Renal Cortical Perfusion, Measured by Superb Microvascular Imaging, during Infusion of Norepinephrine in Experimental Cardiopulmonary Bypass

Maintenance of beta-blockers and cardiac surgery-related outcomes: a prospective propensity-matched multicentre analysis

BACKGROUND

We investigated the effects of maintaining beta-blockers on the day of surgery on the incidence of atrial fibrillation and postoperative acute kidney injury (AKI) in patients undergoing cardiac surgery.

METHODS

We conducted a multicentre prospective observational study with propensity matching on patients treated with beta-blockers. We collected their baseline patient characteristics, comorbidities, and operative and postoperative outcomes. The endpoints were postoperative atrial fibrillation and AKI after cardiac surgery.

RESULTS

Of the 1789 included patients, propensity matching led to 583 patients in each group. Maintenance of beta-blockers was not associated with a reduced risk of atrial fibrillation (odds ratio: 0.86 [95% confidence interval 0.66-1.14], P=0.335; 141 patients [24.2%] vs 126 patients [21.6%]). Sensitivity analysis did not demonstrate association between beta-blocker maintenance and atrial fibrillation after cardiac surgery (odds ratio: 0.93 [95% confidence interval: 0.72-1.22], P=0.625). Maintenance of beta-blockers was associated with a higher rate of norepinephrine use (415 [71.2%] vs 465 [79.8%], P=0.0001) and postoperative AKI (124 [21.3%] vs 159 [27.3%], P=0.0127). No statistically significant difference was observed in ICU length of stay.

CONCLUSIONS

Maintenance of beta-blockers on the day of surgery was not associated with a reduced incidence of postoperative atrial fibrillation. However, maintenance of beta-blockers was associated with increased usage of vasopressors, potentially contributing to adverse postoperative renal events.

CLINICAL TRIAL REGISTRATION

NCT04769752.

Association Between Changes in Norepinephrine Infusion Rate and Urinary Oxygen Tension After Cardiac Surgery

OBJECTIVES

To determine if the administration of norepinephrine to patients recovering from on-pump cardiac surgery is associated with changes in urinary oxygen tension (PO₂), an indirect index of renal medullary oxygenation.

DESIGN

Single center, prospective observational study.

SETTING

Surgical intensive care unit (ICU).

PARTICIPANTS

A nonconsecutive sample of 93 patients recovering from on-pump cardiac surgery.

MEASUREMENTS AND MAIN RESULTS

In the ICU, norepinephrine was the most commonly used vasopressor agent (90% of patients, 84/93), with fewer patients receiving epinephrine (48%, 45/93) or vasopressin (4%, 4/93). During the 30-to-60-minute period after increasing the infused dose of norepinephrine (n = 89 instances), urinary PO₂ decreased by (least squares mean ± SEM) 1.8 ± 0.5 mmHg from its baseline level of 25.1 ± 1.1 mmHg. Conversely, during the 30-to-60-minute period after the dose of norepinephrine was decreased (n = 134 instances), urinary PO₂ increased by 2.6 ± 0.5 mmHg from its baseline level of 22.7 ± 1.2 mmHg. No significant change in urinary PO₂ was detected when the dose of epinephrine was decreased (n = 21). There were insufficient observations to assess the effects of increasing the dose of epinephrine (n = 11) or of changing the dose of vasopressin (n <4).

CONCLUSIONS

In patients recovering from on-pump cardiac surgery, changes in norepinephrine dose are associated with reciprocal changes in urinary PO₂, potentially reflecting an effect of norepinephrine on renal medullary oxygenation.

Renal and Cerebral Hypoxia and Inflammation During Cardiopulmonary Bypass

Cardiac surgery-associated acute kidney injury and brain injury remain common despite ongoing efforts to improve both the equipment and procedures deployed during cardiopulmonary bypass (CPB). The pathophysiology of injury of the kidney and brain during CPB is not completely understood. Nevertheless, renal (particularly in the medulla) and cerebral hypoxia and inflammation likely play critical roles. Multiple practical factors, including depth and mode of anesthesia, hemodilution, pump flow, and arterial pressure can influence oxygenation of the brain and kidney during CPB. Critically, these factors may have differential effects on these two vital organs. Systemic inflammatory pathways are activated during CPB through activation of the complement system, coagulation pathways, leukocytes, and the release of inflammatory cytokines. Local inflammation in the brain and kidney may be aggravated by ischemia (and thus hypoxia) and reperfusion (and thus oxidative stress) and activation of resident and infiltrating inflammatory cells. Various strategies, including manipulating perfusion conditions and administration of pharmacotherapies, could potentially be deployed to avoid or attenuate hypoxia and inflammation during CPB. Regarding manipulating perfusion conditions, based on experimental and clinical data, increasing standard pump flow and arterial pressure during CPB appears to offer the best hope to avoid hypoxia and injury, at least in the kidney. Pharmacological approaches, including use of anti-inflammatory agents such as dexmedetomidine and erythropoietin, have shown promise in preclinical models but have not been adequately tested in human trials. However, evidence for beneficial effects of corticosteroids on renal and neurological outcomes is lacking. © 2021 American Physiological Society. Compr Physiol 11:1-36, 2021.

