Radiologist-guided Analgosedation with Ketamine/Midazolam: A Feasible Strategy to Expand Percutaneous Tumor Ablation Capacity

Abstract

Purpose

Percutaneous thermal tumor ablation is an established oncologic treatment, but rising case numbers and limited anesthesia resources increasingly restrict procedural capacity. Radiologist-guided analgosedation may offer a pragmatic alternative to general anesthesia for selected ablation procedures. This study evaluates the safety, technical success, and impact on procedural throughput of performing microwave (MWA) and radiofrequency ablation (RFA) of hepatic, renal, and osseous tumors under analgosedation with midazolam and S-ketamine.

Materials and Methods

In this retrospective single-center study, 140 percutaneous tumor ablations performed in 115 patients under radiologist-guided analgosedation between January 2022 and July 2024 were analyzed. The primary endpoint was the occurrence of sedation-related complications. Secondary endpoints included technical success, ablation-related complications, and changes in procedural volume compared with ablations performed under general anesthesia. Technical success was defined as complete tumor ablation with an adequate safety margin.

Results

Of 115 planned patients, 113 (98.3%) were completed as intended. No major complications occurred. One minor complication (subcapsular hepatic hematoma, CIRSE grade 1) was observed. Four patients (3.5%) experienced transient post-interventional vomiting. No respiratory, cardiovascular, or anaphylactic adverse events were recorded. Transitioning from general anesthesia to analgosedation resulted in a significant increase in procedural volume from 2.1 to 6.3 ablations per month (p < 0.05). Mean in-room time was significantly shorter under analgosedation compared with general anesthesia (42 ± 34 min vs. 98 ± 42 min; p < 0.05).

Conclusion

Radiologist-guided analgosedation with midazolam and S-ketamine is a feasible and safe approach for percutaneous thermal ablation of liver, kidney, and bone tumors. It enables high technical success without increasing complication rates and can substantially expand procedural capacity where anesthesiology resources are limited. Adequate training, structured workflows, and robust emergency preparedness are essential for safe implementation.

Key Points

• Given the limited resources available for anaesthesia and the increasing demand for minimally invasive therapeutic procedures, the question of alternative concepts arises.

• At present, there is a lack of scientific research on the feasibility of percutaneous thermal ablation under analgosedation.

• This study demonstrated that percutaneous thermal tumour ablation under analgosedation is an effective method of achieving complete tumour ablation without increasing the rate of complications.

• It was shown that the use of analgosedation with S-ketamine and midazolam could increase procedural number of percutaneous thermal ablation procedures and therefore could reduce waiting times.

Citation Format

• Beeskow AB, Struck MF, Elkilany A et al. Radiologist-guided Analgosedation with Ketamine/Midazolam: A Feasible Strategy to Expand Percutaneous Tumor Ablation Capacity. Rofo 2026; DOI 10.1055/a-2786-2622

Zusammenfassung

Hintergrund

Die perkutane thermische Tumorablation ist ein etabliertes onkologisches Therapieverfahren. Steigende Fallzahlen und limitierte anästhesiologische Ressourcen führen jedoch zunehmend zu Einschränkungen der prozeduralen Kapazität. Die radiologisch geführte Analgosedierung kann bei ausgewählten Ablationsverfahren eine praktikable Alternative zur Allgemeinanästhesie darstellen. Ziel dieser Studie war die Evaluation von Sicherheit, technischem Erfolg und Einfluss auf den Prozedurendurchsatz bei Mikrowellen- (MWA) und Radiofrequenzablationen (RFA) hepatischer, renaler und ossärer Tumoren unter Analgosedierung mit Midazolam und S-Ketamin.

Material und Methoden

In dieser retrospektiven monozentrischen Studie wurden 140 perkutane Tumorablationen bei 115 Patientinnen und Patienten analysiert, die zwischen Januar 2022 und Juli 2024 unter radiologisch geführter Analgosedierung durchgeführt wurden. Primärer Endpunkt war das Auftreten sedierungsassoziierter Komplikationen. Sekundäre Endpunkte umfassten den technischen Erfolg, ablationsbedingte Komplikationen sowie Veränderungen des Prozedurvolumens im Vergleich zu unter Allgemeinanästhesie durchgeführten Ablationen. Der technische Erfolg wurde als vollständige Tumorablation mit adäquatem Sicherheitsrand definiert.

