Post-hypothermia fever is associated with increased mortality after out-of-hospital cardiac arrest

Sinus bradycardia during hypothermia in comatose survivors of out-of-hospital cardiac arrest - a new early marker of favorable outcome?

BACKGROUND

Bradycardia is a common finding in patients undergoing therapeutic hypothermia (TH) following out-of-hospital cardiac arrest (OHCA), presumably as a normal physiological response to low body temperature. We hypothesized that a normal physiological response with sinus bradycardia (SB) indicates less neurological damage and therefore would be associated with lower mortality.

METHODS

We studied 234 consecutive comatose survivors of OHCA with presumed cardiac etiology and shockable primary rhythm, who underwent a full 24-h TH-protocol (33°C) at a tertiary heart center (years: 2004-2010). Primary endpoint was 180-day mortality; secondary endpoint was favorable neurological outcome (180-day cerebral performance category: 1-2).

RESULTS

SB, defined as sinus rhythm <50 beats per minute during TH, was present in 115 (49%) patients. Baseline characteristics including sex, witnessed arrest, bystander cardiopulmonary resuscitation and time to return of spontaneous circulation were not different between SB- and no-SB patients. However, SB-patients were younger, 57±14 vs. 63±14 years, p<0.001 and less frequently had known heart failure (7% vs. 20%, p<0.01). Patients experiencing SB during the hypothermia phase of TH had a 17% 180-day mortality rate compared to 38% in no-SB patients (p<0.001), corresponding to a 180-day hazard ratio (HRadjusted=0.45 (0.23-0.88, p=0.02)) in the multivariable analysis. Similarly, SB during hypothermia was directly associated with lower odds of unfavorable neurological outcome (ORunadjusted=0.42 (0.23-0.75, p<0.01).

CONCLUSION

Sinus bradycardia during therapeutic hypothermia is independently associated with a lower 180-day mortality rate and may thus be a novel, early marker of favorable outcome in comatose survivors of OHCA.

Fever and therapeutic normothermia in severe brain injury: an update

PURPOSE OF REVIEW

Fever is common in the ICU among patients with severe brain injury. Fever has been consistently shown to exacerbate brain injuries in animal models and has been consistently associated with poor outcome in human studies. However, whether fever control improves outcome and the ideal means of fever control remain unknown. This review will address recent literature on the impact of fever on severe brain injury and on interventions to maintain normothermia.

RECENT FINDINGS

Current guidelines generally recommend maintenance of normothermia after brain injury but have scant recommendations on methods to do this. Observational trials have continued to demonstrate the association between fever and poor outcome after severe brain injury. Recent trials have shown the efficacy of more aggressive approaches to fever reduction, whereas a large randomized trial showed the relative ineffectiveness of acetaminophen alone for fever control. Several studies have also described the impact of fever and of fever control on brain physiology.

SUMMARY

The value of therapeutic normothermia in the neurocritical care unit (NCCU) is increasingly accepted, yet prospective trials that demonstrate a functional benefit to patients are lacking.

Enhancing approaches to therapeutic hypothermia in patients with sudden circulatory arrest

Cardiac arrest is common and causes substantial morbidity and mortality. Despite advances in prevention and resuscitation, most patients remain unconscious and survival remains poor. Therapeutic hypothermia (32-34 °C) has emerged as a potent neuroprotective modality following resuscitation. In early clinical trials, application of therapeutic hypothermia improved survival in patients with ventricular fibrillation (VF), which led to the recommended use of therapeutic hypothermia for patients resuscitated from VF. However, two recent clinical trials have challenged some assumptions. First, the use of paramedic-initiated rapid infusion of cold crystalloids as a mean to achieve faster cooling rates after resuscitation in patients with and without VF arrest did not improve survival. Second, once patients were admitted to the hospital, targeting their temperature to 33 versus 36 °C for 36 h (in addition to active hyperthermia prevention) after out-of-hospital cardiac arrest did not to change clinical outcomes, suggesting that 36 °C may represent the target temperature instead of temperatures of less than 34 °C.

A 4-year implementation strategy of aggressive post-resuscitation care and temperature management after cardiac arrest

BACKGROUND

target temperature management (TTM) not only improves neurological outcome and survival but has given momentum to a more aggressive and comprehensive treatment after resuscitation. Yet, implementation issues represent the main obstacle to systematic treatment with TTM and aggressive post-resuscitation care. We devised a strategy to introduce, monitor and improve the quality of aggressive treatment after resuscitation, including TTM.

