The output of two sevoflurane vaporizers in the presence of helium

Background. Modern vaporizers are designed to deliver accurateand stable concentrations of volatile anaesthetic agents. Carriergas composition may adversely affect the output from vaporizers.No previous study has tested helium in combination with sevofluranevaporizers, a clinically useful combination especially in anaesthesiafor upper airway obstruction. Methods. This study evaluated the effect of increasing heliumconcentrations, carrier gas flow rates and varying the vaporizerdial setting on the output from Blease Datum^® and DragerVapor 19.3^® sevoflurane vaporizers. Results. The presence of helium in the carrier gas had negligibleeffects on the output from both of the sevoflurane vaporizerstested. Carrier gas flow rates had the greatest effect on outputbut changes were within ±10% of baseline. Conclusion. Helium/oxygen mixtures can be used with these vaporizerswithout adversely affecting their performance. Br J Anaesth 2002; 88: 711–13     

The output of four modern vaporizers in the presence of helium

It has been previously demonstrated that the output of calibrated vaporizers is influenced by the concentration of nitrous oxide in the carrier gas. This study was performed to determine whether helium in the carrier gas affects the output of modern calibrated vaporizers. A factorial design was used to determine the influence of carriergas helium concentration, carriergas flow rate and vaporizer dial setting on the output of four vaporizers: Ohio Calibrated Enflurane, Ohio Calibrated Isoflurane, Ohmeda Isotec 4, and Dräger Vapor 19.1 Isoflurane. Three vaporizers of each model were tested. Output was converted to % of baseline so that different dial settings could be compared. For a given dial setting, baseline was defined as the output at a carriergas flow rate of 3 L · min^?1 and helium concentration of zero. The data were analyzed using multiple linear regression. There was an effect of helium concentration on vaporizer output in all models. None of these changes was clinically important, since vaporizer output did not vary by more than ± 10%, except at high flows and at high helium concentrations with the Ohmeda Isotec 4. It is concluded that these vaporizers can be used safely with helium.     

The desflurane (Tec 6) vaporizer: design, design considerations and performance evaluation

We have described the design and design considerations of thedesflurane Tec 6 "vaporizer" and have tested its performancecharacteristics. The vaporizer differs from previous vaporizersdesigned for anaesthesia in that electromechanical rather thanmechanical controls accommodate the different physical characteristicsof desflurane. This design; while offering perhaps an increasedrisk of failure (owing to sophisticated electronic componentsand circuitry), on the other hand offers the decreased likelihoodof accidental delivery of very large concentrations of liquidanaesthetic resulting from tilting or overfilling and alarmsand warnings not previously incorporated into the design ofanaesthetic vaporizers. The output characteristics of the vaporizerare as expected, based on the design: desflurane concentrationoutput in oxygen has accuracy (±15%) which is similarto that of the mechanical vaporizers; output decreases whennitrous oxide is added owing to the lower viscosity, but remainswithin 20% of the dial setting or 0.5% absolute. (Br. J. Anaesth.1994; 72: 474–479)     

Long-term performance of Tec vaporizers

We reviewed the maintenance records of Tec vaporizers which had been in clinical use for up to 4 years. Tec 4s and Enfluratec 3s were found to be extremely reliable, but Fluotec 3s suffered progressively from mechanical and calibration problems. Their most recurrent fault was sticking valves caused probably by thymol crystallizing on the valve faces. This fault did not occur with Fluotec 4s, which are designed to prevent liquid agent reaching the valve surfaces. We found, in a study of the effects of thymol accumulation, that only occasional draining of a Fluotec vaporizer is required to keep thymol concentration below the level at which its output is reduced. We conclude that, if regular field calibration checks are carried out as a safety measure, the service interval for Tec vaporizers could be extended beyond Ohmeda's present recommendation of one year.     

