Renal Insufficiency After Cardiac Surgery

The new millennium ushered in a number of changes in cardiac surgery. Off-pump coronary artery bypass surgery became technically easier so that multivessel surgery became less of a challenge and cardiologists were supplied with new catheters that accessed lesions that were previously thought of as being unapproachable. New drugs were introduced that made the management of heart failure patients feasible on an outpatient basis, and new devices extend the bridging period to transplantation. However, these advances have not necessarily been attended by significant improvements in outcome, possibly because the less challengng a procedure becomes, the sicker the patients that can be managed. This observation is particularly true with the incidence and outcome of renal failure after cardiac surgery. Bypass factors have been manipulated without much effect, and the traditional drugs that were found to increase renal blood flow in animal experiments did not translate into clinical improvement in renal outcome. Recent research has given us insight into the pathophysiology of ischemic acute renal failure, and it has been found that the paradigm was not as simple as previously thought, possibly accounting for the failure of the more traditional renal drugs (dopamine, mannitol and diuretics). However, these new insights open up the possibility of novel targets for renal protection and repair.

Blood transfusions are associated with urinary biomarkers of kidney injury in cardiac surgery

OBJECTIVE

Cardiac surgery is a major cause of acute kidney injury. In this setting, receipt of blood transfusions seems to be associated with a higher risk of acute kidney injury, as measured using serum creatinine values. We examined this association further by using urinary biomarkers of kidney injury.

METHODS

A total of 1210 adults underwent cardiac surgery and were divided into 3 groups on the basis of the receipt of intraoperative packed red blood cell units: no blood (n = 894), 2 or less packed red blood cell units (n = 206), and more than 2 packed red blood cell units (n = 110). Acute kidney injury was defined as (1) doubling of serum creatinine from the preoperative value; (2) first postoperative urinary interleukin-18 in the fifth quintile; and (3) first postoperative urinary neutrophil gelatinase-associated lipocalin in the fifth quintile. We determined the relative risk for acute kidney injury outcome according to packed red blood cell units group after adjusting for 12 preoperative and surgical variables. By using the Sobel test for mediation analysis, we also evaluated the role of biomarkers in causing acute kidney injury through alternative pathways.

RESULTS

Acute kidney injury was more common in those who received more than 2 packed red blood cell units. In patients receiving more than 2 packed red blood cell units, the adjusted relative risks were 2.3 (95% confidence interval, 1.2-4.4, P .01), 1.36 (95% confidence interval, 1.0-1.9, P .05), and 1.34 (95% confidence interval, 1.0-1.8, P .06) for doubling of serum creatinine, urinary interleukin-18 in the fifth quintile (>60 pg/mL), and urinary neutrophil gelatinase-associated lipocalin in the fifth quintile (>102 ng/mL), respectively. Furthermore, the effect of packed red blood cell units transfusion on acute kidney injury was partially mediated by interleukin-18.

CONCLUSIONS

Receipt of 2 or more packed red blood cell units during cardiac surgery is associated with a greater risk of acute kidney injury defined by serum creatinine and kidney injury biomarkers.

Preoperative angiotensin-converting enzyme inhibitors and angiotensin receptor blocker use and acute kidney injury in patients undergoing cardiac surgery

BACKGROUND

Using either an angiotensin-converting enzyme inhibitor (ACEi) or an angiotensin receptor blocker (ARB) the morning of surgery may lead to 'functional' postoperative acute kidney injury (AKI), measured by an abrupt increase in serum creatinine. Whether the same is true for 'structural' AKI, measured with new urinary biomarkers, is unknown.

METHODS

The TRIBE-AKI study was a prospective cohort study of 1594 adults undergoing cardiac surgery at six hospitals between July 2007 and December 2010. We classified the degree of exposure to ACEi/ARB into three categories: 'none' (no exposure prior to surgery), 'held' (on chronic ACEi/ARB but held on the morning of surgery) or 'continued' (on chronic ACEi/ARB and taken the morning of surgery). The co-primary outcomes were 'functional' AKI based upon changes in pre- to postoperative serum creatinine, and 'structural AKI', based upon peak postoperative levels of four urinary biomarkers of kidney injury.

