Jørgen Eriksen

Observations on Long Bone Medullary Pressures in Relation to Arterial Po2, PCO2 and pH in the Anaesthetized Dog

To investigate the influence of variations in arterial oxygen tensions (PaO2), arterial carbon dioxide tensions (PaCO2), and arterial pH on long bone medullary pressures, seven anaesthetized dogs were investigated. Comparing the control medullary pressures, i.e. the mean medullary pressures obtained at the normal range of PaO2 (75--110 mmHg) with the mean medullary pressures corresponding to the range of PaO2 of less than 75 mmHg, statistically significant (P less than 0.05) decreases were seen in both epiphyseal, metaphyseal and diaphyseal medullary pressures, from 27.6 +/- 5.0 to 15.5 +/- 3.6 mmHg, from 23.5 +/- 2.9 to 13.9 +/- 2.3 mmHg and from 27.7 +/- 3.9 to 18.3 +/- 2.5 mmHg (all mean values +/- s.e. mean), respectively. Hyperoxia, hypocapnia, hypercapnia or metabolic acidosis had no effect on medullary pressures in any of the regions studied.

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.

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%.

Observations on Long Bone Medullary Pressure in Relation to Mean Arterial Blood Pressure in the Anaesthetized Dog

To study the influence of variations in mean arterial pressures (MAP) on long bone medullary pressures, seven anaesthetized dogs were investigated. The medullary pressures were measured in the epiphyseal, the metaphyseal and the diaphyseal regions and remained rather constant when MAP was above 80 mmHg. Below this level of MAP a statistically significant (P less than 0.01) reduction of the medullary pressures was seen. Comparing the mean medullary pressures obtained with ranges of MAP of 81--100 mmHg (the control medullary pressures) and of 61--80 mmHg, the greatest decline was seen in the epiphyseal and the diaphyseal regions, from 25.2 mmHg to 8.1 mmHg and from 26.7 mmHg to 8.3 mmHg, respectively. The corresponding decrease in the metaphyseal region was from 18.9 mmHg to 10.9 mmHg. The mean values of intraosseous pressure measured by our technique were between 20--30 mmHg and this is in accordance with measurements in normal humans found by other authors.

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.

Postanaesthetic postural stability following thiopental or propanidid anaesthesia.

Using a quantitative Romberg‐test performed on a computerized force‐plate‐system, postural stability was tested in 39 patients before and 3 hours after general anaesthesia with either thiopental (20 patients) or propanidid (19 patients).

Relationships Between Oxygen and Carbon Dioxide Tensions and Acid-Base Balance in Arterial Blood and in Medullary Blood from Long Bones in Dogs

By means of an invasive technique the relations between arterial and medullary gas tensions PO2 and PCO2), and arterial and medullary acid-base balance (pH and standard bicarbonate) were determined in long bones in seven anaesthetized dogs. A semilogarithmic correlation was found between the arterial oxygen tension and the oxygen tension in the medullary blood. Between the arterial carbon dioxide tension and the medullary blood carbon dioxide tension a linear correlation was demonstrated A linear correlation was also found between arterial pH and standard bicarbonate values and the corresponding values obtained from medullary blood. With regard to the parameters investigated no difference was demonstrated between epiphyseal, metaphyseal or diaphyseal medullary blood.

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.

Alfentanil and Skeletal Muscle Circulation, Oxygen Consumption and P50

The preservation of blood flow to skeletal muscles has low priority in the intact organism. If cardiovascular function is disturbed, for example by anesthetic drugs, skeletal muscle circulation diminishes or stops. Skeletal muscle surface pH (m‐pH) is a sensitive indicator of muscle cell oxygenation and a fall in m‐pH therefore provides an early warning of deterioration in overall cardiovascular performance. In the present study we investigated the peripheral effects of a new short‐acting fentanyl derivative, alfentanil. Twelve dogs were anesthetized with a bolus injection of alfentanil 0.16 mg‐kg‐1 i.v. M‐pH was recorded continuously, while total body oxygen consumption, oxygen transport and P50 were calculated. No changes were found. In the second part of the study, we pretreated six of the dogs with the “calcium antagonist” verapamil 0.5 mg‐kg‐1, while the other six dogs served as controls. After a rechallenge dose of alfentanil, we again found the peripheral perfusion sufficient to meet the oxygen demand of the muscles. Side‐effects to alfentanil were a decrease in Pao2, due to an increase in pulmonary shunting of venous blood, and an increase in Paco2. The changes in pulmonary ventilation‐perfusion relationships were, however, not of a magnitude that should cause concern when alfentanil is used in normal subjects.