Ketamine-Induced Sclerosing Cholangitis (KISC) in a Critically Ill Patient With COVID-19

Ketamine restriction correlates with reduced cholestatic liver injury and improved outcomes in critically ill patients with burn injury

Background & Aims

Ketamine-associated cholestatic liver injury is reported in patients with severe burn injury, but its association with patient outcome is unclear. We investigated the relationship between ketamine exposure, cholestatic liver injury, and outcome of critically ill patients with burn injury.

Methods

In a retrospective study, patients with severe burn injury were analysed across two periods: unrestricted ketamine prescription (ketamine-liberal) and capped ketamine dosage (ketamine-restricted). The primary endpoint was cholestatic liver injury, and the secondary endpoint was 3-month mortality. Binary logistic regression models and the revised electronic causality assessment method were used to measure the strength of associations and causality assessment, respectively.

Results

Of 279 patients (median age 51 [IQR 31-67] years; 63.1% men; burned surface area 28.5%, IQR 20-45%), 155 (56%) were in the ketamine-liberal group, and 124 (44%) were in the ketamine-restricted group, with comparable clinical characteristics, except for ketamine exposure (median doses 265.0 [IQR 0-8,021] mg and 20 [IQR 0-105] mg, respectively; p <0.001). A dose- and time-dependent relationship was observed between ketamine exposure and cholestatic liver injury. Ketamine restriction was associated with a reduced risk of cholestatic liver injury (adjusted odds ratio 0.16, 95% CI 0.04-0.50; p = 0.003) and with a higher probability of 3-month survival (p = 0.035). The revised electronic causality assessment method indicated that ketamine was probably and possibly the cause of cholestatic liver injury for 14 and 10 patients, respectively. Cholangitis was not observed in the ketamine-restricted group. In propensity-matched patients, the risk of 3-month mortality was higher (adjusted odds ratio 9.92, 95% CI 2.76-39.05; p = 0.001) in patients with cholestatic liver injury and ketamine exposure ≥10,000 mg. Other sedative drugs were not associated with liver and patient outcome.

Conclusions

In this cohort, ketamine restriction was associated with less cholestatic liver injury and reduced 3-month mortality.

Impact and implications

In a cohort of 279 critically ill patients with burn injury, ketamine was associated with a risk of liver bile duct toxicity. The risk was found to be dependent on both the dosage and duration of ketamine use. A restriction policy of ketamine prescription was associated with a risk reduction of liver injury and 3-month mortality. These findings have implications for the analgesia and sedation of critically ill patients with ketamine, with higher doses raising safety concerns.

Post-COVID-19 cholangiopathy: Systematic review

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic has had a profound impact on global health, primarily characterized by severe respiratory illness. However, emerging evidence suggests that COVID-19 can also lead to secondary sclerosing cholangitis (SC), referred to as post-COVID-19 cholangiopathy.

AIM

To synthesize currently reported cases to assess the current state of knowledge on post-COVID-19 cholangiopathy.

METHODS

Medical Subject Headings and Health Sciences Descriptors were used to retrieve relevant studies, which were combined using Boolean operators. Searches were conducted on electronic databases including Scopus, Web of Science, and MEDLINE (PubMed). Studies published in English, Spanish, or Portuguese were included, with no restrictions on the publication date. Additionally, the reference lists of retrieved studies were manually searched. Simple descriptive analyses were used to summarize the results. Then the data were extracted and assessed based on Reference Citation Analysis (https://www.referencecitationanalysis.com/).

RESULTS

The initial search yielded a total of 192 articles. After screening, 85 articles were excluded due to duplication, leaving 107 articles for further review. Of these, 63 full-length articles met the inclusion criteria and were included in the analyses. Most of the patients were male and exhibited elevated liver function tests (93.8%). Magnetic resonance imaging revealed duct thickening with contrast enhancement (47.7%), as well as beading of the intrahepatic ducts (45.7%) with peribiliary contrast enhancement on diffusion (28.7%). Liver biopsy results confirmed SC in most cases (74.4%). Sixteen patients underwent liver transplantation, with three experiencing successful outcomes.

CONCLUSION

Post-COVID-19 cholangiopathy is a serious condition that is expected to become increasingly concerning in the coming years, particularly considering long COVID syndromes. Although liver transplantation has been proposed as a potential treatment option, more research is necessary to establish its efficacy and explore other potential treatments.

