P. K. Andersen

Postoperative Pain Treatment after Upper Abdominal Surgery with Epidural Morphine at Thoracic or Lumbar Level

Thirty patients undergoing upper laparotomy were entered into a randomized trial, comparing the effect of midthoracic (T) and lumbar (L) epidural morphine on postoperative pain and pulmonary function. Five mg morphine was injected through the catheter at the end of the operation, and subsequently three times a day. Six, 30 and 54 h postoperatively, the following tests were performed: linear analogue pain score, arterial gas tensions (PaO2, PaCO2 and pH), forced ventilatory capacity (FVC), forced expiratory volume in 1 s (FEV1) and peak expiratory flow rate (PEF). The changes in pain score (increase of the median): T: 21, 6, 5, and L: 24, 15, 8 per cent of full scale), PaO2 (decrease of the tension: T: 1.7, 2.1, 2.4, and L: 2.0, 2.8, 2.0 kPa), PaCO2, pH, FVC (decrease of the volume: T: 1.3, 1.1, 0.9, and L: 1.3, 1.3, 1.2 1). FEV1 and PEF from the preoperative tests were not significantly different. It is concluded that the clinical effect of epidural morphine for postoperative pain treatment is the same or little different whether the administration takes place at the thoracic or lumbar level.

Sodium nitroprusside and epidural blockade in the treatment of ergotism.

The treatment of vasospasm during ergotism has been difficult and unconvincing.1 2 3 A combination of hyperbaric oxygen and sympathetic blockade by means of continuous epidural anesthesia has been ...

Acid—Base Interactions with Noradrenaline-induced Contractile Response of the Rabbit Isolated Aorta

The effect of acidosis and alkalosis on vascular smooth muscle contractions evoked by noradrenaline was studied. Helical strips of rabbit aorta were mounted for isometric tension recording. Acidosis (pH 7.24–6.51) was obtained by either increasing the Pco2 (hypercapnic) and/or lowering the HCO3-concentration (hypobicarbonatic). Acidosis shifted the noradrenaline concentration-response curve to the right in a competitive manner. The maximal developed tension was unchanged at pH 7.24–6.90 and decreased by 30% at pH 6.51. Alkalosis (pH 7.61–8.04) did not alter nor-adrenaline-evoked contractions. The results suggest that hydrogen ions during acidosis (pH < 7.40) but not during alkalosis (pH > 7.40) exert α-adrenoceptor blocking properties.

Changes in circulating blood volume after infusion of hydroxyethyl starch 6% in critically ill patients

Background: The cardiovascular response to a volume challenge with hydroxyethyl starch (HES) (200/0.5) 6% depends on the relation between the volume of HES 6% infused and the expansion of the blood volume in critically ill patients. However, only relatively limited data exist on the plasma expanding effect of infusion of HES 6% in critically ill patients. The purpose of the study was to evaluate the variation in the expansion of the circulating blood volume (CBV) in critically ill patients after infusion of 500 ml of colloid (HES (200/0.5) 6%) using the carbon monoxide method.

The reproducibility of measurement of right ventricular ejection fraction and cardiac output by the thermodilution technique in patients on mechanical ventilation

Thermodilution determined right ventricular ejection fraction (RVEF) and cardiac output (CO) were measured in 48 critically ill patients requiring mechanical ventilation and inotropic and/or vasoactive drugs. The coefficient of variation on CO and RVEF were calculated from triple determinations. The average coefficient of variation based on 551 triple determinations was 12.6% for RVEF (range 2–51%) and 4.9% for CO (range 0–24%). If a 10% coefficient of variation was chosen as acceptable, 95% of the CO measurements were acceptable. The coefficient of variation on RVEF only fulfilled the 10% criteria in 46% of the measurements, but if the accepted level was raised to a 20% coefficient of variation, 90% of the measurements were acceptable. The measurement of RVEF and CO are used for calculation of e.g. right ventricular end diastolic volume (RVEDV). By applying the average coefficient of variation on RVEF and CO, the accumulated error on calculation of RVEDV was found to be 15%–+20% at worst. Before derived parameters such as RVEDV are interpreted or compared with previously obtained values, the accumulated error should be calculated. To ensure the quality of the measurements, our recommendation is always to calculate the coefficient of variation for each triple determination of RVEF and CO.