Estimation of changes in cardiac output from the arterial blood pressure waveform in the upper limb

We have developed a new pulse contour cardiac output (PulseCO)algorithm based on frequency analysis studies of the arterialsystem. PulseCO was compared with thermodilution cardiac output(TDCO) in 10 patients undergoing cardiac surgery. Results fromone patient were unsuitable for analysis. In the remaining ninepatients, 142 TDCO determinations were compared with PulseCOafter logarithmic transformation and after being normalizedby the initial cardiac output in each patient. Each determinationwas usually the average of three measurements. Least squaresregression gave y=0.77x (r²=0.81) and the limits of agreementwere from –26% to +21%. The accuracy of PulseCO in determiningshort-term changes in cardiac output was assessed by comparingthe ratios of consecutive PulseCO determinations with the ratiosof the corresponding, consecutive TDCO determinations. Leastsquares regression gave y=0.71x (r²=0.70) and the limits ofagreement were from –21% to +25%. After phenylephrinehad been given to five patients, PulseCO showed an increasein systemic vascular resistance consistent with the known pharmacologicalactions of the drug. The PulseCO algorithm was incorporatedinto a computer program that acquires arterial pressure datafrom an analogue-to-digital converter and displays beat-to-beattrend values. Br J Anaesth 2001; 86: 486–96     

Less invasive determination of cardiac output from the arterial pressure by aortic diameter-calibrated pulse contour

Background. Cardiac output by modelflow pulse contour methodcan be monitored quantitatively and continuously only afteran initial calibration, to adapt the model to an individualpatient. The modelflow method computes beat-to-beat cardiacoutput (COmf) from the radial artery pressure, by simulatinga three-element model of aortic impedance with post-mortem datafrom human aortas. Methods. In our improved version of modelflow (COmfc) we adaptedthis model to a real time measure of the aortic cross-sectionalarea (CSA) of the descending aorta just above the diaphragm,measured by a new transoesophageal echo device (HemoSonic 100).COmf and COmfc were compared with thermodilution cardiac output(COtd) in 24 patients in the intensive care unit. Each thermodilutionvalue was the mean of four measurements equally spread overthe ventilatory cycle. Results. Least squares regression of COtd vs COmf gave y=1.09x[95%confidence interval (CI) 0.96–1.22], R²=0.15, and of COtdvs COmfc resulted in y=1.02x(95% CI 0.96–1.08), R²=0.69.The limits of agreement of the un-calibrated COmf were –3.53to 2.79, bias=0.37 litre min^–1 and of the diameter-calibratedmethod COmfc, –1.48 to 1.32, bias=–0.08 litre min^–1.The coefficient of variation for the difference between methodsdecreased from 28 (un-calibrated) to 12% after diameter-calibration. Conclusions. After diameter-calibration, the improved modelflowpulse contour method reliably estimates cardiac output withoutthe need of a calibration with thermodilution, leading to aless invasive cardiac output monitoring method.      

Dobutamine-induced dissociation between changes in splanchnic blood flow and gastric intramucosal pH after cardiac surgery

Gastric intramucosal acidosis, a sign of splanchnic tissue hypoxia,is common after cardiac surgery. We tested the hypothesis thatan increase in splanchnic blood flow induced by dobutamine improvessplanchnic tissue oxygenation after cardiac surgery. We measuredchanges in gastric intramucosal pH, splanchnic blood flow andoxygen transport in response to increased systemic flow inducedby dobutamine (mean 4.4 (range 3.0–7.0) µg kg^–1min^–1) after coronary artery bypass. We studied 22 stablepostoperative patients who were allocated randomly to receivedobutamine (n = 11) or to serve as controls (n = 11). Dobutaminewas given also to a separate group with a low cardiac indexafter operation (n = 6). The end-point was to increase cardiacindex by at least 25% and to exceed 2 litre min^–1 m^–2.Dobutamine consistently increased mean splanchnic blood flow(control 0.6 (SD0.2) vs 0.7 (0.2) litre min^–1 m^–2(P<0.05); normal cardiac output and dobutamine 0.7 (0.2)vs 1.1 (0.4) litre min^–1 m^–2 (P<0.01); low cardiacoutput and dobutamine 0.4 (0.1) vs 0.7 (0.1) litre min^–1m^–2 (P<0.05)) and oxygen delivery (control 102 (29)vs 111 (28) ml min^–1 m^–2 (ns); normal cardiac outputand dobutamine 106 (27) vs 156 (47) ml min^–1 m^–2(P < 0.01); low cardiac output and dobutamine 75 (21) vs110 (26) ml min^–1 m^–2 (P<0.05)) but had no effecton splanchnic oxygen consumption (control 44 (10) vs 49 (10)ml min^–1 m^–2 (ns); normal cardiac output and dobutamine45(12) vs 51 (17) ml min^–1 m^–2 (ns); low cardiacoutput and dobutamine 37 (9) vs 40 (9) ml min^–1 m^–2(ns)). Despite this, dobutamine reduced gastric intramucosalpH in all patients with low cardiac output (7.33 (0.12) vs 7.25(0.06)(P<0.05)) and in 50% of patients with stable haemodynamics(7.37(0.07) vs 7.34(0.06) (ns)). In contrast, gastric intramucosalpH remained stable in the control group (7.34 (0.05) vs 7.34(0.04) (ns)).We conclude that dobutamine resulted in a dissociationbetween splanchnic oxygen delivery and gastric mucosal tissueoxygenation, suggesting inappropriate distribution of bloodflow within the splanchnic region. (Br. J. Anaesth. 1995; 74:277–282)     

