Pharmacokinetic and Other Considerations for Drug Therapy During Targeted Temperature Management:

Sedation and shivering management after cardiac arrest

Management of sedation and shivering during targeted temperature management (TTM) after cardiac arrest is limited by a dearth of high-quality evidence to guide clinicians. Data from general intensive care unit (ICU) populations can likely be extrapolated to post-cardiac arrest patients, but clinicians should be mindful of key differences that exist between these populations. Most importantly, the goals of sedation after cardiac arrest are distinct from other ICU patients and may also involve suppression of shivering during TTM. Drug metabolism and clearance are altered considerably during TTM when a low goal temperature is used, which can delay accurate neuroprognostication. When neuromuscular blockade is used to prevent shivering, sedation should be deep enough to prevent awareness and providers should be aware that this can mask clinical manifestations of seizures. However, excessively deep or prolonged sedation is associated with complications including delirium, infections, increased duration of ventilatory support, prolonged ICU length of stay, and delays in neuroprognostication. In this manuscript, we review sedation and shivering management best practices in the post-cardiac arrest patient population.

Temperature Control After Cardiac Arrest: A Narrative Review

Cardiac arrest (CA) is a critical public health issue affecting more than half a million Americans annually. The main determinant of outcome post-CA is hypoxic-ischemic brain injury (HIBI), and temperature control is currently the only evidence-based, guideline-recommended intervention targeting secondary brain injury. Temperature control is a key component of a post-CA care bundle; however, conflicting evidence challenges its wide implementation across the vastly heterogeneous population of CA survivors. Here, we critically appraise the available literature on temperature control in HIBI, detail how the evidence has been integrated into clinical practice, and highlight the complications associated with its use and the timing of neuroprognostication after CA. Future clinical trials evaluating different temperature targets, rates of rewarming, duration of cooling, and identifying which patient phenotype benefits from different temperature control methods are needed to address these prevailing knowledge gaps.

Electrolyte considerations in targeted temperature management

PURPOSE

Targeted temperature management (TTM), including normothermia and therapeutic hypothermia, is used primarily for comatose patients with return of spontaneous circulation after cardiac arrest or following neurological injury. Despite the potential benefits of TTM, risks associated with physiological alterations, including electrolyte shifts, may require intervention.

SUMMARY

This review describes the normal physiological balance of electrolytes and temperature-related alterations as well as the impact of derangements on patient outcomes, providing general recommendations for repletion and monitoring of key electrolytes, including potassium, phosphate, and magnesium.

CONCLUSION

Frequent monitoring and consideration of patient variables such as renal function and other risk factors for adverse effects are important areas of awareness for clinicians caring for patients undergoing TTM.

Targeted Temperature Management After Out-of-Hospital Cardiac Arrest: Integrating Evidence Into Real World Practice

Targeted temperature management (TTM) after out-of-hospital cardiac arrest (OHCA) has been a focus of debate in an attempt to improve post-arrest outcomes. Contemporary trials examining the role of TTM after cardiac arrest suggest that targeting normothermia should be the standard of care for initially comatose survivors of cardiac arrest. Differences in patient populations have been demonstrated across trials, and important subgroups may be under-represented in clinical trials compared with real-world registries. In this review, we aimed to describe the populations represented in international OHCA registries and to propose a pathway to integrate clinical trial evidence into practice. The patient case mix among registries including survivors to hospital admission was similar to the pivotal trials (shockable rhythm, witnessed arrest), suggesting reasonable external validity. Therefore, for the majority of OHCA, targeted normothermia should be the strategy of choice. There remains conflicting evidence for patients with a nonshockable rhythm, with no clear evidence-based justification for mild hypothermia over targeted normothermia.

Evaluation of Unfractionated Heparin Dosing by Antifactor Xa During Targeted Temperature Management Post Cardiac Arrest

Purpose

To evaluate unfractionated heparin (UFH) dosing guided by antifactor Xa levels during targeted temperature management (TTM) post-cardiac arrest.

