Postoperative Ketamine Administration Decreases Morphine Consumption in Major Abdominal Surgery: A Prospective, Randomized, Double-Blind, Controlled Study

Ketamine intolerance in patients on enhanced recovery after surgery protocols undergoing colorectal operations

BACKGROUND

Ketamine is used in enhanced recovery after surgery (ERAS) protocols because of its beneficial antihyperalgesic and antitolerance effects. However, adverse effects such as hallucinations, sedation, and diplopia could limit ketamine's utility. The main objective of this study was to identify rates of ketamine side effects in postoperative patients after colorectal surgery and, secondarily, to compare short-term outcomes between patients receiving ketamine analgesia and controls.

METHODS

This was a retrospective observational cohort study. Subjects were adults who underwent ERAS protocol-guided colorectal surgery at a large, integrated health system. Patients were grouped into ketamine-receiving and preketamine cohorts. Patients receiving ketamine were divided into tolerant and intolerant groups. Propensity score-adjusted models tested multivariate associations of ketamine tolerance/intolerance vs control group.

RESULTS

A total of 732 patients underwent colorectal surgery within the ERAS program before ketamine's introduction (control). After ketamine's introduction, 467 patients received the medication. Intolerance was seen in 29% of ketamine recipients, and the most common side effect was diplopia. Demographics and surgical variables did not differ between cohorts. Multivariate models revealed no significant differences in hospital stays. Pain scores in the first 24 hours after surgery were slightly higher in patients receiving ketamine. Opiate consumption after surgery was lower for both ketamine tolerant and ketamine intolerant cohorts than for controls.

CONCLUSION

Rates of ketamine intolerance are high, which can limit its use and potential effectiveness. Ketamine analgesia significantly reduced opiate consumption without increasing hospital stays after colorectal surgery, regardless of whether it was tolerated.

Optimizing the use of ketamine to reduce chronic postsurgical pain in women undergoing mastectomy for oncologic indication: study protocol for the KALPAS multicenter randomized controlled trial

BACKGROUND

Mastectomies are commonly performed and strongly associated with chronic postsurgical pain (CPSP), more specifically termed postmastectomy pain syndrome (PMPS), with 25-60% of patients reporting pain 3 months after surgery. PMPS interferes with function, recovery, and compliance with adjuvant therapy. Importantly, it is associated with chronic opioid use, as a recent study showed that 1 in 10 patients continue to use opioids at least 3 months after curative surgery. The majority of PMPS patients are women, and, over the past 10 years, women have outpaced men in the rate of growth in opioid dependence. Standard perioperative multimodal analgesia is only modestly effective in prevention of CPSP. Thus, interventions to reduce CPSP and PMPS are urgently needed. Ketamine is well known to improve pain and reduce opioid use in the acute postoperative period. Additionally, ketamine has been shown to control mood in studies of anxiety and depression. By targeting acute pain and improving mood in the perioperative period, ketamine may be able to prevent the development of CPSP.

METHODS

Ketamine analgesia for long-lasting pain relief after surgery (KALPAS) is a phase 3, multicenter, randomized, placebo-controlled, double-blind trial to study the effectiveness of ketamine in reducing PMPS. The study compares continuous perioperative ketamine infusion vs single-dose ketamine in the postanesthesia care unit vs placebo for reducing PMPS. Participants are followed for 1 year after surgery. The primary outcome is pain at the surgical site at 3 months after the index surgery as assessed with the Brief Pain Inventory-short form pain severity subscale.

DISCUSSION

This project is part of the NIH Helping to End Addiction Long-term (HEAL) Initiative, a nationwide effort to address the opioid public health crisis. This study can substantially impact perioperative pain management and can contribute significantly to combatting the opioid epidemic.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05037123. Registered on September 8, 2021.

Review of the Current Situation of Postoperative Pain and Causes of Inadequate Pain Management in Africa

Postoperative pain is one of the most prevalent complications following surgery, and more than 47% of surgical patients endure postoperative discomfort worldwide. In Africa, due to resource shortages and other issues, postoperative pain is substantially more common when compared to developed countries. Severe postoperative pain has many negative effects, including possibly death, which can burden both individuals and society as a whole. Therefore, effectively controlling postoperative pain is becoming increasingly important. To enhance the effectiveness of future pain management, a thorough analysis of the current reasons for inadequate postoperative pain management is necessary. In this article, the present situations of occurring postoperative pain, children's postoperative pain, and pain management in Africa are reviewed, based on relevant and recent literature. In particular, the reasons for inadequate postoperative pain management in Africa are detailed in this article from five perspectives: the inadequate assessment of postoperative pain, the knowledge gap among medical professionals, the patients' misconceptions, the scarcity of resources, and the lack of medications. Additionally, we offer appropriate solutions following various factors.

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.

Effect of magnesium sulfate with ketamine infusions on intraoperative and postoperative analgesia in cancer breast surgeries: a randomized double-blind trial

BACKGROUND

Opioids are the cornerstone in managing postoperative pain; however, they have many side effects. Ketamine and Magnesium (Mg) are NMDA receptor antagonists used as adjuvant analgesics to decrease postoperative opioid consumption.

OBJECTIVE

We assumed that adding Mg to ketamine infusion can improve the intraoperative and postoperative analgesic efficacy of ketamine infusion alone in cancer breast surgeries.

METHODS

Ninety patients aged between 18 and 65 years and undergoing elective cancer breast surgery were included in this prospective randomized, double-blind study. Group K received ketamine 0.5.ßmg.kg^...1 bolus then 0.12.ßmg.kg^...1.h^...1 infusion for the first 24.ßhours postoperatively. Group KM: received ketamine 0.5.ßmg.kg^...1 and Mg sulfate 50.ßmg.kg^...1, then ketamine 0.12.ßmg.kg^...1.h^...1 and Mg sulfate 8.ßmg.kg^...1.h^...1 infusions for the first 24.ßhours postoperative. The primary outcome was the morphine consumption in the first 24.ßhours postoperative, while the secondary outcomes were: intraoperative fentanyl consumption, NRS, side effects, and chronic postoperative pain.

RESULTS

Group KM had less postoperative opioid consumption (14.12.ß...ß5.11.ßmg) than Group K (19.43.ß...ß6.8.ßmg). Also, Group KM had less intraoperative fentanyl consumption. Both groups were similar in postoperative NRS scores, the incidence of side effects related to opioids, and chronic neuropathic pain.

CONCLUSION

Adding Mg to ketamine infusion can safely improve intraoperative and postoperative analgesia with opioid-sparing effect in cancer breast surgery.

Single-Dose of Postoperative Ketamine for Postoperative Pain After Mastectomy: A Pilot Randomized Controlled Trial

Background and Objectives

Perioperative ketamine has been shown to reduce opioid consumption and pain after surgery. Ketamine is most often given as an infusion, but an alternative is single-dose ketamine. Single-dose ketamine at up to 1 mg/kg has been shown to reduce symptoms of depression, and a wide range of dosages has been used for pain in the emergency department. However, limited data exists on the tolerability and efficacy of a single-dose of ketamine at 0.6 mg/kg for pain when administered immediately after surgery. We conducted a pilot study of single-dose ketamine in patients undergoing mastectomy with reconstruction, hypothesizing that a single-dose of ketamine is well tolerated and can relieve postoperative pain and improve mood and recovery.

