TTM Audit 2021 RLI
Jan Hansel & Simon Mackie
15/06/2021
Background
The optimal medical management of patients with return of spontaneous circulation (ROSC) who remain comatose following cardiac arrest is not known. An element of so-called post ROSC care bundles is targeted temperature management, previously known as therapeutic hypothermia. Some of the landmark trials done to date have suggested that cooling comatose patients following cardiac arrest may be beneficial in terms of neurologic outcomes. The Barnard trial in 2002 looked at patients following a shockable cardiac arrest had improved outcomes when cooled to a core temperature of 33°C, compared to the control group.1 Around the same time, the HACA trial confirmed the findings of Barnard et al.2 In 2013 Nielsen et al. published the results of the TTM trial in NEJM, demonstrating that patients who were kept normothermic at 36°C had similar outcomes to patients that had been cooled.3 The 2019 HYPERION trial by Lascarrou et al. further revealed the potential benefit of therapeutic hypothermia to patients resuscitated from cardiac arrest presenting with non-shockable rhythms.4 Further trials in this area are ongoing (chiefly the TTM2 trial), but presently the International Liaison Committee on Resuscitation (ILCOR) guidelines recommend targeted temperature management.5,6
The following recommendations by ILCOR are valid as of 2015:
We recommend targeted temperature management as opposed to no targeted temperature management for adults with OHCA with an initial shockable rhythm who remain unresponsive after ROSC (strong recommendation, low-quality evidence).
We suggest targeted temperature management as opposed to no targeted temperature management for adults with OHCA with an initial non-shockable rhythm who remain unresponsive after ROSC (weak recommendation, very low-quality evidence).
We suggest targeted temperature management as opposed to no targeted temperature management for adults with IHCA with any initial rhythm who remain unresponsive after ROSC (weak recommendation, very low-quality evidence).
We recommend selecting and maintaining a constant, target temperature between 32°C and 36°C for those patients in whom temperature control is used (strong recommendation, moderate-quality evidence).
Data collected
We collected data for all admissions to the Royal Lancaster Infirmary Intensive Care Unit coded via ICNARC as ‘cardiac arrest’ over the timeframe from May 15th 2020 until May 15th 2021 with the aim of evaluating adherence to targeted temperature management (TTM) interventions as recommended by ILCOR guidelines. In-hospital (IHCA) and out-of-hospital (OHCA) cardiac arrests were included.
We collected the following data points, as recommended by the RCoA Audit Recipe Book:
- RTX number
- Reason for admission to ICU
- Date & time of admission to ICU
- Date & time of cardiac arrest
- Location of arrest (OHCA/IHCA)
- Patient age and gender
- First rhythm
- Downtime; low-flow and no-flow time, estimated from case notes (minutes)
- Best Glasgow coma scale (GCS) following ROSC
- Core temperature measurements at 0, 6, 12, 18 and 24 hours (°C)
- Maximum and minimum core temperature in first 24 hours (°C)
- Target temperature documented
- Maximum blood glucose level at 4-24 hours (mmol/L)
- Target blood glucose documented
- Maximum pCO2 at 4-24 hours (kPa)
- Target pCO2 documented
- Temperature management methods used (cooling/warming devices & medication)
- Glasgow coma scale (GCS) at ICU discharge
- Outcome at ICU discharge
Inclusion characteristics
A total of 24 cases were identified over the period of 12 months. 4 cases were excluded for the following reasons:
- Rapid deterioration and death within hours of admission to ICU (n=3)
- Transfer to other facility shortly after admission (n=1)
Patient characteristics
| Alive (N=7) |
Dead (N=13) |
Overall (N=20) |
|
|---|---|---|---|
| Gender | |||
| Female | 2 (29 %) | 3 (23 %) | 5 (25 %) |
| Male | 5 (71 %) | 10 (77 %) | 15 (75 %) |
| Age | |||
| Mean (SD) | 63.4 (± 13.4) | 63.1 (± 16.8) | 63.2 (± 15.3) |
| OHCA | |||
| Yes | 7 (100 %) | 11 (85 %) | 18 (90 %) |
| No | 0 (0 %) | 2 (15 %) | 2 (10 %) |
| Rhythm | |||
| PEA | 1 (14 %) | 4 (31 %) | 5 (25 %) |
| Unknown | 1 (14 %) | 0 (0 %) | 1 (5 %) |
| VF | 5 (71 %) | 3 (23 %) | 8 (40 %) |
| Asystole | 0 (0 %) | 6 (46 %) | 6 (30 %) |
| Maximum temperature | |||
| Mean (SD) | 37.2 (± 0.621) | 37.3 (± 1.42) | 37.3 (± 1.18) |
| Minimum temperature | |||
| Mean (SD) | 33.7 (± 4.32) | 34.7 (± 1.01) | 34.4 (± 2.60) |
| Warmed | |||
| No | 5 (71 %) | 6 (46 %) | 11 (55 %) |
| Yes | 2 (29 %) | 7 (54 %) | 9 (45 %) |
| Maximum pCO2 | |||
| Mean (SD) | 6.93 (± 1.60) | 7.32 (± 2.11) | 7.18 (± 1.91) |
| Maximum blood glucose level | |||
| Mean (SD) | 10.0 (± 4.58) | 12.3 (± 6.71) | 11.5 (± 6.03) |
Admissions
Rhythms
| Rhythm | Frequency | Proportion |
|---|---|---|
| VF | 8 | 40.0% |
| Asystole | 6 | 30.0% |
| PEA | 5 | 25.0% |
| Unknown | 1 | 5.0% |
Temperature
Temperatures collected at 0, 6, 12, 18 and 24 hours from admission to ICU are plotted here.