Secondary Sclerosing Cholangitis After SARS-CoV2: ICU Ketamine Use or Virus-Specific Biliary Tropism and Injury in the Context of Biliary Ischemia in Critically Ill Patients?

Purpose

From the beginning of the Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV2) pandemic, different cases of a cholangiopathy with features of secondary sclerosing cholangitis in critically ill patients (SSC-CIP) have been reported. Patients developing it are generally recovering from severe Coronavirus disease 19 (COVID-19) and required intensive care unit (ICU) admission and mechanical ventilation. Many of them have been administered with ketamine during their ICU stay. The pathogenesis of this novel disease is still debated, and, since prognosis is poor, efforts are needed in order to better understand it.

Patients and Methods

In this review, we focused our attention on COVID-19 SSC clinical, imaging, and histology findings in order to clarify the different pathogenetic options, particularly in regard of the ischemic-direct viral damage and ketamine-related theories, beginning with a recapitulation of SSC-CIP and ketamine-induced cholangiopathy in abusers. The research has been conducted using PubMed and Google Scholar databases. Key-words were "Secondary Sclerosing Cholangiopathy", "SSC-CIP", "Secondary Sclerosing Cholangiopathy in critically ill patients", "Ketamine and cholangiopathy", "Ketamine abusers and liver disease", "Ketamine-related cholangiopathy", "SARS-CoV2 infection and liver disease", "post Covid-19 secondary sclerosing cholangitis", "Covid-19 cholangiopathy".

Results

Many authors, based on the clinical, histological, imaging, and prognostic features of the disease, have pointed out the similarities between post COVID-19 SSC and SSC-CIP; however, peculiar features in the former were not previously observed. Therefore, a direct viral cytopathic action and SARS-CoV2-related coagulopathy are considered the most likely causes. On the other hand, ketamine, with the available data, cannot be surely linked as the main determinant cause of cholangiopathy. Moreover, ketamine-induced cholangitis (KIC) presentation is different from post COVID-19 SSC. Its role as a cofactor precipitating the disease cannot be ruled out.

Conclusion

Post COVID-19 SSC is a rare clinical entity following severe COVID-19 disease. The most accepted theory is that a sum of different insults determines the disease: biliary ischemia, direct viral damage, toxic bile, possibly worsened by ketamine and hyperinflammation due to the cytokine storm. Given the severe prognosis of the disease, with persistent cholangiopathy, organ failure, and orthotopic liver transplantation (OLT), further study on this novel clinical entity is needed.

Secondary Sclerosing Cholangitis due to Severe COVID-19: An Emerging Disease Entity?

INTRODUCTION

Coronavirus disease 2019 (COVID-19) can lead to many extrapulmonary manifestations. In this case series, we report on 7 patients developing secondary sclerosing cholangitis (SSC) after severe COVID-19 with intensive care treatment.

METHODS

Between March 2020 and November 2021, 544 patient cases with cholangitis treated at a German tertiary care centre were screened for SSC. Patients found to be suffering from SSC were assigned to COVID-19 group if SSC presented after a severe course of COVID-19 and to non-COVID-19 group if not. Peak liver parameters as well as intensive care treatment factors and data generated from liver elastography were compared between both groups.

RESULTS

We identified 7 patients who developed SSC after a severe course of COVID-19. In the same period, 4 patients developed SSC due to other causes. Mean values of gamma-glutamyl transferase (GGT) and alkaline phosphatase (ALP) were higher in the COVID-19 group than in the non-COVID-19 group (GGT: 2,689 U/L vs. 1,812 U/L and ALP: 1,445 U/L vs. 1,027 U/L), whereas intensive care treatment factors were comparable in both groups. Only the mean duration of mechanical ventilation was shorter in the COVID-19 group than in the non-COVID-19 group (22.1 days vs. 36.7 days). Liver elastography indicated a fast progression to liver cirrhosis with a mean liver stiffness of 17.3 kilopascals (kPa) in less than 12 weeks in the COVID-19 group.

CONCLUSIONS

Our data suggest a more severe course of SSC when caused by SARS-CoV-2. Reasons for this are probably multifactorial, including a direct cytopathogenic effect of the virus.

