This Article Abstract Résumé de cet Article Full Text (PDF) Submit a scholarly reply Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dal, D. Articles by Aypar, U. Search for Related Content PubMed PubMed Citation Articles by Dal, D. Articles by Aypar, U.

A background infusion of morphine does not enhance postoperative analgesia after cardiac surgery

[Une perfusion de morphine de base n’améliore pas l’analgésie postopératoire en cardiochirurgie]

Didem Dal, MD^*, Meral Kanbak, MD^*, Meltem Caglar, MD and Ulku Aypar, MD^*

^* From the Departments of Anesthesiology and Reanimation, and
Nuclear Medicine, Hacettepe University, Ankara, Turkey.

Address correspondence to: Dr. Didem Dal, Hacettepe University, Faculty of Medicine, Department of Anesthesiology and Reanimation, 06100 Ankara, Turkey. Phone: 90 312 3051250; Fax: 90 312 3109600; E-mail: didemdal{at}yahoo.com

	Abstract

TOP Abstract Introduction Methods Results Discussion References

 
Purpose: To compare the effects of patient-controlled analgesia (PCA), with or without a background infusion of morphine on postoperative pain relief and stress response after cardiac anesthesia.

Methods: With University Ethics approval, 35 consenting adults undergoing elective open-heart surgery were randomly assigned preoperatively in a double-blind fashion to receive either morphine PCA alone (Group I, n = 15) or morphine PCA plus a continuous basal infusion (Group II, n = 14) for 44 hr postoperatively. Pain scores with visual analogue scale (VAS) at rest, deep inspiration and with cough, sedation scores, stress hormone levels [cortisol, adrenocorticotropin (ACTH) and growth hormone (GH)] and morphine consumption were assessed, and serum morphine levels were measured at four, 20, 28 and 44 hr after surgery. Adverse effects including nausea, vomiting, constipation, urinary retention and pruritus were noted. Total blood, fluid requirements, drainage and urinary output were recorded.

Results: Postoperative morphine consumption at 44 hr was less in Group I (29.43 ± 12.57 mg) than in Group II (50.14 ± 16.44 mg), P = 0.0006. There was no significant difference between groups in VAS scores, GH levels, blood levels of morphine and adverse effects. While VAS scores, ACTH and GH levels decreased significantly in both groups, plasma cortisol levels increased significantly in Group I only at four hours. In Group II, ACTH and cortisol were higher at four and 44 hr respectively.

Conclusion: PCA with morphine effectively controlled postoperative pain after cardiac surgery. The addition of a background infusion of morphine did not enhance analgesia and increased morphine consumption.

	Introduction

TOP Abstract Introduction Methods Results Discussion References

 
PAIN that also augments the neurohumoral response is an important problem for patients who undergo cardiothoracic surgery.¹ Therefore methods for effective pain control are required.

Patient-controlled analgesia (PCA) was used either alone or in addition to continuous basal infusion in different clinical trials.^2–6 In a series of postoperative studies, PCA plus continuous infusion resulted in better analgesia than PCA alone. However other studies demonstrate no benefit in adding a continuous infusion to PCA therapy and claim increased drug utilization without an increase in analgesia.^7–9

In this double-blinded prospective clinical study, the effects of a continuous infusion of morphine in addition to PCA on postoperative pain and stress hormones in patients undergoing open heart surgery were evaluated.

	Methods

TOP Abstract Introduction Methods Results Discussion References

 
After Ethics Committee approval, a prospective double-blind study was conducted. ASA II–III patients younger than 70 yr of age undergoing an elective open-heart surgery were included.

Patients with a left ventricular ejection fraction less than 45% and with abnormal hepatic or renal functions and diabetes were excluded. Patients that necessitated a reoperation or intraaortic balloon pump, and patients with agitation or neurological complications that impaired the proper use of the PCA pump were excluded from the study.

Patients provided informed consent and were randomly allocated into the PCA alone (Group I) or PCA plus continuous basal infusion (Group II) groups. They were informed on the role and function of PCA and use of the pump.

