Preoperative cerebral hypoperfusion in the left, not in the right, hemisphere is associated with cognitive decline after cardiac surgery.

OBJECTIVE: Postoperative cognitive decline (POCD) is a frequent complication after cardiac surgery. Although intraoperative events are risk factors for POCD, the role played by preoperative hypoperfusion in cognitive decline has not yet been investigated. It is also unknown whether the impact of preoperative hypoperfusion in the left or right middle cerebral arteries (MCAs) can differentially account for POCD. The main aims of this study were to investigate whether preoperative cerebral hypoperfusion was associated with early POCD and whether lateralized hypoperfusion would differentially affect POCD in patients after cardiac surgery. METHODS: Bilateral MCA continuous transcranial Doppler (TCD) sonography was preoperatively performed at rest in 31 right-handed patients who underwent cardiac surgery to detect cerebral blood flow (CBF) velocity. All patients completed a neuropsychological evaluation to assess attention, short-term memory, working memory, and psychomotor function before surgery and at discharge. POCD was defined using the standard deviation method. Logistic regression was used to investigate the association between hypoperfusion and POCD, controlling for common preoperative risk factors. RESULTS: Fourteen patients (45%) exhibited POCD. Cerebral hypoperfusion in the left MCA selectively predicted the incidence of POCD (odds ratio = 0.90, p < .02), whereas CBF velocity in the right MCA was unrelated to POCD (odds ratio = 1.07, p = .39). CONCLUSIONS: Patients who underwent cardiac surgery with reduced CBF velocity in the left MCA preoperatively are at greater risk for POCD. Left cerebral hypoperfusion may also represent an independent predictor of POCD in these patients. TCD evaluation may have substantial clinical benefits for the detection of patients at high risk of POCD after cardiac surgery.

Intraoperative neurophysiological monitoring of the afferent pain pathway in cardiac surgery patients.

OBJECTIVE: No specific and sensitive method is available in routine clinical practice to detect pain in anaesthetised patients during surgery. The main aim of the present study was to investigate whether intraoperative somatosensory evoked potentials, the bispectral index, electroencephalogram, blood pressure and heart rate change during painful stimulation in cardiac surgery patients. METHODS: After induction of anaesthesia, 37 cardiac surgery patients were subjected to increasing electrical stimulation of both the median nerves and subsequent intravenous infusion of remifentanil to suppress this painful stimulation. RESULTS: The higher intensities of electrical stimulation significantly modified the cortical evoked potentials, the electroencephalogram spectral edge frequency and blood pressure. We also observed the appearance of a middle-latency component in the somatosensory evoked cortical potentials between 60 and 70 ms. These neurophysiological and clinical responses were significantly reduced by remifentanil administration. CONCLUSIONS: The data suggest that somatosensory evoked potentials might be used to detect and monitor painful stimulation during surgery, unlike the bispectral index, which does not seem to be highly sensitive to intraoperative pain. SIGNIFICANCE: Measurement of intraoperative somatosensory evoked potentials provides a specific and sensitive method to monitor the afferent pain pathway in anaesthetised patients.

Microembolic signals and strategy to prevent gas embolism during extracorporeal membrane oxygenation.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) supplies systemic blood perfusion and gas exchange in patients with cardiopulmonary failure. The current literature lacks of papers reporting the possible risks of microembolism among the complications of this treatment.In this study we present our preliminary experience on brain blood flow velocity and emboli detection through the transcranial Doppler monitoring during ECMO. METHODS: Six patients suffering of heart failure, four after cardiac surgery and two after cardiopulmonary resuscitation were treated with ECMO and submitted to transcranial doppler monitoring to accomplish the neurophysiological evaluation for coma.Four patients had a full extracorporeal flow supply while in the remaining two patients the support was maintained 50% in respect to normal demand.All patients had a bilateral transcranial brain blood flow monitoring for 15 minutes during the first clinical evaluation. RESULTS: Microembolic signals were detected only in patients with the full extracorporeal blood flow supply due to air embolism. CONCLUSIONS: We established that the microembolic load depends on gas embolism from the central venous lines and on the level of blood flow assistance.The gas microemboli that enter in the blood circulation and in the extracorporeal circuits are not removed by the membrane oxygenator filter.Maximum care is required in drugs and fluid infusion of this kind of patients as a possible source of microemboli. This harmful phenomenon may be overcome adding an air filter device to the intravenous catheters.