Interstitial fluid accumulation does not influence oxygen uptake in the rabbit small intestine

Crystalloid resuscitation increases interstitial fluid volume. Intestinal ischemia and impaired barrier function may contribute to the precipitation of multiple organ failure. Accordingly, the intestine was chosen as target organ to test whether interstitial oedema impairs oxygen extraction by the tissue.
The portal vein in anaesthetized rabbits was partially obstructed for 30 min along with an intravenous infusion of 0.9% saline 60–90 ml kg^-1 (oedema group, n = 7). Total water content of the small intestine increased from 3.4 ml g^-1 dry weight in control (n = 8) to 3.9 ml g^-1 in the oedema group ( P = 0.049). Small intestinal O₂ uptake was calculated from the arteriovenous O₂ content and electromagnetic flow measurements in the superior mesenteric artery. Mesenteric flow was reduced stepwise by a snare occluder around the artery. Intestinal oxygen-ation was monitored indirectly as well, by means of mesenteric venous lactate, arterial base excess and by mucosal pH (pH_i) assessed tonometrically.
The oxygen extraction ratios were similar in the oedema and control group at similar oxygen supplies. After a 45 min flow reduction to 15% of baseline mesenteric venous lactate and pH_i did not differ between the groups. pH; averaged 7.31 and fell to 6.74. Below an intestinal O₂ uptake of 2.5 ml min^-1, pH_i correlated somewhat better with O₂ uptake (r=0.66) than did arterial base excess (r=0.50).
The results indicate that acute elevation of extracellular volume to the extent in the present study, does not impede oxygen uptake in the gut.     

Predictable nitrous oxide uptake enables simple oxygen uptake monitoring during low flow anaesthesia

The uptake rate of oxygen and nitrous oxide were studied during low flow anaesthesia with enflurane or isoflurane in nitrous oxide with either spontaneous or controlled ventilation. The excess gas flow and composition were analysed. The nitrous oxide uptake rate was in agreement with Severinghaus'formula _N20 1000.t^-0.5. The composition of excess gas was predictable and the following formula for oxygen uptake could be derived: O₂=fgO₂ -0.45 (fgN²O -(kg: 70.1000.t^-0.5)) where oxygen uptake rate (O₂, ml.min^-1) equals oxygen fresh gas flow (fgO₂) minus 0.45 times the difference between the fresh gas flow of nitrous oxide (fgN₂O), ml.min^-1 and estimated uptake of nitrous oxide. The equation assumes constant inspired gas concentrations of 30% oxygen and 65–70% nitrous oxide. The oxygen uptake rates calculated from this formula were in good agreement with measured uptake rates. Thus, continuous monitoring of oxygen uptake rates is possible by using only reliable flowmeters and analysis of inspried oxygen concentration.     

Haemodynamics and Oxygen Consumption in the Dog During High Epidural Block with Special Reference to the Splanchnic Region

High epidural block (Th I-IV) with bupivacaine was carried out in 16 dogs. Mean arterial blood pressure decreased to 52% of control value owing to nearly equal decreases in systemic vascular resistance and cardiac output. Portal venous blood flow decreased from 25.8 ± 8.6 to 16.7 ±7.2 ml/kg b.w. × min^-1 following epidural block, while hepatic arterial blood flow remained unchanged at 9.1 ± 3.1 ml/kg b.w. × min^-1 owing to a reduction in hepatic arterial resistance of 51 %. Hepatic oxygen uptake was maintained during the epidural block through increased oxygen extraction. However, total oxygen uptake decreased by 18 % and, in spite of this, arteriovenous oxygen content difference increased by 25%, indicating circulatory depression.     

