Tourniquet test in Dengue hemorrhagic fever

Q: How a tourniquet test is performed in Dengue hemorrhagic fever (DHF)?

Answer: 

According to WHO 1997 classification, Dengue fever is classified into three major categories

1. Dengue Fever (DF)

2. Dengue hemorrhagic fever (DHF)

3. Dengue Shock Syndrome (DSS) 

Dengue hemorrhagic fever is characterized by plasma leakage and manifests as hemoconcentration, pleural effusion, and/or ascites - along with fever and thrombocytopenia. According to WHO guidelines, DHF requires the documentation of hemorrhagic tendency. 

One easy method is via tourniquet test. The blood pressure cuff should be inflated on the upper arm to a point midway between the systolic and diastolic pressures for 5 minutes. A positive test is described as 10 or more petechiae per 1 inch. Said that test may give false-negative results if a patient is in profound shock, or false-positive when patient is in a recovering state.

Link to WHO document is given in the reference below. 

#hematology

#infectious disease

References:

1. World Health Organization. Dengue haemorrhagic fever: Diagnosis, treatment, prevention and control, 2nd edition. WHO, Geneva 1997. http://apps.who.int/iris/bitstream/10665/41988/1/9241545003_eng.pdf (Accessed on May 18, 2020).

Hyperoxia and coronary vessels

Q: Hyperoxia causes? (select one)

A) Coronary vasoconctriction

B) Coronary vasosilatation

Answer: A

Although it is true that oxygen is an essential requirement during coronary angina, "too much oxygen" (hyperoxia) is deleterious to coronary vessels. It induces coronary vasoconstriction. In animal models, it has shown to cause microscopic foci of myocardial necrosis. Other cardiac effects of hyperoxia are reduced stroke volume, decreased cardiac output, relative bradycardia, and increase systemic vascular resistance (SVR).

Clinically this can be significant in patients who require more than 60% of oxygen on ventilator for a prolonged period.

#pulmonary

#cardiology

References:

1. Ganz W, Donoso R, Marcus H, Swan HJ. Coronary hemodynamics and myocardial oxygen metabolism during oxygen breathing in patients with and without coronary artery disease. Circulation 1972; 45:763.

2. Büsing CM, Kreinsen U, Bühler F, Bleyl U. Light and electron microscopic examinations of experimentally produced heart muscle necroses following normobaric hyperoxia. Virchows Arch A Pathol Anat Histol 1975; 366:137.

3. Lodato RF. Decreased O2 consumption and cardiac output during normobaric hyperoxia in conscious dogs. J Appl Physiol (1985) 1989; 67:1551.

Sundowning

Q: "Sundowning" can be related to nurses'  shift changes in ICU? (select one)

A) True 

B) False

Answer: A

Sundowning was first described almost 80 years ago as nocturnal dementia. It still remains one of the least understood phenomena. There have been multiple definitions described but there is no general consensus. Many factors have been identified besides patients' frail and diseased state including unfamiliar environment, noise, unstructured nurses' shift changes, and reduced staffing. It would be a misnomer to name it purely as a disease of evening time. Sundowning has been reported with shift changes at 3 PM also.

#neurology

#psychiatry

References:

1.  Cameron DE. Studies in senile nocturnal delirium. Psychiatr Q. 1941;15:47–53

2.  Jacobson S, Pies R, Katz I. Clinical Manual of Geriatric Psychopharmacology. Washington, DC: American Psychiatric Publishing, Inc.; 2007. pp. 580–586. 

3. Mace N, Rabins P. The 36 Hour Day. New York: Grand Central Publishing; 2006. pp. 234–235.

4.. Khachiyants N, Trinkle D, Son SJ, Kim KY. Sundown syndrome in persons with dementia: an update. Psychiatry Investig. 2011;8(4):275‐287. doi:10.4306/pi.2011.8.4.275

Bowel Ischemia and clinical signs

Q: Presence or absence of bowel ischemia can be quickly predicted by an experienced clinician at the bedside? (select one)

A) True

B) False

Answer: B

The objective of the above question is to emphasize the deceiving nature of bedside clinical assessment of bowel ischemia. It is extremely difficult to accurately predict bowel ischemia just based upon clinical signs alone. Actually, a study has shown that even experienced clinicians were wrong in preoperative assessment more than fifty percent of times where patients eventually have gangrenous bowel. A decision should be taken in conjunction with radiological findings.

Said that, a study has shown that despite the deceiving nature of bowel ischemia, clinical experience matters. Patients with Small Bowell Obstruction (SBO) who gets admitted to a surgical service have found to have a shorter length of stay (LOS), lower hospital bills, a shorter time to surgery, and lower mortality when compared to similar kind of patients admitted to a medical service!