RESULTS

Across the three levels (none, held and continued) of ACEi/ARB exposure there was a graded increase in functional AKI, as defined by AKI stage 1 or worse; (31, 34 and 42%, P for trend 0.03) and by percentage change in serum creatinine from pre- to postoperative (25, 26 and 30%, P for trend 0.03). In contrast, there were no differences in structural AKI across the strata of ACEi/ARB exposure, as assessed by four structural AKI biomarkers (neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, interleukin-18 or liver-fatty acid-binding protein).

CONCLUSIONS

Preoperative ACEi/ARB usage was associated with functional but not structural acute kidney injury. As AKI from ACEi/ARB in this setting is unclear, interventional studies testing different strategies of perioperative ACEi/ARB use are warranted.

Prevention and treatment of acute kidney injury in patients undergoing cardiac surgery: a systematic review

BACKGROUND

Acute kidney injury (AKI) is common in patients undergoing cardiac surgery and is associated with a high rate of death, long-term sequelae and healthcare costs. We conducted a systematic review of randomized controlled trials for strategies to prevent or treat AKI in cardiac surgery.

METHODS

We screened Medline, Scopus, Cochrane Renal Library, and Google Scholar for randomized controlled trails in cardiac surgery for prevention or treatment of AKI in adults.

RESULTS

We identified 70 studies that contained a total of 5,554 participants published until November 2008. Most studies were small in sample size, were single-center, focused on preventive strategies, and displayed wide variation in AKI definitions. Only 26% were assessed to be of high quality according to the Jadad criteria. The types of strategies with possible protective efficacy were dopaminergic agents, vasodilators, anti-inflammatory agents, and pump/perfusion strategies. When analyzed separately, dopamine and N-acetylcysteine did not reduce the risk for AKI.

CONCLUSIONS

This summary of all the literature on prevention and treatment strategies for AKI in cardiac surgery highlights the need for better information. The results advocate large, good-quality, multicenter studies to determine whether promising interventions reliably reduce rates of acute renal replacement therapy and mortality in the cardiac surgery setting.

Endobronchial ultrasound for the diagnosis of pulmonary sarcoidosis

BACKGROUND

The diagnosis of pulmonary sarcoidosis can be established by a variety of techniques. Transbronchial lung biopsy is often the preferred approach, but it is frequently nondiagnostic and carries a risk of pneumothorax and bleeding. Mediastinoscopy is often suggested as the next diagnostic step but entails significant cost and associated morbidity. Endobronchial ultrasound (EBUS) with transbronchial needle aspiration (TBNA) is emerging as a safe, minimally invasive tool for the primary diagnosis of mediastinal and hilar lymphadenopathy. The purpose of this study was to assess the utility of EBUS-TBNA for pulmonary sarcoidosis.

METHODS

Fifty consecutive patients who had been referred for EBUS-TBNA for suspected pulmonary sarcoidosis were included in the study. On-site cytology was used to assess the adequacy of the samples. The presence of noncaseating granulomas without necrosis in the appropriate clinical setting was deemed to be adequate for the diagnosis of pulmonary sarcoidosis. Patients with a negative EBUS-TBNA underwent further histologic biopsy or clinical follow-up to determine the final diagnosis.

RESULTS

Eighty-two lymph nodes with a median size of 16 mm (range, 4 to 40 mm) were punctured. EBUS-TBNA demonstrated noncaseating granulomas without necrosis in 41 of 48 patients (85%) with a final diagnosis of sarcoidosis. EBUS-TBNA, therefore, has a sensitivity of 85% for the primary diagnosis of pulmonary sarcoidosis.

CONCLUSIONS

EBUS-TBNA is a safe, minimally invasive tool for the primary diagnosis of pulmonary sarcoidosis that has a high diagnostic yield. EBUS-TBNA should be considered an appropriate alternative diagnostic technique for patients with suspected pulmonary sarcoidosis.