A standard anesthetic technique was used. Diazepam 10 mg po was administered as premedication. Anesthesia was induced with diazepam 5–10 mg, fentanyl 5 µg•kg^-1, etomidate 0.3 mg•kg^-1 and vecuronium bromide 0.08 mg•kg^-1 and was maintained with isoflurane 0.5–1%, N₂O in oxygen. Additional fentanyl was given as required for the operative period. Cardiopulmonary bypass was standardized. Patients were extubated in the operating room and transferred to the intensive care unit for the first 24 hr and treated in an intermediate care unit after the first 24 hr.

Postoperative analgesia was provided by iv PCA with morphine and was started on the second postoperative hour. No additional analgesic drugs were given in the first two hours after extubation. PCA included a loading dose of 3 mg, and a bolus dose of 1 mg, with a 15-min lockout period in both groups. The continuous infusion was set at 0.5 mg•hr^-1 in Group II. Pain was evaluated with a visual analogue scale (VAS) at rest, deep inspiration and with coughing. Blood samples were obtained for measurements of adrenocorticotropin (ACTH), growth hormone (GH), cortisol, and morphine levels two hours before PCA (baseline) and four, 20, 28 and 44 hr after the operation. Postoperative pain was evaluated in these two groups by a standard 10-cm VAS with one end representing "no pain" (0 cm) and the other "most severe pain" (10 cm). An anesthesiologist blinded to group assignment recorded pain and sedation scores. The sedation score was assessed using a four-point scale as follows: 0 = awake; 1 = easy awakening; 2 = awaken by physical stimulation; 3 = difficult to awake by physical stimulation.² VAS and sedation scores, and morphine consumption were assessed at the same time intervals. Serum morphine concentrations were measured by chemiluminescence. Adverse effects including nausea, vomiting, constipation, urinary retention and pruritus were also noted. Total blood and fluid requirement, drainage and urinary output were recorded. Heart rate, arterial pressure, oxygen saturation, central venous pressure and ventilatory frequency were monitored continuously.

The primary measures (dependent variable) of treatment efficacy were VAS scores and stress response. Measurements at five time points were analyzed in a repeated measures analysis of Wilcoxon matched pairs test. T test was used for demographic data. Intragroup comparisons were performed by Mann-Whitney U test and P values less than 0.05 were considered to be statistically significant.

	Results

TOP Abstract Introduction Methods Results Discussion References

 
Thirty-five patients were enrolled in the study and six patients, three in each group, were excluded because of reoperation, late extubation or missing data. The two groups were similar for demographic data, surgical procedures and anesthesia regimen (Table I).

View larger version (47K): [in this window] [in a new window]   FIGURE 1 Pain scores as measured by visual analogue scale at rest and at inspiration at predetermined times after surgery. Mean ± SD. #P < 0.05 vs baseline. Group I = patient-controlled analgesia (PCA) alone; Group II = PCA plus continuous basal infusion.

GH, ACTH and cortisol levels were similar in both groups during the study period (Figure II). The decrease in ACTH level was more pronounced at the fourth hour in Group I and cortisol levels of groups were significantly different at the 44^th hr (P < 0.05; Figure 2).

View larger version (34K): [in this window] [in a new window]   FIGURE 2 Adrenocorticotropin (ACTH), cortisol and growth hormone (GH) concentrations (mean ± SD). Group I = patient-controlled analgesia (PCA) alone; Group II = PCA plus continuous basal infusion. *P < 0.05 Group I vs II; #P < 0.05 vs baseline.

	Discussion

TOP Abstract Introduction Methods Results Discussion References

 
Despite impaired cardiopulmonary and hepatic functions, patients undergoing open-heart surgery are required to awaken rapidly after surgery. These conditions render pain control and sedation more difficult. Checketts et al. suggested that PCA techniques could be used successfully by adult cardiac surgical patients.¹⁰ Our study is in agreement and shows that PCA alone or with an additional basal infusion of morphine at the suggested minimal dosage¹ effectively controls pain after cardiac operations.

While cortisol concentrations did not differ, ACTH and GH concentrations decreased in both groups. However, decreases were similar in both groups, irrespective of pain management.

