Analgesia for acute musculoskeletal trauma: low-dose subcutaneous infusion of ketamine

Pain management in acute musculoskeletal injury: Effect of opioid vs nonopioid medications

BACKGROUND

The use of opioids for pain is linked to an increased risk of developing opioid use disorder, and has resulted in the emergence of the opioid crisis over the last few years.

AIM

The systematic review question is "How does the use of opioid medications in pain management, compared with non-opioid medications, affect pain intensity over the short, intermediate, and long-term in adults with acute traumatic pain?".

METHODS

The protocol was prospectively registered on the International Prospective Register of Systematic Reviews: CRD42021279639. Medline and Google Scholar were electronically searched for controlled peer-reviewed studies published in full, with the PICO framework: P: Adult patients with traumatic injuries, I: Opioid medications, C: Non-opioid medications, O: A minimum clinically important difference (MCID) in pain.

RESULTS

After full-text screening, we included 14 studies in the qualitative synthesis. Of these 14 studies, 12 were randomized clinical trials (RCTs) and 2 were pseudo-RCTs with a total of 2347 patients enrolled. There was heterogeneity in both medication utilized and outcome in these studies; only two studies were homogeneous regarding the type of study conducted, the opioid used, its comparator, and the outcome explored. The MCID was evaluated in 8 studies, while in 6 studies, any measured pain reduction was considered as an outcome. In 11 cases, the setting of care was the Emergency Department; in 2 cases, care occurred out-of-hospital; and in one case, the setting was not well-specified. The included studies were found to have a low-moderate risk of bias.

CONCLUSION

Non-opioids can be considered an alternative to opioids for short-term pain management of acute musculoskeletal injury. Intravenous ketamine may cause more adverse events than other routes of administration.

Narrative Review: Low-Dose Ketamine for Pain Management

Pain is the leading cause of medical consultations and occurs in 50-70% of emergency department visits. To date, several drugs have been used to manage pain. The clinical use of ketamine began in the 1960s and it immediately emerged as a manageable and safe drug for sedation and anesthesia. The analgesic properties of this drug were first reported shortly after its use; however, its psychomimetic effects have limited its use in emergency departments. Owing to the misuse and abuse of opioids in some countries worldwide, ketamine has become a versatile tool for sedation and analgesia. In this narrative review, ketamine's role as an analgesic is discussed, with both known and new applications in various contexts (acute, chronic, and neuropathic pain), along with its strengths and weaknesses, especially in terms of psychomimetic, cardiovascular, and hepatic effects. Moreover, new scientific evidence has been reviewed on the use of additional drugs with ketamine, such as magnesium infusion for improving analgesia and clonidine for treating psychomimetic symptoms. Finally, this narrative review was refined by the experience of the Pain Group of the Italian Society of Emergency Medicine (SIMEU) in treating acute and chronic pain with acute manifestations in Italian Emergency Departments.

Novel uses of ketamine in the emergency department

INTRODUCTION

: Ketamine is gaining renewed interest among healthcare providers due to its novel clinical applications in the emergency department (ED) setting.

AREAS COVERED

: This article provides a comprehensive discussion of ketamine's pharmacological properties, including safety profile and adverse effects, in addition to an overview of current evidence for ketamine (racemic formulation) in the management of ED patients with acute agitation, pain, and depression/suicide ideation.

EXPERT OPINION

: Ketamine is an effective adjunct to opioids, providing greater pain relief than morphine alone. As an analgesic agent, administration of ketamine (0.1-0.3 mg/kg IV) alone can provide analgesia similar to that of morphine in patients with acute visceral and musculoskeletal pain. Moreover, ketamine provides equal analgesic efficacy to morphine in a variety of chronic painful conditions including pain associated with cancer, vaso-occlusive pain crisis associated with sickle cell disease, and in patients with high opioid tolerance and/or opioid dependency. Available literature shows that ketamine (1-2mg/kg IV or 4-5 mg/kg IM) is a safe, rapid (<5 minutes) and effective tranquilization agent for ED patients with acute agitation. Finally, there is growing evidence that suggests ketamine may have a potential utility in the management of patients with self-harm ideation or acute depressive episodes. Intravenous infusion of ketamine (0.5 mg/kg over 40 mins) has been shown to produce an antidepressant effect and decrease in suicidal ideation within 4 hours with effects lasting up to one week.

Advantages of ketamine in pediatric anesthesia

Although ketamine is primarily used for induction and maintenance of general anesthesia, it also presents sedative, amnestic, anesthetics, analgesic, antihyperalgesia, neuroprotective, anti-inflammatory, immunomodulant, and antidepressant effects. Its unique pharmacodynamics and pharmacokinetic properties allow the use of ketamine in various clinical settings including sedation, ambulatory anesthesia, and intensive care practices. It has also adopted to manage acute and chronic pain management. Clinically, ketamine produces dissociative sedation, analgesia, and amnesia while maintaining laryngeal reflexes, with respiratory and cardiovascular stability. Notably, it does not cause respiratory depression, maintaining both the hypercapnic reflex and the residual functional capacity with a moderate bronchodilation effect. In the pediatric population, ketamine can be administered through practically all routes, making it an advantageous drug for the sedation required setting such as placement of difficult vascular access and in uncooperative and oppositional children. Consequently, ketamine is indicated in prehospital induction of anesthesia, induction of anesthesia in potentially hemodynamic unstable patients, and in patients at risk of bronchospasm. Even more, ketamine does not increase intracranial pressure, and it can be safely used also in patients with traumatic brain injuries. This article is aimed to provide a brief and practical summary of the role of ketamine in the pediatric field.

Analgesic Efficacy of Oral Aspirin/Ketamine Combination for Management of Acute Musculoskeletal Pain in the Emergency Department - A Proof of Concept Pilot Study

BACKGROUND

Musculoskeletal pain (MSK) affects one out of three adults and is the most common source of significant long-term pain, physical disability, and under-treatment in the emergency department (ED).

