Selective use of cardiopulmonary bypass in trauma patients

The need for cardiopulmonary bypass (CPB) in the treatment of trauma patients is controversial, and not all level I trauma centers have CPB readily available. Our purpose was to review the selective use of CPB in the management of trauma victims at a level I trauma center in Los Angeles County. We reviewed the records of all patients for whom the CPB team was called in from 1994 to 2002. Perfusionists were present for the initial operative management of 24 patients, 22 (92%) of which were male. Twelve patients had penetrating and nine had blunt injuries, two were severely hypothermic, and the last suffered embolization of a bullet to the pulmonary artery. Overall survival was 75 per cent. Sixteen (67%) patients required CPB due to the life-threatening nature of their injuries and/or hemodynamic instability; 11 (69%) survived. The remaining 8 patients were operated on with the CPB team present but on standby; 7 (88%) survived. Cardiopulmonary bypass could be life-saving in select trauma patients with major chest injuries. Hypothermia, acidemia, and shock can be reversed earlier while allowing increased time to gain adequate exposure and perform quality repairs. Level I trauma centers should have CPB capabilities immediately available.     

Heparinless partial cardiopulmonary bypass for the repair of aortic trauma

OBJECTIVE: We hypothesized that partial cardiopulmonary bypass with a heparin-bonded system would be a technically simple, effective adjunct for reducing paraplegia during repair of traumatic aortic rupture. It avoids the risk of heparin, but, unlike left atrial-arterial bypass, it can heat, cool, oxygenate, and rapidly infuse volume if needed. METHODS: A retrospective review was conducted of patients admitted for aortic trauma from July 1994 to December 1999. Bypass consisted of femoral venous (right atrial) cannulation, a centrifugal pump, and an oxygenator-heater/cooler. Arterial return was to the femoral artery or distal aorta. The entire system was heparin-bonded and no systemic heparin was given. RESULTS: Heparin-bonded partial bypass was established in 50 patients (mean age 43 +/- 17 years). Crossclamp time was 32 +/- 11 minutes (range 14-70 minutes), mean flow 3.0 +/- 0.8 L/min, and bypass time 64 +/- 43 minutes. During repair, 58% of patients received volume through the system (mean 1.1 +/- 1.9 L). Core temperature rose slightly (35.9 degrees C +/- 0.7 degrees C to 36.3 degrees C +/- 0.8 degrees C). Three of the 15 patients who underwent percutaneous femoral arterial and venous cannulation concomitant with their angiograms had vessel injury, with one limb loss, and this procedure was discontinued. Thirty-five patients underwent percutaneous femoral vein and direct distal aortic cannulation without event. The mortality rate for patients supported by bypass was 10%, and all deaths were due to other injuries. There were no new cases of paraplegia and no worsening of intracranial or pulmonary injuries. CONCLUSIONS: Heparin-bonded bypass is technically simple to use and avoids the risk of anticoagulation. Paraplegia was avoided. The ability to correct hypothermia, oxygenate, and rapidly infuse volume may simplify management and improve outcomes.     

An oxygenator for cardiopulmonary bypass in the rat

A minature bubble oxygenator with integral heat exchange has been developed for high flow, normothermic, total cardiopulmonary bypass in rats: priming volume, 25 ml; flow rate, up to 260 ml/kg/min; survival after a 2-hr total bypass. It is thus possible to use rats for cardiothoracic surgical research and to make use of the many advantages of a standardized small-animal model, in particular for large-series work, in a field previously limited to large animals such as dogs, pigs, and calves.     

Heparin-coated cardiopulmonary bypass circuits reduce blood cell trauma. Experiments in the pig

Blood cell trauma and postoperative bleeding remain important problems in cardiopulmonary bypass (CPB). We compared heparin-coated with non-coated circuits in the pig. Twenty animals were perfused for 2 h at normothermia using membrane oxygenators (Bentley Bos 50). Two groups were studied. In the non-coated group (NC, n = 11) the CPB circuits used were without a heparin coating. This group had systemic heparinization of 400 IU/kg to maintain an ACT (activated clotting time) of over 400 s during CPB. In the coated group (C, n = 9), all surfaces exposed to blood in the CPB circuits were heparin-coated. This group had the heparin dose reduced to 25% (100 IU/kg) without further administration regardless of ACT. During CPB, group C displayed shorter ACT (per definition), higher platelet count, platelet adhesion and lower fibrinolysis and haemolysis (P less than 0.05) as compared to group NC. No thromboembolic events were detected during CPB. Three animals in group NC and 4 animals in group C were weaned from CPB and protaminized. Four hours postoperatively, the leucocyte consumption was two-fold greater and blood loss about four-fold greater in group NC as compared with group C (P less than 0.05). Perfusion with heparin-coated surfaces reduces blood cell trauma. The decreased postoperative blood loss observed in group C is probably explained by the reduced dosages of heparin and protamine.     

Microvascular permeability after cardiopulmonary bypass. An experimental study

Microvascular permeability is presumed to increase during cardiopulmonary bypass, but this has not been directly demonstrated. Method: Therefore, a controlled experimental study was performed in dogs in which the permeability ratio of the small intestinal microvasculature was determined. Shortly after 120 minutes of cardiopulmonary bypass (experimental group, n = 7) or a sham procedure (control group, n = 7), the superior mesenteric venous pressure was raised in a stepwise fashion until the intestinal lymph/plasma protein concentration stabilized at a minimum value. Data: Minimal lymph/plasma concentration ratio (permeability ratio) of the total proteins and each of six protein fractions was greater in dogs that had been on bypass than in control dogs (p = 0.01 for total proteins and less than 0.05 for five of the fractions). The variability in this regard was large in both groups, and in some animals subjected to bypass the permeability ratio was more than twice the maximum value for the control group. The increase in permeability ratio was greater for large molecules. Inferences: Cardiopulmonary bypass results in a variable increase in microvascular permeability. This results primarily from an increase in the size of large pores in the microvascular barrier.     

