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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 31  |  Issue : 1  |  Page : 23-27

Postoperative pain relief using intrathecal morphine for lumbar spine decompression and instrumentation surgery: A comparative study of two different doses


Department of Anaesthesiology, Dr. B. L. Kapur Memorial Hospital, New Delhi, India

Date of Web Publication5-May-2017

Correspondence Address:
Priyanka Dhir
B-6, Shankar Garden, New Delhi - 110 018
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijpn.ijpn_22_17

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  Abstract 


Background and Aims: Patients undergoing lumbar spine instrumentation surgery suffer severe postoperative pain which is difficult to treat by conventional multimodal analgesic methods. We aimed to compare the analgesic effect of two different doses of intrathecal morphine (ITM) 0.2 mg and 0.3 mg in patients undergoing lumbar spine decompression and instrumentation surgery. Design: This was a randomized, prospective, double-blinded study. Materials and Methods: After approval from the Institutional Ethics Committee, forty American Society of Anesthesiologists 1 and 2 patients of either sex aged 18 years or older undergoing lumbar spine surgery were randomly assigned to receive ITM either 0.2 mg (Group A, n = 20) or 0.3 mg (Group B, n = 20) in 2 ml saline before general anesthesia. A morphine intravenous patient-controlled analgesia (PCA) device was used for rescue analgesia in the postoperative period. Assessment parameters included hemodynamics, sedation score, pain using numeric rating scale (NRS), total consumption of PCA morphine recorded for 24 h, and patient's satisfaction score. The data were analyzed using Chi-square test for categorical variables and Student's t-test for quantitative variables. Results: NRS score was significantly low in Group B at 4, 8, 12, and 24 h as compared to Group A (P < 0.05). Group B also had decreased requirement for rescue analgesia (P = 0.001) with higher patient satisfaction. There was no significant difference between the two groups in other studied parameters. Conclusions: 0.3 mg ITM provided superior analgesia postoperatively in terms of NRS score and higher patient satisfaction compared to 0.2 mg with no significant difference in the incidence of side effects.

Keywords: Intrathecal, morphine, patient-controlled analgesia, spine surgery


How to cite this article:
Dhir P, Mittal S, Valecha UK, Khanuja JS. Postoperative pain relief using intrathecal morphine for lumbar spine decompression and instrumentation surgery: A comparative study of two different doses. Indian J Pain 2017;31:23-7

How to cite this URL:
Dhir P, Mittal S, Valecha UK, Khanuja JS. Postoperative pain relief using intrathecal morphine for lumbar spine decompression and instrumentation surgery: A comparative study of two different doses. Indian J Pain [serial online] 2017 [cited 2019 Oct 18];31:23-7. Available from: http://www.indianjpain.org/text.asp?2017/31/1/23/205715




  Introduction Top


Effective pain management is an important component of postsurgical care.[1] Intrathecal opioids (ITOs) are a novel way of postoperative analgesia as they produce “segmental analgesia” resulting in localized nociception without sensory, motor, autonomic, or systemic side effects.[2] They not only allow postoperative neurological assessment in immediate postoperative period but also avoid risk of orthostatic hypotension or motor incoordination that local anesthetics cause.[3]

Due to its long duration of action, morphine is considered a better option for intrathecal administration.

Previous studies have used 0.2–2.5 mg of intrathecal morphine (ITM) for postoperative pain control after lumbar spine surgery.[4],[5],[6],[7],[8] DeSousa and Chandran in a review article concluded that ITM higher than 0.3 mg has a risk of respiratory depression.[9] We studied low dose, i.e., 0.2 mg and 0.3 mg, of ITM for quality and duration of analgesia, side effects, and complications in posterior lumbar spinal surgeries.


  Materials and Methods Top


A prospective, randomized, double-blinded study was carried out after approval from the Ethics Committee of our hospital and written informed consent was obtained from 40 patients. American Society of Anesthesiologists (ASA) Grade I and II aged 18 years or older of either sex undergoing lumbar spine decompression and instrumentation surgery between L1 and L5 were included in the study. Patients with known allergies to morphine or other opioids, lumbar procedures performed in minimally invasive technique or revision lumbar spine surgery, patients with a history of severe respiratory illness including chronic obstructive pulmonary disease, asthma, obstructive sleep apnea, psychiatric disorders, and pregnancy, patients lacking mental capacity to use patient-controlled analgesia (PCA) or on sustained release narcotics and substance abuse, and patients not giving consent were excluded from the study.