Methods

Single-center, retrospective, observational study between January 1, 2014 and September 1, 2020. Patients initiated on TTM post-cardiac arrest and UFH were evaluated for inclusion. Patients included were ≥18 years of age and received weight-based UFH for ≥6 hours with 2 antifactor Xa levels drawn at target temperature. Excluded patients had no available temperature readings, received extracorporeal membrane oxygenation (ECMO) or factor Xa inhibitor (within 72 hours), or had hypertriglyceridemia or hyperbilirubinemia. The primary endpoint was to evaluate the proportion of patients that achieved a therapeutic antifactor Xa level between 0.3 and 0.7 IU/mL at steady state during TTM. Secondary endpoints included average UFH dose and average time to therapeutic antifactor Xa level at steady state; percent of first and total antifactor Xa levels subtherapeutic, therapeutic, and supratherapeutic during TTM.

Results

A total of 73 patients met inclusion criteria. Of these, 21 patients achieved steady-state therapeutic antifactor Xa levels during TTM. The average time and dose to steady-state therapeutic antifactor Xa levels were 8.1 ± 4.5 hours and 9.9 ± 3.2 units/kg/hour. Overall, 61.7% of first and 47.4% of all antifactor Xa levels were supratherapeutic during TTM. Three (4.1%) patients experienced a major bleeding event.

Conclusions

Guideline recommended UFH dosing, 12 or 18 units/kg/hour, during TTM resulted in more supratherapeutic antifactor Xa levels. Reduction of UFH infusion dose to 10 units/kg/hour may be required during TTM to maintain therapeutic antifactor Xa levels.

Targeted temperature management after out of hospital cardiac arrest: quo vadis?

Targeted temperature management (TTM) has become a cornerstone in the treatment of comatose post-cardiac arrest patients over the last two decades. Belief in the efficacy of this intervention for improving neurologically intact survival was based on two trials from 2002, one truly randomized-controlled and one small quasi-randomized trial, without clear confirmation of that finding. Subsequent large randomized trials reported no difference in outcomes between TTM at 33 vs. 36°C and no benefit of TTM at 33°C as compared with fever control alone. Given that these results may help shape post-cardiac arrest patient care, we sought to review the history and rationale as well as trial evidence for TTM, critically review the TTM2 trial, and highlight gaps in knowledge and research needs for the future. Finally, we provide contemporary guidance for the use of TTM in daily clinical practice.

Contemporary targeted temperature management: Clinical evidence and controversies

Advancements in cardiac arrest and post-cardiac arrest care have led to improved survival to hospital discharge. While survival to hospital discharge is an important clinical outcome, neurologic recovery is also a priority. With the advancement of targeted temperature management (TTM), the American Heart Association guidelines for post-cardiac arrest care recommend TTM in patients who remain comatose after return of spontaneous circulation (ROSC). Recently, the TTM2 randomized controlled trial found no significant difference in neurologic function and mortality at 6-months between traditional hypothermia to 33°C versus 37.5°C. While TTM has been evaluated for decades, current literature suggests that the use of TTM to 33° when compared to a protocol of targeted normothermia does not result in improved outcomes. Instead, perhaps active avoidance of fever may be most beneficial. Extracorporeal cardiopulmonary resuscitation and membrane oxygenation can provide a means of both hemodynamic support and TTM after ROSC. This review aims to describe the pathophysiology, physiologic aspects, clinical trial evidence, changes in post-cardiac arrest care, potential risks, as well as controversies of TTM.

Effects of Propofol on Hemodynamic Profile in Adults Receiving Targeted Temperature Management

