PHYSIOLOGY OF AGING

ANSWER TO CASE PRESENTATION QUESTION

QUESTION #1:

Q: Which of the following are potentially important to her presentation and care?

• Myocardial ischemia
• Intravascular volume depletion
• Decreased creatinine clearance
• Decreased cardiac output
• Decreased renal blood flow

A: Any or all of the above.

• Myocardial ischemia: Dyspnea may be a presenting symptom of myocardial ischemia, even in the absence of chest pain. Furthermore, this patient has a history of myocardial infarction, increasing the likelihood that the dyspnea represents myocardial ischemia. The remainder of the presentation (hypotension, pulmonary congestion, tachycardia, etc.) only increases the level of concern for an acute cardiac event, probably another MI.
• Intravascular volume depletion: This woman has been unable to obtain food or drink for two days, making volume depletion a certainty. Her hypotension and tachycardia are consistent with volume depletion, but the presence of rales suggest that IV fluids will have to be given very cautiously and could precipitate pulmonary edema. She may well require placement of a Swan-Ganz catheter in the coronary care unit for close monitoring of pressures inside the heart as fluids and possibly pressors are given.
• Decreased creatinine clearance: With her prolonged confinement to bed without oral fluids, as well as her hypotension, she may have significant prerenal azotemia (impairment of kidney function due to volume depletion).
• Decreased cardiac output: Her medication list suggests a history of congestive heart failure with systolic dysfunction (lisinopril, an afterload reducer; furosemide, a diuretic; and digoxin, a positive inotropic agent). In addition, her clinical presentation with dyspnea, hypotension, pulmonary congestion, tachycardia, and edema indicates acute cardiac pump failure.
• Decreased renal blood flow: This is an inevitable consequence of the decreased cardiac output.

Q: If she has a ventricular fibrillation arrest on the way to the E.R., and is successfully resuscitated to sinus rhythm, what considerations are important in giving lidocaine?

A: Important considerations include:

• Age
  • For lidocaine infusions, a downward dosage adjustment of 50% is appropriate for elderly people. Decreased liver perfusion and drug metabolism as well as an increased drug sensitivity in older adults result in a higher risk of drug toxicity (e.g., acute confusion, seizures).
• Decreased hepatic blood flow, resulting in decreased clearance of lidocaine.
• The presence of congestive heart failure requires a downward adjustment in lidocaine infusion rate of 50%, in addition to the effects of age per se.

Copyright 1999, 2000 David A. Gruenewald, M.D. and Kayla I. Brodkin, M.D. All rights reserved.