Patient-controlled analgesia for labour using remifentanil: a feasibility study

We have investigated the efficacy and safety of remifentanilin a patient-controlled analgesia device for labour in 21 women.Remifentanil was available in increasing doses (bolus doses0.25–1.0 µg kg^–1) with and without a backgroundinfusion (0.025–0.05 µg kg^–1 min^–1).A lockout time of 2 min was used. Thirteen out of 21 (62%) womenchose to continue using remifentanil up to and during delivery.Nineteen out of 21 (90%) achieved a reduction in pain scorefrom baseline. Using a VAS of 0–10 cm the median maximumreduction in pain score was 3 cm (range 0–8 cm). Therewas a significant reduction (P<0.05) from baseline pain scores(median= 8 cm) to scores at bolus doses in the range 0.25–0.5µg kg^–1 (median=5 cm). There were no significantreductions in the fetal heart rate. Apgar scores and cord bloodgas analyses remained within normal limits. We conclude thata remifentanil patient-controlled analgesia system (bolus doses0.25–0.5 µg kg^–1, without a background infusion)may safely provide worthwhile, although incomplete, analgesiafor labour. Br J Anaesth 2001; 87: 415–20     

OXPRENOLOL AND THE CIRCULATION DURING ANAESTHESIA IN THE DOG: INFLUENCE OF INTRINSIC SYMPATHOMIMETIC ACTIVITY

Oxprenolol is a non-selective adrenergic beta-receptor antagonistdisplaying beta-mimetic activity. To test the hypothesis thatbeta-mimetic activity could minimize the response of the circulationto adrenergic beta-receptor blockade, cumulative dose-responsecurves to oxprenolol 0.1–1.6mgkg^–1 were obtainedin seven anaesthetized dogs. Anaesthesia was maintained with0.5% halothane supplementing nitrous oxide 66% in oxygen, undermoderately hypocapnic IPPV. Oxprenolol, up to 0.4mgkg^–1i.v., caused modest increases in heart rate, LVdP/dt max andcardiac output. With the largest dose (1.6mg kg^–1), significantincreases in heart rate(+19%), LVdP/dtmax(+13%)and cardiac output(+27%)wereobserved while arterial pressure remained unchanged and systemicvascular resistance decreased (–18%).     

EFFECT OF NITROUS OXIDE ON THE OUTPUT OF THREE HALOTHANE VAPORIZERS

The effect of changing the composition of the carrier gas from66% nitrous oxide in oxygen to 100% oxygen was examined in threehalothane vaporizers (Fluotec Mk 3, Drager Vapor 19 and Abingdonhalothane vaporizer). All showed a transient increase in outputfollowing the discontinuation of the nitrous oxide. The effectwas minor(2–8% of indicated output) and short-lived (1–4min)at the fresh gas flows used. The steady-state output of thevaporizers, once the transient response was over, was foundto be lower with 100% oxygen as carrier gas than it had beenwith 66% nitrous oxide in oxygen. The difference was minor inthe case of the Drager Vapor 19 (1% of indicated output) andFluotec Mk3(5% of indicated output), but greater in the caseof the Abingdon (15% of indicated output).     

Effects of phenylephrine and prostaglandin E on ventriculo-arterial matching during halothane anaesthesia

