The Effects of a Multiday (10–14 days) Subanesthetic Dose IV Ketamine Infusion in the Treatment of Refractory Chronic Pain

Figures & data

Table 1. Summary table of baseline variables of all 128 admissions.

Patient demographics/characteristics	All 128 admissions		All 52 admissions by patients with opioid use
	N/mean	%/SD	N/mean	%/SD
Total: number of admissions	128		52
Total: number of patients	87		39
Gender
Female	107	83.6%	41	78.8%
Male	21	16.4%	11	21.2%
Age	48.32	11.83	50.44	11.67
Clinical diagnosis
CRPS	48	37.5%	13	25.0%
Back pain	6	4.7%	5	9.6%
Fibromyalgia	48	37.5%	17	32.7%
Headache	7	5.5%	3	5.8%
Peripheral neuropathy	19	14.8%	14	26.9%
Length of stay (days)
10	14	10.9%	4	7.7%
11	2	1.6%	0	0.0%
12	3	2.3%	1	1.9%
14	100	78.1%	41	78.8%
>14	9	7.0%	6	11.5%
Opioid use at time
No	76	59.4%
Yes	52	40.6%
Opioid use at time
Codeine			4	7.7%
Fentanyl			4	7.7%
Fentanyl, hydromorphone			3	5.8%
Fentanyl, morphine			2	3.8%
Hydromorphone			7	13.5%
Methadone			9	17.3%
Methadone, hydromorphone			3	5.8%
Oxycodone			4	7.7%
Tapentadol			5	9.6%
Tapentadol, tramadol			1	1.9%
Tramadol			10	19.2%
Made the follow-up visit
Visit1	118	92.2%	48	92.3%
Visit2	99	77.3%	41	78.8%
Visit3	83	64.8%	35	67.3%
Days from discharge to visit
Visit1	30.42	58.07	34.38	57.44
Visit2	67.44	56.75	61.78	55.60
Visit3	110.69	71.09	95.97	57.40
Maximum dose of ketamine tolerated
Not specified	5	3.9%	2	3.8%
14–19	6	4.7%	2	3.8%
20–24	23	18.0%	11	21.2%
25–29	26	20.3%	11	21.2%
30	68	53.1%	26	50.0%

CRPS: Complex regional pain syndrome.

Table 2. Changes in pain ratings for all patients.

Outcome	Patient group	With no missing data	Level	Discharge	Visit1	Visit2	Visit3
Change in pain rating	All patients	Admit, discharge (n = 77)	1: Decrease ≥30%	56 (72.7%)
			2: Decrease <30%	13 (16.9%)
			3: No change	3 (3.9%)
			4: Worse	5 (6.5%)
		Admit, discharge, visit 1 (n = 34)	1: Decrease ≥30%	30 (88.2%)	25 (73.5%)
			2: Decrease <30%	4 (11.8%)	7 (20.6%)
			3: No change	0 (0.0%)	2 (5.9%)
		Admit, discharge, visit 1, visit 2 (n = 14)	1: Decrease ≥30%	11 (78.6%)	10 (71.4%)	10 (71.4%)
			2: Decrease <30%	3 (21.4%)	3 (21.4%)	3 (21.4%)
			3: No change	0 (0.0%)	1 (7.1%)	0 (0.0%)
			4: Worse	0 (0.0%)	0 (0.0%)	1 (7.1%)
		Admit, discharge, visit 1, visit 2, visit 3 (n = 6)	1: Decrease ≥30%	6 (100.0%)	6 (100.0%)	6 (100.0%)	4 (66.7%)
			2: Decrease <30%	0 (0.0%)	0 (0.0%)	0 (0.0%)	1 (16.7%)
			3: No change	0 (0.0%)	0 (0.0%)	0 (0.0%)	1 (16.7%)
	Opioid users	Admit, discharge (n = 34)	1: Decrease ≥30%	21 (61.8%)
			2: Decrease <30%	9 (26.5%)
			3: No change	2 (5.9%)
			4: Worse	2 (5.9%)
		Admit, discharge, visit 1 (n = 12)	1: Decrease ≥30%	10 (83.3%)	7 (58.3%)
			2: Decrease <30%	2 (16.7%)	5 (41.7%)
			3: No change	0 (0.0%)	0 (0.0%)
		Admit, discharge, visit 1, visit 2 (n = 5)	1: Decrease ≥30%	4 (80.0%)	3 (60.0%)	3 (60.0%)
			2: Decrease <30%	1 (20.0%)	2 (40.0%)	1 (20.0%)
			3: No change	0 (0.0%)	0 (0.0%)	0 (0.0%)
			4: Worse	0 (0.0%)	0 (0.0%)	1 (20.0%)
		Admit, discharge, visit 1, visit 2, visit 3 (n = 3)	1: Decrease ≥30%	3 (100.0%)	3 (100.0%)	3 (100.0%)	1 (33.3%)
			2: Decrease <30%	0 (0.0%)	0 (0.0%)	0 (0.0%)	1 (33.3%)
			3: No change	0 (0.0%)	0 (0.0%)	0 (0.0%)	1 (33.3%)

Figure 1. Morphine milligram equivalents usage over time, excluding methadone.

MME: Morphine milligram equivalents.

Figure 2. Mixed effect piecewise regression model of pain rating scale – CRPS versus non-CRPS.

CRPS: Complex regional pain syndrome.

Figure 3. Mixed effect piecewise regression model of pain rating scale – opioid users versus nonopioid users.

Figure 4. Mixed effect piecewise regression model among opioid users – estimated morphine milligram equivalents.

Data availability statement

If requested, we can share all the data gathered and used in this report for research purposes. Please direct data requests to the corresponding author.