Ergebnisse

113 von 115 geplanten Eingriffen (98,3%) wurden wie vorgesehen abgeschlossen. Schwere Komplikationen traten nicht auf. Eine leichte Komplikation (subkapsuläres Leberhämatom, CIRSE-Grad 1) wurde beobachtet. Vier Patientinnen und Patienten (3,5%) zeigten vorübergehendes postinterventionelles Erbrechen. Respiratorische, kardiovaskuläre oder anaphylaktische Nebenwirkungen traten nicht auf. Nach Umstellung von Allgemeinanästhesie auf Analgosedierung stieg das monatliche Prozedurvolumen signifikant von 2,1 auf 6,3 Ablationen (p<0,05). Die mittlere Raumbelegungszeit war unter Analgosedierung signifikant kürzer als unter Allgemeinanästhesie (42 ± 34 min vs. 98 ± 42 min; p<0,05).

Schlussfolgerung

Die radiologisch geführte Analgosedierung mit Midazolam und S-Ketamin ist ein sicheres und praktikables Verfahren für die perkutane thermische Ablation von Leber-, Nieren- und Knochentumoren. Sie ermöglicht hohe technische Erfolgsraten ohne Zunahme der Komplikationsrate und kann bei limitierten anästhesiologischen Ressourcen die prozedurale Kapazität deutlich erhöhen. Voraussetzungen für eine sichere Implementierung sind eine adäquate Schulung, strukturierte Abläufe und eine verlässliche Notfallbereitschaft.

Kernaussagen

• Angesichts begrenzter anästhesiologischer Ressourcen und einer zunehmenden Nachfrage nach minimal-invasiven Therapieverfahren gewinnen alternative Behandlungskonzepte an Bedeutung.

• Bisher liegen nur begrenzte wissenschaftliche Daten zur Durchführbarkeit perkutaner thermischer Ablationen unter Analgosedierung vor.

• Die vorliegende Studie zeigt, dass die perkutane thermische Tumorablation unter Analgosedierung eine effektive Methode zur vollständigen Tumorablation darstellt, ohne die Komplikationsrate zu erhöhen.

• Es konnte gezeigt werden, dass der Einsatz einer Analgosedierung mit S-Ketamin und Midazolam die Anzahl perkutaner thermischer Ablationen steigern und dadurch Wartezeiten reduzieren kann.

Keywords

analgosedation - radiologist-guided sedation - S-ketamine - interventional oncology - thermal tumor ablation - workflow optimization

Introduction

Percutaneous ablations such as radiofrequency ablation (RFA) and microwave ablation (MWA) are now an integral part of modern tumor therapies [1] [2]. Due to their minimally invasive nature, these procedures can be carried out during short hospital stays (usually <2 days) [3]. As the number of cases of tumors with liver metastases continues to rise, there is an urgent need to provide patients with prompt, high-quality treatment, and appropriate follow-up care [4]. In many European centers, it is common practice to perform percutaneous RFA and MWA under general anesthesia [3], which means that an anesthesiology team consisting of a consultant anesthesiologist and a specialized anesthesiology nurse is required for each procedure in addition to the interventional radiology team. However, in times of high economic pressures on hospitals and, in some cases, a shortage of junior staff and personnel, the capacity for this type of procedure is often limited, meaning that the procedures might not be performed as promptly as desired [4] [5] [6]. A possible partial solution to this problem could be to train radiologists to independently perform analgosedation that enables thermoablation, so that general anesthesia with an anesthesia team is only required for more complex procedures.

Analgosedation is already well established in interventional radiology, with midazolam and propofol as commonly used agents. Previous studies have demonstrated their adequate efficacy in various interventional procedures [7] [8]. These techniques are frequently employed for painful interventions such as drain placements, dilatations, and embolizations [9]. Effective analgosedation is essential for local ablations, as patient movement can significantly hinder accurate placement of the ablation catheter [10].