Technique for cardiopulmonary bypass in the goat.

The goat is an ideal animal for intracardiac surgical investigation. The animal is docile and easy to care for; it has an ideal heart size, a high cardiac output and a long life expectancy. The animal tolerates cardiopulmonary bypass well and does not require blood transfusion. Anoxic cardiac arrest is tolerated for up to 35 minutes. Initial experience in 36 animals with operations on the right side of the heart resulted in a 72% long-term survival.     

Coronary artery bypass without cardiopulmonary bypass.

The purpose of this article is twofold: to describe our technique for performing coronary artery bypass grafting without cardiopulmonary bypass (off pump) and to demonstrate that this operation is safe, in terms of mortality and certain indices of morbidity. Very little has been published in regard to off-bypass operations. From 1985 through 1990, 220 patients underwent operation off bypass; 220 on-pump controls were retrospectively matched for number of grafts, left ventricular function, and date of operation. Groups were compared in terms of mortality and ten indicators of morbidity. The same analysis was performed for ten subgroups. We found no statistically significant difference between groups in mortality (off pump, 1.4% [3/220]; on pump, 2.4% [5/220]), which held across all subgroups. Patients undergoing operation off pump required blood far less often (not transfused: off pump, 72.7% [160/220]; on pump, 54.6% [116/220]; p = 0.005 by Fisher's exact test), and the low output state occurred statistically less frequently off pump (off pump, 5.5% [12/220]; on-pump, 12.7% [28/220]; p = 0.01 by Fisher's exact test). Further research should be directed to which subgroups can be operated on to advantage off pump and which, if any, groups of patients should be confined to on-bypass operations.     

r-hirudin as anticoagulant for cardiopulmonary bypass.

A 68-year-old woman with unstable angina and an episode of ventricular fibrillation developed a persistent and recurrent rash due to heparin. Medical therapy was continued with danaproid. For cardiopulmonary bypass and coronary artery grafting, r-hirudin was used as the anticoagulant. There were no thrombotic or coagulopathic complications. There is still no ideal alternative to unfractionated heparin for anticoagulation for cardiopulmonary bypass. The use of r-hirudin was successful and we describe our anticoagulant strategy.     

Penetrating cardiac trauma. Experience with thirty-four patients in a hospital without cardiopulmonary bypass capability.

A review of thirty-four consecutive penetrating wounds of the heart is presented. Thirty-one patients were in shock at the time of admission, and fourteen had no obtainable blood pressure and were comatose or moribund. The weapon used, clinical status of the patient on arrival, size of the cardiac wound, and presence of associated injuries affected the mortality rate. Seven of the eight deaths were considered unpreventable due to clinical deterioration by the time of arrival. Clinical recognition of cardiac tamponade is stressed. Early open thoracotomy and closure of the cardiac wound is advocated as the preferred method of treating this injury. No patient was lost due to lack of cardiopulmonary bypass capability.     

Hemofiltration during cardiopulmonary bypass.

Several factors combine to facilitate the evolution towards heart and multi-organ failure following cardiac surgery. Some of these factors are related to pure cardiac aspects like the existence of a preoperative heart disease, the use of aortic cross clamping or performance of cardiotomy. Cardiopulmonary bypass (CPB) also plays an important role in the occurrence of postoperative organ dysfunctions by two principal means: firstly by inducing a profound hemodilution, which impairs oxygen transport through tissues. This phenomenon is pointed out in the postoperative period by the existence of increased transpulmonary O2 gradients, extravascular lung water volume and subsequent impairments of O2 transport. Secondly CPB is deleterious by triggering an important inflammatory reaction. This reaction is largely related to the ratio of the circuit area to the patient's body surface area and is therefore maximal in children. It has been widely demonstrated that the very early paths of this reaction imply several humoral factors including kinins, coagulation factor-XII and complement fragments. The activation of these factors is self-amplified and triggers both expression and release of numerous mediators by endothelial cells and leukocytes. Finally, these mediators are responsible for the well described "post-bypass syndrome" which is, from a clinical viewpoint, very close to hyperkinetic septic shocks. Several methods have been proposed to reduce the deleterious effects of both cardiac surgery and CPB. The older one is hypothermia that considerably reduces the triggering of the inflammatory mediators network. Heparin-coated circuits may also reduce this reaction to some extent. Hemofiltration has been introduced in the 90's in CPB management. Because of its very high tolerance in patients with compromised circulatory status this technique was already used in the postoperative period to treat patients with acute renal failure. Initially hemofiltration was intended to correct the accumulation of extravascular water during or immediately following the surgical procedure. Nevertheless several of its "side-effects" appeared to be useful like reduction of postoperative blood loss and immediate hemodynamics improvement. Several studies attempted to point out the mechanism of action of hemofiltration and although removal of inflammatory mediator occurs, there is currently no proofs that this removal is the actual mechanism by which this technique acts. At the early beginning of the use of its utilization hemofiltration during cardiac surgery aimed either to concentrate blood at the end of the procedure or to rapidly restore a normal fluid and electrolytes balance. Today some new implementations of this technique are proposed either to reduce the triggering of the inflammatory reaction to CPB or to reduce the immediate postoperative drug support.     

Traumatic cardiogenic shock due to massive air embolism. A possible role for cardiopulmonary bypass.

Systemic arterial embolism is a potentially lethal complication of bronchopulmonary venous fistula in trauma patients with blunt chest trauma or isolated penetrating lung injury on positive pressure ventilation. A high index of suspicion, early diagnosis and management in specialized centres are keys to a successful outcome.