Effect of dexmedetomidine on cardiorespiratory regulation in spontaneously breathing adult rats

Purpose We examined the cardiorespiratory effect of dexmedetomidine, an α2- adrenoceptor/imidazoline 1 (I1) receptor agonist, in spontaneously breathing adult rats. Methods Male rats (226−301 g, n = 49) under isoflurane anesthesia had their tail vein cannulated for drug administration and their tail artery cannulated for analysis of mean arterial pressure (MAP), pulse rate (PR), and arterial blood gases (PaO2, PaCO2, pH). After recovery, one set of rats received normal saline for control recording and was then divided into three experimental groups, two receiving dexmedetomidine (5 or 50 μg·kg−1) and one receiving normal saline (n = 7 per group). Another set of rats was divided into four groups receiving dexmedetomidine (50 μg·kg−1) followed 5 min later by 0.5 or 1 mg∙kg−1 atipamezole (selective α2-adrenoceptor antagonist) or efaroxan (α2-adrenoceptor/I1 receptor antagonist) (n = 6 or 8 per group). Recordings were performed 15 min after normal saline or dexmedetomidine administration. Results Compared with normal saline, dexmedetomidine (5 and 50 μg·kg−1) decreased respiratory frequency (fR, p = 0.04 and < 0.01, respectively), PR (both p < 0.01), and PaO2 (p = 0.04 and < 0.01), and increased tidal volume (both p = 0.049). Dexmedetomidine at 5 μg·kg−1 did not significantly change minute ventilation (V′E) (p = 0.87) or MAP (p = 0.24), whereas dexmedetomidine at 50 μg·kg−1 significantly decreased V′E (p = 0.03) and increased MAP (p < 0.01). Only dexmedetomidine at 50 μg·kg−1 increased PaCO2 (p < 0.01). Dexmedetomidine (5 and 50 μg·kg−1) significantly increased blood glucose (p < 0.01), and dexmedetomidine at 50 μg·kg−1 increased hemoglobin (p = 0.04). Supplemental atipamezole or efaroxan administration similarly prevented the 50 μg·kg−1 dexmedetomidine-related cardiorespiratory changes. Principal conclusion These results suggest that dexmedetomidine-related hypoventilation and hypertension are observed simultaneously and occur predominantly through activation of α2-adrenoceptors, but not I1 receptors, in spontaneously breathing adult rats.

Gas conditioning during helmet noninvasive ventilation: effect on comfort, gas exchange, inspiratory effort, transpulmonary pressure and patient–ventilator interaction

Background There is growing interest towards the use of helmet noninvasive ventilation (NIV) for the management of acute hypoxemic respiratory failure. Gas conditioning through heat and moisture exchangers (HME) or heated humidifiers (HHs) is needed during facemask NIV to provide a minimum level of humidity in the inspired gas (15 mg H2O/L). The optimal gas conditioning strategy during helmet NIV remains to be established. Methods Twenty patients with acute hypoxemic respiratory failure (PaO2/FiO2 < 300 mmHg) underwent consecutive 1-h periods of helmet NIV (PEEP 12 cmH2O, pressure support 12 cmH2O) with four humidification settings, applied in a random order: double-tube circuit with HHs and temperature set at 34 °C (HH34) and 37 °C (HH37); Y-piece circuit with HME; double-tube circuit with no humidification (NoH). Temperature and humidity of inhaled gas were measured through a capacitive hygrometer. Arterial blood gases, discomfort and dyspnea through visual analog scales (VAS), esophageal pressure swings (ΔPES) and simplified pressure–time product (PTPES), dynamic transpulmonary driving pressure (ΔPL) and asynchrony index were measured in each step. Results Median [IqR] absolute humidity, temperature and VAS discomfort were significantly lower during NoH vs. HME, HH34 and HH37: absolute humidity (mgH2O/L) 16 [12–19] vs. 28 [23–31] vs. 28 [24–31] vs. 33 [29–38], p < 0.001; temperature (°C) 29 [28–30] vs. 30 [29–31] vs. 31 [29–32] vs 32. [31–33], p < 0.001; VAS discomfort 4 [2–6] vs. 6 [2–7] vs. 7 [4–8] vs. 8 [4–10], p = 0.03. VAS discomfort increased with higher absolute humidity (p < 0.01) and temperature (p = 0.007). Higher VAS discomfort was associated with increased VAS dyspnea (p = 0.001). Arterial blood gases, respiratory rate, ΔPES, PTPES and ΔPL were similar in all conditions. Overall asynchrony index was similar in all steps, but autotriggering rate was lower during NoH and HME (p = 0.03). Conclusions During 1-h sessions of helmet NIV in patients with hypoxemic respiratory failure, a double-tube circuit with no humidification allowed adequate conditioning of inspired gas, optimized comfort and improved patient–ventilator interaction. Use of HHs or HME in this setting resulted in increased discomfort due to excessive heat and humidity in the interface, which was associated with more intense dyspnea. Trail Registration Registered on clinicaltrials.gov (NCT02875379) on August 23rd, 2016.