Atrial Fibrillation

Over 2 million people in the Untied States are known to have AF, and this number is expected to rise to 5 to 6 million in the next 50 years. In spite of advances in detection and treatment of AF, it is still associated with significant morbidity and mortality. Treatment currently consists of rhythm management and prevention of embolic events (anticoagulation). Although two strategies of rhythm management exist (heart rate control and heart rhythm control), a distinct advantage of one over the other has not yet been determined. Because of the increasing numbers of patients who have AF in the general population and newer surgical approaches to dealing with AF, the anesthesiologist encounters patients who have AF on an almost daily basis. Fortunately, national and international guidelines exist for the treatment of pre-existing AF and dealing with anticoagulated patients in the perioperative period, clearly indicating whether a patient is adequately managed or not by current standards of practice. With respect to the new development of AF in the perioperative period, cardiac and thoracic surgeries are particularly associated with this phenomenon. Guidelines have been published for the perioperative management of AF after cardiac surgery, and are in accordance with the findings from studies in thoracic surgery. Beta-blockers and amiodarone are strongly recommended for the pre-emptive treatment of AF in high-risk patients, whereas amiodarone and sotalol are the agents of choice in those patients developing AF after surgery not requiring urgent cardioversion. The recent discoveries of properties of statins other than their lipid-lowering abilities has sparked wide interest in the possibility of this family of drugs having a protective role against AF in many scenarios. It remains to be seen whether statins will prove to be adjunct in patients at high risk for AF in the perioperative period.

Superior vena cava syndrome related to indwelling intravenous catheters in patients with cystic fibrosis

Patients with cystic fibrosis (CF) often need long-term implanted vascular-access devices for intravenous antibiotics for chronic lower respiratory tract infections. These devices are not without complications, including infection, occlusion, and vascular thrombosis. Such thrombosis can result in superior vena cava (SVC) syndrome due to the position of the catheter proximal to the right atrium. SVC syndrome in CF patients, however, is rarely reported in the literature, suggesting that its incidence is uncommon. We describe three patients with SVC syndrome as a consequence of implanted vascular-access devices.

Adverse gastrointestinal complications after cardiopulmonary bypass: can outcome be predicted from preoperative risk factors?

Adverse gastrointestinal (GI) outcome after cardiac surgery is an infrequent event but is a clinically important health care problem because of associated increased morbidity and mortality. The ability to identify patients at greatest risk before surgery may be helpful in planning appropriate perioperative management strategies. We examined the pre- and intraoperative characteristics of 2417 patients from 24 diverse United States medical centers enrolled in the Multicenter Study of Perioperative Ischemia Study who were undergoing cardiac surgery using cardiopulmonary bypass as predictors for adverse GI outcome. Resource utilization was evaluated for patients with and without adverse GI outcomes. Adverse GI outcomes occurred in 5.5% of patients (133 of 2417), increased in-hospital mortality 6.5-fold, prolonged the mean intensive care unit length of stay by 1 wk, and more than doubled the mean postoperative hospital stay (P < 0.0001). Predictors of adverse GI outcome included decreased left ventricular function, hyperbilirubinemia, thrombocytopenia, prolonged partial thromboplastin time, prior cardiovascular surgery, combined coronary artery bypass graft surgery and intracardiac or proximal aortic surgery, pharmacological cardiovascular support, and intraoperative transfusion. The literature suggests that adverse GI outcome after cardiac surgery is secondary to poor splanchnic perfusion, which many of these risk factors may predict. Therefore, patients deemed to be at risk before surgery may benefit from tightly controlled hemodynamic management and other strategies that optimize perioperative organ perfusion.

IMPLICATIONS

We identified the preoperative and intraoperative predictors associated with an increased incidence of postoperative gastrointestinal complications after cardiac surgery using cardiopulmonary bypass. Because these complications are associated with frequent morbidity and mortality, these predictors may be helpful in identifying patients at increased risk so that risk stratification can be modified and perioperative management can be appropriately adjusted.

Mannitol and dopamine in patients undergoing cardiopulmonary bypass: a randomized clinical trial

In this prospective, randomized, placebo-controlled, double-blinded study, we determined the effects of two commonly used adjuncts, mannitol and dopamine, on beta(2)-microglobulin (beta(2)M) excretion rates in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass (CPB). beta(2)M excretion rate has been described as a sensitive marker of proximal renal tubular function. One-hundred patients with a preoperative serum creatinine level <or=1.5 mg/dL were prospectively randomized into 4 groups: 1). placebo, 2). mannitol 1 g/kg added to the CPB prime, 3). dopamine 2 microg kg(-1x. min(-1) from the induction of anesthesia to 1 h post-CPB, or 4). mannitol plus dopamine. The primary outcome measure was beta(2)M excretion rate at 1 h post-CPB. Secondary outcome measures included beta(2)M excretion rate at 6 and 24 h post-CPB; urinary flow rate and creatinine clearance at 1, 6, and 24 h post-CPB; and the highest postoperative serum creatinine level. Length of intensive care stay and hospitalization, as well as adverse events, were also considered secondary outcomes. Dopamine significantly increased beta(2)M excretion rate at 1 h post-CPB (2.48 +/- 3.61 microg/min) compared with placebo (0.59 +/- 1.04 microg/min; P = 0.001). This effect was not ameliorated by the addition of mannitol (beta(2)M excretion rate, 2.05 +/- 2.77 microg/min; P = 0.007 compared with placebo). beta(2)M excretion rate was similar in patients given placebo or mannitol alone (P = 0.831). Rather than being a protective drug in the setting of CPB, dopamine alone or in combination with mannitol increases beta(2)M excretion rate, which may be a measure of renal tubular dysfunction. The clinical implications of this increase and whether it is also seen in patients with established renal dysfunction undergoing CPB require additional investigation.

