Comparison 2. H2 receptor antagonists versus placebo or no prophylaxis.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Clinically important upper GI bleeding	24	2149	Risk Ratio (M‐H, Random, 95% CI)	0.50 [0.36, 0.70]
1.1 Cimetidine vs placebo	10	772	Risk Ratio (M‐H, Random, 95% CI)	0.53 [0.28, 1.02]
1.2 Famotidine vs placebo	1	146	Risk Ratio (M‐H, Random, 95% CI)	2.11 [0.20, 22.79]
1.3 Ranitidine vs placebo	5	446	Risk Ratio (M‐H, Random, 95% CI)	0.36 [0.17, 0.77]
1.4 Cimetidine vs no prophylaxis	3	516	Risk Ratio (M‐H, Random, 95% CI)	0.59 [0.23, 1.48]
1.5 Famotidine vs no prophylaxis	1	50	Risk Ratio (M‐H, Random, 95% CI)	0.3 [0.09, 0.96]
1.6 Ranitidine vs no prophylaxis	4	219	Risk Ratio (M‐H, Random, 95% CI)	0.51 [0.26, 1.00]
2 Nosocomial pneumonia	8	945	Risk Ratio (M‐H, Fixed, 95% CI)	1.12 [0.85, 1.48]
2.1 Cimetidine vs placebo	2	204	Risk Ratio (M‐H, Fixed, 95% CI)	0.34 [0.06, 2.00]
2.2 Famotidine vs placebo	1	146	Risk Ratio (M‐H, Fixed, 95% CI)	1.48 [0.49, 4.45]
2.3 Ranitidine vs placebo	2	277	Risk Ratio (M‐H, Fixed, 95% CI)	0.79 [0.47, 1.31]
2.4 Cimetidine vs no prophylaxis	1	200	Risk Ratio (M‐H, Fixed, 95% CI)	2.17 [0.86, 5.47]
2.5 Ranitidine vs no prophylaxis	2	118	Risk Ratio (M‐H, Fixed, 95% CI)	1.33 [0.93, 1.90]
3 All‐cause mortality in ICU	14	1428	Risk Ratio (M‐H, Fixed, 95% CI)	1.12 [0.88, 1.42]
3.1 Cimetidine vs placebo	4	478	Risk Ratio (M‐H, Fixed, 95% CI)	1.05 [0.66, 1.68]
3.2 Famotidine vs placebo	1	146	Risk Ratio (M‐H, Fixed, 95% CI)	1.32 [0.55, 3.16]
3.3 Ranitidine vs placebo	2	148	Risk Ratio (M‐H, Fixed, 95% CI)	0.69 [0.31, 1.54]
3.4 Cimetidine vs no prophylaxis	2	400	Risk Ratio (M‐H, Fixed, 95% CI)	1.0 [0.61, 1.63]
3.5 Famotidine vs no prophylaxis	1	50	Risk Ratio (M‐H, Fixed, 95% CI)	1.25 [0.59, 2.64]
3.6 Ranitidine vs no prophylaxis	4	206	Risk Ratio (M‐H, Fixed, 95% CI)	1.58 [0.97, 2.58]
4 All‐cause mortality in hospital	4	487	Risk Ratio (M‐H, Fixed, 95% CI)	1.16 [0.79, 1.70]
4.1 Famotidine vs placebo	1	146	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.43, 1.86]
4.2 Ranitidine vs placebo	1	101	Risk Ratio (M‐H, Fixed, 95% CI)	0.35 [0.01, 8.47]
4.3 Cimetidine vs no prophylaxis	1	200	Risk Ratio (M‐H, Fixed, 95% CI)	1.47 [0.88, 2.46]
4.4 Ranitidine vs no prophylaxis	1	40	Risk Ratio (M‐H, Fixed, 95% CI)	0.92 [0.33, 2.53]
5 Duration of ICU stay	2	230	Mean Difference (IV, Fixed, 95% CI)	0.73 [‐0.92, 2.38]
5.1 Famotidine vs placebo	1	146	Mean Difference (IV, Fixed, 95% CI)	1.5 [‐1.93, 4.93]
5.2 Ranitidine vs no prophylaxis	1	84	Mean Difference (IV, Fixed, 95% CI)	0.5 [‐1.38, 2.38]
6 Duration of intubation	2	230	Mean Difference (IV, Fixed, 95% CI)	0.79 [‐0.95, 2.54]
6.1 Famotidine vs placebo	1	146	Mean Difference (IV, Fixed, 95% CI)	1.20 [‐1.86, 4.26]
6.2 Ranitidine vs no prophylaxis	1	84	Mean Difference (IV, Fixed, 95% CI)	0.60 [‐1.52, 2.72]
7 Number of participants requiring blood transfusions	7	655	Risk Ratio (M‐H, Fixed, 95% CI)	0.58 [0.36, 0.95]
7.1 Cimetidine vs placebo	3	107	Risk Ratio (M‐H, Fixed, 95% CI)	0.39 [0.19, 0.79]
7.2 Ranitidine vs placebo	2	148	Risk Ratio (M‐H, Fixed, 95% CI)	1.05 [0.24, 4.60]
7.3 Cimetidine vs no prophylaxis	2	400	Risk Ratio (M‐H, Fixed, 95% CI)	0.77 [0.35, 1.71]
8 Units of blood transfused	2	209	Mean Difference (IV, Fixed, 95% CI)	0.33 [‐0.04, 0.70]
8.1 Cimetidine vs placebo	1	9	Mean Difference (IV, Fixed, 95% CI)	‐4.35 [‐7.35, ‐1.35]
8.2 Cimetidine vs no prophylaxis	1	200	Mean Difference (IV, Fixed, 95% CI)	0.40 [0.03, 0.77]
9 Adverse events of interventions	8		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
9.1 Diarrhoea	2	225	Risk Ratio (M‐H, Fixed, 95% CI)	1.30 [0.57, 2.96]
9.2 Thrombocytopenia	1	200	Risk Ratio (M‐H, Fixed, 95% CI)	3.0 [0.12, 72.77]
9.3 Hypophosphatemia	1	25	Risk Ratio (M‐H, Fixed, 95% CI)	3.75 [0.17, 84.02]
9.4 Mental confusion	5	657	Risk Ratio (M‐H, Fixed, 95% CI)	2.01 [1.10, 3.65]
9.5 Nausea and vomiting	2	287	Risk Ratio (M‐H, Fixed, 95% CI)	0.46 [0.09, 2.35]
9.6 Increased creatinine levels	1	200	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.64, 1.69]
9.7 Erythema	1	70	Risk Ratio (M‐H, Fixed, 95% CI)	3.0 [0.13, 71.22]
9.8 Pancreatitis	1	39	Risk Ratio (M‐H, Fixed, 95% CI)	0.29 [0.01, 6.66]
9.9 Chest infection	1	101	Risk Ratio (M‐H, Fixed, 95% CI)	1.74 [0.92, 3.30]
9.10 Delirium	1	39	Risk Ratio (M‐H, Fixed, 95% CI)	2.59 [0.11, 59.93]
9.11 Hallucinations	1	39	Risk Ratio (M‐H, Fixed, 95% CI)	2.59 [0.11, 59.93]
9.12 Severe bleeding	1	101	Risk Ratio (M‐H, Fixed, 95% CI)	0.35 [0.01, 8.47]