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Postoperative analgesic techniques following cardiac surgery

Alan Dine
9 June, 2014  
A narcotic-reducing strategy involving continuous sub-muscular infusion of local anaesthetic as an intercostal/sternal block significantly improves recovery variables in post-cardiac surgery patients
Alan P Dine
I-Flow LLC,
a Kimberly Clark Company US
Cardiac surgery pain is due to a multiplicity of causes, including trauma of the surgical incision and manipulation of chest wall, tissue retraction and chest tubes. Inadequate control of pain following coronary artery bypass graft procedures may contribute to postoperative complications and delay the overall recovery of the patient. Opioid reduction strategies to limit adverse effects of these analgesic agents are becoming mandatory around the globe. The comparative effectiveness program described below evaluated the opioid-reducing capabilities of a multimodal approach to postoperative pain management, utilising a continuous infusion of local anaesthetic as the primary pain management source.
Unmet need in cardiac surgery
Despite major advances in our understanding of the pathophysiology of acute pain and the development of new analgesic and drug delivery techniques, significant numbers of patients continue to suffer from unrelieved postoperative pain.
Untreated severe postoperative pain has several deleterious effects. This is particularly relevant for patients undergoing cardiac surgery, where the under-treatment of pain may lead to comorbid conditions that slow down the recovery and extend hospital length of stay.(1–3)
Adequate pain control after cardiac surgery has become of growing concern due to the recent trend toward fast-track cardiac anaesthesia using lower narcotic doses intraoperatively. Reports suggest that many patients undergoing coronary artery bypass graft experience pain, with average visual analogue scale scores reported at 3–6 in the immediate postoperative period.(4) Postoperative pain can keep patients from participating in expected activities, such as deep-breathing exercises and getting out of bed, which foster wellness and may prevent further postoperative problems. 
Decreased respiratory movement, splinting and inability to cough can promote atelectasis and postoperative pulmonary complications. Decreased mobility caused by severe pain makes early ambulation difficult and increases the risk of thromboembolic complications. Severe pain leads to accelerated catecholamine response and plasma concentrations may be many times normal. The resultant increase in systemic vascular resistance may increase the cardiac work load and the need for higher myocardial oxygen consumption, both of which may be particularly harmful in patients with coronary arterial disease. 
The treatment of pain following cardiac surgery is often challenging due to the physical condition and age of the patient and the trauma of the procedure. Unmanaged or undermanaged pain may also result in nervous system changes which can produce permanent physical damage and amplify pain. Morphine and hydromorphone, titrated intravenously, are a primary part of the standard treatment protocol for moderate-to-severe pain following surgical procedures, but these opioids have well-documented side effects, including drowsiness, nausea and vomiting, and respiratory depression. 
These side effects can be distressing for patients who are already in severe pain and can also interfere with patient recovery and the efficient flow of patients through the hospital. The medical team must spend additional time observing patients who are experiencing side effects; the length of the patient’s stay is prolonged; and some patients need to be admitted or readmitted to the ICU/CCU while they recover from the side effects of opioids, thus adding to overall costs. 
Postoperative pain for the adult cardiac surgery patient has many facets. Pain can be caused by incisions, intraoperative tissue retraction and dissection, multiple intravascular cannulations, chest tubes left after surgery, and multiple invasive procedures that patients undergo as part of their therapeutic regimen. Pain has been pointed out as one of the primary sources of concern to ICU patients,(5,6) and similar findings have been reported for cardiac surgery patients as well.(7,8)
Data on pain location and distribution are lacking in the literature. However, due to the multidimensional aspect of postoperative pain in cardiac surgery, this point deserves emphasis.  In the cardiac surgery patient, maximal pain intensity has been shown to be moderate, yet does not diminish during the first two PODs, beginning its decline between POD 2 and 3.6 The multiple facets assimilated in the personal experience of pain warrant close attention to the pain level specified by each patient. Examination of the adverse effects of pain that may undermine the desired outcomes of cardiac surgery reaffirms the importance of patients’ postoperative pain rating.
