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The in vivo effects of Diaspirin Crosslinked Hemoglobin (DCLHb, Baxter Healthcare Corp.) on hematology and biochemistry are unknown. This study includes 6 calves (71.2±1.3 kg). In each animal a total of 2 litres of blood was exchanged for the same amount of hydroxylethyl starch (Haes, Fresenius) (n=3) or DCLHb (n=3), which is equivalent to 28cc/kg of blood substitute, over a period of 5 hours. The animals were allowed to survive 7 days. Blood samples were taken hourly during the perfusion protocol, at postoperative day (POD) 1, 2 and 7. ANOVA test was used for repeated measurements. Blood cell profiles were similar in both groups. Peak methemoglobinemia was 4.2% in the DCLHb group. Osmolarity was significantly higher in the DCLHb group with the greatest difference at POD 1 and 2. Postmortem analysis of the major organs did not show any sign of hemoglobin deposit in the DCLHb group. In the given setup DCLHb can be administered in a large quantity with good hematological tolerance and without any deposits in major organs. A prolonged plasma expander effect was observed. (Int J Artif Organs 2000; 23: 119–24)

Apnoeic oxygenation (AO) combined with extracorporeal CO2removal (ECCO2R), using venovenous perfusion across a membrane area of 0.1m2has been shown to be feasible in six healthy anaesthetized rabbits. In a further twelve rabbits, ECCO2R has been randomly compared with conventional mechanical ventilation (CMV) following saline lavage to induce respiratory failure. Blood gases were maintained for up to 6h within the same range (PaO2=8–20 kPa, PaCO2=4–6 kPa) in two groups of six by varying airway pressures and the oxygen fraction delivered either to the membrane lung (ECCO2R group) or to the ventilator (CMV group). The influence of single hourly sustained inflations (SI) on oxygenation was studied. ECCO2R subjects remained stable and survived. CMV subjects deteriorated and had 80% mortality. Hyaline membranes were absent from ECCO2R subjects and present in all CMV subjects. The response to SI suggests that a lung volume recruitment is maintained during AO for up to 1 h but is ineffective during CMV.

The effect of clonidine on intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), heart rate (HR), and drug requirements was studied in 24 patients scheduled for elective cerebral tumor resection (ICP ≤20 mm Hg). The patients were randomly assigned to one of two groups: Group P (placebo), 12 patients; Group C (clonidine 3 μg/kg 10 min before induction), 12 patients. In all patients, anesthesia was induced with a propofol infusion (500 μg/kg/min) combined with fentanyl 2 μg/kg, lidocaine 1.5 mg/kg, and vecuronium 0.1 mg/kg. Propofol was also used for maintenance. During the preinduction period, clonidine had no effect on ICP or HR, but in clonidine-treated patients, MAP and CPP decreased significantly in comparison to those of the placebo group. During induction, ICP and HR were stable and similar in both groups. MAP and CPP remained significantly lower in Group C. At intubation and Mayfield clamp application, ICP increased in both groups, with similar values at all times. MAP increased in both groups at intubation, Mayfield clamp application, and incision, staying lower, however, in Group C. CPP followed a pattern similar to that of MAP. Propofol requirements up to the 20th min were lower in Group C than in Group P (2.08 ± 0.83 vs. 3.3 ± 0.7 mg/kg, p< 0.05). Finally, throughout the study, eight patients in Group C versus two in Group P had a CPP value <60 mm Hg for ≥1 min (p <0.05). In contrast, eight patients in Group P, but only one in Group C, had a CPP >110 mm Hg. In conclusion, in normotensive neurosurgical patients with a baseline ICP ≤20 mm Hg, clonidine had no effect on ICP or HR. It decreased MAP and CPP to lower values than those recorded in the placebo group throughout the study without altering the increase in these variables after intraoperative noxious stimulation. Therefore, it would seem that an appropriate use of clonidine would be in the patient in whom MAP control is otherwise difficult despite relatively high doses of anesthetic agents.

The cardiorespiratory effects of three different patterns of mechanical ventilation were compared in sixteen anaesthetized goats. Intermittent positive pressure ventilation (IPPV), with an inspiratory: expiratory (I:E) time ratio of 1∶3, was compared with an inspiratory hold pattern (IPPVH), with an I:E ratio of 3∶1, and with continuous positive pressure ventilation (CPPV) adjusted to produce the same mean airway pressure. In eight animals with normal lungs, IPPVH reduced VD/VTand PaCO2, but produced no changes in oxygenation. CPPV did not significantly alter the efficiency of gas exchange. In a further eight animals, with oleic acid-induced lung damage, both IPPVH and CPPV produced a decrease in both VD/VTand PaCO2. Qs/Qt was significantly reduced by both CPPV and IPPVH, but the effect was more marked with CPPV, and the PaO2was significantly increased only by CPPV. The increased effectiveness of CPPV in increasing PaO2in this model may have been due to the greater increase in endexpiratory lung volume produced by this pattern of ventilation.

Summary In acute postoperative respiratory failure, the following pathophysiological mechanisms are involved: an interstitial pulmonary edema secondary to an increased capillary permeability and/or increased hydrostatic pressure; changes in mechanics and expansion of the thorax and the diaphragm as a consequence of surgery; specific postoperative factors such as impaired defense mechanisms and ciliary movements, as well as metabolic changes due to protein catabolism and artificial nutrition. The consequences are restrictive pulmonary changes, ventilation/perfusion mismatch, retention of bronchial secretions, increased work of breathing, formation of atelectasis and superinfection.

In this report we present the case of a 77-yr-old man who underwent resection of the upper lobe of the left lung for a carcinoma, six weeks after percutaneous transluminal coronary angioplasty (PTCA) with stenting of the left anterior descending (LAD) and circumflex coronary arteries. Antiplatelet therapy with clopidogrel was interrupted two weeks before surgery to allow for epidural catheter placement and to minimize haemorrhage. The surgical procedure was uneventful. In the immediate postoperative period, however, the patient suffered severe myocardial ischaemia. Emergency coronary angiography showed complete thrombotic occlusion of the LAD stent. In spite of successful recanalization, reinfarction occurred and the patient died in cardiogenic shock. Prophylactic preoperative coronary stenting may put the patient at risk of stent thrombosis if surgery cannot be postponed for three months. In such cases, other strategies such as perioperative β-blockade for preoperative cardiac management should be considered. Br J Anaesth 2004; 92: 743–7

The central nervous and cardiovascular effects of midazolam 0.15 mg kg−1 were studied in 20 healthy, unpremedicated volunteers (10 male and 10 female). No important side-effects were noted and the venous tolerance to midazolam was excellent. Three minutes after injection mean systolic arterial pressure decreased from 121±(SEM) 2 mm Hg to 115±(SEM) 2 mm Hg and diastolic pressure from 78±2 to 70±2 mm Hg (P <0.05), and these effects persisted for at least 20 mm. Heart rate increased from 77±4 beat mm−1 to 90±3 and 88±3 beat mm−1 1 and 3 mm after the injection (P <0.05). Anterograde amnesia (40±3 min duration) and drowsiness (lasting 128±23 mm) were observed in all subjects. Loss of the eyelash reflex and apnoea were observed more often in the male group than in the female subjects. Midazolam 0.15 mg kg−1 was not sufficient to induce anaesthesia reliably in healthy unpretnedicated volunteers.