One possible scheme for such analgosedation would be the combination of midazolam and S-ketamine [11]. S-ketamine is an intravenously injectable general anesthetic with a strong analgesic effect, which causes a so-called dissociative anesthesia without cardiorespiratory depression [12]. After intravenous bolus administration, it has a rapid onset of action (< 1 min) with a duration of action of approx. 10–15 minutes, making it well suited for short, potentially painful procedures such as RFA and MWA. Relative contraindications include unstable angina pectoris or myocardial infarction in the last six months. An undesirable side effect is hallucinations and nightmares, which occur in 10–30 % of cases. These can be reduced by pre-administering midazolam [13] [14].

In our hospital, we switched to analgosedation with midazolam/S-ketamine for percutaneous RFA and MWA of liver, kidney, and bone tumors in January 2022. This retrospective study aimed to analyze the thermal ablations performed in our department in terms of technical success and complication rate. Additionally, the study aimed to determine the potential increase in procedure rates using analgosedation compared to procedures under general anesthesia.

Material and Methods

Study population

Institutional ethics committee approval was obtained. Using the institutional radiological information system (RIS), we retrospectively analyzed 197 patients with 236 thermal tumor ablations. They were subdivided into two groups: Group one included percutaneous thermal ablations of liver, kidney, and bone tumors, performed under general anesthesia between January 2019 and July 2024 (n=82). In February 2022, we transitioned to performing percutaneous ablations under analgosedation using midazolam and S-ketamine. All patients (n=115) treated with this protocol between January 2022 and July 2024 were included in the second group: 101 patients with microwave ablations (MWA) and 14 radiofrequency ablations (RFA). The exact breakdown of ablations under analgosedation is shown in [Fig. 1]. We analyzed sex, age, body mass index (BMI), American Society of Anesthesiologists Physical Status (ASA-Score), tumor side, and comorbidities, reviewing the patient’s files. In addition, we recorded the in-room time using our room scheduling system (appointment schedule).

Fig. 1 The flowchart illustrates the distribution of microwave and radiofrequency ablation in liver, kidney, and bone performed under analgosedation.

Inclusion criteria were the following: All patients were presented to an interdisciplinary tumor board prior to ablation. All patients had a pre-ablation computed tomography (CT) or magnetic resonance imaging (MRI) scan that was no more than four weeks old. All patients gave written informed consent at least 24 hours before the ablation.

The exclusion criteria were possible contraindications to analgosedation, such as serious pre-existing cardiovascular or pulmonary conditions, or allergies to medication. These were recorded during the information session.

By analyzing the intervention reports, we determined whether the procedures were successfully completed or had to be aborted. Technical success was defined as complete tumor ablation, including an adequate safety margin. The intervention reports also noted whether any peri- or post-intervention complications occurred. The occurrence of sedation-related complications, subdivided into respiratory, cardiovascular, vegetative and anaphylactic complications was defined as primary endpoint. Secondary endpoints were the technical success rate and ablation-related complications.

Procedure of the interventions and analgosedation

When the concept was first introduced, a senior radiologist, board certified EBIR-ES (European Board of Interventional Radiology – Endovascular Specialist), who had completed the CIRSE sedation course and had completed one year of internal medicine training was responsible for managing peri-interventional monitoring and medication. This consultant then trained the radiology residents to supervise this process. All personnel involved in the intervention were trained in performing manual ventilation and cardiopulmonary resuscitation.

All patients received intravenous access, through which a continuous infusion of Ringer's acetate was administered during the procedure. Before the start of the intervention, patients received a standard dose of 4 mg ondansetron IV for the prophylaxis of post-interventional nausea and vomiting. In addition, all patients received oxygen via nasal cannula at a flow rate of 3 L/min for pre-oxygenation. A calm environment was maintained, and patients were addressed in a reassuring manner whenever necessary.

Peri-procedural monitoring of vital signs, consisting of a continuous 3-channel ECG lead, pulse oximetry, and non-invasive blood pressure measurement at 3-minute intervals were monitored by a trained doctor or a trained nurse and manually recorded.

After positioning and sterile draping, the patients received midazolam IV in 1 mg increments until the onset of light drowsiness (sedation grade II correlated to Zalunardo) while maintaining spontaneous breathing [15]. An emergency kit, ventilation equipment, and suction were always available in the intervention room. In addition, the hospital’s emergency medical team – consisting of a certified, experienced anesthesiologist and an intensive care nurse – could be on site within minutes in the event of an emergency.