Differential effects of dobutamine, dopamine, and noradrenaline on splanchnic haemodynamics and oxygenation in the pig

Supranormal oxygen (O₂) transport may benefit critically ill patients. Catecholamines are clinically employed for this purpose. However, their effects on splanchnic haemodynamics and oxygenation are not well defined. The effects of dobutamine (DOBU), dopamine (DOPA), and noradrenaline (NA) on splanchnic blood flows (electromagnetic flow probes), O₂ deliveries and uptakes (catheterisation of portal and hepatic veins) were studied in nine anaesthetised (ketamine/flunitrazepam), ventilated, paralysed, and laparotomised pigs. All three catecholamines (DOPA at 15 μg·kg^-1 · min^-1, DOBU at 13 μg · kg^-1 · min^-1, NA at 0.4 μg · kg^-1 · min^-1) significantly ( P <0.05) increased cardiac output and systemic O₂ delivery. Only DOPA increased small intestinal and total hepatic blood flows, and O₂ deliveries, and decreased O₂ extractions. The same parameters did not change during DOBU. During NA, total hepatic blood flow and O₂ delivery decreased, and hepatic O₂ extraction increased. During all three catecholamines, small intestinal and total hepatic O₂ uptakes did not change significantly. Whereas hepatic arterial blood flow decreased during both DOPA and NE, portal venous flow increased during DOPA. These data suggest that in the experimental model used splanchnic O₂ supply and O₂ reserve capacity appear improved by DOPA, unaffected by DOBU, and impaired by NA.     

Influence of Dixyrazine on Intestinal and Renal Vasoconstrictor Responses During Fentanyl-Nitrous Oxide Anaesthesia

In cats (n=24) anaesthetized with fentanyl-nitrous oxide and diazepam, stimulation of the hypothalamic defence-alarm area (DA) or afferent activation of somatic pain fibres (SA), elicited a pronounced increase in intestinal (DA 297%, SA 107%) and renal (DA 214%, SA 90%) vascular resistance as well as a decrease in diuresis. These stress-related responses were markedly counteracted by dixyrazine (0.15-0.5 mg · kg^-1 b.w. i.v.), especially in the kidney where the subsequent increase in vascular resistance to DA and SA stimulations amounted to only 25% and 13%, respectively, while diuresis increased. Corresponding data for stimulation-induced increases in intestinal vascular resistance after dixyrazine were DA 156% and SA 28%. Dixyrazine is suggested to act both through interaction with peripheral α-adrenergic mechanisms in control of vascular tone and through central nervous cardiovascular reflex depression. In man (n=7), during a similar form of anaesthesia, portal vein blood flow (1137±177 ml) was measured by the continuous thermodilution method. Preportal tissue vascular resistance during surgery decreased significantly (11.3 vs 8.7 kPa · min ml^-1 · 10^-3) after i.v. dixyrazine (0.15mg · kg^-1 b.w.). A concomitant increase in oxygen uptake in preportal tissues occurred (19.9 ml min^-1 vs 24.5 ml · min^-1).     

The Venturi Anaesthesia Circuit II Carbon Dioxide Production and Gas Flow Requirements

Carbon dioxide production was measured in 20 adult patients undergoing alloplastic operation of the hip. Body weight ranged from 40 to 81 kg. Anaesthesia consisted of lumbar plexus block, i. v. diazepam, pethidine, pavulon and N₂O/O₂ under controlled ventilation. CO₂ production was 2.13 ml kg^-1 min^-1 (interquartile range 2.09-2.23). A fresh gas flow rate of about 30 ml kg^-1 min^-1 was required for the elimination of CO₂ produced when using the Venturi system for inhalation anaesthesia.     

Effects of induced hypotension on arterial blood–gases under spontaneous breathing

