Clinical Uses of Low – Dose Ketamine in Patients Undergoing Surgery

Ketamine use in critically ill patients: a narrative review

Ketamine is unique among anesthetics and analgesics. The drug is a rapid-acting general anesthetic that produces an anesthetic state characterized by profound analgesia, preserved pharyngeal-laryngeal reflexes, normal or slightly enhanced skeletal muscle tone, cardiovascular and respiratory stimulation, and occasionally a transient and minimal respiratory depression. Research has demonstrated the efficacy of its use on anesthesia, pain, palliative care, and intensive care. Recently, it has been used for postoperative and chronic pain, as an adjunct in psychotherapy, as a treatment for depression and posttraumatic stress disorder, as a procedural sedative, and as a treatment for respiratory and/or neurologic clinical conditions. Despite being a safe and widely used drug, many physicians, such as intensivists and those practicing in emergency care, are not aware of the current clinical applications of ketamine. The objective of this narrative literature review is to present the theoretical and practical aspects of clinical applications of ketamine in intensive care unit and emergency department settings.

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.

The multiple faces of ketamine in anaesthesia and analgesia

Objective

Ketamine is an anaesthetic agent with a unique dissociative profile and pharmacological effects ranging from the induction and maintenance of anaesthesia to analgesia and sedation, depending on the dose. This article provides information for the clinical use of ketamine in anaesthesia, in both conventional and special circumstances.

Methods

This is a non-systematic review of the literature, through a PubMed search up to February 2021.

Results

With a favourable pharmacokinetic profile, ketamine is used in hospital and prehospital settings for emergency situations. It is suitable for patients with many heart conditions and, unlike other anaesthetics, its potential for cardiorespiratory depression is low. Furthermore, it may be used when venous access is difficult as it may be administered through various routes. Ketamine is the anaesthetic of choice for patients with bronchospasm thanks to its bronchodilatory and anti-inflammatory properties.

Conclusion

With a favourable pharmacokinetic profile, ketamine is used in hospital and prehospital settings for emergency situations and is suitable for patients with many cardiac and respiratory conditions.

Pain Intensity in the First 96 Hours After Abdominal Surgery: A Prospective Cohort Study

OBJECTIVE

Multimodal pain management strategies aim to improve postoperative pain control. The purpose of this study was to analyze pain scores and risk factors for acute postoperative pain after various abdominal surgery procedures.

METHODS

Data on 11 different abdominal surgery procedures were prospectively recorded. Pain intensity (rest, mobilization) and patient satisfaction at discharge were assessed using a visual analog scale (VAS; 0-10), and analgesic consumption was recorded until 96 hours postoperation. Demographic, surgery-related, and pain management-related univariate risk factors for insufficient pain control (VAS ≥ 4) were entered in a multivariate logistic regression model.

RESULTS

A total of 1,278 patients were included. Overall, mean VAS scores were <3 at all time points, and scores at mobilization were consistently higher than at rest (P < 0.05). Thirty percent of patients presented a prolonged VAS score ≥4 at mobilization at 24 hours, significantly higher than at rest (14%, P < 0.05). High pain scores correlated with high opioid consumption, whereas a variability of pain scores was observed in patients with low opioid consumption. The only independent risk factor for moderate and severe pain (VAS ≥ 4) was younger age (<70 years, P = 0.001). The mean satisfaction score was 8.18 ± 1.29.

CONCLUSIONS

Among 1,278 patients, pain was controlled adequately during the first four postoperative days, resulting in high levels of patient satisfaction. Pain levels were higher at mobilization. Younger age was the only independent risk factor for insufficient pain control. Preventive treatment in patients <70 years old and before mobilization could be evaluated for potential improvement.

Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Acute Pain Management From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists

BACKGROUND

Ketamine infusions have been used for decades to treat acute pain, but a recent surge in usage has made the infusions a mainstay of treatment in emergency departments, in the perioperative period in individuals with refractory pain, and in opioid-tolerant patients. The widespread variability in patient selection, treatment parameters, and monitoring indicates a need for the creation of consensus guidelines.

METHODS

The development of acute pain ketamine guidelines grew as a corollary from the genesis of chronic pain ketamine guidelines. The charge for the development of acute pain ketamine guidelines was provided by the Boards of Directors of both the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine, who approved the document along with the American Society of Anesthesiologists' Committees on Pain Medicine and Standards and Practice Parameters. The committee chair developed questions based on input from the committee during conference calls, which the committee then refined. Groups of 3 to 5 panel members and the committee chair were responsible for answering individual questions. After preliminary consensus was achieved, the entire committee made further revisions via e-mail and conference calls.

