Myocardial effects of pericardial tamponade

Emergency thoracotomy in thoracic trauma-a review

Thoracic trauma is one of the leading causes of death in all age groups and accounts for 25-50% of all traumatic injuries. While the majority of patients with thoracic trauma can be managed conservatively, a small but significant number requires emergency thoracotomy as part of their initial resuscitation. The procedure has been advocated for evacuation of pericardial tamponade, direct control of intrathoracic haemorrhage, control of massive air-embolism, open cardiac massage and cross-clamping of the descending aorta. Emergency thoracotomy can be defined as thoracotomy "occurring either immediately at the site of injury, or in the emergency department or operating room as an integral part of the initial resuscitation process". Following emergency thoracotomy, the overall survival rates for penetrating thoracic trauma are around 9-12% but have been reported to be as high as 38%. The survival rate for blunt trauma is approximately 1-2%. The decision to perform emergency thoracotomy involves careful evaluation of the scientific, ethical, social and economic issues. This article aims to provide a review of the current literature and to outline the pathophysiological features, technical manoeuvres and selective indications for emergency thoracotomy as a component of the initial resuscitation of trauma victims with thoracic injury.

Efficacy of intravascular volume resuscitation in dogs with acute cardiac tamponade

Whether cardiac tamponade causes myocardial ischemia and whether volume resuscitation can improve coronary perfusion pressure and myocardial blood flow were studied by hemodynamic responses to three blood infusions of 15 ml/kg in dogs with left ventricular hypovolemia produced by cardiac tamponade (N = 10) or hemorrhage (N = 10). Coronary perfusion pressure decreased to 37 +/- 2 mm Hg with tamponade and 39 +/- 1 mm Hg with hemorrhage, causing significant blood flow decreases in both ventricles. Myocardial oxygen extraction increased significantly in both groups without affecting lactate extraction. Volume resuscitation after hemorrhage progressively restored hemodynamic variables to baseline values. Volume resuscitation after tamponade did not increase stroke volume, whereas it increased coronary sinus pressure to 19.2 +/- 1.0 mm Hg (p less than 0.05). Coronary perfusion pressure increased to 53 +/- 5 mm Hg following the first infusion (p less than 0.05), but exhibited no further improvement. Tamponade did not produce myocardial ischemia. Coronary perfusion pressure and blood flow were not restored to baseline values with volume resuscitation since coronary sinus pressure rose incrementally with each volume infusion.

Cardiac tamponade

Cardiac tamponade is an insidious and often fatal complication which can occur on any service, in many diseases, and at any age. The increasing pressure within the pericardium prevents ventricular filling and depresses cardiac output, coronary and systemic perfusion, and venous return. Compensatory mechanisms may protect the patient for some time, but prompt diagnosis and rapid decompression are usually required and must be followed by meticulous evaluation and treatment of the underlying disease.