J. P. Rasmussen

Effect of methylprednisolone on endotoxemia and complement activation during cardiac surgery

The influence of high doses of methylprednisolone on complement activation and endotoxin concentration was investigated in two groups of eight patients undergoing coronary artery bypass grafting. Group 1 received methylprednisolone, 30 mg/kg, at the induction of anesthesia; group 2 served as the control group. The endotoxin concentrations increased significantly in both groups at the start of cardiopulmonary bypass. During cardiopulmonary bypass, the endotoxin concentrations were significantly higher in the steroid group compared with the control group (p less than 0.01). After completion of surgery, the endotoxin concentrations declined to almost zero within seven days in both groups. Complement activation was significantly reduced in the steroid-treated group during cardiopulmonary bypass compared with the control group (P less than 0.01). The clinical outcome after the first postoperative week was the same in the two groups. It appears that high-dose steroids can reduce complement activation during cardiopulmonary bypass, although the clearance of endotoxins may also be reduced.

Evaluation of Impedance Cardiography as a Non-Invasive Means of Measuring Systolic Time Intervals and Cardiac Output

Impedance cardiography was used for non‐invasive determinations of systolic time intervals (STI) and cardiac output. The results were compared with simultaneously obtained invasive measurements of STI from central aortic pressure curves and of cardiac output using the dye‐dilution technique.

Early Response in Central Hemodynamics to High Doses of Sufentanil or Morphine in Dogs

The hemodynamk effects of high doses of sufentanil, a newly synthetized highly potent analgesic, were investigated in dogs. This study compared the early (30 min) cardiovascular effects of sufentanil 0.01 mg‐ kg‐1 and morphine 4 mg‐kg‐1. Sufentanil caused a moderate and insignificant decrease in mean arterial pressure (MAP). A 30% decrease in cardiac index (CI) was almost outbalanced by an increased systemic vascular resistance (SVRI). The lowering of CI was due to a more than 50% decrease in heart rate (HR) which was partly compensated for by a greater stroke volume index (SVI). In the first 5 min after morphine injection, MAP fell significantly to about 50 mmHg (below 50% of the control value). CI was reduced to about 50% of the control value because of significant decreases in both SVI and HR. The calculated SVRI was unchanged alter morphine. Within 30 min some of the initially changed parameters had returned to control levels. Central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) increased immediately after sufentanil, but decreased alter morphine. With time, both parameters returned towards control values. Peak left ventricular dP/dt decreased by about 25–50% after both analgesics. The rate‐pressure products (RPP) were significantly decreased to less than one half of the control values after both analgesics. Mixed venous oxygen tension (Pv̇o2), oxygen transport and oxygen consumption were significantly lowered in the sufentanil group, whereas immediate decreases after morphine were followed by gradual increases towards control values. We conclude that the use of high doses of sufentanil in dogs is safe. Apart from initial, transient changes, a stable cardiovascular stale characterizes the high‐dose sufentanil anesthesia, while morphine causes fluctuations in several hemodynamic parameters. Compared to morphine anesthesia, sufentanil anesthesia appears to be an attractive alternative which deserves further evaluation in humans.

Effects of Ventilation with Large Tidal Volumes or Positive End-Expiratory Pressure on Cardiorespiratory Function in Anesthetized Obese Patients

The cardiorespiratory effects of ventilation with large tidal volumes (LTV) or positive end‐expiratory pressure (PEEP) were investigated in 10 extremely obese patients during anesthesia for a jejuno‐ileal by‐pass operation.

Postoperative Pulmonary Function in Obese Patients after Upper Abdominal Surgery

The pulmonary course after jejuno‐ileal by‐pass operation in six massively obese patients (mean weight 130.2 kg) was followed for the first 5 postoperative days by means of arterial blood gas analysis and measurements of forced vital capacity (FVC), forced expired volume in the first second (FEV1.0) and peak expiratory flow rate (PEFR). The patients were extubated in the operating room and were breathing spontaneously in the postoperative period. Pao2 and FVC reached their minimum values in the first 24 postoperative hours (respectively, 74% and 45% of their preoperative values), but were almost restored in 5 days. PEFR had at this time reached 77% of its preoperative value. FEV1.0% (FEV1.0 in per cent of FVC) did not change from the pre‐ to the postoperative period, but remained about 70%.