Proportion of patients with maximum temperature > 36.0°C
## [1] 0.95Proportion of patients with maximum temperature > 37.0°C
## [1] 0.55Proportion of patients with maximum temperature > 37.7°C
## [1] 0.15Temperature management devices
A variety of devices were used to achieve targeted temperature management. The means of temperature management was frequently not documented on the chart. We did not extract data from the electronic record on the use of paracetamol (likely underestimate).
| Cooling method used | Frequency |
|---|---|
| Warmer | 9 |
| Not documented | 7 |
| CareCooler | 4 |
| Fan | 3 |
| Paracetamol | 3 |
| Blanketrol | 2 |
| Axillary ice packs | 1 |
| Cold compresses | 1 |
| Window open | 1 |
An interesting pattern was observed in the data, where in 45% of the reviewed cases patients were warmed, usually within the first 12 hours of admission. One patient (5%) was admitted following a hypothermic arrest, where this was appropriate.
Ventilation and glycaemic control
We analysed ventilation parameters and glycaemic control during the first 24 hours of admission. We sampled the maximum value for pCO2 and blood glucose 4-24 hours into the ICU admission. This was to allow for an initial stabilisation of parameters from admission blood gases.
We can see that adherence to glycaemic control is reasonable with only a small proportion of patients exceeding the usual target of 10 mmol/L beyond 4 hours following admission. Ventilatory control, however, can still be optimised, as a large proportion of patients seems to have poor CO2 clearance beyond the first 4 hours of admission. Many post-arrest patients have an increased PaCO2–etCO2 gradient; it is therefore important to quantify this on admission, comparing the arterial blood gas with the etCO2 readings and adjusting the etCO2 target accordingly during the first few hours of resuscitation.
Documentation of targets
Documentation of treatment targets varied. We extracted data where patients either had explciit documentation of temperature, glycaemic and/or ventilation targets documented. 5 patients had ‘neuroprotection’ documented, which would imply controlling the above parameters, but this was not counted in the following tables.
| Documented target temperature | Frequency | Proportion |
|---|---|---|
| No | 11 | 55.0% |
| Normothermia | 5 | 25.0% |
| <36 | 4 | 20.0% |
| Documented target glucose | Frequency | Proportion |
|---|---|---|
| No | 14 | 70% |
| Normoglycaemia | 3 | 15% |
| <10 | 1 | 5% |
| 4-10 | 1 | 5% |
| 4-12 | 1 | 5% |
| Documented target pCO2 | Frequency | Proportion |
|---|---|---|
| No | 14 | 70% |
| Normal | 2 | 10% |
| 4-5 | 1 | 5% |
| 4-6 | 1 | 5% |
| 4.5-5 | 1 | 5% |
| 4.5-5.5 | 1 | 5% |
Suggestions
Provided that we agree that strict normothermia currently has a sufficient evidence base for all comers, the following actionable suggestions can be made based on the locally observed data:
- No warming of patients. Use of active or passive warming should be avoided. Any temperatures above 33°C are to be tolerated and patients not actively warmed to 36°C, because we have a tendency to then overshoot.
- Temperature probe to be inserted at time of intubation or admission to ICU for all cardiac arrest patients. This will ensure stricter adherence to the TTM bundle. All patients presenting after cardiac arrest, regardless of first rhythm, should be kept normothermic, erring on the side of hypothermia.
- A copy of the post-arrest bundle to be printed out and placed on ICU chart on admission. This will ensure better adherence to the bundle and a culture of TTM. Documentation on targets is often vague (or missing) in admission clerking and on admission charts. A departmentally agreed set of targets would avoid ambiguity.
- All patients are to have the Blanketrol III placed on admission. This will encourage a proactive & preemptive approach to temperature control, as opposed to a reactive one. Furthermore, consistent use of the device will increase staff knowledge and skills. Patients should be actively cooled with the most effective available device to prevent any increase in temperature above 36°C.
Furthermore, consideration should be given to intravascular cooling devices. This should be a departmental decision as the device and consumables would need to be purchased separately.
Summary
In summary, our audit revealed general non-adherence to targeted temperature management, with a significant proportion of patients (55.0%) reaching core temperatures of 37.0°C or more during the first 24 hours of admission following cardiac arrest. A pragmatic set of inexpensive interventions is proposed to improve outcomes in the next cycle.
References
1. Bernard SA, Gray TW, Buist MD, et al. Treatment of comatose survivors of out-of-hospital cardiac arrest with induced hypothermia. New England Journal of Medicine. 2002;346(8):557-563. doi:10.1056/NEJMoa003289
2. HACA. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. New England Journal of Medicine. 2002;346(8):549-556. doi:10.1056/NEJMoa012689
3. Nielsen N, Wetterslev J, Cronberg T, et al. Targeted temperature management at 33°C versus 36°C after cardiac arrest. New England Journal of Medicine. 2013;369(23):2197-2206. doi:10.1056/NEJMoa1310519
4. Lascarrou J-B, Merdji H, Le Gouge A, et al. Targeted temperature management for cardiac arrest with nonshockable rhythm. New England Journal of Medicine. 2019;381(24):2327-2337. doi:10.1056/NEJMoa1906661
5. Dankiewicz J, Cronberg T, Lilja G, et al. Targeted hypothermia versus targeted normothermia after out-of-hospital cardiac arrest (ttm2): A randomized clinical trial-rationale and design. Am Heart J. 2019;217:23-31. doi:10.1016/j.ahj.2019.06.012
6. Andersen L, Berg K, Böttiger B, et al. Targeted temperature management after cardiac arrest. Statement by the advanced life support task force of the international liaison committee on resuscitation following publication of the hyperion trial. Published online 2019. https://www.ilcor.org/news/test-news-article-one