#surgical-critical-care

References:

Sarr MG, Bulkley GB, Zuidema GD. Preoperative recognition of intestinal strangulation obstruction. Prospective evaluation of diagnostic capability. Am J Surg 1983; 145:176.

Oyasiji T, Angelo S, Kyriakides TC, Helton SW. Small bowel obstruction: outcome and cost implications of admitting service. Am Surg 2010; 76:687.

Pulmonary contusion

Q: Pulmonary contusions evident on CT scan but not on plain chest X-ray (CXR) have better outcomes? (select one)

A) True

B) False

Answer: A

Pulmonary contusion is one of the most deceiving clinical pictures in blunt chest trauma. It can be easily missed on initial evaluation as it gradually develops over the first 24 hours. It usually resolves in about a week. It is characteristically present as irregular, nonlobular opacification of the lung parenchyma. Unfortunately, it may not be apparent on CXR, and may require a CT scan of chest to better diagnose it. Some experts argue about its utility as non-evident CXR is usually benign and requires only clinical followup. Addition of CT scan mostly does not alter clinical management. Pain control and pulmonary toilet are usually sufficed.

#trauma

References:

1. Wanek S, Mayberry JC. Blunt thoracic trauma: flail chest, pulmonary contusion, and blast injury. Crit Care Clin 2004; 20:71.

2. Richardson JD, Adams L, Flint LM. Selective management of flail chest and pulmonary contusion. Ann Surg 1982; 196:481.

3. Deunk J, Poels TC, Brink M, et al. The clinical outcome of occult pulmonary contusion on multidetector-row computed tomography in blunt trauma patients. J Trauma 2010; 68:387.

inhaled TA in hemoptysis

A note on inhaled Tranexamic Acid (TA) in patients with frequent hemoptysis

An underutilized adjuvent treatment in ICU patients who continue to have frequent bouts of hemoptysis is the use of inhaled Tranexamic Acid (TA), an antifibrinolytic agent. This may works well in non-life-threatening hemoptysis. The dose is 500 mg/5 mL every 8 hours for up to five days. It has shown to reduce the volume of hemoptysis, faster resolution and shorter hospital stay. Unfortunately, this may not work in life-threatening hemoptysis, though giving a trial may not be a bad idea when patient is at verge of death.

#pulmonary

References:

1. Wand O, Guber E, Guber A, et al. Inhaled Tranexamic Acid for Hemoptysis Treatment: A Randomized Controlled Trial. Chest 2018; 154:1379.

2. Adams TR, Reeder JA, Alqassab F, Gilbert BW. Inhaled TXA for cases of massive hemoptysis. Am J Emerg Med 2020; 38:156.

3. Dhanani JA, Roberts J, Reade MC. Nebulized Tranexamic Acid Therapy for Hemoptysis Associated with Submassive Pulmonary Embolism. J Aerosol Med Pulm Drug Deliv 2020; 33:12.

4. Segrelles Calvo, Gonzalo et al.  Inhaled Tranexamic Acid as an Alternative for Hemoptysis Treatment. CHEST, Volume 149, Issue 2, 604

A-line air embolism

Q: Air embolism via arterial line (A-line) is more likely to occur? (select one)

A) Supine position

B) Upright position

Answer: B

Air embolism via arterial lines can be more devastating than central venous lines and may cause severe consequences such as stroke.  Air embolism via A-line usually occurs due to bubbles in the flush solution of an arterial catheter. They can travel in either direction (antegrade or retrograde) and can cause embolic damage to the brain, spinal cord, heart, or even skin. Studies have demonstrated that even 2 mL of air from radial artery can cause a clinically significant cerebral air embolism. This is due to the fact that arterial air emboli does not have a luxury to get filtered out through pulmonary capillaries. Interestingly, this risk is higher when patient is in an upright position, or of a short stature.

#procedures

References:

1. McCarthy CJ, Behravesh S, Naidu SG, Oklu R. Air Embolism: Practical Tips for Prevention and Treatment. J Clin Med. 2016;5(11):93. Published 2016 Oct 31. doi:10.3390/jcm5110093

2. Chang C, Dughi J, Shitabata P, et al. Air embolism and the radial arterial line. Crit Care Med 1988; 16:141.

3. Glenn S. Murphy, Joseph W. Szokol, Jesse H. Marymont, Michael J. Avram, Jeffery S. Vender; Retrograde Air Embolization during Routine Radial Artery Catheter Flushing in Adult Cardiac Surgical Patients: An Ultrasound Study. Anesthesiology 2004;101(3):614-619. doi: https://doi.org/

4. 2.Klein J, Juratli TA, Weise M, Schackert G. A systematic review of the semi-sitting position in neurosurgical patients with patent Foramen Ovale: how frequent is paradoxical embolism?World Neurosurg. 2018; 115:196–200. doi: 10.1016/j.wneu.2018.04.114

5. Arthur C Theodore, Gilles Clermont, Allison Dalton, MD: Indications, interpretation, and techniques for arterial catheterization for invasive monitoring. Uptodate: last updated: Jul 24, 2019.

