Räsänen, Jukka

Pre-hospital use of whole blood is becoming increasingly prevalent in EMS and military medicine. Technologies to store, transport, warm up, and transfuse the blood are now available, and the outcome of whole blood transfusion seems to be superior to infusion of crystalloid solutions or plasma and at least equivalent to packed cells with plasma. The auto-transfusion tourniquet (A-TT®, Oneg HaKarmel Ltd., Tirat Carmel, Israel) is a non-invasive device that shifts the patient’s own blood from the legs to the core and blocks its reentry. The A-TT consists of an elastic ring made of a stainless-steel coil, wrapped by an elastic sleeve and pulling straps. When rolled up the leg(s), it squeezes the soft-tissues’ blood into the central circulation, and the ring stops the return of blood to the leg. The application time of the A-TT is less than 20 s per leg, and the A-TT transfers more than 500 mL of blood from each leg to the core. The auto-transfused blood is of the patient’s own type, has full oxygen carrying capacity, is normothermic, and is not anticoagulated. The device can be applied by a trained first responder, even during transport, and its use can be titrated to avoid overshooting the patient’s blood pressure. The device can be kept on the leg for up to 2 h, and as such, can serve as a bridge to blood or a bridge to definitive care. This paper is a hypothesis-generating review that defines the potential role of the A-TT in settings where blood is not available and is a call for others to help generate more data.

Setting: The coronavirus disease 2019 pandemic has raised fear throughout the nation. Current news and social media predictions of ventilator, medication, and personnel shortages are rampant. Patients: Patients with coronavirus disease 2019 are presenting with early respiratory distress and hypoxemia, but not hypercapnia. Interventions: Patients who maintain adequate alveolar ventilation, normocapnia, and adequate oxygenation may avoid the need for tracheal intubation. Facemask continuous positive airway pressure has been used to treat patients with respiratory distress for decades, including those with severe acute respiratory syndrome. Of importance, protocols were successful in protecting caregivers from contracting the virus, obviating the need for tracheal intubation just to limit the spread of potentially infectious particles. Conclusions: During a pandemic, with limited resources, we should provide the safest and most effective care, while protecting caregivers. Continuous positive airway pressure titrated to an effective level and applied early with a facemask may spare ventilator usage. Allowing spontaneous ventilation will decrease the need for sedative and paralytic drugs and may decrease the need for highly skilled nurses and respiratory therapists. These goals can be accomplished with devices that are readily available and easier to obtain than mechanical ventilators, which then can be reserved for the sickest patients.

To evaluate the utility of monitoring the sound-filtering characteristics of the respiratory system in the assessment of acute lung injury (ALI), we injected a multifrequency broadband sound signal into the airway of five anesthetized, intubated pigs, while recording transmitted sound over the trachea and on the chest wall. Oleic acid injections effected a severe lung injury predominantly in the dependent lung regions, increasing venous admixture from 6 ± 1 to 54 ± 8% ( P < 0.05) and reducing dynamic respiratory system compliance from 19 ± 0 to 12 ± 2 ml/cmH2O ( P < 0.05). A two- to fivefold increase in sound transfer function amplitude was seen in the dependent ( P < 0.05) and lateral ( P < 0.05) lung regions; no change occurred in the nondependent areas. High within-subject correlations were found between the changes in dependent lung sound transmission and venous admixture ( r = 0.82 ± 0.07; range 0.74–0.90) and dynamic compliance ( r = −0.87 ± 0.05; −0.80 to −0.93). Our results indicate that the acoustic changes associated with oleic acid-induced lung injury allow monitoring of its severity and distribution.

Objective To compare measured and predicted oxygen consumption (V˙o2) in children with congenital heart disease. Design Retrospective study. Setting The cardiac catheterisation laboratory in a university hospital. Patients 125 children undergoing preoperative cardiac catheterisation. Interventions V˙o2 was measured using indirect calorimetry; the predicted values were calculated from regression equations published by Lindahl, Wesselet al, and Lundell et al. Stepwise linear regression and analysis of variance were used to evaluate the influence of age, sex, weight, height, cardiac malformation, and heart failure on the bias and precision of predicted V˙o2. An artificial neural network was trained and used to produce an estimate of V˙o2 employing the same variables. The various estimates for V˙o2 were evaluated by calculating their bias and precision values. Results Lindahl’s equation produced the highest precision (±42%) of the regression based estimates. The corresponding average bias of the predicted V˙o2 was 3% (range −66% to 43%). When V˙o2 was predicted according to regression equations by Wessel and Lundell, the bias and precision were 0% and ±44%, and −16% and ±51%, respectively. The neural network predicted V˙o2 from variables included in the regression equations with a bias of 6% and precision ±29%; addition of further variables failed to improve this estimate. Conclusions Both regression based and artificial intelligence based techniques were inaccurate for predicting preoperative V˙o2 in patients with congenital heart disease. Measurement of V˙o2 is necessary in the preoperative evaluation of these patients.

Background Rapid recovery and weaning from ventilatory support and cardiovascular stability are suggested advantages of isoflurane inhalation, in concentrations ranging from 0.1 to 0.6 vol%, for long-term sedation in mechanical ventilated patients. This study was designed to determine whether isoflurane in low concentrations impairs pulmonary gas exchange by increasing ventilation and perfusion (V(A)/Q) mismatch during lung injury. Methods Fourteen anesthetized dogs received in random order 0, 0.25, or 0.5 vol% end-tidal isoflurane before and after induction of lung injury with oleic acid. Gas exchange was assessed by blood gas analysis and by estimating the V(A)/Q distributions using the multiple inert gas elimination technique. Results Administration of oleic acid produced a lung injury with severe V(A)/Q mismatch and 38 +/- 4% intrapulmonary shunting of blood. During lung injury, isoflurane accounted for a dose-related increase in blood flow to shunt units from 38 +/- 4 to 42 +/- 3 (0.25 vol%) and 48 +/- 4% (0.5 vol%) (P < 0.05), dispersion pulmonary blood flow distribution from 0.94 +/- 0.07 to 1.01 +/- 0.09 (0.25 vol%) and 1.11 +/- 0.11% (0.5 vol%) (P < 0.05), and a decrease in perfusion of normal V(A)/Q units from 58 +/- 5 to 55 +/- 4 (0.25 vol%) and 50 +/- 4% (0.5 vol%) (P < 0.05) (mean +/- SE). Isoflurane decreased arterial oxygen partial pressure from 72 +/- 4 to 62 +/- 4 mmHg (0.25 vol%) and 56 +/- 4 mmHg (0.5 vol%) (P < 0.05) and oxygen delivery from 573 +/- 21 to 529 +/- 19 ml. kg. min (0.25 vol%) and 505 +/- 22 ml. kg. min (0.5 vol%) (P < 0.05). Gas exchange, perfusion of shunt and normal V(A)/Q units, and pulmonary blood flow distribution was similar in absence of lung injury with and without isoflurane. Isoflurane 0.5 vol% lowered cardiac output during all conditions (P < 0.05). CONCLUSIONS Inhalation of low concentrations of isoflurane contributed to increased V(A)/Q mismatch and decreased systemic blood flow and oxygen delivery in mechanically ventilated animals with injured lungs.