Methods

This is a randomized, single-blind, placebo-controlled, two-arm parallel, single-center study. Thirty adult women undergoing mastectomy with reconstruction for oncologic indication received a single-dose of ketamine (0.6mg/kg) or placebo after surgery in the post-anesthesia care unit (PACU). Patients were followed through postoperative day (POD) 7. The primary outcome was postoperative pain measured by the Brief Pain Inventory (BPI) pain subscale on POD 1 and 2. Secondary outcomes include effects on opioid use, PROMIS fatigue and sleep, mood, Quality of Recovery-15, and the Breast Cancer Pain Questionnaire.

Results

Side effects were minor and not significantly different in frequency between groups. The ketamine group reported lower scores on the BPI pain severity subscale, especially at POD 7; however, the difference was not statistically significant. There were no statistically significant differences between ketamine and placebo groups for the secondary outcomes.

Conclusion

A single-dose of ketamine at 0.6mg/kg administered postoperatively in the PACU is well tolerated in women undergoing mastectomy and may confer better pain control up to one week after surgery. Future studies with larger sample sizes are necessary to adequately characterize the effect of postoperative single-dose ketamine on pain control in this population.

Opioid-Sparing Analgesia Impacts the Perioperative Anesthetic Management in Major Abdominal Surgery

Background and Objectives: The management of acute postoperative pain (APP) following major abdominal surgery implies various analgetic strategies. Opioids lie at the core of every analgesia protocol, despite their side effect profile. To limit patients’ exposure to opioids, considerable effort has been made to define new opioid-sparing anesthesia techniques relying on multimodal analgesia. Our study aims to investigate the role of adjuvant multimodal analgesic agents, such as ketamine, lidocaine, and epidural analgesia in perioperative pain control, the incidence of postoperative cognitive dysfunction (POCD), and the incidence of postoperative nausea and vomiting (PONV) after major abdominal surgery. Materials and Methods: This is a clinical, observational, randomized, monocentric study, in which 80 patients were enrolled and divided into three groups: Standard group, C (n = 32), where patients received perioperative opioids combined with a fixed regimen of metamizole/acetaminophen for pain control; co-analgetic group, Co-A (n = 26), where, in addition to standard therapy, patients received perioperative systemic ketamine and lidocaine; and the epidural group, EA (n = 22), which included patients that received standard perioperative analgetic therapy combined with epidural analgesia. We considered the primary outcome, the postoperative pain intensity, assessed by the visual analogue scale (VAS) at 1 h, 6 h, and 12 h postoperatively. The secondary outcomes were the total intraoperative fentanyl dose, total postoperative morphine dose, maximal intraoperative sevoflurane concentration, confusion assessment method for intensive care units score (CAM-ICU) at 1 h, 6 h, and 12 h postoperatively, and the postoperative dose of ondansetron as a marker for postoperative nausea and vomiting (PONV) severity. Results: We observed a significant decrease in VAS score, as the primary outcome, for both multimodal analgesic regimens, as compared to the control. Moreover, the intraoperative fentanyl and postoperative morphine doses were, consequently, reduced. The maximal sevoflurane concentration and POCD were reduced by EA. No differences were observed between groups concerning PONV severity. Conclusions: Multimodal analgesia concepts should be individualized based on the patient’s needs and consent. Efforts should be made to develop strategies that can aid in the reduction of opioid use in a perioperative setting and improve the standard of care.

Opioid-Sparing Perioperative Analgesia Within Enhanced Recovery Programs

Opioid-based analgesia in the perioperative period can provide excellent pain control, but this approach exposes the patient to avoidable side effects and possible harm. Optimal analgesia, an approach that targets the fastest functional recovery with adequate pain control while minimizing side effects, can be achieved with opioid minimization. Many different options for nonopioid multimodal analgesia exist and have been shown to be efficacious, with certain modalities being more beneficial for specific surgeries. This review will present the evidence and practical tips for these management strategies.

Pain, negative affective states and opioid-based analgesics: Safer pain therapies to dampen addiction

Across centuries and civilizations opioids have been used to relieve pain. In our modern societies, opioid-based analgesics remain one of the most efficient treatments for acute pain. However, the long-term use of opioids can lead to the development of analgesic tolerance, opioid-induced hyperalgesia, opioid use disorders, and overdose, which can ultimately produce respiratory depressant effects with fatal consequences. In addition to the nociceptive sensory component of pain, negative affective states arising from persistent pain represent a risk factor for developing an opioid use disorder. Several studies have indicated that the increase in prescribed opioid analgesics since the 1990s represents the root of our current opioid epidemic. In this review, we will present our current knowledge on the endogenous opioid system within the pain neuroaxis and the plastic changes occurring in this system that may underlie the occurrence of pain-induced negative affect leading to misuse and abuse of opioid medications. Dissecting the allostatic neuronal changes occurring during pain is the most promising avenue to uncover novel targets for the development of safer pain medications. We will discuss this along with current and potential approaches to treat pain-induced negative affective states that lead to drug misuse. Moreover, this chapter will provide a discussion on potential avenues to reduce the abuse potential of new analgesic drugs and highlight a basis for future research and drug development based on recent advances in this field.

Impact of Intraoperative Ketamine on Postoperative Analgesic Requirement Following Bariatric Surgery: a Meta-analysis of Randomized Controlled Trials

This meta-analysis aimed at exploring the impact of intravenous ketamine on pain relief and analgesic consumption in patients undergoing bariatric surgery (BS). Literature searches identified nine eligible trials with 458 participants. Forest plot revealed a significantly lower pain score [mean difference (MD) =  - 1.06, p = 0.005; 390 patients) and morphine consumption (MD =  - 3.85 mg, p = 0.01; 212 patients) immediately after BS in patients with intravenous ketamine than in those without. In contrast, pooled analysis showed comparable pain score (p = 0.28), morphine consumption (p = 0.45) within 24 h, and risk of postoperative nausea/vomiting (p = 0.67) between the two groups. In conclusion, the meta-analysis demonstrated improvements in pain outcomes immediately after surgery through perioperative intravenous ketamine administration despite the absence of analgesic benefit in the late postoperative period and a positive impact on postoperative nausea/vomiting.

Ketamine for Acute Pain Management and Sedation

TOPIC

Ketamine is beneficial in clinical settings ranging from procedural sedation to the treatment of chronic pain. This article describes the clinical benefits of ketamine for treatment of acute pain and for sedation of patients undergoing mechanical ventilation.

CLINICAL RELEVANCE

Ketamine causes analgesic and amnestic effects by noncompetitive inhibition of the N-methyl-D-aspartate receptor and activation of the opioid μ and κ receptors. Unlike other sedatives, ketamine provides analgesia and amnesia without causing hypotension or respiratory depression. Several studies have elucidated the clinical benefits of ketamine. The use of ketamine has extended beyond critical care areas such as the operating room and intensive care units. Nurses must be familiar with optimal clinical scenarios, monitoring parameters, and contraindications of ketamine.

PURPOSE

To highlight the clinical utility and pharmacological properties of ketamine through a literature review. Current studies of ketamine in acute pain and sedation management are summarized.

CONTENT COVERED

This narrative review describes pharmacological properties, dosing strategies, adminis-tration considerations, and adverse effects of ketamine.