Profile of liver cholestatic biomarkers following prolonged ketamine administration in patients with COVID-19

BACKGROUND

To investigate the possible influence of prolonged ketamine (K) or esketamine (ESK) infusion on the profile of liver cholestatic biomarkers in patients with COVID-19 infection.

METHODS

A retrospective analysis was performed on 135 patients with COVID-19 related ARDS who received prolonged K or ESK infusion. They were compared to 15 COVID-19 ICU patients who did not receive K/ESK while being mechanically ventilated and 108 COVID-19 patients who did not receive mechanical ventilation nor K/ESK. The profile of the liver function tests was analysed in the groups.

RESULTS

Peak values of ALP, GGT and bilirubin were higher in the K/ESK group, but not for AST and ALT. Peak values of ALP were significantly higher among patients who underwent mechanical ventilation and who received K/ESK, compared with mechanically ventilated patients who did not receive K/ESK. There was a correlation between these peak values and the cumulative dose and duration of K/ESK therapy.

CONCLUSIONS

Based on the observations of biliary anomalies in chronic ketamine abusers, prolonged exposure to ketamine sedation during mechanical ventilation may also be involved, in addition to viral infection causing secondary sclerosing cholangitis. The safety of prolonged ketamine sedation on the biliary tract requires further investigations.

COVID-19: gastrointestinal and hepatobiliary manifestations

SARS-CoV-2 is the viral agent of COVID-19, a pandemic that surfaced in 2019. Although predominantly a respiratory ailment, patients with COVID-19 can have gastrointestinal (GI) and hepatobiliary manifestations. These manifestations are often mild and transient, but they can be severe and consequential. In the GI tract, ischemic enterocolitis is the most common and significant consequence of COVID-19. In the liver, the reported pathologic findings may often be related to consequences of severe systemic viral infection, but reports of hepatitis presumed to be due to SARS-CoV-2 suggest that direct viral infection of the liver may be a rare complication of COVID-19. In both the GI tract and liver, lingering symptoms of GI or hepatic injury after resolution of pulmonary infection may be part of the evolving spectrum of long COVID.

Acute liver injury in COVID-19 patients hospitalized in the intensive care unit: Narrative review

In recent years, humanity has been confronted with a global pandemic due to coronavirus disease 2019 (COVID-19), which has caused an unprecedented health and economic crisis worldwide. Apart from the respiratory symptoms, which are considered the principal manifestations of COVID-19, it has been recognized that COVID-19 constitutes a systemic inflammatory process affecting multiple organ systems. Across the spectrum of organ involvement in COVID-19, acute liver injury (ALI) has been gradually gaining increasing attention by the international scientific community. COVID-19 associated liver impairment can affect a considerable proportion of COVID-19 patients and seems to correlate with the severity of the disease course. Indeed, COVID-19 patients hospitalized in the intensive care unit (ICU) run a greater risk of developing ALI due to the severity of their clinical condition and in the context of multi-organ failure. The putative pathophysiological mechanisms of COVID-19 induced ALI in ICU patients remain poorly understood and appear to be multifactorial in nature. Several theories have been proposed to explain the occurrence of ALI in the ICU setting, such as hypoperfusion and ischemia due to hemodynamic instability, passive liver congestion as a result of congestive heart failure, ischemia-reperfusion injury, hypoxia due to respiratory failure, mechanical ventilation itself, sepsis and septic shock, cytokine storm, endotheliitis with concomitant coagulopathy, drug-induced liver injury, parenteral nutrition and direct cytopathic viral effect. It should be noted that no specific therapy for COVID-19 induced ALI exists. Therefore, the therapeutic approach lies in preventive measures and is exclusively supportive once ALI ensues. The aim of the current review is to scrutinize the existing evidence on COVID-19 associated ALI in ICU patients, explore its clinical implications, shed light on the underlying pathophysiological mechanisms and propose potential therapeutic approaches. Ongoing research on the particular scientific field will further elucidate the pathophysiology behind ALI and address unresolved issues, in the hope of mitigating the tremendous health consequences imposed by COVID-19 on ICU patients.