CSF / BMI

Q: The normal cerebrospinal fluid (CSF) pressure should be adjusted with patients' body mass index to avoid false positive or false negative results? (select one) 

A) True

B) False

Answer: B

The normal CSF pressure in most healthy people is usually less than 150 mm H20. Although the upper limit up to 250 mm H20 has been described. The  CSF pressure should be measured with a manometer in a patient lying flat in the lateral decubitus position with the legs extended. 

Said that, there are many factors that can alter the CSF measurement. It includes an improper patient's position, the experience of an operator, and the degree of relaxation of a patient's other body muscles. Although patients' BMI may cause a little elevation in CSF opening pressure, studies have failed to show a strong correlation. 

#procedures

#neurology

References:

Whiteley W, Al-Shahi R, Warlow CP, et al. CSF opening pressure: reference interval and the effect of body mass index. Neurology 2006; 67:1690. 

Trauma and airway

Q: Which of the following is the direct sign of airway compromise during trauma?

A) Stridor

B) Drooling

C) Trismus

D) Odynophagia

E) Tracheal deviation

Answer: A

Securing the airway is the foremost priority in trauma as there may not be any luxury of time. A clinician needs to be very prudent in securing airway. Airway comprises during trauma can be divided into three time-sensitive classes.

• Direct signs of airway compromise
• Indirect signs of airway compromise
• Signs of developing airway compromise

Dyspnea and stridor (choice A) are the most worrisome direct signs of airway compromise. All other choices given in the above question i.e., B, C, D & E are the indirect signs of airway compromise. Signs of developing airway compromise should be watched carefully and should be under constant consideration for early securement of the airway. Those are non-superficial burns of the face or neck, bleeding noted in the oropharynx or nasopharynx, crepitus or hematoma over the neck, face or chest, change of voice and subjective sense of shortness of breath despite normal oxygen saturation.

#trauma

References:

1.  Ollerton JE. NSW Institute of trauma and injury management. North Ryde: NSW; 2007. Adult trauma clinical practice guidelines: Emergency airway management in the trauma patients

2. Talucci R, Shaikh K, Schwab C. Rapid sequence induction with oral endotracheal intubation in the multiple injured patient. AmSurg. 1988;54:185–7

3. McGill J. Airway management in trauma: An update. Emerg Med Clin N Am. 2007;25:603–22.

4. Hagberg CA. The traumatized airway: Principles of airway management in the trauma patient. In: Hagberg CA, editor. Benumof's Airway Management. 2nd ed. New York: Mosby Elsevier Inc; 2008

Diaphragm

Q: What are the three significant objectives diaphragmatic muscle serves?

Answer: Diaphragm is one of the most important muscles in the human body which maintains life. It serves three main purposes:

• It is the chief inspiratory muscle.
• It keeps a  mechanical barrier between the abdominal and thoracic cavities.
• It maintains the pressure gradient between the abdominal and thoracic cavities.

One of the objectives of the above question is to emphasize that the human body has different muscles for inspiration and expiration.

Inspiratory muscles: Diaphragm,  scalenes, external intercostals, and sternomastoids. 

Expiratory muscles:  Internal intercostals, rectus abdominus, internal and external obliques, and transversus abdominus.

Clinical significance: If on clinical exam, abdominal muscles show paradoxical movement on expiration, respiratory failure is imminent - and if a patient is on spontaneous breathing trial (SBT) while on a ventilator, it is most likely to fail liberation from ventilator.

#ventilators

#pulmonary

References:

1. Roussos C, Macklem PT. The respiratory muscles. N Engl J Med 1982; 307:786.

2. Davis J, Goldman M, Loh L, Casson M. Diaphragm function and alveolar hypoventilation. Q J Med 1976; 45:87.

3. Laroche CM, Carroll N, Moxham J, Green M. Clinical significance of severe isolated diaphragm weakness. Am Rev Respir Dis 1988; 138:862.

minimum heart rate to qualify for Torsades de pointes

Q: By definition, what should be the minimum heart rate to qualify for Polymorphic Ventricular Tachycardia (Torsades de pointes) in adults?

Answer: 100 beats per minute

Polymorphic ventricular tachycardia, popularly known as Torsades de pointes ("twisting of the points.") is defined as a ventricular rhythm faster than 100 beats per minute in adults with frequent variations of the QRS axis, morphology, or both. Although minimum heart rate required is 100 beats per minute, usually heart rate runs between 160 to 250 beats per minute.

#cardiology

References:

1. Passman R, Kadish A. Polymorphic ventricular tachycardia, long Q-T syndrome, and torsades de pointes. Med Clin North Am 2001; 85:321.