Does central sensitization affect hyperalgesia after staged bilateral total knee arthroplasty? A randomized controlled trial

Objective

Osteoarthritis (OA) patients who undergo staged bilateral total knee arthroplasty (TKA) feel postoperative hyperalgesia in the second operated knee compared with the first knee. Ketamine is an important drug for central temporal summation and inhibition of secondary mechanical hyperalgesia. This study investigated whether central sensitization has a significant effect on hyperalgesia after consecutive operations.

Methods

Seventy-one of 80 OA patients were randomly allocated to the ketamine or saline group. A bolus of ketamine (group K) or saline (group C) (0.5 mg/kg) was injected before induction and at an infusion rate of 3 µg/kg/minute during surgery. A visual analog scale (VAS) was used to assess resting and moving pain and opioid consumption on postoperative days 1, 2, and 3.

Results

The difference in the VAS score between stages 1 and 2 (D_V2-V1) was higher in the ketamine compared with the saline group. D_V2-V1 for movement between the two groups was not inferior for all periods. Ketamine did not show a large analgesic effect on second-operated knee hyperalgesia in staged bilateral TKAs.

Conclusions

We could not confirm that hyperalgesia was only related to central sensitization with low-dose ketamine. Other factors might be also associated with the hyperexcitability of nociceptive stimuli.

Clinical Research Information Service (CRIS) trial registry no: KCT0001481

Continuous Infusion Ketamine for Adjunctive Analgosedation in Mechanically Ventilated, Critically Ill Patients

OBJECTIVE

Ketamine is an N-methyl-D-aspartate antagonist with emerging evidence assessing its use as a continuous infusion agent to provide concomitant analgesia and sedation. The role of ketamine as adjunctive therapy in mechanically ventilated patients is unclear. This study sought to investigate the impact of adjunctive continuous infusion ketamine on concomitant analgesic and sedative dosing while providing goal comfort in mechanically ventilated patients.

METHODS

This retrospective two-center intrapatient comparison study included mechanically ventilated adult ICU patients who received continuous infusion ketamine with at least one other analgesic or sedative infusion. The primary outcome assessed percent relative change in concomitant analgesic-sedative doses 24 hours after ketamine initiation. Secondary outcomes included percent of Richmond Agitation and Sedation Score (RASS) assessments at goal, adverse effects, and delirium incidence. Exploratory evaluation of independent factors associated with ketamine responders (50% or more relative reduction in analgesic-sedative dosing requirements at 24 hrs) and nonresponders (less than 50% relative reduction) was performed using multivariate logistic regression.

RESULTS

Overall, 104 patients were included. A total of 160 concomitant analgesic-sedative infusions were used in combination with ketamine, most commonly fentanyl (98 [61.3%]) and propofol (46 [28.8%]). A 20% (interquartile range [IQR] -63.6 to 0.0, p<0.001) relative reduction in total analgesic-sedative infusion pharmacotherapy was achieved at 24 hours after ketamine initiation. Analgesic and sedative infusion doses decreased at 24 hours (fentanyl: pre, 175 μg/hr [IQR 100-200 μg/hr] vs post, 125 μg/hr [IQR 50-200 μg/hr], p<0.001; propofol: pre, 42.5 μg/kg/min [IQR 20.0-60.0 μg/kg/min] vs post, 20.0 μg/kg/min [IQR 3.8-31.3 μg/kg/min], p<0.001). Median percent time within goal RASS improved after ketamine initiation (pre, 7.1% [0-40%] vs post, 25% [0-66.7%], p=0.005). No differences were observed in secondary outcomes between responders and nonresponders, except a longer non-ICU hospital length of stay in responders. Independent factors associated with ketamine response included a lower body mass index, higher starting dose of ketamine, lower severity of illness, and need for multiple concomitant analgesic-sedative infusions before initiation of ketamine.

CONCLUSIONS

Adjunctive continuous infusion ketamine promotes analgesic and sedative dose-sparing effects in mechanically ventilated patients while improving time spent within goal sedation range. Further prospective research is warranted.

Ketamine Infusion in Post-Surgical Pain Management after Head and Neck Surgery: A Retrospective Observational Study

Background:

Head and neck cancer affects approximately 382,000 new patients per year worldwide with a significant portion undergoing surgical treatment. During postoperative period key elements in the Intensive Care Unit (ICU) are airway management and pain control.

Objective:

We evaluated the average change of inpatient pain control using a Numerical Rating Score (NRS). We also evaluated the time of extubation after ICU admission recording the incidence of desaturation and the necessity of re-intubation. Secondary outcomes were the incidence of postoperative complications, included those narcotics-related, and the use of rescue analgesics.

Methods:

In this retrospective observational study, we analyzed data of registry before and after we have changed our postoperative analgesic protocol from remifentanil infusion to ketamine infusion.

Results:

Medical records of 20 patients were examined. 10 patients received 0.5 mg/kg ketamine bolus at the end of surgery, followed by a continuous infusion of 0.25 mg/kg/h. All patients presented a significant decrease in pain intensity from the 4th to 48th postoperative hour (p < 0.05), but statically not a significant difference in NRS score was recorded between the two groups. Time to extubation was shorter in ketamine group compared to the remifentanil group (112.30 min ± 16.78 vs. 78 min ± 14.17; p < 0.05). Desaturation rate was 10% in the remifentanil group, while no case was recorded in the ketamine group.

Conclusion:

The level of analgesia provided by ketamine and remifentanil was comparable. Ketamine was superior in ventilatory management of the patient with more rapid extubation and with no case of desaturation.

Critical Care Pain Management in Patients Affected by the Opioid Epidemic: A Review

The rapid rise in the opioid epidemic has had a deleterious impact across the United States. This increase has drawn the attention of the critical care community not only because of the surge in acute opioid overdose-related admissions, but also due to the increase in the number of opioid-dependent and opioid-tolerant patients being treated in the intensive care unit (ICU). Opioid-related issues relevant to the critical care physician include direct care of patients with opioid overdoses, the provision of sufficient analgesia to patients with opioid dependence and tolerance, and the task of preventing long-term opioid dependence in patients who survive ICU care. This review identifies the challenges facing the ICU physician working with patients presenting with opioid-related complications, discusses current solutions, and suggests future areas of research and heightened ICU clinician attention.

An Update on the Basic and Clinical Science of Ketamine Analgesia

OBJECTIVE

In the context of the current opioid epidemic, there has been a renewed interest in the use of ketamine as an analgesic agent.

METHODS

We reviewed ketamine analgesia.

RESULTS

Ketamine is well-known as an antagonist for N-methyl-D-aspartate receptors. In addition, it can regulate the function of opioid receptors and sodium channels. Ketamine also increases signaling through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. These myriad of molecular and cellular mechanisms are responsible for a number of pharmacological functions including pain relief and mood regulation. Clinically, a number of studies have investigated the role of ketamine in the setting of acute and chronic pain, and there is evidence that ketamine can provide analgesia in a variety of pain syndromes.

DISCUSSION

In this review, we examined basic mechanisms of ketamine and its current clinical use and potential novel use in pain management.

Does Sub-Anesthetic Ketamine Provide Postoperative Analgesia for Third Molar Surgery?

PURPOSE

Despite ketamine's effectiveness as an anesthetic and its known analgesic properties, the role of ketamine in postoperative pain after third molar surgery remains unclear. Therefore, this study aimed to investigate whether patients undergoing third molar surgery who received a sub-anesthetic preoperative dose of intravenous ketamine would experience less postoperative pain.