Impact of COVID-19 on the liver and on the care of patients with chronic liver disease, hepatobiliary cancer, and liver transplantation: An updated EASL position paper

The COVID-19 pandemic has presented a serious challenge to the hepatology community, particularly healthcare professionals and patients. While the rapid development of safe and effective vaccines and treatments has improved the clinical landscape, the emergence of the omicron variant has presented new challenges. Thus, it is timely that the European Association for the Study of the Liver provides a summary of the latest data on the impact of COVID-19 on the liver and issues guidance on the care of patients with chronic liver disease, hepatobiliary cancer, and previous liver transplantation, as the world continues to deal with the consequences of the COVID-19 pandemic.

Gamma-glutamyltransferase is a strong predictor of secondary sclerosing cholangitis after lung transplantation for COVID-19 ARDS

BACKGROUND

Lung transplantation (LTx) can be considered for selected patients suffering from COVID-19 acute respiratory distress syndrome (ARDS). Secondary sclerosing cholangitis in critically ill (SSC-CIP) patients has been described as a late complication in COVID-19 ARDS survivors, however, rates of SSC-CIP after LTx and factors predicting this detrimental sequela are unknown.

METHODS

This retrospective analysis included all LTx performed for post-COVID ARDS at 8 European LTx centers between May 2020 and January 2022. Clinical risk factors for SSC-CIP were analyzed over time. Prediction of SSC-CIP was assessed by ROC-analysis.

RESULTS

A total of 40 patients were included in the analysis. Fifteen patients (37.5%) developed SSC-CIP. GGT at the time of listing was significantly higher in patients who developed SSC-CIP (median 661 (IQR 324-871) vs 186 (109-346); p = 0.001). Moreover, higher peak values for GGT (585 vs 128.4; p < 0.001) and ALP (325 vs 160.2; p = 0.015) were found in the 'SSC' group during the waiting period. Both, GGT at the time of listing and peak GGT during the waiting time, could predict SSC-CIP with an AUC of 0.797 (95% CI: 0.647-0.947) and 0.851 (95% CI: 0.707-0.995). Survival of 'SSC' patients was severely impaired compared to 'no SSC' patients (1-year: 46.7% vs 90.2%, log-rank p = 0.004).

CONCLUSIONS

SSC-CIP is a severe late complication after LTx for COVID-19 ARDS leading to significant morbidity and mortality. GGT appears to be a sensitive parameter able to predict SSC-CIP even at the time of listing.

Secondary sclerosing cholangitis after critical COVID-19: Three case reports

BACKGROUND

The global coronavirus disease 2019 (COVID-19) pandemic has caused more than 5 million deaths. Multiorganic involvement is well described, including liver disease. In patients with critical COVID-19, a new entity called "post-COVID-19 cholangiopathy" has been described.

CASE SUMMARY

Here, we present three patients with severe COVID-19 that subsequently developed persistent cholestasis and chronic liver disease. All three patients required intensive care unit admission, mechanical ventilation, vasopressor support, and broad spectrum antibiotics due to secondary infections. Liver transplant protocol was started for two of the three patients.

CONCLUSION

Severe COVID-19 infection should be considered a potential risk factor for chronic liver disease and liver transplantation.

Secondary sclerosing cholangitis after COVID-19 pneumonia: a report of two cases and review of the literature

Secondary sclerosing cholangitis in critically ill patients (SC-CIP) is a rare disease characterized by chronic cholestasis. The underlying pathophysiology of SC-CIP is not fully understood, and prognosis in severe cases remains poor with liver transplantation remaining the only curative treatment option. There is a growing amount of literature describing patients with chronic cholangiopathy after COVID-19 infection. The vast majority of the patients described in these reports were male and had a poor outcome. While the exact percentage of patients with COVID-19-related SC-CIP cannot be estimated accurately due to a lack of larger studies, an increase in patients with long-term complications of chronic cholestatic liver disease after severe COVID19-pneumonia can be expected in the upcoming years. Treatment options remain limited and further research is needed to improve the dismal prognosis of SC-CIP. Here, we present the cases of two patients who developed SC-CIP after prolonged intensive care unit stay due to severe COVID-19 pneumonia. Both patients required invasive ventilation for 31 and 141 days, respectively, as well as extra-corporal membrane oxygenation for 23 and 87 days. The patients suffered from jaundice and severe pruritus, and typical features of SC-CIP were present by MRCP and ERC. Repeated removal of biliary casts resulted in some alleviation of their clinical symptoms, but cholestasis parameters remain elevated. Furthermore, an increased liver stiffness was indicative of advanced fibrosis in both patients. In addition to these two case reports, we provide a concise review of the literature of SC-CIP after COVID-19 infection and discuss risk factors, treatment options and prognosis.