RESULTS

Consensus guidelines were prepared in the following areas: indications, contraindications for acute pain and whether they differ from those for chronic pain, the evidence for the use of ketamine as an adjunct to opioid-based therapy, the evidence supporting patient-controlled ketamine analgesia, the use of nonparenteral forms of ketamine, and the subanesthetic dosage range and whether the evidence supports those dosages for acute pain. The group was able to reach consensus on the answers to all questions.

CONCLUSIONS

Evidence supports the use of ketamine for acute pain in a variety of contexts, including as a stand-alone treatment, as an adjunct to opioids, and, to a lesser extent, as an intranasal formulation. Contraindications for acute pain are similar to those for chronic pain, partly based on the observation that the dosage ranges are similar. Larger studies evaluating different acute pain conditions are needed to enhance patient selection, determine the effectiveness of nonparenteral ketamine alternatives, define optimal treatment parameters, and develop protocols optimizing safety and access to care.

Ketamine for the treatment of addiction: Evidence and potential mechanisms

Ketamine is a dissociative anaesthetic drug which acts on the central nervous system chiefly through antagonism of the n-methyl-d-aspartate (NMDA) receptor. Recently, ketamine has attracted attention as a rapid-acting anti-depressant but other studies have also reported its efficacy in reducing problematic alcohol and drug use. This review explores the preclinical and clinical research into ketamine's ability to treat addiction. Despite methodological limitations and the relative infancy of the field, results thus far are promising. Ketamine has been shown to effectively prolong abstinence from alcohol and heroin in detoxified alcoholics and heroin dependent individuals, respectively. Moreover, ketamine reduced craving for and self-administration of cocaine in non-treatment seeking cocaine users. However, further randomised controlled trials are urgently needed to confirm ketamine's efficacy. Possible mechanisms by which ketamine may work within addiction include: enhancement of neuroplasticity and neurogenesis, disruption of relevant functional neural networks, treating depressive symptoms, blocking reconsolidation of drug-related memories, provoking mystical experiences and enhancing psychological therapy efficacy. Identifying the mechanisms by which ketamine exerts its therapeutic effects in addiction, from the many possible candidates, is crucial for advancing this treatment and may have broader implications understanding other psychedelic therapies. In conclusion, ketamine shows great promise as a treatment for various addictions, but well-controlled research is urgently needed. This article is part of the Special Issue entitled 'Psychedelics: New Doors, Altered Perceptions'.

A Case Report: Subanesthetic Ketamine Infusion for Treatment of Cancer-Related Pain Produces Urinary Urge Incontinence

Oncology patients undergoing treatment can experience substantial pain related to their disease or prescribed therapy. Ketamine infusions at subanesthetic doses have been used at our institution to supplement the pain management regimens of 262 patients. We present 2 cases in which young adult patients being treated with subanesthetic ketamine for cancer-related pain experienced urinary urgency and incontinence after initiation or increase of the ketamine infusion. This adverse effect has not been reported previously at this dosing range. These case reports suggest that subanesthetic ketamine infusions may cause side effects that previously have been reported only at anesthetic or abuse doses.

Analgesic Effects of Preincision Ketamine on Postspinal Caesarean Delivery in Uganda's Tertiary Hospital: A Randomized Clinical Trial

Background. Good postoperative analgesic management improves maternal satisfaction and care of the neonate. Postoperative pain management is a challenge in Mulago Hospital, yet ketamine is accessible and has proven benefit. We determined ketamine's postoperative analgesic effects. Materials and Methods. We did an RCT among consenting parturients that were randomized to receive either intravenous ketamine (0.25 mg/kg) or placebo after spinal anesthetic. Pain was assessed every 30 mins up to 24 hours postoperatively using the numerical rating scale. The first complaint of pain requiring treatment was noted as “time to first breakthrough pain.” Results. We screened 100 patients and recruited 88 that were randomized into two arms of 44 patients that received either ketamine or placebo. Ketamine group had 30-minute longer time to first breakthrough pain and lower 24-hour pain scores. Postoperative diclofenac consumption was lesser in the ketamine group compared to placebo and Kaplan-Meier graphs showed a higher probability of experiencing breakthrough pain earlier in the placebo group. Conclusion. Preincision intravenous ketamine (0.25 mg/kg) offered 30-minute prolongation to postoperative analgesia requirement with reduced 24-hour pain scores. We recommend larger studies to explore this benefit. This trial is registered with Pan African Clinical Trial Registry number PACTR201404000807178.

