A 52-year-old male with a history of hypertrophic cardiomyopathy is nil per oral for right heart catheterization procedure. The patient is lightly sedated and the cardiology team obtains these numbers:
Based on the systemic vascular resistance and the rest of his numbers, what would be the best choice of vasopressor for this patient?
Correct Answer: C
Systemic vascular resistance (SVR) is calculated by:
SVR = MAP - CVPCO x 80
Normal value of 800 to 1200 dynes/sec/cm5 . Since this patient’s calculated SVR is 740 dynes/sec/cm5 in addition to his history of hypertrophic cardiomyopathy, the best vasopressor to use is phenylephrine (pure alpha agonist), which would increase SVR and reflexively decrease heart rate (beneficial for someone with hypertrophic cardiomyopathy).
Reference:
A 43-year-old female presenting with urosepsis has persistent hypotension despite fluid resuscitation. You do a bedside echocardiogram on the patient showing normal biventricular function and measure an inferior vena cava size of 2.1 cm with minimal respiratory variation. Her blood pressure is 92/43 mm Hg on norepinephrine 30 µg/min, and you decide to add vasopressin 0.04 Units/min.
What is the receptor that you are targeting by adding vasopressin?
Correct Answer: A
Vasopressin is formed in the hypothalamus and released from the pituitary. The primary function of vasopressin is to regulate extracellular fluid volume, but it is also a potent vasoconstrictor. There are three different types of vasopressin receptors. V1 is a receptor located in vascular smooth muscles that couples to a G protein to cause vasoconstriction. V2 receptor is located in the renal collecting duct to increase water reabsorption in the kidneys and forming a more concentrated urine through adenylyl cyclase. V3 receptor is located in the anterior pituitary gland that also couples to a G protein to release adrenocorticotropic hormone. It has been demonstrated that vasopressin has systemic vasoconstriction effects with minimal effect on pulmonary vascular resistance and thus does not increase right ventricular afterload.
References:
A 56-year-old male with liver cirrhosis and hypertension (on angiotensin-converting enzyme inhibitors) presents to the intensive care unit postoperatively after a Whipple for pancreatic cancer. You note that he is on norepinephrine 30 µg/min, vasopressin 0.04 Units/min, and epinephrine 2 µg/min to maintain a mean arterial pressure of 58 mm Hg and heart rate 99 beats/min. His arterial line shows no pulse pressure variation. You do a bedside echocardiogram which shows hyperdynamic left ventricular function and measures inferior vena cava of 1.9 cm with <50% collapse. You want to add another agent to support his blood pressure to avoid kidney injury.
Which among the following is the best medication to add?
Correct Answer: B
Methylene blue can be used as a rescue treatment for profound vasodilatory shock in the setting of normal cardiac function. It inhibits guanylate cyclase and the production of cyclic guanosine monophosphate, which reduces a vessel’s response to nitric oxide and thus decreases smooth muscle relaxation. Methylene blue causes discoloration of urine and may interfere with pulse oximetry measurements. In this scenario, the patient has both liver dysfunction and use of an angiotensin-converting enzyme inhibitor that predisposes him to vasodilatory shock. Given his adequate cardiac function, he needs another agent to improve his systemic vascular resistance and methylene blue is a good choice. Milrinone, dobutamine, and isoproterenol decrease systemic vascular resistance and may cause hypotension. Dopamine may worsen tachycardia and thus not preferred.
A 72-year-old female who is postoperative day 3 from a small bowel resection and is unable to take oral medications yet because of high nasogastric tube output. She is hypertensive, controlled on a nitroglycerin drip for a day now.
What is the LEAST likely side effect of long-term nitroglycerin exposure?
Nitroglycerin is a parenteral nitrovasodilator drug that provides nitric oxide to induce vasodilation via the cyclic GMP pathway. Nitroglycerin provides relatively higher venodilation than arteriolar dilation as opposed to nitroprusside, which provides more arteriolar dilation. Headaches are a common side effect because of direct vasodilation; tachycardia usually results from reflex sympathetic activation. Nitroglycerin is metabolized by liver nitrate reductase, which produces a nitrite that oxidizes the ferrous iron of hemoglobin to methemoglobin. Nitroglycerin can also affect platelet aggregation by reducing the ability of platelets to adhere to damaged intima. Nitroprusside can cause cyanide toxicity, not nitroglycerin.
A 69-year-old male is admitted to intensive care unit after fourvessel coronary artery bypass grafting for hemodynamic management. Upon awakening, he is hypertensive, has a central venous pressure of 12 mm Hg, and you start him on a nitroglycerin drip to maintain normotension. He then suddenly coughs and you notice 200 mL of blood in one of the chest tubes. He becomes hypotensive, and you stop the nitroglycerin drip. As this episode continues to develop, you see his central venous pressure is now 23 mm Hg and you need to start norepinephrine for hypotension. You suspect tamponade and perform a bedside echocardiogram.
Which of the following is a specific sign for tamponade?
Correct Answer: D
Specific signs of tamponade include electrical alternans, diastolic collapse of right ventricle, and left atrial collapse. Sensitive signs for tamponade include right atrial collapse, inferior vena cava plethora, and pulsus paradoxus. Right atrial collapse can occur in either tamponade or severe hypovolemia. Right atrial collapse for more than one-third of cardiac cycle is highly sensitive and specific for tamponade. Right ventricular diastolic collapse may not occur if right ventricle is hypertrophied (such as in pulmonary hypertension) or if diastolic pressure is greatly elevated.
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