METHODS

standard operative procedures on aggressive post-resuscitation care, written jointly by physicians and nurses, were introduced in November 2004. Data of all resuscitated patients admitted to the ICU were prospectively acquired for 4 years. Periodic audits (every 16 months) were programmed, leading to three equally long periods. Several critical issues were identified after each audit and addressed subsequently, leading to a growing complexity of care. Moreover, after 2 years we introduced an educational programme with medical credits for all staff attending critically ill patients. Neurological outcome and survival at hospital discharged were compared to historical controls of the preceding 22 months.

RESULTS

129 consecutively resuscitated patients were admitted to the ICU in the 4-year study period. Of these, 96 (74%) were treated with TTM and aggressive post-resuscitation care. Favourable neurological recovery among patients discharged alive significantly improved in the 4-year intervention period (81% vs. 50% in historical controls, p<0.01). A composite endpoint of mortality and poor neurological outcome also improved (64% vs. 82% respectively, p<0.05). Overall survival increased throughout the 4 years, leading to a significant improvement in the 3rd period compared to historical controls (60% vs. 35%; p<0.05).

CONCLUSIONS

we propose a strategy to successfully introduce and implement TTM and aggressive post-resuscitation care via standard operative procedures, periodic audits and feedback. Continuous education among other factors contributed to a significant improvement in neurological outcome and a progressive increase in survival.

Therapeutic hypothermia after in-hospital cardiac arrest: a critique

More than 210,000 in-hospital cardiac arrests occur annually in the United States. Use of moderate therapeutic hypothermia (TH) in comatose survivors after return of spontaneous circulation following out-of-hospital cardiac arrest (OOH-CA) caused by ventricular fibrillation or pulseless ventricular tachycardia is recommended strongly by many professional organizations and societies. The use of TH after cardiac arrest associated with nonshockable rhythms and after in-hospital cardiac arrest (IH-CA) is recommended to be considered by these same organizations and is being applied widely. The use in these latter circumstances is based on an extrapolation of the data supporting its use after out-of-hospital cardiac arrest associated with shockable rhythms. The purpose of this article is to review the limitations of existing data supporting these extended application of TH after cardiac arrest and to suggest approaches to this dilemma. The data supporting its use for OOH-CA appear to this author, and to some others, to be rather weak, and the data supporting the use of TH for IH-CA appear to be even weaker and to include no randomized controlled trials (RCTs) or supportive observational studies. The many reasons why TH might be expected to be less effective following IH-CA are reviewed. The degree of neurologic injury may be more severe in many of these cases and, thus, may not be responsive to TH as currently practiced following OOH-CA. The potential adverse consequences of the routine use of TH for IH-CA are listed and include complications associated with TH, interference with diagnostic and interventional therapy, and use of scarce personnel and financial resources. Most importantly, it inhibits the ability of researchers to conduct needed RCTs. The author believes that the proper method of providing TH in these cases needs to be better defined. Based on this analysis the author concludes that TH should not be used indiscriminantly following most cases of IH-CA, and instead clinicians should concentrate their efforts in conducting high-quality large RCTs or large-scale, well-designed prospective observation studies to determine its benefits and identify appropriate candidates.

Serotonin syndrome after therapeutic hypothermia for cardiac arrest: a case series

AIM

To describe causes, manifestations, and diagnosis of serotonin syndrome following therapeutic hypothermia (TH) after cardiac arrest.

METHODS

Retrospective case series from a tertiary academic medical center.

RESULTS

Three male patients suffered witnessed out-of-hospital cardiac arrests and were treated with induced TH. Initial cardiac rhythms included asystole in two and ventricular fibrillation in one. Following completion of rewarming, all three developed neurological signs unexpected for their clinical condition. These included rigidity, hyperreflexia, diffuse tremors, ankle clonus, and marked agitated delirium. Patients also were febrile, hypertensive, and tachycardic. A diagnosis of serotonin syndrome was made in all cases and serotonergic medications were discontinued. All three patients recovered consciousness and two made a full neurological recovery. One patient remained dependent on others for activities of daily living at the time of hospital discharge because of short-term memory impairment.

CONCLUSIONS

Unexpected neurologic findings and prolonged high fever following recovery from TH can be manifestations of serotonin syndrome rather than post-cardiac arrest anoxic brain injury.