The role of cerebral hyperperfusion in postoperative neurologic dysfunction after left ventricular assist device implantation for end-stage heart failure

Delirium Development After Lung Transplantation: An Intraoperative Assessment

BACKGROUND

This study aimed to evaluate the relationship between intraoperative hemodynamic and laboratory parameters with postoperative delirium development after lung transplantation.

METHODS

A total of 77 patients who underwent lung transplantation in a single center were included in the study. Demographic and clinical data recorded at critical intraoperative stages (after induction [T1], after bilateral lungs are dissected [T2], while the patient is ventilated for 1 lung [T3], while the unilateral transplanted lung is ventilated [T4], while bilateral transplanted lungs are ventilated [T5], and after the thorax is closed [T6]), postoperative complications, mechanical ventilation duration, intensive care, and hospitalization durations and mortality rates were recorded.

RESULTS

A total of 83.1% of the 77 patients were male, and the mean (SD) age was 47.56 (12.95) years. The mean body mass index (calculated as weight in kilograms divided by height in meters squared) was 23.30 (3.99), and the median Charles Comorbidity Index (CCI) was 1. The diagnosis of 36.4% of the patients was chronic obstructive pulmonary disease. Delirium was seen in 51.9% of the patients. Age, CCI, intraoperative mean arterial pressure changes, lactate levels, mechanical ventilation duration, and hospital stay were all associated with delirium development.

CONCLUSION

Age, CCI, duration of mechanical ventilation, and hospital stay were independent predictors of postoperative delirium development. We believe that our study will be a guide for future prospective randomized controlled studies.

Effects of Acute Pump Speed Changes on Cerebral Hemodynamics in Patients With an Implantable Continuous-Flow Left Ventricular Assist Devices

Mechanical circulatory support (MCS) with an implantable left ventricular assist device (LVAD) is an established therapeutic option for advanced heart failure. Most of the currently used LVADs generate a continuous stream of blood that decreases arterial pulse pressure. This study investigated whether a change of the pulse pressure during different pump speed settings would affect cerebral autoregulation and thereby affect cerebral blood flow (CBF). The study included 21 haemodynamically stable outpatients with a continuous-flow LVAD (HeartMate II, Abbott, USA) implanted a median of 6 months before the study (interquartile range 3 to 14 months). Arterial blood pressure (measured by finger plethysmography) was recorded simultaneously with CBF (measured by transcranial Doppler ultrasound) during baseline pump speed (8900 rpm [IQR 8800; 9200]) and during minimum and maximum tolerated pump speeds (8000 rpm [IQR 8000; 8200] and 9800 rpm [IQR 9800; 10 000]). An increase in LVAD pump speed by 800 rpm [IQR 800; 1000] from the baseline lead to a significant decrease in arterial pulse pressure and cerebral blood flow pulsatility (relative change -24% and -32%, both p < 0.01), but it did not affect mean arterial pressure and mean CBF velocity (relative change 1% and -1.7%, p = 0.1 and 0.7). In stable patients with a continuous-flow LVAD, changes of pump speed settings within a clinically used range did not impair static cerebral autoregulation and cerebral blood flow.

Effects of continuous-flow left ventricular assist devices on cerebral hemodynamics