2. Khan IA. Long QT syndrome: diagnosis and management. Am Heart J 2002; 143:7.

3. El-Sherif N, Turitto G. Torsade de pointes. Curr Opin Cardiol 2003; 18:6.

wlfl classification

Q: What is 'wlfl' classification?

Answer: WIfI is a classification for threatened lower limbs. It provides the likelihood of morbidity in at-risk limbs. It was developed by the Society for Vascular Surgery. It stands for Wound/Ischemia/Foot Infection (WIfI). It is a score based classification assigned on a "none/mild/moderate/severe basis on the scale of 0 to 3. It has been validated through several studies. 

This classification recommends to put diabetic and nondiabetic patients in separate categories and the presence or absence of neuropathy be additionally noted in patients with diabetes.

Classification can be accessed in a link given in reference # 4.

#surgical-critical-care

References:

1. Armstrong DG, Mills JL. Juggling risk to reduce amputations: The three-ring circus of infection, ischemia and tissue loss-dominant conditions. Wound Medicine 2013; 1:13.

2. Zhan LX, Branco BC, Armstrong DG, et al. The Society for Vascular Surgery lower extremity threatened limb classification system based on Wound, Ischemia, and foot Infection (WIfI) correlates with risk of major amputation and time to wound healing. Journal of Vascular Surgery 2015; 61:939.

3. Mills JL Sr, Conte MS, Armstrong DG, et al. The Society for Vascular Surgery Lower Extremity Threatened Limb Classification System: risk stratification based on wound, ischemia, and foot infection (WIfI). Journal of Vascular Surgery 2014; 59:220.

4. Darling JD, McCallum JC, Soden PA, et al. Predictive ability of the Society for Vascular Surgery Wound, Ischemia, and foot Infection (WIfI) classification system after first-time lower extremity revascularizations. J Vasc Surg. 2017;65(3):695‐704. doi:10.1016/j.jvs.2016.09.055 Weblink: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5328924/

Physiologic PEEP

Q: Routine application of physiologic PEEP  at 5 to 8 cm H2O in ventilated patients decreases overall mortality?

A) True

B) False

Answer: B

Routine application of PEEP  at 5 to 8 cm H2O does not make any difference in mortality or ICU length of stay, but it decreases the incidence of ventilator-associated pneumonia (VAP), lower incidences of hypoxemia, and decreased leakage of posterior pharyngeal secretions into the lower airway.

#pulmonary

#ventilators

References:

1. Smith, RA. Physiologic PEEP. Respir Care 1988; 33:620.

2. Manzano F, Fernández-Mondéjar E, Colmenero M, et al. Positive-end expiratory pressure reduces incidence of ventilator-associated pneumonia in nonhypoxemic patients. Crit Care Med 2008; 36:2225.

3. Lucangelo U, Zin WA, Antonaglia V, et al. Effect of positive expiratory pressure and type of tracheal cuff on the incidence of aspiration in mechanically ventilated patients in an intensive care unit. Crit Care Med 2008; 36:409.

Olanzapine and smoking

Q: Olanzapine is a frequently used anti-psychotic in ICU. How it is related to a patient's smoking status? 

Answer: Half life is significantly longer in non-smokers

Olanzapine has an interesting characteristic i.e. its half life gets significantly prolonged in nonsmoker patients, maybe up to more than 50 hours!  Also, half life stays prolonged with kidney and liver insufficiency.

Another less well known effect of Olanzapine is its tendency to cause hyperglycemia.


#pharmacology


Reference:

Skrobik YK, Bergeron N, Dumont M, Gottfried SB. Olanzapine vs haloperidol: treating delirium in a critical care setting. Intensive Care Med 2004; 30:444.

Dig dosing

Q: Why Digoxin is not dialysable?

Answer: Digoxin has a unique property. It gets extensively bind to skeletal muscle and myocardium. It should be used with extreme caution once renal GFR is below 50 mL/minute. It should be used with the lowest possible dose of 0.0625 mg, once anywhere between 24 to 48 hours depending on the clinical effect and renal function. 

Digoxin is not dialyzable in any form like hemodialysis, Continuous Ambulatory Peritoneal Dialysis (CAPD), or continuous renal replacement therapy (CRRT).

#cardiology
#pharmacology


Reference:

Golightly LK, Teitelbaum I, Kiser TH, et al, eds. Renal Pharmacotherapy: Dosage Adjustment of Medications Eliminated by the Kidneys. New York, NY: Springer Science; 2013.

ADA in pleural fluid

Q: What's the utility of measuring adenosine deaminase (ADA) in pleural fluid? 