We have investigated the effects of phenylephrine alone andcombined with prostaglandin E₁ (PGE₁) on ventriculo-arterialmatching during halothane anaesthesia in dogs. The ratio ofleft ventricular end-systolic elastance (Ees) to effective arterialelastance (Ea) was used as an index of ventriculo-arterial matching.In group 1 (n = 7), measurements were performed at control,1.5% halothane, halothane+phenylephrine 1–10 µgkg^–1 min^–1, and halothane + phenylephrine + PGE₁,0.2–1.0 or 1.0–2.0 µg kg^–1 min^–1.In group 2 (n = 5), dobutamine 2 and 5 µg kg^–1 min^–1was infused during halothane anaesthesia. Halothane 1.5% decreasedmean arterial pressure (MAP), cardiac output and Ees. Phenylephrinerestored MAP, but further decreased cardiac output. The decreasein Ees produced by halothane was reversed by phenylephrine.PGE₁ increased cardiac output and reversed the increases inEa and Ea/Ees during phenylephrine infusion. Dobutamine alsoreversed halothane-induced decreases in MAP, cardiac outputand Ees, and improved Ea/Ees. Our results indicate that combineduse of PGE₁ with phenylephrine can eliminate the vasoconstrictiveproperty of phenylephrine, resulting in an improvement in ventriculo-arterialmatching.     

THE INFLUENCE OF CARRIER GAS ON THE OUTPUT OF AUTOMATIC PLENUM VAPORIZERS

The effect of the physical characteristics of the carrier gason the output of automatic plenum vaporizers was studied. TheVapor and Fluomatic halothane output at all dial settings washighest with oxygen as the carrier gas, as compared with heliumand nitrous oxide and was a function of carrier gas viscosityat all dial settings. The output of the Fluotec Mark 2 at the0.5 and 1 % settings was highest with nitrous oxide as the carriergas, but at 2, 3 and 4% settings it was highest with oxygen;at the 0.5% and 1% dial settings it was a function of carriergas density, but at 2%, 3% and 4% it was a function of carriergas viscosity.     

Simultaneous measurement of cardiac output by thermodilution, thoracic electrical bioimpedance and Doppler ultrasound

To evaluate the accuracy of two non-invasive techniques forcardiac output (CO) measurement, we have measured CO simultaneouslyby thoracic electrical bioimpedance (TEB), pulsed Doppler ultrasound(DU) and standard thermodilution methods (TD) under differentclinical conditions. Measurements were made in 10 patients:(I) during steady state anaesthesia with controlled IPPV ventilation(n = 131), spread over the entire ventilatory cycle; (II) duringapnoea (n = 56); (III) during spontaneous breathing (n = 152)in the intensive care unit. Mean (SD) cardiac output valueswere: (I) CO_TD 3.5 (1.0) litre min^–1, CO_TEB 3.4 (0.7)litre min^–1 CO_DU 2.8 (0.7) litre min^–1; (II) CO_TD3.6 (0.6) litre min^–1, CO_TEB 3.5 (0.4) litre min^–1,CO_DU 2.9 (0.7) litre min^–1; (III) CO_TD 7.7 (1.5) litremin^–1, CO_TEB 7.6 (1.9) litre min^–1, CO_DU 5.2 (1.4)litre min^–1. The mean percentage deviation of TEB fromTD ranged from –2.2% to 1.4% and that of DU from TD wasfrom –16% to –32%. There were no statistically significantdifferences between TD and TEB, but TD and DU differed significantlyduring IPPV, apnoea and spontaneous ventilation (P < 0.0001).(Br. J. Anaesth. 1994; 72:133–138) ^*Department of Anaesthesiology, Caritas Krankenhaus, Werkstr.1, 66763 Dillingen/Saar, Germany      

Downward movement of syringe pumps reduces syringe output

We studied how lowering a syringe pump and changing the outflowpressure could affect syringe pump output. We experimentallyreduced the height of three different syringe pump systems by80 cm (adult setting) or 130 cm (neonatal setting),as can happen clinically, using five flow rates. We measuredthe time of backward flow, no flow and the total time withoutflow. An exponential negative correlation was present betweeninfusion rate and time without flow (r²=0.809 to 0.972, P<0.01).Minimum flow rates of 4.4 and 2.6 ml h^–1 respectivelywere calculated to give 60 and 120 s without infusion.The compliance of the different syringe pumps and their infusionsystems was linearly correlated with the effective time withoutinfusion (r²=0.863, P<0.05). We conclude that the heightof the syringe pumps should not be changed during transportation.If vertical movement of the syringe pump is necessary, the drugsshould be diluted so that the flow rate is at least 5 ml h^–1. Br J Anaesth 2001; 86: 828–31     

Xenon increases total body oxygen consumption during isoflurane anaesthesia in dogs

