Spinal anaesthesia at low and moderately high altitudes: A comparison of anaesthetic parameters and hemodynamic changes

Background: Hypoxemia caused high altitude leads to an increase and variability in CSF volume. The purpose of this prospective study was to detect the differences, if any, between moderately highlanders and lowlanders in terms of anaesthetic parameters under neuroaxial anaesthesia. Methods: Consecutive patients living at moderately high altitude (Erzurum, 1890 m above the sea level) and sea level (Sakarya, 31 m above the sea level) scheduled for elective lower extremity surgery with spinal anaesthesia were enrolled in this study (n = 70, for each group). Same anaesthesia protocol was applied for all patients. Spinal anaesthesia was provided with hyperbaric bupivacaine 0.5 %, 9 mg (1.8 mL) in all patients. Anaesthetic characteristics and hemodynamic parameters of patients were recorded. The findings obtained in two different altitudes were compared using appropriate statistical tests. If data was not normally distributed, comparisons were determined using the Mann-Whitney U-test. Comparisons were determined using the Independent T test when data was normally distributed and Fisher's exact test was used to compare the percentage values. Results: Duration of the block procedure (minutes) was significantly shorter at the sea level (14.34 ± 0.88) than at moderate altitude (20.38 ± 1.46) (P < 0.001). Motor block duration (minutes) was higher at the sea level compared to the moderate altitude (310.2 ± 104.2, 200.4 ± 103.2; respectively; P < 0.05). Also, the sensory block time (minutes) was higher at the sea level compared to moderate altitude (200.2 ± 50. minutes vs. 155.2 ± 60.7 min; respectively; P < 0.05). Moderate altitude group had significantly higher MABP values at baseline, during surgery and at postoperative 1^st and 2nd hours than in the sea level group (P < 0.05, for all). Moderately high altitude group had lower heart rate values at baseline, during surgery and postoperative 1^st and 2^nd hours compared with the sea level group (P < 0.05). PDPH was seen more frequently (7.14 vs. 2.85 %; P < 0.05) at moderate altitude. Conclusions: Hemodynamic variations and more anaesthetic requirements following the spinal anaesthesia may be observed at moderately high altitudes compared to the sea level. Trial registration: Australian New Zealand Clinical Trials Registry: ACTRN12614000749606.