IMPLICATIONS

In many clinical settings, an increased beta-2-microglobulin (beta(2)M) excretion rate indicates renal tubular injury. In this cardiopulmonary bypass (CPB) study, a dopamine infusion (alone or with mannitol) resulted in an increased beta(2)M excretion rate. It is unclear whether this dopamine-related increase implies renal injury after CPB, and further investigations are required to examine the mechanism/clinical relevance of this observation.

A case series of low-dose fenoldopam in seventy cardiac surgical patients at increased risk of renal dysfunction

OBJECTIVE

To evaluate the usefulness of low-dose fenoldopam mesylate in patients at risk of developing renal dysfunction after cardiac surgery requiring cardiopulmonary bypass.

DESIGN

A prospective, single-center, observational study.

SETTING

University teaching hospital.

PARTICIPANTS

Seventy patients scheduled for elective cardiac surgery with one or more predefined risk factors for renal dysfunction.

INTERVENTIONS

After induction of anesthesia, fenoldopam (0.03 microg/kg/min) was administered throughout surgery and into the postoperative period, until the patient was stable and weaned from all other vasoactive agents. Perioperatively, fenoldopam was also used as a second-line antihypertensive agent as required.

MEASUREMENTS AND MAIN RESULTS

No patient developed renal failure that required dialysis, whereas 7.1% (5/70) developed non-dialysis-dependent renal dysfunction. Four out of these 5 patients had 2 or more risk factors (9.5%). Higher preoperative creatinine levels, a history of hypertension, myocardial infarction within 5 days of surgery, and a preoperative diagnosis of chronic renal insufficiency were all good predictors of postoperative non-dialysis-dependent renal dysfunction. Discharge serum creatinine levels were lower than preoperative levels (1.16 +/- 0.36 mg/dL v 1.26 +/- 0.34 mg/dL, p < 0.05).

CONCLUSION

These findings suggest that renal function was preserved in patients at increased risk for renal dysfunction after cardiac surgery when low-dose fenoldopam was used in the perioperative period. However, a randomized, controlled trial is required to establish efficacy.

Tubal surface lidocaine mediates pre-emptive analgesia in awake laparoscopic sterilization: a prospective, randomized clinical trial

OBJECTIVE

The purpose of this study was to determine whether lidocaine that is instilled onto the Fallopian tubes reduces pain scores in awake patients who undergo laparoscopic sterilization with Filshie clips.

STUDY DESIGN

This was a prospective, randomized, placebo-controlled, double-blinded, clinical trial study that was approved by our institutional review board.

RESULTS

Pain scores (visual analogue scales) were lower in the lidocaine group (n = 12 patients) than in the placebo group (n = 12 patients) at clip application (6 vs 71 mm; P <.0001) and after 15 minutes after operation (15.5 vs 44.5 mm; P <.005). No significant differences occurred at 1-hour after operation or discharge, but more rescue analgesia was required in the placebo group ( P <.05), with more side effects ( P <.05). In a separate group of 20 women, serum lidocaine levels were measured (maximum level, 16.0 micromol/L). Holter monitoring of these patients revealed no significant arrhythmias.

CONCLUSION

One percent lidocaine that is instilled onto the Fallopian tubes reduces pain scores in awake patients who undergo laparoscopic sterilization with Filshie clips.

