Subarachnoid pressures and cardiorespiratory parameters during cisternal myelography in isoflurane anaesthetized dogs

Abstract Objective To measure subarachnoid pressures, systemic circulatory and respiratory effects, and to calculate cerebral perfusion pressure during cisternal myelography. Study design Prospective clinical study. Animals Forty‐three client owned dogs with clinical signs of spinal disease, weighing 6–56 kg. Methods Dogs were premedicated with butorphanol and diazepam intravenously (IV) and anaesthesia was induced with propofol and maintained with isoflurane vaporized in oxygen. Ventilation was spontaneous. Heart and respiratory rates, invasive mean arterial blood pressure (MAP), end tidal carbon dioxide and isoflurane concentration were measured continuously. Initial subarachnoid pressure (SaP 0 ) was measured in the cisterna magna with a needle pressure gauge. Iohexol 0.3 mL kg −1 was injected at a rate of 4.1 mL minute −1 into the cerebellomedullary cistern. The SaP was recorded during and at 120 seconds after contrast administration. The maximum SaP (SaP max ) and minimum calculated cerebral perfusion pressure (CPP min ) were recorded for each case. Results Prior to contrast injection, mean ± SD, MAP was 73 ± 20 mmHg and SaP 0 was 10 ± 3 mmHg. The cerebral perfusion pressure (CPP) was 64 ± 20 mmHg. The contrast injection increased the SaP 0 to 73 ± 33 mmHg (SaP max ). After injection, MAP increased to 97 ± 25 mmHg and the CPP decreased to 14 ± 34 mmHg. A negative correlation was found between the lowest CPP and body weight (ρ = −0.77, p p max (ρ = −0.66, p min (ρ = −0.73, p Conclusions and clinical relevance Cerebral perfusion can severely decrease during cisternal myelography using the standard dose of iohexol. Bradycardia, apnoea and systemic hypertension were associated with decreased CPP.