Non Invasive Methods to Guide Volume Optimization

Overview

Goal directed volume therapy means that bolus doses of 150-250 ml colloid fluid is administered to the patient during contemporary measurement of the patients stroke volume. The fluid status is considered optimized when stroke volume no longer increases with more than 10%, indicating that the patient is close to the top of the Frank-Starling curve. Several studies show that volume optimization reduces hospital stay and reduces the amount of surgical complications. The overall purpose is to investigate if the much more simple non invasive technique Pleth Variability Index can replace oesophageal doppler to guide volume therapy in routine health care, and to analyse if a volume kinetic test can be used to evaluate hypovolemia before surgery and make specific rehydration possible by analysing the correlation between this test and fluid optimization using stroke volume measurements. Primary hypothesis: 1. The volume of colloids that is given to volume optimise an anesthetized patient using Pleth Variability Index shows a good correlation to the volume used if volume optimisation is undertaken by the guidance of oesophageal doppler. 2. Data from the two methods correlate and discriminates similarly volume responders from non responders. 3. A volume kinetic model that indicates dehydration can predict the need for rehydration in order to achieve a well hydrated patient at start of surgery.

The patients are not allowed to eat after midnight. Routine premedication is given with paracetamol and oxynorm/oxycontin. Thrombosis and antibiotic prophylaxis is given according to surgical department. The weight of the patient is notices on the morning of surgery (day 0). The patient arrives in the morning to the preoperative area. A urinary analysis is taken for urinary colour, creatinine, specific weight, osmolality, microalbuminuria and electrolytes. For 30 patients a volume kinetic analysis of 5 ml/kg infusion of acetated Ringers solution is undertaken between 6.30 and 8.00 am on the morning of surgery. During 15 minutes 5 ml/kg acetated Ringers solution is infused intravenously. Hb is continuously measured noninvasively by Masimo Radical 7 pulse oximeter (MasimoHb) and invasively with maximum 13 samples a 4 ml during 80 minutes (0, 10, 15, 25, 40, 50, 60 and 70 min. Double samples at start and 60 min. The volume kinetic part of the study is finished after 70 min when the patient urinates and the volume is measured. The patient is taken to the operating theatre and MasimoHb, NT-proBNP, Troponin T hs, pl-lactate, PI och PVI (stable value during 5 min) is registered before anaesthesia. Avoid having blood pressure cuff and pulse oximeter for PVI analysis on the same arm. Aim at PI \> 1 to get a reliable registration of PVI, otherwise try another finger. Anaesthesia: Epidural anaesthesia according to clinical praxis (activated after the first volume optimisation and kept activated during surgery) and anaesthesia according to clinical practise. The ventilation during anaesthesia is maintained using volume controlled mode, tidal volume 7 ml/kg (ideal weight, using the formula: men 50 + 0.91(height in centimetre -152.4); women 45.5 + 0.91(height in centimetre -152.4)), PEEP 5 - 10 cmH2O, respiratory rate to achieve normocapnia. Tidal volume and PEEP is maintained during surgery. The Doppler sond is placed after anaesthesia induction and after that the gastric sond is placed. During induction of anaesthesia an amount of u to 500 ml colloid solution as well as intermittently ephedrine in small doses of 2.5 - 10 mg can be given for circulatory stability. Antibiotics are given according to clinical practice. Preoperative fluid regimen: Grupp OD: Basic infusion: Buffered glucose 2.5% 1000 ml 2 ml/kg/h. The first volume optimization of stroke volume (SV) takes place after anaesthesia induction and a stable baseline of measurement is achieved. Note SV (mean value during 1 min), Flow time corrected (FTC), MasimoHb and PVI (mean value during 1 min). The PVI value is only visualised to the research nurse and not to the attending anaesthesiologist. Administer 3 ml/kg (actual weight) maximum 250 ml hydroxyethyl starch during 5 minutes. Wait for 5 minutes. Note