ON-Q® Pain Relief System
Use of continuous infusions of local anaesthetics to a surgical wound site or as a continuous peripheral nerve block may have the potential to provide superior postoperative analgesia.  The use of continuous infusions of local anaesthetics with the
ON-Q® Pain Relief System (I-Flow,LLC a Kimberly Clark Company, Irvine, CA) has been shown to decrease narcotic use, patient’s perception of the level of pain and length of hospital stay in a variety of procedures including coronary artery bypass graft surgery,(1,4,9,10) orthopaedic procedures,(11) abdominal hysterectomy(12) and C-section.(13)
Overall, approximately 150 studies have been conducted with this device following various procedures. The effect of continuous infusions of local anaesthetics following a variety of surgical procedures on length of hospital stay, narcotic usage and quality of recovery has been summarised in the literature in two meta-analyses by Liu and Richman.(14,15)
Subjects (1248) were enrolled at 18 centres. Patients in the ON-Q® arm received postoperative pain management with a continuous submuscular infusion of local anaesthetic and had available supplemental opioids for breakthrough pain delivered via PCA, IV, IM or oral modalities (according to the standard of care at each institution). Patients in the control arm were treated with the standard of care at each institution for post-operative pain, including opioids delivered via PCA, IV, IM or oral modalities.  Opioid consumption, length of hospital and CCU stay, extubation time, pain reports and recovery variables were measured.
These data represent 18 evidence-based outcomes evaluations (EBOe) in patients undergoing open heart procedures. The data at each of the participating centres were collected in a retrospective fashion utilising a common case report form. A minimum of 15 patients per arm was requested from each of the centres. Patients in the ON-Q® arm received postoperative pain management with the ON-Q® device and had available supplemental opioids for breakthrough pain delivered via PCA, IV, IM or oral modalities, according to the standard of care at each institution. Patients in the control arm were treated with the standard of care at each institution for post-operative pain, which included opioids delivered via PCA, IV, IM or oral modalities. Data were obtained using a standardised data collection tool and entered into a common database for analysis. 
The ON-Q® system is an elastomeric pump system used for continuous infusions of local anaesthetics to control postoperative pain. Silver Soaker® catheters were inserted bilaterally in a submuscular fashion approximately 3cm lateral to the sternal incision from the level of the xiphoid process at the base of the subcostal margin advancing in upwards fashion below the pectoral muscles to approximately 2.5cm below the clavicle.  The local anaesthetic (either bupivacaine or ropivacaine) was infused at a rate of 2cc/hr per catheter for a period of three days. 
The results of the analysis of efficacy are illustrated in Table 1.
These data are represented as mean (standard deviation). There were no serious adverse events recorded in either group during these evaluations.  
Significant decreases in pain, opioid consumption, time to foley removal and return of bowel function and lengths of stay were found in the ON-Q® group versus control. Total opioid consumption, pain, length of hospital stay and time to extubation were all reduced (p< 0.001). 
Pain is a subjective and unpleasant result of the trauma of surgical procedures. Many factors shape an individual’s expression of pain, and adverse effects caused by current drug therapies can compromise a patient’s well-being. Effective pain management resulting in pain relief without side effects is an important outcome of care and a major hurdle on the postoperative pathway to recovery with the use of opioid based treatment protocols.
Multimodal or balanced analgesia, like that outlined in the WHO analgesic ladder, is strongly recommended for management of postoperative pain.(16) Narcotic-free postoperative pain management protocols based on a multimodal approach may aid the overall acute recovery parameters and affect long-term outcomes. The use of a multimodal narcotic reducing approach to postoperative pain management has been shown in this study to provide superior analgesia compared to the current standard of care decreasing narcotic use, pain, time to extubation, recovery variables (bladder and bowel function) and hospital length of stay. Improved pain relief using a multimodal analgesic strategy is not the sole challenge in enhancing recovery.
The use of minimally invasive surgical approaches to decrease surgical stress, and to facilitate early mobilisation, and early oral (enteral) nutrition, coupled with a narcotic reducing multimodal pain management protocol may accelerate postoperative recovery and reduce morbidity.(17) Combination regimens of multimodal analgesic techniques, coupled with regional analgesic techniques, are still being studied extensively.  This evidence-based comparative effectiveness program provides a real-world look at the addition of a narcotic reducing analgesic method to controlling pain following cardiac surgery. 
Further research into this area of pain management is warranted to provide patients with superior outcomes from surgery.
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