Continuous percutaneous paravertebral block for minimally invasive cardiac surgery

Abstract

p OSTOPERATIVE PAIN after thoracotomy is managed by a number of modalities, including thoracic epidural analgesia (TEA), intercostal block (ICB), interpleural block, and paravertebral b l o c k y Although most regional blocks need to be inserted before surgery, Sabanathan et aP have described a technique of stripping the pleura posteriorly via the surgical incision to position a catheter in the paravertebral space after thoracotomy for infusion of local anesthetics. This technique, in some studies, has been documented to be as good as TEA, the latter being the gold standard for postthoracotomy analgesia.1 Minimally invasive direct coronary artery bypass graft surgery (MIDCABG) without the aid of cardiopulmonary bypass (CPB) is performed more frequently using a minithoracotomy. In the authors' institution, patients come in as a same day admit on the morning of surgery. These patients are extubated on the operating table at the end of anesthesia and are discharged home 48 to 72 hours later. To optimize benefits from such surgical fast-tracking, the anesthesia and analgesia have to be titrated. The authors are currently evaluating TEA for MIDCABG surgery, comparing it with continuous ICB inserted by the surgeon at the end of surgery using the technique described by Sabanathan et al. 3 It is difficult to strip the parietal pleura posteriorly adequately through the small anterior thoracotomy and to insert the catheter far enough posteriorly to position the catheter closer to the paravertebral area (Fig 1). Because ICB is initiated only at the end of surgery, the patients in this group, compared to the TEA group, required higher doses of intraoperative fentanyl (TEA = 269 _+ 120 ~g v ICB = 1,160 + 539 pg), nitroglycerin (TEA = 4,089 -+ 2,863 pg v ICB = 7,953 -+ 5,174 ~tg), and morphine (TEA = 0 v ICB = 6.3 _+ 5.8 mg) 6 as well as requiring higher end-tidal concentrations of isoflurane to achieve hemodynamic control during the intense surgical stimulation associated with thoracotomy. All of these factors may contribute to the need for postoperative ventilation. In view of this experience, the authors believe that insertion of the paravertebral block before surgical incision may facilitate early extubation. Rather than continuous infusion, multiple paravertebral injections from T1 to T8 are used for breast surgery, 4 which encompasses a similar dermatomal segment as minithoracotomy for MIDCABG. Single injections are inadequate for the 24 to 36 hours' duration of analgesia required after MIDCABG. This article reports the use of a continuous paravertebral catheter inserted percntaneously just before surgery for pain relief after MIDCABG via minithoracotomy.