Management of acute pancreatitis in dogs: a critical appraisal with focus on feeding and analgesia

Knowledge about acute pancreatitis has increased recently in both the medical and veterinary fields. Despite this expansion of knowledge, there are very few studies on treatment interventions in naturally occurring disease in dogs. As a result, treatment recommendations are largely extrapolated from experimental rodent models or general critical care principles. General treatment principles involve replacing fluid losses, maintaining hydrostatic pressure, controlling nausea and providing pain relief. Specific interventions recently advocated in human medicine include the use of neurokinin-1 antagonists for analgesia and early interventional feeding. The premise for early feeding is to improve the health of the intestinal tract, as unhealthy enterocytes are thought to perpetuate systemic inflammation. The evidence for early interventional feeding is not supported by robust clinical trials to date, but in humans there is evidence that it reduces hospitalisation time and in dogs it is well tolerated. This article summarises the major areas of management of acute pancreatitis in dogs and examines the level of evidence for each recommendation.

Ketamine: Current applications in anesthesia, pain, and critical care

Ketamine was introduced commercially in 1970 with the manufacturer's description as a "rapidly acting, nonbarbiturate general anesthetic" and a suggestion that it would be useful for short procedures. With the help of its old unique pharmacological properties and newly found beneficial clinical properties, ketamine has survived the strong winds of time, and it currently has a wide variety of clinical applications. It's newly found neuroprotective, antiinflammatory and antitumor effects, and the finding of the usefulness of low dose ketamine regimens have helped to widen the clinical application profile of ketamine. The present article attempts to review the current useful applications of ketamine in anesthesia, pain and critical care. It is based on scientific evidence gathered from textbooks, journals, and electronic databases.

A case of above knee amputation with preoperative high risks

An 85-year-old malnourished man was admitted with ischemia-induced necrosis of the right leg and high-risk factors, including chronic obstructive pulmonary disease, pneumonia, and infection of the necrotic leg. We controlled the infection and provided proper nutrition. Using light general anesthesia and a nerve block, we amputated the leg above the knee. The patient could eat and drink the same day following the surgery, and respiratory rehabilitation was begun the next day. His postoperative course was uneventful. Our case suggests that maintenance of good nutrition may play a key role for high-risk elders undergoing leg amputation.

Addition of ketamine to propofol-alfentanil anesthesia may reduce postoperative pain in laparoscopic cholecystectomy

OBJECTIVE

The aim of this study was to assess whether intravenous anesthesia supplemented with ketamine reduces postoperative pain after elective laparoscopic cholecystectomy.

MATERIALS AND METHODS

Forty patients were enrolled and randomized 1:1 into one of 2 groups: the propofol group (received propofol and alfentanil supplemented with saline) and the ketamine group (received propofol and alfentanil with ketamine). The study was double-blind. The number and amount of the intraoperative additional alfentanil doses were recorded. Pain assessments and cumulative analgesic consumption at postanesthesia care unit (PACU) admission, PACU discharge, postoperative 24th hour, and hospital discharge were recorded.

RESULTS

The visual analog scale scores at PACU admission, PACU discharge, postoperative 24th hour, and hospital discharge were significantly lower in the ketamine group than the propofol group. The pain visual analog scale ≥ 75 at the postoperative 24th hour for the propofol group was also significantly lower (P<0.035) than that of the ketamine group. The difference in analgesic consumption between groups was statistically significant (P<0.001).

CONCLUSIONS

Our study showed that ketamine supplemented with propofol and alfentanil produced better analgesia intraoperatively and postoperatively and decreased analgesic consumption compared with the propofol group after laparoscopic cholecystectomy.

Ketamine in pain management

For ketamine's fiftieth birthday, a narrative review of this unique drug in pain management is presented. Its history is traced from its conception, and its heritage, as a phencyclidine offspring, delineated. The earliest roots of the conceptions concerning the mechanisms of action are sought, and then followed in preclinical as well as clinical research. The major proposed mechanisms in the literature are commented on and evaluated. The growth of the clinical evidence for perioperative pain, acute pain, and chronic pain is followed from early attempts to systematic reviews. Finally, an attempt is made to foresee what the next 50 years might hold in store for our 50 years old.

