Management of the Postsurgical CABG Patient
Management of the Postsurgical CABG Patient
Coronary artery bypass graft (CABG) surgery is a recommended treatment for coronary heart disease (CHD). In the United Kingdom, around 2.7 million people have been diagnosed with this condition (NHS, 2012). The aim of surgery is to relieve angina and shortness of breath by improving the flow of blood to the heart (Parry et al., 2010). These symptoms cause severe discomfort and distress as well as limit the amount and type of physical activity a patient may engage in.
Surgery helps patients attain a higher quality of life referred to as satisfaction with life and optimum physiological as well as psychological functioning (Abdallah et al., 2013). CABG is also associated with a reduced risk of mortality from myocardial infarction (Greason & Schaff, 2010). The success of the procedure rests in part on the postoperative management of pain, blood glucose, and fluid balance. The related interventions under these domains enable healing and full recovery.
Postoperative pain occurs in CABG because of tissue damage from body positioning during the long procedure. It is also caused by surgical incisions, dissections, retraction, electrocautery, and the placement of chest tubes, catheters, and wires (Sethares, Chin & Costa, 2013). Patients who underwent saphenous vein or mammary artery harvesting further experience postoperative pain of greater intensity than those who did not. Among discharged patients, pain is one reason they seek to be readmitted. While pain is a typical effect of surgery, however, it can be managed effectively.
On the other hand, most CABG patients also have type II diabetes that is often uncontrolled. Surgery is a stressor. In conjunction with drugs administered during and after the procedure, it induces insulin resistance and hence hyperglycaemia in the postoperative period (Breithaupt, 2010). It requires management because of the negative impact on tissues and healing. Lastly, fluid balance must be maintained to prevent harm from the fluid overload that typically occurs after surgery (Ricci & Romagnoli, 2010). These are potential but preventable complications.
The need to manage pain. Among post-CABG patients, moderate to severe pain is a commonly reported symptom that persists weeks after discharge. Pain management is important as Parry et al. (2009) report that “unrelieved acute pain can precipitate adverse events, such as pulmonary and cardiovascular dysfunction” (p. E13). Patients alter the depth and frequency of their breathing to cope with pain but the pattern results in inadequate ventilation. Pain also makes deep breathing, coughing exercises, position changes, and early ambulation difficult. The net effect is an increased risk for atelectasis and respiratory infection (Sattari et al., 2013).
Further, poor postoperative pain control is associated with suboptimal cardiovascular outcomes. Moderate to severe pain activates the sympathetic response causing a rise in heart rate, blood pressure, and cardiac output (Sethares, Chin & Costa, 2013). These significantly increase the cardiac workload and myocardial oxygen consumption. Hypoxaemia and cardiac ischaemia may occur with the imbalance in the demand for and supply of oxygen. Organ dysfunction may occur as a consequence while inadequate tissue perfusion delays the process of wound healing (Parry et al., 2010).
In addition, immobility resulting from uncontrolled pain leads to blood stasis that increases the risk of deep vein thrombosis. The inability to ambulate also leads to muscle deconditioning and wasting (Sattari et al., 2013). As the return of normal bladder and bowel functions depends in part on early postoperative mobility, pain further impacts the processes of elimination. Moreover, ineffective analgaesia deprives patients of rest and sleep which contributes to fatigue. It negatively affects appetite and thus contributes to poor nutrition. Lastly, unmanaged postsurgical pain increases the probability of experiencing chronic pain (Sethares, Chin & Costa, 2013).
The above complications highlight the need for adequate analgaesia. However, there are several factors contributing to poor pain management. Pain is a subjective experience. Hence, the level of pain can only be assessed accurately by asking the patient. Delayed pain assessment and analgesic administration leads to breakthrough pain that does not respond to the usual dose (Power & McCormack, 2008). This requires an increase in dose and the use of a short-acting pain reliever. In addition, analgesics can have life-threatening side effects when given in bolus doses. This fact plus the fear that patients will develop addiction especially to opioid analgesics result in underdosing (Sattari et al., 2013).
