Blood pressure excursions below the cerebral autoregulation threshold during cardiac surgery are associated with acute kidney injury. Crit Care Med. 2013;41:464-471. [PMID: 23263580 DOI: 10.1097/ccm.0b013e31826ab3a1]

Ventilatory strategy during liver transplantation: implications for near-infrared spectroscopy-determined frontal lobe oxygenation

BACKGROUND

As measured by near infrared spectroscopy (NIRS), cerebral oxygenation (ScO2) may be reduced by hyperventilation in the anhepatic phase of liver transplantation surgery (LTx). Conversely, the brain may be subjected to hyperperfusion during reperfusion of the grafted liver. We investigated the relationship between ScO2 and end-tidal CO2 tension (EtCO2) during the various phases of LTx.

METHODS

In this retrospective study, 49 patients undergoing LTx were studied. Forehead ScO2, EtCO2, minute ventilation (VE), and hemodynamic variables were recorded from the beginning of surgery through to the anhepatic and reperfusion phases during LTx.

RESULTS

In the anhepatic phase, ScO2 was reduced by 4.3% (95% confidence interval: 2.5-6.0%; P < 0.0001), EtCO2 by 0.3 kPa (0.2-0.4 kPa; P < 0.0001), and VE by 0.4 L/min (0.1-0.7 L/min; P = 0.0018). Conversely, during reperfusion of the donated liver, ScO2 increased by 5.5% (3.8-7.3%), EtCO2 by 0.7 kPa (0.5-0.8 kPa), and VE by 0.6 L/min (0.3-0.9 L/min; all P < 0.0001). Changes in ScO2 were correlated to those in EtCO2 (Pearson r = 0.74; P < 0.0001).

CONCLUSION

During LTx, changes in ScO2 are closely correlated to those of EtCO2. Thus, this retrospective analysis suggests that attention to maintain a targeted EtCO2 would result in a more stable ScO2 during the operation.

Intraoperative blood pressure and cerebral perfusion: strategies to clarify hemodynamic goals

Blood pressure can vary considerably during anesthesia. If blood pressure falls outside the limits of cerebrovascular autoregulation, children can become at risk of cerebral ischemic or hyperemic injury. However, the blood pressure limits of autoregulation are unclear in infants and children, and these limits can shift after brain injury. This article will review autoregulation, considerations for the hemodynamic management of children with brain injuries, and research on autoregulation monitoring techniques.

Cardiovascular consequence of reclining vs. sitting beach-chair body position for induction of anesthesia

The sitting beach-chair position is regularly used for shoulder surgery and anesthesia may be induced in that position. We tested the hypothesis that the cardiovascular challenge induced by induction of anesthesia is attenuated if the patient is placed in a reclining beach-chair position. Anesthesia was induced with propofol in the sitting beach-chair (n = 15) or with the beach-chair tilted backwards to a reclining beach-chair position (n = 15). The last group was stepwise tilted to the sitting beach-chair position prior to surgery. Hypotension was treated with ephedrine. Continuous hemodynamic variables were recorded by photoplethysmography and frontal cerebral oxygenation (ScO₂) by near infrared spectroscopy. Significant differences were only observed immediately after the induction when patients induced in a reclining beach-chair position had higher mean arterial pressure (MAP) (35 ± 12 vs. 45 ± 15 % reduction from baseline, p = 0.04) and ScO₂ (7 ± 6 vs. 1 ± 8% increase from baseline, p = 0.02) and received less ephedrine (mean: 4 vs. 13 mg, p = 0.048). The higher blood pressure and lower need of vasopressor following induction of anesthesia in the reclining compared to the sitting beach-chair position indicate more stable hemodynamics with the clinical implication that anesthesia should not be induced with the patient in the sitting position.

Impact of perioperative blood pressure variability on health resource utilization after cardiac surgery: an analysis of the ECLIPSE trials

OBJECTIVE

To examine the impact of blood pressure control on hospital health resource utilization using data from the ECLIPSE trials.

DESIGN

Post-hoc analysis of data from 3 prospective, open-label, randomized clinical trials (ECLIPSE trials).

SETTING

Sixty-one medical centers in the United States.

PARTICIPANTS

Patients 18 years or older undergoing cardiac surgery.

INTERVENTIONS

Clevidipine was compared with nitroglycerin, sodium nitroprusside, and nicardipine.

