Why was the myocardial infarction in my postop patient silent?

Myocardial infarction (MI) in postop patients is in fact usually silent (1,2) but what is less clear is how myocardial ischemia can occur without any symptoms.

Although use of analgesics and narcotics postop may dampen or mask chest pain or other symptoms associated with MI, other factors are also likely to play an important role, such as decreased sensitivity to painful stimuli, autonomic neuropathy (eg, in diabetes mellitus), and higher pain threshold among some patients (3).

Additional factors associated with silent MIs include cerebral cortical dysfunction since frontal cortical activation appears to be necessary to experience cardiac pain. Mental stress is also a frequent trigger for asymptomatic myocardial ischemia, infarction and sudden cardiac death (4).  High levels of beta-endorphin, an endogenous opiate, may also play a role (5).

Perhaps the most intriguing explanation for lack of symptoms is the observation that the levels of anti-inflammatory cytokines (interleukin-4 and -10)—which block pain transmission pathways and increase the threshold for nerve activation—seem to be increased in patients with silent myocardial ischemia (6).  Even more relevant to our postop patient is the finding that interleukin-10 production increases during and after major abdominal surgery and correlates with the amount of intraoperative blood loss (7). 

No wonder MIs in postop patients are often silent!

1. Devereaux PJ, Xavier D, Pogue J, et al. Characteristics nd short-term prognosis of perioperative myocardial infarction in patients undergoing noncardiac surgery: a cohort study. Ann Intern Med 2011;154:523-8. https://annals.org/aim/article-abstract/746934/characteristics-short-term-prognosis-perioperative-myocardial-infarction-patients-undergoing-noncardiac 
2. Badner NH, Knill RL, Brown JE, et al. Myocardial infarction after noncardiac surgery. Anesthesiology 1998;88:572-78. http://anesthesiology.pubs.asahq.org/article.aspx?articleid=1948483
3. Ahmed AH, Shankar KJ, Eftekhari H, et al. Silent myocardial ischemia:current perspectives and future directions. Exp Clin Cardiol 2007;12:189-96. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2359606/ 
4. Gullette EC, Blumenthal JA, Babyak M, et al. Effects of mental stress on myocardial ischemia during daily life. JAMA 1997;277:1521-6. https://jama.jamanetwork.com/journals/jama/articlepdf/416233/jama_277_19_029.pdf
5. Hikita H, Kurita A, Takase B, et al. Re-examination of the roles of beta-endorphin and cardiac autonomic function in exercise-induced silent myocardial ischemia. Ann Noninvasive Electrocardiol 1997;2:319-25. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1542-474X.1997.tb00195.x
6. Mazzone A, Cusa C, Mazzucchelli I, et al. Increased production of inflammatory cytokines in patients with silent myocardial ischemia. J Am Coll Cardiol 2001;38:1895-901. https://www.ncbi.nlm.nih.gov/pubmed/11738291
7. Kato M, Honda I, Suzuki H, et al. Interleukin-10 production during and after upper abdominal surgery. J Clin Anesth 1998;10:184-8. https://www.ncbi.nlm.nih.gov/pubmed/9603586 

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Why was the myocardial infarction in my postop patient silent?

My patient with chronic pain complains of difficulty sleeping. Would improving her sleep hygiene impact her pain medication requirement?

Most likely!

We should routinely assess for poor sleep as a potential impediment to adequate pain control in our patients. Substantial research supports a bidirectional relationship between pain and sleep.  That is, not only can pain disrupt sleep but sleep quality can also adversely affect pain.1   In fact, even a short-term disturbance in a stable sleep pattern may lower the pain threshold 2 and the ability to tolerate previously controlled pain.3

These observations are thought to result from activated stress responses from poor sleep hygiene which in turn produce cellular oxidative stress and inflammation of tissues and the nervous system. 4 This process can result in a vicious cycle between increasing pain and persistent insomnia.4,5  Breaking this cycle can reduce pain and improve function, among other desired outcomes.