Imaging features of COVID-19-associated secondary sclerosing cholangitis on magnetic resonance cholangiopancreatography: a retrospective analysis

Background

Despite emerging reports of secondary sclerosing cholangitis (SSC) in critically ill COVID-19 patients little is known about its imaging findings. It presents as delayed progressive cholestatic liver injury with risk of progression to cirrhosis. Diagnosis cannot be made based on clinical presentation and laboratory markers alone. Magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) can aid in the diagnosis. The aim of this study was to describe MRI/MRCP imaging features of COVID-19-associated SSC.

Results

Seventeen patients (mean age 60.5 years, 15 male) who underwent MRI/MRCP were included. All had been admitted to intensive care unit (ICU) (median duration of ICU stay 10 weeks, range, 2–28 weeks) and developed acute respiratory distress syndrome requiring mechanical ventilation. On imaging, all patients had intrahepatic bile duct strictures and 10 (58.8%) had associated upstream dilatation. Intrahepatic bile duct beading was seen in 14 cases (82.3%). Only one patient (5.9%) had extrahepatic bile duct stricturing. Patchy arterial phase hyperenhancement and high signal on T2- and diffusion-weighted images were seen in 7 cases (53.8%) and 9 cases (52.9%), respectively. Biliary casts were seen in 2 cases (11.8%). Periportal lymphadenopathy and vascular complications were not seen.

Conclusion

On MRI/MRCP, COVID-19-associated SSC presents with multiple intrahepatic bile duct strictures with or without upstream dilatation and intrahepatic bile duct beading. Surrounding hepatic parenchymal changes including alterations in enhancement and T2 signal are common. The extrahepatic biliary tree was typically spared and periportal lymphadenopathy was missing in all patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13244-022-01266-9.

Biliary Tract Injury in Patients With COVID-19: A Review of the Current Literature

Multiple studies and extensive clinical experience have shown that COVID-19 can impact the hepatobiliary system, with most reports describing primarily hepatocellular injury with elevations of aspartate aminotransferase and alanine aminotransferase. In addition to hepatocellular injury, recent literature has described a pattern of severe biliary tract injury resulting in patients with COVID-19. This novel syndrome, termed COVID-19 cholangiopathy, may have severe consequences for affected patients. This article will examine the literature describing this novel entity, its relationship to secondary sclerosing cholangitis, clinical outcomes, and proposed mechanisms underlying this form of biliary injury.

Persistent Cholestatic Injury and Secondary Sclerosing Cholangitis in COVID-19 Patients

CONTEXT.–

Coronavirus disease 2019 (COVID-19) has been associated with liver injury, and a small subset of patients recovering from severe disease have shown persistent markedly elevated liver biochemistries for months after infection.

OBJECTIVE.–

To characterize persistent biliary injury after COVID-19.

DESIGN.–

A search of the pathology archives identified 7 post-COVID-19 patients with persistent biliary injury, and the clinical, radiologic, and pathologic features were assessed.

RESULTS.–

All patients in this cohort presented with respiratory symptoms and had a complicated clinical course with acute elevation of liver biochemistries. Alkaline phosphatase (ALP) was markedly and persistently elevated after discharge (median peak ALP: 1498 IU/L, at a median of 84 days from diagnosis). Magnetic resonance cholangiopancreatography (MRCP) showed 3 patients with irregularity, stricturing, and dilatation of intrahepatic ducts; no radiographic abnormalities were identified in the remaining 4 patients. Liver biopsies showed mild portal changes with features of cholestatic injury in 4 patients (bile duct injury and canalicular cholestasis) and marked biliary obstruction in 2 patients (profound cholestasis, ductular reaction, and bile infarcts), but no SARS-CoV-2 ribonucleic acid (RNA) was identified on in-situ hybridization. On follow-up, most patients had minimal intervention and showed marked improvement of liver biochemistries but with mild persistent elevation of ALP.