OBJECTIVE

We aimed to assess the analgesic efficacy of a combination of oral VTS-Aspirin® (Vitalis Analgesics, New York, NY) and ketamine in managing acute MSK pain in adult ED patients.

METHODS

This was a prospective, proof-of-concept, single-arm, pilot study evaluating the analgesic efficacy of a single dose of oral combination of VTS-Aspirin and ketamine in adult ED patients with acute moderate-to-severe MSK pain. The primary outcome included the difference in pain scores on an 11-point numeric pain rating scale at 60 min. Secondary outcomes included the need for rescue analgesia, the occurrence of adverse events at 60 min, and a change in pain scores at 120 min.

RESULTS

We enrolled 25 subjects in the study. The mean baseline pain score was 8.6 and the mean pain score at 60 min decreased to 4.8. The oral ketamine dose ranged from 24 mg to 50 mg, with a mean dose of 37.8 mg. No clinically concerning changes in vital signs were noted. No serious adverse events occurred in any of the subjects. Majority of adverse effects were transient and weak in intensity.

CONCLUSION

We demonstrated that administration of an oral combination of VTS-Aspirin and ketamine to adult ED patients with acute MSK pain resulted in clinically significant pain relief in 80% of enrolled subjects.

The Expanding Role of Ketamine in the Emergency Department

Patients frequently come to the emergency department for pain. For decades, ketamine has been used in the emergency department for procedural sedation but is now receiving attention as a potential alternative to opioids because of its unique analgesic effects. Additionally, ketamine's dissociative properties have made it a popular choice for sedating profoundly agitated patients. In this narrative review, these new roles for ketamine in the emergency department are discussed.

A Systematic Review and Meta-analysis of Ketamine as an Alternative to Opioids for Acute Pain in the Emergency Department

BACKGROUND

Opioids are commonly prescribed in the emergency department (ED) for the treatment of acute pain. Analgesic alternatives are being explored in response to an epidemic of opioid misuse. Low-dose ketamine (LDK) is one opioid alternative for the treatment of acute pain in the ED.

OBJECTIVES

This systematic review and meta-analysis sought to quantify whether LDK is an effective and safe opioid alternative for acute pain reduction in adults in the ED setting. (PROSPERO Registration Number CRD42017065303).

METHODS

This was a systematic review of randomized controlled trials comparing intravenous opioids to LDK for relief of acute pain in the ED. Studies where the control group initially received opioids prior to ketamine were excluded. A research librarian designed the electronic search strategy. Changes in visual analog scale or numeric rating scale pain scales were analyzed to determine the relative effects of LDK and opioids in the treatment of acute pain.

RESULTS

Three studies met the criteria for inclusion in this meta-analysis. Compared to pain scale reduction with morphine, ketamine was not inferior (relative reduction = 0.42, 95% confidence interval = -0.70 to 1.54). No severe adverse events were reported in any study, but higher rates of nonsevere adverse events were observed with ketamine.

CONCLUSIONS

Ketamine is noninferior to morphine for the control of acute pain, indicating that ketamine can be considered as an alternative to opioids for ED short-term pain control.

Slow Infusion of Low-dose Ketamine Reduces Bothersome Side Effects Compared to Intravenous Push: A Double-blind, Double-dummy, Randomized Controlled Trial

OBJECTIVE

We compared the analgesic efficacy and incidence of side effects when low-dose (0.3 mg/kg) ketamine (LDK) is administered as a slow infusion (SI) over 15 minutes versus an intravenous push (IVP) over 1 minute.

METHODS

This was a prospective, randomized, double-blind, double-dummy, placebo-controlled trial of adult ED patients presenting with moderate to severe pain (numerical rating scale [NRS] score ≥ 5). Patients received 0.3 mg/kg ketamine administered either as a SI or a IVP. Our primary outcome was the proportion of patients experiencing any psychoperceptual side effect over 60 minutes. A secondary outcome was incidence of moderate or greater psychoperceptual side effects. Additional outcomes included reduction in pain NRS scores at 60 minutes and percent maximum summed pain intensity difference (%SPID).

RESULTS

Fifty-nine participants completed the study. A total of 86.2% of the IVP arm and 70.0% of the SI arm experienced any side effect (difference = 16.2%, 95% confidence interval [CI] = -5.4 to 37.8). We found a large reduction in moderate or greater psychoperceptual side effects with SI administration-75.9% reported moderate or greater side effects versus 43.4% in the SI arm (difference = 32.5%, 95% CI = 7.9 to 57.1). Additionally, the IVP arm experienced more hallucinations (n = 8, 27.6%) than the SI arm (SI n = 2, 6.7%, difference = 20.9%, 95% CI = 1.8 to 43.4). We found no significant differences in analgesic efficacy. At 60 minutes, the mean %SPID values in the IVP and SI arms were 39.9 and 33.5%, respectively, with a difference of 6.5% (95% CI = -5.8 to 18.7).

CONCLUSION

Most patients who are administered LDK experience a psychoperceptual side effect regardless of administration via SI or IVP. However, patients receiving LDK as a SI reported significantly fewer moderate or greater psychoperceptual side effects and hallucinations with equivalent analgesia.

