Ketamine with midazolam outperformed fentanyl for image-guided procedures

Design

single-centre randomised clinical trial, radiologist-administered sedation

Population

264 image-guided lung or bone biopsy and abscess drainage procedures in 260 adults, median age 68

Primary outcome

maximum intraprocedural pain on a 0 to 10 numeric rating scale

Effect

mean difference −1.4 points favouring ketamine (95% CI −2.0 to −0.8); pain above 4 in 2.3% versus 17%; desaturation below 90% in 2.3% versus 9.8%

Two hundred and sixty-four image-guided procedures in 260 adults — lung or bone biopsy and abscess drainage, under ultrasound, CT, CT fluoroscopy or combined guidance — were randomised to interventional radiologist-administered fentanyl plus midazolam or ketamine plus midazolam, 132 procedures per arm. The primary outcome was maximum intraprocedural pain on a 0 to 10 scale.

Ketamine won on pain: mean difference −1.4 points (95% CI −2.0 to −0.8; P<0.001), and pain above 4 occurred in 2.3% against 17%, an absolute difference of 14 percentage points (95% CI 8 to 21; P<0.001). It also won on respiratory safety, which is the opposite of what many operators would expect: nadir oxygen saturation was higher by 1.4% (95% CI 0.6 to 2.2; P=0.001), and desaturation below 90% occurred in three procedures (2.3%) against 13 (9.8%), an absolute difference of 7.6 percentage points (P=0.02). Sedation was deeper and intraprocedural systolic pressure higher. The cost was hallucinations, 11.4% against 3.8% (P=0.03), and yet overall comfort, reduced recall and perceived adequacy of sedation all favoured ketamine. Complication rates did not differ.

This is directly actionable for anyone running a biopsy list under radiologist-administered sedation. An opioid-benzodiazepine combination is the default largely by habit, and the trial says a ketamine-based regimen hurts less and desaturates less in the same hands. The hypoxaemia difference is the finding most likely to change a department's protocol, because desaturation is what turns a routine biopsy into an event.

Two practical conditions come with it. Hallucinations at one in nine need warning beforehand and a quiet recovery area afterwards, and the rise in systolic pressure needs thought in patients where that matters. This was also a single academic centre with operators who chose to run the trial; a unit adopting it should train for the emergence phenomena rather than discovering them.

• Review your procedural sedation protocol for lung and bone biopsy and abscess drainage specifically — that is what was studied
• Warn patients about hallucinations and dissociative sensations before ketamine, and plan a quiet recovery space
• Reconsider the assumption that ketamine is the riskier respiratory choice; desaturation below 90% was less frequent here
• Check blood pressure trajectory in patients where a rise in systolic pressure matters
• Train the whole list team before switching, rather than changing the drug and leaving the recovery staff to adapt

The statistics, in plain English

A 1.4-point mean reduction on a 0 to 10 pain scale is around the smallest difference patients notice, so the more informative figure is the proportion with pain above 4: 2.3% against 17%, which is a sevenfold difference on a threshold that matters. The desaturation result rests on 16 events in total, so its absolute difference interval is wide (1.9 to 13.3 percentage points) — the direction is trustworthy, the size less so. Hallucinations at 11.4% against 3.8% is a real difference and the number to quote in consent.

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