A method for identifying mechanisms of neurologic injury from cardiac surgery.

BACKGROUND: A method for linking discrete surgical and perfusion-related processes of care with cerebral emboli, cerebral oxyhemoglobin desaturation, and hemodynamic changes may offer opportunities for reducing overall neurologic injury for patients undergoing cardiac surgery. METHODS: An intensive intraoperative neurologic and physiologic monitoring approach was developed and implemented. Mechanisms likely to produce embolic (cerebral emboli), hypoperfusion (oxyhemoglobin desaturation), and hypotensive (hemodynamic changes) neurologic injuries were monitored and synchronized with the occurrence of surgical and perfusion clinical events/techniques using a case video. RESULTS: The system was tested among 32 cardiac surgery patients. Emboli were measured in the cerebral arteries and outflow of the cardiopulmonary bypass circuit among nearly 75% and 85% of patients, respectively. Oxyhemoglobin desaturation was measured among nearly 70% of patients. Hemodynamic information was recorded in 100% of patients. CONCLUSIONS: We developed and successfully implemented a method for detailed real-time associations between processes of clinical care and precursors of neurologic injury. Knowledge of this linkage will result in the redesign of clinical care to reduce a patient's risk of neurologic injury.

Detection and elimination of microemboli related to cardiopulmonary bypass.

BACKGROUND: Neurobehavioral impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass (CPB) are a principal mechanism of cognitive injury. The aim of this work was to study the occurrence of cerebral embolism during CPB and to evaluate the effectiveness of evidence-based CPB circuit component and process changes on the exposure of the patient to emboli. METHODS AND RESULTS: M-Mode Doppler was used to detect emboli in the inflow and outflow of cardiopulmonary circuit and in the right and left middle cerebral arteries. Doppler signals were merged into a single display to allow real-time associations between discrete clinical techniques and emboli detection. One hundred sixty-nine isolated coronary artery bypass grafting (CABG) patients were studied between 2002 and 2008. There was no statistical difference in median microemboli detected in the inflow of the CPB circuit, (Phase I, 931; Phase II, 1214; Phase III, 1253; Phase IV, 1125; F [3,158]=0.8, P=0.96). Significant changes occurred in median microemboli detected in the outflow of the CPB circuit across phases, (Phase I, 702; Phase II, 572; Phase III, 596; Phase IV, 85; F [3,157]=13.1, P<0.001). Significant changes also occurred in median microemboli detected in the brain across phases, (Phase I, 604; Phase II, 429; Phase III, 407; Phase IV, 138; F [3,153]=14.4, P<0.001). Changes in the cardiopulmonary bypass circuit were associated with an 87.9% (702 versus 85) reduction in median microemboli in the outflow of the CPB circuit (P<0.001), and a 77.2% (604 versus 146) reduction in microemboli in the brain (P<0.001). CONCLUSIONS: Changes in CPB techniques and circuit components, including filter size and type of pump, resulted in a reduction in more than 75% of cerebral microemboli.

Repair of hypoplastic left heart syndrome of a 4.25-kg Jehovah's witness.

The care of patients who refuse homologous transfusions has challenged cardiac surgery teams to refine blood conservation techniques and question standard transfusion practices. We cared for a newborn child with hypoplastic left heart syndrome (HLHS) whose parents refused to give consent to care for the child that involved the transfusion of homologous blood. A Norwood Stage I procedure was planned with the understanding that transfusions would be avoided, if possible. A court order was obtained that specified the conditions under which the attending physicians would transfuse the newborn. The birth weight of the patient was 4.25 kg. A low prime cardiopulmonary bypass (CPB) circuit and aggressive blood conservation techniques that included modified ultrafiltration (MUF) allowed the completion of the repair and CPB portion of the operation without the use of blood. The lowest hematocrit during CPB was 20%. After an unsuccessful attempt to separate from CPB, blood was transfused. Recovery was consistent for HLHS patients following Norwood Stage I. However, at 1 month postoperatively, the patient did require a shunt reduction for pulmonary overcirculation. Norwood Stage II repair was completed at age 4 months without donor blood. The key to a successful outcome is a well-thoughtout plan by the surgeon, anesthesiologist and perfusionist. This plan should include careful monitoring of the patient's oxygenation and cardiovascular status.

Highest core temperature during cardiopulmonary bypass and rate of mediastinitis.

Temperature control during cardiopulmonary bypass (CPB) may be related to rates of bacterial infection. We assessed the relationship between highest core temperature during CPB and rates of mediastinitis in 6955 consecutive isolated coronary artery bypass graft (CABG) procedures in northern New England. The overall rate of mediastinitis was 1.1%. The association between highest core temperature and mediastinitis was different for diabetics than for nondiabetics. A multivariate model showed that there was a significant interaction between diabetes and temperature in their association with mediastinitis (p=0.015). Diabetic patients showed higher rates of mediastinitis as highest core temperature increased, from 0.7% in the < or = 37 degrees C group to 3.3% in the > or = 38 degrees C group (p(trend) = 0.002). Adjusted rates were similar. Nondiabetic patients did not show this trend (p(trend) = 0.998). Among diabetic patients, a peak core body temperature > 37.9 degrees C during CPB is a significant risk factor for development of mediastinitis. Avoidance of higher temperatures during CPB may lower the risk of mediastinitis for diabetic patients undergoing CABG surgery.

Lowest core body temperature and adverse outcomes associated with coronary artery bypass surgery.

To examine the effect of lowest core body temperature on adverse outcomes associated with coronary artery bypass graft (CABG) surgery, data were collected on 7134 isolated CABG procedures carried out in New England from 1997 to 2000. Excluded from the analysis were patients with pump times < 60 and > 120 min and those operated upon using continuous warm cardioplegia. Data for lowest core temperature were divided into quartiles for analysis ( < 31.4 degrees C, 31.5-33.1 degrees C, 33.2-34.3 degrees C, and 2 34.4 degrees C). Patients with lower core body temperature on cardiopulmonary bypass (CPB) had higher in-hospital mortality rates. Crude mortality rates were 2.9% in the < or = 31.4 degrees C group, 2.1% in the 31.5-33.1 degrees C group, 1.3% in the 33.2-34.3 degrees C group and 1.2% in the > or = 34.4 degrees C group. The trend toward higher mortality as core temperature decreased was statistically significant (P(trend) < 0.001). Adjustment for differences in patient and disease characteristics did not significantly change the results and the test of trend remained significant (p < 0.001). Rates of perioperative stroke were somewhat lower in the colder groups. Rates in the two colder groups were 0.9% compared with 1.6% and 1.4% in the warmer groups (P(trend) = 0.082). This remained a marginal but significant trend after adjustment for possible confounding factors (p = 0.044). Low core body temperatures on CPB are associated with higher rates of in-hospital mortality among isolated CABG patients. Rates of intra- or postoperative use of an intra-aortic balloon pump are also higher with lower core temperatures. We concluded that temperature management strategy during CABG surgery has an important effect on patient outcomes.