Ketamine as an Analgesic Adjuvant in Adult Trauma Intensive Care Unit Patients With Rib Fracture

Background: Rib fracture associated pain is difficult to control. There are no published studies that use ketamine as a therapeutic modality to reduce the amount of opioid to control rib fracture pain. Objective: To examine the analgesic effects of adjuvant ketamine on pain scale scores in trauma intensive care unit (ICU) rib fracture. Methods: This retrospective, case-control cohort chart review evaluated ICU adult patients with a diagnosis of ≥1 rib fracture and an Injury Severity Score >15 during 2016. Patients received standard-of-care pain management with the physician’s choice analgesics with or without ketamine as a continuous, fixed, intravenous infusion at 0.1 mg/kg/h. Results: A total of 15 ketamine treatment patients were matched with 15 control standard-of-care patients. Efficacy was measured via Numeric Pain Scale (NPS)/Behavioral Pain Scale (BPS) scores, opioid use, and ICU and hospital length of stay. Safety of ketamine was measured by changes in vital signs, adverse effects, and mortality. Average NPS/BPS, severest NPS/BPS, and opioid use were lower in the ketamine group than in controls (NPS: 4.1 vs 5.8, P < 0.001; severest NPS: 7.0 vs 8.9, P = 0.004; opioid use: 2.5 vs 3.5 mg morphine equivalents/h/d, P = 0.015). No difference was found between the cohort’s length of stay or mortality. Average diastolic blood pressure was higher in the treatment group versus the control group (75.3 vs 64.6 mm Hg, P = 0.014). Conclusion: Low-dose ketamine appears to be a safe and effective adjuvant option to reduce pain and decrease opioid use in rib fracture.

Systematic review of the use of low-dose ketamine for analgesia in the emergency department

Objectives

The aim of the study is to determine the performance of low-dose ketamine (LDK) as an analgesic for acute pain management in adult patients in the emergency department (ED).

Methods

We systematically reviewed electronic databases, grey literature, conference abstracts, and clinical trial registries. Two independent reviewers identified eligible studies. These selections were subsequently reviewed by one reviewer who identified the final eligible studies, using refined inclusion and exclusion criteria. Our outcome measures included the analgesic effect of LDK, need for rescue analgesia, and neuropsychological adverse events secondary to LDK use. We assessed inter-rater agreement using kappa statistics and proposed a treatment recommendation using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) software. Heterogeneity among studies precluded meta-analysis.

Results

Our electronic search identified 1,408 records; 44 were selected for full evaluation (kappa=0.70), and 8 were included after the final review. All six randomized controlled trials and two observational studies were set in the ED where LDK was administered to adult patients ( >18 years old) exclusively for pain management. All studies had an overall low risk of bias. There was extensive variation in the dose and route of LDK used (0.1-0.7 mg/kg SC/IV/IM), administration protocols, and use of adjunct analgesia. Overall, most studies reported a significant analgesic effect of LDK with occasional need for rescue analgesia and mild-to-moderate adverse events (dizziness, dysphoria, and confusion).

Conclusion

There are moderate to low quality data supporting LDK as an alternative analgesic in the ED with the potential for minimal requirement of rescue analgesia and self-limited neuropsychological adverse events.

Ketamine as an Adjunct to Opioids for Acute Pain in the Emergency Department: A Randomized Controlled Trial

OBJECTIVES

This study had five objectives: 1) to measure and compare total opioid use and number of opioid doses in patients treated with opioids versus ketamine in conjunction with opioids; 2) to measure pain scores up to 2 hours after presentation in the ED patient with pain, comparing standard opioid pain control to ketamine in conjunction with opioids; 3) to compare patient satisfaction with pain control using opioids alone versus ketamine in conjunction with opioids; 4) to monitor and compare side effects in patients treated with opioids versus ketamine in conjunction with opioids; and 5) to identify effect variation between different subgroups of patients, with the purpose of focusing future research. We hypothesized that low-dose ketamine, compared to placebo, as an adjunctive treatment to opioids would result in better pain control over 2 hours and greater patient satisfaction with pain control; further, this protocol will result in a lower opioid dosage over 2 hours.

METHODS

This was a randomized, double-blinded, placebo-controlled trial at a single academic emergency department evaluating the use of ketamine versus placebo in conjunction with opioids for moderate to severe pain. Subjects with a continued high level of pain after an initial dose of opioid analgesia were randomized to receive either 0.1 mg/kg ketamine or placebo prior to protocol-based dosing of additional opioid analgesia, if required. Over 120 minutes, subjects were assessed for pain level (0-10), satisfaction with pain control (0-4), side effects, sedation level, and need for additional pain medication. Total opioid dose, including the initial dose, was compared between groups.

RESULTS

Sixty-three subjects were randomized to the placebo group and 53 to the ketamine group. No significant differences were found in demographics between the groups. Patients receiving ketamine reported lower pain scores over 120 minutes than patients receiving placebo (p = 0.015). Total opioid dose was lower in the ketamine group (mean ± SD = 9.95 ± 4.83 mg) compared to placebo (mean ± SD = 12.81 ± 6.81 mg; p = 0.02). Satisfaction did not differ between groups. Fewer patients in the ketamine group required additional opioid doses. More patients reported light-headedness and dizziness in the ketamine group.

CONCLUSIONS

Ketamine, as an adjunct to opioid therapy, was more effective at reducing pain over 120 minutes and resulted in a lower total opioid dose as well as fewer repeat doses of analgesia. More side effects were reported in the ketamine group (51% vs. 19%), but the side effect profile appears tolerable.

The use of subdissociative-dose ketamine for acute pain in the emergency department

OBJECTIVES

Ketamine is a well-known anesthetic with its use trailing back to the 1960s. It has antagonistic effects at the N-methyl-d-aspartate receptor. There is emerging literature to suggest the use of subdissociative-dose ketamine (SDDK) for pain reduction. This evidence-based review evaluates the evidence regarding the use of SDDK for acute pain control in the emergency department (ED).