The addition of a continuous basal infusion of morphine to morphine PCA does not result in superior pain control or an improved neurohumoral response, but increases morphine consumption. PCA alone should be preferred for pain control in patients who have undergone open-heart surgery.

Revision received February 12, 2003. Accepted for publication November 21, 2002.

	References

TOP Abstract Introduction Methods Results Discussion References

 
1 Wolman RL. Patient-controlled analgesia following thoracic surgery. In: Gravlee and Rauck (Eds). Pain Management in Cardiothoracic Surgery. Philadelphia: Lippincott Company; 1993: 59–87.

2 Boldt J, Thaler E, Lehmann A, Papsdorf M, Isgro F. Pain management in cardiac surgery patients: comparison between standard therapy and patient-controlled analgesia regimen. J Cardiothorac Vasc Anesth 1998; 12: 654–8.[Medline]

3 Searle NR, Roy M, Bergeron G, et al. Hydromorphone patient-controlled analgesia (PCA) after coronary artery bypass surgery. Can J Anaesth 1994; 41: 198–205.[Abstract/Free Full Text]

4 Myles PS, Buckland MR, Cannon GB, et al. Comparison of patient-controlled analgesia and nurse-controlled infusion analgesia after cardiac surgery. Anaesth Intensive Care 1994; 22: 672–8.[Medline]

5 Rapanos T, Murphy P, Szalai JP, Burlacoff L, Lam-McCulloch J, Kay J. Rectal indomethacin reduces postoperative pain and morphine use after cardiac surgery. Can J Anesth 1999; 46: 725–30.[Abstract/Free Full Text]

6 Munro AJ, Long GT, Sleigh JW. Nurse-administered subcutaneous morphine is a satisfactory alternative to intravenous patient-controlled analgesia morphine after cardiac surgery. Anesth Analg 1998; 87: 11–5.[Abstract/Free Full Text]

7 Burns JW, Hodsman NB, McLintock TT, Kenny GN, McArdle CS. The influence of patient characteristics on the requirements for postoperative analgesia. A reassessment using patient-controlled analgesia. Anaesthesia 1989; 44: 2–6.[Medline]

8 Sinatra R, Chung KS, Silverman DG, et al. An evaluation of morphine and oxymorphone administered via patient-controlled analgesia (PCA) or PCA plus basal infusion in post cesarean-delivery patients. Anesthesiology 1989; 71: 502–7.[Medline]

9 Parker RK, Holtmann B, White PF. Patient-controlled analgesia. Does a concurrent opioid infusion improve pain management after surgery? JAMA 1991; 266: 1947–52.[Abstract]

10 Checketts MR, Gilhooly CJ, Kenny GN. Patient-maintained analgesia with target-controlled alfentanil infusion after cardiac surgery: a comparison with morphine PCA. Br J Anaesth 1998; 80: 748–51.[Abstract/Free Full Text]

This article has been cited by other articles:

				D. Bainbridge, J. E. Martin, and D. C. Cheng Patient-controlled versus nurse-controlled analgesia after cardiac surgery - a meta-analysis: [L'analgesie auto-controlee versus controlee par le personnel infirmier apres la chirurgie cardiaque - une meta-analyse]. Can J Anesth, May 1, 2006; 53(5): 492 - 499. [Abstract] [Full Text] [PDF]

				J. A. Grass Patient-Controlled Analgesia Anesth. Analg., November 1, 2005; 101(5S_Suppl): S44 - 61. [Abstract] [Full Text] [PDF]

				T. Guler, H. Unlugenc, Z. Gundogan, M. Ozalevli, O. Balcioglu, and M. S. Topcuoglu A background infusion of morphine enhances patient-controlled analgesia after cardiac surgery: [Une perfusion de morphine ameliore l'analgesie autocontrolee apres cardiochirurgie] Can J Anesth, August 1, 2004; 51(7): 718 - 722. [Abstract] [Full Text] [PDF]

This Article Abstract Résumé de cet Article Full Text (PDF) Submit a scholarly reply Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dal, D. Articles by Aypar, U. Search for Related Content PubMed PubMed Citation Articles by Dal, D. Articles by Aypar, U.