Ketamine decreases postoperative pain scores in patients taking opioids for chronic pain: results of a prospective, randomized, double-blind study

BACKGROUND

Patients prescribed opioids for chronic pain may suffer from inadequate postoperative pain control. Ketamine is an adjuvant demonstrating analgesic and opioid-sparing effects. We hypothesize that an intravenous ketamine infusion in addition to opioid-based patient-controlled analgesia (PCA) improves postoperative pain relief in this patient population.

METHODS

We evaluated 64 patients with chronic pain taking opioids undergoing nononcologic surgery. Patients were randomized to receive either postoperative hydromorphone PCA and continuous ketamine (0.2 mg/kg/hour), or hydromorphone PCA and saline. Patients provided numeric rating scale (NRS) pain scores for "worst," "average," and "least" pain following surgery. The primary outcome measure was change in patients' postoperative NRS scores compared with baseline NRS. Secondary and tertiary outcomes included postoperative day one 24-hour opioid use and the amount of opioid used 24 hours prior to hospital discharge.

RESULTS

Fifty-nine patients were included in the analysis. Baseline patient characteristics were similar with the exception of age. Patients using ketamine had decreased "average" pain scores (percent change between postoperative and preoperative NRS) after surgery (13.5% decrease in the ketamine group vs 15.5% increase in NRS in the placebo group, P = 0.0057). There were no differences in "worst" or "least" pain scores or postoperative opioid use. Side effects between groups were similar.

CONCLUSIONS

Our study demonstrates that a postoperative ketamine infusion at 0.2 mg/kg/hour in addition to opioids results in a statistically significant reduction of "average" pain scores in patients undergoing surgery who take opioids for chronic pain. However, "least" and "worst" pain scores and the amount of opioid used postoperatively did not differ between groups. Thus, the use of a postoperative ketamine infusion at 0.2 mg/kg/hour provides limited benefit in improving pain management for this challenging population.

Effects of nefopam on early postoperative hyperalgesia after cardiac surgery

OBJECTIVE

The purpose of this randomized, double-blind placebo-controlled study was to evaluate the effect of nefopam, a centrally acting antinociceptive compound, on the development of hyperalgesia after sternotomy. Preventive strategy giving nefopam from the early stage of anesthesia was compared with a postoperative strategy only and placebo.

DESIGN

This study was double-blinded and randomized.

SETTING

It was conducted in a single university hospital.

PARTICIPANTS

Ninety American Society of Anesthesiologists II to III patients scheduled for elective cardiac surgery.

INTERVENTIONS

Patients were assigned randomly to receive a 0.3-mg/kg bolus of nefopam at the induction of anesthesia followed by a continuous infusion of 0.065 mg/kg/h for 48 hours (G1), a 0.3-mg/kg bolus of nefopam at the end of surgery followed by a continuous infusion of 0.065 mg/kg/h for 48 hours (G2), or a placebo (G3). Postoperative analgesia was based on morphine patient-controlled analgesia and rescue analgesia when necessary. Postoperative hyperalgesia, pain scores, morphine consumption, and postoperative cognitive dysfunction were assessed for the first 48 hours and thereafter on postoperative days 4 and 7.

MEASUREMENTS AND MAIN RESULTS

The postoperative extent of dynamic hyperalgesia and the decrease of the nociceptive threshold evaluated by von Frey filaments at the sternal midline were smaller in group 1 and group 2 compared with the placebo group at the 24th hour. The primary objective was the extent of hyperalgesia at the midline given as the mean (standard deviation [SD]) (4.4 [2.5] cm for G1, 4.1 [2.7] for G2, and 6.1 [2.7] cm for G3. The punctuate is given as mean (SD) (64 [43] g for G1, 68 [40.8] g for G2, and 32 [27] g for G3; with p < 0.05 for the comparisons of extent and punctuate hyperalgesia between G1 and G3 and G2 and G3). The extent of hyperalgesia was not significantly different among the 3 groups on days 2, 4, and 7 after surgery. There were no significant differences in pain scores, morphine consumption, or postoperative cognitive dysfunctions.

CONCLUSIONS

Nefopam administered during the perioperative period slightly reduced acute hyperalgesia after cardiac surgery, but this was not associated with improved analgesic efficacy.