Before the placement of the thermal ablation probes, patients received local anesthesia with lidocaine at the puncture site. For radiofrequency ablation (RFA), we used the RITA system (Angiodynamics, Latham, USA). For microwave ablation (MWA), we employed either the AMICA system (water-cooled) from Plus Medica, Düsseldorf, Germany, or the NeuWave system (CO₂-cooled) from Johnson & Johnson, New Brunswick, USA. Ablation probes were placed under image guidance. Shortly before the ablation was initiated, S-ketamine (0.5 mg/kg body weight) was administered to achieve adequate analgosedation for the duration of the procedure. Radiofrequency or microwave ablation was then performed according to standard protocol, followed by a control CT scan to confirm complete ablation and exclude complications. Finally, patients were transferred to a monitored recovery room for postprocedural observation, typically lasting approximately two hours under the supervision of a trained nurse ([Fig. 2]).

Fig. 2 The flowchart illustrates the procedure workflow for percutaneous thermal ablations under radiologist-guided analgosedation.

Complications

Major and minor complications, subdivided into respiratory, cardiovascular vegetative, and anaphylactic reactions, were documented during the intervention, during the two-hour follow-up phase and during the inpatient stay (one night) in medical notes and intervention reports. The CIRSE classification system for complications was used to grade the complications [16].

Statistical analysis

All analyses were performed using SPSS statistical software V28 (IBM, Armonk, NY, USA). The distribution of the variables was tested using the Shapiro-Wilk test for normality. This study primarily employs descriptive statistics, presenting quantitative variables as mean values and standard deviations (SD). Analysis included Mann-Whitney U Test for continuous variables and paired t-test for categorical variables. A p-value < 0.05 was considered statistically significant.

Results

Patient characteristics

A total of 197 patients (165 male, 32 female; mean age 64 ± 17 years) who underwent image-guided tumor ablation procedures were included in this retrospective study. Ablations were performed in lesions located in bone, liver, or kidney. All bone ablations were carried out for osteoid osteomas, with one lesion treated per patient. Renal ablations targeted renal cell carcinomas; 28 patients had a single lesion treated, while two patients underwent ablation of two lesions each. Among patients with hepatic tumors (n = 148), 119 had hepatocellular carcinoma (HCC), 12 had intrahepatic cholangiocarcinoma (ICC), and 17 presented with hepatic metastases. All HCC patients had underlying liver cirrhosis, classified as Child-Pugh A in 103 cases, Child B in 15, and Child C in one case. Regarding comorbidities across the cohort, 38 patients had type 2 diabetes mellitus, 43 had arterial hypertension, and 16 had coronary artery disease (including seven with prior coronary stenting). One patient had an infrarenal aortic prosthesis following abdominal aortic aneurysm repair. Additionally, three patients tested positive for hepatitis C, and 11 patients had benign prostatic hyperplasia, while one patient had rheumatoid arthritis. See [Table 1].

Table 1 Patient characteristics and comorbidities.

Characteristic	Analgosedation	General anaesthesia
Number of patients (n)	115	82
Sex (male/female)	94/21	71/11
Mean age (years)	62 ± 14	66 ± 21
Body mass index (Kg/m2)	22 ± 6	24 ± 9
mean ASA	1.8	2.2
Tumor site – Bone (osteoid osteoma)	14	9
Tumor site – Kidney (RCC)	19	11
Tumor site – Liver (HCC/ICC/Metastases)	82 (58/10/14)	66 (61/2/13)
Total number of ablated tumors	140	96
HCC patients with cirrhosis (Child A/B/C)	58 (47/10/1)	61 (56/5/0)
Diabetes mellitus type 2	14	24
Arterial hypertension	17	26
Coronary heart disease (CHD)	5	11
CHD with coronary stent	3	4
Infrarenal aortic prosthesis	1	0
Hepatitis C positive	3	0
Benign prostatic hyperplasia	7	4
Rheumatic arthritis	0	2

Ablations under general anesthesia

Between January 2019 and July 2024, we performed 76 percutaneous ablations of liver, kidney, and bone tumors under general anesthesia. Between January 2022 and July 2024, only six ablations (n=2 liver and n=4 bone) were performed under general anesthesia at the patient's request. All ablations were performed as planned, resulting in a technical success rate of 100%. There were no major complications. In one case, a perihepatic hematoma occurred after the ablation, which resolved without further intervention, the hospital stay was not extended as a result (Grade 1 according to CIRSE Classification System for Complications). Mean in-room time was 98 ± 42 minutes.