MEASUREMENTS AND MAIN RESULTS

The ECLIPSE trials included 3 individual randomized open-label studies comparing clevidipine to nitroglycerin, sodium nitroprusside, and nicardipine. Blood pressure control was assessed as the integral of the cumulative area under the curve (AUC) outside specified systolic blood pressure ranges, such that lower AUC represents less variability. This analysis examined surgery duration, time to extubation, as well as intensive care unit (ICU) and hospital length of stay (LOS) in patients with AUC≤10 mmHg×min/h compared to patients with AUC>10 mmHg×min/h. One thousand four hundred ten patients were included for analysis; 736 patients (52%) had an AUC≤10 mmHg×min/h, and 674 (48%) had an AUC>10 mmHg×min/h. The duration of surgery and ICU LOS were similar between groups. Time to extubation and postoperative LOS were both significantly shorter (p = 0.05 and p<0.0001, respectively) in patients with AUC≤10. Multivariate analysis demonstrates AUC≤10 was significantly and independently associated with decreased time to extubation (hazard ratio 1.132, p = 0.0261) and postoperative LOS (hazard ratio 1.221, p = 0.0006).

CONCLUSIONS

Based on data derived from the ECLIPSE studies, increased perioperative BP variability is associated with delayed time to extubation and increased postoperative LOS.

Duration and magnitude of blood pressure below cerebral autoregulation threshold during cardiopulmonary bypass is associated with major morbidity and operative mortality

OBJECTIVES

Optimizing blood pressure using near-infrared spectroscopy monitoring has been suggested to ensure organ perfusion during cardiac surgery. Near-infrared spectroscopy is a reliable surrogate for cerebral blood flow in clinical cerebral autoregulation monitoring and might provide an earlier warning of malperfusion than indicators of cerebral ischemia. We hypothesized that blood pressure below the limits of cerebral autoregulation during cardiopulmonary bypass would be associated with major morbidity and operative mortality after cardiac surgery.

METHODS

Autoregulation was monitored during cardiopulmonary bypass in 450 patients undergoing coronary artery bypass grafting and/or valve surgery. A continuous, moving Pearson's correlation coefficient was calculated between the arterial pressure and low-frequency near-infrared spectroscopy signals and displayed continuously during surgery using a laptop computer. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was compared between patients with and without major morbidity (eg, stroke, renal failure, mechanical lung ventilation >48 hours, inotrope use >24 hours, or intra-aortic balloon pump insertion) or operative mortality.

RESULTS

Of the 450 patients, 83 experienced major morbidity or operative mortality. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was independently associated with major morbidity or operative mortality after cardiac surgery (odds ratio, 1.36; 95% confidence interval, 1.08-1.71; P = .008).

CONCLUSIONS

Blood pressure management during cardiopulmonary bypass using physiologic endpoints such as cerebral autoregulation monitoring might provide a method of optimizing organ perfusion and improving patient outcomes from cardiac surgery.

Cerebral near-infrared spectroscopy monitoring and neurologic outcomes in adult cardiac surgery patients: a systematic review

BACKGROUND

Near-infrared spectroscopy is used during cardiac surgery to monitor the adequacy of cerebral perfusion. In this systematic review, we evaluated available data for adult patients to determine (1) whether decrements in cerebral oximetry during cardiac surgery are associated with stroke, postoperative cognitive dysfunction (POCD), or delirium; and (2) whether interventions aimed at correcting cerebral oximetry decrements improve neurologic outcomes.

METHODS

We searched PubMed, Cochrane, and Embase databases from inception until January 31, 2012, without restriction on languages. Each article was examined for additional references. A publication was excluded if it did not include original data (e.g., review, commentary) or if it was not published as a full-length article in a peer-reviewed journal (e.g., abstract only). The identified abstracts were screened first, and full texts of eligible articles were reviewed independently by 2 investigators. For eligible publications, we recorded the number of subjects, type of surgery, and criteria for diagnosis of neurologic end points.

RESULTS

We identified 13 case reports, 27 observational studies, and 2 prospectively randomized intervention trials that met our inclusion criteria. Case reports and 2 observational studies contained anecdotal evidence suggesting that regional cerebral O(2) saturation (rSco(2)) monitoring could be used to identify cardiopulmonary bypass cannula malposition. Six of 9 observational studies reported an association between acute rSco(2) desaturation and POCD based on the Mini-Mental State Examination (n = 3 studies) or more detailed cognitive testing (n = 6 studies). Two retrospective studies reported a relationship between rSco(2) desaturation and stroke or type I and II neurologic injury after surgery. The observational studies had many limitations, including small sample size, assessments only during the immediate postoperative period, and failure to perform risk adjustments. Two randomized studies evaluated the efficacy of interventions for treating rSco(2) desaturation during surgery, but adherence to the protocol was poor in one. In the other study, interventions for rSco(2) desaturation were associated with less major organ injury and shorter intensive care unit hospitalization compared with nonintervention.

CONCLUSIONS

Reductions in rSco(2) during cardiac surgery may identify cardiopulmonary bypass cannula malposition, particularly during aortic surgery. Only low-level evidence links low rSco(2) during cardiac surgery to postoperative neurologic complications, and data are insufficient to conclude that interventions to improve rSco(2) desaturation prevent stroke or POCD.