Arterial Carbon Dioxide Tensions during Anaesthesia with Manual Ventilation A Descriptive Study of the Effects of Various Non-Polluting Circuits

In 660 supine, intubated and anaesthetized, healthy patients scheduled for various elective surgical procedures, the distribution of arterial carbon dioxide tension (Paco2) was investigated during manual non‐monitored ventilation. The study comprised six equal groups: group I: ventilation with a circle circuit absorber system; group 2: ventilation with the Hafnia A circuit using a total fresh gas flow (FGF) of 100 ml.kg‐1 min‐1; groups 3–6: ventilation with a Hafnia D circuit with fresh gas flows of 100, 80, 70 and 60 ml.kg‐1 min‐1, respectively. The mean Pacos of the first three groups were situated in the lower range of normocapnia (the observations in the first group having the greatest total range), whereas the rebreathing (Hafnia A and D) circuits resulted in a clustering of observed data. Employing the rebreathing circuits, protection against hypocapnia can be achieved by lowering the fresh gas flow. The most satisfying result was obtained with the Hafnia D circuit with a fresh gas flow of 70 ml.kg‐1 min‐1, resulting in normocapnia with a modest and limited spread towards hypo‐ and hypercapnia. FGF in excess of this level must be considered as wasted. The study indicates that corrections of fresh gas flows for age are superfluous. Use of relaxants and type of surgery had no influence on the observations.

Spectral analysis of cyclic fluctuations in haemodynamic parameters in critically ill patients

In critically ill patients haemodynamic parameters are being routinely monitored. All of the fluctuations in blood pressures cannot be visualised since on most monitors the time window is too short and trend curves do not have a sufficient time resolution. Therefore, frequency analysis was applied to an 800-second window. Systemic artery pressure, central venous pressure and pulmonary artery pressure curves of 6 patients were sampled with a frequency of 40 Hz. The signals were transformed into the frequency domain by the Fast Fourier Transform method. Bispectral analysis was applied to determine the origin of higher frequencies. There were three main frequencies present: heart stroke rate, respiratory frequency and a slow frequency (<0.05 Hz), which was equal to the used infusion rate (2–10 ml/h) of vaso-active drugs. Continuous infusion of short-acting vaso-active drugs delivered by pulsatile diaphragm pumps to produce slow significant fluctuations in especially the arterial blood pressures (range: 5–40 mmHg). The periodicity of these slow fluctuations is not visualised during routine monitoring, so the observer may misinterpret the cause of changes in blood pressure and make inappropriate clinical decisions. A solution for detection of such slow waves is Fast Fourier Transform combined with bispectral analysis.

pH in physiological salt solutions: direct measurements

Calculations of pH in modified Krebs solutions by inserting Pco2 and total‐CO2 in the Henderson‐Hasselbalch (H.‐H.) equation are obvious as the equation originally served for this purpose. An exact calculation of the relation between pH and Pco2 is complicated as the concentration of bicarbonate, the dissociation constant and the solubility of CO2 change. Furthermore, the dissociation constant in the H.‐H. equation is constant only if activities are used in the equation instead of stoichiometric concentrations. We therefore investigated the influence of different carbon dioxide tensions and bicarbonate concentrations on directly measured pH of organ baths aerated with mass‐spectrometric analyzed O2‐CO2 gases. For reference precision buffers were used. The measured pH values differed distinctly from calculated pH values in the acidic and alkaline parts of the pH interval investigated (6.57–8.15). Measurements of actual pH with proper calibration standards therefore seem mandatory.

Carbon dioxide distribution in Mapleson A and D systems: an experimental study

The distribution of CO2 in the Mapleson A and D rebreathing systems was investigated experimentally during controlled ventilation and with the expiratory valve closed during inspiration. Maximal and minimal levels of CO2‐concentration obtained from capnograms along the tubing were used to construct “gas profiles”. For both systems, high tidal volumes and low fresh gas flows resulted in a high degree of gas separation with a pool of alveolar gas near the expiratory valve, and longitudinal gas mixing was minimal. In this manner fresh gas loss was prevented and fresh gas utilization optimized. The end of the tubing nearest the patient was found to act as a reservoir for alveolar gas in the Mapleson A system and fresh gas in the Mapleson D system. Fresh gas utilization in the Mapleson D system was somewhat less efficient than in the Mapleson A system due to the fresh gas admixture to exhaled alveolar gas in the patient‐near end of the tubing during expiration. The replacement of the usual expiratory valve of the Mapleson A system by a valve which is closed during inspiration makes the A system an alternative to the D system for controlled ventilation.

Carbon dioxide tensions in physiological salt solutions: direct measurements.

Carbon dioxide tensions were measured directly in organ baths and a tonometer aerated in parallel with 6 different gas mixtures of O2 and CO2, 3 gas flows, 3 equilibration periods, and 3 bicarbonate concentrations. The measured partial pressure of carbon dioxide differed systematically from expected values, probably due to errors in the carbon dioxide measurement system. In conclusion, carbon dioxide equilibrates with the bubbling gas in the baths as well as in the tonometer to an almost perfect equilibration.