Therapeutic Hypothermia and Temperature Management

Liquid ventilation was initially proposed for lung lavage and respiratory support. More recently, it was also investigated as an experimental strategy for ultrafast cooling or organ preservation during ischemic disorders. The goal of this article is to identify and review the studies that investigated liquid ventilation in the field of resuscitation sciences. An exhaustive analysis of the literature was performed using the Medline database up to 15th September 2015. Articles were selected according to their relevance. All articles focusing on respiratory support were excluded. On the basis of 76 retrieved studies from the Medline database, 29 were included in this review. All studies were experimental reports and most of them investigated the cooling properties of liquid ventilation in animal models of experimental cardiac arrest or coronary artery occlusion in rabbits or pigs. Animal studies demonstrated a wide range of potential applications of total liquid ventilation in resuscitation sciences. This strategy is able to provide ultrafast cooling, independent of the body weight. In animal models of cardiopulmonary resuscitation, it was shown to provide potent benefits widely linked to cooling rapidity.

Old age is considered a negative prognostic factor after out-of-hospital cardiac arrest (OHCA). The purpose of this study was to assess the benefit of therapeutic hypothermia (TH) on survival and neurologic outcome in the elderly. This is a retrospective study of patients treated for OHCA from April 2011 to August 2013 in a regional cardiac system. Patients with return of spontaneous circulation (ROSC) are directed to designated cardiac receiving centers with established TH protocols. The decision to initiate TH is determined by the treating physician. All patients 65 years or older were identified. Patients were excluded if awake and responsive in the emergency department, died before hospital admission, or had preexisting coma. The adjusted odds ratio for survival with good neurologic outcome (defined as cerebral performance category [CPC] 1 or 2) was calculated for patients who received TH compared to a reference group without TH. There were 1612 patients, of whom 552 (34%) received TH. Median age was 78 (inter-quartile range [IQR] 71–85); 56% was male. 493 (31%) patients survived to hospital discharge, 266 (17%) with CPC of 1 or 2. Of 1292 patients considered for TH, 192 (25%) of 552 patients who received TH survived to hospital discharge and 97 (18%) with good neurologic outcome compared to 150 (20%) and 57 (8%), respectively, without TH. The adjusted odds ratio for survival with good neurologic outcome for TH was 2.0 (95% CI 1.3–3.3). TH is associated with improved neurologic outcome in the elderly population.

Research describing survivors of sudden cardiac arrest (SCA) has centered on quantifying functional ability, perceived quality of life, and neurocognitive assessment. Many gaps remain, however, regarding survivors' psychosocial perceptions of life in the aftermath of cardiac arrest. An important influence upon those perceptions is the presence of support and its role in a survivor's life. An Internet-based pilot survey study was conducted to gather data from SCA survivors and friends and/or family members (FFMs) representing their support system. The survey was distributed to members of the Sudden Cardiac Arrest Foundation (SCAF) via the Internet by SCAF leadership. Questions included both discrete multiple-choice and open-ended formats. Inductive thematic analyses were completed by three independent researchers trained in qualitative research methodology to identify primary themes consistent among study participants until thematic saturation was achieved. No statistical inferences were made. A total of 205 surveys were returned over the 5-month study period (July to November 2013); nine were received blank, leaving 196 surveys available for review. Major themes identified for survivors (N = 157) include the significance of and desire to share experiences with others; subculture identification (unique experience from those suffering a heart attack); and the need to seek a new normal, both personally and inter-personally. Major themes identified for FFMs (N = 39) include recognition of loved one's memory loss; a lack of information at discharge, including expectations after discharge; and concern for the patient experiencing another cardiac arrest. This pilot, qualitative survey study suggests several common themes important to survivors, and FFMs, of cardiac arrest. These themes may serve as a basis for future patient-centered focus groups and the development of patient-centered guidelines for patients and support persons of those surviving cardiac arrest.