Background: Propofol is a key component for the management of sedation and shivering during targeted temperature management (TTM) following cardiac arrest. The cardiac depressant effects of propofol have not been described during TTM and may be especially relevant given the stress to the myocardium following cardiac arrest. The purpose of this study is to describe hemodynamic changes associated with propofol administration during TTM. Methods: This single center, retrospective cohort study evaluated adult patients who received a propofol infusion for at least 30 minutes during TTM. The primary outcome was the change in cardiovascular Sequential Organ Failure Assessment (cvSOFA) score 30 minutes after propofol initiation. Secondary outcomes included change in systolic blood pressure (SBP), mean arterial pressure (MAP), heart rate (HR), and vasopressor requirements (VR) expressed as norepinephrine equivalents at 30, 60, 120, 180, and 240 minutes after propofol initiation. A multivariate regression was performed to assess the influence of propofol and body temperature on MAP, while controlling for vasopressor dose and cardiac arrest hospital prognosis (CAHP) score. Results: The cohort included 40 patients with a median CAHP score of 197. The goal temperature of 33°C was achieved for all patients. The median cvSOFA score was 1 at baseline and 0.5 at 30 minutes, with a non-significant change after propofol initiation ( P = .96). SBP and MAP reductions were the greatest at 60 minutes (17 and 8 mmHg; P < .05 for both). The median change in HR at 120 minutes was −9 beats/minute from baseline. This reduction was sustained through 240 minutes ( P < .05). No change in VR were seen at any time point. In multivariate regression, body temperature was the only characteristic independently associated with changes in MAP (coefficient 4.95, 95% CI 1.6-8.3). Conclusion: Administration of propofol during TTM did not affect cvSOFA score. The reductions in SBP, MAP, and HR did not have a corresponding change in vasopressor requirements and are likely not clinically meaningful. Propofol appears to be a safe choice for sedation in patients receiving targeted temperature management after cardiac arrest.

Principles of Pharmacotherapy of Seizures and Status Epilepticus

Status epilepticus is a neurological emergency with an outcome that is highly associated with the initial pharmacotherapy management that must be administered in a timely fashion. Beyond first-line therapy of status epilepticus, treatment is not guided by robust evidence. Optimal pharmacotherapy selection for individual patients is essential in the management of seizures and status epilepticus with careful evaluation of pharmacokinetic and pharmacodynamic factors. With the addition of newer antiseizure agents to the market, understanding their role in the management of status epilepticus is critical. Etiology-guided therapy should be considered in certain patients with drug-induced seizures, alcohol withdrawal, or autoimmune encephalitis. Some patient populations warrant special consideration, such as pediatric, pregnant, elderly, and the critically ill. Seizure prophylaxis is indicated in select patients with acute neurological injury and should be limited to the acute postinjury period.

Control of Shivering During Targeted Temperature Management

Targeted temperature management (TTM) is used frequently in patients with a variety of diseases, especially those who have experienced brain injury and/or cardiac arrest. Shivering is one of the main adverse effects of TTM that can often limit its implementation and efficacy. Shivering is the body's natural response to hypothermia and its deleterious effects can negate the benefits of TTM. The purpose of this article is to provide an overview of TTM strategies and shivering management.

The Influence of Therapeutics on Prognostication After Cardiac Arrest

PURPOSE OF REVIEW

The goal of this review is to highlight the influence of therapeutic maneuvers on neuro-prognostication measures administered to comatose survivors of cardiac arrest. We focus on the effect of sedation regimens in the setting of targeted temperature management (TTM), one of the principle interventions known to improve neurological recovery after cardiac arrest. Further, we discuss the critical need for novel markers, as well as refinement of existing markers, among patients receiving extracorporeal membrane oxygenation (ECMO) in the setting of failed conventional resuscitation, known as extracorporeal cardiopulmonary resuscitation (ECPR).

RECENT FINDINGS

Automated pupillometry may have some advantage over standard pupillary examination for prognostication following TTM, sedation, or the use of ECMO after cardiac arrest. New serum biomarkers such as Neurofilament light chain have shown good predictive abilities and need further validation in these populations. There is a high-level uncertainty in brain death declaration protocols particularly related to apnea testing and appropriate ancillary tests in patients receiving ECMO. Both sedation and TTM alone and in combination have been shown to affect prognostic markers to varying degrees. The optimal approach to analog-sedation is unknown, and requires further study. Moreover, validation of known prognostic markers, as well as brain death declaration processes in patients receiving ECMO is warranted. Data on the effects of TTM, sedation, and ECMO on biomarkers (e.g., neuron-specific enolase) and electrophysiology measures (e.g., somatosensory-evoked potentials) is sparse. The best approach may be one customized to the individual patient, a precision-medicine approach.