MATERIALS AND METHODS

We implemented a randomized, double-blinded, placebo-controlled trial. The study sample consisted of participants undergoing third molar surgery with procedural sedation anesthesia. Participants were randomized to receive a preoperative intravenous dose of ketamine or placebo, as predictor variables. The primary outcome variable was postoperative pain intensity determined by a 10-point visual analog scale at 6-hour intervals over a period of 48 hours. The secondary outcome variable was the quantity of postoperative non-opioid and opioid consumption. Other variables included the extent and difficulty of surgery performed, patient satisfaction, gender, and age. Data analysis involved descriptive statistics, multivariate analysis, and regression analysis. The P value was set at .05.

RESULTS

A total of 134 participants were randomly enrolled into either the ketamine group (n = 74, 55.2%) or placebo group (n = 60, 44.8%). No statistically significant differences in the distribution of study variables were found between the groups. A small yet statistically significant (P < .05) difference was noted in the median pain score at 6 hours postoperatively, with the ketamine group experiencing more pain. However, no further differences were detected at any postoperative time between the 2 groups. Similar results were obtained after adjusting for age, gender, and surgical difficulty. No difference in the amount of postoperative non-opioid or opioid medication use was found between the 2 groups.

CONCLUSIONS

This study did not find evidence that a preoperative sub-anesthetic dose of ketamine could reduce pain after third molar surgery or have any effects on non-opioid or opioid analgesic consumption. Nevertheless, ketamine remains a valuable option among sedation medications for oral and maxillofacial surgeons.

Perspectives on adjunctive use of ketamine for analgosedation during extracorporeal membrane oxygenation

Analgosedation on ECMO is more than the choice of any drug, it has to be context specific. Ketamine may be considered as an adjunctive therapy in patients requiring high-dose opioids and sedatives during ECMO support with difficulty to achieve a target RASS. Considering ketamine provides analgesia while maintaining airway reflexes, it could be useful for early ECMO weaning and use of ECMO in awake, non-intubated, spontaneously breathing patients with respiratory failure ('awake' ECMO), especially for patients having considerable waiting periods while being bridged to transplant. The hemodynamic effects of ketamine may provide the benefit of decreasing vasopressor requirements, thereby potentially improving microcirculation. In this context, the effects on end-organ function and the need for renal replacement therapy should be investigated. Pharmacokinetic and pharmacodynamic studies on ketamine ex- and in vivo are of utmost importance to delineate its pharmacological profile and effectiveness during ECMO therapy and to create admissible future study hypothesis.

Pain Management in Enhanced Recovery after Surgery (ERAS) Protocols

Pain control is an integral part of Enhanced Recovery after Surgery (ERAS) protocols for colorectal surgery. While opioid therapy remains the mainstay of therapy for postsurgical pain, opioids have undesired side effects including delayed recovery of bowel function, respiratory depression, and postoperative nausea and vomiting. A variety of nonopioid systemic medical therapies as well as regional and neuraxial techniques have been described as improving pain control while reducing opioid use. Multimodal and preemptive analgesia as part of an ERAS protocol facilitates early mobility and early return of bowel function and decreases postoperative morbidity. In this review, we examine several multimodal therapies and their impact on postoperative analgesia, opioid use, and recovery for patients undergoing colorectal surgery.

Perioperative intravenous ketamine for acute postoperative pain in adults

BACKGROUND

Inadequate pain management after surgery increases the risk of postoperative complications and may predispose for chronic postsurgical pain. Perioperative ketamine may enhance conventional analgesics in the acute postoperative setting.

OBJECTIVES

To evaluate the efficacy and safety of perioperative intravenous ketamine in adult patients when used for the treatment or prevention of acute pain following general anaesthesia.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase to July 2018 and three trials registers (metaRegister of controlled trials, ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP)) together with reference checking, citation searching and contact with study authors to identify additional studies.

SELECTION CRITERIA

We sought randomised, double-blind, controlled trials of adults undergoing surgery under general anaesthesia and being treated with perioperative intravenous ketamine. Studies compared ketamine with placebo, or compared ketamine plus a basic analgesic, such as morphine or non-steroidal anti-inflammatory drug (NSAID), with a basic analgesic alone.

DATA COLLECTION AND ANALYSIS

Two review authors searched for studies, extracted efficacy and adverse event data, examined issues of study quality and potential bias, and performed analyses. Primary outcomes were opioid consumption and pain intensity at rest and during movement at 24 and 48 hours postoperatively. Secondary outcomes were time to first analgesic request, assessment of postoperative hyperalgesia, central nervous system (CNS) adverse effects, and postoperative nausea and vomiting. We assessed the evidence using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

We included 130 studies with 8341 participants. Ketamine was given to 4588 participants and 3753 participants served as controls. Types of surgery included ear, nose or throat surgery, wisdom tooth extraction, thoracotomy, lumbar fusion surgery, microdiscectomy, hip joint replacement surgery, knee joint replacement surgery, anterior cruciate ligament repair, knee arthroscopy, mastectomy, haemorrhoidectomy, abdominal surgery, radical prostatectomy, thyroid surgery, elective caesarean section, and laparoscopic surgery. Racemic ketamine bolus doses were predominantly 0.25 mg to 1 mg, and infusions 2 to 5 µg/kg/minute; 10 studies used only S-ketamine and one only R-ketamine. Risk of bias was generally low or uncertain, except for study size; most had fewer than 50 participants per treatment arm, resulting in high heterogeneity, as expected, for most analyses. We did not stratify the main analysis by type of surgery or any other factor, such as dose or timing of ketamine administration, and used a non-stratified analysis.Perioperative intravenous ketamine reduced postoperative opioid consumption over 24 hours by 8 mg morphine equivalents (95% CI 6 to 9; 19% from 42 mg consumed by participants given placebo, moderate-quality evidence; 65 studies, 4004 participants). Over 48 hours, opioid consumption was 13 mg lower (95% CI 10 to 15; 19% from 67 mg with placebo, moderate-quality evidence; 37 studies, 2449 participants).Perioperative intravenous ketamine reduced pain at rest at 24 hours by 5/100 mm on a visual analogue scale (95% CI 4 to 7; 19% lower from 26/100 mm with placebo, high-quality evidence; 82 studies, 5004 participants), and at 48 hours by 5/100 mm (95% CI 3 to 7; 22% lower from 23/100 mm, high-quality evidence; 49 studies, 2962 participants). Pain during movement was reduced at 24 hours (6/100 mm, 14% lower from 42/100 mm, moderate-quality evidence; 29 studies, 1806 participants), and 48 hours (6/100 mm, 16% lower from 37 mm, low-quality evidence; 23 studies, 1353 participants).Results for primary outcomes were consistent when analysed by pain at rest or on movement, operation type, and timing of administration, or sensitivity to study size and pain intensity. No analysis by dose was possible. There was no difference when nitrous oxide was used. We downgraded the quality of the evidence once if numbers of participants were large but small-study effects were present, or twice if numbers were small and small-study effects likely but testing not possible.Ketamine increased the time for the first postoperative analgesic request by 54 minutes (95% CI 37 to 71 minutes), from a mean of 39 minutes with placebo (moderate-quality evidence; 31 studies, 1678 participants). Ketamine reduced the area of postoperative hyperalgesia by 7 cm² (95% CI -11.9 to -2.2), compared with placebo (very low-quality evidence; 7 studies 333 participants). We downgraded the quality of evidence because of small-study effects or because the number of participants was below 400.CNS adverse events occurred in 52 studies, while 53 studies reported of absence of CNS adverse events. Overall, 187/3614 (5%) participants receiving ketamine and 122/2924 (4%) receiving control treatment experienced an adverse event (RR 1.2, 95% CI 0.95 to 1.4; high-quality evidence; 105 studies, 6538 participants). Ketamine reduced postoperative nausea and vomiting from 27% with placebo to 23% with ketamine (RR 0.88, 95% CI 0.81 to 0.96; the number needed to treat to prevent one episode of postoperative nausea and vomiting with perioperative intravenous ketamine administration was 24 (95% CI 16 to 54; high-quality evidence; 95 studies, 5965 participants).

