Background: Accumulating evidence indicates that target temperature management (TTM) is beneficial in patients resuscitated after cardiac arrest since it appears to improve neurological outcome. However, the optimal cooling method (surface vs. intravascular) has not yet been specified. Substantial heart disease is present in most of these patients and therefore haemodynamic effects of cooling need to be considered very carefully. We analysed the haemodynamic response to TTM in patients treated with surface versus intravascular cooling following out-of-hospital cardiac arrest.
Methods and results: In this observational study 63 consecutive subjects presenting to the hospital after successful resuscitation following of out-of-hospital cardiac arrest received an intravascular (40 patients) or external cooling device (23 patients) to induce TTM. While with intravascular cooling the target temperature of 33 degrees C was reached after 159 minutes, the minimum temperature achieved with surface cooling was about 35 degrees C after 437 minutes. Haemodynamic parameters were recorded in a 4-hour rhythm for the first 12 hours after induction of hypothermia. Generally, TTM of 33 degrees C resulted in a higher systemic vascular resistance index (749 vs. 467 dyn*sec/cms/m2; P= 0.04) but also in a marked reduction of heart rate (67.70 vs. 100.00 bpm; P < 0.001), a higher mixed venous oxygen saturation (76 vs. 68%; P = 0.016), and a higher stroke volume index (45 vs. 33 mI/m2; P = 0.036). TTM additionally resulted in a higher cardiac power index (0.55 vs. 0.46 Watt/m2; P = 0.024).
Conclusion: TTM of 33 degrees C compared to 35 degrees C exerts beneficial haemodynamic effects and might be viewed as an adjunct inotropic therapy avoiding the undesired side effects of vasoactive substances.