Incidence, characteristics and risk factors for alveolar recruitment maneuver-related hypotension in patients undergoing laparoscopic colorectal cancer resection

Table 1 The occurrence of alveolar recruitment maneuver-related hypotension

ARM-related hypotension1	MAP < 60 mmHg2	MAP ≤ 55 mmHg
Patients having hypotension, n (%)	34 (24.3)	17 (12.1)
Patients having hypotension ≥ two times, n	3	2
ARMs with hypotension/total ARMs, No. (%)	37/1027 (3.61)	19/1027 (1.85)
ARM1 or ARMlast with hypotension, No.	27	12
Recovery without vasopressor, No.	27	NA3
ARMs under nonpneumoperitoneum conditions	33/349 (9.46)4	16/349 (4.58)
With hypotension/total ARMs, No. (%)
ARM1 with hypotension, No. (%)	18/135 (13.3)5,6	9/135 (6.7)
ARMlast with hypotension, No. (%)	9/134 (6.7)7	3/134 (2.2)

¹Hypotension occurred during an alveolar recruitment maneuver (ARM) or within 5 min after an ARM.

²Primary endpoint: A mean arterial pressure (MAP) < 60 mmHg during an ARM or within 5 min after an ARM.

³NA: No analysis because vasopressors must be given according to the study protocol when MAP ≤ 55 mmHg.

⁴P < 0.01 compared with ARMs under pneumoperitoneum conditions (4 of 678, 0.59%).

⁵P < 0.01 compared with non-ARM₁ points (19 of 892, 2.13%).

⁶Five participants did not receive ARM₁ because of a MAP ≤ 65 mmHg.

⁷Six participants did not receive ARM_last because they met the intraoperative exclusion criteria.

Data are given as counts or counts (proportion). MAP: Mean arterial pressure; ARM: Alveolar recruitment maneuver; ARM₁: The first ARM; ARM_last: The last ARM; bpm: Beats per minute; NA: Not available.

Table 2 Univariate analysis of the associations between baseline characteristics and alveolar recruitment maneuver-related hypotension

	ARM-related hypotension		P value
	Yes, n = 34	No, n = 106
Male	24	78	0.83
Age (yr)	71.7 ± 6.4	69.1 ± 5.5	< 0.01
Age ≥ 74 yr	15	22	< 0.01
Body weight (kg)	60.8 ± 8.8	62.5 ± 9.6	0.36
Body mass index (kg/m2)	22.54 ± 2.77	23.18 ± 2.63	0.22
Hemoglobin (g/L)	116.1 ± 23.4	121.5 ± 21.5	0.21
White blood cells (× 109/L)	6.84 ± 2.25	6.34 ± 1.94	0.20
C-reaction protein (mg/L)	3.50 (1.39, 7.98)	2.84 (1.02, 6.78)	0.31
Albumin (g/L)	38.4 ± 3.6	39.4 ± 4.0	0.16
SpO2 (%)	96 (96, 97)	97 (96, 97)	0.07
SpO2 (< 96/≥ 96)	8/26	14/92	0.18
Mean arterial pressure (mmHg)	89 ± 8	91 ± 7	0.10
ASA physical status (II/III)	24/10	86/20	0.23
Cardiocerebrovascular events	4	11	0.76
Chemotherapy	5	14	0.78
Hypertension	14	42	> 0.99
Body weight loss ≥ 10%	10	24	0.49
Diabetes mellitus	3	17	0.40

Continuous data are reported as the mean ± SD or median (25^th and 75^th percentile), and categorical data are given as counts. Alveolar recruitment maneuver (ARM)-related hypotension: Mean arterial pressure < 60 mmHg during an ARM or within 5 min after an ARM. ARM: Alveolar recruitment maneuver; S_pO₂: Saturation of peripheral oxygen; ASA: American Society of Anesthesiologists.