Patient-controlled analgesia. The use of patient-controlled analgesia (PCA) resolves the aforementioned factors to ineffective pain management. This technology delivers predetermined doses of a pain-relieving drug typically through an intravenous pump (Surprise & Simpson, 2013). To obtain the drug, the patient only needs to push the button. The needleless transdermal patch has recently been improved so that it can be used for postoperative pain. The delivery device is applied like a patch but has a button that can be pressed. Very low levels of electric current enable a faster and more accurate drug delivery through the skin compared to the traditional patch (Power & McCormack, 2009).
One benefit of using PCA is patient control over dose and timing (Surprise & Simpson, 2013). Based on need, the patient can press the button for a timely dose of pain reliever whereas in the traditional mode of administration, the patient has to wait for the nurse to give the drug. Another benefit is better pain control. Timeliness eliminates the experience of breakthrough pain that is more difficult to treat. A third benefit is the reduction of side-effects (Power & McCormack, 2009). Each PCA dose is smaller than a bolus dose. Though the pump may be used more frequently, there is a lesser risk for adverse effects.
Fentanyl and side effects. Fentanyl is one type of analgesic administered via PCA. It is an opioid and acts by binding with the opioid receptors in the central nervous system (Hong et al., 2009). It modifies patient perception of pain and the attendant emotional response. Fentanyl has several side effects that require monitoring. Nausea, vomiting, and urine retention are common reasons for patients to discontinue the medication (Wolff et al., 2012). Dizziness, sedation, and somnolence pose a threat to patient safety (Hong et al., 2009). Accidental high doses cause respiratory depression that may be fatal. Although uncommon, arrhythmia, hypotension, and urine retention may occur (Jiang et al., 2009).
Blood Glucose Management
The need for blood glucose control. In patients with uncontrolled type II diabetes mellitus (DM), chronic hyperglycaemia causes the desensitization of or injury to pancreatic beta cells leading to impairment in insulin secretion (Papak & Kansagara, 2012). Prolonged hyperglycaemia causes damage to tissues through oxidative stress giving rise to various degrees of organ damage (Breithaupt, 2010). During CABG, one of the body’s responses to stress from surgical insult is gluconeogenesis. At the same time, steroid administration pre- and post-surgery reduces insulin production and causes cellular resistance to the hormone (Hui, Kumar & Adams, 2012). The result is exacerbated hyperglycaemia.
Tissue damage from hyperglycaemia precipitates many adverse outcomes and highlights the need for good glucose control. Giakoumidakis et al. (2013) state that uncontrolled blood glucose correlated in studies with “complications such as infections, surgical wound contamination and compromised wound healing, acute myocardial infarction, atrial fibrillation, delayed extubation and adverse renal and respiratory events” (p. 146). There is also a high risk for post-operative sepsis and cerebral ischaemia (Emam et al., 2010). Thus, a higher mortality rate is noted among post-CABG patients with uncontrolled diabetes compared to non-diabetics.
Hyperglycaemia further precipitates a heightened inflammatory response in the newly-grafted blood vessels (Lazar, 2012). This causes thrombosis that compromises graft patency and requires revascularization to ensure continued viability. In addition, sternal wound healing has been found to be delayed among patients with uncontrolled type II DM (Emam et al., 2010). Further, hyperglycaemia within the immediate 48 hours following surgery is linked with an increased incidence of deep post-surgical wound infection among post-CABG patients (Breithaupt, 2010).
Adequate circulation and good immune response are indispensable elements of wound healing (Ead, 2009). The blood carries with it platelets that facilitate clotting. It transports oxygen via the haemoglobin in red blood cells (RBCs). Also travelling through the blood are macrophages and white blood cells (WBCs) responsible for eliminating wound contaminants such as bacteria that can cause prolonged inflammation and infection (Papak & Kansagara, 2012). Glucose, vitamins, and minerals also pass through the blood for use in tissue regeneration and wound healing.
With hyperglycaemia in type II DM, there is poor microvascular circulation because of blood vessel constriction as well as deviation from the normal immune response (Giakoumidakis et al., 2013). The wound bed is then deprived of oxygen and nutrients. Inflammatory factors cause the body’s initial reaction to injury, namely inflammation. Because chemotaxis – the process by which macrophages and WBCs are attracted to the wound site – is diminished during hyperglycaemia, inflammation becomes prolonged (Lazar, 2012). This is ideal for bacterial proliferation and infection. It also prevents progress to wound regeneration and complete healing. Steroid-induced immune suppression further heightens these negative outcomes (Hui, Kumar & Adams, 2012).