Ongoing insomnia may also be a sign of a variety of other conditions that should be treated, such as mood disorder and sleep apnea. For example, besides standard non-pharmaceutical measures to improve sleep hygiene, continuous positive air pressure (CPAP) can reduce pain and opioid use in the setting of sleep apnea .2,6

Remember also that controlling pain with opioids in hopes of improving sleep may be counterproductive as opioids can contribute to sleep apnea.7,8  Melatonin may be a better sleep aid in this setting. 9


  1. Wei Y, Blanken TF, Van Someren EJW. Insomnia really hurts: effect of a bad night’s sleep on pain increases with insomnia severity. Front Psychiatry 2018;9:377. doi: 10.3389/fpsyt.2018.00377. https://www.ncbi.nlm.nih.gov/pubmed/30210367
  2. Charokopos A, Card ME, Gunderson C, Steffens C, Bastian LA. The association of obstructive sleep apnea and pain outcomes in adults: a systematic review. Pain Med 2018;19(suppl_1):S69-S75. doi: 10.1093/pm/pny140. https://www.ncbi.nlm.nih.gov/pubmed/30203008
  3. Sivertsen B, Lallukka T, Petrie KJ, et al. Sleep and pain sensitivity in adults. Pain. 2015;156:1433-9. https://www.ncbi.nlm.nih.gov/pubmed/25915149
  4. Iacovides S, George K, Kamerman P, Baker FC. Sleep fragmentation hypersensitizes healthy young women to deep and superficial experimental pain. J Pain. 2017;18:844-854. doi: https://doi.org/10.1016/j.jpain.2017.02.436. https://www.ncbi.nlm.nih.gov/pubmed/28300651
  5. Edwards RR, Almeida DM, Klick B, Haythornthwaite JA, Smith MT. Duration of sleep contributes to next-day pain report in the general population. Pain. 2008;137:202-7. doi: 10.1016/j.pain.2008.01.025. https://www.ncbi.nlm.nih.gov/pubmed/18434020
  6. Edwards RR, Almeida DM, Klick B, Haythornthwaite JA, Smith MT. Duration of sleep contributes to next-day pain report in the general population. Pain. 2008 Jul;137(1):202-7. doi: 10.1016/j.pain.2008.01.025. https://www.ncbi.nlm.nih.gov/pubmed/18434020
  7. Marshansky S, Mayer P, Rizzo D, Baltzan M, Denis R, Lavigne GJ. Sleep, chronic pain, and opioid risk for apnea. Prog Neuropsychopharmacol Biol Psychiatry 2018 20;87:234-244. https://www.ncbi.nlm.nih.gov/pubmed/28734941
  8. Jungquist CR, Flannery M, Perlis ML, Grace JT. Relationship of chronic pain and opioid use with respiratory disturbance during sleep. Pain Manag Nurs 2012;13:70-9. doi: 10.1016/j.pmn.2010.04.003. https://www.ncbi.nlm.nih.gov/pubmed/22652280
  9. Landis CA. Is melatonin the next “new” therapy to improve sleep and reduce pain? Sleep 2014; 37: 1405–1406. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153056/

Contributed by Paul Arnstein, PhD, RN, FAAN, Mass General Hospital, Boston, MA.

My patient with chronic pain complains of difficulty sleeping. Would improving her sleep hygiene impact her pain medication requirement?

How exactly do urinary tract infections (UTIs) cause delirium in my elderly patients?

 UTIs are often considered in the differential diagnosis of causes of delirium in the elderly. Though largely speculative, 2 possible pathophysiologic basis for this association are suggested:1-3

  •  Direct brain insult (eg, in the setting of sepsis/hypotension)
  • Indirect aberrant stress response, involving cytokines/inflammatory pathways,  hypothalamic-pituitary-adrenal [HPA] axis and sympathetic nervous system (SNS). One or both pathways can interact with the neurotransmitter and intracellular signal transduction systems underlying delirium in the brain, which may already be impaired in the elderly due to age-related or other pathologic changes.

The indirect aberrant stress pathway suggests that not only pain and discomfort (eg from dysuria) can contribute to delirium but UTI-associated circulating cytokines may also cause delirium.  Indeed, a large study of older adults undergoing elective surgery found a significant association between delirium postoperatively (postop day 2) and serum proinflammatory cytokine levels such as IL-6. 4  

The corollary is that bacteriuria is unlikely to be associated with delirium in the absence of significant systemic inflammatory response, pain or discomfort.