AUTHORS' CONCLUSIONS

Perioperative intravenous ketamine probably reduces postoperative analgesic consumption and pain intensity. Results were consistent in different operation types or timing of ketamine administration, with larger and smaller studies, and by higher and lower pain intensity. CNS adverse events were little different with ketamine or control. Perioperative intravenous ketamine probably reduces postoperative nausea and vomiting by a small extent, of arguable clinical relevance.

Donor Hepatectomy Surgery using Ketamine to Compliment Analgesia and Reduce Morbidity - a Retrospective Chart Review Investigation

Objective

Inferior and limited analgesic options/techniques during living donor hepatectomy surgery can result in pain and risks of morbidity, opioid-related adverse events (AEs), predisposition to the development of chronic pain and concerns of potential narcotic abuse. Traditional analgesia uses unimodal intravenous opioids that can cause significant side effects. Ketamine provides analgesia and may be opioid sparing, but use in living-donor hepatectomy has not been studied.

Methods

Following human investigation committee approval and informed written consent, 47 liver donor patients over a 5-year period scheduled for surgery were categorized into one of three groups: 24 patients received no ketamine (Group 1), 9 received only intraoperative ketamine (Group 2) and 14 patients received intraoperative plus postoperative ketamine (Group 3). Subjects had access to opioid patient-controlled analgesia (PCA). Chart reviews (including operating room and intensive care unit) were collected and analysed for morphine consumption, pain-intensity scores, opioid-sparing effects, AEs of analgesics and for evidence of ketamine side effects on donor hepatectomy patients.

Results

There were no differences in patient demographics. Living donor hepatectomy patients receiving intraoperative ketamine that was continued postoperatively consumed fewer morphine-equivalents and had lower median pain scores than subjects from the other two groups. Ileus occurred in those not receiving ketamine, pruritus was lowest in Group 3, and there was no evidence or reports of ketamine-associated AEs.

Conclusion

Perioperative ketamine for donor hepatectomy patients could safely provide improved analgesia and be opioid sparing when compared to PCA opioids alone, and there is no evidence of ketamine-related AEs at the dose and delivery methods described here during partial liver donation surgery.

Factors Influencing Quality of Pain Management in a Physician Staffed Helicopter Emergency Medical Service

BACKGROUND

Pain is frequently encountered in the prehospital setting and needs to be treated quickly and sufficiently. However, incidences of insufficient analgesia after prehospital treatment by emergency medical services are reported to be as high as 43%. The purpose of this analysis was to identify modifiable factors in a specific emergency patient cohort that influence the pain suffered by patients when admitted to the hospital.

METHODS

For that purpose, this retrospective observational study included all patients with significant pain treated by a Swiss physician-staffed helicopter emergency service between April and October 2011 with the following characteristics to limit selection bias: Age > 15 years, numerical rating scale (NRS) for pain documented at the scene and at hospital admission, NRS > 3 at the scene, initial Glasgow coma scale > 12, and National Advisory Committee for Aeronautics score < VI. Univariate and multivariable logistic regression analyses were performed to evaluate patient and mission characteristics of helicopter emergency service associated with insufficient pain management.

RESULTS

A total of 778 patients were included in the analysis. Insufficient pain management (NRS > 3 at hospital admission) was identified in 298 patients (38%). Factors associated with insufficient pain management were higher National Advisory Committee for Aeronautics scores, high NRS at the scene, nontrauma patients, no analgesic administration, and treatment by a female physician. In 16% (128 patients), despite ongoing pain, no analgesics were administered. Factors associated with this untreated persisting pain were short time at the scene (below 10 minutes), secondary missions of helicopter emergency service, moderate pain at the scene, and nontrauma patients. Sufficient management of severe pain is significantly better if ketamine is combined with an opioid (65%), compared to a ketamine or opioid monotherapy (46%, P = .007).

CONCLUSIONS

In the studied specific Swiss cohort, nontrauma patients, patients on secondary missions, patients treated only for a short time at the scene before transport, patients who receive no analgesic, and treatment by a female physician may be risk factors for insufficient pain management. Patients suffering pain at the scene (NRS > 3) should receive an analgesic whenever possible. Patients with severe pain at the scene (NRS ≥ 8) may benefit from the combination of ketamine with an opioid. The finding about sex differences concerning analgesic administration is intriguing and possibly worthy of further study.

A Comparison of Multimodal Analgesic Approaches in Institutional Enhanced Recovery After Surgery Protocols for Colorectal Surgery: Pharmacological Agents

INTRODUCTION

Enhanced Recovery After Surgery (ERAS^®) protocols are the cornerstone of improved recovery after colorectal surgery. Their implementation leads to reduced morbidity and shorter hospital stays while attenuating the surgical stress response. Multimodal analgesia is an important part of ERAS protocols. We compared and contrasted protocols from 15 institutions to test our hypothesis that there is a fundamental consensus among them.

MATERIALS AND METHODS

ERAS protocols for open and laparoscopic colorectal surgery were compared from 15 different healthcare facilities. We examined each institution's approach to multimodal analgesia related to the use of oral and intravenous analgesics. Preoperative, intraoperative, and postoperative management was examined.

RESULTS

All but three protocols used preoperative multimodal analgesics, with acetaminophen, celecoxib, and gabapentin being the most common. Intraoperative recommendations included the use of ketamine, lidocaine, magnesium, and ketorolac. Some protocols advocated for the use of opiates, while others aimed to minimize total opioid dose. In the postoperative period, the three most utilized agents were acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), and opioids.

CONCLUSIONS

There were many similarities and some significant differences among ERAS protocols examined. Acetaminophen was the most widely used nonopioid agent and along with NSAIDs offers a benefit with respect to postoperative analgesia, opioid-sparing effects, earlier ambulation, and reduction in postoperative ileus. Gabapentin was widely used as it may reduce opioid consumption within the first 24 hours postoperatively. Lidocaine infusion was recommended if there were contraindications to or failure of epidural anesthesia. Ketamine is frequently recommended due to its analgesic, antihyperalgesic, antiallodynic, and antitolerance properties. Differences in approaches may be due to both institutional- and provider-level factors.

Analgesia and Sedation Requirements in Mechanically Ventilated Trauma Patients With Acute, Preinjury Use of Cocaine and/or Amphetamines

BACKGROUND

The purpose of this study was to determine whether mechanically ventilated trauma patients with a positive urine drug screen (UDS) for cocaine and/or amphetamines have different opioid analgesic and sedative requirements compared with similar patients with a negative drug screen for these stimulants.

