CHOICE OF ANESTHETIC REGIMEN INFLUENCES HEMODYNAMIC-RESPONSE TO CEMENTED ARTHROPLASTY

Haemodynamic changes during bilateral cemented arthroplasty (BCA) were compared in dogs anaesthetized with isoflurane/N2O (ISOF) or diazepam /fentanyl (100 mu g . kg(-1)/N2O (FENT). Eight animals were anaestheti zed with each regimen. After establishing monitoring and recording bas eline values, BCA was performed. Haemodynamic measurements included ao rtic blood pressure (ABP) pulmonary artery pressure (PAP), right and l eft atrial pressures, and cardiac output. These were recorded at 30, 6 0, 180 and 300 sec after BCA. Lungs were removed and examined postmort em using quantitative morphometry. Groups demonstrated similar increas es in PAP (ISOF 15 +/- 2 to 32 +/- 7, FENT 19 +/- 4 to 38 +/- 13; P > 0.05 between groups, P < 0.05 vs baseline). The proportion of lung vas culature occluded by fat was not different between groups (ISOF 9.63 /- 3.38%, FENT 8.85 +/- 2.20%). Stroke volume decreased similarly in b oth groups (P > 0.05 between groups, P < 0.05 vs baseline). However, A BP decreased within one minute of BCA in ISOF (111 +/- 17 to 55 +/- 27 mmHg, P < 0.05) and two of eight dogs died. All FENT dogs survived an d hypotension (118 +/- 20 to 102 +/- 24 mmHg) was transient and less s evere (P < 0.05 vs ISOF). Increased heart rare (HR) was noted in FENT following BCA (73 +/- 8 to 108 +/- 25 beats . min(-1) P < 0.05). Basel ine HR was higher in ISOF (P < 0.05) and no increase in HR was noted. Systemic vascular resistance decreased in ISOF (P < 0.05), but not FEN T (P > 0.05 vs baseline, P < 0.05 vs ISOF). To assess the role of slow er baseline HR in FENT (73 +/- 8) versus ISOF (131 +/- 5), six FENT do gs were paced (130 beats . min(-1)) with epicardial leads and an AV se quential pulse generator to simulate the ISOF group's baseline HR Haem odynamic stability was maintained in this group in spite of a more rap id baseline HR The choice of anaesthetic regimen strongly influenced a cute haemodynamic changes in response to BCA.