Intuitive use and usability of ventricular assist device peripheral components in simulated emergency conditions

Ventricular assist devices (VADs) are now increasingly used to prolong the lives of end-stage heart failure patients. These patients vary greatly in age, alertness, activity, and home environment. In daily routine, but especially in emergencies or in conjunction with non-VAD-correlated diseases, the untrained, intuitive use and application of VAD peripherals by relatives, laypersons, and paramedics becomes important. Correct intuitive use may be a matter of life and death. The aim of this study was to evaluate the intuitive usability of these systems and to identify key features needed to optimize intuitive use. Paramedics (n=96) were confronted with a simulated emergency situation involving VAD peripherals mounted on a dummy. Three conditions were simulated: the VAD disconnected from its power source (n=44); both VAD batteries empty (n=44); and a discharged VAD battery mistakenly connected in place of a charged one (n=8). Two VAD systems were assessed: the Heartware HVAD and the Thoratec HeartMate II. An appropriate emergency card developed by our center was available in each case. Actions were videotaped, response times were measured, and a standardized questionnaire was completed after the simulation. The problem was solved by 71% of the participants (HVAD 83%, HMII 60%) with 87% using the emergency card. Only 4% could solve the problem without. Cardiac massage, which was unnecessary, was started by 44%, while 18% complained about unnecessarily difficult conditions (e.g., irritation from the acoustic alarm, complexity of the emergency card, error-prone procedures). Better component labeling (e.g., displays, control elements, connectors) was recommended by 56%. A thoroughly color-coded connection system was especially desired. Cable- and connector-related difficulties were reported by 23%. The study indicated that VAD systems should be self-explaining, with clear labeling of components and connectors, that a clearer emergency card is pivotal and that similar basic handling and emergency procedures for all VAD types would be desirable.

The beneficial effect of mild therapeutic hypothermia depends on the time of complete circulatory standstill in patients with cardiac arrest

AIM

Mild therapeutic hypothermia has shown to improve long-time survival as well as favorable functional outcome after cardiac arrest. Animal models suggest that ischemic durations beyond 8 min results in progressively worse neurologic deficits. Based on these considerations, it would be obvious that cardiac arrest survivors would benefit most from mild therapeutic hypothermia if they have reached a complete circulatory standstill of more than 8 min.

METHODS

In this retrospective cohort study we included cardiac arrest survivors of 18 years of age or older suffering a witnessed out-of-hospital cardiac arrest, which remain comatose after restoration of spontaneous circulation. Data were collected from 1992 to 2010. We investigated the interaction of 'no-flow' time on the association between post arrest mild therapeutic hypothermia and good neurological outcome. 'No-flow' time was categorized into time quartiles (0, 1-2, 3-8, >8 min).

RESULTS

One thousand-two-hundred patients were analyzed. Hypothermia was induced in 598 patients. In spite of showing a statistically significant improvement in favorable neurologic outcome in all patients treated with mild therapeutic hypothermia (odds ratio [OR]: 1.49; 95% confidence interval [CI]: 1.14-1.93) this effect varies with 'no-flow' time. The effect is significant in patients with 'no-flow' times of more than 2 min (OR: 2.72; CI: 1.35-5.48) with the maximum benefit in those with 'no-flow' times beyond 8 min (OR: 6.15; CI: 2.23-16.99).

CONCLUSION

The beneficial effect of mild therapeutic hypothermia increases with cumulative time of complete circulatory standstill in patients with witnessed out-of-hospital cardiac arrest.

Surface cooling for induction of mild hypothermia in conscious healthy volunteers - a feasibility trial

Introduction

Animal and human studies suggest beneficial outcome effects of mild hypothermia for stroke, for acute myocardial infarction, and for cardiogenic shock. The aim of this study was to investigate the feasibility and safety of non-invasive surface cooling for induction and maintenance of mild hypothermia (32 to 34°C) in healthy, conscious volunteers.

Methods

The trial was set at a clinical research ward in a tertiary care center, and included 16 healthy male volunteers 18 to 70 years old. Surface cooling was established by a novel non-invasive cooling pad with an esophageal target temperature of 32 to 34°C and maintenance for six hours. Shivering-control was achieved with meperidine and buspirone and additional administration of magnesium in eight subjects.

Results

The primary endpoint to reach a target temperature of 32 to 34°C was only reached in 6 of the 16 participating subjects. Temperatures below 35°C were reached after a median cooling time of 53 minutes (38 to 102 minutes). Cooling rate was 1.1°C/h (0.7 to 1.8°C). Additional administration of magnesium had no influence on cooling rate. At no time during the cooling procedure did the participants report uncomfortable conditions for which termination of cooling had to be considered. No severe skin damage was reported.

