Heart Association EndNote master resuscitation reference library, supplemented by hand searches of key papers. Writing groups comprising international experts were assigned to each section. Drafts of the document were circulated to all authors for comment and amendment.

RESULTS

The 4 key components of post-cardiac arrest syndrome were identified as (1) post-cardiac arrest brain injury, (2) post-cardiac arrest myocardial dysfunction, (3) systemic ischaemia/reperfusion response, and (4) persistent precipitating pathology.

CONCLUSIONS

A growing body of knowledge suggests that the individual components of the postcardiac arrest syndrome are potentially treatable.

Incidence of iatrogenic dyscarbia during mild therapeutic hypothermia after successful resuscitation from out-of-hospital cardiac arrest

To investigate the incidence of iatrogenic dyscarbia in survivors of out-of-hospital cardiac arrest treated with induced mild hypothermia.We performed a retrospective cohort study of the ventilatory management based on blood gas analyses of patients resuscitated from prehospital cardiac arrest. In the pilot phase, we assessed the ventilatory management in the patients treated in one university hospital during a 4-year study period. Subsequently, a more recent (1-year) retrospective cohort of resuscitated patients from all five Finnish university hospitals concerning the first 48h after hospital admission was analyzed. Core temperatures and temperature corrected (or non-corrected) blood gas analysis results with focus on carbon dioxide tension were analyzed. In addition, a survey was performed to investigate the ventilatory strategies in all Finnish hospitals providing mild hypothermia for cardiac arrest victims.The pilot cohort suggested a high incidence of hypo- or hyper-carbia during hypothermia treatment. In the multicenter patient population of 122 patients contributing a total of 1627 measurements, the PaCO(2) distribution was as follows: less than 4 kPa in 148 samples out of 1627 (9%), 4-4.6 kPa in 404 (25%), 4.7-6 kPa in 887 (55%) and more than 6 kPa in 188 samples (12%). There was a significant difference in the incidence of hypercarbia between the hospitals (p<0.05).We conclude that normocarbia was achieved/maintained only in approximately 55% of the samples. The incidence of hypo- or hyper-carbia (dyscarbia) was high (45%). This may predispose for serious derangements in the cerebral perfusion of the resuscitated patient. These results call for vigilance in adjustment of the ventilatory management to meet the needs of the patients treated with mild hypothermia.

Scandinavian clinical practice guidelines for therapeutic hypothermia and post-resuscitation care after cardiac arrest

BACKGROUND AND AIM

Sudden cardiac arrest survivors suffer from ischaemic brain injury that may lead to poor neurological outcome and death. The reperfusion injury that occurs is associated with damaging biochemical reactions, which are suppressed by mild therapeutic hypothermia (MTH). In several studies MTH has been proven to be safe, with few complications and improved survival, and is recommended by the International Liaison of Committee on Resuscitation. The aim of this paper is to recommend clinical practice guidelines for MTH treatment after cardiac arrest from the Scandinavian Society of Anaesthesiology and Intensive Care Medicine (SSAI).

METHODS

Relevant studies were identified after two consensus meetings of the SSAI Task Force on Therapeutic Hypothermia (SSAITFTH) and via literature search of the Cochrane Central Register of Controlled Trials and Medline. Evidence was assessed and consensus opinion was used when high-grade evidence (Grade of Recommendation, GOR) was unavailable. A management strategy was developed as a consensus from the evidence and the protocols in the participating countries.

RESULTS AND CONCLUSION

Although proven beneficial only for patients with initial ventricular fibrillation (GOR A), the SSAITFTH also recommend MTH after restored spontaneous circulation, if active treatment is chosen, in patients with initial pulseless electrical activity and asystole (GOR D). Normal ethical considerations, premorbid status, total anoxia time and general condition should decide whether active treatment is required or not. MTH should be part of a standardized treatment protocol, and initiated as early as possible after indication and treatment have been decided (GOR E). There is insufficient evidence to make definitive recommendations among techniques to induce MTH, and we do not know the optimal target temperature, duration of cooling and rewarming time. New studies are needed to address the question as to how MTH affects, for example, prognostic factors.