Background. This study was designed to examine whether the couplingbetween oxygen consumption (V^·O₂) and cardiac output(CO) is maintained during xenon anaesthesia. Methods. We studied the relationship between V^·O₂ (indirectcalorimetry) and CO (ultrasound flowmetry) by adding xenon toisoflurane anaesthesia in five chronically instrumented dogs.Different mixtures of xenon (70% and 50%) and isoflurane (0–1.4%)were compared with isoflurane alone (1.4% and 2.8%). In addition,the autonomic nervous system was blocked (using hexamethonium)to study its influence on V^·_O2 and CO during xenon anaesthesia. Results. Mean (SEM) V^·O₂ increased from 3.4 (0.1) ml kg^–1 min^–1during 1.4% isoflurane to 3.7 (0.2) and 4.0 (0.1) ml kg^–1 min^–1after addition of 70% and 50% xenon, respectively (P<0.05),whereas CO and arterial pressure remained essentially unchanged.In contrast, 2.8% isoflurane reduced both, V^·O₂ [from3.4 (0.1) to 3.1 (0.1) ml kg^–1 min^–1]and CO [from 96 (5) to 70 (3) ml kg^–1 min^–1](P<0.05). V^·O₂ and CO correlated closely during isofluraneanaesthesia alone and also in the presence of xenon (r²=0.94and 0.97, respectively), but the regression lines relating COto V^·_O2 differed significantly between conditions, withthe line in the presence of xenon showing a 0.3–0.6 ml kg^–1 min^–1greater V^·O₂ for any given CO. Following ganglionic blockade,50% and 70% xenon elicited a similar increase in V^·O₂,while CO and blood pressure were unchanged. Conclusions. Metabolic regulation of blood flow is maintainedduring xenon anaesthesia, but cardiovascular stability is accompaniedby increased V^·O₂. The increase in V^·_O2 is independentof the autonomic nervous system and is probably caused by directstimulation of the cellular metabolic rate. Br J Anaesth 2002; 88: 546–54     

A comparison of cardiac output derived from the arterial pressure wave against thermodilution in cardiac surgery patients

In three clinical centres, we compared a new method for measuringcardiac output with conventional thermodilution. The new methodcomputes beat-to-beat cardiac output from radial artery pressureby simulating a three-element model of aortic input impedance,and includes non-linear aortic mechanical properties and a self-adaptingsystemic vascular resistance. We compared cardiac output bycontinuous model simulation (MF) with thermodilution cardiacoutput (TD) in 54 patients (18 female, 36 male) undergoing coronaryartery bypass surgery. We made three or four conventional thermodilutionestimates spread equally over the ventilatory cycle. In 490series of measurements, thermodilution cardiac output rangedfrom 2.1 to 9.3, mean 5.0 litre min^–1. MF differed +0.32(1.0) litre min^–1 on average with limits of agreementof –1.68 and +2.32 litre min^–1. Differences decreasedwhen the first series of measurements in a patient was usedto calibrate the model. In 436 remaining series, the mean differencebecame –0.13 (0.47) litre min^–1 with limits of agreementof –1.05 and +0.79 litre min^–1. When consecutivemeasurements were made, the change was greater than 0.5 litremin^–1, on 204 occasions. The direction of change was thesame with both methods in 199. The difference between the methodsremained near zero during surgery suggesting that a single calibrationper patient was adequate. Aortic model simulation with radialartery pressure as input reliably monitors changes in cardiacoutput in cardiac surgery patients. Before calibration, themodel cannot replace thermodilution, but after calibration themodel method can quantitatively replace further thermodilutionestimates. Br J Anaesth 2001; 87: 212–22     

Cerebral pressure autoregulation and carbon dioxide reactivity during propofol-induced EEG suppression

We studied cerebral pressure autoregulation and carbon dioxidereactivity during propofol-induced electrical silence of theelectroencephalogram (EEG) in 10 patients. Anaesthesia was inducedwith propofol 2.5 mg kg^–1, fentanyl 3 µg kg^–1and vecuronium 0.1 mg kg^–1, and a propofol infusion of250–300 µg kg^–1 min^–1 was used to induceEEG silence. Cerebral pressure autoregulation was tested byincreasing mean arterial pressure (MAP) by 24 (SEM 5) mm Hgfrom baseline with an infusion of phenylephrine and simultaneouslyrecording middle cerebral artery blood flow velocity (vmca)using transcranial Doppler. Carbon dioxide reactivity was testedby varying Pa_co2 between 4.0 and 7.0 kPa and recording vmcasimultaneously. Although absolute carbon dioxide reactivitywas reduced, relative carbon dioxide reactivity was within normallimits for all patients studied (mean 8.5 (SEM 0.8) cm s^–1kPa^–1 and 22 (2)% kPa^–1, respectively). No significantchange in vmca (34 (2) and 35 (2) cm s^–1) was observedwith the increase in MAP (77 (4) to 101 (4) mm Hg) during autoregulationtesting. We conclude that cerebral carbon dioxide reactivityand pressure autoregulation remain intact during propofol-inducedisoelectric EEG.     