CONCLUSIONS.–

A subset of critically ill COVID-19 patients demonstrates marked and persistent cholestatic injury, with radiographic and histologic evidence of secondary sclerosing cholangitis, suggesting that cholestatic liver disease and secondary sclerosing cholangitis may be long-term sequelae of COVID-19 acute illness as a longstanding manifestation of critical illness.

Drug-induced bile duct injury: new agents, new mechanisms

PURPOSE OF REVIEW

Drug-induced bile duct injury can be caused by a long list of agents. In most cases, damage is because of T-cell-mediated idiosyncratic reactions. Recently, a number of new agents, including not only drugs but also herbal supplements, have been incriminated and new mechanisms of bile duct injury have emerged. This review will focus on these new data.

RECENT FINDINGS

New members of drug families already known to be responsible for bile duct injury have been incriminated. New players have been identified, such as herbal supplements, like kratom, and recreational drugs, such as ketamine used outside the medical setting. Anticytokine monoclonal antibodies are rarely involved. In contrast, antineoplastic treatments are of growing concern, especially immune checkpoint inhibitors, which induce immune-related adverse effects because of the excessive stimulation of the immune system and its lack of regulation.

SUMMARY

Two patterns of bile duct injury are recognized. Drug-induced small-duct cholangiopathies target the smaller bile ducts; acute injuries eventually progress to chronic disease in the form of the vanishing bile duct syndrome. Drug-induced sclerosing cholangitis target large bile ducts, with a protracted chronic course; the onset of symptoms may be delayed after drug discontinuation; potentially severe, life-threatening complications can occur.

Secondary sclerosing cholangitis as cause of persistent jaundice in patients with severe COVID-19

BACKGROUND & AIMS

Little is known about cholestasis, including its most severe variant secondary sclerosing cholangitis (SSC), in critically ill patients with coronavirus disease 19 (COVID-19). In this study, we analysed the occurrence of cholestatic liver injury and SSC, including clinical, serological, radiological and histopathological findings.

METHODS

We conducted a retrospective single-centre analysis of all consecutive patients admitted to the intensive care unit (ICU) as a result of severe COVID-19 at the University Hospital Zurich to describe cholestatic injury in these patients. The findings were compared to a retrospective cohort of patients with severe influenza A.

RESULTS

A total of 34 patients with severe COVID-19 admitted to the ICU were included. Of these, 14 patients (41%) had no cholestasis (group 0), 11 patients (32%, group 1) developed mild and 9 patients (27%, group 2) severe cholestasis. Patients in group 2 had a more complicated disease course indicated by significantly longer ICU stay (median 51 days, IQR 25-86.5) than the other groups (group 0: median 9.5 days, IQR 3.8-18.3, P = .001; and group 1: median 16 days, IQR 8-30, P < .05 respectively). Four patients in group 2 developed SSC compared to none in the influenza A cohort. The available histopathological findings suggest an ischaemic damage to the perihilar bile ducts.

CONCLUSIONS

The development of SSC represents an important complication of critically ill COVID-19 patients and needs to be considered in the diagnostic work up in prolonged cholestasis. The occurrence of SSC is of interest in the ongoing pandemic since it is associated with considerable morbidity and mortality.

Severe Encephalatrophy and Related Disorders From Long-Term Ketamine Abuse: A Case Report and Literature Review

Ketamine is a glutamate N-methyl D-aspartate receptor antagonist and an anaesthetic agent that has been effectively used to treat depression. However, ketamine has also been increasingly used for recreational purposes. The dissociative side-effects of ketamine use, such as hallucinations, are the reason for abuse. Additionally, long-term ketamine abuse has been highly associated with liver-gallbladder and urinary symptoms. The present study reports the case of a 28-year-old young male adult with an 8-year history of daily inhalation of ketamine. We investigated the association between ketamine abuse and the mechanism of its adverse effects, particularly encephalatrophy, and attempted to find a link between these disorders. These results would help us to better understand ketamine usage, ketamine abuse effects and the addictive mechanism. To the best of our knowledge, the present case is the first report of severe brain atrophy related to ketamine abuse. Details of the patient are presented and the mechanism of the encephalatropy-associated ketamine abuse is discussed. Furthermore, organ dysfunction following chronic ketamine abuse may indicate that the side effects are the result of comprehensive action on multiple regions in the brain.