Anaesthetic strategies to reduce perioperative blood loss in paediatric surgery.

In adults, a number of measures to reduce perioperative blood loss have been established. These techniques serve to reduce patients' exposure to homologous blood. Most adults are concerned with this issue especially since many patients became infected with human immunodeficiency virus (HIV) during the 1980s through exposure to blood components. While blood-saving strategies are widely used in adults, they are mostly neglected in infants. However, it is these young patients with their whole life in front of them who, it could be argued, would benefit especially from any potentially avoidable infection (HIV, hepatitis, etc.) or immunological complications. In infants and small children, these blood-sparing techniques may not be as effective as in adults and technical limitations may prevent their application. However, some of these measures can be used and may serve to prevent or reduce exposure to homologous blood. In the following review, blood-saving techniques established in adults are described and their applicability for paediatric patients discussed.

Naloxone prevents increased atrial natriuretic peptide release during regional myocardial ischaemia and stunning in awake dogs.

BACKGROUND: Atrial natriuretic peptide (ANP) release is increased in patients with ischaemic left ventricular dysfunction. A beneficial effect of naloxone on recovery from myocardial stunning was shown previously. The aim of this study was to investigate the effects of naloxone on ANP release during regional myocardial ischaemia and stunning in awake dogs. METHODS: Ten dogs were chronically instrumented for measurement of heart rate, left atrial, aortic, and left ventricular pressure (LVP), LV dP x dtmax/min(-1), and myocardial wall-thickening fraction. An occluder around the left anterior descending artery (LAD) allowed induction of reversible ischaemia in the LAD-perfused myocardium. Each dog underwent two ischaemic episodes (randomized crossover fashion; separate days): 10 min of LAD occlusion (1) after application of naloxone (63 microg kg(-1)), and (2) without naloxone. ANP levels were measured at baseline (BL) and at predetermined time points until complete recovery of myocardial stunning occurred. RESULTS: LAD ischaemia-induced release of ANP (peak level: 182 (30) vs 27 (7) pg ml(-1) BL) only in the control group without naloxone. Between 1 and 180 min of reperfusion, ANP levels were significantly higher only in the control group (P<0.05). CONCLUSION: Pre-ischaemic application of naloxone prevents this ischaemia-induced ANP-release in conscious dogs.

Arteriovenous carboxyhemoglobin gradient is a technical artifact that is eliminated by special calibration (SAT 100).

Pulmonary enzyme heme oxygenase, which catalyses carbon monoxide production, may be responsible for arteriovenous carboxyhemoglobin (COHb) differences measured in humans. Unspecific inflammatory stimuli have been shown to induce pulmonary heme oxygenase possibly leading to increased pulmonary carbon monoxide production and elevated arterial COHb. Arteriovenous COHb gradients may therefore be a measurable parameter of lung injury severity. To exclude a technical artefact, we repeated measurements of central venous COHb and arterial COHb in healthy humans (ASA I-II) undergoing elective surgery with the ABL 625 and the updated version, ABL 725 (Radiometer, Copenhagen). In addition to the standard calibration, an especially accurate adjustment of the spectrophotometer wavelengths (SAT100) was performed. This adjustment eliminates the FCOHb dependency on the oxygen saturation. No significant differences were detectable between central venous and arterial COHb concentrations with either blood gas analyzer. The difference between central venous COHb and arterial COHb was 0.09 with the ABL 625 and -0.03 with the ABL 725. Therefore, we conclude that previously reported arteriovenous COHb differences are artifactual and may be eliminated by SAT 100 adjustment, as is possible with the ABL 725.