Interact CardioVasc Thorac Surg 2009;8:117-122. doi:10.1510/icvts.2008.190686
© 2009 European Association of Cardio-Thoracic Surgery
Best evidence topic - Cardiac general |
Is intrathecal morphine of benefit to patients undergoing cardiac surgery
Lydia Richardsona,
Joel Dunningb,* and
Steven Hunterb
a Medical Student, Brighton and Sussex Medical School, Brighton, East Sussex, UK
b Department of Cardiothoracic Surgery, James Cook University Hospital, Middlesbrough, UK
Received 11 August 2008;
accepted 11 August 2008
*Corresponding author. Tel./fax: +44-780-1548122.
E-mail address: joeldunning{at}doctors.org.uk (J. Dunning).
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Abstract
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A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed is whether intrathecal morphine is of benefit to patients undergoing cardiac surgery? Using the reported search 850 papers were identified. Ten papers represented the best evidence on the subject. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study comments and weaknesses were tabulated. The ten papers demonstrated that intrathecal morphine reduces postoperative pain scores, increases time to first IV morphine dose and reduces the overall postoperative IV morphine dose required, indicating its analgesic effect. Opioid-related complications remained comparable to controls, however, other benefits of reduced time to extubation, reduced ICU stay and improved postoperative lung function are variably reported with significant results found only in small retrospective studies. No spinal haematomas were reported, however, high-risk patients were excluded. We conclude that intrathecal morphine is an alternative method of pre-induction analgesia that benefits patients as less postoperative IV morphine is required, however, other benefits are less well reported.
Key Words: Intrathecal morphine; Extubation; Analgesia; ICU
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1. Introduction
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A best evidence topic was constructed according to a structured protocol, described in the ICVTS [1].
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2. Clinical scenario
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A patient has undergone 2-vessel coronary artery bypass graft surgery and returns to CICU. He is administered IV morphine for signs of pain and extubated 4 h after surgery. The patient develops nausea and later vomits for which anti-emetics are prescribed. The anaesthetist wonders whether intrathecal administration of morphine prior to induction would lead to quicker extubation, reduced requirement for IV morphine and thus reduced opioid side effects but he is cautious to proceed due to the potential complications including spinal haematoma, especially after routine systemic heparinisation, and longer anaesthetic time. You decide to perform a literature search on the benefits of intrathecal morphine in cardiac surgery.
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3. Three-part question
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In [patients undergoing cardiac surgery], is [intrathecal morphine superior to iv morphine] for [complication free analgesia]?
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4. Search strategy
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Medline 1996 to date and Embase 1996 to date using OVID interface. [exp intrathecal [morphine.mp OR exp intrathecal opioids/OR exp spinal morphine/OR exp intrathecal analgesia] AND [exp cardiothoracic surgery/OR exp cardiac surgery/OR exp thoracic surgery/OR CABG.mp]. Cochrane Database of Systematic Reviews and the Cochrane controlled trials register was searched on 4th June 2008 using the search terms ‘intrathecal morphine’ and ‘cardiac surgery’. The references of resulting papers were also reviewed.
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5. Search outcome
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Four hundred and twenty-three abstracts were identified from Medline, 427 abstracts from Embase, no papers from the Cochrane database of systematic reviews or Cochrane controlled trials register. From these studies 10 represented the best evidence on the topic (Table 1). We included one meta-analysis of RCTs [2], five randomized controlled trials [3–7] and four retrospective studies [8–11].
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6. Comments
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Liu et al. [2] included 17 RCTs in their meta-analysis, enrolling a total of 668 patients, and found that compared to patients not receiving intrathecal morphine, time to extubation, pain scores and IV morphine use postoperatively were all reduced in those receiving intrathecal morphine pre-induction. In addition, no spinal haematomas were reported despite systemic heparinisation during surgery. However, the meta-analysis fails to highlight that a range of morphine doses were used and in a selection of the RCTs intrathecal morphine is used in conjunction with other opioids.
The major beneficial postoperative effects, in agreement with Liu et al. observed amongst all five RCTs and two retrospective comparative reviews were reduced pain score [4–6], need for IV morphine [4–7, 10, 11] and increased time until first IV morphine dose [3]. However, the two patient groups in each RCT differ between studies with only Jacobsohn et al. [3] using a true control by administering intrathecal saline, while other studies administered no intrathecal morphine [4, 7], administered only IV remifentanil [5] or administered only postoperative IV morphine [6]. The intrathecal morphine doses were all comparable ranging from 6 µg/kg [3] to 10 µg/kg [5], although Roediger et al. [6] administered a bolus dose of 500 µg to all patients.