On the other hand, adequate insulin has many protective effects. It reduces inflammation, prevents infection, promotes the lysis of blood clots, potentiates the functioning of endothelial cells that line the blood vessels, improves blood flow through the myocardium, and prevents the death of cardiac muscle cells (Papak & Kansagara, 2012). It is therefore recommended to give post-surgical CABG patients insulin to reduce blood glucose levels down to within the normal range. This aim, in conjunction with preventing hypoglycaemia as a side effect, requires periodic monitoring of glucose levels and the timely administration of insulin.
Diabetic medications. Actrapid, Novarapid, and Lantus are types of insulin used for blood glucose management. They are substitutes for the natural insulin produced minimally by the body with type II DM. They mimic the action of human insulin by stimulating the cellular uptake of glucose, reducing abnormally high levels in the blood, and preventing hyperglycaemia (Arnolds et al., 2011). Lantus, in particular, promotes glucose absorption by fat and skeletal muscle cells while also preventing gluconeogenesis by the liver (Evans, Schumm & King, 2011). The three types of insulin differ in terms of onset of action and duration. Lantus is long acting, Actrapid is short acting, and Novarapid is ultra-short acting.
Importance of using the glucose sliding scale. Achieving normal blood sugar levels is more difficult to attain and maintain in post-CABG patients with type II diabetes. Greater amounts of insulin are also needed. The reason is that steroids, namely corticosteroids and catecholamines, are administered for their protective effects such as reducing the risk for haemorrhage and atrial fibrillation (Cappabianca et al., 2011). As mentioned above, steroids impair the production of and body sensitivity to insulin. Each administration causes significant fluctuations in the patient’s blood glucose levels.
Given the clinical challenges in the post-CABG patient, the use of a protocol-guided sliding scale promotes optimum glucose management. In this system of insulin administration, the degree of change in previous and current blood glucose readings as well as the degree of insulin resistance is used to determine the rate of infusion (Hui, Kumar & Adams, 2012). Thus, the effect of steroids on blood sugar is taken into account as compared to when the current level of glucose is the sole parameter used to determine dose. Further, appropriate monitoring prevents hypoglycaemia and its adverse effects.
Fluid Management
The need to maintain fluid balance. Fluid overload is a frequent occurrence post-CABG surgery (Ricci & Romagnoli, 2010). Prior to and during the procedure, hypervolaemia is brought about by more than adequate fluid replacement totalling as much as and even exceeding four litres. Following surgery, a similarly excessive intravenous administration of crystalloid fluid expanders also causes fluid overload. Blood loss is common during CABG surgery and fluids are used to correct the resulting hypovolaemia, hypotension, oliguria, and insufficient tissue oxygenation (Bosch et al., 2013).
Moreover, a systemic inflammatory response is noted among bypass surgery patients. With the increased permeability of capillaries, fluids shift into the extravascular space (Gandhi et al., 2012). It also should be noted that patients undergoing CABG are often critically ill with heart or kidney failure and hence already have pre-existing hypervolaemia. As a result, pre-surgery fluid overload is aggravated. Indicators of hypervolaemia include peripheral oedema, weight gain, pulmonary congestion, heart congestion, haemodilution, and hypoxaemia (Morin et al., 2011).
Hypervolaemia is implicated in many adverse events and thus warrant postoperative management. As stated by Bundgaard-Nielsen, Secher & Kehlet (2009), the “liberal administration of fluid may impair pulmonary, cardiac and gastrointestinal functions contributing to post-operative complications and prolonged recovery” (p. 843). For one, ventricular dysfunction and congestive heart failure occur as a result of organ oedema with acute kidney failure as a highly probable consequence (Morin et al., 2011). Meanwhile, respiratory congestion increases the work of breathing, alters the normal breathing pattern, and renders coughing ineffective. Hence, it predisposes the patient to atelectasis, prolonged extubation, and pulmonary infection.