Hypothermia: Impact on plasticity following brain injury

Therapeutic hypothermia (TH) is a potent neuroprotectant against multiple forms of brain injury, but in some cases, prolonged cooling is needed. Such cooling protocols raise the risk that TH will directly or indirectly impact neuroplasticity, such as after global and focal cerebral ischemia or traumatic brain injury. TH, depending on the depth and duration, has the potential to broadly affect brain plasticity, especially given the spatial, temporal, and mechanistic overlap with the injury processes that cooling is used to treat. Here, we review the current experimental and clinical evidence to evaluate whether application of TH has any adverse or positive effects on postinjury plasticity. The limited available data suggest that mild TH does not appear to have any deleterious effect on neuroplasticity; however, we emphasize the need for additional high-quality preclinical and clinical work in this area.

Pediatric Post–Cardiac Arrest Care: A Scientific Statement From the American Heart Association

Successful resuscitation from cardiac arrest results in a post–cardiac arrest syndrome, which can evolve in the days to weeks after return of sustained circulation. The components of post–cardiac arrest syndrome are brain injury, myocardial dysfunction, systemic ischemia/reperfusion response, and persistent precipitating pathophysiology. Pediatric post–cardiac arrest care focuses on anticipating, identifying, and treating this complex physiology to improve survival and neurological outcomes. This scientific statement on post–cardiac arrest care is the result of a consensus process that included pediatric and adult emergency medicine, critical care, cardiac critical care, cardiology, neurology, and nursing specialists who analyzed the past 20 years of pediatric cardiac arrest, adult cardiac arrest, and pediatric critical illness peer-reviewed published literature. The statement summarizes the epidemiology, pathophysiology, management, and prognostication after return of sustained circulation after cardiac arrest, and it provides consensus on the current evidence supporting elements of pediatric post–cardiac arrest care.

Management of Comatose Survivors of Cardiac Arrest

PURPOSE OF REVIEW

Because the whole-body ischemia-reperfusion insult associated with cardiac arrest often results in brain injury, neurologists perform an important role in postresuscitation cardiac arrest care. This article provides guidance for the assessment and management of brain injury following cardiac arrest.

RECENT FINDINGS

Neurologists have many roles in postresuscitation cardiac arrest care: (1) early assessment of brain injury severity to help inform triage for invasive circulatory support or revascularization; (2) advocacy for the maintenance of a neuroprotective thermal, hemodynamic, biochemical, and metabolic milieu; (3) detection and management of seizures; (4) development of an accurate, multimodal, and conservative approach to prognostication; (5) application of shared decision-making paradigms around the likely outcomes of therapy and the goals of care; and (6) facilitation of the neurocognitive assessment of survivors. Therefore, optimal management requires early neurologist involvement in patient care, a detailed knowledge of postresuscitation syndrome and its complex interactions with prognosis, expertise in bringing difficult cases to their optimal conclusions, and a support system for survivors with cognitive deficits.

SUMMARY

Neurologists have a critical role in postresuscitation cardiac arrest care and are key participants in the treatment team from the time of first restoration of a perfusing heart rhythm through the establishment of rehabilitation services for survivors.