 
Answer: To differentiate between malignant and tuberculous pleurisy 

 If a situation arises where the pleural fluid is exudative, lymphocytic, but initial cytology, smear, and culture fails to document tuberculosis or malignancy, ADA can be relied on with good confidence. The usual cutoff point to make that distinction is at around 35-40 U/L. ADA is usually less than 40 U/L in malignant pleural effusions, more than 35 to 50 U/L in tuberculous pleural effusions. 

 Said that interpretation of ADA should be done in connection with clinical history, physical exam, geographic locations, and local experts.

#pulmonary

#infectious-diseases 

#oncology

​#laboratory science

References: 

1.  Liang QL, Shi HZ, Wang K, et al. Diagnostic accuracy of adenosine deaminase in tuberculous pleurisy: a meta-analysis. Respir Med 2008; 102:744. 

2.  Ogata Y, Aoe K, Hiraki A, et al. Is adenosine deaminase in pleural fluid a useful marker for differentiating tuberculosis from lung cancer or mesothelioma in Japan, a country with intermediate incidence of tuberculosis? Acta Med Okayama 2011; 65:259. 

3. Biswas B, Sharma SK, Negi RS, et al. Pleural effusion: Role of pleural fluid cytology, adenosine deaminase level, and pleural biopsy in diagnosis. J Cytol 2016; 33:159. 

4.  Sivakumar P, Marples L, Breen R, Ahmed L. The diagnostic utility of pleural fluid adenosine deaminase for tuberculosis in a low prevalence area. Int J Tuberc Lung Dis 2017; 21:697.

consumptive hypothyroidism

Q: What is consumptive hypothyroidism?

Answer:  Consumptive hypothyroidism is a form of hypothyroidism characterized by excessive degradation of thyroid hormone. This is due to ectopic production of type 3 deiodinase, which metabolizes T4 to reverse T3 and T3 to T2. 

This ectopic production signifies underlying vascular and fibrotic tumors and is found to be highly associated wiith gastrointestinal stromal tumors.

In such patients Reverse T3 (rT3) is usually high which is an inactive metabolite of thyroxine.  

#endocrinology



References:

1. Ruppe MD, Huang SA, Jan de Beur SM. Consumptive hypothyroidism caused by paraneoplastic production of type 3 iodothyronine deiodinase. Thyroid 2005; 15:1369. 

2. Maynard MA, Marino-Enriquez A, Fletcher JA, et al. Thyroid hormone inactivation in gastrointestinal stromal tumors. N Engl J Med 2014; 370:1327.

3. Schmidt RL, LoPresti JS, McDermott MT, et al. Does Reverse Triiodothyronine Testing Have Clinical Utility? An Analysis of Practice Variation Based on Order Data from a National Reference Laboratory. Thyroid 2018; 28:842. 

Doxy

Q: What is the advantage of using doxycycline in ICU?

Answer: Doxycycline is an extensively broad-spectrum antibiotic, and unfortunately less utilized in developed countries. It is from the tetracycline class. It is 

• very cost-effective
• similar intravenous to oral conversion
• no adjustment needed in renal or hepatic insufficiency
• it does not get cleared by any form of dialysis

#pharmacology

#infectious-diseases

References:

1. Heintz BH, Matzke GR, Dager WE. Antimicrobial dosing concepts and recommendations for critically ill adult patients receiving continuous renal replacement therapy or intermittent hemodialysis. Pharmacotherapy. 2009;29(5):562-577. doi: 10.1592/phco.29.5.562 

2. Lee P, Crutch ER, Morrison RB. Doxycycline: studies in normal subjects and patients with renal failure. N Z Med J. 1972;75(481):355-358. 

3. Letteri JM, Miraflor F, Tablante V, Siddiqi S. Doxycycline (Vibramycin) in chronic renal failure. Nephron. 1973;11(5):318-324.

Labs in SJS/TEN

Q: Which laboratory abnormality is more common in Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN)? 

A) lymphopenia 
B) eosinophilia


Answer: A 

 As SJS/TEN appears to be more like a reactive disease in response to drugs or underlying diseases, it may be assumed that eosinophilia would a feature of SJS/TEN. In contrast, anemia and lymphopenia, are more common in SJS/TEN. It is followed by neutropenia in about one-third of patients. The presence of neutropenia is usually associated with a poor prognosis but may go undetected due to the use of systemic steroids as a treatment. 

Eosinophilia is not very common in STS/TEN.

#dermatology
#laboratory-medicine


References:

1. Roujeau JC, Chosidow O, Saiag P, Guillaume JC. Toxic epidermal necrolysis (Lyell syndrome). J Am Acad Dermatol 1990; 23:1039. 

