The primary functions of the kidneys and the renal system are to regulate extracellular fluid volume and blood pressure, osmolarity, electrolytes, and pH; to excrete toxins and waste; and to produce specific hormones.
If the kidneys are acutely injured, the body will experience a reduction or loss of glomerular filtration and urine output, leading to the retention of water, sodium and other metabolites, as well as to a higher propensity for ongoing kidney malfunction and disease.
The First Rule of 3: AKI Pathophysiology
There are three types of AKI pathophysiology:
- Pre-Renal – resulting in hypovolemia, hypotension, renal vasoconstriction and glomerular efferent arteriolar vasodilation
- Renal – characterized by acute tubular necrosis (ATN), acute interstitial nephritis, glomerulonephritis, and intratubular obstruction
- Post-Renal – with renal/ureteral calculi (stones), ureteral obstruction (tumors, clots, neurogenic bladder), and urethral obstruction (prostate enlargement)
The 2nd Rule of 3: Cardiac-Assisted AKI (CSA-AKI)
Cardiac surgeries can be a significant risk for resulting in CSA-AKI. Some estimates place that risk as high as 50%. Patients impacted by CSA-AKI face higher risks for mortality, increased ICU and hospital stays, increased costs for short-term and long-term care, and increased chances for chronic kidney disease.
The three primary causes for CSA-AKI during cardiac surgery are:
- Reduced renal blood flow
- Negative effects from cardiopulmonary bypass (renal perfusion, systemic inflammation, reperfusion injury, embolization of circuit materials, hemolysis)
- Effects of medications administered during the surgery
The Rule of 272: Oxygen Delivery Level
The primary risk of cardiac surgeries to result in CSA-AKI is from reduced renal blood flow due to the underlying heart failure or low cardiac output, and suboptimal blood flow and blood pressure. Additionally, issues with hemodilution, transfusion, thromboemboli, and low oxygen deliver can contribute.
Critical to the avoidance of CSA-AKI is maintaining blood oxygen delivery levels during the surgery to no less than 272 ml/min per m2.
Conclusion
With informed perfusion techniques, the risk for CSA-AKI can be actively managed during cardiac surgeries:
- Renal perfusion pressure should be kept within a 70-90 mm Hg range.
- Medications should be limited to nephrotoxic antibiotics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and NSAIDs
- Critical oxygen delivery should remain above 272 ml/min per m2
About SpecialtyCare
At SpecialtyCare, it’s our mission to help make every surgery safer, and we partner with ORs around the nation to provide critical services, reduce errors, and optimize team performance. As the industry leader in OR services, our teams are integrated with 1,200 hospitals and health systems nationwide, supporting 13,500 physicians during 500,000+ procedures annually. Our teams participate in 1 in 7 of all cardiac surgeries done in the U.S. each year.
We are highly experienced, among the most trusted leaders in the cardiac industry.We hire and train some of the best specialists in the medical industry to entrench ourselves as the source of reliable coverage for some of the most complex operations in modern medicine. If you’re interested in how we can assist you in improving processes and outcomes in the cardiac OR, contact us today!
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