Prehospital therapeutic hypothermia induced with cold infusions improves haemodynamic stability in nonshockable cardiac arrest patients

Introduction

Recent studies report an increase of asystole and pulseless electrical activity (PEA) as the first monitored cardiac arrest rhythms after arrival of the Emergency Medical Services [1]. The asystolic patients presumably undergo ischaemia for a longer time and may benefit from treatment reducing hypoxic brain injury. Therapeutic hypothermia (TH) has expanded into prehospital care to be initiated as soon as possible. Rapid cold crystalloid infusion is the most frequent method; however, severe haemodynamic instability is its contraindication. The aim of the study was to assess the adverse effects of prehospital volume expansion in patients with initial nonshockable rhythms when used in a setting with only restricted cardiovascular monitoring.

Methods

The nonshockable patients enrolled in a prospective nonrandomized PRE-COOL trial (PRE-hospital COOLing in cardiac arrest patients) were rapidly administered cold normal saline (5 to 30 ml/kg) intravenously and analysed for body temperature, haemodynamic variables (blood pressure, heart rate, shock index), incidence of circulatory complications (recurrence of cardiac arrest, pulmonary oedema), and outcome. Hypothermic patients (group A, n = 19) were compared with matched historic controls (group B, n = 22).

Results

In treatment group A, 1,021 ± 526 ml (13.2 ± 6.3 ml/kg) of 4°C cold normal saline was administered before hospital admission. Body temperature decreased by 1.32 ± 0.71°C until arrival at hospital (calculated rate 1.08 ± 0.44°C/30 minutes). The incidence of hypotension requiring vasopressors (noradrenaline or dopamine) significantly decreased in patients given cold intravenous fluids compared with control group B: 31.6% vs 63.6% (P = 0.04). No patient developed pulmonary oedema within 24 hours. Recurrence of cardiac arrest was comparable in both groups (3/19 vs 3/22), shock index at hospital arrival was 0.92 vs 0.97 (P = 0.78), and favorable outcome (cerebral performance category 1 or 2) 26.3% vs 13.6% (P = 0.31).

Conclusions

The early prehospital administration of cold infusions is safe and contributes to haemodynamic optimization in patients resuscitated from nonshockable rhythms. Incidence of hypotension requiring vasopressors was significantly reduced in the treated group. No pulmonary oedema was observed.