Andrew Stephen, MD
Background
Acute pancreatitis(AP) can cause significant regional and systemic inflammation. It is a truly multisystem disease process with the ability to lead to derangements in each organ system. In the 1970s Ranson first described impaired gas exchange and hypoxia early in the presentation of patients with AP despite their chest x-rays appearing fairly clear. This supported the concept that AP was leading to microscopic changes in the lungs through cytokine response and inflammation. Similarly, we have also begun to understand in the last decade that AP and sepsis lead to acute kidney injury not just by hypoperfusion and a prerenal state but also through the inflammatory burden directly on the organ. Here we will review some of the key aspects of the supportive care of ICU patients with AP. This is not a place for review of surgical approaches or timing of operation.
Grading of AP, scoring systems
An international symposium was convened in 1992 in Atlanta to further define and classify AP. Mild AP is a self limited disease with minimal to no organ dysfunction. Patients usually recover uneventfully and rarely need the ICU. Severe AP(SAP) involves organ dysfunction, prolonged ICU stays, and a significant mortality, up to 20% or greater depending on the time of publication and the patient population in the series. AP has been described as having three phases of pathophysiology. The third phase progresses from local inflammation to activation of the systemic immune system and remote organ dysfunction-SAP.
Ranson’s score – Involves collecting data points at presentation and 48 hours which is a limitation. Does cover issues in each key system-pulmonary, cardiovascular, renal, but these data points are not reviewed until the 48 hour point. Sensitivity, specificity to predict SAP 75%, 77% in metaanalysis. Original paper:
Prognostic signs and the role of operative management in acute pancreatitis.
Ranson JH, Rifkind KM, Roses DF, Fink SD, Eng K, Spencer FC. Surg Gynecol Obstet. 1974 Jul;139(1):69-81.
BISAP – Bedside index for severity of acute pancreatitis. Measured on presentation. BUN, mental status, SIRS, age, pleaural effusions. 0-5 points. Key advantage is how simple it is to tabulate. 0-2 points with mortality < 5%, 3-5 points with mortality >15%.
CTSI – Computed tomography severity index. Residents should become facile at reading their own CT scans to assess CTSI. CTSI is graded by number and size of peripancreatic fluid collections and percentage of necrosis.
A 2010 review of Ranson’s, BISAP, CTSI, APACHE II in AP patients and how well they predict organ failure, complications, and mortality in acute pancreatitis.
Fluid management
SAP can lead to myocardial dysfunction centrally. Even more frequently it leads to significant and sometimes massive capillary leak from loss of endothelial integrity and poor oncotic pressure. There is often also loss of vasomotor tone in a distributive fashion similar to with sepsis. Degree of hypovolemia can be underestimated as patients have often had little intake in the period leading up to presentation. Good, early fluid resuscitation may reduce local and systemic inflammation by improving pancreatic perfusion as the organ has a vulnerable microcirculation.
-Start with a 1-2 liter bolus of crystalloid, may need up to 5 liters or more in first 6 hours(alert chief resident and attending if ongoing fluid requirement)
-Must reassess frequently-UOP, HR, MAP, consider more advanced HD monitoring
Nutrition
Dogma used to suggest holding on feeding patients with SAP due to concern for intolerance or stimulating more pancreatic inflammation. More recent evidence suggests early feeding(within 48-72 hours) of SAP patients reduces complications. Enteral feeding was a level I-B recommendation in the 2013 IAP/APA Acute Pancreatitis Guidelines based on two metaanalyses showing reductions in the following:
-infections
-multi-organ failure
-need for surgery
-mortality
2013 Guidelines:
Still one must use clinical judgment in feeding these patients as there are some scenarios where enteral feeding remains inappropriate
-concern for abdominal compartment syndrome
-patient with massive distention, vomiting
-patient on more than a low dose of vasopressor
Lack of bowel sounds does not mean a patient cannot be fed.
Patients intolerant of nasogastric feeding may need a more distal tube placed.
Abdominal compartment syndrome
A study of almost 300 SAP patients showed that 78% had intraabdominal pressure(IAP) of at least Grade 2(>16 mm). Abdominal compartment syndrome definition:
-IAP > 20 mm
-end organ dysfunction-pulmonary, renal, and/or cardiovascular
If there is concern for IAP, measure bladder pressure with patient paralyzed.
Patient may need laparotomy for decompression if conservative measures such as NG drainage, positional management not effective.
Antibiotic use
Antibiotics tend to be overused in patients with SAP. Patients are often transferred from surrounding hospitals on antibiotics without clear indication. This is especially common when there is any degree of necrosis on CT scan. A systematic review of 14 RCTs did not show improvements in any of the following outcomes when antibiotics were given prophylactically to SAP patients:
-pancreatic infections
-other infections
-mortality
A few other misconceptions, points to discuss:
-zosyn has been shown to penetrate necrotic pancreatic tissue and pancreatic ascites-4.5 g dosing q8 hours(HPB 2006)
-there is not a defined percentage of necrosis above which antibiotic prophylaxis should be started to improve outcome
-unnecessary antibiotics may lead to higher rates of fungal infections, more complicated and more resistant gram negative organisms