METHODS

This retrospective, single-center cohort study at a tertiary care, academic medical and level 1 trauma center in the United States included patients ≥16 years of age who were admitted to an adult intensive care unit with a diagnosis of trauma between 2009 and 2013 with a UDS documented within 24 hours of admission, and were mechanically ventilated for >24 hours. The primary end point was the daily dose of opioid received during mechanical ventilation, expressed as morphine equivalents, for patients presenting with a positive UDS for cocaine and/or amphetamines compared with patients with a negative UDS for these stimulants. Secondary end points included the daily benzodiazepine dose and median infusion rates of propofol and dexmedetomidine received during mechanical ventilation, duration of mechanical ventilation, intensive care unit and hospital length of stay, and in-hospital mortality. Analgesic and sedative goals were similar for the duration of the study period, and both intermittent and continuous infusions of opioids and sedatives were administered to achieve these targets, although a standardized approach was not used. A multivariate logistic regression analysis and a propensity-adjusted model evaluated patient characteristics predictive of a higher median opioid requirement.

RESULTS

A total of 150 patients were included in the final analysis. In a univariate analysis, opioid and sedative requirements were similar for patients presenting with a positive UDS for cocaine and/or amphetamines compared with patients with a negative UDS for these stimulants. In the multivariate regression analysis, increasing age and Abbreviated Injury Scale (head and neck) were associated with decreased daily opioid requirements (odds ratio [OR], .95, 95% confidence interval [CI], .93-.97 and OR, .71, 95% CI, .65-.77, respectively), whereas preinjury stimulant use was not predictive of opioid requirements (OR, .88, 95% CI, .40-1.90). In a propensity score--adjusted model, preinjury stimulant use was similarly not predictive of opioid requirements during mechanical ventilation (OR, .97, 95% CI, .44-2.11).

CONCLUSIONS

For trauma patients presenting with acute, preinjury use of cocaine and/or amphetamines, analgesic and sedative requirements are variables and may not be greater than those patients presenting with a stimulant-negative UDS to achieve desirable pain control and depth of sedation, although this observation should be interpreted cautiously in light of the wide CI observed in the propensity score--adjusted model. Although unexpected, these findings indicate that empirically increasing analgesic and sedative doses based on positive UDS results for these stimulants may not be necessary.

Efficacy of Low-dose Ketamine as Sole Analgesic Agent in Maintaining Analgesia and Intraoperative Hemodynamics During Laparoscopic Gynecological Surgeries

BACKGROUND

Ketamine, in low doses, is known to possess intense analgesic properties. The available literature shows wide variation regarding the time and dose of administration of ketamine during surgery.

AIM

The aim of this study was to evaluate the effect of intraoperative administration of ketamine when used as sole analgesic in low doses, on hemodynamics and postoperative analgesia in patients undergoing laparoscopic gynecological surgery and compared on the basis of duration of surgery.

SETTINGS AND DESIGN

This prospective, observational study was conducted from July to December 2015, over a period of 6 months in a tertiary care medical college and hospital.

MATERIALS AND METHODS

Seventy patients between 23 and 55 years planned for laparoscopic gynecological surgery were recruited. Ketamine was given in a dose of 0.5 mg/kg preoperatively and then repeated every ½ hourly in a dose of 0.25 mg/kg throughout the surgery. Hemodynamic parameters, time to the first rescue analgesia and complications were recorded for the first 8 h. Statistical evaluation was done and result expressed as percentage. Paired t-test was employed for the comparison of numerical variables within the group.

RESULTS

Seventy percent of the patients did not require any postoperative rescue analgesia during the first 8 h after surgery. None of the patients complained of pain immediately after extubation, and 16% of the patients had minor postoperative complications. The intraoperative hemodynamic profile was significantly altered. Duration of surgery and dose of ketamine required did not affect the duration of analgesia.

CONCLUSION

Ketamine in low dose proved to be an efficacious analgesic even in the long duration laparoscopic gynecological surgeries. It stabilizes intraoperative hemodynamics thereby reducing the requirement of other anesthetic and antihypertensive agents.

American Society for Enhanced Recovery (ASER) and Perioperative Quality Initiative (POQI) joint consensus statement on optimal analgesia within an enhanced recovery pathway for colorectal surgery: part 1-from the preoperative period to PACU

Background

Within an enhanced recovery pathway (ERP), the approach to treating pain should be multifaceted and the goal should be to deliver “optimal analgesia,” which we define in this paper as a technique that optimizes patient comfort and facilitates functional recovery with the fewest medication side effects.

Methods

With input from a multi-disciplinary, international group of clinicians, and through a structured review of the literature and use of a modified Delphi method, we achieved consensus surrounding the topic of optimal analgesia in the perioperative period for colorectal surgery patients.

Discussion

As a part of the first Perioperative Quality Improvement (POQI) workgroup meeting, we sought to develop a consensus document describing a comprehensive, yet rational and practical, approach for developing an evidence-based plan for achieving optimal analgesia, specifically for a colorectal surgery ERP. The goal was two-fold: (a) that application of this process would lead to improved patient outcomes and (b) that investigation of the questions raised would identify knowledge gaps to aid the direction for research into analgesia within ERPs in the years to come. This document details the evidence for a wide range of analgesic components, with particular focus from the preoperative period to the post-anesthesia care unit. The overall conclusion is that the combination of analgesic techniques employed in the perioperative period is not important as long as it is effective in delivering the goal of optimal analgesia as set forth in this document.

American Society for Enhanced Recovery (ASER) and Perioperative Quality Initiative (POQI) Joint Consensus Statement on Optimal Analgesia within an Enhanced Recovery Pathway for Colorectal Surgery: Part 2-From PACU to the Transition Home

BACKGROUND

Within an enhanced recovery pathway (ERP), the approach to treating pain should be multifaceted and the goal should be to deliver "optimal analgesia", which we define in this paper as a technique that optimizes patient comfort and facilitates functional recovery with the fewest medication side effects.

METHODS

With input from a multidisciplinary, international group of experts and through a structured review of the literature and use of a modified Delphi method, we achieved consensus surrounding the topic of optimal analgesia in the perioperative period for colorectal surgery patients.

DISCUSSION

As a part of the first Perioperative Quality Improvement (POQI) workgroup meeting, we sought to develop a consensus document describing a comprehensive, yet rational and practical, approach for developing an evidence-based plan for achieving optimal analgesia, specifically for a colorectal surgery within an ERP. The goal was twofold: (a) that application of this process would lead to improved patient outcomes and (b) that investigation of the questions raised would identify knowledge gaps to aid the direction for research into analgesia within ERPs in the years to come. This document details the evidence for a wide range of analgesic components, with particular focus on care in the post-anesthesia care unit, general care ward, and transition to home after discharge. The preoperative and operative consensus statement for analgesia was covered in Part 1 of this paper. The overall conclusion is that the combination of analgesic techniques employed in the perioperative period is not important as long as it is effective in delivering the goal of "optimal analgesia" as set forth in this document.