Use of Air-activated Thermal Devices during Recovery after Surgery in Mice

Laboratory mice (Mus musculus) are susceptible to hypothermia, especially during anesthetic events, disease states, and exposure to environmental stressors. Thermal support devices for small mammals are numerous, but often require a power source and may be impractical to use for cages on a rack. Air-activated thermal devices (AATD) are mixtures of chemicals that cause an exothermic reaction. In this study, we examined the environmental effects of AATD on internal cage temperatures without the use of additional equipment as well as the physiologic effects of AATD as postoperative thermal support in mice. For environmental experiments, temperatures measured inside the cage and above the AATD peaked at 35.6 ± 2.5 °C (13.4 °C higher than control cages). We also demonstrated that the amount of heat produced by AATD and its temporal distribution are dependent on cage and rack types. For physiologic experiments, mice were surgically implanted with an intraperitoneal temperature telemetry device in a static cage setting. Recovery times and final body temperature at 5 h postoperatively did not differ significantly between mice with and without AATD. During the first 0 to 3 h after mice returned to their home cages, body temperature dropped markedly in mice without AATD but not in mice with AATD. Based on this result the physiologic results of our study support that AATD can be useful in providing extended thermal support for mice housed in static microisolation cages to help maintain body temperature postsurgically. Environmental results of our studies demonstrated that AATD provide local clinically relevant thermal support for 2.5 to 6 h, depending on cage set-up.

2-Iminobiotin Superimposed on Hypothermia Protects Human Neuronal Cells from Hypoxia-Induced Cell Damage: An in Vitro Study

Perinatal asphyxia represents one of the major causes of neonatal morbidity and mortality. Hypothermia is currently the only established treatment for hypoxic-ischemic encephalopathy (HIE), but additional pharmacological strategies are being explored to further reduce the damage after perinatal asphyxia. The aim of this study was to evaluate whether 2-iminobiotin (2-IB) superimposed on hypothermia has the potential to attenuate hypoxia-induced injury of neuronal cells. In vitro hypoxia was induced for 7 h in neuronal IMR-32 cell cultures. Afterwards, all cultures were subjected to 25 h of hypothermia (33.5°C), and incubated with vehicle or 2-IB (10, 30, 50, 100, and 300 ng/ml). Cell morphology was evaluated by brightfield microscopy. Cell damage was analyzed by LDH assays. Production of reactive oxygen species (ROS) was measured using fluorometric assays. Western blotting for PARP, Caspase-3, and the phosphorylated forms of akt and erk1/2 was conducted. To evaluate early apoptotic events and signaling, cell protein was isolated 4 h post-hypoxia and human apoptosis proteome profiler arrays were performed. Twenty-five hour after the hypoxic insult, clear morphological signs of cell damage were visible and significant LDH release as well as ROS production were observed even under hypothermic conditions. Post-hypoxic application of 2-IB (10 and 30 ng/ml) reduced the hypoxia-induced LDH release but not ROS production. Phosphorylation of erk1/2 was significantly increased after hypoxia, while phosphorylation of akt, protein expression of Caspase-3 and cleavage of PARP were only slightly increased. Addition of 2-IB did not affect any of the investigated proteins. Apoptosis proteome profiler arrays performed with cellular protein obtained 4 h after hypoxia revealed that post-hypoxic application of 2-IB resulted in a ≥ 25% down regulation of 10/35 apoptosis-related proteins: Bad, Bax, Bcl-2, cleaved Caspase-3, TRAILR1, TRAILR2, PON2, p21, p27, and phospho Rad17. In summary, addition of 2-IB during hypothermia is able to attenuate hypoxia-induced neuronal cell damage in vitro. Combination treatment of hypothermia with 2-IB could be a promising strategy to reduce hypoxia-induced neuronal cell damage and should be considered in further animal and clinical studies.

Valproate Protein Binding Is Highly Variable in ICU Patients and Not Predicted by Total Serum Concentrations: A Case Series and Literature Review

STUDY OBJECTIVE

The free fraction of valproate (the pharmacologically active moiety, normally 5-10%) may vary significantly in critically ill patients, but this topic is understudied, with only four prior intensive care unit (ICU) case reports. The objective of this study was to evaluate the range of valproate plasma protein binding in ICU patients.

DESIGN

Observational study of consecutive ICU patients.

SETTING

Neurocritical and medical critical care services in a nonuniversity academic medical center.

PATIENTS

Consecutive ICU patients treated with valproate with serum albumin less than 4 g/dl.

