Intrathecal morphine provides effective and safe analgesia in children after cardiac surgery

Effects of 5 µg/kg intrathecal morphine for postoperative analgesia in pediatric patients undergoing major surgery

BACKGROUND

The effects and analgesic adequacy of intrathecal morphine (ITM) administration have been studied less frequently than other regional analgesia techniques in pediatric surgical procedures.

OBJECTIVE

To evaluate the efficacy and adverse event rate of 5 µg/kg ITM administration for postoperative analgesia according to age group.

METHODS

We retrospectively evaluated the medical records of patients who underwent major pediatric surgery and were administered ITM for postoperative analgesia. Patients were divided into three age groups: ≤ 5 years (group I), 5.1-13 years (group II) and > 13 years (group III). All patients received ITM 5 µg/kg (max 300 μg) through the L_4-5 or L₅-S₁ interspace. Postoperative pain (modified pediatric objective pain score > 4), need for rescue analgesics, sleep interruption due to pain, sedation (Ramsay sedation scale score > 3), opioid-related postoperative adverse events (at 0, 4, 8, 12, and 24 h after intervention), hemodynamic data and nurse satisfaction with the analgesic method were compared between groups.

RESULTS

The analysis included 100 children (47 girls, 9 ± 5.4 years). Groups were similar regarding postoperative rescue analgesia consumption and sleep interruption (p = 0.238, p = 0.958), 96% of the children did not require rescue analgesia, and sleep interruption was not observed in 97%. Postoperative adverse events were pruritus in 14 and nausea/vomiting in 9 patients (p = 0.052). Overall, nurses were satisfied or very satisfied in 99% of the cases.

CONCLUSION

Administration of 5 µg/kg ITM can be used for postoperative analgesia in pediatric surgery in all age groups, with no severe adverse events and high nurse satisfaction with analgesic management.

Regional anesthesia for sternotomy and bypass-Beyond the epidural

Systemic opioids have been the main stay for the management of perioperative pain in children undergoing cardiac surgery with sternotomy. The location, distribution, and duration of pain in these children have not been studied as extensively as in adults. Currently, there is no consensus to the dose of opioids required to provide optimum analgesia and attenuate the stress response while minimizing their unwanted side effects. At present there is a tendency to use lower dose aiming for early extubation and minimize opioid-related side effects, but this may not obtund the stress response in all children. The development of chronic pain although rare when compared to adults is still a risk that needs further investigation. Regional anesthetic techniques, by blocking the afferent impulses, have been shown to be advantageous in reducing the stress response to surgery as well as pain and opioid requirements in children up to 24 hours after cardiac surgery. Central neuraxial blockades have not gained wide spread acceptance in these procedures due to the worry of hematoma, although rare, leading to catastrophic neurological outcomes. This review focuses on blocks outside the vertebral column, ie, peripheral nerve blocks, performed either in the front or the back of the chest wall to target the thoracic intercostal nerves. Techniques of ultrasound-guided bilateral single shot paravertebral block and erector spinae block posteriorly and transversus thoracic plane block anteriorly are discussed. In addition, parasternal block and wound infiltration by surgeon as well as continuous local anesthetic infusion via catheters placed at end of procedures are summarized. Current evidence available for use of these techniques in children undergoing cardiac surgery are reviewed. These are based on small studies and case series and further studies are required to evaluate the risks and benefits of local anesthetic blocks in children undergoing cardiac surgery.

Pediatric Cardiac Surgery and Pain Management: After 40 Years in the Desert, Have We Reached the Promised Land?

Pain prevention in the pediatric population is mandatory and an integrative aspect of medical practice. Optimal pain management is the right of all patients and the responsibility of all health professionals. The key to adequate pain management is assessing its presence and severity, identifying those who require intervention, and appreciating treatment efficacy. The population of pediatric patients undergoing cardiac surgery is unique in both clinical severity and hemodynamic response to painful stimuli, thus making pain management even more challenging. In this review, we will describe the different pain assessment tools as well as intra- and postoperative regimens of pain management.