The effects of deliberate hypotension on both Pao₂ and Paco₂ were investigated under isoflurane anaesthesia with spontaneous breathing from a laryngeal mask. Lumbar epidural block was introduced; anaesthesia was induced with thiamylal (4 mg kg^-1) and maintained with 0.5% isoflurane in nitrous oxide (4 1 min^-1) and oxygen (2 1 min^-1) under spontaneous breathing. After that nitroglycerin, trimetaphan or prostaglandin E₁ were used to induce a hypotension of 70% of control. All three drugs significantly decreased Pao₂, from 19.9 ± 3.3, 19.2 ±2.7, and 19.6 ± 3.1 kPa to 14.6 ± 1.9, 16.6 ± 2.2, and 16.2 ± 2.4kPa (mean ± s.d.), respectively; none of them increased Paco₂. In spite of the sparing of functional residual capacity under spontaneous breathing, the levels of reduction of Pao₂ were the same as levels reported in paralyzed and mechanically ventilated subjects. In conclusion, under deliberate hypotension Pao₂ decreases to a considerable degree, even under spontaneous breathing, presumably not because of alveolar hypoventilation, but because of the suppression of hypoxic pulmonary vasoconstriction by the drugs used in this study.     

Cardiovascular effects of moderate normovolaemic haemodilution during enflurane–nitrous oxide anaesthesia in man

The cardiovascular effects of mild normovolaemic haemodilution during enflurane–nitrous oxide anaesthesia were studied in 20 patients with normal cardiac function before, during and after total hip replacement. After induction of anaesthesia, patients were randomly allocated to one control group (C), or one haemodiluted group (H) where Hct was decreased to 30% by replacement of blood volume by an identical volume of hydroxyethyl starch 200/0.5. Each patient was monitored with a pulmonary artery catheter allowing the measurement of right ventricular ejection fraction. During haemodilution, stroke index and right ventricular end–diastolic volume index increased from 33.1 7.9 to 39.3 7.1 ml M^-2 and from 73.8 20.3 to 94.9 18.5 mlM^-2 respectively (mean s.d., both P <0.05). However, heart rate decreased so that cardiac index did not change. O₂ delivery decreased significantly (from 389 70 to 31163 ml–min^-1 –m^-2; P <0.05), but was not different to the control group. O₂ consumption was maintained by an increase in O₂ extraction. During the surgical procedure, cardiac index was higher in the haemodiluted group than in the control group, so that O₂ delivery was similar in the two groups. O₂ consumption tended to be greater in the haemodiluted group.     

Subcutaneous blood flow in man during sleep with continuous epidural anaesthesia

Background: Subcutaneous blood flow increases during sleep and we evaluated if this increase is affected by epidural anaesthesia.
Methods: Lower leg subcutaneous blood flow was determined by ¹³³Xenon clearance in ten subjects during continuous epidural anaesthesia at L₂-L₃ including eight hours of sleep, while the upper abdominal subcutaneous blood flow served as control.
Results: Epidural anaesthesia to the level of the umbilicus was followed by an increase in the lower leg subcutaneous blood flow from 3.4 (1.8-6.3) to 7.8 (3.6–16.9) ml min^-1 100 g^-1 (median and range; P <0.001) and returned to 3.5 (2.4–7.6) ml min^-1 100 g^-1 after 88 (45–123) min. In contrast, until the period of sleep the upper abdominal region blood flow remained at 5.2 (3.2–6.4) ml min^-1 100 g^-1. During sleep, lower leg subcutaneous blood flow did not change significantly, but the upper abdominal flow increased to 6.2 (5.2–7.2) ml min^-1 100 g^-1 after 34 (29–70) min ( P <0.01), and it remained elevated for 125 (100–164) min.
Conclusions: The results indicate that although epidural anaesthesia induced only a temporary increase in lower leg subcutaneous blood flow, it hindered the rise in subcutaneous blood flow normally manifest during early sleep.     