A computer-generated random number sequence was generated using a block randomization; forty patients were allocated to either Group A (n = 20) or B (n = 20). The same was translated to sequentially numbered opaque sealed envelopes to receive ITM 0.2 mg (Group A) or 0.3 mg (Group B). The anesthesiologist conducting the case as well as recording the data was unaware of the drug being administered.

After preanesthetic checkup patients were made familiar of the numeric rating scale (NRS) for pain scoring, use of PCA system and potential adverse drug events. Patients were kept fasting for 6–8 h and premedicated with tablet ranitidine 150 mg and tablet alprazolam 0.25 mg orally, the night before surgery. On arrival in the operative room, standard monitoring equipment was attached (electrocardiogram lead II and lead V5, pulse oximeter, and noninvasive blood pressure) and baseline vital parameters such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), respiratory rate (RR), and oxygen saturation (SpO2) were noted just before induction of anesthesia. Peripheral venous access was obtained.

The index anesthesiologist prepared the aforementioned injection taking all aseptic precautions and delivered it to the operating room to ensure all parties were blinded. Patients were placed in sitting position, and the spinal puncture was performed at L3–L4 interspace using a 25-gauge whitacre pencil-point spinal needle. Once free flow of cerebrospinal fluid had been recognized, the ITM (0.2 mg or 0.3 mg) in 2 ml normal saline 0.9% was injected. No presurgery analgesia was given to the patients.

The patient was made supine. No presurgery analgesia was given to the patients. Anesthesia was induced with injection propofol 2 mg/kg, injection midazolam 1 mg, and injection morphine 0.1 mg/kg intravenous (i.v.). Endotracheal intubation was facilitated with injection vecuronium bromide 0.1 mg/kg i.v. Anesthesia was maintained with 50% N2O in O2 with sevoflurane 2%. Neuromuscular relaxation was maintained with injection vecuronium top ups of 1 mg i.v. every hourly. The lungs were mechanically ventilated to keep end-tidal CO2 within normal range. Temperature probe was inserted and temperature was recorded. The patient was catheterized and urine output was recorded. The patient was made prone for surgery. Thirty minutes before completion of surgery, all patients were given injection ondansetron 0.15 mg/kg body weight for the prevention of postoperative nausea and vomiting.

At the end of the surgery, patients were made supine, and residual neuromuscular block was reversed with injection neostigmine (0.05 mg/kg) and injection glycopyrrolate (0.008 mg/kg). Endotracheal tube was removed and patients were transferred to the postanesthesia care unit. All patients had PCA morphine in postoperative period up to 24 h. PCA was programmed to deliver a 0.5 mg morphine bolus with a 20 min lockout time through a dedicated i.v. cannula.

In the postoperative period, following parameters were recorded at 1, 2, 4, 8, 12, and 24 h after the surgery: pain score by NRS, noninvasive blood pressure, HR, RR, SpO2, nausea, vomiting, pruritus, sedation score, total morphine consumption in 24 h, and patient satisfaction score. Rescue analgesia was provided with injection morphine using PCA in incremental doses till NRS score was <3.

Pain was assessed by NRS 0–10 cm long scale, on which 0 is taken as no pain and 10 being worst possible pain. NRS <3 was taken as satisfactory pain relief. The assessor was blinded. Side effects including nausea, vomiting, respiratory depression (RR <8 breaths/min), sedation, and pruritus were also recorded. For sedation, Ramsey sedation score was used if awake: 1 - anxious, agitated, restless, 2 - cooperative, oriented, tranquil, and 3 - responsive to commands only; if asleep - 4 - brisk response to light glabellar tap or loud auditory stimulus, 5 - sluggish response to light glabellar tap or loud auditory stimulus, and 6 - no response to light glabellar tap or loud auditory stimulus. Side effects if any were treated as in table shown below.



At the end of 24 h, patients were asked to rank the quality of pain relief on a four-point pain satisfaction scale with 1 - excellent, 2 - very good, 3 - satisfactory, and 4 - poor.