Fluid overload further brings about haemodilution or an increase in the fluid portion of the blood relative to the formed elements. Haemodilution is a cause for hyponatraemia, an electrolyte imbalance that needs to be corrected through promoting the loss of excess fluids (Hernandez et al., 2013). In addition, impaired wound healing is another negative outcome of hypervolaemia (Bundgaard-Nielsen, Secher & Kehlet, 2009). Oedema reduces tissue perfusion where inadequate oxygenation inhibits the normal processes of wound health including collagen formation, capillary growth, and infection control. Lastly, there are suggestions that a positive fluid balance gives rise to oedema of the intestines which delay the return of peristalsis post-surgery (Bundgaard-Nielsen, Secher & Kehlet, 2009).
Medications for fluid management. There are several types of medications intended to reduce fluid volume and maintain electrolytes within normal levels. These include furosemide, spironolactone, and potassium chloride. Furosemide is a loop diuretic that inhibits the reabsorption of sodium and chloride in the distal and proximal tubules as well as the loop of Henle in the kidneys (Munoz & Felker, 2013; Gandhi et al., 2012). Water from the body follows the sodium and this mechanism promotes fluid loss through increased diuresis. However, an unintended consequence of loop diuretics is the loss of potassium. There are adverse outcomes that arise from hypokalaemia necessitating supplementation (Ekundayo et al., 2010). Slow-K is one example of an oral potassium chloride in extended release form used as a supplement.
Spironolactone is an alternative medication in inducing diuresis without potassium loss. It similarly stimulates the excretion of sodium, chloride, and water through renal pathways. However, it accomplishes this by inhibiting the action of aldosterone, a hormone produced in the kidney that causes the reabsorption of sodium and water on one hand and the loss of potassium on the other (Edwards et al., 2011). Thus, spironolactone generates a potassium-sparing effect. This eliminates the need for potassium replacement. However, the opposite side-effect is hyperkalaemia which needs to be monitored as it can also result in life-threatening adverse effects such as arrhythmia.
Importance of pharmacotherapy for fluid management. In quantifying the impact of hypervolaemia, one study concluded that with every 1% excess in fluid, there is a 3% increase in the patient’s mortality risk (Stein et al., 2012). One purpose of fluid management is to return the patient’s weight to baseline through diuresis starting as early as the first day post-surgery (Morin et al., 2011). This is a proactive way to prevent the aforementioned complications of fluid overload wherein symptoms may not be apparent until a few days after the procedure (Stein et al., 2012). By then, organ functioning especially of the kidneys may have already been irreversibly diminished. Fluid management promotes optimum patient outcomes and conversely reduces the likelihood of mortality.
Conclusion
The best postoperative care must be given to post-CABG patients. Critical illness combined with comorbidities and the effect of surgery warrants careful patient monitoring to prevent the many serious complications that may arise. In particular, sufficient pain management, blood glucose control, and fluid balance must be indispensable components of the care plan. Pharmacologic therapies are the pillars to preventing such complications. The aim should be to bring about the best surgical outcomes for each patient.
References
Abdallah, M.S., Wang, K., Magnuson, E.A., Spertus, J.A., Farkouh, M.E., Fuster, V., Cohen, D.J. (2013). Quality of life after PCI vs CABG among patients with diabetes and multivessel coronary artery disease: A randomized controlled trial. Journal of the American Medical Association, 310(15), 1581-1590. doi:10.1001/jama.2013.279208.
Arnolds, S., Kuglin, B., Kapitza, C., & Heise, T. (2010). How pharmacokinetic and pharmacodynamics principles pave the way for optimal basal insulin therapy in type 2 diabetes. International Journal of Clinical Practice, 64(1), 1415-1424. doi: 10.1111/j.1742-1241.2010.02470.x.
