Table 3.
Cerebral haemodynamic variables at baseline and during infusion of sodium nitroprusside (SNP) without and with ‘correction’ for changes in arterial CO2 tension by the determined CO2 reactivity
| Baseline (n = 19) | SNP low rate (n = 19) | SNP high rate (n = 16) | P value | |
|---|---|---|---|---|
| Without ‘correction’ for changes in arterial CO2 tension | ||||
| ICA TAVMAX (cm s–1) | 47 ± 9 | 47 ± 10 | 48 ± 12 | 0.9823 |
| ICA diameter (mm) | 5.5 ± 0.5 | 5.8 ± 0.5* | 5.6 ± 0.3 | 0.0018 |
| ICA blood flow (ml min–1) | 336 ± 66 | 365 ± 69* | 349 ± 82 | 0.0417 |
| ICA conductance (ml min–1 mmHg–1) | 4.0 ± 0.8 | 5.3 ± 0.8* | 6.1 ± 1.3* † | < 0.0001 |
| ICA shear rate (s–1) | 347 ± 87 | 332 ± 90 | 348 ± 94 | 0.4222 |
| VA TAVMAX (cm s–1) | 29 ± 6 | 25 ± 5* | 26 ± 8* | 0.0017 |
| VA diameter (mm) | 4.0 ± 0.4 | 4.3 ± 0.6* | 4.3 ± 0.6* | 0.0002 |
| VA blood flow (ml min–1) | 114 ± 34 | 112 ± 38 | 110 ± 42 | 0.7963 |
| VA conductance (ml min–1 mmHg–1) | 1.4 ± 0.4 | 1.6 ± 0.6* | 1.9 ± 0.7* † | < 0.0001 |
| VA shear rate (s–1) | 293 ± 64 | 242 ± 52* | 247 ± 95* | 0.0001 |
| CBF (ml min–1) | 899 ± 135 | 962 ± 127 | 918 ± 197 | 0.157 |
| CBF conductance (ml min–1 mmHg–1) | 10.8 ± 1.7 | 14.1 ± 2.3* | 15.9 ± 3.1* † | < 0.0001 |
| MCA mean blood velocity (cm s–1) | 69 ± 16 | 59 ± 14* | 52 ± 14* † | < 0.0001 |
| MCA conductance index (cm s–1 mmHg–1) | 0.82 ± 0.17 | 0.86 ± 0.18 | 0.91 ± 0.23* † | 0.0014 |
| With ‘correction’ for changes in arterial CO2 tension | ||||
| ICA blood flow (ml min–1) | 336 ± 66 | 388 ± 74* | 382 ± 78* | < 0.0001 |
| ICA conductance (ml min–1 mmHg–1) | 4.0 ± 0.8 | 5.7 ± 1.2* | 6.6 ± 1.2* † | < 0.0001 |
| VA blood flow (ml min–1) | 114 ± 34 | 119 ± 40 | 125 ± 46 | 0.2608 |
| VA conductance (ml min–1 mmHg–1) | 1.4 ± 0.4 | 1.7 ± 0.6* | 2.2 ± 0.8* † | < 0.0001 |
| CBF (ml min–1) | 899 ± 135 | 1023 ± 131* | 1013 ± 183* | 0.0002 |
| CBF conductance (ml min–1 mmHg–1) | 10.8 ± 1.7 | 15.0 ± 2.5* | 17.6 ± 2.8* † | < 0.0001 |
| MCA mean blood velocity (cm s–1) | 69 ± 16 | 61 ± 15* | 56 ± 15* † | < 0.0001 |
| MCA conductance index (cm s–1 mmHg–1) | 0.82 ± 0.17 | 0.89 ± 0.19* | 0.98 ± 0.27* † | < 0.0001 |
ICA, internal carotid artery; TAVMAX, time averaged maximum blood velocity; VA, vertebral artery; CBF, cerebral blood flow; MCA, middle cerebral artery. n = 18 for ICA and CBF at the low SNP rate. Values are means ± SD. P values represent the overall effect as estimated by a repeated measure mixed model. * P < 0.05 vs. baseline. † P < 0.05 for low vs. high SNP infusion rate.