Interestingly, only one RCT [4] agreed with the finding of Liu et al. of reduced time to extubation in intrathecal morphine patients (3.58 vs. 4.86 h) while two found a longer time to extubation with intrathecal morphine [3, 5] and one observed similar times [6]. Parlow et al. [10] and Zisman et al. [11] who performed retrospective reviews did, however, observe a significantly shorter time to extubation in those patients receiving intrathecal morphine with differences of 75 vs. 117 min and 3.2 vs. 6.3 h, respectively. Metz et al. [9] performed a retrospective review of 112 patients and observed the dose of morphine most likely to reduce time to extubation to be 10–15 µg/kg, higher than that used for the RCTs. Jacobsohn et al. [3] also found that post-op spirometry after 24 h was comparable between control and treatment groups therefore showing no benefit of intrathecal morphine on post-op respiratory function.
In all RCTs and the two retrospective comparative reviews [10, 11], the ICU and hospital stays were shorter in those patients who had received intrathecal morphine compared to controls, however, not statistically significant. Only Yapici et al. [4] found a statistically significant shorter ICU stay (16.25 vs. 19.3 h), however, this study is retrospective in nature with its obvious limitations and includes only 23 patients.
Postoperative complications were comparable between groups and no spinal haematomas were reported in any of the RCTs however, in general, patients at high risk of bleeding were excluded.
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7. Clinical bottom line
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The most consistently reported benefits of intrathecal morphine are reduced pain scores, increased time to first morphine dose and overall reduced postoperative IV morphine dose. Some studies report benefits of shorter time to extubation, improved postoperative lung function and shorter ICU and hospital stays, however, only retrospective reviews report any significant differences. No spinal haematomas were reported, however, patients at high risk of bleeding were excluded. Opioid-related complications remained comparable to patients receiving only IV morphine postoperatively.
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References
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- Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: best BETS. Interact CardioVasc Thorac Surg 2003;405–409.
- Liu SS, Block BM, Wu CL. Effects of perioperative central neuraxial analgesia on outcome after coronary artery bypass surgery. Anesthesiology 2004;101:153–161.[CrossRef][Medline]
- Jacobsohn E, Lee TWR, Amadeo RJ, Syslak PH, Debrouwere RG, Bell D, Klock PA, Tymkew H, Avidan M. Low-dose intrathecal morphine does not delay early extubation after cardiac surgery. Can J Anesth 2005;52:848–857.[Medline]
- Yapici D, Altunkan ZO, Atici S, Bilgin E, Doruk N, Cinel I, Dikmengil M, Oral U. Postoperative effects of low-dose intrathecal morphine in coronary artery bypass surgery. J Card Surg 2008;23:140–145.[CrossRef][Medline]
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- Roediger L, Joris J, Senard M, Larbuisson R, Canivet JL, Lamy M. The use of pre-operative intrathecal morphine for analgesia following coronary artery bypass surgery. Anaesthesia 2006;61:838–844.[CrossRef][Medline]
- Suominen PK, Ragg PG, McKinley DF, Frawley G, Bur WW, Eyres RL. Intrathecal morphine provides effective and safe analgesia in children after cardiac surgery. Acta Anaesthesiol Scand 2004;48:875–882.[CrossRef][Medline]
- Taylor A, Healy M, McCarroll M, Moriarty DC. Intrathecal morphine: one year's experience in cardiac surgical patients. J Cardiothorac Vasc Anesth 1996;10:225–228.[CrossRef][Medline]
- Metz S, Schwann N, Hassanein W, Yuskevich B, Nixon T. Intrathecal morphine for off-pump coronoary artery bypass graftng. J Cardiothorac Vasc Anesth 2004;18:451–453.[CrossRef][Medline]
- Parlow JL, Steele RG, O'Reilly D. Low dose intrathecal morphine facilitates early extubation after cardiac surgery: results of a retrospective continuous quality improvement audit. Can J Anesth 2005;52:94–99.[Medline]
- Zisman E, Shenderey A, Amnar R, Eden A, Pizov R. The effects of intrathecal morphine on patients undergoing minimally invasive direct coronary artery bypass surgery. J Cardiothorac Vasc Anesth 2005;19:40–43.[CrossRef][Medline]
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Abstract
1. Introduction