Reversal of renal tissue hypoxia during experimental cardiopulmonary bypass in sheep by increased pump flow and arterial pressure

AIM

Renal tissue hypoxia during cardiopulmonary bypass could contribute to the pathophysiology of acute kidney injury. We tested whether renal tissue hypoxia can be alleviated during cardiopulmonary bypass by the combined increase in target pump flow and mean arterial pressure.

METHODS

Cardiopulmonary bypass was established in eight instrumented sheep under isoflurane anaesthesia, at a target continuous pump flow of 80 mL·kg^-1 min^-1 and mean arterial pressure of 65 mmHg. We then tested the effects of simultaneously increasing target pump flow to 104 mL·kg^-1 min^-1 and mean arterial pressure to 80 mmHg with metaraminol (total dose 0.25-3.75 mg). We also tested the effects of transitioning from continuous flow to partially pulsatile flow (pulse pressure ~15 mmHg).

RESULTS

Compared with conscious sheep, at the lower target pump flow and mean arterial pressure, cardiopulmonary bypass was accompanied by reduced renal blood flow (6.8 ± 1.2 to 1.95 ± 0.76 mL·min^-1 kg^-1) and renal oxygen delivery (0.91 ± 0.18 to 0.24 ± 0.11 mL·O₂ min^-1 kg^-1). There were profound reductions in cortical oxygen tension (PO₂) (33 ± 13 to 6 ± 6 mmHg) and medullary PO₂ (31 ± 12 to 8 ± 8 mmHg). Increasing target pump flow and mean arterial pressure increased renal blood flow (to 2.6 ± 1.0 mL·min^-1 kg^-1) and renal oxygen delivery (to 0.32 ± 0.13 mL·O₂ min^-1kg^-1) and returned cortical PO₂ to 58 ± 60 mmHg and medullary PO₂ to 28 ± 16 mmHg; levels similar to those of conscious sheep. Partially pulsatile pump flow had no significant effects on renal perfusion or oxygenation.

CONCLUSIONS

Renal hypoxia during experimental CPB can be corrected by increasing target pump flow and mean arterial pressure within a clinically feasible range.

Anaesthesia and ICU sedation with sevoflurane do not reduce myocardial injury in patients undergoing cardiac surgery: A randomized prospective study

BACKGROUND

To evaluate the effect of anaesthesia and ICU sedation with sevoflurane to protect the myocardium against ischemia-reperfusion injury associated to cardiac surgery assessed by troponin release.

METHODS

We performed a prospective, open-label, randomized study in cardiac surgery with cardiopulmonary bypass. Patients were randomized to an algorithm-based intervention group and a control group. The main outcome was the perioperative kinetic of cardiac troponin I (cTnI). The secondary outcomes included composite endpoint, GDF-15 (macrophage inhibitory cytokine-1) value, arterial lactate levels, and the length of stay (LOS) in the ICU.

RESULTS

Of 82 included patients, 81 were analyzed on an intention-to-treat basis (intervention group: n = 42; control group: n = 39). On inclusion, the intervention and control groups did not differ significantly in terms of demographic and surgical data. The postoperative kinetics of cTnI did not differ significantly between groups: the mean difference was 0.44 ± 1.09 μg/ml, P = .69. Incidence of composite endpoint and GDF-15 values were higher in the sevoflurane group than in propofol group. The intervention and control groups did not differ significantly in terms of ICU stay and hospital stay.

CONCLUSION

The use of an anaesthesia and ICU sedation with sevoflurane was not associated with a lower incidence of myocardial injury assessed by cTnI. Sevoflurane administration was associated with higher prevalence of acute renal failure and higher GDF-15 values.

Acute kidney injury

Acute kidney injury (AKI) is defined by a rapid increase in serum creatinine, decrease in urine output, or both. AKI occurs in approximately 10-15% of patients admitted to hospital, while its incidence in intensive care has been reported in more than 50% of patients. Kidney dysfunction or damage can occur over a longer period or follow AKI in a continuum with acute and chronic kidney disease. Biomarkers of kidney injury or stress are new tools for risk assessment and could possibly guide therapy. AKI is not a single disease but rather a loose collection of syndromes as diverse as sepsis, cardiorenal syndrome, and urinary tract obstruction. The approach to a patient with AKI depends on the clinical context and can also vary by resource availability. Although the effectiveness of several widely applied treatments is still controversial, evidence for several interventions, especially when used together, has increased over the past decade.