Amniotic fluid embolus.

A case report of a 27-yr-old healthy patient for Caesarean section under epidural anaesthesia is presented. The patient suffered an acute cardiorespiratory collapse when the infant's head was being delivered through the anterior abdominal wall. The patient remained cyanosed after proper tracheal intubation and pulmonary ventilation with 100% O2. Hypotension was difficult to treat but returned to normal 25 min after the event. A pulmonary artery catheter inserted three hours after the event showed normal pressures and a high cardiac output. The patient suffered permanent neurological damage. The differential diagnosis is discussed and current concepts of the aetiology and management of amniotic fluid embolism reviewed.

MAO inhibitors and coronary artery surgery: a patient death.

The mechanisms of action of monoamine oxidase inhibitors (MAOIs) suggest that patients taking them may respond with hyper- or hypotension when undergoing coronary artery surgery. We describe a case where MAOIs were present and fentanyl and midazolam were the anaesthetic agents used. The anaesthesia and surgery were performed without incident. Postoperative ICU care was complicated by hypertension, hyperthermia, and severe shivering followed by hypotension resistant to therapy and finally death. Diagnoses of pulmonary embolism and sepsis were unproven and may have played a role. The MAOIs may also have played a role. Reactions in patients while taking both meperidine and MAOIs are unusual and animals react differently from humans to a combination of MAOIs and narcotics. There are only five reported cases where fentanyl was given to patients on MAOIs. We conclude that, until there is more information, MAOIs should be discontinued, if possible, before surgery in which catecholamines may be needed.

Pulmonary pressures at high flows in the intact pulsatile flow perfused lung.

Pulmonary pressure-flow curves can be easily generated in the intact animal by using a combination of systemic arteriovenous (a-v) fistulas and inferior vena cava (IVC) occlusion. By combining this technique with pulmonary artery occlusion, pulmonary pressure-flow curves may be studied over a broader range of pressures than has been previously been done in the intact, resting animal using pulsatile flow. Pressure-flow curves were generated by varying flow through opening and closing of the a-v fistulas in conjunction with inflating and deflating a balloon in the inferior vena cava. The pressure-flow curves were done under two conditions; (1) with both lungs perfused; (2) with the right lung excluded from the circulation (PA occlusion). PA occlusion resulted in no change in alveolar arterial oxygen tension gradient. The pressure-flow relationships for one lung and two lungs were well described by linear equations (r2 = 0.83 +/- 0.03 and 0.82 +/- 0.04 respectively). The slope of the equations increased with PA occlusion (3.6 +/- 0.4 mmHg.L-1 to 5.9 +/- 0.9 mmHg.L-1). There was no change in the pressure axis intercept with PA occlusion (8.34 +/- 0.8 mmHg pre-occlusion and 8.9 +/- 1.3 mmHg post-occlusion). It is concluded that the pulmonary pressure-flow relationship is well described by a linear function above a mean pulmonary artery pressure (PAP) of 10-12 mmHg.

Meperidine to control shivering associated with platelet transfusion reaction.

Shivering may be part of a febrile non-haemolytic reaction to blood product transfusion. Shivering can increase oxygen consumption up to 500 per cent which may be detrimental to patients with decreased myocardial reserve. A case is presented of a reaction to platelet transfusion characterized by shivering, tachycardia and hypertension in a patient with a recent myocardial infarction in whom the metabolic and haemodynamic effects were considered to be potentially disastrous. Intravenous injection of meperidine was rapidly effective in treating these changes.

Effects of emboli, positive-pressure ventilation, and airway water on lung water measurements.

We tested the effects of microemboli, continuous positive-pressure ventilation (CPPV), and aspirated airway water on measurements of extravascular lung water by use of the technique of thermal indicator dilution (ETVL). A control group of dogs and a group of dogs in which dextran was infused created all levels of pulmonary edema. In an emboli group 0.125 g/kg of starch microemboli (63-74 micron diam) were infused. In groups with emboli and CPPV, starch emboli were infused and CPPV was then applied at 15 cmH2O. In an airway saline group measured amounts of saline were poured into the airway. In all groups postmortem pulmonary extravascular tissue weight (PETW) was determined and compared with the last ETVL. Emboli created an increased scatter when the last ETVL is compared with PETW because 1) blood trapped distal to emboli was included in the ETVL measurement, and/or 2) diffusion limitations for the thermal indicator were exceeded. Emboli and CPPV decreased ETVL/PETW. Airway saline (80 +/- 5%) was measured by ETVL. In conclusion, the ETVL technique is reliable in well-perfused lungs but loses accuracy in measuring lung water after emboli of any size or with large amounts of airway fluid.

Critical incidents detected by pulse oximetry during anaesthesia.

The Critical Incident Technique was used to study anaesthetics given in a major tertiary care teaching hospital in order to define indications for monitoring with a pulse oximeter during anaesthesia. Anaesthetists were asked to use a pulse oximeter in every case and trained to report Critical Incidents in order to determine if the oximeter can shorten the time to detection of these events. Four thousand seven hundred and ninety-seven anaesthetics were given during a four-month period in 1986-87. A Critical Incident was recorded when an unexpected physiologic deterioration requiring intervention by the anaesthetist to prevent a likely bad outcome was signalled first by the pulse oximeter. Critical Incidents were classified by patient characteristics, physiologic change, type of anaesthetic, and the type, length, and place of surgery. Reports were received in 65 per cent of cases, and a Critical Incident occurred in 191 (six per cent) of these. Desaturation was the commonest physiologic change (151) and was further classified as to severity (mild 85-94 per cent saturation, moderate 75-84 per cent, and severe 75 per cent). Desaturations during the maintenance phase of anaesthesia were milder but more frequent than those in the induction or emergence phases. There were no severe desaturations in elderly patients or those receiving regional anaesthesia. No group was free of Critical Incidents. Since undetected hypoxaemia may lead to disastrous complications we recommend that a pulse oximeter be used for every anaesthetic.