Pain outcomes in children who received intrathecal vs intravenous opioids for pain control following major urologic surgery: a retrospective review

BACKGROUND

Intrathecal (IT) opioid administration has been associated with postoperative benefits including reduced pain and opioid use in children. However, the postoperative benefits and risks of IT opioid administration during major urologic surgery in children remain unclear.

AIM

The aim of this study was to compare postoperative pain and adverse event outcomes among children who received IT vs intravenous (IV) opioids during major urologic surgery.

METHODS

We reviewed the medical records of children 3-17 years of age who underwent ureteroneocystostomy or pyeloplasty between 2006 and 2012. Electronically captured anesthetic and surgical data, postanesthesia care recovery unit (PACU) and nursing flowsheets, and daily progress notes through hospital discharge were reviewed. Analgesic techniques (i.e., IT or IV patient/nurse controlled opioids), all analgesic drugs and doses were recorded. Outcome measures included pain scores, need for rescue analgesics, opioid-related adverse events, and their treatments.

RESULTS

Seventy-seven children received IT opioids and 51 received IV opioids. More children in the IV group required rescue analgesics and had higher pain scores at PACU discharge. Children in the IV group required rescue opioids more frequently than the IT group from 0 to 8 h and 8 to 16 h after PACU discharge, but rates were similar by 16-24 h 70% of children in IT group transitioned directly to oral opioids. Seven IT placements were considered as failed due to early need for rescue opioids. Four (8%) of the IV group and seven (9%) of the IT group experienced oxygen desaturation. Two of these, both in IT group required naloxone and one was admitted to ICU for observation. The IT group experienced a higher incidence of pruritus, constipation and hypotension.

CONCLUSION

We observed better postoperative pain control in children who received IT vs IV opioids for the first 16 h with no discernible difference thereafter. The intrathecal group experienced higher incidences of pruritus, constipation, and hypotension.

Immediate rescue designs in pediatric analgesic trials: a systematic review and meta-analysis

BACKGROUND

Designing analgesic clinical trials in pediatrics requires a balance between scientific, ethical, and practical concerns. A previous consensus group recommended immediate rescue designs using opioid sparing as a surrogate measure of analgesic efficacy. The authors summarize the performance of rescue analgesic designs in pediatric trials of four commonly used classes of analgesics: opioids, nonsteroidal antiinflammatory drugs, acetaminophen, and local anesthetics.

METHODS

MEDLINE, Embase, CINAHL, The Cochrane Library, and Web of science were searched in April 2013. The 85 studies selected were randomized or controlled clinical trials using immediate rescue paradigms in postoperative pain settings. A random-effects meta-analysis was used to synthesize predefined outcomes using Hedges' g. Difference between the means of the treatment arms were also expressed as a percentage of the corresponding value in the placebo group (placebo-treatment/placebo). Distributions of pain scores in study and control groups and relationships between opioid sparing and pain scores were examined.

RESULTS

For each of the four study drug classes, significant opioid sparing was demonstrated in a majority of studies by one or more of the following endpoints: (1) total dose (milligram per kilogram per hour), (2) percentage of children requiring rescue medication, and (3) time to first rescue medication (minutes). Pain scores averaged 2.4/10 in study groups, 3.4/10 in control groups.

CONCLUSIONS

Opioid sparing is a feasible pragmatic endpoint for pediatric pain analgesic trials. This review serves to guide future research in pediatric analgesia trials, which could test whether some specific design features may improve assay sensitivity while minimizing the risk of unrelieved pain.

Intrathecal morphine for postoperative analgesia: Current trends

The practice of anesthesiology has always been governed by evidence-based medicine. The quick turnover rate of patients in the operating room and patient safety and satisfaction, have also further changed the way we practice anesthesia. The use of intrathecal (IT) opiates as an effective form of postoperative pain relief has been established for many years. Morphine was the first opioid used by IT route. In clinical practice, morphine is regarded as the gold standard, or benchmark, of analgesics used to relieve intense pain. Perhaps for this reason, IT morphine has been used for over 100 years for pain relief. IT morphine is one of the easiest, cost-effective and reliable techniques for postoperative analgesia and technical failures are rare. And yet there is no consensus amongst anesthesiologists regarding the dose of IT morphine. Like all other methods of pain relief, IT morphine also has some side effects and some of them are serious though not very common. This review article looks into some of the key aspects of the use of IT morphine for post-operative analgesia and various doses for different procedures are discussed. This article also describes the side effects of IT morphine and how to treat and prevent them.