METHODS

The MEDLINE and EMBASE databases were searched. Randomized controlled trials (RCTs) that described or evaluated the use of SDDK for acute pain in the ED were included. Literature was excluded if it was not published in English. Duplicate articles, unpublished reports, abstracts, and review articles were also excluded. Quality assessment and evaluation of literature were evaluated based on the GRADE criteria. The primary outcome of interest in this review was the difference in pain score from baseline to cutoff time as specified in the studies. Secondary outcome measures were the incidence of adverse events and reduction in the amount of adjuvant opioids consumed by patients who received SDDK.

RESULTS

Four RCTs met the inclusion criteria, which enrolled a total of 428 patients. Three adult trials and one pediatric trial were identified. The level of evidence for the individual trials ranged from low to moderate. A significant reduction in pain scores was only found in two of the four trials. One trial found a significant reduction in mean pain scores when ketamine was compared to morphine (p < 0.05). Another trial reported a significant decrease in mean distress scores, favoring SDDK over fentanyl (1.0 vs. 2.7, p < 0.05). One trial found a significant reduction in the amount of morphine consumed, favoring ketamine over placebo (0.14 mg/kg, 95% confidence interval [CI] = 0.13 to 0.16 mg/kg vs. 0.2 mg/kg, 95% CI = 0.18 to 0.22 mg/kg; p < 0.001). An emergence phenomenon was reported in one trial.

CONCLUSIONS

Four RCTs with methodologic limitations failed to provide convincing evidence to either support or refute the use of SDDK for acute pain control in the ED.

Continuous Infusion of Ketamine for Out-of-hospital Isolated Orthopedic Injuries Secondary to Trauma: A Randomized Controlled Trial

Abstract Objective. Although ketamine has recently been demonstrated to provide a morphine-sparing effect, no previous study reports the effect of continuous infusion of ketamine for analgesia in out-of-hospital environments. The aim of this study was to compare the effect of a continuous infusion of ketamine (IK group) vs. a continuous infusion of saline (IS group) on morphine requirements in out-of-hospital trauma patients suffering from severe acute pain. Methods. In this prospective, multicenter, randomized, single-blind clinical study, patients suffering from isolated orthopedic injuries secondary to trauma with severe acute pain received a low-dose intravenous (IV) bolus of ketamine (0.2 mg·kg^-1) combined with an IV bolus of morphine (0.1 mg·kg^-1) and were randomized either in the IK group (IV continuous infusion of ketamine 0.2 mg·kg^-1·h^-1), or in the IS group (IV continuous infusion of saline at the same volume). The primary endpoint was morphine requirements in terms of total dose of morphine (excluding the baseline bolus) injected at the end of prehospital emergency care at hospital admission (final time, Tf). The secondary endpoint was evaluation of pain with visual analogic scale (VAS). Results. Sixty-six patients were enrolled. Total morphine dose was not significantly reduced with continuous infusion of ketamine (0.048 [0.000; 0.150] vs. 0.107 [0.052; 0.150] in IK and IS groups), with similar mean duration of care (median 35.0 min). Analgesia was as efficient without any significant difference in VAS at Tf between groups (3.1 ± 2.3 (IK group) vs. 3.7 ± 2.7 (IS group), p = 0.5). Conclusions. Continuous ketamine infusion did not reduce morphine requirements in severe acute pain trauma patients in the out-of-hospital emergency settings.

Review on pharmacological pain management in trauma patients in (pre-hospital) emergency medicine in the Netherlands

Pain is one of the main complaints of trauma patients in (pre-hospital) emergency medicine. Significant deficiencies in pain management in emergency medicine have been identified. No evidence-based protocols or guidelines have been developed so far, addressing effectiveness and safety issues, taking the specific circumstances of pain management of trauma patients in the chain of emergency care into account. The aim of this systematic review was to identify effective and safe initial pharmacological pain interventions, available in the Netherlands, for trauma patients with acute pain in the chain of emergency care. Up to December 2011, a systematic search strategy was performed with MeSH terms and free text words, using the bibliographic databases CINAHL, PubMed and Embase. Methodological quality of the articles was assessed using standardized evaluation forms. Of a total of 2328 studies, 25 relevant studies were identified. Paracetamol (both orally and intravenously) and intravenous opioids (morphine and fentanyl) proved to be effective. Non-steroidal anti-inflammatory drugs (NSAIDs) showed mixed results and are not recommended for use in pre-hospital ambulance or (helicopter) emergency medical services [(H)EMS]. These results could be used for the development of recommendations on evidence-based pharmacological pain management and an algorithm to support the provision of adequate (pre-hospital) pain management. Future studies should address analgesic effectiveness and safety of various drugs in (pre-hospital) emergency care. Furthermore, potential innovative routes of administration (e.g., intranasal opioids in adults) need further exploration.

Ketamine activates the L-arginine/Nitric oxide/cyclic guanosine monophosphate pathway to induce peripheral antinociception in rats

BACKGROUND

The involvement of the L-arginine/nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway in antinociception has been implicated as a molecular mechanism of antinociception produced by several antinociceptive agents, including μ-, κ-, or δ-opioid receptor agonists, nonsteroidal analgesics, cholinergic agonist, and α2C adrenoceptor agonist. In this study, we investigated whether ketamine, a dissociative anesthetic N-methyl-D-aspartate receptor antagonist, was also capable of activating the L-arginine/NO/cGMP pathway and eliciting peripheral antinociception.

METHODS

The rat paw pressure test was used, with hyperalgesia induced by intraplantar injection of prostaglandin E2. All drugs were locally administered into the right hindpaw of male Wistar rats.