Bosch, Y., Dieri, R.A., Cate, H., Nelemans, P., Bloemen, S., Hemker, C., Mochtar, B. (2013). Preoperative thrombin generation is predictive for the risk of blood loss after cardiac surgery: A research article. Journal of Cardiothoracic Surgery, 8(154), 1-9. Retrieved from http://www.cardiothoracicsurgery.org/content/8/1/154
Breithaupt, T. (2010). Postoperative glycemic control in cardiac surgery patients. Proceedings (Baylor University Medical Center), 23(1), 79-82. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2804499/
Bundgaard-Nielsen, M., Secher, N.H., & Kehlet, H. (2009). ‘Liberal’ vs. ‘restrictive’ perioperative fluid therapy – a critical assessment of the evidence. Acta Anaesthesiologica Scandinavica, 53(7), 843-851. doi: 10.1111/j.1399- 6576.2009.02029.x
Cappabianca, G., Rotunno, C., Schinosa, L.L.T., Ranieri, V.M., & Paparella, D. (2011). Protective effects of steroids in cardiac surgery: A meta-analysis of randomized double-blind trials. Journal of Cardiothoracic and Vascular Anesthesia, 25(1), 156- 165. doi:10.1053/j.jvca.2010.03.015.
Ead, H. (2009). Glycemic control and surgery – optimizing outcomes for the patient with diabetes. Journal of Peri-Anesthesia Nursing, 24(6), 384-395. doi:10.1016/j.jopan.2009.10.003.
Edwards, N.C., Steeds, R.P., Chue, C.D., Stewart, P.M., Ferro, C.J., & Townsend, J.N. (2011). The safety and tolerability of spironolactone in patients with mild to moderate chronic kidney disease. British Journal of Clinical Pharmacology, 73(3), 447-454. doi:10.1111/j.1365-2125.2011.04102.x.
Ekundayo, O.J., Adamopoulos, C., Ahmed, M.I., Pitt, B., Young, J.B., Fleg, J.L., Ahmed, A. (2010). Oral potassium supplement use and outcomes in chronic heart failure: A propensity-matched study. International Journal of Cardiology, 141(2), 167-174. doi:10.1016/j.ijcard.2008.11.195.
Emam, I., Allan, A., Eskander, K., Dhanraj, K., Faraq, E., El-Kadj, Y., Somia, R. (2010). Our experience of controlling diabetes in the peri-operative period of patients who underwent cardiac surgery. Diabetes Research and Clinical Practice, 88(3), 242-246. doi:10.1016/j.diabres.2010.03.002.
Evans, M., Schumm-Draeger, M., Vora, J., & King, A.B. (2011). A review of modern insulin analogue pharmacokinetic and pharmacodynamics profiles in type 2 diabetes: Improvements and limitations. Diabetes, Obesity and Metabolism, 13(8), 677-684. doi: 10.1111/j.1463-1326.2011.01395.x.
Gandhi, A., Husain, M., Salhiyyah, K., & Raja, S.G. (2012). Does perioperative furosemide usage reduce the need for renal replacement therapy in cardiac surgery patients? Interactive Cardiovascular and Thoracic Surgery, 15(4), 750-755. doi:10.1093/icvts/ivs208.
Giakoumidakis, K., Eltheni, R., Patelarou, E., Theologou, S., Patris, V., Michopanou, N., & Brokalaki, H. (2013). Effects of intensive glycemic control on outcomes of cardiac surgery. Heart and Lung, 42(2013), 146-151. Retrieved from http://dx.doi.org/10.1016/j.hrtlng.2012.12.007
Greason, K.L., & Schaff, H.V. (2010). Coronary artery bypass graft surgery (CABG) for patients with diabetes and multivessel coronary artery disease: Identifying patients who would benefit with CABG and understanding the potential mechanisms involved. Coronary Artery Disease, 21(7), 402-406. doi: 10.1097/MCA.0b013e32833bfde3.
Hernandez, M.C., Hoyos, E.G., Capel, F.F., Gracia, T.R., Pascual, A.C. , Sanchez, J.M., & De La Vega, I.R. (2013). Hyponatremia in the emergency room: Characteristics, and initial diagnostic approach. Endocrine Abstracts, 32(P708). doi:10.1530/endoabs.32.P708.
Hong, J.Y., Kim, W.O., Koo, B.N., Cho, J.S., Suk, E.H., & Kil, H.K. (2010). Fentanyl- sparing effect of acetaminophen as a mixture of fentanyl in intravenous parent-/nurse- controlled analgesia after pediatric ureteroneocystostomy. Anesthesiology, 113(3), 672-677. doi: 10.1097/ALN.0b013e3181e2c34b.