Review of pharmacological treatment in mood disorders and future directions for drug development

After a series of serendipitous discoveries of pharmacological treatments for mania and depression several decades ago, relatively little progress has been made for novel hypothesis-driven drug development in mood disorders. Multifactorial etiologies of, and lack of a full understanding of, the core neurobiology of these conditions clearly have contributed to these development challenges. There are, however, relatively novel targets that have raised opportunities for progress in the field, such as glutamate and cholinergic receptor modulators, circadian regulators, and enzyme inhibitors, for alternative treatment. This review will discuss these promising new treatments in mood disorders, the underlying mechanisms of action, and critical issues of their clinical application. For these new treatments to be successful in clinical practice, it is also important to design innovative clinical trials that identify the specific actions of new drugs, and, ideally, to develop biomarkers for monitoring individualized treatment response. It is predicted that future drug development will identify new agents targeting the molecular mechanisms involved in the pathophysiology of mood disorders.

The N-methyl-d-aspartic acid receptor antagonist memantine ameliorates and delays the development of arthritis by enhancing regulatory T cells

The neuroendocrine impact on rheumatoid arthritis is not yet fully described although numerous neurotransmitters are shown to act as inflammatory modulators. One of these is the excitatory transmitter glutamate (Glu). In this study, the influence of the Glu receptor (GluR)-mediated effects on collagen-induced arthritis (CIA) was investigated. CIA was induced in DBA/1 mice by immunization with chicken collagen type II (CII). Mice were exposed to the following GluR antagonists: group 1, the N-methyl-D-aspartic acid (NMDA) receptor channel blocker memantine; group 2, the metabotropic GluR antagonist AIDA, and group 3, the excitatory amino acid receptor antagonist kynurenic acid (KA). Arthritis was evaluated clinically and histologically and compared to PBS-treated controls. The effects of treatment on T cell populations and the levels of anti-CII and anti-citrullinated peptide antibodies were evaluated. Memantine treatment significantly improved the course of CIA, reducing synovitis (p = 0.007) and the frequency of erosions (p = 0.007). Memantine treatment up-regulated the expression of Foxp3 in spleen CD4+ T cells followed by an increase in CD4+CD25+ regulatory T cells. The other GluR antagonists, AIDA and KA, had no effect on CIA. These results demonstrate that blockade of the NMDA receptor channel with memantine delays and attenuates the development of arthritis, probably by promoting the development of regulatory T lymphocytes.

Strategies Aimed at Preventing Chronic Post-surgical Pain: Comprehensive Perioperative Pain Management after Total Joint Replacement Surgery

PURPOSE

Chronic post-surgical pain (CPSP) is a frequent outcome of musculoskeletal surgery. Physiotherapists often treat patients with pain before and after musculoskeletal surgery. The purposes of this paper are (1) to raise awareness of the nature, mechanisms, and significance of CPSP; and (2) to highlight the necessity for an inter-professional team to understand and address its complexity. Using total joint replacement surgeries as a model, we provide a review of pain mechanisms and pain management strategies.

SUMMARY OF KEY POINTS

By understanding the mechanisms by which pain alters the body's normal physiological responses to surgery, clinicians selectively target pain in post-surgical patients through the use of multi-modal management strategies. Clinicians should not assume that patients receiving multiple medications have a problem with pain. Rather, the modern-day approach is to manage pain using preventive strategies, with the aims of reducing the intensity of acute postoperative pain and minimizing the development of CPSP.

CONCLUSIONS

The roles of biological, surgical, psychosocial, and patient-related risk factors in the transition to pain chronicity require further investigation if we are to better understand their relationships with pain. Measuring pain intensity and analgesic use is not sufficient. Proper evaluation and management of risk factors for CPSP require inter-professional teams to characterize a patient's experience of postoperative pain and to examine pain arising during functional activities.

Wherefore ketamine?

PURPOSE OF REVIEW

Ketamine has been repeatedly reviewed in this journal but novel developments have occurred in the last few years prompting an update. Interesting recent publications will be highlighted against a background of established knowledge.

RECENT FINDINGS

In the field of anesthesia, particularly in pediatrics, some contributions have been made concerning intramuscular versus intravenous induction. The need for anticholinergic adjuvants has also been clarified. Neuroapoptosis has been observed in animals and its implications for human subjects are discussed in a general context of neurotoxicity. The most important developments, however, are in the treatment of pain. Neurological and urological side effects strongly question long-term use. Other potentially beneficial effects have also been reported, such as anti-inflammatory and antidepressive effects. There are also indications that ketamine may attenuate postoperative delirium in coronary by-pass patients.

SUMMARY

More questions have arisen than have been answered. Some have very grave implications. The issue of neuroapoptosis must be clarified. The long-term effects must be further investigated. On the bright side the effects on postoperative delirium, as well as the anti-inflammatory and antidepressive effects, might open new vistas for an old drug.