Continuous-flow left ventricular assist devices (LVADs) reduce peak systolic flow, increase diastolic flow, and eliminate pulsatility of circulation. Altered blood flow may lead to a change in end-organ perfusion. Analysis of the flow dynamics of the arteries of end organs, such as the brain, may indicate whether an organ is perfused sufficiently. The aim of this study is to evaluate and identify the flow pattern changes of carotid (CA) and middle cerebral arteries (MCA) in LVAD patients and to compare with heart failure patients and healthy volunteers. Eighty-nine individuals were included in this cross-sectional study. Participants were divided into three groups: LVAD patients (n = 31), heart failure patients (n = 26), and healthy volunteers (n = 27). Carotid and transcranial Doppler ultrasonography were performed for all study groups for peak systolic velocity (PSV), end-diastolic velocity (EDV), pulsatility (PI), and resistive (RI) indices of CA and MCA. Flow dynamics were compared between the groups. Doppler ultrasonographic data were analyzed at a median 12 (3-47) months after LVAD implantation. CA-PSV was lower in LVAD group compared with the other two groups (P < .001), MCA-PSV of LVAD and heart failure groups were similar and lower than healthy volunteers (P < .05). The highest values for CA-EDV were found in the LVAD group (P < .05). MCA-EDV values were found to be lowest in heart failure group (P < .05). For PI and RI, in all CA and MCA, the LVAD group had lower indices compared with the other two groups (P < .001). In addition, MCA flow analysis in patients with LVADs was identified for the first time with this study.

Does cognition improve following LVAD implantation?

BACKGROUND

Studies of cognition after LVAD surgery have produced mixed results. To explore whether cognition would improve, decline, or remain stable after LVAD surgery, we examined cognition before and 1- and 3-months after LVAD surgery. Patients with post-surgical stroke were excluded.

METHODS

28 subjects (mean age = 54.31 ± 12 years) comprised an observational case series from the DuraHeart LVAS device® trial. Cognitive testing was performed at baseline, 1-month, and 3-month post-surgery, and included tests of attention, memory, language, visualmotor speed (TMT) and visualconstruction.

RESULTS

No difference in cognition was found between baseline and 1-month exams (means z score improvement = 0.06, p = 0.43) but cognition improved significantly between baseline and 3-month exams (mean z score improvement = 0.34, p < 0.00001). Examination of individual test scores found, after correction for multiple comparisons, only the TMT variable was significantly different at the 3-month exam.

CONCLUSIONS

We found significantly improved cognition 3 months after LVAD surgery in a subset of patients without post-surgical stroke. The reasons for the lack of cognitive improvement at the 1-month post-surgical assessment may include ongoing medical and physiological disruptions in the immediate post-operative period. Further research into the sources of delayed improvement is warranted. Cognitive assessments performed immediately after surgery should be interpreted with caution because the results may not reflect longer term cognitive outcomes. LVAD patients may require additional support to successfully manage their health in the weeks immediately following surgery but assistance needs may decrease over time.

Physiological impact of continuous flow on end-organ function: clinical implications in the current era of left ventricular assist devices

The clinical era of continuous-flow left ventricular assist devices has debunked many myths about the dire need of a pulse for human existence. While this therapy has been documented to provide a clear survival benefit in end-stage heart failure patients, we are now faced with certain morbidity challenges that as of yet have no easy mechanistic physiological explanation. The effect of physiological changes on end-organ function in patients supported by continuous-flow ventricular assist devices may offer insight into some of these morbidities. We therefore present a review of current evidence documenting the impact of continuous flow on end-organ function.

[Near-infrared spectroscopy during cardiopulmonary resuscitation and mechanical circulatory support: From the operating room to the intensive care unit]

BACKGROUND

Near infrared spectroscopy (NIRS) allows continuous measurement of cerebral regional oxygen saturation (rSO2). It is a weighted saturation value derived from approximately 70-75 % venous, 20-25 % arterial and 2.5-5 % capillary blood. In contrast to pulse oximetry, NIRS is independent of pulsatile flow. Therefore, it is also applicable during extracorporeal circulation, cardiopulmonary resuscitation (CPR), and hypothermia.

OBJECTIVES

The purpose of this work is to describe the application of cerebral and somatic NIRS in cardiology and cardiac surgery patients in the operation room, during and after CPR, and during the intensive care unit stay.

MATERIALS AND METHODS

This article is based on peer-reviewed literature from PubMed.