1.Trzepacz P, van der Mast R. The neuropathophysiology of delirium. In Lindesay J,  Rockwood K, Macdonald A (Eds.). Delirium in old age, pp. 51–90. Oxford University Press, Oxford , 2002.

2.Flacker JM, Lipsitz LA. Neural mechanisms of delirium: current hypotheses and evolving concepts. J Gerontol A Biol Sci Med Sci. 1999; 54: B239–B246 https://www.ncbi.nlm.nih.gov/pubmed/10411009

3. Maclullich AM, Ferguson KJ, Miller T, de Rooij SE, Cunningham C. Unravelling the pathophysiology of delirium: a focus on the role of aberrant stress responses. J Psychosom Res. 2008;65:229–38. https://www.ncbi.nlm.nih.gov/pubmed/18707945

4. Vasunilashom SM, Ngo L, Inouye SK, et al. Cytokines and postoperative delirium in older patients undergoing major elective surgery. J Gerontol A Biol Sci Med Sci 2015;70:1289-95. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4817082/pdf/glv083.pdf

Contributed by Henrietta Afari MD, Mass General Hospital, Boston, MA

How exactly do urinary tract infections (UTIs) cause delirium in my elderly patients?

“In my patient with abdominal pain, what physical exam finding can help differentiate abdominal wall from intra-abdominal sources of pain?”

Carnett’s sign (described by a surgeon, J.B. Carnett, in 1926) is a physical exam finding that helps differentiate abdominal wall or psychogenic pain from intra-abdominal sources of pain.

The test is considered positive when, upon locating the tender abdominal spot, the patient’s pain worsens on tensing of the abdominal wall muscles by lifting the head and shoulders from the bed or by raising both legs with straight knees. Conversely, if the pain decreases with this maneuver, an intra-abdominal source is more likely1,2. Sensitivity of ~80%, specificity of ~90%, positive likelihood ratio of 2.6 and negative likelihood ratio of 0.2 have been reported in various studies. 3,4,5

A positive Carnett’s sign should broaden the differential of abdominal pain to include: hernias, irritation of intercostal nerve roots, rectus sheath hematomas, myofascial pain, anterior cutaneous nerve entrapment or ACNES (also see another P4P pearl 6) and psychogenic pain. In the appropriate clinical setting,  local corticosteroids or anesthetic injections, or the application of hot or cold packs may be therapeutic. 2,7

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  1. Carnett JB. Intercostal neuralgia as a cause of abdominal pain and tenderness. J Surg Gynecol Obstet 1926; 42:625-632.
  2. Bundrick JB, Litin SC. Clinical pearls in general internal medicine.  Mayo Clin Proceedings 2011;86: 70–74.  https://mayoclinic.pure.elsevier.com/en/publications/clinical-pearls-in-general-internal-medicine-2.
  3. Takada T, Ikusaka M, Ohira Y, et al. Diagnostic usefulness of Carnett’s test in psychogenic abdominal pain. Intern Med 2011;50:213-17. https://www.jstage.jst.go.jp/article/internalmedicine/50/3/50_3_213/_article
  4. Kamboj Ak, Hoverten P, Oxentenko AS. Chronic abdominal wall pain: a common yet overlooked etiology of chronic abdominal pain. Mayo Clin Proc 2019;94:139-44. https://www.mayoclinicproceedings.org/article/S0025-6196(18)30852-8/pdf
  5. Sweetser S. Abdominal wall pain: a common clinical problem. Mayo Clin Proc 2019;94:347-335.https://www.mayoclinicproceedings.org/article/S0025-6196(18)30671-2/fulltext  
  6. https://pearls4peers.com/2015/11/18/whats-acnes-anterior-cutaneous-nerve-entrapment-syndrome/
  7. Suleiman S , Johnston DE.  The abdominal wall: an overlooked source of pain. Am Fam Physician 2001; 64: 431-8. https://www.ncbi.nlm.nih.gov/pubmed/11515832

Contributed in part by Brad Lander MD, Mass General Hospital, Boston, MA.


“In my patient with abdominal pain, what physical exam finding can help differentiate abdominal wall from intra-abdominal sources of pain?”