My postop patient now has fever with atelectasis on her chest X-ray one day after surgery. Does atelectasis cause fever?

Although fever and atelectasis often coexist during the early postop period, there is no evidence that atelectasis causes fever.

A 2011 systematic analysis of 8 published studies found that all but 1 study failed to find a significant association between postop fever and atelectasis.A 1988 study reported a significant association between postop fever during the first 48 h and atelectasis on day 4 postop, but not each postop day.2  Even in this study, however, fever as a predictor of atelectasis performed poorly with a sensitivity of 26%, specificity of 75% and accuracy of 43%.

In another study involving postop cardiac surgery patients, despite a fall in the incidence of fever from day 0 to day 2, the incidence of atelectasis based on serial chest X-rays actually  increased. 3

Experimental studies in dogs and cats in the 1960s also support the lack of a causative relationship between atelectasis and fever. 4,5 Although fever was observed within 12 hrs of placement of cotton plugs in the left main bronchus of these animals, almost all animals also developed pneumonia distal to the plug.  Antibiotic treatment was associated with resolution of fever but not atelectasis.

So if it’s not atelectasis, what’s the explanation for early postop fever? The great majority of postop fevers during the first 4 days postop are unlikely to be related to infections. Instead, a more plausible explanation is the inflammatory response to the tissue injury as a result of the surgery itself causing release of cytokines (eg, interleukin-1 and -6 and tumor necrosis factor) associated with fever. 6

References

  1. Mavros MN, Velmahos GC, Falagas ME. Atelectasis as a cause of postoperative fever. Where is the clinical evidence? CHEST 2011;140:418-24. https://www.ncbi.nlm.nih.gov/pubmed/21527508
  2. Roberts J, Barnes W, Pennock M, et al. Diagnostic accuracy of fever as a measure of postoperative pulmonary complications. Heart Lung 1988;17:166-70. https://www.ncbi.nlm.nih.gov/pubmed/3350683
  3. Engoren M. Lack of association between atelectasis and fever. CHEST 1995;107:81-84. https://www.ncbi.nlm.nih.gov/pubmed/7813318
  4. Lansing AM, Jamieson WG. Mechanisms of fever in pulmonary atelectasis. Arch Surg 1963;87:168-174. https://jamanetwork.com/journals/jamasurgery/fullarticle/561080
  5. Jamieson WG, Lansing AM. Bacteriological studies in pulmonary atelectasis. Arch Surg 1963;87:1062-66. https://www.ncbi.nlm.nih.gov/pubmed/14063816
  6. Narayan M, Medinilla SP. Fever in the postoperative patient. Emerg Med Clin Nam 2013;31:1045-58. https://www.ncbi.nlm.nih.gov/pubmed/24176478 

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My postop patient now has fever with atelectasis on her chest X-ray one day after surgery. Does atelectasis cause fever?

My patient with cirrhosis now has an upper gastrointestinal bleed (UGIB) with hepatic encephalopathy (HE). What’s the connection between UGIB and HE?

Hepatic encephalopathy (HE) may be precipitated by a variety of factors including infection, hypovolemia, electrolyte imbalance (eg, hyponatremia, hypokalemia), metabolic alkalosis, sedatives, and of course UGIB. 1-3

Ammonia is often considered to play a central role in the the pathogenesis of HE, particularly when associated with UGIB. The ammoniagenic potential of UGIB is primarily attributed to the presence of hemoglobin protein in the intestinal tract. One-half of the ammoniagenesis originates from amino acid metabolism (mainly glutamine) in the mucosa of the small bowel, while the other half is due to the splitting of urea by the resident bacteria in the colon (eg, Proteus spp., Enterobacteriaceae, and anerobes).1,2

A large protein load in the GI tract, as occurs in UGIB, may result in hyperammonemia in patients with cirrhosis due to the limited capacity of the liver to convert ammonia to urea through the urea cycle as well as by the shunting of blood around hepatic sinusoids. Recent studies, however, also implicate the kidneys as an important source of ammonia in this setting, further compounding HE.3

It’s important to stress that ammonia is not likely to be the only mediator of HE. Enhanced production of cytokines due to infection or other inflammatory states, neurosteroids, endogenous benzodiazepines, and other bacterial byproducts may also play an important role in precipitating HE.2,4-6  So stay tuned!

Bonus pearl: Did you know that proinflammatory cytokines tumor necrosis factor-alpha and inerleukin-6 increase ammonia permeability across central nervous system-derived endothelial cells? 7

 

References

  1. Olde Damink SWM, Jalan R, Deutz NEP, et al. The kidney plays a major role in the hyperammonemia seen after simulated or actual GI bleeding in patients with cirrhosis. Hepatology 2003;37:1277-85.
  2. Frederick RT. Current concepts in the pathophysiology and management of hepatic encephalopathy. Gastroenterol Hepatol 2011;7:222-233.
  3. Tapper EB, Jiang ZG, Patwardhan VR. Refining the ammonia hypothesis: a physiology-driven approach to the treatment of hepatic encephalopathy. Mayo Clin Proc 2015;90:646-58.
  4. Shawcross DL, Davies NA, Williams R, et al. Systemic inflammatory response exacerbates the neuropsychological effects of induced hyperammonemia in cirrhosis. J Hepatol 2004;40:247-254.
  5. Shawcross DL, Sharifi Y, Canavan JB, et al. Infection and systemic inflammation, not ammonia, are associated with grade ¾ hepatic encephalopathy, but not mortality in controls. J Hepatol 2011;54:640-49.
  6. Shawcross D, Jalan R. The pathophysiologic basis of hepatic encephalopathy: central role for ammonia and inflammation.Cell Mol Life Sci 2005;62:2295-2304.
  7. Duchini A, Govindarajan S, Santucci M, et al. Effects of tumor necrosis factor-alpha and interleukin-6 on fluid-phase permeability and ammonia diffusion in CNS-derived endothelial cells. J Investig Med 1996;44:474-82.