RESULTS

Interventions based on decline of cerebral NIRS values during on-pump cardiac surgery can reduce major organ morbidity and mortality; however, the appearance of a postoperative cognitive dysfunction is scarcely influenced. Persisting of low cerebral oximetry values during resuscitation is a marker for not achieving return of spontaneous circulation under normothermia. NIRS is an additional method for monitoring that can be used during extracorporeal circulation.

CONCLUSION

NIRS is a rapidly available, user-friendly, and noninvasive method for continuous measurement of rSO2. NIRS provides additional information about tissue oxygenation especially during resuscitation and extracorporeal circulatory assist support. Recommendations concerning the use of NIRS for standard monitoring during resuscitation and mechanical circulatory support are not currently available. Further studies are required to show if use of NIRS can reduce pulse control and hands-off times during resuscitation and if use of NIRS can improve outcome after CPR and mechanical circulatory support.

Systolic blood pressure on discharge after left ventricular assist device insertion is associated with subsequent stroke

BACKGROUND

Stroke is a significant complication in patients supported with continuous-flow left ventricular assist devices (CF-LVAD) and hypertension is a significant risk factor for stroke, but the association between blood pressure and stroke in LVAD patients is not well characterized.

METHODS

We identified 275 consecutive patients who survived implant hospitalization between January 2005 and April 2013. Patients were grouped according to systolic blood pressure (SBP) as above a median and below a median of 100 mm Hg by their averaged systolic blood pressure during the 48 hours before discharge from implantation hospitalization. The groups were compared for the primary outcome of time to stroke.

RESULTS

The above-median SBP group had mean SBP of 110 mm Hg and the below-median SBP group had mean SBP of 95 mm Hg. There were no significant between-group differences in body mass index, smoking, vascular disease, hypertension, atrial fibrillation, or prior stroke. During a mean follow-up of 16 months, stroke occurred in 16% of the above-median SBP group vs in 7% of the below-median SBP group (hazard ratio, 2.38; 95% confidence interval, 1.11-5.11), with a similar proportion of hemorrhagic and ischemic strokes in each group. In Cox proportional hazard models adjusting for age, diabetes, or prior stroke, the hazard ratio remained statistically significant. SBP as a continuous variable predictor of stroke had an area under the curve of 0.64 in a receiver operating characteristic curve analysis.

CONCLUSIONS

In this large, CF-LVAD cohort, elevated SBP was independently associated with a greater risk of subsequent stroke. These results identify management of hypertension as a potential modifiable risk factor for reducing the incidence of stroke in patients supported by CF-LVAD.

Is a palpable pulse always restored during cardiopulmonary resuscitation in a patient with a left ventricular assist device?

End-stage heart failure patients are being supported with continuous flow left ventricular assist devices (CF-LVAD) in increasing numbers. The severe physiologic and pharmacologic derangements associated with end-stage heart failure therapies predispose these patients to delirium. During a delirious episode, a patient may inadvertently disconnect CF-LVAD equipment, which may have dangerous consequences. Unfortunately, it is not yet routine to use readily available clinical monitoring tools to allow early detection of delirium in this high-risk population. The authors present a case of acute hyperactive delirium leading to pump power disconnection and cardiopulmonary arrest occurring 7 days after CF-LVAD implantation. The case highlights the need for delirium awareness in the cardiovascular intensive care unit and the unique challenges associated with resuscitation of CF-LVAD patients. The authors propose that cardiovascular intensive care unit patients undergo at least twice daily delirium monitoring and provide a novel resuscitation algorithm for patients who have CF-LVADs.

Cerebral blood flow autoregulation is preserved after continuous-flow left ventricular assist device implantation

OBJECTIVE

To compare cerebral blood flow (CBF) autoregulation in patients undergoing continuous-flow left ventricular assist device (LVAD) implantation with that in patients undergoing coronary artery bypass grafting (CABG).

DESIGN

Prospective, observational, controlled study.

SETTING

Academic medical center.

PARTICIPANTS

Fifteen patients undergoing LVAD insertion and 10 patients undergoing CABG.