Multiple Dose Kinetics of Ketobemidone in Surgical Patients

Twelve patients scheduled for major abdominal surgery were selected for a study of the kinetics of ketobemidone during the day of surgery and in a follow-up study 3–5 days after surgery. In six patients ketobemidone was administered as ketobemidone plain and in the other six, it was given as Ketogin®, a combination formula containing a spasmolytic substance in addition to ketobemidone. Plasma samples were collected for approximately 24 h following induction of anesthesia, during which time multiple doses of ketobemidone were administered. A single-dose study was performed 3–5 days after surgery using the same drug. No significant differences were found between the two formulations of ketobemidone. Plasma clearance did not change significantly between the two periods of study, being 18.0±4.4 ml · kg^-1 · min^-1 peroperatively and 21.7±7.6 ml · kg^-1 · min^-1 postoperatively. Peroperative V_{d area} was significantly larger than post-operative V_{d area}, 5.84±2.621 · kg^-1 and 3.63±0.381 ·; kg^-1, respectively. T1/2 terminal decreased from 3.84±1.6 h peroperatively to 2.06±0.44 h postoperatively.     

Pharmacokinetics and Placental Transmission of Fazadinium in Elective Caesarean Sections

The pharmacokinetics and placental transmission of fazadinium (0.75-0.80 mg kg^-1) were studied in seven pregnant women undergoing elective caesarean section. Plasma levels of the drug were determined by a spectrofluorimetric method and pharmacokinetics were derived according to a 2-compartment open model. Distribution and elimination half-lives averaged 0.07 ±0.03 (t½alpha) and 1.24 ± 0.34 (t½ beta) h; the volume of distribution was 20.75± 5.81 1, and the plasma clearance was 202.33 ± 39.2 ml min^-1 1.73 m². The ratio between umbilical venous blood and maternal blood at delivery ranged from 2.57 to 17.5%. Urinary elimination accounted for 37% of the injected dose within 24 h. It is concluded that because of early good intubating conditions and favourable pharmacokinetics with a modest placental passage, fazadinium might be particularly useful in obstetrics.     

Topographical analysis of the EEG effects of a subconvulsive dose of lidocaine in healthy volunteers

Background: The purpose of the present study was to assess the effects of intravenous lidocaine on spatial changes of electroen-cephalographic power and on psychomotoric status in conscious volunteers.
Methods: In 11 healthy volunteers lidocaine (2-min bolus, 100 mg; 15-min infusion, 40 μg kg^-1 min^-1) or placebo were given intravenously in a randomized, single-blinded, two-way crossover study. Haemodynamics and lidocaine plasma concentrations were measured at baseline and within a period of 30 min following bolus injection. Vigilance and emotional status were tested using visual analogue scales (VAS). Toxic CNS effects were evaluated by a questionnaire. The raw EEG (17 leads, reference C_z) and computed power spectra were continuously recorded.
Results: The chosen lidocaine dosage led to nearly constant plasma concentrations (unbound lidocaine 2.5 min and 15 min after bolus 0.36±0.14 μg/ml and 0.30±0.06 μg/ml, respectively [mean±SD]). The placebo caused no symptoms, changes in VAS-scores or EEG-parameters. Lidocaine induced pronounced subjective symptoms and significant increases in delta activity for 15 min, most dominant at the frontotemporal and occipital leads (max. +219% O₁). Frontal and occipital beta1 and beta2 power (max. +131% and +124% at O₁, respectively) was immediately increased after the bolus injection. No EEG changes occurred at central region C_z, and no interhemispheric EEG differences were noted. Theta, alphal, and alpha2 power remained unchanged.
Conclusion: The current data demonstrate simultaneous changes in psychomotoric status as well as delta and beta spectral power during lidocaine infusion. These data could be an indication that the pronounced frontotemporal and occipital EEG changes are the electroencephalographic expression of subjective sensations.     

The combination of external high-frequency oscillation and pressure support ventilation in acute respiratory failure

