My patient with diverticular bleed has now developed signs of bowel ischemia with abdominal pain and sepsis after transcatheter colic artery embolization. Is bowel ischemia common after embolization of lower gastrointestinal (GI) arteries?

It may be more common than we think! Reported rates of bowel ischemia following lower GI artery embolization have been as high as 22% (1,2). For this reason, it is prudent to closely monitor for signs of bowel ischemia and infection in patients who undergo embolization to control lower GI bleeding.

In some cases, ischemia of the bowel appears to be mild enough to be treated conservatively, while in other cases bowel infarction with surgical intervention has been necessary (1).  One case report described signs of infection (including fever, abdominal tenderness and leukocytosis) 2 days after arterial embolization in a patient who was treated conservatively (3), while another described “sepsis” 6 days post procedure with bowel wall ischemia requiring surgical resection (1). 

Bowel injury leading to a septic picture following embolization of lower GI arteries should not be surprising given the expected capillary hypoperfusion and risk of tissue hypoxia.  Compared to embolization for upper GI bleed, lower GI embolization may place the patient at higher risk of bowel ischemia bowel ischemia due to lack of a rich collateral blood supply (1).  Older patients may also have mesenteric artery atherosclerotic disease or low cardiac output,  further compromising the collateral blood flow (3).  

At a more molecular level, hypoxia leads to the activation of hypoxia-inducible factor (HIF-1), which plays an important role in inducing gut injury. In fact, deletion of HIF-1a in mice prevented shock-induced intestinal permeability and bacterial translocation that ultimately led to bacteremia (4). 

As for preventing embolization-induced bacteremia, although antibiotics are used for liver and spleen embolization prophylaxis, their role in colic angioembolization is unclear (5).  

Bonus Pearl: Did you know that some of the earliest angioembolizations were performed during the Vietnam War to stop bleeding from bullet injuries? (6)

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References:

  1. Gady, J, Reynolds, H., & Blum, A. Selective arterial embolization for control of lower gastrointestinal bleeding: Recommendations for a clinical management pathway. Current Surg 2003; 60: 344-347. https://www.sciencedirect.com/science/article/abs/pii/S0149794402007493
  2. Rossetti A, Buchs NC, Breguet R, et al. Transarterial embolization in acute colonic bleeding: review of 11 years of experience and long-term results. Int J Colo Dis 2013;28:777-782. https://link.springer.com/article/10.1007/s00384-012-1621-5
  3. Shenoy, S, Satchidanand, S, & Wesp S. Colonic ischemic necrosis following therapeutic embolization. Gastrointest Radiol 1981, 6: 235-237. https://link.springer.com/article/10.1007/BF01890256
  4. Vollmar, B., & Menger, M. Intestinal ischemia/reperfusion: Microcirculatory pathology and functional consequences. Langenbeck Arch Surg 2011; 396: 13-29 https://link.springer.com/article/10.1007%2Fs00423-010-0727-x 
  5. Ryan, J. Mark, Ryan, Barbara M, & Smith, Tony P. Antibiotic prophylaxis in interventional radiology. JVIR 2004; 15: 547-556. https://www.sciencedirect.com/science/article/pii/S1051044307603248
  6. Nolan, T, Phan H, Hardy A, et al. Bullet embolization: Multidisciplinary approach by interventional radiology and surgery. Semin Interven Radiol 2012, 29: 192-6. https://www.ncbi.nlm.nih.gov/pubmed/23997411 

Contributed by Hannah Ananda Bougleux Gomes, Medical Student, Harvard Medical School, Boston, MA.

My patient with diverticular bleed has now developed signs of bowel ischemia with abdominal pain and sepsis after transcatheter colic artery embolization. Is bowel ischemia common after embolization of lower gastrointestinal (GI) arteries?

My previously healthy 55 year old patient is admitted with a respiratory tract infection and a respiratory rate of 22 breaths/min. Should I be concerned?

Any respiratory rate (RR) greater than 20/min in an adult patient may be cause for concern, particularly in the setting of potentially serious disease and absence of an obvious cause such as pain or fever.

Our patient’s RR is outside the commonly cited normal range of 12-20/min. It indicates increased alveolar ventilation which may in turn be caused by hypoxia, hypercapnea, or metabolic acidosis, all portending possibly poor outcome, if left untreated.It’s no surprise that an abnormal RR is often the first sign of clinical deterioration.2 RR is also the least likely of the vital signs to be affected by polypharmacy (eg, NSAIDs affecting temperature, beta-blockers affecting heart rate and blood pressure). 

Another reason for not dismissing an RR of 22 in our patient is the common practice of guessing rather than measuring the RR by healthcare providers in part likely due to the  more “labor-intensive” nature of measuring RRs compared to other vital signs and lack of appreciation for its importance in assessing severity of disease. 1 Of note, in an experimental study of doctors viewing videos of mock patients, over 50% failed to detect abnormal RR when using the “spot” technique of estimating without a timer.3 Even when presented with a RR of 30/min, over 20% of doctors reported it as normal (12-20/min)!

Final tidbit: Do you want to know what a RR of 20/min really feels like? Take a breath every 3 seconds.  If you are like most, it doesn’t feel “normal”!

References
1. Cretikos MA, Bellomo R, Hillman K. Respiratory rate: the neglected vital sign. MJA 2008;188:657-59. https://www.ncbi.nlm.nih.gov/pubmed/18513176
2. Flenady T, Dwer T, Applegarth J. Accurate respiratory rates count: So should you! Australas Emerg Nurs J 2017; 20:45-47. https://www.ncbi.nlm.nih.gov/pubmed/28073649
3. Philip KEJ, Pack E, Cambiano V et al. The accuracy of respiratory rate assessment by doctors in a London teaching hospital: a cross-sectional study. J Clin Monit Comput2015;29:455-60. https://www.ncbi.nlm.nih.gov/pubmed/25273624

My previously healthy 55 year old patient is admitted with a respiratory tract infection and a respiratory rate of 22 breaths/min. Should I be concerned?