Table 2.
Intraoperative characteristics. Data represent median (Q1–Q3) of the median values of each subject during surgery. ‡P-values are calculated from the Kruskal–Wallis test (for continuous variables) or Fisher's exact test (extended). For post hoc comparisons – we consider P≤0.01667 (=0.05/3) statistically significant – allowing for multiple comparisons. However, we also indicate for completeness all two-group comparisons where 0.01667<P<0.05 as these would be considered significant if we had not adjusted for multiple comparisons. ∗P-value 0.01667<P<0.05 compared with control; ˆP-value 0.01667<P<0.05 PEEPPtp_eevs PEEPmaxCrs; ∗∗P≤0.01667 compared with control; ˆˆP≤0.01667 PEEPPtp_eevs PEEPmaxCrs. aPes values shown correspond to actual Pes measurements (absolute Pes levels). bAlbumin was the only colloid administered to any study subject. cIncludes only patients receiving any volume of albumin. PBW, predicted body weight.
| Variables | Control (n=13) | PEEPmaxCrs (n=16) | PEEPPtp_ee (n=8) | P-value‡ |
|---|---|---|---|---|
| Respiratory variables | ||||
| Driving pressure (ΔP) (cm H2O) (primary outcome) | 12.0 (10.0–15.0) | 8.0 (7.0–10.0)∗∗ | 9.0 (7.8–10.1)∗ | 0.011 |
| Respiratory system static compliance (Crs) (ml/cm H2O) | 39.0 (32.9–43.4) | 47.7 (43.2–68.8)∗∗ | 49.0 (44.6–58.7)∗∗ | 0.010 |
| Tidal volume (VT) (ml/kg PBW) | 6.7 (6.6–7.1) | 7.1 (6.6–7.5) | 6.9 (6.5–7.3) | 0.810 |
| Respiratory rate (RR) (bpm) | 10.0 (10.0–12.0) | 10.0 (10.0–12.0) | 12.5 (11.0–13.5) | 0.149 |
| Peak inspiratory pressure (PIP) (cm H2O) | 18.0 (13.0–20.0) | 21.0 (18.0–26.0)∗ | 22.5 (21.5–27.0)∗∗ | 0.007 |
| Plateau pressure (Pplat) (cm H2O) | 14.7 (10.2–17.0) | 17.3 (14.0–24.0)∗ | 20.1 (18.0–23.5)∗∗ | 0.006 |
| PEEP (cm H2O) | 2.0 (0.0–2.0) | 10.0 (6.5–15.0)∗∗ | 11.0 (9.5–14.0)∗∗ | <0.001 |
| PEEP coefficient of variation (CVPEEP) | 0.00 (0.00–0.00) | 0.25 (0.17–0.40)∗∗ | 0.17 (0.14–0.23)∗∗ | <0.001 |
| End-expiratory oesophageal pressure (Pes_ee) (cm H2O)a | 9.5 (6.0–14.8) | 7.8 (5.6–10.7) | 9.5 (8.8–12.3) | 0.269 |
| End-expiratory transpulmonary pressure (Ptp_ee) (cm H2O) | -8.3 (-13.0–-4.0) | 2.0 (-0.7–4.5)∗∗ | 1.0 (1.0–2.3)∗∗ | <0.001 |
| Inspired fraction of oxygen (FiO2) (%) | 40.0 (40.0–49.0) | 40.0 (40.0–45.5) | 43.0 (40.0–51.0) | 0.821 |
| Peripheral saturation of oxyhaemoglobin (SpO2) (%) | 98 (95–100) | 99 (98.5–100) | 99 (97.5–99.5) | 0.353 |
| Exhaled end-tidal partial pressure of CO2 PETCO2 (mmHg) | 35.0 (34.0–37.0) | 36.5 (33.5–39.0) | 38.0 (37.0–39.0)∗∗ | 0.048 |
| Other vital signs | ||||
| Temperature (°C) | 35.7 (35.5–36.2) | 35.8 (35.2–36.8) | 36.2 (35.8–36.6) | 0.483 |
| Heart rate (beats min−1) | 64 (62–66) | 70 (67–79)∗∗ | 74 (71–80)∗∗ | 0.007 |
| Mean arterial blood pressure (mmHg) | 84 (78–85) | 80 (75–84) | 82 (78–82) | 0.535 |
| Intraoperative fluid management | ||||
| Crystalloid volume (ml kg−1 h−1) | 8.5 (6.0–9.3) | 6.9 (6.1–10.6) | 5.7 (4.9–8.9) | 0.425 |
| Albumin n (%)b | 4 (31) | 5 (31) | 3 (38) | 1.000 |
| Albumin volume (ml kg−1 h−1) | 1.3 (1.2–1.7) | 2.5 (2.4–3.0)∗ | 2.1 (1.4–2.2) | 0.024 |
| Any blood product n (%) | 0.216 | |||
| Packed red blood cells | 0 (0) | 0 (0) | 0 (0) | |
| Fresh frozen plasma | 0 (0) | 0 (0) | 1 (12) | |
| Platelets | 0 (0) | 0 (0) | 0 (0) | |
| Estimated blood loss (ml) | 100 (25–750) | 188 (113–525) | 575 (138–775) | 0.407 |
| Urine output (ml kg−1 h−1) | 1.0 (0.6–1.7) | 0.9 (0.6–1.2) | 0.8 (0.5–1.7) | 0.744 |
| Vasoactive medications | ||||
| Vasoactive medications n (%) | 12 (92) | 16 (100) | 8 (100) | 0.387 |
| Phenylephrine | 9 (69) | 15 (94) | 8 (100) | 0.071 |
| Ephedrine | 9 (69) | 8 (50) | 4 (40) | 0.530 |
| Vasopressin | 2 (15) | 2 (13) | 1 (13) | 0.970 |
| Total vasoactive doses | ||||
| Phenylephrine (μg) | 850 (0–5060) | 1250 (630–3559) | 6922 (3113–20 548) | 0.064 |
| Ephedrine (mg) | 15 (0–30) | 5 (0–17.5) | 2.5 (0–17.5) | 0.455 |
| Vasopressin units | 0 (0–0) | 0 (0–0) | 0 (0–0) | 0.963 |