Neuraxial analgesia in neonates and infants: a review of clinical and preclinical strategies for the development of safety and efficacy data

Neuraxial drugs provide robust pain control, have the potential to improve outcomes, and are an important component of the perioperative care of children. Opioids or clonidine improves analgesia when added to perioperative epidural infusions; analgesia is significantly prolonged by the addition of clonidine, ketamine, neostigmine, or tramadol to single-shot caudal injections of local anesthetic; and neonatal intrathecal anesthesia/analgesia is increasing in some centers. However, it is difficult to determine the relative risk-benefit of different techniques and drugs without detailed and sensitive data related to analgesia requirements, side effects, and follow-up. Current data related to benefits and complications in neonates and infants are summarized, but variability in current neuraxial drug use reflects the relative lack of high-quality evidence. Recent preclinical reports of adverse effects of general anesthetics on the developing brain have increased awareness of the potential benefit of neuraxial anesthesia/analgesia to avoid or reduce general anesthetic dose requirements. However, the developing spinal cord is also vulnerable to drug-related toxicity, and although there are well-established preclinical models and criteria for assessing spinal cord toxicity in adult animals, until recently there had been no systematic evaluation during early life. Therefore, in the second half of this review, we present preclinical data evaluating age-dependent changes in the pharmacodynamic response to different spinal analgesics, and recent studies evaluating spinal toxicity in specific developmental models. Finally, we advocate use of neuraxial drugs with the widest demonstrable safety margin and suggest minimum standards for preclinical evaluation before adoption of new analgesics or preparations into routine clinical practice.

Pharmacotherapy for acute pain in children: current practice and recent advances

INTRODUCTION

Acute pain in children may be undertreated. Improved understanding of developmental neurobiology and paediatric pharmacokinetics should facilitate better management of pharmacotherapy. The objective of this review is to discuss current paediatric practice and recent advances with these analgesic agents by using an evidence-based approach.

AREAS COVERED

Using PubMed an extensive literature review was conducted on the commonly used analgesic agents in children from 2000 to April 2010.

EXPERT OPINION

A multimodal analgesic regimen provides better pain control and functional outcome in children. The choice of pharmacological treatment is determined by the severity and type of pain. However, more research and evidence is required to determine the optimal drug combinations.

[Intrathecal opioid medication for perioperative analgesia in severely handicapped children undergoing spinal operations]

PURPOSE OF THE STUDY

Intrathecal opioids have been shown to be safe and effective for postoperative analgesia in healthy children for spinal surgery. The aim of this study was to evaluate the applicability of intrathecal opioids in severely handicapped children scheduled for spinal surgery.

METHODS

With hospital ethical committee approval, patients with physical states III and IV of the ASA classification requiring spinal surgery were retrospectively studied. In addition to inhalational anesthesia with sevoflurane or intravenous anesthesia using propofol, morphine 20 microg/kgBW and sufentanil 1.5 microg/kgBW were administered intrathecally before surgery. After surgery an infusion of nalbuphine was started. Need for additional intraoperative and postoperative analgesics, time of extubation, postoperative pain scores and p(a)CO2 values as well as adverse effects were recorded.

RESULTS

A total of 28 patients aged from 2.8 to 18.5 years (median 11.6 years) were studied. Immediate tracheal extubation in the operating room was possible in 17 patients and for 11 patients delayed extubation was elected. All patients were extubated within 24 h except for 1 patient who received massive postoperative transfusions. In 26 out of 28 patients (93%) the combination of intrathecal opioids with postoperative nalbuphine provided adequate analgesia. Observed side effects were post-operative nausea and vomiting (PONV), pruritus and moderate hypoventilation. In two patients a change to intravenous morphine therapy was necessary.

