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Postoperative Pain Management for the Cardiac Patient
Key Points
- 1.
Inadequate postoperative analgesia and/or an uninhibited perioperative surgical stress response has the potential to initiate pathophysiologic changes in all major organ systems, which may lead to substantial postoperative morbidity. Adequate postoperative analgesia prevents unnecessary patient discomfort, may decrease morbidity, hospital lengths of stay, and thus may decrease costs.
- 2.
Pain after cardiac surgery may be intense and originates from many sources, including the incision (sternotomy or thoracotomy), intraoperative tissue retraction and dissection, vascular cannulation sites, vein-harvesting sites, and chest tubes. Achieving optimal pain relief after cardiac surgery is often difficult, yet it may be attained through a wide variety of techniques, including local anesthetic infiltration, nerve blocks, intravenous agents, intrathecal techniques, and epidural techniques.
- 3.
Traditionally, analgesia after cardiac surgery has been obtained with intravenous opioids (specifically morphine). However, intravenous opioid use is associated with definite detrimental side effects and longer-acting opioids such as morphine may delay tracheal extubation during the immediate postoperative period via excessive sedation and/or respiratory depression. Thus in the current era of early extubation (eg, fast-tracking), cardiac anesthesiologists are exploring unique options for the control of postoperative pain in patients after cardiac surgery.
- 4.
Although patient-controlled analgesia is a well-established technique and offers potential unique benefits, whether it truly offers significant clinical advantages (compared with traditional nurse-administered analgesic techniques) to patients immediately after cardiac surgery remains to be determined.
- 5.
Administration of intrathecal morphine to patients initiates reliable postoperative analgesia after cardiac surgery. Intrathecal opioids or local anesthetics cannot reliably attenuate the perioperative stress response associated with cardiac surgery that persists during the immediate postoperative period. Although intrathecal local anesthetics (not opioids) may induce perioperative thoracic cardiac sympathectomy, the hemodynamic changes associated with total spinal anesthesia make the technique unpalatable in patients with cardiac disease.
- 6.
Administration of thoracic epidural opioids or local anesthetics to patients initiates reliable postoperative analgesia after cardiac surgery. The quality of analgesia obtained with thoracic epidural anesthetic techniques is sufficient to allow cardiac surgery to be performed in “awake” patients.
- 7.
Use of intrathecal and epidural techniques in patients undergoing cardiac surgery remains extremely controversial. Concerns regard the risk of hematoma formations.
- 8.
The last decade has seen a resurgence of nerve blocks (including catheter-based techniques) in patients undergoing cardiac surgery. Recent clinical studies using intercostal, intrapleural, and paravertebral blocks indicate that these techniques may have unique clinical advantages, even when compared with traditional intrathecal and epidural techniques. The emergence of liposomal bupivacaine, which has the potential to provide clinical analgesia for 96 hours after a single injection, may revolutionize the use of single-shot nerve blocks for patients undergoing cardiac surgery.
- 9.
As a general rule, avoiding intense, single-modality therapy for the treatment of acute postoperative pain is best. The administration of two analgesic agents that act by different mechanisms (multimodal or balanced analgesia) provides superior analgesic efficacy with equivalent or reduced adverse effects.
Adequate postoperative analgesia prevents unnecessary patient discomfort, may decrease morbidity, may decrease postoperative hospital lengths of stay, and thus may decrease costs. Because postoperative pain management has been deemed important, the American Society of Anesthesiologists has published practice guidelines regarding this topic. Furthermore, in recognition of the need for improved pain management, the Joint Commission has developed standards for the assessment and management of pain in accredited hospitals and other health care settings. Patient satisfaction (no doubt linked to adequacy of postoperative analgesia) has become an essential element that influences clinical activity of not only anesthesiologists but all health care professionals.