Hui, M.L., Kumar, A., & Adams, G.G. (2012). Protocol-directed insulin infusion sliding scales improve perioperative hyperglycaemia in critical care. Perioperative Medicine, 1(7), 1-10. Retrieved from http://www.perioperativemedicinejournal.com/content/1/1/7.
Jiang, Z., Dai, J.Q., Shi, C., Zeng, W.S., Jiang, R.C., & Tu, W.F. (2009). Influence of patient-controlled i.v. analgesia with opiods on supraventricular arrhythmias after pulmonary resection. British Journal of Anaesthesia, 103(3), 364-368. doi: 10.1093/bja/aep172.
Lazar, H.L. (2012). Glycemic control during coronary artery bypass graft surgery. International Scholarly Research Network, 2012(292490), 1-14. doi:10.5402/2012/292490.
Morin, J.F., Mistry, B., Langlois, Y., Ma, F., Chamoun, P., & Holcroft, C. (2011). Fluid overload after coronary artery bypass grafting surgery increases the incidence of post- operative complications. World Journal of Cardiovascular Surgery, 1(2), 18-23. doi:10.4236/wjcs.2011.12004.
Munoz, D., & Felker, G.M. (2013). Approaches to decongestion in patients with acute decompensated heart failure. Current Cardiology Reports, 15(2), 335-345. doi:10.1007/s11886-012-0335-1.
National Health Service (2012). Coronary heart disease. Retrieved from http://www.nhs.uk/Conditions/Coronary-heart-disease/Pages/Introduction.aspx
Papak, J., & Kansagara, D. (2012). Management of hyperglycemia in a hospitalized patient with diabetes mellitus and cardiovascular disease. American Journal of Cardiology, 100(9Suppl), 24B-31B. doi: 10.1016/j.amjcard.2012.08.034.
Parry, M., Watt-Watson, J., Hodnett, E., Tranmer, J., Dennis, C.L., & Brooks, D. (2010). Pain experiences of men and women after coronary artery bypass graft surgery. Journal of Cardiovascular Nursing, 25(3), E9-E15. doi: 10.1097/JCN.0b013e3181cd66be.
Power, I., & McCormack, J.G. (2009). Advances in patient-controlled analgesia: The role of fentanyl ITS. Medical Devices: Evidence and Research, 1, 49-57. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/22936861
Ricci, Z., & Romagnoli, S. (2010). The issue of fluid balance and mortality. HSR Proceedings in Intensive Care and Cardiovascular Anesthesia, 2(4), 245-247.
Sattari, M., Baghdadchi, M.E., Kheyri, M., Khakzadi, H., & Mashayekhi, S.O. (2013). Study of patient pain management after heart surgery. Advanced Pharmaceutical Bulletin, 3(2), 373-377. doi: http://dx.doi.org/10.5681/apb.2013.060.
Sethares, K.A., Chin, E., & Costa, I. (2013). Pain intensity, interference and patient pain management strategies the first 12 weeks after coronary artery bypass graft surgery. Applied Nursing Research, 26(4), 174-179. Retrieved from http://dx.doi.org/10.1016/j.apnr.2013.07.005
Stein, A., de Souza, L.V., Belettini, C.R., Menegazzo, W.R., Viegas, J.R., Pereira, E.D.C., Irigoyen, M.C. (2012). Fluid overload and changes in serum creatinine after cardiac surgery: Predictors of mortality and longer intensive care stay. A prospective cohort study. Critical Care, 16(3), 1-9. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/22651844
Surprise, J.K., & Simpson, M.H. (2013). PCA: Is that patient- or provider-controlled analgesia? Journal of Radiology Nursing, 33(1), 18-22. Retrieved from http://dx.doi.org/10.1016/j.jradnu.2013.10.002.
Wolff, R.F., Aune, D., Truyers, C., Hernandez, A.V., Misso, K., Riemsma, R., & Kleijnen, J. (2012). Systemic review of efficacy and safety of buprenorphine versus fentanyl or morphine in patients with chronic moderate to severe pain. Current Medical Research & Opinion, 28(5), 833-845. doi: 10.1185/03007995.2012.678938.
