This is an animal study, rather than a human study, but it has fewer disadvantages than the usual animal studies of medical cardiac arrest. Animals do not develop the comorbidities that humans do, but have artificially created heart attacks, rather than by the development of actual heart disease. In studying trauma, this is less of a problem, since trauma is artificially created. This study is much more representative of penetrating injuries with a low velocity objects, than blunt force trauma, or penetrating injury with a high velocity object.
Are we really killing trauma patients with our chest compressions?
Maybe. This is one small study (39 pigs), but it does raise questions about the ways we can minimize the harm we cause.
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CCC were associated with increased mortality and compromised haemodynamics compared to intravenous fluid resuscitation. Whole blood resuscitation was better than saline.[1]
A soft tissue injury was created, with 3 shots to the right thigh using a captive bolt (Cash Special, Accles and Shelvoke, Sutton Coldfield, UK). Two minutes later animals underwent a controlled haemorrhage (30% blood volume) at an exponentially reducing rate as previously described12 until the mean arterial blood pressure (MAP) was 45 mmHg. Blood was collected into CPD (citrate phosphate dextrose) and stored at room temperature until required for later transfusion.[1]
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This study, conducted in an animal model of haemorrhage-induced traumatic cardiac arrest, has demonstrated that chest compressions confer no benefit over fluid resuscitation alone, and blood should be the fluid therapy of choice.[1]That seems to be concluding too much, since this is just one study, but it does reinforce the results of other, similar studies. We should study the outcomes in humans, since there does appear to be equipoise. There never was a physiological justification for chest compressions in traumatic cardiac arrest which appears to be due to hemorrhage. Now there is more evidence that chest compressions produce more harm than benefit in traumatic cardiac arrest which appears to be due to hemorrhage.
One study using a baboon traumatic cardiac arrest model found that the improvements in haemodynamics seen with chest compressions for normovolaemic cardiac arrest were not reproduced in hypovolaemic arrest.14 The authors suggested that CCC should not delay correction of the underlying deficit causing TCA, but the study was undertaken in only three animals, perhaps limiting its clinical relevance. A more recent study using a canine model of pulseless electrical activity in TCA found no benefit of chest compressions over fluid therapy alone or fluid combined with chest compressions; in fact the chest compression only group had worse survival, base deficit and ejection fraction.15 The authors concluded that further research was required to determine whether CPR has a role for the patient in haemorrhagic shock.[1]Most important is that the outcome is ROSC (Return Of Spontaneous Circulation), not return to normal neurological function. Since these are pigs, even the appearance of normal neurological function may not mean anything in humans. Still, the treatment is not evidence-based, so there does not appear to be a good reason to prefer to continue using compressions for traumatic cardiac arrest which appears to be due to hemorrhage. Here in America, we are unlikely to do the research, because we are more concerned with appearances than with improving outcomes for patients. Maybe somebody in Britain or Australia will have to demonstrate some responsibility, so we can stop using chest compressions to kill trauma patients. Footnotes: [1] Closed chest compressions reduce survival in an animal model of haemorrhage-induced traumatic cardiac arrest. Watts S, Smith JE, Gwyther R, Kirkman E. Resuscitation. 2019 May 9;140:37-42. doi: 10.1016/j.resuscitation.2019.04.048. [Epub ahead of print] PMID: 31077754 Free Full Text from Resuscitation .
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