Achieving optimal pain relief after cardiac surgery is often difficult. Pain may be associated with many interventions, including sternotomy, thoracotomy, leg vein harvesting, pericardiotomy, and/or chest tube insertion, among other interventions. Inadequate analgesia and/or an uninhibited stress response during the postoperative period may increase morbidity by causing adverse hemodynamic, metabolic, immunologic, and hemostatic alterations. Aggressive control of postoperative pain, associated with an attenuated stress response, may decrease morbidity and mortality in high-risk patients after noncardiac surgery and may also decrease morbidity and mortality in patients after cardiac surgery. Adequate postoperative analgesia may be attained via a wide variety of techniques ( Box 33.1 ). Traditionally, analgesia after cardiac surgery has been obtained with intravenous opioids (specifically morphine). However, intravenous opioid use is associated with definite detrimental side effects (eg, nausea and vomiting, pruritus, urinary retention, respiratory depression), and longer-acting opioids such as morphine may delay tracheal extubation during the immediate postoperative period via excessive sedation and/or respiratory depression. Thus in the current era of early extubation (fast-tracking), cardiac anesthesiologists are exploring unique options other than traditional intravenous opioids for the control of postoperative pain in patients after cardiac surgery. The last decade has witnessed increased use of smaller incisions by cardiac surgeons, prompting clinical investigations into the use of intercostal, intrapleural, and paravertebral blocks (with and without catheters), and the emergence of long-acting liposomal bupivacaine may revolutionize the use of these techniques. No single technique is clearly superior; each possesses distinct advantages and disadvantages. It is becoming increasingly clear that a multimodal approach and/or a combined analgesic regimen (using a variety of techniques) is the best way to approach postoperative pain in all patients after surgery to maximize analgesia and minimize side effects. When addressing postoperative analgesia in cardiac surgical patients, the choice of technique (or techniques) should be made only after a thorough analysis of the risk-benefit ratio of each technique in the specific patient in whom analgesia is desired.
Box 33.1
Techniques Available for Postoperative Analgesia
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Local anesthetic infiltration
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Nerve blocks
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Opioids
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Nonsteroidal antiinflammatory agents
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α-Adrenergic agents
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Intrathecal techniques
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Epidural techniques
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Multimodal analgesia
Pain and Cardiac Surgery
Surgical or traumatic injury initiates changes in the peripheral and central nervous systems that must be addressed therapeutically to promote postoperative analgesia and, it is hoped, positively influence clinical outcomes ( Box 33.2 ). The physical processes of incision, traction, and cutting of tissues stimulate free nerve endings and a wide variety of specific nociceptors. Receptor activation and activity are further modified by the local release of chemical mediators of inflammation and sympathetic amines released via the perioperative surgical stress response. The perioperative surgical stress response peaks during the immediate postoperative period and exerts major effects on many physiologic processes. The potential clinical benefits of attenuating the perioperative surgical stress response (above and beyond simply attaining adequate clinical analgesia) have received significant attention during the 2000s and remain fairly controversial. However, inadequate postoperative analgesia and/or an uninhibited perioperative surgical stress response clearly has the potential to initiate pathophysiologic changes in all major organ systems, including the cardiovascular, pulmonary, gastrointestinal, renal, endocrine, immunologic, and/or central nervous systems, all of which may lead to substantial postoperative morbidity.
Box 33.2
Pain and Cardiac Surgery
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Originates from many sources
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Most commonly originates from the chest wall
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Preoperative expectations influence postoperative satisfaction
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Quality of postoperative analgesia may influence morbidity
Pain after cardiac surgery may be intense, and it originates from many sources, including the incision (eg, sternotomy, thoracotomy), intraoperative tissue retraction and dissection, vascular cannulation sites, vein-harvesting sites, and chest tubes, among other sources. Patients in whom an internal mammary artery is surgically exposed and used as a bypass graft may have substantially more postoperative pain.
Persistent pain after cardiac surgery, although rare, can be problematic. The cause of persistent pain after sternotomy is multifactorial, yet tissue destruction, intercostal nerve trauma, scar formation, rib fractures, sternal infection, stainless-steel wire sutures, and/or costochondral separation may all play roles. Such chronic pain is often localized to the arms, shoulders, or legs. Postoperative brachial plexus neuropathies also may occur and have been attributed to rib fracture fragments, internal mammary artery dissection, suboptimal positioning of the patient during surgery, and/or central venous catheter placement. Postoperative neuralgia of the saphenous nerve has also been reported after harvesting of saphenous veins for coronary artery bypass grafting (CABG). Younger patients appear to be at greater risk for the development of chronic, long-lasting pain. The correlation of severity of acute postoperative pain and the development of chronic pain syndromes has been suggested (patients requiring more postoperative analgesics may be more likely to develop chronic pain), yet this link is still vague.