FENTANYL INHIBITS THE UPTAKE OF [3H]NORADRENALINE IN CULTURED NEURONAL CELLS

We have examined how fentanyl modulates [³H]noradrenaline uptakein two cultured neuronal cell preparations, the human neuroblastomaSH-SY5Y and the rat phaeochromocytoma PC12. Fentanyl produceda significant, dose-dependent inhibition of [³noradrenalineuptake at concentrations in excess of 0.1 µmol litre^–1(P <0.05) and 0.3 µmol litre^–1 (P < 0.05)for PC12 and SH-SY5Y cells, respectively. However, these valuesexceed the serum concentration of fentanyl required to produceanalgesia. At the maximum concentration examined (100 µmollitre^–1), fentanyl produced 85–95% inhibition ofuptake. This effect was not antagonized by naloxone, implyinga nonopioid mechanism of action. Imipramine 1 µmol litre^–1reduced [³H]noradrenaline uptake by 65–70% but morphine,in contrast to fentanyl, had no effect (P > 0.1). (Br. J.Anaesth. 1993; 71: 540–543)     

SODIUM THIOSULPHATE DECREASES BLOOD CYANIDE CONCENTRATIONS AFTER THE INFUSION OF SODIUM NITROPRUSSIDE

Plasma and red cell cyanide, and plasma thiocyanate, concentrationswere measured in 30 patients undergoing elective nitro-prusside-inducedhypotension. One randomly selected group (n = 15), who received0.21–0.70 mg kg^–1 over periods of 50– 160min, were given a bolus of sodium thio-sulphate 10.6–38.5mg kg^–1 immediately on cessation of the nitroprussideadministration. The other group, who received infusions of 0.11–0.85mg kg^–1 for periods of 59—197 min, received no antidote.Cyanide concentrations, expressed as a percentage of the immediatepost-infusion values, were significantly lower in the treatedgroup in all subsequent blood samples (at 10, 30 and 60 min;plasma cyanide P < 0.05; red cell cyanide P < 0.001).Improved cyanide metabolism was further demonstrated by a sharpincrease in mean plasma thiocyanate concentration (P < 0.05)in the group receiving the antidote.     

Does the optimization of cardiac output by fluid loading increase splanchnic blood flow?

We studied the effects of increasing cardiac output by fluidloading on splanchnic blood flow in patients with haemodynamicallystabilized septic shock. Eight patients (five female, 39–86yr) were assessed using a transpulmonary thermo-dye-dilutiontechnique for the measurement of cardiac index (CI) intrathoracicblood volume (ITBV) as a marker of cardiac preload and totalblood volume (TBV). Splanchnic blood flow was measured by thesteady state indocyanine-green technique using a hepatic venouscatheter. Gastric mucosal blood flow was estimated by regionalcarbon dioxide tension (PR_CO2). Hydroxyethyl starch was infusedto increase cardiac output while mean arterial pressure waskept constant. In parallel, mean norepinephrine dosage couldbe reduced from 0.59 to 0.33 µg kg^–1 min^–1.Mean (SD) TBV index increased from 2549 (365) to 3125 (447)ml m^–2, as did ITBV index from 888 (167) to 1075 (266)ml m^–2 and CI from 3.6 (1.0) to 4.6 (1.0) litre min^–1m^–2. Despite marked individual differences, splanchnicblood flow did not change significantly neither absolutely (from1.09 (0.96) to 1.19 (0.91) litre min^–1 m^–2) norfractionally as part of CI (from 28.4 (19.5) to 24.9 (16.3)%).Gastric mucosal PR_CO2 increased from 7.7 (2.6) to 8.3 (3.1)kPa. The PCO₂-gap, the difference between regional and end-tidalPCO₂, increased slightly from 3.2 (2.7) to 3.4 (3.1) kPa. Thus,an increase in cardiac output as a result of fluid loading isnot necessarily associated with an increase in splanchnic bloodflow in patients with stabilized septic shock. Br J Anaesth 2001; 86: 657–62