Safety and effectiveness of neuromuscular electrical stimulation in cardiac surgery: A systematic review

Table 3 Population, intervention, comparison, outcomes, and study design of each study included in the systematic review

Ref.	Interventions by group	Frequency	Session duration	Intervention Duration	Outcomes	Main results	Adverse events
Fischer et al[19]	NMES: biphasic rectangular pulses at 66 Hz, pulse duration 0.4 ms, duty cycle 3.5 s on and 4.5 s off to quadriceps muscle bilaterally. CG: stimulator electrodes were applied but no electricity was delivered	2 times/d for 7 d/wk	30 min	From POD 1 until ICU exit or POD 14	Muscle layer thickness, Muscle strength; Functional capacity	No significant effect on MLT. ↑ 4.5 times in recovering muscle strength to NMES group during ICU stay. Positive correlation between change in MLT and cumulative fluid balance (r = 0.43, P = 0.01) the first 3 PODs. No significant effect on functional ability	5 patients in the NMES group mentioned a feeling of discomfort
Schardong et al[20]	1FES: symmetric biphasic rectangular pulses at 15 Hz, pulse duration 0.5 ms, duty cycle 5 s on and 10 s off to vastus medialis and lateralis muscle bilaterally. CG: Stimulator electrodes were applied but no electricity was delivered	2 times/wk	40 min	8 wk	Functional capacity; Muscle strength; Muscle endurance; Muscle mass	↑ Distance to 6MWT in the FES group by 11.0% (49.6 m, 95%CI: 15.9-83.3) and in the CG by 10.4% (41.5 m, 95%CI: 7.8-75.2) with no significant between-groups. ↑ muscle strength (7.2 kg, 95%CI: 0.2-14.2). ↑ Muscle endurance (2.2 repetitions, 95%CI: 1.0-3.4)	No complications
Kitamura et al[21]	NMES: Symmetric biphasic square pulses, duty cycle 0.4 s on and 0.6 s off, 10 pulse trains (10 s) with 30 s intervals to quadriceps femoris and triceps surae muscle bilaterally. Usual postoperative rehabilitation program. CG: Usual postoperative rehabilitation program	1 time/d	30 min	3 d before surgery and from POD 1 to POD 5 (8 sessions)	The mean concentration of 3-MH/Cre; Physical function; Walking speed; Grip strength	No significant difference in the mean 3-MH/Cre from POD 1 to POD 6 between groups (225.3 [204.0-248.3] μmol/g vs 227.3 [206.3-259.9] μmol/g, P = 0.531). No significant difference in the KEIS on POD 7 between groups (0.44 ± 0.13 kgf/kg vs 0.41 ± 0.12 kgf/kg, P = 0.149. No significant difference in walking speed between groups (1.04 ± 0.24 m/s vs 0.99 ± 0.23 m/s, P = 0.294). No significant difference in grip strength between groups (29.1 ± 10.5 kg vs 26.9 ± 8.7 kg, P = 0.213)	1 patient mentioned muscle soreness
Cerqueira et al[22]	NMES: Stimulation at 50 Hz, duration 400 ms duty cycle 3 s on and 9 s off, to quadriceps and gastrocnemius muscle bilaterally. Regular physiotherapy care. CG: Usual physiotherapy care twice a day	2 times/d	60 min	from POD 1 to POD 5	Ambulation ability; Muscle strength; Functional independence; Quality of life	No significant difference in distance walked (95%CI: -64.87 to 65.97) and walking speed (95%CI: -0.55 to 0.57) between groups. No significant difference in muscle strength in the upper- limb, lower limb, and total MRC values, functional independence, and quality of life between groups	2 patients reported hypotension, and 1 patient complained of pain
Cerqueira et al[23]	NMES: Stimulation at 50 Hz, duration 200 ms duty cycle 3 s on and 9 s off, to quadriceps and gastrocnemius muscle bilaterally. Regular physiotherapy care. CG: stimulator electrodes were applied but no electricity was delivered	Once during the first 48 h of ICU stay	60 min	60 min	Hemodynamic responses; Respiratory responses	No difference in heart rate, systolic blood pressure, diastolic blood pressure, mean blood pressure respiratory rate, and oxygen saturation between groups	No complications