MEASUREMENTS AND MAIN RESULTS

Cerebral autoregulation was monitored with transcranial Doppler and near-infrared spectroscopy. A continuous Pearson correlation coefficient was calculated between mean arterial pressure (MAP) and CBF velocity and between MAP and near-infrared spectroscopic data, rendering the variables mean velocity index (Mx) and cerebral oximetry index (COx), respectively. Mx and COx approach 0 when autoregulation is intact (no correlation between CBF and MAP), but approach 1 when autoregulation is impaired. Mx was lower during and immediately after cardiopulmonary bypass in the LVAD group than in the CABG group, indicating better-preserved autoregulation. Based on COx monitoring, autoregulation tended to be better preserved in the LVAD group than in the CABG group immediately after surgery (p = 0.0906). On postoperative day 1, COx was lower in the LVAD group than in the CABG group, indicating preserved CBF autoregulation (p = 0.0410). Based on COx monitoring, 3 patients (30%) in the CABG group had abnormal autoregulation (COx ≥0.3) on the first postoperative day but no patient in the LVAD group had this abnormality (p = 0.037).

CONCLUSIONS

These data suggest that CBF autoregulation is preserved during and immediately after surgery in patients undergoing LVAD insertion.

Medical and nursing care of the child on mechanical circulatory support

OBJECTIVES

To review the medical and nursing care of children receiving mechanical circulatory support as part of the Pediatric Cardiac Intensive Care Society/Extracorporeal Life Support Organization Joint Statement on Mechanical Circulatory Support. DATA SOURCES/STUDY SELECTION/DATA EXTRACTION/DATA SYNTHESIS: This is a general review of current issues of medical and nursing care of children on mechanical circulatory support. It consists of knowledge gained from practical experience combined with supporting evidence and/or discussion of controversies for which evidence exists or is inconclusive. The scope of this review includes assessment and monitoring, cardiovascular, pulmonary, and renal and fluid management, as well as infection prevention and treatment, neurological, and nutritional considerations. Physical and psychological care is discussed, as well as ethical and practical issues regarding termination of support.

CONCLUSIONS

There are unique aspects to the medical and nursing care of a patient requiring mechanical circulatory support. Preserving the possibility for cardiac recovery when possible and preventing damage to noncardiac organs are essential to maximizing the probability that patients will have quality survival following support with a mechanical circulatory support device.

Recent progress in heart failure treatment and heart transplantation

There has been significant progress in heart failure treatment; its stages are defined as a management platform for cardiovascular specialists. Surgical ventricular restoration adds no outcome advantage in ischemic heart failure over coronary artery bypass surgery alone. Novel medical therapies may include cytokine blockade and the vasodilator, relaxin. Although diastolic failure is prevalent, its clinical significance is unclear. Cardiac resynchronization reduces mortality and hospitalization. Perioperative enoximone facilitates beta-blockade for prophylaxis against myocardial ischemia. Heart failure still determines outcome in pulmonary embolism and cardiac surgery. The practice of ventricular assist devices continues to progress. A profile system based on urgency of mechanical support will guide future outcome assessment. Clinical scoring systems will guide the management of right heart failure. Device flow determines the risk of cerebral hyperperfusion and neurologic dysfunction. Regardless of device type, renal dysfunction remains an important outcome determinant. Postoperative heparinization is increasingly challenged because of the risks of bleeding and heparin-induced thrombocytopenia. The practice of heart transplantation continues to mature. The bicaval rather than the biatrial technique improves short-term outcome. Oral sildenafil is effective for pulmonary hypertension and right ventricular support. Although immunosuppression with tacrolimus is beneficial, sirolimus is less nephrotoxic and preserves coronary vasomotor function. The induction of immunosuppression may be modified as it has a weak evidence base. Psychosocial factors also continue to influence clinical outcome significantly. The future of heart failure treatment is bright with signs of active growth and progress in this vibrant subspecialty.