Evaluation of Impedance Cardiography during Anesthesia in Extremely Obese Patients

In three anesthetized markedly obese patients, non‐invasive stroke volumes (the transthoracic electrical impedance method) were compared to simultaneously obtained invasively measured stroke volumes (dye‐dilution method). Close correlations were obtained (r = 0.90‐0.98) between the two methods, although constant lower impedance stroke volumes were found in these patients when the values usually employed for the electrical resistivity of the blood (ζ) were used for calculation of the impedance stroke volume. No statistically significant difference (P> 0.10) between the two methods was found when a ζ of 175 ohm ζ cm was used for the calculations, or when the percentage changes in stroke volumes were analyzed.

Changes in Systolic Time Intervals During Stepwise Increasing Hypoxia

Determinations of the reciprocal value of the square of the pre‐ejection period (1/PEP2) and the pre‐ejection period/left ventricular ejection time‐ratio (PEP/LVET‐ratio) during stepwise increasing hypoxia showed in seven mongrel dogs a decrease in PEP/LVET‐ratio and an increase in 1/PEP2 as an expression of a stimulation of the cardiac function. Significant changes were not observed before the arterial oxygen tension (Pao2) was below 40 mmHg. During severe hypoxia (Pao2 15–20 mmHg), some deterioration in the systolic time intervals occurs with time, but a stimulation persists at the time of death compared to the prehypoxic values.

Transcutaneous Oxygen Measurement During Thoracic Anaesthesia

The value of transcutaneous oxygen tension (tcPO2) as an oxygen parameter during uncomplicated thoracic anaesthesia was examined in ten patients anaesthetized with oxygen‐nitrous oxide and enflurane or flunitrazepam/fentanyl. tcPO2 was measured with the Radiometer TCM‐1® monitor at 45d̀C. Measuring interference due to the anaesthetic agents was not observed. tcPO2 was found to be lower than the arterial oxygen tension (PaO2) at any inspiratory oxygen fraction (FIO2). When the peroperative readings were related to the preoperative values, no statistically significant difference was found between PaO2 and tcPO2 at FIO2 = 0.5, 0.4 and 0.3 (P > 0.3). Linear regression between PaO2 and tcPO2 shows disparity in pre‐ and peroperative regression. tcPO2 (preoperative) = ‐2.2+ 1.03 X PaO2 (r = 0.89), tcPO2 (peroperative) = +3.1 +0.56 X PaO2 (r = 0.87). This disparity indicates a decrease in the tcPO2/PaO2 ratio with increasing PaO2. It is concluded that tcPO2 cannot substitute for PaO2, but tcPO2 and PaO2 proved to be equally useful as oxygen parameters in the examined patients. Interpretation of tcPO2 during anaesthesia, however, necessitates a preoperative measurement as reference.

Peripheral Circulation During Sufentanyl and Morphine Anesthesia

Sufentanyl is a newly developed potent, short‐acting fentanyl‐like morphinomimetic. No independent studies of the peripheral circulation during sufentanyl anesthesia are available. In the present study we compared the effects of sufentanyl and morphine on the peripheral perfusion in dogs. The effects of total β‐blockade during sufentanyl and morphine anesthesia were also evaluated. We elected to record skeletal muscle surface pH (m‐pH) continuously as an index of the microcirculation and cellular function. Arterial and mixed venous blood gases and acid‐base status were measured to determine the respiratory component of changes in m‐pH. Hematocrits, plasma electrolytes and plasma proteins were analyzed in order to permit calculations of fluid‐shifts between the blood and the interstitial fluid. Sufentanyl (0.01 nig/kg) had no adverse effects on the peripheral perfusion. Morphine (4 mg/kg) caused a severe and rapid fall in m‐pH from 7.29 to 7.11 during the 30‐min experimental period. At the same time, calculated blood volume decreased by 20%. This hypovolemic deterioration of the circulation was probably caused by a histamine‐mediated increase in capillary pressure with filtration of plasma from the circulation to the interstitial fluid.

Pulmonary function in obese patients scheduled for jejuno-ileostomy.

Preoperative pulmonary parameters were evaluated in 37 extremely obese but otherwise healthy patients. They were on average 100.9% overweight. X‐ray of the chest, electrocardiograms, and residual volume, vital capacity, total lung capacity, maximum breathing capacity, forced expired volume in 1 second, and related ratios were all within the normal range. The alveolar‐arterial oxygen gradient and the arterial carbon dioxide tension were also within the normal range. The only abnormal finding was a substantially reduced arterial oxygen tension.