RESULTS

Ketamine (10, 20, 40, 80 μg/paw) elicited a local antinociceptive effect that was antagonized by the nonselective NOS inhibitor L-NOARG (12, 18, and 24 μg/paw) and by the selective neuronal NOS inhibitor L-NPA (12, 18, and 24 μg/paw). In another experiment, we used the inhibitors L-NIO and L-NIL (24 μg/paw) to selectively inhibit endothelial and inducible NOS, respectively. These 2 drugs were ineffective at blocking the effects of the peripheral ketamine injection. In addition, the level of nitrite in the homogenized paw indicated that exogenous ketamine is able to induce NO release. The soluble guanylyl cyclase inhibitor ODQ (25, 50, and 100 μg/paw) blocked the action of ketamine, and the cGMP-phosphodiesterase inhibitor zaprinast (50 μg/paw) enhanced the antinociceptive effects of low-dose ketamine (10 μg/paw).

CONCLUSIONS

Our results suggest that ketamine stimulates the L-arginine/NO/cyclic GMP pathway via neuronal NO synthase to induce peripheral antinociceptive effects.

Dissociative conscious sedation, an alternative to general anesthesia for laparoscopic peritoneal dialysis catheter implantation: a randomized trial comparing intravenous and subcutaneous ketamine

Laparoscopy is an effective method of implantation for peritoneal dialysis (PD) catheters. Use of the laparoscopic technique is increasing because of its potential advantages over other techniques. In most patients, selection for PD is based on negative criteria, and because of the need for general anesthesia, the laparoscopic technique can be life-threatening in these patients. On the other hand, local anesthesia is insufficient for laparoscopic catheter implantation. To avoid the need for general anesthesia and to achieve patient safety and satisfaction, we designed a type of conscious sedation (dissociative conscious sedation) and compared the efficacy of subcutaneous (SC) and intravenous (IV) ketamine added to narcotics in patients scheduled for laparoscopic implantation of a PD catheter.

METHODS

Our prospective randomized double-blind study enrolled 60 adult patients with chronic renal failure who were scheduled for laparoscopic implantation of a PD catheter. Patients were randomly assigned to one of two groups: one receiving IV ketamine, and the other receiving SC ketamine. In both groups, patients were premedicated with IV midazolam 0.015 mg/kg, fentanyl 1-2 μg/kg, and lidocaine 1.5 mg/kg. Patients then received 0.6 mg/kg ketamine either intravenously (IV group) or by subcutaneous injection at the anterior aspect of the forearm (SC group). If systolic blood pressure (BP) increased more than 20% from baseline or exceeded 170 mmHg, IV nitroglycerine (TNG) 50 μg was administered incrementally (repeated 50-μg doses). After a desirable level of conscious sedation was achieved, local anesthesia and nitrous oxide pneumoperitoneum were applied, and the PD catheter was implanted under laparoscopic guidance. Heart rate and BP were measured throughout the procedure. Adverse effects and recovery events were recorded.

RESULTS

All patients tolerated the procedure well. Administration of TNG was significantly more frequent in the IV ketamine group. Pain intensity during the surgery was similar in both groups. Both groups were comparable with regard to heart rate, but patients in the SC ketamine group had a significantly lower systolic BP at the 2nd measurement and a lower rate-pressure product at the 2nd, 4th, and 5th measurements. All patients in the SC ketamine group were cooperative during surgery and experienced uneventful recoveries; mild hallucinations were observed in 5 patients in the IV ketamine group. In the IV ketamine group, 3 patients lost the ability to cooperate during surgery. All catheters were successfully placed.

CONCLUSIONS

Dissociative conscious sedation is an acceptable alternative to general anesthesia in laparoscopic implantation of the PD catheter. Ketamine by the SC route is as effective as, but safer than, IV ketamine.

The evolution of ketamine applications in children

Ketamine has found many applications in pediatric anesthetic practice. Insights into the mechanism of action and the pharmacokinetics and pharmacodynamics of its isomers have led to a re-evaluation of this drug, expanding the range of applications in children. Ketamine is a remarkably versatile drug that can be administered through almost any route. It can also be used for different purposes. The aim of this review is to look at the possible applications of this drug in children.

Low dose ketamine: a therapeutic and research tool to explore N-methyl-D-aspartate (NMDA) receptor-mediated plasticity in pain pathways

Ketamine is a dissociative anaesthetic that has been used in the clinic for many years. At low, sub-anaesthetic doses, it is a relatively selective and potent antagonist of the N-methyl-D-aspartate (NMDA) receptor. It belongs to the class of uncompetitive antagonists and blocks the receptor by binding to a specific site within the NMDA receptor channel when it is open. Like other compounds of this class, ketamine can cause hallucinations or other untoward central effects which limit its use in the clinic. Nevertheless, because of the evidence on the importance of NMDA receptor-mediated pLasticity in chronic pain, low doses of ketamine have been explored in a wide range of pain conditions. The majority of studies with ketamine have shown efficacy; however, it has not been possible to separate safely the pain relief from the side effects of the drug. Hence, clinical use of ketamine as a pain treatment is very limited. Nevertheless, ketamine has served as a useful tool to provide a compelling rationale for developing other NMDA antagonists. Some of the new compounds of this class, particularly those acting at the NR2B subtype of the NMDA receptor, have shown promise in preclinical and clinical studies.

Management of severe acute pain in emergency settings: ketamine reduces morphine consumption

OBJECTIVE

The aim of the study was to compare in emergency settings 2 analgesic regimens, morphine with ketamine (K group) or morphine with placebo (P group), for severe acute pain in trauma patients.

METHODS

This was a prospective, multicenter, randomized, double-blind, clinical trial. Seventy-three trauma patients with a severe acute pain defined as a visual analog scale (VAS) score of at least 60/100 were enrolled. Patients in the K group received 0.2 mg x kg(-1) of intravenous ketamine over 10 minutes, and patients in the P group received isotonic sodium chloride solution. In both groups, patients were given an initial intravenous morphine injection of 0.1 mg x kg(-1), followed by 3 mg every 5 minutes. Efficient analgesia was defined as a VAS score not exceeding 30/100. The primary end points were morphine consumption and VAS at 30 minutes (T30).