The sample size calculation was based on estimating a 30% decreased in postoperative morphine requirement as observed in the previous studies.[10],[11],[12] A calculated sample size of 20 patients would be required to attain the power of at least 80% and 5% significance level with 90% confidence interval. Therefore, we enrolled 20 patients in each group. Statistical analysis was performed using Statistical analysis was performed using Statistical package for the Social Sciences (version 15, SPSS Inc., Chicago, IL, USA). Statistical significance of categorical variables between the groups was compared by Chi-square test and that of quantitative variables was compared using Student's t-test and nonparametric Mann–Whitney U-test in case data do not follow normal distribution. Quantitative variables are presented as mean (±standard deviation), while ordinal data are presented as number (%). P< 0.05 was considered statistically significant.


  Results Top


The demographic profile in relation to age, weight, gender, ASA grade, and duration of surgery in the two groups was comparable [Table 1]. The extent of the surgical procedure was similar in both the groups involving two or three levels of lumbar vertebrae.
Table 1: Demographic variable and operative data

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The NRS score at 1 and 2 h postoperative was comparable in both the groups (P = 0.714 and 0.721, respectively). In Group B, there was a statistically significant decrease in the NRS score at 4, 8, 12, and 24 h postoperative. On the other hand in Group A, NRS score was slightly more than the value at 2 h. When comparing the two groups, in Group B, none of the patients had pain score >2. The difference in NRS score was statistically significant at 4, 8, 12, and 24 h postoperative between the two groups (P < 0.05) [Figure 1].
Figure 1: Comparison of numeric rating scale Group A: 0.2 mg intrathecal morphine, Group B: 0.3 mg intrathecal morphine

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The morphine consumption as rescue analgesia over 24 h was much higher in Group A as compared to Group B. The difference was found to be statistically significant (P = 0.001) [Table 2]. The patient satisfaction in Group B was much higher than in Group A (P = 0.001) [Figure 2]. However, the exact time of first use of rescue analgesia could not be recorded as it was administered by the patient himself/herself. The mean sedation score at 1, 2, and 12 h postoperative was comparable in both the groups (P = 0.061, 0.370, and 0.119, respectively). The difference between the two groups was statistically significant at 4, 8, and 24 h (P < 0.05). However, it was not clinically significant as none of the patients had score >4 at any occasion.
Table 2: Mean 24 h morphine requirement

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Figure 2: Comparison of patient satisfaction score Group A: 0.2 mg intrathecal morphine, Group B: 0.3 mg intrathecal morphine

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Hemodynamic parameters (HR, SBP, DBP, RR, and SpO2) were within the normal limit during the entire 24 h postoperative period [Table 3]. There was no occasion when the RR was <10/min or SpO2 <93% in either group. The number of patients complaining of vomiting and pruritus in the postoperative period was comparable between the two groups [Table 4].
Table 3: Hemodynamic parameters

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Table 4: Side effects

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  Discussion Top


Pain is one of the main postoperative adverse outcomes, which determines postsurgical morbidity, ambulation, and discharge from hospital. Most patients complain of severe pain at rest during the first 12 h after lumbar spine decompression and instrumentation surgery. This pain increases considerably with mobilization because of the reflex spasm of paraspinal muscles that is triggered by the primary wound pain. On movement, pain remains severe for 48 h and produces discomfort that can interfere with patient mobilization and with discharge time.[1],[13]

Analgesics given before the onset of pain, or “preventive analgesia,” prevent plasticity of the central nervous system and provide more effective pain relief.[14] It has been seen that low doses of morphine used for preventive analgesia prevent central sensitization and prevent chronic pain.[15]

In a meta-analysis of ITM, the seriousness of the induced respiratory depression was related to the dose of ITM.[15] The incidence of late respiratory depression is reported to be 4%–7% for patients receiving ITM (0.8–2 mg). Lower doses of ITM (0.3–0.4 mg) are linked to minimal risks of respiratory depression.[15]

Recently, practice guidelines for the administration of neuraxial opioids have been published by the ASA Task Force.[16] According to the guidelines, the lowest efficacious dose of neuraxial opioid should be used to minimize the risk of respiratory depression. The present study has used the same approach of low dose to prevent respiratory depression.