Objective Evaluation of Efficacy of Decortication in Chronic Pleural Empyema in Adult Patients

Background: Chronic pleural empyema (CPE) is the last phase of the triphasic process of pleural empyema development. Lung decortication is the corner stone in management of chronic empyema. This study aimed to objectively evaluate the efficacy of conventional decortication operation in chronic pleural empyema in adult patients. Also to prove that decortication of variable sizes of chronic empyema thoracis lesions is followed by improvement considering respiratory impairment. Methods: This prospective clinical study was conducted on 103 patients undergoing elective lung decortication operation for management of chronic empyema. All patients were subjected to the history taking, general examination, chest examination, computed tomography (CT), pulmonary function test and arterial blood gases. Postoperative evaluation was done in outpatient clinic 6 months post operatively including: Full clinical examination, investigations (acute phase reactants, CT chest, PFT and arterial blood gases. Results: Total leucocytic count, ESR 1st hour, ESR 2nd hour and CRP were significantly decreased in post than pre. FEV1 and FVC were significantly increased in post than pre (P <0.001). FEV1 / FVC Ratio was significantly decreased in post than pre (P <0.001). Transverse and antero-posterior diameters of affected hemithorax were significantly increased in post than pre (P <0.001, 0.019 respectively). Transverse and antero-posterior diameters of normal hemithorax were insignificantly different between post and pre. PaO2 and SpO2 were significantly increased in post than pre (P <0.001). PaCO2 was significantly decreased in post than pre (P <0.001). Conclusions: The improvement in the lung function, arterial blood gases, transverse and antero-posterior diameter of affected and normal hemithorax was proposed to have resulted from the decortication in chronic empyema thoracis. Decortication of variable sizes of chronic pleural empyema lesions is followed by objective improvement considering respiratory impairment.

Estimating exercise PaCO2 in patients with heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) patients exhibit cardiopulmonary abnormalities that could affect the predictability of exercise PaCO2 from the Jones (PJCO2) equation (PJCO2=5.5+0.9xPETCO2-2.1xVT). Since the dead space to tidal volume (VD/VT) calculation also includes PaCO2 measurements, estimates of VD/VT from PJCO2 may also be affected. Because using noninvasive estimates of PaCO2 and VD/VT could save patient discomfort, time, and cost, we examined whether PETCO2 and PJCO2 can be used to estimate PaCO2 and VD/VT in 13 HFpEF patients. PETCO2 was measured from expired gases measured simultaneously with radial arterial blood gases at rest, constant-load (20W), and peak exercise. VD/VT[art] was calculated using the Enghoff modification of the Bohr equation, and estimates of VD/VT were calculated using PETCO2 (VD/VT[ET]) and PJCO2 (VD/VT[J]) in place of PaCO2. PETCO2 was similar to PaCO2 at rest (-1.46±2.63, P=0.112) and peak exercise (0.66±2.56, P=0.392), but overestimated PaCO2 at 20W (-2.09±2.55, P=0.020). PJCO2 was similar to PaCO2 at rest (-1.29±2.57, P=0.119) and 20W (-1.06±2.29, P=0.154); but, underestimated PaCO2 at peak exercise (1.90±2.13, P=0.009). VD/VT[ET] was similar to VD/VT[art] at rest (-0.01±0.03, P=0.127) and peak exercise (0.01±0.04, P=0.210), but overestimated VD/VT[art] at 20W (-0.02±0.03, P=0.025). Although VD/VT[J] was similar to VD/VT[art] at rest (-0.01±0.03, P=0.156) and 20W (-0.01±0.03, P=0.133), VD/VT[J] underestimated VD/VT[art] at peak exercise (0.03±0.04, P=0.013). Exercise PETCO2 and VD/VT[ET] provide better estimates of PaCO2 and VD/VT[art] than PJCO2 and VD/VT[J] does at peak exercise. Thus, estimates of PaCO2 and VD/VT should only be used if sampling arterial blood during CPET is not feasible.

The Role of Lactate Dehydrogenase (LDH) Compared to Arterial Blood Gases (ABG) in Diagnosing Pneumocystis Carinii Pneumonia (PCP) in HIV/AIDS Patients on Routine Antiretroviral Therapy

Background: The lungs are one of the primary target organs for HIV disease and a major source of morbidity and mortality, among others, caused by Pneumocystis carinii pneumonia (PCP) or recurrent bacterial pneumonia. In developing countries, the incidence of PCP infection has soared, with high mortality rates ranging from 20% to 80%. The increase in serum LDH plays an important role in determining the severity of the disease. This study aims to determine the role of LDH examination as a diagnostic tool for PCP and Arterial Blood Gases (ABG) in HIV and AIDS patients. Method: This research is an analytical study using an observational diagnostic test design, conducted from November 2020-January 2021 at the HIV Treatment Room at H. Adam Malik Hospital, Medan with 158 subjects. We calculate the value of sensitivity, specificity, positive predictive value, and negative predictive value. Results: 75.3% of the total sample was male, with the highest age group being 30-39 years old (46.2%) 126 samples (79.7%) had CD4 levels 200 cells/mm3, 98 samples (62%) had LDH levels > 500 U/L. In this study, 113 samples (71.5%) fell into the ABG criteria [PaO2] <70 mmHg). LDH has superior sensitivity and specificity value compared to ABG examination. In this case PaO2 or A-A DO2 in diagnosing PCP in HIV-AIDS patients. Conclusion: LDH examination combined with clinical and radiological examinations has good sensitivity and specificity in the diagnosis of PCP. Keywords: HIV, AIDS, Lactate dehydrogenase, PCP.