RESULTS

At T30, morphine consumption was significantly lower in the K group vs the P group, with 0.149 mg x kg(-1) (0.132-0.165) and 0.202 mg x kg(-1) (0.181-0.223), respectively (P < .001). The VAS score at T30 did not differ significantly between the 2 groups, with 34.1 (25.6-42.6) in the K group and 39.5 (32.4-46.6) in the P group (P = not significant).

CONCLUSION

Ketamine was able to provide a morphine-sparing effect.

Adjunct continuous intravenous ketamine infusion for postoperative pain relief following posterior spinal instrumentation for correction of scoliosis: a case report

Providing effective analgesia is challenging for correction of idiopathic scoliosis, as nonsteroidal anti-inflammatory drugs and epidural anesthesia are controversial and large-dose opioids can cause significant side effects. Perioperative adjuvant low-dose ketamine has been shown to provide good supplementary analgesia as well as to potentially spare opioid consumption. Ketamine may also improve early ease of mobility without addition of any noticeable adverse effects. This case describes the combined use of a continuous low-dose ketamine infusion and patient-controlled analgesia (PCA) morphine for postoperative analgesia in an adolescent girl undergoing posterior spinal instrumentation and correction of scoliosis. The patient had excellent postoperative analgesia and was able to participate in early rehabilitation. The opioid-sparing effect of ketamine was not demonstrated in this case. Further study of continuous low-dose ketamine infusions in this patient population would be beneficial to provide more evaluation of the efficacy and tolerability of ketamine and of its opioid-sparing potential.

Earthquake injuries and the use of ketamine for surgical procedures: the Kashmir experience

The October 8, 2005 earthquake in Northern Pakistan had widespread destructive effects throughout the northern subcontinent. Large numbers of people were killed or severely injured and many medical services destroyed. This report describes the experience of the only standing surgical hospital in the Kashmir region of Bagh District. More than 1,500 people were triaged in 72 hours, many critically injured; 78.4% of patients had upper or lower limb injuries; 50.3% of patients had fractures, mainly closed; 37% of patients required extensive wound debridements. A total of 149 patients received emergency surgery using ketamine anaesthesia with benzodiazepine premedication. This was found to be safe, effective and with a low incidence of major adverse effects. We recommend that ketamine anaesthesia be encouraged in disaster area surgery, particularly in under-resourced regional centres.

Pharmacokinetics and clinical effects of a subanesthetic continuous rate infusion of ketamine in awake horses

OBJECTIVE

To determine the pharmacokinetics and clinical effects of a subanesthetic, continuous rate infusion of ketamine administered to healthy awake horses.

ANIMALS

8 adult horses.

PROCEDURES

Ketamine hydrochloride was administered to 2 horses, in a pilot study, at rates ranging from 0.4 to 1.6 mg/kg/h for 6 hours to determine an appropriate dose that did not cause adverse effects. Ketamine was then administered to 6 horses for a total of 12 hours (3 horses at 0.4 mg/kg/h for 6 hours followed by 0.8 mg/kg/h for 6 hours and 3 horses at 0.8 mg/kg/h for 6 hours followed by 0.4 mg/kg/h for 6 hours). Concentration of ketamine in plasma, heart rate, respiratory rate, blood pressure, physical activity, and analgesia were measured prior to, during, and following infusion. Analgesic testing was performed with a modified hoof tester applied at a measured force to the withers and radius.

RESULTS

No signs of excitement and no significant changes in the measured physiologic variables during infusion rates of 0.4 and 0.8 mg of ketamine/kg/h were found. At 6 hours following infusions, heart rate and mean arterial pressure were decreased, compared with preinfusion measurements. An analgesic effect could not be demonstrated during or after infusion. Pharmacokinetic variables for 0.4 and 0.8 mg/kg/h infusions were not significantly different.

CONCLUSIONS AND CLINICAL RELEVANCE

Ketamine can be administered to awake horses at 0.4 or 0.8 mg/kg/h without adverse behavioral effects. The observed pharmacokinetic values are different than those reported for single-dose IV bolus administration of this drug.

The role of ketamine in pain management

Ketamine is a dissociative anaesthetic; its mechanism of action is primarily an antagonism of the N-methyl-D-aspartate (NMDA) receptor. The role of ketamine, in particular in lower sub-anaesthetic doses, has recently gained increasing interest in pain management. It has been studied in a considerable number of trials and analysed in meta-analyses and systematic reviews. Based on these data, the primary role of ketamine in such low doses is as an 'anti-hyperalgesic', 'anti-allodynic' or 'tolerance-protective' agent. It therefore has a role in the treatment of opioid resistant or 'pathological' pain (central sensitisation with hyperalgesia or allodynia, opioid induced hyperalgesia, neuropathic pain) rather than as an 'analgesic' in its own right. Low dose ketamine also has 'preventive analgesia' properties. Furthermore, in higher doses it provides effective and safe sedation and analgesia for painful procedures. The place of ketamine in the treatment of chronic pain and the effects of long-term medicinal use remain unclear.