2. Westly ED, Wechsler HL. Toxic epidermal necrolysis. Granulocytic leukopenia as a prognostic indicator. Arch Dermatol 1984; 120:721.

effect of prone positioning on cardiac function

Q: What is the effect of prone positioning on cardiac function? (select one)

A) Increase in cardiac output

B) Decrease in cardiac output

Answer: A

 Assuming, a patient has a relatively stable cardiac function, prone position increase the cardiac output contrary to believe that sternal pressure of chest wall on the heart will decrease cardiac output. This occurs due to two mechanisms 

 1. Decrease pressure of heart on the lungs leading to increased lung recruitment, which results in increase right ventricular preload and decrease right ventricular afterload 

2. Reduction in hypoxic pulmonary vasoconstriction leading to a decrease in pulmonary vascular resistance


#pulmonary
#cardiology


References:

1. Albert RK, Hubmayr RD. The prone position eliminates compression of the lungs by the heart. Am J Respir Crit Care Med 2000; 161:1660.

2. Jozwiak M, Teboul JL, Anguel N, et al. Beneficial hemodynamic effects of prone positioning in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 2013; 188:1428.

3. Malbouisson LM, Busch CJ, Puybasset L, et al. Role of the heart in the loss of aeration characterizing lower lobes in acute respiratory distress syndrome. CT Scan ARDS Study Group. Am J Respir Crit Care Med 2000; 161:2005.

Redistribution hypothermia

Q: What is redistributive hypothermia?

Answer: Redistributive hypothermia occurs during the first hour of surgical anesthesia. During the first hour of induction or activation of a neuraxial block, the body's core temperature decreases rapidly, but this drop in body temperature is not due to direct peripheral effects of anesthetics. This drop in body temperature in the first hour of anesthesia is due to anesthetic-induced vasodilation resulting from impairment of central thermoregulatory control. This redistribution of heat leads to a significant reduction in body's core temperature, though body mean body temperature remains the same.

See weblink in reference # 1 for an open-access article and diagrammatic representations.

# Surgical-critical-care


References:

 1. Hart SR, Bordes B, Hart J, Corsino D, Harmon D. Unintended perioperative hypothermia. Ochsner J. 2011;11(3):259‐270. Weblink: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3179201/

2. Matsukawa T, Sessler DI, Sessler AM, et al. Heat flow and distribution during induction of general anesthesia. Anesthesiology 1995; 82:662.

ULBT

Q: What is upper lip bite test (ULBT)?


Answer:   A test to assess difficult video laryngoscopy

ULBT is performed prior to video laryngoscopy to assess its difficulty. It is performed by asking the patient to extend his or her jaw and cover the upper lip with their lower incisors. If the patient can fully cover their upper lip with their lower incisors, video laryngoscopy would likely to be easy.

ULBT is validated via a systematic review of 27 studies comprised of about 18,000 patients. It carries a high specificity and a high negative predictive value. The accuracy of ULBT was more than 85% in 24 out of 27 studies.

#procedures


Reference: 

Faramarzi E, Soleimanpour H, Khan ZH, et al. Upper lip bite test for prediction of difficult airway: A systematic review. Pak J Med Sci 2018; 34:1019.

Receptors of hemodynamics

Q: Blood vessels contain which of the receptors?

A) Beta-1
B) Beta-2


Answer: B

To understand the mechanism of hemodynamics, it is essential to know the main categories of receptors, their location, and their function. Most of these receptors are known for more than seven decades but still eludes clinicians at the bedside.

Alpha-1 adrenergic receptors are located in vascular walls and induce significant vasoconstriction. 

Beta-1 adrenergic receptors are mostly present in the heart and increase inotropic and chronotropic effects but minimal vasoconstriction. 

Beta-2 adrenergic receptors are present in blood vessels and induce vasodilation. 

Dopamine receptors are present in the renal, splanchnic (mesenteric), coronary, and cerebral vascular beds; stimulation of these receptors leads to vasodilation. A subtype of dopamine receptors causes vasoconstriction by inducing norepinephrine release. 

Calcium sensitizers: These agents increase the sensitivity of the myocardial contractile apparatus to calcium, causing increase myocardial contractility (eg, pimobendan, levosimendan). A subtype of calcium sensitizers is phosphodiesterase inhibitors, which increase inotropy along with vasodilation 

Angiotensin II is a vasoconstrictor that is part of the renin-aldosterone-angiotensin (RAAS) system. Stimulation of these receptors increases cytosolic calcium concentration and mediate vasoconstrictive effects as well as aldosterone and vasopressin secretion.


