Central cardiovascular and oxygen variables during haemorrhage in the pig

Background: We evaluated the ability of the standards issued by the Danish Society of Anaesthesiologists to reflect a blood loss.
Methods: In 9 pigs bled (0–24 ml kg^-1) and retransfused (to 28 ml kg^-1) during halothane anaesthesia, central cardiovascular, thoracic electrical impedance (TI), oxygen, acid-base and temperature variables were recorded.
Results: With the recommendation for minor surgery (mean arterial pressure (MAP) and heart rate (HR)), the correlation to the blood loss was 0.74 ( P < 0.001) and with that for major surgery (MAP, HR, central venous pressure (CVP) and rectal temperature (Temp_r)) it was 0.79 ( P < 0.001). With the recommendation for extensive surgery (MAP, HR, CVP, pulmonary artery catheter variables and the central-peripheral temperature difference (ΔTemp_r-t)), the correlation was 0.84 ( P < 0.001). Non-invasive monitoring (MAP, HR, ΔTemp_r-t TI and near-infrared spectroscopy of the brain (S_invosO₂)) was only slightly better than basal monitoring (r=0.76, P < 0.001). However, adding arterial base excess (BE), TI and peripheral temperature (Temp_t) to the recommendation for major surgery resulted in a correlation of 0.87 ( P < 0.001), while adding BE and TI to the recommendation for extensive surgery raised correlation to only 0.88 ( P < 0.001).
Conclusion: When the recommendations were followed the correlation to the blood loss ranged from 0.74–0.84. However, with the recording of MAP, HR, CVP, ΔTemp_r-t, BE and TI a correlation of 0.87 was achieved, indicating that a pulmonary artery catheter may not be in need for patients undergoing surgical procedures with expected haemorrhage.     

Middle cerebral artery blood velocity depends on cardiac output during exercise with a large muscle mass

We tested the hypothesis that pharmacological reduction of the increase in cardiac output during dynamic exercise with a large muscle mass would influence the cerebral blood velocity/perfusion. We studied the relationship between changes in cerebral blood velocity (transcranial Doppler), rectus femoris blood oxygenation (near-infrared spectroscopy) and systemic blood flow (cardiac output from model flow analysis of the arterial pressure wave) as induced by dynamic exercise of large (cycling) vs. small muscle groups (rhythmic handgrip) before and after cardioselective β₁ adrenergic blockade (0.15 mg kg^?1 metoprolol i.v.). During rhythmic handgrip, the increments in systemic haemodynamic variables as in middle cerebral artery mean blood velocity were not influenced significantly by metoprolol. In contrast, during cycling (e.g. 113 W), metoprolol reduced the increase in cardiac output (222 ± 13 vs. 260 ± 16%), heart rate (114 ± 3 vs. 135 ± 7 beats min^?1) and mean arterial pressure (103 ± 3 vs.112 ± 4 mmHg), and the increase in cerebral artery mean blood velocity also became lower (from 59 ± 3 to 66 ± 3 vs. 60 ± 2 to 72 ± 3 cm s^?1; P < 0.05). Likewise, during cycling with metoprolol, oxyhaemoglobin in the rectus femoris muscle became reduced (compared to rest; ?4.8 ± 1.8 vs. 1.2 ± 1.7 μmol L^?1, P < 0.05). Neither during rhythmic handgrip nor during cycling was the arterial carbon dioxide tension affected significantly by metoprolol. The results suggest that as for the muscle blood flow, the cerebral circulation is also affected by a reduced cardiac output during exercise with a large muscle mass.     