Background: Effective gas exchange can be maintained in animals by using external high-frequency oscillation (EHFO). The present study evaluates the effect of relatively long-term duration EHFO combined with pressure support ventilation (PSV) in patients with acute respiratory failure.
Methods: Twelve patients were ventilated with EHFO combined with PSV for 8 h at 60 oscillations min^-1, with a cuirass pressure of 36 cm H₂O: -26 to +10 cm H₂O (27 mm Hg: -19.5 to +7.5 mm Hg) and an inspiratory-to-expiratory ratio of 1: 1. Blood gas values and hemodynamic parameters were measured. Results: Significant increases were noted in cardiac index (3.0±0.7 to 3.2±0.7 1 min^-1 m^-2, P < 0.05) and stroke volume index (32±14 to 35±13 ml m^-2, P < 0.05) without changes in pulmonary artery wedge pressure at 1 h after EHFO. PaO₂(kPa)/FiO₂ and PaCO₂ improved from 21.9±7.5 to 26.8±8.0 ( P < 0.05) at 2 h and from 6.9±1.7 to 6.1±0.9 kPa ( P < 0.01) at 30 min after EHFO, respectively. Breath sounds could be heard well throughout the lung fields after institution of EHFO. The mucous rales also decreased.
Conclusions: As a method of ventilation for patients with acute respiratory failure, EHFO combined with PSV may have potential advantages over conventional mechanical ventilation when drainage of secretions is facilitated. Beneficial effects of EHFO may appear after several hours.     

Determination of Skin Blood Flow by 133Xe Washout and by Heat Flux from a Heated tc-Po2 Electrode

¹³³Xe washout measurements were used to determine cutaneous and subcutaneous blood flow beneath a specially designed double-thermostated tc-Po₂ electrode. The skin blood flow was determined using thermal methods based on reduced heat dissipation during blood flow cessation. A total of 20 measurements were performed on two healthy volunteers, using the volar side of the right forearm as the experimental area. Cutaneous as well as subcutaneous blood flow increased with increasing electrode temperature. The cutaneous blood flow increased from 12.3 ± 1.3 ml (100 g)^-1-min^-1 (37C) to 49.1 ± 5.4 ml (100 g)^-1.min^-1 (45C) and the subcutaneous values from 20.9 ± 0.2 ml (100 g)^-1 -min^-1 to 57.3 ± 0.5 ml (100 g)^-1 -min^-1. Preheating of the measuring area or injection of papaverine as blood flow accelerator did not increase the maximum blood flow values. A considerable inter-individual difference between cutaneous and subcutaneous blood flow was observed, but in spite of that a good overall correlation between the ¹³³Xe washout measurements and the two thermal flow measurements was found (r = 0.932 and 0.945, respectively). It is concluded that in some cases, but not always, measurements of tc-Po₂ at electrode temperatures of 45C take place on a maximally perfused skin and that it is possible to determine skin blood flow by means of determinations of the heat dissipated from the tc-Po2 electrode to the underlying skin.     

Endocrine Stress Response during General and Epidural Anaesthesia for Elective Caesarean Sections

In 17 patients scheduled for elective caesarean sections, the influence of general (GA, n = 9) and epidural anaesthesia (EA, n = 8) on maternal and umbilical vein blood plasma concentrations of ACTH, Cortisol, 17-α-hydroxyprogesterone (OHP) and blood glucose (BG) was studied. Mean blood pressure (MBP mmHg) and heart rate (HR beats min^-1) were also followed during the operation and Apgar scores were evaluated in all neonates. With epidural anaesthesia, an MBP of 102±6.5 mmHg and an HR of 87 ±4.9 beats min^-1 was found at hysterotomy (HT). With general anaesthesia, the corresponding values were 143 ±6.9 mmHg (P<0.01) and 108 ±6.3 beats min^-1 (P<0.05). The plasma concentration of ACTH at HT was higher during GA than during EA (P<0.01), while the plasma concentration of Cortisol during GA was higher 30 min alter HT (P<0.05). Maternal ACTH and Cortisol levels at HT were higher than umbilical vein levels, while OHP was 2–3 times higher in the umbilical vein than in maternal blood at HT. Umbilical vein Cortisol concentration was higher in the EA than in the GA group (P<0.01). With epidural anaesthesia, neonates had higher Apgar scores than with general anaesthesia (P<0.01). The increased umbilical vein Cortisol concentration with epidural anaesthesia challenged the assumption of a higher fetal stress response. The results might have a bearing on the choice of the most suitable anaesthetic method in complicated pregnancies.     

