efficacy of a hydrogel pad cooling device for induction, maintenance, and rewarming during mild...

Efficacy of a Hydrogel Pad Cooling Device for induction, maintenance, and rewarming during mild hypothermia treatment in the post cardiac arrest and neuro patient populations

Mission Hospital – Mission Viejo CA1 UCLA Los Angeles CA2

Mary Kay Bader RN1, Teresa Wavra RN1, Robert McCary RN2, Joy Toyama MS2 , George Schiffman MD1, and Jon Cline MD1

Conclusion:Patients undergoing mild hypothermia were rapidly cooled to the goal temp of 32-34 °C within 2.5-2.8 hours using a hydrogel pad surface cooling device. Overshooting the target temperature occurred in 3 of the 40 patients. Rewarming to 37°C was well controlled in both populations. There were several patient records that had incomplete clinical data therefore they were not included in the statistical analysis. Overall, the organizations cooling method and protocol were able to deliver a well controlled hypothermia treatment while minimizing overshooting of the target temperature.

Results:28 post cardiac arrest patients and 28 neuro patients had orders to induce mild hypothermia starting in September 2006. 16 patients were excluded due to: a) target temperature ordered to 35°C [6 neuro], b) no available medical record [3], c) hemodynamic instability leading to aborted procedures [3 cardiac], d) poor documentation [3] with inability to obtain accurate data, and e)1st documented temperature of 33°C with incomplete documentation [3]). Data from 40 patients were included for analysis. In the neuro patients, mean values were 43.1 (age), 23.59 (BSA) and 1.866 (BMI). In the cardiac patients, mean values were 58.7 (age), 27.675 (BSA), and 2.024 (BMI). Induction cooling time to target of 33°C was 2.575 hours with a mean cooling rate of 1.43°C/hr for the neuro patients and 2.8 hours with a mean cooling rate of 1.2°C/hr for the cardiac patients. Using the Pearson Correlation, a significant association between the degree/hr decrease for both BMI and BSA was determined: BMI p-value= 0.40568; BSA p-value= 0.45674 at a significant level of p=0.05. Overshooting the lower temperature threshold of 32°C occurred in 0 of 20 neuro patients and 3 of 20 cardiac patients with the lowest temperature recorded at 31.5°C. Rewarming rates were well controlled for both populations (0.25°C/hour in cardiac patients/spinal injury and 0.05°C/hour in brain injury patients).

Introduction:The implementation of mild hypothermia (32-34°C) in post cardiac arrest (HACA) ameliorates the hypoxic/anoxic damage in the brain. Mild hypothermia has been deployed in neuro patients with refractory increased intracranial pressure, severe vasospasm, stroke, and injury to the brain/spine. The challenge in implementing this therapy is using a cooling system that rapidly induces the target temperature of 32-34°C without overshooting the temperature, maintaining the target temperature, and rewarming slowly to reduce rebound cerebral swelling and minimize the electrolyte shifts that occur as patients return to 37°C. This study examined two patient populations at one community hospital where mild hypothermia was used to reduce neurologic injury post cardiac arrest and in critical neuro patients using a hydrogel pad surface cooling system.

Methods:A retrospective review of all patients treated with mild hypothermia post-cardiac arrest or for severe neurologic injury over the last three years was conducted. An analysis of the medical records was done. Data abstracted included age, body surface area (BSA), and body mass index (BMI) as well as bladder temperatures obtained every 15 to 60 minutes during the hypothermia period. Induction time (defined as the active rate of cooling from start to target temperature), overshooting target temperature (defined as temperatures below 32°C) and control of rewarming at the prescribed rate were assessed.

HACA Patient Population Individual Temperature

Curves

Variable Mean Std Error N

Age

Sex

Ht__cm_

Wt__kg_

BMI__kg_m2_

BSA__m2_

Temp_at_start_of_Induction__fole

Post_induction_Foley_Temp__C_

time_hrs

deg_hr

43.1500000

1.3684211

174.2520000

72.2250000

23.5900000

1.8660000

36.2800000

33.1150000

2.5750000

1.4322604

3.9975486

0.1136972

1.6426387

3.4423361

0.8568271

0.0534711

0.2025625

0.0264326

0.4144194

0.1062931

20

20

20

20

20

20

20

20

20

20

Variable AnalysisNeuro Population HACA Population

Pearson Correlation Coefficients, N = 20 one-sided pvalue under H0: Rho=0

Age BMI _ _ kg_ m2_ BSA_ _ m2_ time_ hrs deg_ hr

Age Age

1.00000

-0.10285 0.33305

0.00520 0.49135

0.00441 0.49265

0.07214 0.38125

BMI _ _ kg_ m2_ BMI (kg/ m2)

-0.10285 0.33305

1.00000

0.91036 <.0001

0.40568 0.038

-0.51840 0.0096

BSA_ _ m2_ BSA (m2)

0.00520 0.49135

0.91036 <.0001

1.00000

0.45674 0.02145

-0.60547 0.00235

time_ hrs

0.00441 0.49265

0.40568 0.038

0.45674 0.02145

1.00000

-0.62497 0.0016

deg_ hr

0.07214 0.38125

-0.51840 0.0096

-0.60547 0.00235

-0.62497 0.0016

1.00000

Pearson Correlation Coefficients, N = 20 one-sided pvalue under H0: Rho=0

Age BMI_ _ kg_ m2_ BSA_ _ m2_ time_ hrs deg_ hr

Age Age

1.00000

0.29880 0.10035

-0.22271 0.17265

-0.23743 0.15675

0.10128 0.33545

BMI_ _ kg_ m2_ BMI (kg/ m2)

0.29880 0.10035

1.00000

0.23937 0.1547

0.29946 0.0998

-0.25187 0.14205

BSA_ _ m2_ BSA (m2)

-0.22271 0.17265

0.23937 0.1547

1.00000

0.44290 0.02525

-0.73090 0.00015

time_ hrs

-0.23743 0.15675

0.29946 0.0998

0.44290 0.02525

1.00000

-0.64195 0.00115

deg_ hr

0.10128 0.33545

-0.25187 0.14205

-0.73090 0.00015

-0.64195 0.00115

1.00000

Statistical AnalysisNeuro Population HACA Population

Badermk@aol.com Teresa.Wavra@stjoe.org

Variable Mean Std Error N

Age

Sex

Ht__cm_

Wt__kg_

BMI__kg_m2_

BSA__m2_

Temp_at_start_of_Induction__fole

Post_induction_Foley_Temp__C_

time_hrs

deg_hr

58.2000000

1.2500000

176.5500000

86.0580000

27.6750000

2.0240000

36.0750000

33.0000000

2.8000000

1.2011550

3.0971974

0.0993399

1.8020529

2.8007848

0.7780162

0.0521001

0.2237098

0.0369922

0.2530082

0.0934018

20

20

20

20

20

20

20

20

20

20

Neuro Patient Population Individual Temperature Curves

Poster 353