CONCLUSION

The use of intrathecal opioids for perioperative pain control from spinal fusion in severely handicapped children is feasible. Intrathecal opioids provide adequate postoperative analgesia and allow early extubation without persisting relevant respiratory compromise in most of these patients.

Validation of a preclinical spinal safety model: effects of intrathecal morphine in the neonatal rat

BACKGROUND

Preclinical studies demonstrate increased neuroapoptosis after general anesthesia in early life. Neuraxial techniques may minimize potential risks, but there has been no systematic evaluation of spinal analgesic safety in developmental models. We aimed to validate a preclinical model for evaluating dose-dependent efficacy, spinal cord toxicity, and long-term function after intrathecal morphine in the neonatal rat.

METHODS

Lumbar intrathecal injections were performed in anesthetized rats aged postnatal day (P) 3, 10, and 21. The relationship between injectate volume and segmental spread was assessed postmortem and by in vivo imaging. To determine the antinociceptive dose, mechanical withdrawal thresholds were measured at baseline and 30 min after intrathecal morphine. To evaluate toxicity, doses up to the maximum tolerated were administered, and spinal cord histopathology, apoptosis, and glial response were evaluated 1 and 7 days after P3 or P21 injection. Sensory thresholds and gait analysis were evaluated at P35.

RESULTS

Intrathecal injection can be reliably performed at all postnatal ages and injectate volume influences segmental spread. Intrathecal morphine produced spinally mediated analgesia at all ages with lower dose requirements in younger pups. High-dose intrathecal morphine did not produce signs of spinal cord toxicity or alter long-term function.

CONCLUSIONS

The therapeutic ratio for intrathecal morphine (toxic dose/antinociceptive dose) was at least 300 at P3 and at least 20 at P21 (latter doses limited by side effects). These data provide relative efficacy and safety for comparison with other analgesic preparations and contribute supporting evidence for the validity of this preclinical neonatal safety model.

Efficacy of a low-dose spinal morphine with bupivacaine for postoperative analgesia in children undergoing hypospadias repair

BACKGROUND

Children undergoing hypospadias repair need to be protected from highly unpleasant sensory and emotional experiences during and after surgery. We designed a double-blinded, randomized, and placebo-controlled study to compare the efficacy of a low-dose (2 microg x kg(-1)) of intrathecal morphine with placebo for postoperative pain control of children undergoing repair of hypospadias surgery with spinal anesthesia.

METHODS

Fifty-four children were randomly assigned to one of two spinal anesthesia groups. Group M (n = 27) received hyperbaric bupivacaine plus 2 microg x kg(-1) of preservative-free morphine and group P (n = 27) received hyperbaric bupivacaine plus 0.9% NaCl (placebo) under inhalation anesthesia. General anesthetics were discontinued subsequent to the block. The primary outcome was the presence of pain-requiring analgesics during the first 12 h after the spinal block. Side effects were also recorded. The analgesic effects were evaluated by using the Children's Hospital of Eastern Ontario Pain Scale.

RESULTS

Forty-nine patients completed the trial. Fifteen patients (60%) in group P received supplementary analgesics within the first 12 h compared to only four patients (16.7%) in group M (P = 0.005). Mean duration of analgesia was 480 +/- 209 and 720 +/- 190 min in group P and group M respectively (P = 0.009). The groups were similar in postoperative side effects.

CONCLUSION

Spinal anesthesia provided by hyperbaric bupivacaine is adequate for distal hypospadias repair in children, but adding 2 microg x kg(-1) intrathecal morphine provides better postoperative pain control when compared to placebo in these children.

A qualitative systematic review of morphine treatment in children with postoperative pain

BACKGROUND

Postoperative pain management in children is often empirical rather than evidence based. Morphine is the pharmacological treatment most widely used and although considered safe for children, adequate scientific data on morphine's pharmacokinetics, efficacy and safety are lacking. This systematic review aimed to evaluate the available literature examining different pediatric morphine regimens with respect to dosage, analgesic efficacy and incidence of side effects.

