Table 2.

Summary of the included studies

First author, year, design	N patients Median Age (range)	Inclusion criteria	Ketamine dose(s) Comparison dose	Outcomes studied by the authors	Main results of each study
Esmailian M, 2018; RCT	N = 92 48 years (34–62)	-	- K: bolus 0.3 mg/kg (16.3%), 0.4 mg/kg (15.2%), and 0.5 mg/kg (17.4%) - Placebo	PEFR before and 1 h after treatment	- PEFR baseline K0.3: 346 ± 85, P: 336 ± 101 (p = 0.60) - PEFR 1 h after K0.3: 416 ± 76, P: 352 ± 101 (p = 0.001) No side effects reported
Allen JY, 2005; RCT	N = 68 6 years (2–10)	PIS > 8	- K: bolus 0.2 mg/kg + infusion 0.5 mg/kg/h (2 h) - Placebo	PIS at 0, 30, 60, 90, and 120 min No side effects reported	- PIS baseline K: 10 ± 1, P: 10 ± 1 (MD 0.2; 95%CI [− 0.5;0.8]) - PIS at 2 h K: 3 ± 2, P: 4 ± 1 (MD 0.4; 95%CI [− 0.4;1.3])
Tiwari A, 2016; RCT	N = 48 48 months (16–144)	PRAM ≥ 5 after 2 h of standard therapy	- K: bolus 0.5 mg/kg (20 min) + infusion 0.6 mg/kg/h (3 h) - Aminophylline: 5 mg/kg bolus (20 min) + infusion 0.9 mg/kg/h (3 h)	ΔPRAM in the first 24 h, Hypertension, Tachycardia	ΔPRAM score in the first 24 h K: 4.00 ± 1.25, A: 4.17 ± 1.68 (p = 0.70) No side effects reported
Nedel W, 2020; RCT	N = 45 65 years (51–79)	- Adults intubated for acute bronchospasm -Rsmax ≥ 12 cmH2O/L/s	- K: bolus 2 mg/kg + infusion 2 mg/kg/h - Fentanyl: bolus 1 mcg/kg + infusion of 1 mcg/kg/h	Rsmax, ΔPEEPi, ΔCdyn at 3 h and 24 h after treatment	- Rsmax at 3 h: K: 0 ± 6, F: –3 ± 8, p = 0.16 - Rsmax at 24 h: K: –3 ± 17, F: –3 ± 14, p = 0.73 - ΔPEEPi at 3 h: K: 0 (95%CI –1;1), F: –0.5 (–8;0), p = 0.77 - ΔPEEPi at 24 h: K: –1 (95%CI –3;1), F: –0.5 (–5;2), p = 0.72 - ΔCdyn at 3 h: K: 0 (95%CI –2;2), F: 0 (–2;3), p = 0.85 - ΔCdyn at 3 h: K: 1 (95%CI –6;3), F: 0.5 (–11;3), p = 0.35 No side effects reported
Howton JC, 1996; RCT	N = 44 33 years (26–40)	-	- K: bolus 0.1 mg/kg + infusion at 0.5 mg/kg/h - Placebo	Respiratory rate, Borg Score, Peak flow, FEV1 before and after treatment	- RR before vs after K: 29 ± 7 vs 24 ± 4; P: 30 ± 10 vs 24 ± 6 - Borg Score before vs after K: 6 ± 2 vs 3 ± 1; P: 6 ± 3 vs 3 ± 2 - Peak Flow before vs after K: 139 ± 53 vs 158 ± 48, P: 124 ± 49 vs 163 ± 91 - FEV1 before vs after K: 0.7 ± 0.3 vs 0.9 ± 0.3; P: 0.6 ± 0.4 vs 1.0 ± 0.6 - Adverse reactions K: 17.4% (95%CI 5;39), P: 4.8% (12;24). All the above results were not significant
Petrillo TM, 2001; Prospective	N = 10 8 years (5–16)	CAS > 12	- K: bolus 1 mg/kg + infusion 0.75 mg/kg/h (1 h)	CAS and PEFR before K bolus, 10 min after K bolus, and 1 h after infusion	- CAS baseline 14 (8–21). 10 min after bolus 10 (4–12), 1 h after infusion 9 (4–12). Both results p < 0.001 - PEFR baseline 16 ± 10 (0–46) 10 min after bolus 47 ± 14 (0–76). 1 h after infusion: 69 ± 8 (53–95). Both results p < 0.05 Hallucinations n = 2, hypertension n = 1, diffuse skin flushing n = 1
Heshmati F, 2003; Prospective	N = 11 30 years (15–40)	-	- K: bolus 1 mg/kg + infusion 1 mg/kg/h (2 h)	Ppeak, PaCO2, PaO2 before K bolus, 15 min after bolus and 2 h after infusion	- Ppeak baseline 75 ± 4. 15 min after bolus 50 ± 5. 2 h after infusion 40 ± 5. Both results p < 0.005 - PaCO2 baseline 71 ± 3. 15 min after bolus 64 ± 4. 2 h after infusion 45 ± 4. Both results p < 0.005 - PaO2 baseline 63 ± 4. 15 min after bolus 75 ± 4. 2 h after infusion 92 ± 4. Both results p < 0.005 No side effects reported

K ketamine, CAS clinical asthma score, Cdyn dynamic compliance, CI confidence interval, FEV1 forced expiratory volume in 1 s, MD mean difference, MV mechanical ventilation, PEEPi positive end expiratory pressure intrinsic, PEFR peak expiratory flow rate, Ppeak pressure peak, PIS pulmonary index score, PRAM pediatric respiratory assessment measure, RR, respiratory rate, Rsmax airway resistance, RCT randomized controlled trial