Statins for post resuscitation syndrome

After sudden cardiac arrest, successful resuscitation and return of spontaneous circulation, a multi-faceted ischaemia/reperfusion related disorder develops. This condition now known as post resuscitation syndrome is characterised by marked increases in the inflammatory response and changes in coagulation profile and vascular reactivity. Additionally, the production of reactive oxygen species and activation of cytotoxic cascades of metabolism add to these injury mechanisms resulting in multiorgan perfusion deficits and dysfunction. Especially in the cerebrum these injuries may be the cause of significant morbidity and mortality. Recent evidence has shown that statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) exert numerous beneficial effects in cardiovascular diseases irrespective of the lipid status. Remarkably, these pleiotropic effects seem to extended beyond cardiovascular diseases such as immunomodulative and antioxidative properties. We hypothesised that administration of statins early in the post resuscitation phase would prove beneficial in the resuscitated patient via several pleiotropic effects. These include inhibition of excessive coagulation and inflammatory response, suppression of oxygen radical production and improved vascular reactivity. The discussed effects are mediated via multiple pathways activated in the cardiac arrest victim, to which statins have been shown to have a beneficial modulating effect in experimental settings and non-cardiac arrest patients. To test this hypothesis in clinical practice, a randomized, controlled trial with sufficient power and standardised post resuscitation treatment would be necessary. The generally good tolerance of statin therapy with minimal adverse effects would support this experiment, although a parenteral form of the drug to ensure adequate dosage might be a prerequisite.

The effect of pneumoperitoneum and Trendelenburg position on acute cerebral blood flow-carbon dioxide reactivity under sevoflurane anaesthesia

This study compared cerebral blood flow-carbon dioxide (CBF-CO2) reactivities in the supine and modest Trendelenburg position under pnemoperitoneum during sevoflurane anaesthesia. After induction of anaesthesia in 25 patients, mechanical ventilation was adjusted to increase Paco2 from 4.7 (T1) to 6.0 kPa (T2) in the supine position, and the change in jugular bulb oxygen saturation was measured as an index of CBF. Then, after establishment of pneumoperitoneum and 30 degrees Trendelenburg position, the CO(2) step and measurement of CBF were repeated. The CBF-CO2 reactivity was 7.5 (3.3) %xkPa(-1) (% change in jugular bulb oxygen saturation per unit change in Paco2) in the supine position and 6.8 (2.3) %xkPa(-1) in the 30 degrees Trendelenburg-pneumoperitoneum condition (p = 0.086). We conclude that CBF-CO2 reactivity is unchanged by the modest Trendelenburg position under pneumoperitoneum during sevoflurane anaesthesia.

Post-cardiac arrest syndrome: epidemiology, pathophysiology, treatment, and prognostication. A Scientific Statement from the International Liaison Committee on Resuscitation; the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; the Council on Stroke

AIM OF THE REVIEW

To review the epidemiology, pathophysiology, treatment and prognostication in relation to the post-cardiac arrest syndrome.

METHODS

Relevant articles were identified using PubMed, EMBASE and an American Heart Association EndNote master resuscitation reference library, supplemented by hand searches of key papers. Writing groups comprising international experts were assigned to each section. Drafts of the document were circulated to all authors for comment and amendment.

RESULTS

The 4 key components of post-cardiac arrest syndrome were identified as (1) post-cardiac arrest brain injury, (2) post-cardiac arrest myocardial dysfunction, (3) systemic ischaemia/reperfusion response, and (4) persistent precipitating pathology.

CONCLUSIONS

A growing body of knowledge suggests that the individual components of the post-cardiac arrest syndrome are potentially treatable.

Postresuscitation care

Cardiac arrest in infants and children is a rare but critical event that typically follows a period of respiratory or circulatory compromise and has a low survival rate. The only intervention demonstrated to increase survival rate is the provision of bystander CPR. This article examines the pathophysiology of the postarrest reperfusion state; postresuscitation care of the respiratory and cardiovascular systems; postresuscitation neurologic management; therapeutic hypothermia; blood glucose control; immunologic disturbances and infections; coagulation abnormalities; and gastrointestinal and hepatic dysfunction, among other topics.

Changes in cerebral blood flow and oxygen extraction during post-resuscitation syndrome

INTRODUCTION

Most survivors of out-of-hospital cardiac arrest (OHCA) will die subsequently from post-anoxic encephalopathy. In animals, the severity of brain damage is mainly influenced by the duration of cardiac arrest and also by the cerebral blood flow (CBF) and oxygen extraction (CEO2) abnormalities observed during the post-resuscitation period. The aim of our study was to describe CBF and CEO2 modifications during the first 72 h in OHCA patients treated by induced mild hypothermia.

METHODS

Consecutive OHCA patients were studied every 12 h over 72 h. Diastolic flow velocities (dFV), mean flow velocities (mFV) and pulsatility index (PI) were assessed by transcranial doppler (TCD) as an estimate of CBF changes. Simultaneous measurements of CEO2 were obtained using retrograde jugular catheterisation.