Investigation of the potentiation of the analgesic effects of fentanyl by ketamine in humans: a double-blinded, randomised, placebo controlled, crossover study of experimental pain[ISRCTN83088383]

BACKGROUND: Despite preclinical evidence suggesting a synergistic interaction between ketamine and opioids promoting analgesia, several clinical trials have not identified dosing regimens capable of eliciting a benefit in the co-administration of ketamine with opioids. METHODS: Ten healthy volunteers participated in a double blinded, randomised, placebo controlled, crossover laboratory study in order to determine whether a low dose of ketamine potentiated the antinociceptive effect of fentanyl without causing an increase in sedative effects. A battery of tests was used to assess both nociception and sedation including electrical current, pressure, thermal stimuli, psychometric tests, and both subjective and objective scores of sedation. Target controlled infusions of the study drugs were used. Ketamine and fentanyl were administered alone and in combination in a double-blinded randomised crossover design. Saline was used as the control, and propofol was used to validate the tests of sedation. Cardiovascular and respiratory parameters were also assessed. RESULTS: The electrical current pain threshold dose response curve of fentanyl combined with ketamine was markedly steeper than the dose response curve of fentanyl alone. While a ketamine serum concentration of 30 ng/ml did not result in a change in electrical pain threshold when administered alone, when it was added to fentanyl, the combination resulted in greater increase in pain threshold than that of fentanyl administered alone. When nociception was assessed using heat and pressure stimuli, ketamine did not potentiate the anti-nociceptive effect of fentanyl. There was no difference between the sedative effect of fentanyl and fentanyl in combination with ketamine as assessed by both subjective and objective measures of sedation. Cardiovascular and respiratory parameters were unaffected by the study drugs at the doses given. CONCLUSION: A serum concentration of ketamine that did not alter indices of sedation potentiated the antinociceptive effect of fentanyl. This potentiation of antinociception occurred without an increase in sedation suggesting that low steady doses of ketamine (30-120 ng/ml) might be combined with mu opioid agonists to improve their analgesic effect in a clinical setting. (296 words).

Safety and efficacy of intranasal ketamine for the treatment of breakthrough pain in patients with chronic pain: a randomized, double-blind, placebo-controlled, crossover study

Few placebo-controlled trials have investigated the treatment of breakthrough pain (BTP) in patients with chronic pain. We evaluated the efficacy and safety of intranasal ketamine for BTP in a randomized, double-blind, placebo-controlled, crossover trial. Twenty patients with chronic pain and at least two spontaneous BTP episodes daily self-administered up to five doses of intranasal ketamine or placebo at the onset of a spontaneous BTP episode (pain intensity > or =5 on a 0-10 scale). Two BTP episodes at least 48 h apart were treated with either ketamine or placebo. Patients reported significantly lower BTP intensity following intranasal ketamine than after placebo (P < 0.0001) with pain relief within 10 min of dosing and lasting for up to 60 min. No patient in the ketamine group required his/her usual rescue medication to treat the BTP episode, while seven out of 20 (35%) patients in placebo group did (P = 0.0135). Intranasal ketamine was well tolerated with no serious adverse events. After ketamine administration, four patients reported a transient change in taste, one patient reported rhinorrhea, one patient reported nasal passage irritation, and two patients experienced transient elevation in blood pressure. A side effect questionnaire administered 60 min and 24 h after drug or placebo administration elicited no reports of auditory or visual hallucinations. These data suggest that intranasal administration of ketamine provides rapid, safe and effective relief for BTP.

Effective analgesic modalities for ambulatory patients

The introduction of government-mandated standards for pain management has focused our attention on postoperative pain. With the recent JACHO standards' for ambulatory surgery, it is imperative that all health care workers who care for these patients are familiar with appropriate pain management. Developments in our understanding of the pathophysiology of acute pain have further enhanced our ability to improve pain management for postoperative ambulatory patients. This has led to the concept of preventive analgesia (inhibition of physiological and pathological secondary inflammatory pain). Extensive work has shown that this is best achieved using a multimodel approach usually consisting of an NSAID, opioid, and local anesthetic. NMDA antagonists (ketamine, dextromethorphan) and alpha-2 agnoists (clonodine) show potential supplements to further enhance pain management, especially if given preemptively. Nonpharmacological intervention such as cold therapy or acupuncture may also be considered. The armanentarium for effective pain management has improved substantially over the past few years. The challenge is for health care workers to implement these therapies to obtain optimum pain management in ambulatory surgical patients.

Effect of the addition of ketamine to morphine in patient-controlled analgesia

This randomised, double-blind, prospective study compared morphine (1 mg x m(-1)) with the combination of morphine (1 mg x m(-1)) and ketamine (0.75 mg x m(-1)) via a patient-controlled analgesia system (PCAS) for postoperative pain control. A total of 42 female patients, ASA grade I and II, undergoing elective total abdominal hysterectomy was studied. During a standardised anaesthetic, a loading dose from the PCA syringe of 10 ml x m(-2) of body surface area was given. A PCAS with a background infusion was commenced postoperatively. Pain and side-effects were assessed using numerical scoring systems and cardiovascular and respiratory parameters were recorded. There was no statistically significant difference between the groups in total morphine consumption or pain scoring. Side-effect profiles and time to mobilisation were similar. This study concludes that the addition of ketamine to morphine, in this dosage regimen, administered via PCAS for postoperative pain control, does not confer benefit following total abdominal hysterectomy.

Combined xylazine and ketamine as an analgesic regimen in sheep

OBJECTIVE

To determine whether low dose xylazine with ketamine reduces the concentrations of cortisol and prolactin in sheep postoperatively and to characterise the effects of the drugs on behaviour during recovery.

DESIGN

Analysis of variance was used to compare the effects of anaesthesia, surgery and combined ketamine/xylazine treatment on the plasma cortisol and prolactin concentrations and on behavioural variables in pregnant ewes subjected to abdominal surgery.

PROCEDURE

Twelve ewes were randomly assigned to receive either ketamine/xylazine or placebo in association with anaesthesia and surgery. Both groups of ewes underwent anaesthesia alone followed a week later by anaesthesia with laparotomy and hysterotomy. Plasma cortisol and prolactin concentrations were assayed during these procedures and for 5 days afterwards. Behavioural observations were made remotely during recovery from anaesthesia and anaesthesia plus surgery.