#hemodynamics


References:

1. AHLQUIST RP. A study of the adrenotropic receptors. Am J Physiol 1948; 153:586. 

2. Müllner M, Urbanek B, Havel C, et al. Vasopressors for shock. Cochrane Database Syst Rev 2004; :CD003709. 

3. Catt KJ, Mendelsohn FA, Millan MA, Aguilera G. The role of angiotensin II receptors in vascular regulation. J Cardiovasc Pharmacol 1984; 6 Suppl 4:S575.

cuff pressure at high altitude

Q: Cuff pressure in endotracheal tube (ETT) on transporting a ventilated patient towards a higher altitude will? (select one)

A) Rise 
B) Fall


Answer: A

When a patient is transported to higher altitude for any reason, attention should be paid to cuff pressure on ETT. Cuff pressure increases when a patient is moved to a higher altitude simply because air tends to expand at higher altitude. And, this rise can be clinically significant to cause tracheal ischemia. At least one study showed that when patients were moved from sea level to a height of 3000 feet, the mean rise in cuff pressure was 23 cm H2O. 

#pulmonary
#high-altitude-medicine
#transport-medicine


References:

1. Weisberg SN, McCall JC Jr, Tennyson J. Altitude-Related Change in Endotracheal Tube Cuff Pressures in Helicopter EMS. West J Emerg Med. 2017;18(4):624–629. doi:10.5811/westjem.2017.3.32078

2. Choi YS, Chae YR. Effects of rotated endotracheal tube fixation method on unplanned extubation, oral mucosa and facial skin integrity in ICU patients. J Korean Acad Nurs 2012; 42:116. 

3. Mann C, Parkinson N, Bleetman A. Endotracheal tube and laryngeal mask airway cuff volume changes with altitude: a rule of thumb for aeromedical transport. Emerg Med J2007;24:165–7.

4. Henning J, Sharley P, Young R. Pressures within air-filled tracheal cuffs at altitude – an in vivo study. Anaesthesia 2004;59:252–4.

ESR and ESRD

Q: What is the correlation between high erythrocyte sedimentation rate (ESR) and End Stage Renal Disease (ESRD)?


Answer: None!

Elevated ESR is a norm in ESRD patients as well as in nephrotic syndrome patients, and it does not get effected by hemodialysis either. It has no clinical relevance in this patient population and should not lead clinicians to further expensive testings. This elevation in ESR is usually independent without any underlying disease, infection or malignancy.

#nephrology


References: 

1.  Bathon J, Graves J, Jens P, et al. The erythrocyte sedimentation rate in end-stage renal failure. Am J Kidney Dis 1987; 10:34. 

2. Shusterman N, Kimmel PL, Kiechle FL, et al. Factors influencing erythrocyte sedimentation in patients with chronic renal failure. Arch Intern Med 1985; 145:1796. 

3. Arik N, Bedir A, Günaydin M, et al. Do erythrocyte sedimentation rate and C-reactive protein levels have diagnostic usefulness in patients with renal failure? Nephron 2000; 86:224.

Amio lung toxicity

Q: Why lung biopsy is not a desirable procedure to confirm Amiodarone induce pulmonary toxicity?


Answer: Risk of ARDS

For reasons not fully known, patients who are taking amiodarone are highly prone to develop acute respiratory distress syndrome (ARDS) following open or thoracoscopic lung biopsy. It should be proceeded with extreme care and only if absolutely necessary. Otherwise history, respiratory symptoms of non-productive cough, compatible pulmonary function test (PFT) and radiographic findings should be suffice enough to make a diagnosis. 

​Another way to make a probable diagnosis is to give a trial of drug withdrawal and/or systemic steroid administration.

#pulmonary
#pharmacology


References:

1. Nacca N, Bhamidipati CM, Yuhico LS, Pinnamaneni S, Szombathy T. Severe amiodarone induced pulmonary toxicity. J Thorac Dis. 2012;4(6):667–670. doi:10.3978/j.issn.2072-1439.2012.06.08 

2. Wolkove N, Baltzan M. Amiodarone pulmonary toxicity. Can Respir J. 2009;16(2):43–48. doi:10.1155/2009/282540

NMB and weight

Q: Which of the following Neuro-Muscular Blockade (NMB) should be dosed according to ideal body weight?

A) succinylcholine 
B) rocuronium 
C) vecuronium 
D) cisatracurium


Answer: C

Obesity always posses a dilemma to clinicians while dosing medications. In case of NMBs, it all depends on half-life, pharmacokinetics, pharmacodynamics, and route of elimination. As vecuronium has a prolonged duration of action, it should be given according to the ideal body weight. This tends to keep them effective without having long accumulation. Others can be given per actual body weight.

Cisatracurium has become a drug of choice in ICU as it has a relatively shorter half-life and gets spontaneous degradation at physiologic pH and temperature via Hofmann elimination in the serum.

#pharmacology


References:

1. Schwartz AE, Matteo RS, Ornstein E, et al. Pharmacokinetics and pharmacodynamics of vecuronium in the obese surgical patient. Anesth Analg 1992; 74:515. 

2. Suzuki T, Masaki G, Ogawa S. Neostigmine-induced reversal of vecuronium in normal weight, overweight and obese female patients. Br J Anaesth 2006; 97:160.