RESULTS

Eighteen patients (61 [47-74] years) were studied (12 non-survivors and 6 survivors). At admission, mFV values were low (27.3 [21.5-33.6]cm/s) but reached normal values after 72 h (50.5 [36.7-58.1]cm/s). Initial PI values were high (1.6 [1.3-1.9]) but reached normal values after 72 h (1.04 [0.82-1.2]). No differences were found between survivors and non-survivors regarding these CBF estimates. CEO2 values were quite normal at admission (20.4 [11-27%]) but decreased over time in non-survivors until H72 (25.8% [19.3-31.1] versus 5.7% [5.1-11.5], p=0.02).

CONCLUSION

Cerebral haemodynamic and oxygenation values are altered considerably but evolve during the first 72 h following resuscitation after cardiac arrest. In particular, these changes may lead to a mismatch between CBF and CEO2 leading to a "luxurous perfusion" in non-survivors.

Implementation of a standardised treatment protocol for post resuscitation care after out-of-hospital cardiac arrest

BACKGROUND

Mortality among patients admitted to hospital after out-of-hospital cardiac arrest (OHCA) is high. Based on recent scientific evidence with a main goal of improving survival, we introduced and implemented a standardised post resuscitation protocol focusing on vital organ function including therapeutic hypothermia, percutaneous coronary intervention (PCI), control of haemodynamics, blood glucose, ventilation and seizures.

METHODS

All patients with OHCA of cardiac aetiology admitted to the ICU from September 2003 to May 2005 (intervention period) were included in a prospective, observational study and compared to controls from February 1996 to February 1998.

RESULTS

In the control period 15/58 (26%) survived to hospital discharge with a favourable neurological outcome versus 34 of 61 (56%) in the intervention period (OR 3.61, CI 1.66-7.84, p=0.001). All survivors with a favourable neurological outcome in both groups were still alive 1 year after discharge. Two patients from the control period were revascularised with thrombolytics versus 30 (49%) receiving PCI treatment in the intervention period (47 patients (77%) underwent cardiac angiography). Therapeutic hypothermia was not used in the control period, but 40 of 52 (77%) comatose patients received this treatment in the intervention period.

CONCLUSIONS

Discharge rate from hospital, neurological outcome and 1-year survival improved after standardisation of post resuscitation care. Based on a multivariate logistic analysis, hospital treatment in the intervention period was the most important independent predictor of survival.

The prognostic value of early transcranial Doppler ultrasound following cardiopulmonary resuscitation

The aim of the presented study was to estimate the prognostic value of transcranial Doppler sonography (TCD) for the prediction of clinical outcome of patients after cardiopulmonary resuscitation (CPR) on the basis of the measured flow velocity changes in the basal cerebral arteries. Thirty-nine patients (27 men, 12 women) aged 66 +/- 15 y (+/-SD) who had undergone CPR were involved. Serial TCD examinations of the intracranial arteries were performed 1.5, 4, 8, 16, 24 and 72 h after CPR. Plasma neuron specific enolase (NSE), ventilation parameters (pH, paO(2), paCO(2)) and hemodynamic parameters were registered. Seventeen patients (group 1) survived with moderate or without neurologic deficits. Twenty-two patients (group 2) either died (n = 21) within 9 +/- 14 days or remained in vegetative state (n = 1). NSE levels ranged from 9 to 29 microg/L in group 1 and from 22 to 1242 microg/L in group 2 (p < 0.05). Four and 72 h after CPR, peak systolic flow velocities in the middle cerebral artery (MCA) were significantly higher in group 1 than in group 2 (p < 0.05). Twenty-four h after CPR, peak systolic and diastolic flow velocities in the ACA and PCA were also significantly higher in group 1 than in group 2 (p < 0.05). At this time, patients of group 2 showed significantly higher resistance index-values (RI = (sys-dia)/sys) in the anterior cerebral artery (ACA) and the posterior cerebral artery (PCA) (p < 0.05). A high correlation between peak systolic blood flow velocity in the MCA and systemic systolic blood pressure was observed in group 2 early 4 to 16 h after CPR (r = +0.52 to + 0.81, p < 0.05), while there was no such correlation in group 1. Using serial TCD examinations, patients with severely disabling or fatal outcome could be identified within the first 24 h. Besides established clinical and laboratory parameters, postanoxic myoclonus and NSE, serial TCD examinations following CPR may be helpful to predict the clinical outcome, but further studies with a larger number of patients are necessary to approve this hypothesis.