Patient satisfaction with quality of postoperative analgesia is as much related to the comparison between anticipated and experienced pain as it is to the actual level of pain experienced. Satisfaction is related to a situation that is better than predicted, dissatisfaction to one that is worse than expected. Patients undergoing cardiac surgery remain concerned regarding the adequacy of postoperative pain relief and preoperatively tend to expect a greater amount of postoperative pain than that which is actually experienced. Because of these unique preoperative expectations, patients after cardiac surgery who postoperatively receive only moderate analgesia will likely still be satisfied with their pain control. Thus patients may experience pain of moderate intensity after cardiac surgery yet still express very high satisfaction levels.
Potential Clinical Benefits of Adequate Postoperative Analgesia
Inadequate analgesia (coupled with an uninhibited stress response) during the postoperative period may lead to many adverse hemodynamic (tachycardia, hypertension, vasoconstriction), metabolic (increased catabolism), immunologic (impaired immune response), and hemostatic (platelet activation) alterations. In patients undergoing cardiac surgery, perioperative myocardial ischemia is most commonly observed during the immediate postoperative period and appears to be related to outcome. Intraoperatively, initiation of cardiopulmonary bypass (CPB) causes substantial increases in stress response hormones (eg, norepinephrine, epinephrine) that persist into the immediate postoperative period and may contribute to myocardial ischemia observed during this time. Furthermore, postoperative myocardial ischemia may be aggravated by cardiac sympathetic nerve activation, which disrupts the balance between coronary blood flow and myocardial oxygen demand. Thus during the pivotal immediate postoperative period after cardiac surgery, adequate analgesia coupled with stress-response attenuation may potentially decrease morbidity and enhance health-related quality of life.
Local Anesthetic Infiltration
Pain after cardiac surgery is often related to median sternotomy, peaking during the first 2 postoperative days. Because of problems associated with traditional intravenous opioid analgesia and with the nonsteroidal antiinflammatory drugs (NSAIDs) and cyclooxygenase (COX) inhibitors, alternative methods of achieving postoperative analgesia in cardiac surgical patients have been sought. One such alternative method that may hold promise is the continuous infusion of a local anesthetic.
Clinical investigations have revealed the potential benefits of using a continuous infusion of a local anesthetic in patients after cardiac surgery. Patients undergoing elective CABG via median sternotomy were randomized to either ropivacaine or placebo groups. At the end of the surgery but before wound closure, bilateral intercostal nerve injections from T1 to T12 were performed using 20 mL of either 0.2% ropivacaine or normal saline. After sternal reapproximation with wires, two catheters with multiple side openings were placed anterior to the sternum ( Fig. 33.1 ). These catheters were connected to a pressurized elastomeric pump containing a flow regulator, which allowed for the delivery of 0.2% ropivacaine or normal saline at approximately 4 mL/h. The postoperative pain management was via intravenous patient-controlled anesthesia (PCA) morphine (for 72 hours). The sternal catheters were removed after 48 hours. Total mean PCA morphine consumption during the immediate postoperative period (72 hours) was significantly decreased in the ropivacaine group (47.3 vs 78.7 mg, respectively; P = .038). Mean overall pain scores (scale ranging from 0 for no pain to 10 for maximum pain imaginable) were also significantly decreased in the ropivacaine group (1.6 vs 2.6, respectively; P = .005). Most interestingly, patients receiving ropivacaine had a mean hospital length of stay of 5.2 ± 1.3 days compared with 8.2 ± 7.9 days for patients receiving normal saline, a difference that was statistically significant ( P = .001). No difference was observed in wound infections or wound healing between the two groups during hospitalization or after hospital discharge. No complications related to placement of the sternal wound catheters or performance of the intercostal nerve blocks were encountered. The authors concluded that their analgesic technique significantly improves postoperative pain control while decreasing the amount of opioid analgesia required in patients subjected to standard median sternotomy.
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