Improving blood gas control in mechanically ventilated, premature infants through monitoring and evaluation of clinical practice

Mechanical ventilation causing hypocapnia or hyperoxia carries a risk for the pre-term infant. The aim was to improve blood gas control in our unit. A guideline was written, and all personnel were motivated concerning blood gas control. Case records of all mechanically ventilated premature infants were examined during two 3-month periods, before and after intervention. The hours spent with hypocapnia (pCO2 < 4 kPa) or hyperoxia (PO2 > 12 kPa) were recorded. Case records of 31 infants were examined for a total of 1358 h of mechanical ventilation, 641 h before and 717 h after the intervention. The percentage time of hypocapnia before intervention (7.0%) was reduced significantly (P = 0.044) to less than half (2.9%) after intervention. Hyperoxia was reduced from 14.5% to 8.7% (P = 0.072). Blood gas control of mechanically ventilated premature infants could be improved with little effort, but hyperoxia is too frequent.     

The effect of basal vasodilation on hypercapnic and hypocapnic reactivity measured using magnetic resonance imaging

Cerebrovascular reactivity to vasodilatory hypercapnic and vasoconstrictive hypocapnic challenges is known to be altered in several hemodynamic disorders, which is often attributable to changes in smooth muscle-mediated vascular compliance. Recently, attenuated reactivity to hypercapnia but enhanced reactivity to hypocapnia was observed in patients with chronic stroke. We hypothesize that the latter observation could be explained by a change in the basal vascular tone. In particular, reduced cerebral perfusion pressure, as is prevalent in these patients, may cause vasodilation through autoregulatory mechanisms, and this compensatory baseline condition may alter reactivity to vasoconstrictive hypocapnic challenges. To test this hypothesis, a predilated vascular condition was created in young, healthy subjects (n=11; age=23 to 36 years) using inhalation of 4% CO₂. Using blood oxygenation level-dependent functional magnetic resonance imaging at 3 T, breath holding and cued deep breathing respiratory challenges were administered to assess hypercapnia and hypocapnia reactivity, respectively. During the predilated condition, vasoconstrictive reactivity to hypocapnia was significantly (21.1%, P=0.016) enhanced throughout the gray matter, whereas there was no significant change (6.4%, P=0.459) in hypercapnic vasodilatory reactivity. This suggests that baseline vasodilation may explain the enhanced hypocapnia reactivity observed in some stroke patients, and that hypocapnia challenges may help identify the level of vascular compliance in patients with reduced cerebral perfusion pressure.     

Temporal Lobe CO2 Vasoreactivity in Patients with Complex Partial Seizures

Abstract: The topography of CO, vasoreactivity during hyperventilation in 8 patients with complex partial seizure (CPS) was visualized using the regional cerebral blood flow (rCBF) as measured by H₂¹⁵O-PET (positron emission tomography) and compared with that of 10 normal volunteers. In the normal volunteers, the vascular response to CO₂ (VrCO₂=ΔCBF%/APaCO₂) in the temporal lobe was 2.46±10.56 (%/mmHg). In the patients with CPS, VrCO₂ in the temporal lobe of the affected side was 2.08±0.40 (%/mmHg), while VrCO₂ on the contralateral side was 2.30 ± 0.46 (%/mmHg). There was a significant difference in VrCO₂ between the affected side of the temporal lobes and the temporal lobes of the normal volunteers. Furthermore, there was a tendency for VrCO₂ to be lower in the affected than in the contralateral side of the temporal lobe in patients with CPS. As CO₂ is the main regulator of CBF, this impaired vasoreactivity may reflect the brain dysfunction in the seizure focus and adjacent areas.     

THE EFFECT OF MODERATE HYPOCAPNIA ON THE CEREBRAL ARTERIO-VENOUS DIFFERENCE OF ACETOACETATE, d-β-HYDROXYBUTYRATE AND OXYGEN IN CHILDREN

Cerebral arterio-venous differences of aceto-acetate, D-β-hydroxybutyrate, glucose, glycerol, FFA, lactate, pyruvate and oxygen were determined during normo- and hypocapnia in children anaesthetized in connection with surgical operations or X-ray procedures. Cerebral flow equivalent values were used to calculate the relative changes in uptake or production of substrates during hypocapnia. The uptake of ketone bodies was proportional to the cerebral blood flow and to the arterial concentration. In comparison with reported values in adults the estimated uptake of ketone bodies at a given arterial concentration was about four times higher in children. During hypocapnia, but not during normocapnia children had a significant lactate production. The vasodilating effect of carbon dioxide on the cerebral blood vessels seems to be the same in children and adults.     