To explore if the brain biomarker neuron-specific enolase (NSE) in combination with a biomarker for stress; CT-proAVP (copeptin), oxidation; peroxiredoxin 4 (Prx4), inflammation; procalcitonin (PCT), or with biomarkers from the heart; midregional proatrial natriuretic peptide (MR-proANP), or troponin T (TnT) can improve the prognostic accuracy of long-term outcome after out-of-hospital cardiac arrest (OHCA). Serum samples from cardiac arrest patients, treated at 33°C for 24 hours, were collected serially at 12, 24, and 48 hours after cardiac arrest. The concentration of the investigated biomarkers was measured using stored samples, and long-term outcome was evaluated by the cerebral performance category (CPC) at 6 months. Poor outcome was defined as CPC 3–5. Sixty-two patients with OHCA of presumed cardiac cause were included. NSE had best prognostic accuracy for poor outcome at 48 hours with a receiver operating characteristic area under curve (AUC) of 0.94 (95% confidence interval [CI] 0.87–1). The combination of NSE with TnT, both at 48 hours, increased the AUC to 0.98 (95% CI 0.95–1, likelihood ratio [LR] test p-value 0.07, net reclassification index [NRI] <0.001); NSE and MR-proANP, both at 12 hours, yielded an AUC of 0.91 (95% CI 0.80–1, LR test p-value 0.0014, NRI p-value 0.003); NSE at 48 hours with MR-proANP at 12 hours yielded an AUC of 0.97 (95% CI 0.92–1, LR test p-value 0.055, NRI p-value 0.04). This pilot study suggests that a combination of biomarkers with NSE could be beneficial for improving early prognostication of long-term outcome following OHCA.

We evaluated an endovascular cooling method to modulate core temperature in trauma swine models with and without fluid support. Anesthetized swine (N = 80) were uninjured (SHAM) or injured through a bone fracture plus soft tissue injury or an uncontrolled hemorrhage and then subdivided to target body temperatures of 38°C (normothermia) or 33°C (hypothermia) by using a Thermogard endovascular cooling device (Zoll Medical). Temperature regulation began simultaneously at onset of injury (T0). Body temperatures were recorded from a rectal probe (Rec Temp) and from a central pulmonary artery catheter (PA Temp). At T15, swine received 500 mL IV Hextend over 30 minutes or no treatment (NONE) with continued monitoring until 3 hours from injury. Hypothermia was attained in 105 ± 39 minutes, at a cooling rate of −0.061°C ± 0.007°C/min for NONE injury groups. Postinjury Hextend administration resulted in faster cooling (−0.080°C ± 0.006°C/min); target temperature was reached in 83 ± 11 minutes (p < 0.05). During active cooling, body temperature measured by the PA Temp was significantly cooler than the Rec Temp due to the probe's closer proximity to the blood-cooling catheter balloons (p < 0.05). This difference was smaller in SHAM and fluid-supported injury groups (1.1°C ± 0.4°C) versus injured NONE groups (2.1°C ± 0.3°C). Target temperatures were correctly maintained thereafter in all groups. In normothermia groups, there was a small initial transient overshoot to maintain 38°C. Despite the noticeable difference between PA Temp and Rec Temp until target temperature was attained, this endovascular method can safely induce moderate hypothermia in anesthetized swine. However, likely due to their compromised hemodynamic state, cooling in hypovolemic and/or injured patients will be different from those without injury or those that also received fluids.

Hyperthermia from a central cause is associated with increased morbidity and mortality. Dysfunction of brainstem thermoregulatory pathways may explain the intractable rise in temperature. Antipyretics, dantrolene, bromocriptine, and surface and intravascular cooling devices have been attempted for temperature control. We report the case of a 54-year-old woman with history of hypertension who presented with pontine hemorrhage with extension into the midbrain and medulla. On days 8–9 of her hospital admission, she developed intractable fever and expired the same day despite aggressive treatment of hypothermia, including antipyretics, ice lavage, cold fluid boluses, surface cooling, dantrolene, and bromocriptine. Hyperthermia from brainstem hemorrhage can be difficult to manage with current treatment options. Early recognition of those patients who may develop hyperthermia could lead to early intervention and possibly better outcomes. More evidence from prospective randomized controlled trials will elucidate the risk–benefit profile of achieving normothermia with aggressive fever control in these patients.