MEASUREMENTS AND MAIN RESULTS

Simultaneous total and free trough serum valproate concentrations were measured as were serum creatinine, blood urea nitrogen, albumin, platelets, and transaminase values. The reference concentration range was 50-125 mg/L (total) and 5-17 mg/L (free). Valproate concentrations were categorized as within reference range, low, or high, and as concordant if both concentrations were in the same category. Data are reported as median (interquartile range). Fifteen patients (nine men) were evaluated. The median age was 63 (34-70) years. The valproate dose was 3 g/day (35 mg/kg/day). No patient had a valproate free fraction of 5-10%; the median was 48%, and the range was 15-89%. Total and free concentrations showed poor correlation (0.43) and were concordant in only two patients (both in the reference range). Free valproate concentration was poorly predicted by an equation correcting for albumin (r = 0.45). Suspected adverse drug events occurred in 10 patients: hyperammonemia in 7 of 12 tested (58%), elevated transaminases in 2 of 15 (13%), and thrombocytopenia in 5 of 15 (33%).

CONCLUSIONS

Protein binding of valproate was highly inconsistent in this cohort of ICU patients, and total valproate concentrations did not predict free concentrations, even when correcting for albumin. Additional research to define best practice for dosing and monitoring valproate and the relationship between free valproate concentrations and clinical or adverse effects in ICU patients is needed.

Neuroprognostication after adult cardiac arrest treated with targeted temperature management: task force for Belgian recommendations

The prognosis of patients who are admitted to the hospital after cardiac arrest often relies on neurological examination, which could be significantly influenced by the use of sedative drugs or the implementation of targeted temperature management. The need for early and accurate prognostication is crucial as up to 15-20% of patients could be considered as having a poor outcome and may undergo withdrawal of life-sustaining therapies while a complete neurological recovery is still possible. As current practice in Belgium is still based on a very early assessment of neurological function in these patients, the Belgian Society of Intensive Care Medicine created a multidisciplinary Task Force to provide an optimal approach for monitoring and refine prognosis of CA survivors. This Task Force underlined the importance to use a multimodal approach using several additional tools (e.g., electrophysiological tests, neuroimaging, biomarkers) and to refer cases with uncertain prognosis to specialized centers to better evaluate the extent of brain injury in these patients.

Editor's Choice-The cardiovascular implications of sedatives in the cardiac intensive care unit

Patients admitted to the cardiac intensive care unit frequently develop multi-organ system dysfunction associated with their cardiac disease. In many cases, invasive mechanical ventilation is required, which often necessitates sedation for patient-ventilator synchrony, reduction of work of breathing, and patient comfort. In this paper, we describe the use of common sedatives available in the endotracheally intubated critically ill patient and emphasize the clinical and cardiovascular effects. We review γ-aminobutyric acid agonists such as etomidate, benzodiazepines, and propofol, the centrally acting α₂-agonist dexmedetomidine, and the N-methyl-D-aspartate receptor antagonist ketamine. Additionally, we outline the use of opioids and their role in potentiating other sedatives. We note that some sedatives are associated with increased delirium rates, and emphasize that judicious strategies minimizing sedative use are associated with decreases in morbidity and mortality. We also discuss standardized sedation assessment scales and highlight the importance of sedation weaning. Finally, we offer recommendations for sedation use during therapeutic hypothermia, and discuss the use of adjuvant neuromuscular blocking agents.

The Evolving Paradigm of Individualized Postresuscitation Care After Cardiac Arrest

The postresuscitation period after a cardiac arrest is characterized by a wide range of physiological derangements. Variations between patients include preexisting medical problems, the underlying cause of the cardiac arrest, presence or absence of hemodynamic and circulatory instability, severity of the ischemia-reperfusion injury, and resuscitation-related injuries such as pulmonary aspiration and rib or sternal fractures. Although protocols can be applied to many elements of postresuscitation care, the widely disparate clinical condition of cardiac arrest survivors requires an individualized approach that stratifies patients according to their clinical profile and targets specific treatments to patients most likely to benefit. This article describes such an individualized approach, provides a practical framework for evaluation and triage at the bedside, and reviews concerns specific to all members of the interprofessional postresuscitation care team.