Misoprostol in Ob-gyn

Q: Misoprostol is a synthetic Prostaglandin analogue (PGE1) used an oral preparation to prevent and treat gastrointestinal mucosal damage induced by NSAIDs. What are its indications in the acute care of obstetrics and gynecology? 


Answer: Misoprostol increases uterine tone and hence decreases postpartum hemorrhage (PPH). Misoprostol alone is about 75-85% successful in inducing termination of pregnancy during the first trimester of pregnancy. With Mifepristone this efficacy increases when used as recommended. Another indication for its use is for cervical ripening before surgical procedures like DnC (Dilation and Curettage). Due to its wide-ranging applications in reproductive health, Misoprostol is on the WHO Model list of essential medicines. Its advantages over other synthetic prostaglandins are its low cost, long shelf life, lack of need for refrigeration, and worldwide availability.

#ob-gyn


Reference:

Allen R, O'Brien BM. Uses of misoprostol in obstetrics and gynecology. Rev Obstet Gynecol. 2009;2(3):159‐168.

Toxicology - nontraumatic rhabdomyolysis

Q: Over-dose of which of the following agent causes non-traumatic rhabdomyolysis? 

A) physostigmine 
B) Acetaminophen 
C) Salicylate levels 
D) Diphenhydramine 
E) Doxylamine


Answer: E

Doxylamine is an antihistamine, and its accidental over-dose is common as it is found in over-the-counter sleeping aids. This agent is unique, with property of causing nontraumatic rhabdomyolysis.

Co-ingestion of acetaminophen, salicylate, and diphenhydramine (choices B, C, and D) are common as people intend to take them with sleep-aids but none of them are known to cause nontraumatic rhabdomyolysis. Elevated CPK levels should raise the concern for Doxylamine ingestion.

Physostigmine (choice A) is neither readily available nor it causes nontraumatic rhabdomyolysis. Likelihood of its overdose from over the counter setting is very low.

#toxicology


References:

1. Mendoza FS, Atiba JO, Krensky AM, Scannell LM. Rhabdomyolysis complicating doxylamine overdose. Clin Pediatr (Phila) 1987; 26:595. 

2. Soto LF, Miller CH, Ognibere AJ. Severe rhabdomyolysis after doxylamine overdose. Postgrad Med 1993; 93:227. 

3. Frankel D, Dolgin J, Murray BM. Non-traumatic rhabdomyolysis complicating antihistamine overdose. J Toxicol Clin Toxicol 1993; 31:493. 

4. Leybishkis B, Fasseas P, Ryan KF. Doxylamine overdose as a potential cause of rhabdomyolysis. Am J Med Sci 2001; 322:48.

IPC and DVT

Q: How intermittent pneumatic compression prevents deep venous thrombosis (DVT)?



Answer:  Intermittent pneumatic compression (IPC) popularly known as SCDs (Sequential Compression Boots) prevents DVT via two mechanisms. The objective of this question is to highlight the less well know second mechanism

1. Enhance blood flow in the deep veins of the legs, and prevent venous stasis 

2.  Reduce plasminogen activator inhibitor-1 (PAI-1), thereby increase endogenous fibrinolytic activity 

#hematology


References:

1. Roberts VC, Sabri S, Beeley AH, Cotton LT. The effect of intermittently applied external pressure on the haemodynamics of the lower limb in man. Br J Surg 1972; 59:223. 

2. Comerota AJ, Chouhan V, Harada RN, et al. The fibrinolytic effects of intermittent pneumatic compression: mechanism of enhanced fibrinolysis. Ann Surg 1997; 226:306.

Prostanoids and SUP

Q: What limits the use of prostanoids (prostaglandin analogs) as stress ulcer prophylaxis in ICU?

Answer:  Prostanoids exert their SUP effect via two mechanisms. First, they inhibit gastric acid secretion by selectively reducing the ability of the parietal cell to generate cyclic adenosine monophosphate (AMP) in response to histamine. Second, they exert a cytoprotective effect by enhancing mucosal defense mechanisms.

Misoprostol is the most well-known prostanoid. Despite its effectiveness, the prostanoids are the least used SUP in ICUs. There are three reasons for it

1. There are other equally or most effective SUPs available like H2-Blockers or Proton-Pump Inhibitors.

2. There is not much evidence/data generated for their use.

3. It has a high tendency to cause diarrhea.


#gastroenterology
#pharmacology


References:

1. Wilson DE. Antisecretory and mucosal protective actions of misoprostol. Potential role in the treatment of peptic ulcer disease. Am J Med 1987; 83:2. 

2. Dajani EZ. Overview of the mucosal protective effects of misoprostol in man. Prostaglandins 1987; 33 Suppl:117.