Transfusion in critically ill children: an ongoing dilemma

Transfusion of blood products is a cornerstone in managing many critically ill children. Major improvements in blood product safety have not diminished the need for caution in transfusion practice. In this review, we aim to discuss the interplay between benefits and potential adverse effects of transfusion in critically ill children by including 65 papers, which were evaluated based on previously agreed selection criteria. Current practice on transfusing critically ill children is mainly founded on the basis of adult studies, common practices with cut‐off values, and expert opinions, rather than evidence‐based medicine. Paediatric patients have explicit physiological challenges and requirements to be addressed. Critically ill children often suffer from anaemia, have substantial iatrogenic blood loss with subsequent transfusions, and are at a higher risk of complications, often due to human errors. Transfusion in children is associated with increased morbidity. A restrictive transfusion strategy is not associated with increased morbidity. Thus, transfusion in paediatrics should be considered a high‐risk treatment and requires individual clinical assessment. Current level of evidence support the notion that in most stable cases, despite high severity of illness (cyanotic children and neonates excluded), a restrictive haemoglobin threshold of 70 g/l (4.3 mmol/l) is no more harmful than to transfuse at a liberal trigger, e.g. haemoglobin 95 g/l (5.9 mmol/l). Thus, balanced against potential benefits and often its necessity, a restrictive approach may be appropriate due to the associated risks of transfusion.     

Birthweight-for-gestational age charts based on early ultrasound estimation of gestational age

Summary. Birthweight-for-gestational age charts were based on the analysis of 3888 consecutive births in which the gestational age was estimated by measuring the fetal biparietal diameter before the 20th week of gestation. The data showed, in contrast to previous studies, a linear relation between gestational age and birthweight without inflection after term. The regression parameters showed a strongly significant difference between girls and boys. Thus, boys were 1·5% heavier than girls at 190 days gestation and 3·6% heavier at 300 days gestation. The linearity in the birthweight-for-gestational age charts could be due to the more reliable gestational age based on early ultrasound.     

The Introduction of Ether Anaesthesia in the Nordic Countries

The way in which the news about ether anaesthesia went from U.S.A. to Europe is briefly described. The first information about ether anaesthesia came to the Scandinavian countries in 1847 through newspapers, which had their information from newspapers in England, France and Germany. The professional news came to the respective countries from doctors who were studying medical progress in Paris or from French medical journals. The first Scandinavian Society to be informed was the Swedish, and the first ether anaesthesia was given in Stockholm about 6 February. Denmark was next, and the first anaesthesia was given about 20 February in Copenhagen. In Norway, ether was used on 4 March in Christiania (Oslo), and in Finland on 8 March in Helsingfors (Helsinki). Anaesthesia in Iceland cannot be traced any earlier than 1856. A table shows when the first anaesthetics were given in different places in Europe and the world.     

Sympathetic influence on cardiovascular responses to sustained head-up tilt in humans

Sympathetic β-adrenergic influences on cardiovascular responses to 50d? head-up tilt were evaluated with metoprolol (β₁-blockade; 0.29 mg kg^-1) and propranolol (β₁ and β-₂-blockade; 0.28 mg kg^-1) in eight males. A normotensive-tachycardic phase was followed by a hypotensive-bradycardic episode associated with presyncopal symptoms after 23pL3 min (control, mean pLSE). Head-up tilt made thoracic electrical impedance (3.0pL10Ω), mean arterial pressure (MAP, 86pL4-93pL4 mmHg), heart rate (HR, 63pL3-99pL10 beats min^-1) and total peripheral resistance (TPR, 15pL1-28pL4 mmHg min L^-1) increase, while central venous oxygen saturation (74pL2-58pL4%), cardiac output (5.7pL0.1–3.1pL0.3 L min^-1), stroke volume (95pL6-41pL5 mL) and pulse pressure (55pL4-49pL4 mmHg) decreased (P < 0.05). Central venous pressure decreased during head-up tilt (7pL2-0pL1 mmHg), but it remained stable during the sustained tilt. At the appearance of preswyncopal symptoms MAP (49pL3 mmHg), HR (66pL4 beats min^-1) and TPR (15pL3 mmHg min L^-1) decreased (P < 0.05). Neither metoprolol or propranolo changed tilt tolerance or cardiovascular variables, except for HR that remained at 57pL2 (metoprolol) and 55pL3 beats min^-1 (propranolol), and MAP that remained at 87pL5 mmHg during the first phase with metoprolol. In conclusion, sympathetic activation was crucial for the heart rate elevation during normotensive head-up tilt, but not for tilt tolerance or for the associated hypotension and bradycardia.