In responses to this post, I see no one else has mentioned acid-base balance. ABGs are most commonly used to assess the acid-base balance. The respiratory, cardiovascular, and renal systems work hand in hand to maintain this balance. For people with chronic renal failure, it might be helpful to see how well they are compensating. The anemia and smoking history are also correct, they will alter a pulse ox reading. However I did find a source for you that mentions the use of ABG's with CABG. Schnell, Van Leeuwen, & Kranpitz (2003) state "This group of tests is used to assess conditions such as ashtma, chronic obstructive pulmonary disease (COPD), embolism (e.g., fatty or other embolsim) during coronary arterial bypass surgery, and hypoxia". The authors also noted that ABGs are generally indicated for patients on ventilators or being weaned from ventilation (Schnell, Van Leeuwen, & Kranpitz, 2003). Ignatavicius & Workman (2002) also note that, a client is placed on the bypass machine intraoperatively, to provide oxygenation and ciruculation during an induced cardiac arrest. The client is also cooled to a hypothermic state during the procedure to reduce myocardial oxygen demand. In the postoperative care of a client who has undergone CABG, after surgery the client is transported to a post- open heart surgery unit where they will be placed on a ventilator for 3 to 6 hours. The nurse also monitors for complications of CABG that include hypothermia, hypertension, hypotension, and fluid / e-lyte imbalance, among a few other things. The nurse monitors the body temperature post-operatively and maintains rewarming procedures. If the client is rewarmed too quickly, this may lead to metabolic acidosis and hypoxia (Ignatavicius & Workman, 2002).
A pulse oximeter will not monitor for a disturbance in acid-base balance.
So far this is all I have found... I will get back to you when I get more info. Hope this is helpful!
Quote from Megsd
I am working on a case study for a pt with CAD and CHF who has just undergone a CABGx3. He has a history of chronic renal insufficiency, anemia, diabetes, smoking, hypertension. After surgery he has a Swan-Ganz catheter in place for hemodynamic monitoring, is intubated and put on a ventilator. ABGs are drawn. The question I am supposed to answer is:
"Why are ABGs necessary in the case of this patient? List two reasons why it would be inappropriate to use pulse oximetry on this patient to assess his oxygen saturation status"
I have looked in 3 textbooks and 3 sets of lecture notes and we have not covered anything about why a pulse oximetry would be inappropriate. The only things I can think of include possibly the anemia showing a low SaO2 that wouldn't reflect the PaO2 (but that I'm not sure about), or his smoking history lowering his SaO2 without lowering the PaO2. Or maybe that we want to monitor his ability to ventilate, which SaO2 won't necessarily show, since ventilation includes both O2 and CO2 levels.
Am I on the right track here? What am I missing? Thanks in advance for your help!