Transesophageal echocardiography interpretation: a comparative analysis between cardiac anesthesiologists and primary echocardiographers

Diagnostic interpretation of intraoperative transesophageal echocardiography (TEE) examinations may vary, particularly when the echocardiographer is also the anesthesiologist. We therefore evaluated the concordance of TEE interpretation as part of a process of continuous quality improvement (CQI). Ten cardiac anesthesiologists participating in a CQI program conducted 154 comprehensive TEE examinations, each consisting of 16 major fields describing cardiac anatomy and function. These examinations were subsequently interpreted off-line by two primary echocardiographers (a radiologist and a cardiologist). Agreement was assessed using the kappa coefficient and percent agreement. Overall kappa and percent agreement were 0.58 and 83% for anesthesiologists versus radiologist, 0.57 and 80% for anesthesiologists versus cardiologist, and 0.60 and 82% for radiologist versus cardiologist. Anesthesiologists with longer than 5 yr of TEE experience had higher levels of agreement with the radiologist when assessing the aorta, right atrium, pulmonary vein flow, transmitral flow, and fractional area change. Cardiac anesthesiologists supported by a CQI program interpret TEE examinations at a level comparable with physicians whose primary practice is echocardiography. Thus, the anesthesiologist and the intraoperative echocardiographer need not be mutually exclusive.

IMPLICATIONS

Interpretation of intraoperative transesophageal echocardiograms can be reliably performed by cardiac anesthesiologists.

Intraoperative transesophageal ultrasonography can measure renal blood flow

OBJECTIVE

To determine the feasibility of acquiring Doppler-derived indices of renal blood flow by transesophageal ultrasonography in the perioperative period.

DESIGN

Prospective, sequential, institutional review board-approved study.

SETTING

University teaching hospital.

PARTICIPANTS

Nine patients with normal renal function, scheduled for elective primary coronary artery bypass graft surgery.

INTERVENTIONS

Two-dimensional images of renal parenchyma and Doppler measurement of intrarenal arterial blood flow during internal mammary dissection were acquired. To effect renal blood flow changes, the renal vasodilator dopamine, 2 microg/kg/min, was infused for 20 minutes after baseline measurements were made. Renal Doppler measurements were repeated to determine whether transesophageal ultrasonography can follow these changes.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic measurements (heart rate, mean arterial blood pressure, cardiac output, and cardiac index) and Doppler velocity measurements of intrarenal arterial blood flow (peak systolic, end-diastolic, and mean velocity) were made at time 1 (T1 = baseline) and at time 2 (T2 = after 20 minutes of dopamine infusion). The derived Doppler indices, pulsatility index and resistive index, were calculated according to standard formulae. Measurements were compared by paired Student's t-test (two-tailed, p < 0.05, significant). There were no statistical differences between cardiac index (2.10 +/- 0.93 L/min/m2 v 2.21 +/- 0.92 L/min/m2, p = 0.254) and mean arterial pressure (82.3 +/- 11.2 mmHg v 83.3 +/- 14.5 mmHg, p = 0.872) between T1 and T2. Systolic renal velocity increased from 44.7 +/- 13.0 cm/s to 63.0 +/- 20.4 cm/s (p = 0.005), diastolic velocity increased from 12.7 +/- 4.0 cm/s to 22.4 +/- 7.8 cm/s (p = 0.0003), and mean velocity increased from 22.5 +/- 6.6 cm/s to 34.1 +/- 11.7 cm/s (p = 0.003) after infusion of dopamine. These results indicate an increase in renal blood flow from baseline values. The pulsatility index decreased from 1.44 +/- 0.29 to 1.21 +/- 0.24 (p = 0.0005), whereas the resistive index decreased from 0.71 +/- 0.06 to 0.64 +/- 0.06 (p = 0.0004) after dopamine. Reductions in pulsatility and resistive indices indicate a reduction in renal vascular resistance.

CONCLUSION

This study demonstrates the ability to acquire two-dimensional images of kidney and renal arterial Doppler velocities using transesophageal ultrasonography during cardiac surgery. Transesophageal renal arterial Doppler waveform analysis can follow changes in renal blood flow patterns secondary to interventional therapy.

New pharmacologic options for renal preservation

The understanding of the cause and pathophysiology of renal failure has guided the rational development of pharmacologic renoprotective strategies. Although traditionally anesthesiologists have focused on renal hemodynamic derangements, newer information suggests that cellular interactions amplify and perpetuate the insult. Consequently, the potential renoprotective armamentarium not only encompasses the more traditional vasoactive agents but also therapeutic approaches that may modify the cellular response to injury. Although few of these agents have reached the clinical arena, preliminary work suggests that this new approach to renal injury and protection may be promising.