Analgesia, sedation, and neuromuscular blockade during targeted temperature management after cardiac arrest

The approach to sedation, analgesia, and neuromuscular blockade during targeted temperature management (TTM) remains largely unstudied, forcing clinicians to adapt previous research from other patient environments. During TTM, very little data guide drug selection, doses, and specific therapeutic goals. Sedation should be deep enough to prevent awareness during neuromuscular blockade, but titration is complex as metabolism and clearance are delayed for almost all drugs during hypothermia. Deeper sedation is associated with prolonged intensive care unit (ICU) and ventilator therapy, increased delirium and infection, and delayed wakening which can confound early critical neurological assessments, potentially resulting in erroneous prognostication and inappropriate withdrawal of life support. We review the potential therapeutic goals for sedation, analgesia, and neuromuscular blockade during TTM; the adverse events associated with that treatment; data suggesting that TTM and organ dysfunction impair drug metabolism; and controversies and potential benefits of specific monitoring. We also highlight the areas needing better research to guide our therapy.

Effect of Hypothermia and Targeted Temperature Management on Drug Disposition and Response Following Cardiac Arrest: A Comprehensive Review of Preclinical and Clinical Investigations

Targeted temperature management (TTM) has been shown to reduce mortality and improve neurological outcomes in out-of-hospital cardiac arrest (CA) patients and in neonates with hypoxic-ischemic encephalopathy (HIE). TTM has also been associated with adverse drug events in the critically ill patient due to its effect on drug pharmacokinetics (PKs) and pharmacodynamics (PDs). We aim to evaluate the current literature on the effect of TTM on drug PKs and PDs following CA. MEDLINE/PubMed databases were searched for publications, which include the MeSH terms hypothermia, drug metabolism, drug transport, P450, critical care, cardiac arrest, hypoxic-ischemic encephalopathy, pharmacokinetics, and pharmacodynamics between July 2006 and October 2015. Twenty-three studies were included in this review. The studies demonstrate that hypothermia impacts PK parameters and increases concentrations of cytochrome-P450-metabolized drugs in the cooling and rewarming phase. Furthermore, the current data demonstrate a combined effect of CA and hypothermia on drug PK. Importantly, these effects can last greater than 4-5 days post-treatment. Limited evidence suggests hypothermia-mediated changes in the Phase II metabolism and the Phase III transport of drugs. Hypothermia also has been shown to potentially decrease the effect of specific drugs at the receptor level. Therapeutic hypothermia, as commonly deployed/applied during TTM, alters PK, and elevates concentrations of several commonly used medications. Hypothermia-mediated effects are an important factor when dosing and monitoring patients undergoing TTM treatment.

Impaired biological response to aspirin in therapeutic hypothermia comatose patients resuscitated from out-of-hospital cardiac arrest

AIM OF THE STUDY

Acute coronary syndrome is one of the main causes of out-of-hospital cardiac arrest (OHCA). OHCA patients are particularly exposed to high platelet reactivity (HPR) under aspirin (ASA) treatment. The aim was to evaluate HPR-ASA in therapeutic hypothermia comatose patients resuscitated from OHCA.

METHODS AND RESULTS

Twenty-two consecutive patients with OHCA of cardiac origin were prospectively included after therapeutic hypothermia and randomized to receive ASA 100mg per day, either intravenously (n=13) or orally via a gastric tube (n=9). ADP inhibitors (prasugrel or, if contra-indicated, clopidogrel) were administered in the event of angioplasty. HPR-ASA was assessed by light transmission aggregometry (LTA) with arachidonic acid (AA) and by the PFA-100(®) system with collagen/epinephrine. Clinical, biological and angiographic characteristics were similar in both groups. Using LTA-AA, maximum aggregation intensity was significantly lower in the intravenous group compared to the oral group (15% vs. 29%, respectively; p=0.04). Overall, 10 patients (45%) had HPR-ASA (38% intravenously vs 56% orally; p=0.7). Similarly, closure time was significantly increased in the IV group (277s vs. 155s, respectively; p=0.04).

CONCLUSION

This study suggests that impaired response to both intravenous and oral aspirin is frequent in comatose patients resuscitated from OHCA.