Conclusions

Cooling to body temperature below 35°C by the use of non-invasive surface cooling is feasible and safe in conscious healthy volunteers. Further studies are needed to investigate an altered cooling protocol to achieve temperatures below 35°C.

Trial Registration

ISRCTN: ISRCTN50530495

Mild therapeutic hypothermia is associated with favourable outcome in patients after cardiac arrest with non-shockable rhythms

AIM

Mild therapeutic hypothermia (32-34°C) improves neurological recovery and reduces the risk of death in comatose survivors of cardiac arrest when the initial rhythm is ventricular fibrillation or pulseless ventricular tachycardia. The aim of the presented study was to investigate the effect of mild therapeutic hypothermia (32-34°C for 24h) on neurological outcome and mortality in patients who had been successfully resuscitated from non-ventricular fibrillation cardiac arrest.

METHODS

In this retrospective cohort study we included cardiac arrest survivors of 18 years of age or older suffering a witnessed out-of-hospital cardiac arrest with asystole or pulseless electric activity as the first documented rhythm. Data were collected from 1992 to 2009. Main outcome measures were neurological outcome within six month and mortality after six months.

RESULTS

Three hundred and seventy-four patients were analysed. Hypothermia was induced in 135 patients. Patients who were treated with mild therapeutic hypothermia were more likely to have good neurological outcomes in comparison to patients who were not treated with hypothermia with an odds ratio of 1.84 (95% confidence interval: 1.08-3.13). In addition, the rate of mortality was significantly lower in the hypothermia group (odds ratio: 0.56; 95% confidence interval: 0.34-0.93).

CONCLUSION

Treatment with mild therapeutic hypothermia at a temperature of 32-34°C for 24h is associated with improved neurological outcome and a reduced risk of death following out-of-hospital cardiac arrest with non-shockable rhythms.

Relationship between time to target temperature and outcome in patients treated with therapeutic hypothermia after cardiac arrest

INTRODUCTION

Our purpose was to study whether the time to target temperature correlates with neurologic outcome in patients after cardiac arrest with restoration of spontaneous circulation treated with therapeutic mild hypothermia in an academic emergency department.

METHODS

Temperature data between April 1995 and June 2008 were collected from 588 patients and analyzed in a retrospective cohort study by observers blinded to outcome. The time needed to achieve an esophageal temperature of less than 34°C was recorded. Survival and neurological outcomes were determined within six months after cardiac arrest.

RESULTS

The median time from restoration of spontaneous circulation to reaching a temperature of less than 34°C was 209 minutes (interquartile range [IQR]: 130-302) in patients with favorable neurological outcomes compared to 158 min (IQR: 101-230) (P < 0.01) in patients with unfavorable neurological outcomes. The adjusted odds ratio for a favorable neurological outcome with a longer time to target temperature was 1.86 (95% CI 1.03 to 3.38, P = 0.04).

CONCLUSIONS

In comatose cardiac arrest patients treated with therapeutic hypothermia after return of spontaneous circulation, a faster decline in body temperature to the 34°C target appears to predict an unfavorable neurologic outcome.

Post-resuscitation care at the emergency department with critical care facilities--a length-of-stay analysis

AIM OF THE STUDY

An emergency department providing critical care will have an effect on outcome and intensive-care-units' resources by avoiding unnecessary or futile intensive-care admissions and thereby save hospital expenses. The study focussed on this result.

METHODS

The study employed a retrospective analysis of prospectively collected data of out-of-hospital cardiac arrest patients with return of spontaneous circulation, comatose on arrival. Outcomes and length of stay of patients who either stayed at the 'emergency department only' or were 'transferred in addition to an intensive care unit' were compared. Linear regression with log length of stay as outcome and 'emergency department only' as predictor with covariates was used for modelling.

RESULTS

From 1991 to 2008, out of 1236 patients (age 57 ± 15 years, female 31%), the 'emergency department only' group (n=349 (28%)) survived to discharge in 81(23%) cases, with a median length-of-stay in critical care of 1.7 (interquartile range 0.8; 3.1) days. The patients 'transferred in addition to an intensive care unit' (n=887 (72%)), with a survival rate of 55% (n=486, p<0.001) stayed 10 (5; 18) days (p<0.001). The length-of-stay in hospital was significantly shorter if patients were treated in the 'emergency department only' independent of other cardiac-arrest-related factors (regression coefficient -1.42, confidence interval -1.60 to -1.24).

CONCLUSIONS

An emergency department with critical care prevents admissions to intensive care units in 28% of patients with out-of-hospital cardiac arrest. It saves intensive-care-unit resources and shortens length of stay for comatose out-of-hospital cardiac-arrest survivors, regardless of their outcome.