Single-shot intrathecal technique using ITO with long-lasting analgesia offers many advantages compared with epidural catheter or i.v. PCA. Technically, the intrathecal injection is easier to perform than epidural catheter placement and does not need additional equipment as required in epidural catheter or i.v. PCA. The single-shot approach precludes the risk of catheter dislodgement or catheter-related infection.[17]

Meylan et al. had done a meta-analysis of 27 studies (15 concerning cardiothoracic, 9 abdominal, and 3 spinal surgeries) with a total of 645 patients who received doses between 100 and 4000 μg of ITM without local anesthetic in patients undergoing major surgeries. They had seen that pain intensity was significantly decreased at 2, 4, 12, and 24 h.[18] Up to 4 h after surgery, pain intensity at rest was decreased by about 2 cm on the 10-cm visual analog scale (VAS). At 12 and 24 h, pain intensity was decreased by about 1 cm. This degree of analgesic efficacy appears to be greater than with intraoperative low-dose ketamine (reduction in pain intensity at 24 h, about 0.4 cm) and postoperative nonsteroidal anti-inflammatory drugs or epidural analgesia with local anesthetic (with both, reduction in pain intensity at 24 h, about 1 cm). These findings were similar to the present study in which pain intensity was significantly low in 0.3 mg ITM at 4, 8, 12, and 24 h.

In this review, study authors did not detect a linear relationship between the dose administered and degree of analgesia reached. They concluded that they do not know the optimal dose of ITM when used alone. In contrast to this review, in the present study, a superior analgesic effect was recorded with 0.3 mg ITM as compared to 0.2 mg at all recorded times.

Machino et al. and Trivedi et al. had observed that the patients who received ITM had significantly lower VAS score.[19],[20] They had used lower dose of ITM in combination with local anesthetics. In contrast, the present study had used low dose ITM alone but had found the same results.

Rebel et al. had combined high-dose ITM with i.v. naloxone.[17] They had seen that the i.v. naloxone infusion combined with high-dose ITM control opioid side effects without affecting analgesia.

Fares et al. compared 0.2, 0.5, and 1 mg ITM.[21] They had seen that 1 mg morphine provided superior analgesia for 48 h postoperative. Both these studies had used higher doses of ITM in contrast to the present study where we had used lower doses.

Ross et al. concluded from their study that consumption of parenteral narcotics decreases in correlation with increasing doses of intrathecally administered morphine without increase in parenteral narcotic side effects because of less consumption postoperatively.[7] This was similar to our study. In our study, as we increased the dose of ITM from 0.2 to 0.3 mg, there was a decrease in morphine consumption over 24 h with higher patient satisfaction. The difference was found to be statistically significant (P = 0.001).

Hemodynamic parameters (HR, SBP, DBP, RR, and SpO2) were within the normal limit during the entire 24 h postoperative period. There was no occasion when the RR was <10/min or SpO2 was <93% in either group.

The incidence of nausea, vomiting, and pruritus was comparable in both the groups. The sedation score was higher in Group B as compared to Group A. However, we have not seen a clinically significant sedation score of 6 in any of the patients.

This study has certain limitations such as interpatient pain threshold variability. Not only was this no exact record of preoperative analgesia kept. However, no patient was on any long-acting analgesic preparation. Since patients had been provided with i.v.-PCA, it was difficult to standardize the time-to- first analgesic dose administration as patients often ended up demanding the dose of analgesic based on her own ability to tolerate pain. Hence, the duration of postoperative analgesia cannot be reliably predicted for the two groups. As small sample size was taken, further larger study would be required to confirm the results.


  Conclusions Top


ITM is a simple, safe, reliable technique that provides very good postoperative analgesia in patients after lumbar spine surgery. Side effects such as sedation and respiratory depression could be minimized using appropriate dose of ITM, and minor side effects such as nausea, vomiting, and pruritus could be managed by injection ondansetron. The present study found that single shot of 0.3 mg ITM provided superior analgesia with higher patient satisfaction without increase in the side effects as compared to 0.2 mg morphine. A larger study would be required to confirm the suggestion of 0.3 mg ITM as highly efficient analgesic with minimal side effects after lumbar spine decompression and instrumentation surgery.

Acknowledgment

I would like to acknowledge the effects and encouragement of my guide, my colleagues, Department of Anaesthesiology, Dr. B. L. Kapur Memorial Hospital, New Delhi, and my family.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
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Ross DA, Drasner K, Weinstein PR, Flaherty JF, Barbaro NM. Use of intrathecally administered morphine in the treatment of postoperative pain after lumbar spinal surgery: A prospective, double-blind, placebo-controlled study. Neurosurgery 1991;28:700-4.  Back to cited text no. 7
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