Ketamine-A Narrative Review of Its Uses in Medicine

One of the most fascinating drugs in the anesthesiologist's armament is ketamine, an N-methyl-D-aspartate receptor antagonist with a myriad of uses. The drug is a dissociative anesthetic and has been used more often as an analgesic in numerous hospital units, outpatient pain clinics, and in the prehospital realm. It has been used to treat postoperative pain, chronic pain, complex regional pain syndrome, phantom limb pain, and other neuropathic conditions requiring analgesia. Research has also demonstrated its efficacy as an adjunct in psychotherapy, as a treatment for both depression and posttraumatic stress disorder, as a procedural sedative, and as a treatment for respiratory and neurologic conditions. Ketamine is not without its adverse effects, some of which can be mitigated with certain efforts. Such effects make it necessary for the clinician to use the drug only in situations where it will provide the greatest benefit with the fewest adverse effects. To the best of our knowledge, none of the reviews regarding ketamine have taken a comprehensive look at the drug's uses in all territories of medicine. This review will serve to touch on its chemical data, pharmacokinetics and pharmacodynamics, medical uses, and adverse effects while focusing specifically on the drugs usage in anesthesia and analgesia.

Assessment of low-dose i.v. ketamine infusions for adjunctive analgesia

PURPOSE

The results of a study evaluating all patients treated with adjunctive low-dose ketamine for analgesia over a three-year period are presented.

METHODS

A retrospective single-center analysis evaluated all adult patients who received adjunctive low-dose i.v. ketamine infusions from September 2010 to September 2013. Patients were excluded if they received concomitant oral ketamine, if ketamine was used to treat seizures, or if the patients received ketamine boluses without infusion. The primary endpoint was to identify the patient populations receiving low-dose intravenous ketamine. Secondary endpoints included an assessment of clinical variables and adverse events. Demographic information, level of care, clinical variables, adverse events, and patient outcomes were recorded.

RESULTS

A total of 460 patients were evaluated. Of these, 396 were included in this analysis. Ketamine was administered to 69.9% of the patients in association with a surgical procedure, as opposed to 30.1% who received ketamine for medical management of pain. The percentage of patients receiving intensive care unit level care was 24%. Before initiation of ketamine, patient-reported pain scores averaged 7.1 ± 2.63 S.D.; during the ketamine infusion, patient-reported pain scores averaged 6.42 ± 2.01 S.D.; (p < 0.001). In the safety analysis, hypertension occurred in 21.4% of patients, hypotension occurred in 15.1% of patients, and respiratory depression occurred in 6.3% of patients.

CONCLUSION

A retrospective review found that patients receiving continuous ketamine infusions in addition to opioid therapy saw a reduction in pain scores and experienced cardiovascular adverse effects in greater than 20% of cases.

Ketamine: 50 Years of Modulating the Mind

Ketamine was introduced into clinical practice in the 1960s and continues to be both clinically useful and scientifically fascinating. With considerably diverse molecular targets and neurophysiological properties, ketamine’s effects on the central nervous system remain incompletely understood. Investigators have leveraged the unique characteristics of ketamine to explore the invariant, fundamental mechanisms of anesthetic action. Emerging evidence indicates that ketamine-mediated anesthesia may occur via disruption of corticocortical information transfer in a frontal-to-parietal (“top down”) distribution. This proposed mechanism of general anesthesia has since been demonstrated with anesthetics in other pharmacological classes as well. Ketamine remains invaluable to the fields of anesthesiology and critical care medicine, in large part due to its ability to maintain cardiorespiratory stability while providing effective sedation and analgesia. Furthermore, there may be an emerging role for ketamine in treatment of refractory depression and Post-Traumatic Stress Disorder. In this article, we review the history of ketamine, its pharmacology, putative mechanisms of action and current clinical applications.

Comparison of Small Dose Ketamine and Dexmedetomidine Infusion for Postoperative Analgesia in Spine Surgery--A Prospective Randomized Double-blind Placebo Controlled Study

BACKGROUND

High doses of opioids are frequently used to treat postoperative pain after spine surgery. This leads to opioid-related side effects like nausea, vomiting, respiratory depression, etc. The current study is an attempt to find a safe analgesic adjuvant, which will afford opioid sparing property.

METHOD

Sixty-six patients undergoing spine surgery were randomized into 1 of the 3 groups-group K (ketamine bolus 0.25 mg/kg followed by infusion of 0.25 mg/kg/h with midazolam bolus 10 μg/kg and infusion of 10 μg/kg/h mixed in the same infusion pump), group D (dexmedetomidine bolus 0.5 μg/kg followed by 0.3 μg/kg/h infusion), and group C (normal saline). Study drugs were started in the postoperative period and continued for 24 hours. Pain-free period, pain scores, rescue analgesic (morphine) requirements, and side effects were noted for 48 hours postoperatively.

RESULT

Mean pain-free periods in the ketamine group (860 min) and the dexmedetomidine group (580 min) were longer than in the saline group (265 min) (P<0.002) during the observation period of 48 hours. There was a significant decrease in the rescue analgesic requirement in both ketamine and dexmedetomidine group (P<0.05) (cumulative morphine requirement at 24 h-group C 15.64±9.31 mg, group D 6.89±5.88 mg, group K 2.45±2.06 mg; at 48 h-group C 21.09±12.88 mg, group D 7.98±7.72 mg, group K 2.59±1.97 mg). Hemodynamics were maintained within normal range in all the groups. Patients in ketamine and dexmedetomidine groups were sedated, but none required assistance for maintaining airway patency. Few patients in the ketamine group had nausea, dizziness, and diplopia, but the difference was insignificant in comparison with other groups (P>0.05).

CONCLUSIONS

Infusion of low-dose ketamine and dexmedetomidine both provide good postoperative analgesia with minimal side effects. Both of the tested analgesic regimes can be used safely and effectively for postoperative pain relief in patients after spine surgery.

Comparison of the effects of magnesium and ketamine on postoperative pain and morphine consumption. A double-blind randomized controlled clinical study

PURPOSE

To compare the effects of magnesium sulfate and ketamine on postoperative pain and total morphine consumption in a placebo-controlled design.

METHODS

One hundred and twenty women scheduled for total abdominal hysterectomy were included in this prospective, randomized, double-blind study. Postoperatively, when the Numeric Pain Rating Scale (NPRS) was four or more, IV-PCA morphine was applied to all patients. The patients were randomized into three groups: Group K ketamine, Group M magnesium, and Group C saline received as infusion. Total morphine consumption for 48h, pain scores, adverse effects, and patients' satisfaction were evaluated.

RESULTS

Total morphine consumption was significantly lower in Group K (32.6±9.2 mg) than in Group M (58.9±6.5 mg) and in Group C (65.7±8.2 mg). The satisfaction level of patients in Group K was higher than the other two groups (p<0.05). Pruritus and nausea were observed more frequently in Group C. CONCLUSİON: The addition of ketamine to IV-PCA morphine reduces the total consumption of morphine without psychotic effects; however, magnesium did not influence morphine consumption.

