TABLE 3.
Summary of the Surgical Characteristics of the Study Population
| Unit/category | Patients with data at V0-V2 n=99 | Patients with data at V0-V3 n=57 | Patients with data at V0-V4 n=41 | Statistical difference between visits P | ||
|---|---|---|---|---|---|---|
| V0-V2 vs. V0-V3 | V0-V2 vs. V0-V4 | |||||
| Surgical time | Minutes | 192.7±110.7 | 169.6±94.5 | 171.4±84.0 | 0.20 | 0.22 |
| Surgical type | Lumbar fusion | 47 | 30 | 23 | 0.48 | 0.93 |
| Lumbar decompression and fusion | 32 | 16 | 10 | — | — | |
| Cervical decompression and fusion (ventral) | 8 | 6 | 4 | — | — | |
| Cervical decompression and fusion | 4 | 2 | 1 | — | — | |
| Kyphoplasty | 2 | 1 | 1 | — | — | |
| Other | 6 | 2 | 2 | — | — | |
| Surgical complexity | Simple | 42 | 26 | 18 | 0.41 | 0.89 |
| Intermediate | 41 | 23 | 18 | — | — | |
| Complex | 16 | 8 | 3 | — | — | |
| Surgical levels | — | 1.8±1.2 | 2.4±1.2 | 1.7±1.0 | <0.01 | 0.43 |
| Blood volume in | Milliliter | 74±285 | 57±287 | 3±22 | 0.74 | 0.10 |
| Blood volume out | Milliliter | 397±482 | 289±406 | 346±482 | 0.24 | 0.59 |
| Fluid in | Milliliter | 2572±1363 | 2147±1087 | 2282±1097 | 0.06 | 0.19 |
| Fluid out | Milliliter | 231±364 | 159±293 | 126±231 | 0.32 | 0.14 |
| Fluid balance | Milliliter | 2018±802 | 1756±675 | 1813±406 | 0.06 | 0.23 |
In line with Table 2, we again explored whether patient samples differed at visits. There were no significant differences between the samples except for more extensive surgery in patients that presented at the three-month outpatient follow-up, i.e. with data from V0-V3, as compared with all initially participating patients, i.e. from V0-V2. Although we did not expect such a substantial drop-out rate, it is plausible that patients with more extensive surgery were more likely to present to their follow-up appointment.