Poikilocapnic hypoxic ventilatory response in humans during 0.85 MAC isoflurane anesthesia

Ventilatory responses to hypoxia (HVR) were investigated using poikilocapnic conditions (i.e. end–tidal CO₂'s allowed to seek it's own level) in 15 cardio–pulmonary healthy patients who were first studied awake and then at 0.85 MAC isoflurane. The influence of hypercapnia (HyperCapnic Ventilatory Response, HCVR) was also elucidated. Pneumotachography, capnography and airway occlusion pressures at 0.1 s (P < u) were used before and during both mild hypoxia (end–tidal O₂ tension 8.7 kPa) and hypercapnia achieved by an inspired CO₂ concentration of 5%. HCVR was attenuated by 60% during anesthesia ( P < 0.01). In the awake state , five of the 15 patients decreased HVR during hypoxia as compared with during normoxia. This resulted in a V_E that on average increased by 0.6 l–min^-1 ( P < 0.05) whereas P_E0₁ was unchanged. In the anesthetized state , no case of decreased HVR was seen and hypoxia induced a mean V_E increase (±s.d.) by 1.0± 0.2 lmin^-1 ( P < 0.001) and a P_E0₁ that on average was improved by 0.63 ± 0.27 cm H₂O ( P < 0.01). It is suggested that when the aim is to evaluate the influence of volatile anesthetic agents on HVR and to quantitate its clinical relevance during and immediately after anesthesia, a poikilocapnic technique should be used. It is concluded that the poikilocapnic HVR to P_F.o₂'s of 8.7 kPa was maintained during 0.85 MAC isoflurane.     

Pharmacokinetics of Pethidine During Anaesthesia and Patient-Controlled Analgesic Therapy

The pharmacokinetics of pethidine has been studied in 12 patients subjected to major intraabdominal surgery. Pethidine and norpethidine were analyzed in plasma samples collected during anesthesia and during patient-controlled administration of small intravenous doses of pethidine in the early postoperative period. A second study on the pharmacokinetics of pethidine was performed on the 3-5th postoperative day. The plasma clearance of pethidine was significantly lower in the peroperative study (8.9±1.8ml·kg·min^-1) compared with the postoperative study (12.0 ±3.1 ml·kg·min^-1). Volume of distribution (Vd) was not significantly influenced, being 4.25±1.72 l·kg^-1 peroperatively and 3.14±0.84 l·kg^-1 postoperatively. Elimination half-life decreased from 5.91 ±3.57 h peroperatively to 3.25 ± 1.40 h postoperatively. The kinetics of pethidine in the postoperative study agreed with pethidine kinetics reported for healthy volunteers. The fraction of unbound pethidine decreased from 0.26±0.1 peroperatively to 0.18±0.1 postoperatively. Norpethidine, a metabolite of pethidine, has been claimed to be responsible for several side effects like respiratory depression and convulsions during pethidine therapy. No side effect attributable to norpethidine was observed in the self-administration period. Norpethidine plasma concentrations did not exceed 500 ng/ml. The altered pethidine pharmacokinetics during anesthesia and the ensuing postoperative hours and the interindividual differences of the disposition of the drug strongly suggest that pethidine should be given by individualized regimens in surgical patients.     