Serum concentration of ketamine and antinociceptive effects of ketamine and ketamine-lidocaine infusions in conscious dogs

Background

Central sensitization is a potential severe consequence of invasive surgical procedures. It results in postoperative and potentially chronic pain enhancement. It results in postoperative pain enhancement; clinically manifested as hyperalgesia and allodynia. N-methyl-D-aspartate (NMDA) receptor plays a crucial role in the mechanism of central sensitisation. Ketamine is most commonly used NMDA-antagonist in human and veterinary practice. However, the antinociceptive serum concentration of ketamine is not yet properly established in dogs. Six dogs were used in a crossover design, with one week washout period. Treatments consisted of: 1) 0.5 mg/kg ketamine followed by continuous rate infusion (CRI) of 30 μg/kg/min; 2) 0.5 mg/kg ketamine followed by CRI of 30 μg/kg/min and lidocaine (2 mg/kg followed by CRI of 100 μg/kg/min); and 3) 0.5 mg/kg ketamine followed by CRI of 50 μg/kg/min. The infusion was administered up to 120 min. Nociceptive thresholds and ketamine serum concentrations were measured before drug administration, and at 5, 10, 20, 40, 60, 90, 120, 140 and 160 min after the start of infusion.

Results

Maximum concentration recorded was 435.34 ± 26.18 ng/mL, 582.34 ± 227.46 ng/mL and 733.77 ± 133.6 ng/mL for K30, KL30 and K50, respectively. The concentration at 120 min was 250.87 ± 39.87, 221.73 ± 91.03 and 343.67 ± 63.21 ng/mL at 120 min in K30, KL30 and K50, respectively. All the three infusion regimes maintained serum concentrations above 200 ng/mL. The thresholds returned towards baseline values within 20 min, after cessation of infusion.

Conclusion

Serum concentration to produce mechanical antinociceptive effects in dogs is between 100 and 200 ng/mL. All the three infusion regimes in this study provided antinociceptive effects throughout the infusions. In this study, we found that the serum concentration of ketamine to produce mechanical antinociceptive effects in dogs is above 200 ng/mL. All three infusion regimes provided antinociceptive effects throughout the infusions without causing harmful effects. Further studies are recommended in a clinical setting.

Perioperative Dextromethorphan as an Adjunct for Postoperative Pain: A Meta-analysis of Randomized Controlled Trials

BACKGROUND

N-methyl-D-aspartate receptor antagonists have been shown to reduce perioperative pain and opioid use. The authors performed a meta-analysis to determine whether the use of perioperative dextromethorphan lowers opioid consumption or pain scores.

METHODS

PubMed, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Pubget, and EMBASE were searched. Studies were included if they were randomized, double-blinded, placebo-controlled trials written in English, and performed on patients 12 yr or older. For comparison of opioid use, included studies tracked total consumption of IV or intramuscular opioids over 24 to 48 h. Pain score comparisons were performed at 1, 4 to 6, and 24 h postoperatively. Difference in means (MD) was used for effect size.

RESULTS

Forty studies were identified and 21 were eligible for one or more comparisons. In 848 patients from 14 trials, opioid consumption favored dextromethorphan (MD, -10.51 mg IV morphine equivalents; 95% CI, -16.48 to -4.53 mg; P = 0.0006). In 884 patients from 13 trials, pain at 1 h favored dextromethorphan (MD, -1.60; 95% CI, -1.89 to -1.31; P < 0.00001). In 950 patients from 13 trials, pain at 4 to 6 h favored dextromethorphan (MD, -0.89; 95% CI, -1.11 to -0.66; P < 0.00001). In 797 patients from 12 trials, pain at 24 h favored dextromethorphan (MD, -0.92; 95% CI, -1.24 to -0.60; P < 0.00001).

CONCLUSION

This meta-analysis suggests that dextromethorphan use perioperatively reduces the postoperative opioid consumption at 24 to 48 h and pain scores at 1, 4 to 6, and 24 h.

Role of ketamine in acute postoperative pain management: a narrative review

OBJECTIVES

The objective of this narrative review was to examine the usage of ketamine as a postoperative analgesic agent across a wide variety of surgeries.

DESIGN

A literature search was performed using the phrases "ketamine" and "postoperative pain." The authors analyzed the studies that involved testing ketamine's effectiveness at controlling postoperative pain. Effectiveness was assessed through various outcomes such as the amount of opiate consumption, visual analog scale (VAS) pain scores, and persistent postoperative pain at long-term follow-up.

RESULTS

While many different administration protocols were evaluated, delivering ketamine both as a pre- or perioperative bolus and postoperative infusion for up to 48 hours appeared to be the most effective. These effects are dose-dependent. However, a number of studies analyzed showed no benefit in using ketamine versus placebo for controlling postoperative pain. While ketamine is a safe and well-tolerated drug, it does have adverse effects, and there are concerns for possible neurotoxicity and effects on memory.

CONCLUSIONS

In a number of limited situations, ketamine has shown some efficacy in controlling postoperative pain and decreasing opioid consumption. More randomized controlled trials are necessary to determine the surgical procedures and administrations (i.e., intravenous, epidural) that ketamine is best suited for.

Perioperative low-dose ketamine improves postoperative analgesia following Cesarean delivery with general anesthesia

OBJECTIVE

In this study, the effect of perioperative uses of low dose ketamine on post-operative wound pain and analgesic consumption in patients undergoing elective Cesarean section was evaluated.

METHODS

In randomized, double blind clinical trial, 52 women with American Society of Anesthesiologists (ASA) class I-II identification undergoing elective Cesarean section in general anesthesia were enrolled. In the ketamine group (group K), a ketamine bolus of 0.5 mg kg(-1) IV was administered at the time of induction of general anesthesia. After induction, a ketamine infusion of 0.25 mg kg(-1) h(-1) was started and discontinued at the end of surgery. Patients allocated to the control group (group C) were given identical volumes of saline. The cumulative dose of morphine consumption after surgery was measured as the primary outcome of this study. Secondary outcomes were pain control assessed by numeric rating scale (NRS) and need for rescue analgesia and incidence of side effects.

RESULTS

The mean 24-h morphine consumption was lower in group K (p = 0,001). At 15 min postoperatively, NRS values were lower in group K than group C (p = 0,001). There was no difference among groups regarding the need for supplemental analgesia (rescue diclofenac doses) (p > 0.05).

CONCLUSIONS

Perioperative uses of low dose ketamine decreased post-operative opioid requirements, which was observed long after the normal expected duration of ketamine.

Effect of intraoperative infusion of low-dose ketamine on management of postoperative analgesia

Background:

Use of opioids for perioperative analgesia is associated with sedation, respiratory depression and postoperative nausea and vomiting. N-methyl-D-aspartate receptor antagonist such as ketamine has both analgesic and antihyperalgesic properties. We studied the effect of intraoperative infusion of low-dose ketamine on postoperative analgesia and its management with opioids.

Materials and Methods:

A total of 80 patients scheduled for open cholecystectomy under general anesthesia were randomly allocated into two equal groups in a randomized double-blinded way. The general anesthetic technique was standardized in both groups. Group K patients (n = 40) received bolus of ketamine 0.2 mg/kg intravenously followed by an infusion of 0.1 mg/kg/h before skin incision, which was continued up to the end of surgery. Similar volume of saline was infused in Group C (n = 40). The pain score at different intervals and cumulative morphine consumption over 24 h was observed. Secondary outcomes such as hemodynamic parameters, patient satisfaction score and incidences of side effects were also recorded.

Results:

Intraoperative infusion of low-dose ketamine resulted in effective analgesia in first 6 h of the postoperative period, which was evident from reduced pain scores and reduced opioid requirements (P = 0.001). The incidence of side effects and patient satisfaction were similar in both groups.

Conclusion:

Intraoperative low-dose ketamine infusion provides good postoperative analgesia while reducing need of opioid analgesics, which must be considered for better management of postoperative analgesia.