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My patient with cirrhosis now has an upper gastrointestinal bleed (UGIB) with hepatic encephalopathy (HE). What’s the connection between UGIB and HE?

Does my patient about to undergo immunosuppressive therapy need antiviral prophylaxis even if she tests positive for hepatitis B surface antibody?

The presence of hepatitis B surface antibody (HBsab) in patients who also test positive for core antibody does not necessarily confer full protection against hepatitis B virus (HBV) reactivation during immunosuppression (incidence 4.3%). 1 This is because despite having HBsab and no HB surface antigen,  a small portion of patients continue to have detectable HBV DNA in the serum and are therefore at risk of reactivation during severe immunosuppression. 2

In fact, the American Gastroenterological Association recommends against using anti-HBs status to guide antiviral prophylaxis in anti-HBc-positive patients. 1

Overall, antiviral prophylaxis may reduce the risk of HBV reactivation by 87% (C.I. 70%-94%). Antiviral drugs with a high barrier to resistance (eg, entecavir) are preferred over lamivudine.

Immunosuppressants often requiring HBV prophylaxis include: 1-3

  • B cell-depleting agents (eg, rituximab, ofatumumab)
  • Anthracycline derivatives (eg, doxorubicin, epirubicin)
  • Prednisone (4 weeks or more)
  • Tumor necrosis factor inhibitors (eg, etanercept, adalimumab, certolizumab, infliximab)
  • Other cytokine or integrin inhibitors (eg, abatacept, ustekinumab, natalizumab, vedolizumab)

Traditional immunosuppressive agents such as azathioprine, 6-mercaptopurine and methotrexate are often considered “low-risk” and do not generally require prophylaxis. 1

Fun Fact: Did you know that hepatitis B virus is very old and probably originated in birds when dinosaurs roamed the earth? 4

References

  1. Reddy KR, Beavers KL, Hammond SP, et al. American Gastroenterological Association Institute Guideline on the prevention and treatment of hepatitis B virus reactivation during immunosuppressive drug therapy. Gastroenterology 2015;148:215-19. https://www.ncbi.nlm.nih.gov/pubmed/25447850
  2. Gigi E, Georgiou T, Mougiou D, et al. Hepatitis B reactivation in a patient with rheumatoid arthritis with antibodies to hepatitis B surface antigen treated with rituximab. HIPPOKATRIA 2013;17:91-93. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3738290/
  3. Kim EB, Kim DS, Park SJ, et al. Hepatitis B virus reactivation in a surface antigen-negative and antibody-positive patient after rituximab plus CHOP chemotherapy. Cancer Res Treat 2008;40:36-38. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699087/
  4. Suh A, Brosius J, Schmitz J, et al. The genome of a Mesozoic paleovirus reveals the evolution of hepatitis B virus. Nature Communications 2013; Article no. 1791. http://www.nature.com/articles/ncomms2798
Does my patient about to undergo immunosuppressive therapy need antiviral prophylaxis even if she tests positive for hepatitis B surface antibody?

What is the association between sepsis and jaundice in patients without biliary obstruction?

Up to 20% of cases of jaundice in community hospitals may be due to sepsis and bacterial infections, often occurring within a few days of onset of bacteremia or even before other clinical features of infection become apparent. 1 

Although biliary obstruction as the cause of jaundice is usually suspected, many patients lack extrahepatic cause for their jaundice. Gram-negative bacteria (eg, E. coli) are often the culprit with intraabdominal or urinary tract infection, pneumonia, endocarditis, and meningitis sources also often cited. Hyperbilirubinemia (often 2-10 mg/dl) is commonly associated with elevated alkaline phosphatase and mild aminotransferases elevations, and usually resolves with treatment of infection.1

Although factors such as increased bilirubin load from hemolysis, hepatocellular injury, and drugs (eg, penicillins and cephalosporins) may play a role, cholestasis—likely due to cytokines such as tumor necrosis factor (TNF)α— is the predominant cause. 1  

Interestingly, anti-TNF-α antibodies block reduction in bile flow and bile salt excretion in laboratory animals2

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References

  1. Chand N, Sanyal AJ. Sepsis-induced cholestasis. HEPATOLOGY 2007;45: 230-240. https://aasldpubs.onlinelibrary.wiley.com/doi/full/10.1002/hep.21480
  2. Whiting J, Green R, Rosenbluth A, Gollan J. Tumor necrosis factor-alpha decreases hepatocyte bile salt uptake and mediates endotoxin-induced cholestasis. HEPATOLOGY 1995;22:1273-1278. https://www.deepdyve.com/lp/wiley/tumor-necrosis-factor-alpha-decreases-hepatocyte-bile-salt-uptake-and-J9rdeMQBpF
What is the association between sepsis and jaundice in patients without biliary obstruction?