The Effect of Surgical Stress on Haemodynamics During Neurolept Anaesthesia

The influence of surgical stress on haemodynamics during neurolept anaesthesia (NLA) was studied in ten patients, while they were awake, under anaesthesia prior to surgery and peroperatively. Systemic arterial, pulmonary arterial, right atrial and pulmonary capillary wedge pressures, as well as cardiac output (Q_t), arterial oxygen content and mixed venous oxygen content, were measured. Systemic and pulmonary vascular resistances, arterial-venous oxygen content difference (AVD), oxygen consumption (v_o2 and cardiac index (CI) were calculated.
On institution of anaesthesia, CI fell from 2.8 ±.11 /min. m² to 2.5±0.2 l /min.m² and systolic arterial pressure (SBP) fell from 13.4±0.5 kPa to 10.2±0.3 kPa. During surgery CI rose to 3.3±0.1 1/min.m² and SBP rose to 15.7±0.6 kPa. Prior to anaesthesia, AVD was 40.2±0.2 ml/l Under anaesthesia prior to surgery, AVD did not change, but v_O2 declined from 207±13 ml/min to 171±10 ml/min. During surgery, AVD fell to 30.5±0.3 ml/l, while V_o2 remained unchanged.
It is concluded that NLA has a direct metabolic depressant effect and, in association with surgery, is accompanied by hyperkinetic circulation.     

Effect of inotropic stimulation on the synchrony of left ventricular wall motion in a dog model of myocardial stunning

Background: Reperfusion after short coronary occlusion induces regional myocardial dysfunction ("stunning"), including asynchrony of left ventricular (LV) wall motion. Contractile function of stunned myocardium can be increased by inotropic stimulation, but whether this has an influence on wall motion asynchrony is unknown.
Methods: In six anaesthetized dogs, the effect of inotropic stimulation on regional myocardial function, and LV asynchrony was tested after the induction of regional stunning (by 15 min of left circumflex artery side branch occlusion). Regional myocardial function was assessed as mean systolic wall thickening velocity (υ_swt) by sonomicrometry in the stunned (posterobasal wall) and normal myocardium (anteroapical wall), and LV asynchrony by the phase difference (φ) of the first Fourier transform of the wall thickness signals.
Results: In the stunned myocardium, υ_swt decreased from 8.6±1.0 to 1.7±1.4 mm s^-1 (mean±SEM), P <0.01, and simultaneously φ increased from 10.8±3.6 to 85.7±14.3°, P <0.01. Intra-coronary noradrenaline (NADR, 0.25 μg) improved υ_swt (8.3±1.4 mm s^-1, P <0.01) in the stunned region and changed φ to -38.1±18.0°, P <0.05. Systemic NADR (5 μg) also increased υ_swt of the stunned region (to 3.8±2.1 mm s^-1, P <0.05), but left φ unchanged (82.9±19.8°).
Conclusion: Regional function of stunned myocardium can be augmented by inotropic stimulation with noradrenaline, but this does not result in an improvement of LV wall motion asynchrony during systemic inotropic stimulation.     

A comparison of the effects of fentanyl and propofol on left ventricular contractility during myocardial stunning

Background : The intravenous anaesthetic propofol has been shown to possess free radical scavenging activity and calcium channel blocking effects in a number of in vitro models. We decided to compare the effects of propofol with those of fentanyl on myocardial contractility during and after ischaemia to determine whether propofol could protect the heart and improve recovery of ventricular contractile function in open-chested dogs.
Methods : Twenty adult beagles were acutely instrumented, under halothane anaesthesia, to measure ECG; aortic, left ventricular pressures; cardiac output; coronary flow; and segmental lengths in the regions perfused by the left anterior and left circumflex coronary arteries. After surgery and a stabilisation period halothane anaesthesia was terminated and fentanyl (100 μg. kg^-1 bolus followed by 2 μ.kg^-1·min^-1 infusion; n=10) or propofol (5 mg. kg^-1 bolus followed by 0.3 mg· kg^-1 min^-1 infusion; n=10) anaesthesia commenced. After a stabilisation period the LAD coronary artery was occluded for 10 min and then reperfused for 3 h. Measurements were taken throughout the protocol.
Results : We found no significant difference in recovery of contractile function between propofol and fentanyl as assessed by normalised preload recruitable work area (50±10 vs 47±16%), normalised systolic shortening (36±12 vs 48±14%) and peak left ventricular dP/dt (1665±276 vs 1846±151 mmHg.s^-1) at the end of reperfusion.
Conclusion : We conclude that at the concentration used in this study propofol shows no improvement in contractility during "stunning" when compared to fentanyl.