SV, FTC, MasimoHb and PVI. If SV increases more than 10 % a new colloid bolus is given. This is repeated in cycles until SV not increases \> 10%, or DO2i \> 600 ml/min/m2. For every cycle SV, FTC, MasimoHb and PVI are noted. The first optimization is undertaken before start of surgery. SV, FTC, MasimoHb and PVI are followed during surgery. If SV is reduced \> 10% from the value after the last bolus dose a new volume optimization is repeated as described above. If more than 30 ml/kg hydroxyethyl starch 60 mg/ml is given, colloid solution is changed to albumin 4% or plasma. Bolus doses of albumin 4% and plasma are also 3 ml/kg with a maximum of 250 ml. Beside infusion of colloids, acetated Ringers solution 0-1000 ml can be given according to the decision from the attending anaesthesiologist. Blood loss is replaced ml by ml with colloid until Hb 90 g/l (100 if the patient has an ischemic heart disease or any other condition at the discretion from the attending anaesthesiologist). Thereafter replacement is given1:1 using SAG and colloid/albumin/plasma. If blood loss exceeds half the blood volume replacement is given only using SAG/plasma. Thrombocytes are given according to clinical practice. Any use of inotropic and vasoactive drugs is documented. At the end of surgery pl-lactate and Hb is measured invasively and non-invasively (HB). Estimated blood loss is registered. Grupp PVI: Basic infusion: Buffered glucose 2.5% 1000 ml 2 ml/kg/h. The first volume optimization of stroke volume (SV) takes place after anaesthesia induction and a stable baseline of measurement is achieved. Note PVI ( mean value during 1 min), MasimoHb, SV (mean value during 1 min) and Flow time corrected (FTC). Data from the oesophagus doppler is only visualised to the research nurse and not to the attending anaesthesiologist. Administer 3 ml/kg (actual weight) maximum 250 ml hydroxyethyl starch during 5 minutes. Wait for 5 minutes. Note SV, FTC, MasimoHb and PVI. If PVI is \>10 % and reduced give a new colloid bolus. For every cycle SV, FTC, MasimoHb and PVI are noted. The first optimization is undertaken before start of surgery. If PVI \>10 % the volume optimization is repeated as described above. If more than 30 ml/kg hydroxyethyl starch 60 mg/ml is given, colloid solution is changed to albumin 4% or plasma. Bolus doses of albumin 4% and plasma are also 3 ml/kg with a maximum of 250 ml. Beside infusion of colloids, acetated Ringers solution 0-1000 ml can be given according to the decision from the attending anaesthesiologist. Blood loss is replaced ml by ml with colloid until Hb 90 g/l (100 if the patient has an ischemic heart disease or any other condition at the discretion from the attending anaesthesiologist). Thereafter replacement is given1:1 using SAG and colloid/albumin/plasma. If blood loss exceeds half the blood volume replacement is given only using SAG/plasma. Thrombocytes are given according to clinical practice. Any use of inotropic and vasoactive drugs is documented. At the end of surgery pl-lactate and Hb is measured invasively and non invasively (HB). Estimated blood loss is registered. Both groups: If the patients' perioperative course demands that the anaesthesiologists in charge deviate from the study protocol the reason for this is registered in the CRF. All patients have a urinary bladder catheter or cystofix as decided by the surgeon. The temperature of the patient is measured. Hot air blanked is used to prevent hypothermia. Post-operatively after 12-24 hours and 36-48 hours pl-NT-proBNP and pl-troponinThs are measured. The patients weight is registered the morning on the day after surgery (day 1). Date for end of hospital stay is registered. A blinded team registers postoperative complications on the 3d day after surgery according to a preset protocol. The record is also reviewed retrospectively to document all complications during the first 30 days after surgery. For patients 1-75 Doppler and PVI are recorded simultaneously to allow analysis of concordance between PVI and Doppler as guide to fluid optimization. Also biochemical analyses of cardiac enzymes as part of the study are undertaken in patients 1-75. For patients 1-150 the outcome measure postoperative complications is registered.