Evaluation of the long-term effectiveness of extraluminal and intraluminal vasodilators in an in vitro porcine model of arterial graft spasm

Comparing the Outcomes of Different Agents to Treat Vasospasm at Microsurgical Anastomosis during the Papaverine Shortage

BACKGROUND

Papaverine remains popular for treating intraoperative vasospasm, but the recent shortage has forced surgeons to trial antispasmodic agents unproven in microsurgery but commonly used in other body areas. During this shortage, the authors have used topical lidocaine and nicardipine to break intraoperative vasospasm. This study aims to analyze the outcomes of these medications on flap complications compared with papaverine.

METHODS

All consecutive free flaps performed for breast reconstruction at a single institution were reviewed. Data collected included patient demographics, comorbidities, complications, and type of antispasmodic agent. Rates of reexploration, complications, and flap salvage were compared between patients receiving antispasmodic agents and matched papaverine controls.

RESULTS

Of the 1087 flaps treated with antispasmodic agents, nicardipine was used on 59 flaps and lidocaine was used on 55 flaps. Patients treated with lidocaine had higher body mass indexes (31.0 kg/m versus 27.4 kg/m; p = 0.001). Patients treated with nicardipine tended to be older (64.0 versus 48.5; p < 0.01) and have a history of hypertension (22.0 percent versus 10.4 percent; p = 0.08) or preoperative irradiation (32.2 percent versus 13.6 percent; p = 0.016) compared with papaverine controls. No differences in the rates of total or partial flap loss, unplanned return to the operating room, or fat necrosis were observed between any of the groups. However, the nicardipine group demonstrated a higher rate of infection (15.3 percent versus 3.4 percent; p = 0.027).

CONCLUSION

Substituting lidocaine or nicardipine for papaverine to treat vasospasm did not demonstrate an increased rate of flap loss or return to the operating room, making these medications safe and efficacious alternatives to papaverine.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

The effect of nebivolol on internal mammary artery blood flow during coronary artery bypass graft surgery

Background:

During coronary artery bypass grafting (CABG), one of the most important complications related to the internal mammary artery (IMA) is perioperative spasm. Nebivolol causes endothelium-dependent vascular relaxation by increasing nitric oxide (NO) release and prevents endothelial dysfunction in long-term use. In our study, we measured the effect of a third generation beta blocker, nebivolol, on the flow dynamics of IMA grafts.

Methods:

We recruited 90 hypertensive patients undergoing isolated CABG operation, who were divided into three groups and each group included 30 patients: Group 1 patients were under antihypertensive treatment other than beta-blockers (angiontensin-converting enzyme [ACE] inhibitors, calcium channel blockers or diuretics; monotherapy or combination therapy), Group 2 received metoprolol (50 mg/day) and Group 3 received nebivolol (5 mg/day). These antihypertensive therapies were given for at least one week before the operation and continued thereafter. IMA blood flow volume was measured for one minute just before cardiopulmonary bypass (measurement A) and before left internal mammary artery (LIMA)-left anterior descending (LAD) artery anastomosis (measurement B) in the three groups. Cardiac output measurements were also achieved simultaneously.

Results:

The measurement A results were 56.3 ± 36.2, 54.6 ± 28.1 and 66.8 ± 34.2 mL/min in Groups 1, 2 and 3, respectively (p<0.05). The measurement B results were 78.3 ± 29.6, 80 ± 28.8 and 91.1 ± 40.8 mL/min in Groups 1, 2 and 3 (p<0.05), respectively. There were no differences in cardiac outputs among the groups; 5.2 ± 1.4, 5.0 ± 1.6 and 5.3 ± 1.1 L/min (p>0.05). While the cardiac outputs were similar within the three groups, the IMA free flow volume was higher in the nebivolol group after local papaverine use.

Conclusion:

Nebivolol might represent a good choice in hypertensive patients undergoing cardiac surgery by preventing perioperative myocardial hypoperfusion which increases early morbidity and mortality.

Preventing gastroepiploic artery spasm: papaverine vs calcium channel blockade

The gastroepiploic artery (GEA) is a highly vasoactive artery gaining wider acceptance as a conduit for coronary artery bypass surgery. A variety of agents are used to dilate the GEA prior to grafting; however, little is known about the duration of their effect in the immediate postoperative period. This study evaluated three calcium channel blockers and papaverine in preventing graft spasm.

METHODS

Porcine GEA segments (10-12 cm in length) were connected to a computer-controlled perfusion system with a constant in-flow pressure and distal resistance to simulate bypass flow (80-100 ml/min). Norepinephrine (NE; 10(-9) to 10(-5) M) was given in incremental doses at baseline before the vasodilator, immediately after (0 hr), and again at 2 hr after the vasodilator. Changes in flow and ED50 were recorded. Group INT (N = 25) received papaverine (PAP), diltiazem, nifedipine (NFP), or verapamil (VPL) intraluminally, while group EXT (N = 25) received the same dilators externally.

RESULTS

All arteries showed dose-dependent vasoconstriction to NE prior to treatment. Immediately after receiving the vasodilator, arteries in both groups (INT and EXT) showed initial protection against NE-induced spasm with the exception of arteries receiving NFD externally. However, at 2 hr, for group INT, only VPL and NFD prevented NE-induced graft spasm (VPL: 40.4 +/- 6.8 ml/min vs 17.9 +/- 3.3 ml/min and NFD: 27.0 +/- 6.5 ml/min vs 13.1 +/- 0.9 ml/min, P < 0.02). In group EXT, after 2 hr, only VPL- and PAP-treated grafts showed resistance to NE-induced vasospasm (VPL: 35.6 +/- 7.3 ml/min vs 15.0 +/- 6.9 ml/min and PAP: 47.4 +/- 15.1 ml/min vs 8.0 +/- 2.0 ml/min, P < 0.001).

CONCLUSIONS

Papaverine, a lipophilic vasodilator, when given externally on the perivascular fat of the GEA, prevented graft spasm for up to 2 hr. In contrast, intraluminally applied papaverine did not show graft protection against NE-induced spasm. Nifedipine prevented NE-induced spasm only when given intraluminally. Verapamil proved to be the most potent and versatile vasodilator with effective graft protection of up to 2 hr whether applied externally or internally and was the preferred agent for protecting against GEA spasm.