Effect of cardiac output on extravascular lung water measurements made with the thermoconductivity method.

The authors tested the effects of injectate temperature and of changing cardiac output on the measurement of lung water by the thermoconductivity technique (ETVL). Cardiac output in dogs was increased and decreased with isoproterenol and halothane, respectively. Post mortem extravascular lung water (pulmonary extravascular tissue weight [PETW] was determined using a weighing technique. Cardiac output varied between 0.7 and 8.8 l/min and did not influence the ETVL measurement. The authors conclude ETVL measured by the thermoconductivity technique is not influenced by large changes in cardiac output.

The effects of dobutamine, nitroprusside, or volume expansion on cardiac output and lung water after CPPV.

Pulmonary microemboli can create an ARDS-like state in dogs (high pulmonary vascular resistance, pulmonary oedema and arterial hypoxemia). CPPV can correct the hypoxemia of pulmonary microemboli but reduces cardiac output (Q) and tissue oxygenation. This paper compares the effect of improving Q by infusing volume, reducing afterload, or increasing myocardial contractility. Four groups of seven dogs were studied. All had 0.125 g . kg-1 of starch microemboli (63-74 microns) infused and then CPPV at 15 cm H2O applied. The control group had no further treatment applied. In three other groups volume (dextran) or dobutamine or nitroprusside (NTP) was infused to return Q to the level before CPPV was applied. All treatments (volume, dobutamine and NTP) improved Q and O2 transport. Only the volume group had a significant increase in pulmonary microvascular pressure, Pmv = PLA + 0.4 (PPA - PLA) from 2.53 +/- 0.27 to 3.35 +/- 0.13 kPa, p less than 0.05. Only the volume group demonstrated a significant increase in lung water above (double) the control group as measured by a double indicator dilution technique (ETVL) and post mortem lung weights. We conclude volume infusions to improve a CPPV depressed Q may increase lung water and that better treatment would be to infuse NTP or dobutamine, thus maintaining a lower Pmv and therefore lung water. As a corollary the least CPPV should be applied to maintain adequate oxygenation and create the least need for interventions to improve Q.

Effect of continuous positive-pressure ventilation on oxygenation after pulmonary microemboli in dogs.

We infused starch microemboli (63 to 74-mu diameter) into the external jugular vein of 28 dogs, to observe the effects of continuous positive-pressure ventilation (CPPV) on gas exchange and hemodynamics during hypoxemia (PaO2 53 +/- 3 torr). CPPV at both 10 and 15 cm H2O end-tidal pressure improved PaO2. CPPV 15 returned PaO2 and pulmonary shunt to control values but reduced cardiac output, O2 transport, and O2 consumption. In spite of these changes suggesting inadequate tissue oxygenation with CPPV 15, mixed venous oxygenation was not reduced. We conclude that: (a) hypoxemia after microemboli infusion is improved by CPPV and therefore likely caused by ventilation/perfusion abnormalities; (b) the improvement in PaO2 produced by CPPV after microemboli is not beneficial if CPPV reduces perfusion and O2 transport; and (c) mixed venous oxygenation does not appear to be an adequate measure of oxygen transport to tissues when CPPV is applied in this high pulmonary vascular resistance setting.

Lung water increases with fluid administration during CPPV after pulmonary microembolization.

Hypoxemia created by pulmonary microemboli is improved by continuous positive-pressure ventilation (CPPV) but at a cost of reducing cardiac output (Q). In this high pulmonary vascular resistance (PVR), pulmonary edema setting, the authors attempted to increase the Q, which had been reduced by CPPV, with an infusion of dextran. In 14 dogs, 0.125 g/kg of starch microemboli (63-74 microns in diameter) were infused. CPPV at 15 cm H2O then was applied and PaO2 increased from 53 +/- 4 to 69 +/- 3 mmHg, but Q decreased from 2.9 +/- 0.2 to 1.7 +/- 0.2 1/min. Seven of these dogs (control group) were monitored for 3 h. In the remaining seven dogs (volume group), dextran 40 was infused until Q returned to pre-CPPV values, and monitoring was continued for 3 h. With return of Q to pre-CPPV levels, indices of tissue oxygenation (O2 transport, PVO2, O2 consumption and metabolic acidosis) were significantly improved. However lung water was increased significantly by the volume infusion, so that at 3 h lung water in the volume group was double the value in the control group. The authors conclude that volume infusion in the face of a high PVR may correct the reduced Q of CPPV and improve tissue oxygenation, but it also may increase pulmonary edema.

Dynamic triquetrolunate instability: case report.

A case is reported that demonstrates dynamic triquetrolunate instability with the additional finding of obstruction to smooth intercarpal motion by a tag of torn interosseous triquetrolunate ligament. The patient was successfully treated with excision of the ligamentous tag accompanied by triquetrolunate fusion.