Sumin et al[24]	NMES: biphasic rectangular pulses at 45 Hz, duty cycle 12 s on and 5 s off to quadriceps muscle bilaterally. CG: Usual postoperative rehabilitation program	1 time/d	90 min	from POD 3 to exit the hospital (12 sessions or more)	Knee extensors strength; Handgrip strength; Knee flexor strength CSA of quadriceps femoris	↑ Knee extensors strength in the NMES group [28.1 (23.8; 36.2) kg on the right and 27.45 (22.3; 33.1) kg on the left] vs CG [22.3 (20.1; 27.1) and 22.5 (20.1; 25.9) kg, respectively; P < 0.001]. No difference in handgrip strength, knee flexor strength, quadriceps CSA, and 6MWT at discharge between groups	Non mentioned
Rengo et al[25]	2NMES: biphasic rectangular pulses at 25 Hz, pulse duration 400 ms, duty cycle 10 s on and 30 s off to quadriceps muscle bilaterally. CG: no intervention	1 times/d for 5 d/wk	45 min	4 wk	Physical function Mental and physical health	From discharge to 4-wk post-discharge: No significant interaction effect for total SPPB score (P = 0.11; ηp2 = 0.073; CG: 2.89 ± 0.50 vs NMES: 4.11 ± 0.54 units). Time effects for 6MWT distance (P < 0.01; ηp2 = 0.207; CG: 194 ± 18 vs NMES: 267 ± 16 m) and 6MWT power output (P = 0.01; ηp2 = 0.168; CG: 0.4 ± 0.1 vs NMES: 0.6 ± 0.1 W; P = 0.01)	No complications
Cerqueira et al[26]	NMES: Stimulation at 50 Hz, duration 400 ms duty cycle 3 s on and 9 s off, to rectus femoris and gastrocnemius muscle bilaterally. Regular physiotherapy care twice a day. CG: Usual physiotherapy care twice a day	2 times/d	60 min	From POD 1 to POD 5	Distance walked; Gait speed; Lactate levels Muscle strength Electromyographic activity of the rectus femoris; Functional Independence Measure	No significant difference in the distance walked (P = 0.650) between NMES group (239.06 ± 88.55) and CG (254.43 ± 116.67) as well as gait speed (P = 0.363), lactate levels (P = 0.302), knee extensor strength (P = 0.117), handgrip strength (P = 0.882), global muscle strength (P = 0.104), electromyographic activity (P = 0.179) and Functional Independence Measure (P = 0.059)	No complications
Takino et al[27]	NMES: Biphasic symmetric square pulses at 20 and 200 Hz, duty cycle 0.4 s on and 0.6 s off to vastus lateralis, vastus medialis and triceps surae muscle bilaterally. Standard post- surgical rehabilitation. CG: Standard post- surgical rehabilitation.	1 time/d	60 min	from POD 1 to POD 7	% change in isometric knee strength; % change in usual and maximum walking speed; % change in grip strength	↓ %ΔIKES in the NMES than CG [NMES: Mean -2%, 95% confidence interval (CI) -6 to 1; CG: -13%, 95% CI -17 to -9, P < 0.001]. ↓ %ΔMWS (P = 0.04). ↓ %ΔUWS and %ΔGS in the NMES compare to CG but not statistically significant	Non mentioned
Sumin et al[28]	NMES: rectangular pulses at 45 Hz, duty cycle 12 s on and 5 s off to quadriceps muscle bilaterally. Standard preoperative rehabilitation program; CG: Standard preoperative rehabilitation program	1 time/d	90 min	from the 2nd day of hospital stay until the day before surgery (7–10 sessions)	Exercise capacity; Muscle strength	↑ in KES, KFS, and 6MWT distance (all P < 0.001) in the NMES group compared to the CG. Slight ↑ in HS to the NMES group and slight ↓ to the CG but not statistically significant (P = 0.054 on the right hand and P = 0.062 on the left)	No complications

¹Patients were discharged from hospital and submitted to phase I of cardiac rehabilitation.

²Home-based intervention after hospital discharge.

CG: Control group; CSA: Cross-sectional area; FES: Functional electrical stimulation; ICU: Intensive care unit; KEIS: Knee extensor isometric strength; MLT: Muscle layer thickness; NMES: Neuromuscular electrical stimulation POD: Post operative day; SPPB: Short physical performance battery; 3-MH/Cre: 3-methylhistidine concentration corrected for urinary creatinine content; 6MWT: Six minutes walking test; KFS: Knee flexor strength; KES: Knee extensor strength; NA: Not available.