RESULTS

The concentrations of cortisol in the plasma of pregnant ewes undergoing surgery were increased by preoperative handling and the onset of thiopentone/halothane anaesthesia, with a further increase during surgery (P = 0.033). Cortisol concentrations decreased over the first four postoperative hours (P = 0.029) and were normal by 24 h. The drug treatment did not affect the immediate responses of ewes to anaesthesia or surgery, although treated ewes had lower cortisol concentrations than saline-treated controls over the first five postoperative days (P = 0.018). Prolactin concentrations increased in response to anaesthesia (P = 0.047), but were not affected by surgery or the drug treatment. Drug-treated ewes had prolonged sleeping time after surgery (P = 0.002), but they took no longer to stand than saline-treated controls and required fewer attempts to stand successfully (P = 0.025).

CONCLUSION

At the doses used, ketamine and xylazine did not mitigate the immediate endocrine consequences of surgery but the behavioural data provide a basis for further investigations that may lead to improvements in analgesic treatments.

Adjunctive analgesic therapy

Adjuvant analgesics are drugs that have weak or nonexistent analgesic action when administered alone but can enhance analgesic actions when coadministered with known analgesic agents. Such agents are often administered in cases of refractory pain. For some chronic pain syndromes, however, they may constitute a first-line approach. Because pain is such an individual experience, analgesic regimens may require several drugs at varying dosages to confer a comfortable state. Adjunctive therapies such as the tricyclic antidepressants, anticonvulsants, N-methyl-D-aspartic acid receptor antagonists and low-dose intravenous local anesthetics, to name a few, have proved to be efficacious in relieving certain types of pain, especially neuropathic and cancer pain. Their use in animals is increasing, with anecdotal reports of some success.

Use and efficacy of low-dose ketamine in the management of acute postoperative pain: a review of current techniques and outcomes

Ketamine hydrochloride is a well known general anesthetic and short acting analgesic in use for almost 3 decades. The role of the NMDA receptor in the processing of nociceptive input has led naturally to renewed clinical interest in N-methyl-D-aspartate (NMDA) receptor antagonists such as ketamine. This paper reviews the use and efficacy of low-dose ketamine in the management of acute postoperative pain. The literature was obtained from a computer search of the MEDLINE database from 1966 through December 1998. Studies were included for review if they were randomized, prospective, controlled, double-blind and reported pain scores. We evaluate the clinical literature and discuss the efficacy of low-dose ketamine in the management of acute postoperative pain when administered alone or in conjunction with other agents via the oral, intramuscular, subcutaneous, intravenous and intraspinal routes. Low-dose ketamine is defined as a bolus dose of less than 2 mg/g when given intramuscularly or less than 1 mg/kg when administered via the intravenous or epidural route. For continuous i.v. administration low-dose ketamine is defined as a rate of < or =20 microg/kg per min. We conclude that ketamine may provide clinicians with a tool to improve postoperative pain management and to reduce opioid related adverse effects. The evidence suggests that low-dose ketamine may play an important role in postoperative pain management when used as an adjunct to local anesthetics, opioids, or other analgesic agents. Further research is required in the following areas: (a) dose-finding studies for ketamine as an adjunct to opioids and local anesthetics (b) efficacy and optimal route of administration (c) the role of S(+)-ketamine; (d) the influence of ketamine on long-term outcome such as chronic pain (e) long-term physical and chemical stability of mixtures containing ketamine (f) spinal toxicity of ketamine and (g) effects of low-dose ketamine on cognitive and memory functioning after surgery.

Analgesia for trauma and burns

This article has described the physiologic impact of trauma- and burn-related pain as well as the effect of a clinician's choice of analgesic method, using the specific example of regional analgesia for pain caused by chest trauma. It has been observed that trauma exerts a holistic influence upon the organism, marshalling reflexes, multi-system physiologic stress responses, and psychologic responses--some adaptive and others maladaptive. There is reason to consider that timely analgesia can intervene in this dynamic process and interdict the establishment of a debilitated state. A key finding of these studies is that a report of pain relief may not be the best outcome measure since the choice of analgesic method(s) has a significant impact on the secondary effects of pain. Although extrapolated from studies of perioperative pain, findings do suggest that there may be a critical period of time during which the secondary effects of a painful stimulus may be attenuated or reversed. How long this period of reversibility exists has not been determined, so planning for the level and goals of analgesia intervention should occur early on. Analgesia should be viewed not only as a humanitarian gesture, but also a therapeutic maneuver with the goal being the early restoration of function and the mitigation of a chronic debilitated state. There is scattered evidence that regional analgesic techniques using local anesthetics have some advantages over other analgesic modalities, particularly in the trauma patient with pulmonary compromise; however, as with other medical interventions, one should develop a strategic plan of application which includes consideration of potential complications and side effects, in addition to the potential therapeutic effects. The traumatized body, as well as the attending physician, must deal with inflammation, the neurohumoral reaction, musculoskeletal reflex responses, and numerous other reactions designed to stabilize an acutely destabilized systemic entity. Multimodal analgesia, with the balanced use of systemic and regional medications, has given the best short- and long-term results in studies of postthoracotomy pain. The use of a similar combined plan for posttraumatic analgesia seems logical; however, many questions remain as yet unanswered. In particular, what are the optimal combinations of techniques/medications to employ to maximize analgesia and minimize secondary effects of trauma? Can an aggressive multimodal approach intervene effectively in the development of chronic pain states, and if so, for how long? What are the long-term benefits to be derived from making a significant impact on the stress response? Last, but not least, can analgesic interventions be shown to be cost-effective according to current societal pressures to reduce the cost of health care? These and other questions are not easy to answer. Trauma strikes, in a variable fashion, patients of all ages, with all forms of comorbidity, and is treated by a technology that continues to evolve. Previous research related to the effects of analgesic treatments has been hampered by the limitations that arise when isolated groups embark on vast projects with limited numbers of patients available. It is time for investigators at multiple centers to embark on coordinated efforts to address long-term questions related to trauma and the therapeutic efficacy of analgesia.