Table 3 Univariate analysis of the associations between intraoperative variables and alveolar recruitment maneuver-related hypotension

	ARM-related hypotension		P value
	Yes, n = 34	No, n = 106
Non-PPT ventilation ≥ 90 min	9	17	0.31
Duration of ventilation (min)	233 ± 67	229 ± 84	0.76
Amount of infusion (mL)	3414 ± 799	3181 ± 611	0.13
Recruitment maneuver (times)	7 (6, 8)	7 (5, 8)	0.88
Prefilling fluids before anesthesia (mL)	678 ± 140	696 ± 144	0.52
Blood loss ≥ 150 mL	12	15	0.01
Trendelenburg position	25	79	0.82
Vt at T1 < 7 mL/kg of PBW	8	20	0.62
Vt at T2 < 7 mL/kg of PBW	21	51	0.24
PIP at T1 (cm H2O)	17 ± 2	17 ± 2	> 0.99
PIP at T2 (cm H2O)	24 ± 3	25 ± 2	0.076
PIP at T2 < 24 cm H2O	15	23	0.02
Respiratory rate at T1 (bpm)	12 (12, 12)	12 (12, 12)	0.97
Respiratory rate at T2 (bpm)	17 (16, 18)	16 (15, 18)	0.15
Driving pressure at T1 (cm H2O)	6 ± 2	6 ± 2	0.94
Driving pressure at T2 (cm H2O)	13 ± 2	13 ± 2	0.14
Cdyn at T1 (mL/cm H2O)	48 ± 9	51 ± 14	0.38
Cdyn at T2 (mL/cm H2O)	24 ± 5	24 ± 5	0.95
Urine output < 1.2 mL/kg/h	7	23	0.82
Hemoglobin at T2 (g/L)	97 ± 20	103 ± 18	0.10
lactic acid at T2 (mmol/L)	0.66 ± 0.18	0.69 ± 0.23	0.58

Continuous data are reported as the mean ± SD or median (25^th, 75^th percentile), and categorical data are given as counts. Alveolar recruitment maneuver (ARM)-related hypotension: Mean arterial pressure < 60 mmHg during an ARM or within 5 min after an ARM. PPT: Pneumoperitoneum; ARM: Alveolar recruitment maneuver; PBW: Predicted body weight; T₁: Immediately before induction of pneumoperitoneum; T₂: 0.5 h after induction of pneumoperitoneum; PIP: Peak inspiratory pressure; bpm: Breaths per minute; C_dyn: Dynamic compliance; V_t: Tidal volume.

Table 4 Multivariate analysis: Adjusted risk factors for alveolar recruitment maneuver-related hypotension

Risk factors	OR (95%CI)	P value
Age < 74 yr	1 (Reference)
Age ≥ 74 yr	2.97 (1.24, 7.09)	0.014
Intraoperative blood loss < 150 mL	1 (Reference)
Intraoperative blood loss ≥ 150 mL	2.88 (1.13, 7.30)	0.012
PIP at T2 ≥ 24 cm H2O	1 (Reference)
PIP at T2 < 24 cm H2O	3.06 (1.28, 7.31)	0.026

Alveolar recruitment maneuver (ARM)-related hypotension: Mean arterial pressure < 60 mmHg during an ARM or within 5 min after an ARM. Three different models (A, B, and C) were used to identify risk factors, and all models identified the above three risk factors. Here, we list the results of model C. Model A includes ten variables (six variables with a P value < 0.1 in univariate analysis and four variables considered clinically relevant) using forward conditional stepwise variable elimination. Model B included six variables (three risk factors in model A, American Society of Anesthesiologists physical status, the number of ARMs and the amount of loading fluids before anesthesia) using an enter method. Model C included five variables (three risk factors in model A, number of ARMs and number of prefilling fluids before anesthesia) using backward likelihood ratio stepwise variable elimination. T₂: 0.5 h after induction of pneumoperitoneum; OR: Odds ratio; CI: Confidence interval; ARM: Alveolar recruitment maneuver; PIP: Peak inspiratory pressure.