Ablations under analgosedation

The cohort comprises 140 consecutive percutaneous ablations on 115 patients (82 male, 61±12 years old, BMI 26.58±9.22) in 115 sessions performed between January 2022 and July 2024.

Of the 115 planned patients with percutaneous ablation, 113 (98.3%) were successfully performed and completed. This reflects a statistically significant increase in procedural volume, from 2.1 ablations per month under general anesthesia to 6.3 per month following the implementation of analgosedation (p < 0.05).

Two ablations (1.7%) had to be canceled. The first was due to unexpected, significant patient agitation after the administration of 1 mg of IV midazolam, which prevented the patient from remaining still. The second was canceled because of insufficient analgesia during the ablation despite two boluses of S-ketamine (0.5 mg/kg body weight) each. In this latter case, two metastases from a colorectal carcinoma were scheduled for ablation, but the procedure was aborted after the first lesion was treated.

Eleven patients underwent repeat ablation at a later time due to newly developed tumors (not local recurrences) and consented to having the procedure performed again under the same regime of analgosedation.

The patients received an average of 2.26±1.11 mg midazolam IV (range 1.0–4.0 mg) and 52.71±26.29 mg (range 30.0–120.0 mg) S-ketamine IV; there were no significant differences between men and women (p=0.32) or between MWA and RFA (p=0.27) or between ablations of the different organs (p=0.74).

During the period analyzed, 11 patients received a second MWA due to the occurrence of new tumors (n=8 HCC and n=3 metastases). There were no local recurrences (recurrences within the pre-treated area) observed during this time. Mean in-room time was 42 ± 34 minutes, which was significantly faster than in the general anesthesia group (p<0.05). There were no major complications. There was one minor complication (Grade 1 according to CIRSE Classification System for Complications): a subcapsular liver hematoma of 4 mm occurred post-interventionally without clinical symptoms, which resorbed without further measures. The hospital stay was not extended as a result.

There were no other peri-interventional complications. Furthermore, there were no respiratory, cardiovascular, or anaphylactic complications.

In four cases (3.5%), post-interventional vomiting occurred despite prior administration of 4 mg ondansetron, and resolved spontaneously within two hours under routine postprocedural observation.

Discussion

In this retrospective single-center analysis, we evaluated the feasibility and safety of radiologist-guided analgosedation using midazolam and S-ketamine for percutaneous thermal ablation of liver, kidney, and bone tumors. The principal findings of this study are threefold: first, the technical success rate of ablations performed under analgosedation was high and comparable to procedures conducted under general anesthesia; second, no major sedation-related or procedure-related complications were observed; and third, the implementation of this sedation concept was associated with a substantial increase in procedural throughput within a setting of limited anesthesiology resources.

Percutaneous thermal ablation has become an established component of multimodal oncologic therapy for primary and secondary tumors of the liver as well as for selected renal and osseous lesions [1] [2] [3] [4]. In many European centers, these interventions are still predominantly performed under general anesthesia, requiring the availability of specialized anesthesiology personnel [3]. However, increasing procedural demand, personnel shortages, and financial constraints have led to growing interest in alternative sedation strategies that maintain patient safety while improving procedural flexibility [5] [6].

Analgosedation is well established in interventional radiology and has been successfully applied in a wide range of diagnostic and therapeutic procedures [7] [8] [9]. For thermal ablation, adequate analgesia and patient immobility are essential, as involuntary movement may compromise probe positioning and ablation accuracy [10]. The combination of midazolam and S-ketamine represents a pharmacologically complementary regimen, providing anxiolysis, amnesia, and effective analgesia without relevant respiratory depression when used in appropriate doses [11] [12] [13] [14]. In line with current recommendations, S-ketamine was consistently combined with a benzodiazepine to reduce the risk of emergence phenomena such as hallucinations or agitation [14] [17].

