Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Cardiovascular Anesthesia
Introduction: Administration of methylprednisolone (METHYL) to patients prior to cardiopulmonary bypass (CPB) may [1,2] or may not [3,4] attenuate detrimental physiologic alterations in the lungs. Although the majority of clinical studies suggest METHYL may be beneficial in facilitating early extubation following cardiac surgery, no investigation has examined use of the drug in this setting. This study examined the effects of METHYL on the alveolar-arterial (A-a) oxygen gradient, intrapulmonary shunt, and extubation time in patients undergoing coronary artery bypass grafting (CABG) and early extubation.
Methods: After IRB approval and informed consent, 60 patients scheduled for elective CABG were studied. Prior to anesthesia induction, patients were randomized to receive either intravenous METHYL (30 mg/kg at sternotomy and 30 mg/kg at initiation of CPB) or intravenous PLACEBO (normal saline) at the same two times. All patients received a standardized anesthetic technique consisting of fentanyl (20 mcg/kg), midazolam (10 mg, total), and vecuronium. A pulmonary artery catheter was utilized in all patients to facilitate data collection. A-a gradient and shunt were calculated via standard equations 10 minutes after intubation and 60 minutes after intensive care unit (ICU) arrival utilizing blood gases obtained from the radial artery and pulmonary artery catheter. Mechanical ventilation was standardized at each data point (RR 8, TV 10 ml/kg, FIO2 1.0, PEEP + 5). Postoperative extubation was accomplished at the earliest clinically appropriate time.
Results: 30 patients were randomized to each group. Mean crossclamp time (79 +/- 21 min, 84 +/- 22 min) and mean CPB time (98 +/- 28 min, 102 +/- 24 min) were similar in the PLACEBO and METHYL groups, respectively. Mean A-a gradients (mm Hg) and shunts (%) are listed below. (Table 1)
Both groups exhibited significant increases in A-a gradient (p<0.000001 for each group) and shunt (p<0.000001 for each group) from time A to time B. Although the two groups were similar at time A, the METHYL group exhibited a significantly larger A-a gradient (p<0.02) and shunt (p<0.01) at time B when compared to the PLACEBO group. Two patients in the PLACEBO group were not extubated within 24 hours of ICU arrival whereas all patients in the METHYL group were extubated within this time frame. Of the 58 patients extubated within 24 hours of ICU arrival, mean time to extubation was significantly prolonged in the METHYL group when compared to the PLACEBO group (769 +/- 294 min vs 604 +/- 315 min, respectively, p<0.05).
Discussion: The majority of clinical studies suggest METHYL may be beneficial in facilitating early extubation following cardiac surgery yet no investigation has examined use of the drug in this setting. We found METHYL significantly increased pulmonary dysfunction following cardiac surgery as assessed by A-a gradient, shunt, and extubation time, indicating that use of the drug in this setting may be contraindicated.
1. Scand J Thor Card Surg 1987; 21:255-261
2. J Thor Card Surg 1986; 91:252-258
3. Thorax 1979; 34:720-725
4. Am J Surg 1975; 130:555-559