METHODS

Thirty-six randomized, double-blind controlled clinical trials with 49 comparisons, including multiple dosage regimens and routes of administration were included. The primary outcome measures for analgesic efficacy (pain intensity, time to first analgesic request and need for rescue analgesics) together with the incidence of morphine-related side effects were evaluated qualitatively by significant difference (P < 0.05) as reported in the original investigations.

RESULTS

Overall, significant improvements in the defined outcome measures on analgesic efficacy were only observed when morphine was compared with inactive control interventions. No relation between morphine dosage and analgesic efficacy was detected. The most common morphine-related side effects were vomiting and sedation, with significantly higher incidences observed after morphine administration in half of all comparisons.

CONCLUSIONS

Although several factors may justify its use as first line therapy in many parts of the world, morphine alone is not the most suitable analgesic for postoperative pain in pediatric patients, as it does not have superior analgesic effect and a higher incidence of side effects compared with active control interventions. More standardized clinical trials with multimodal regimens as well as guidelines for evaluating pediatric medicines are desirable in the future.

Anesthesia and postoperative analgesia in pediatric patients undergoing cardiac surgery

Pediatric cardiac anesthesiologists care for patients ranging from premature infants weighing <2 kg to adults requiring surgical intervention for congenital heart disease. Along with their cardiac pathophysiologies, many of these patients also have other co-existing diseases that can affect their anesthetic management. Recent advances in monitoring include non-invasive neuromonitors, such as near-infrared spectroscopy and trans-cranial Doppler, which are assuming increasing importance in intraoperative management, particularly during cardiopulmonary bypass. A variety of anesthetic techniques, including regional anesthesia, can be used to facilitate early extubation in older infants and children with stable postoperative hemodynamics. In addition to regional anesthesia, other modalities for the management of postoperative pain include opioid infusions in critically ill children and the use of patient- or nurse-controlled analgesia pumps. Multiple pain assessment tools are available for children of varying ages and developmental levels to assist in providing appropriate postoperative pain management.

Postoperative continuous intrathecal pain treatment in children after selective dorsal rhizotomy with bupivacaine and two different morphine doses

BACKGROUND

Children undergoing selective dorsal rhizotomy (SDR) experience severe pain postoperatively; a pain related to both the extensive surgical exposure with multilevel laminectomy and nerve root manipulation. We sought to define an optimal dose of continuous intrathecal (IT) morphine and bupivacaine to treat this severe pain. The aim of this study was to compare two different concentrations of morphine in a fixed dose of bupivacaine with regard to the analgesic effect and survey if they differed in side effects.

METHODS

Twenty-six children, aged 2.7-7.4 years undergoing SDR were included in this study. Postoperatively 11 children received a continuous infusion of morphine 0.4 microg x kg(-1) x h(-1) and bupivacaine 40 microg x kg(-1) x h(-1) (low-dose group) and 15, a continuous infusion of morphine 0.6 microg x kg(-1) x h(-1) and bupivacaine 40 microg x kg(-1) x h(-1) (high-dose group). The Behavioral Observational Pain Scale (BOPS) was used to evaluate pain.

RESULTS

Better pain relief was obtained in the high-dose group seen in lower BOPS score compared with the low-dose group [P = 0.03, Fisher's permutation test and P = 0.06 Wilcoxon-Mann-Whitney (WMW) test]. The low-dose group received seven times as much ketobemidone 0.43 +/- 0.54 mg x kg(-1) 48 h(-1) compared with 0.06 +/- 0.09 mg x kg(-1) 48 h(-1) in the high-dose group (P = 0.0005 Fisher's permutation test, P = 0.0017 WMW test). There was no statistical difference in pruritus and postoperative nausea and vomiting between the groups. Respiratory and hemodynamic depression was not found.

CONCLUSION

This study shows that, compared with low-dose, the higher dose of continuous IT morphine combined with bupivacaine, significantly reduce pain score and postoperative intravenous analgesic requirements without increasing adverse effects.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.