In the present study, sedation depth was intentionally limited to moderate analgosedation (Zalunardo grade II), with preserved spontaneous breathing [15]. This point is critical, as the aim of the applied protocol was not to replicate general anesthesia but to provide sufficient analgesia and anxiolysis for short, painful procedures while maintaining a high safety margin. The two aborted procedures underscore the importance of strict safety thresholds: in one case, an unexpected paradoxical reaction to midazolam occurred, and in the other, adequate analgesia could not be achieved despite repeated S-ketamine administration. In both situations, the decision to terminate the procedure was made early in favor of patient safety.

No major peri- or post-interventional complications were observed in either the analgosedation or the general anesthesia group. Minor complications were rare and comparable between groups. Importantly, no respiratory, cardiovascular, or anaphylactic events related to sedation occurred. These findings are consistent with previous reports demonstrating the safety of ketamine-based sedation protocols when applied within a structured monitoring and emergency framework [9] [10] [15]. Nevertheless, it must be emphasized that radiologist-guided analgosedation requires clearly defined prerequisites. These include thorough pre-procedural risk assessment, continuous monitoring of vital signs, immediate availability of ventilation and suction equipment, and personnel trained in airway management and cardiopulmonary resuscitation. In our institution, these requirements are complemented by the availability of an in-house emergency medical team that can be summoned within minutes.

Analgosedation should not be regarded as a purely technical task but as a structured medical responsibility that requires defined competencies, standardized procedures, and appropriate clinical experience. Formalized training and certification – such as programs offered by CIRSE or DeGIR – provide an essential framework for the safe application of radiologist-guided analgosedation, encompassing pharmacology, patient monitoring, emergency management, and relevant legal considerations. This approach is consistent with national and international recommendations on analgosedation performed by non-anesthesiologists, which emphasize structured training, risk stratification, and clearly defined safety standards [15] [17].

Beyond safety considerations, procedural efficiency is an increasingly relevant outcome parameter. Following the implementation of radiologist-guided analgosedation, the number of ablations performed per month increased markedly in our department, while no additional personnel or structural changes were introduced. Although causality cannot be proven in a retrospective design, this observation suggests that reduced dependency on anesthesiology resources may facilitate more flexible scheduling and improved access to timely oncologic treatment. In addition, mean in-room time was significantly shorter in the analgosedation group, potentially allowing more efficient use of interventional suite capacity.

Patient comfort and acceptance are important aspects that were not systematically assessed in this study. However, the fact that several patients underwent repeat ablations under the same sedation protocol without reluctance may indicate acceptable tolerability. Previous studies comparing ketamine-based regimens with alternative sedation strategies have reported comparable patient satisfaction and effective analgesia [18] [19]. Nevertheless, prospective assessment using standardized patient-reported outcome measures would be desirable.

This study has several limitations. Its retrospective design precludes detailed analysis of continuous vital parameters and standardized assessment of patient satisfaction. Furthermore, cost-effectiveness and interventionalist satisfaction were not formally evaluated. Finally, the results reflect the experience of a single center with a specific organizational and training framework and may not be directly generalizable to all institutions.

In conclusion, radiologist-guided analgosedation using midazolam and S-ketamine represents a feasible and safe complementary approach for percutaneous thermal ablation of selected tumors when performed within a structured safety framework. It should not be regarded as a substitute for anesthesiology expertise but as an additional model that may help optimize procedural capacity and reduce waiting times in settings with limited anesthesia resources. Careful patient selection, adequate training, and comprehensive emergency preparedness remain essential prerequisites for its implementation.

Clinical significance

• Given the limited resources available for anesthesia and the increasing demand for minimally invasive therapeutic procedures, the question of alternative concepts arises.

• At present, there is a lack of scientific research on the feasibility of percutaneous thermal ablation under analgosedation.

• This study demonstrated that percutaneous thermal tumor ablation under analgosedation is an effective method of achieving complete tumor ablation without increasing the rate of complications.

In addition, it was shown that the use of analgosedation with S-ketamine and midazolam could increase procedural number of percutaneous thermal ablation procedures and therefore could reduce waiting time.

Conflict of Interest

The authors declare that they have no conflict of interest.

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Publication History

Received: 13 August 2025

Accepted after revision: 09 January 2026

Article published online:
06 February 2026