Effect of graded hypo- and hypercapnia on fMRI contrast in visual cortex: quantification of T(*)(2) changes by multiecho EPI.

The sensitivity of functional magnetic resonance imaging (fMRI) in visual cortex to graded hypo- and hypercapnia was quantified in 10 normal subjects using single-shot multiecho echo-planar imaging (Turbo-PEPSI) with eight equidistant echo times (TEs) between 12 and 140 ms. Visual stimulation was combined with controlled hyperventilation and carbon dioxide inhalation to perform fMRI at six levels of end-expiratory pCO(2) (PETCO(2)) between 20 and 70 mm Hg. T(*)(2) in visual cortex during baseline conditions (light off) increased nonlinearly from 20 to 70 mm Hg, from 61.1 +/- 4.2 ms to 72.0 +/- 4.6 ms. Changes in T(*)(2) due to visual stimulation increased 2.1-fold, from 1.2 +/- 0.6 ms at 20 mm Hg to 2.5 +/- 0.7 ms at 50 mm Hg. An almost complete loss of functional contrast was measured at 70 mm Hg. The model of MR signal dephasing by Yablonskiy and Haacke (Mag Reson Med 1994;32:749-763) was used to predict changes in cerebral blood flow (CBF), which were found to be consistent with results from previous positron emission tomography (PET) studies. This study further emphasizes that global CBF changes (due to PETCO(2) changes even in the physiological range) strongly influence fMRI contrast and need to be controlled for.     

Cerebral vasoreactivity in hypocapnia and hypercapnia in patients with diabetes mellitus type 2 with or without arterial hypertension

Background and purposeDiabetes mellitus (DM) is an independent risk factor for cardiovascular diseases. The origin of diabetic microangiopathy is multifactorial; it affects all layers of the artery wall, causing endothelial and vasoreactivity impairment. The incidence of cerebral vasoreactivity failure in diabetic patients without stroke history is not precisely determined yet. The aim of the study was to assess the cerebrovascular reactivity in hypocapnia and hypercapnia in patients with type 2 DM with or without arterial hypertension without artery stenosis and stroke history, with the use of transcranial Doppler examination.Material and methodsThe mean blood flow velocity, pulsatility index and parameters of cerebrovascular reactivity were measured in 53 patients with type 2 DM (aged 42–72 years, mean 59.5 ± 7.9) and in 27 healthy volunteers (aged 36–74 years, mean 57.0 ± 10.4). Diabetics were further divided into two subgroups according to the presence or absence of arterial hypertension.ResultsThe index of cerebrovascular reactivity in hypocapnia and hypercapnia was significantly worse and time needed to normalization of blood flow velocity was significantly longer in patients with DM in comparison with healthy volunteers.ConclusionsMost DM type 2 patients without stroke history had decreased values of cerebral vasoreactivity parameters, which suggests the presence of microangiopathy.     

血塞通注射液降低COPD患者肺动脉高压的作用及其机制

目的:观察血塞通注射液降低COPD患者肺动脉高压的临床作用并探讨其可能机制。方法:将22例确诊慢性阻塞性肺疾病患者随机分为常规治疗组和血塞通治疗组,随机抽取11例无肺疾患正常人作为对照组。常规治疗组予支气管扩张剂、抗生素及吸入糖皮质激素,血塞通治疗组在常规治疗基础上加用血塞通针,正常对照组不予任何治疗措施,2周后比较3组肺功能、肺动脉压及血气分析,ELISA法检测血浆磷酸化Erk1/2、磷酸化P38MAPK蛋白表达情况,评价血塞通注射液对慢性阻塞性肺疾病肺动脉高压的影响及与MAPKs信号通路的关系。结果:(1)常规组和血塞通组治疗后肺动脉压、肺功能及血气分析各项指标均较治疗前明显改善,且血塞通组优于常规组(均P0.05);(2)ELISA结果:血塞通组综合治疗后血浆p-ERK、p-P38表达降低(均P0.01),常规组无明显差异(P0.05),两组比较有统计学差异(均P0.05)。结论:血塞通注射液可能通过抑制P38MAPK、ERK1/2通路,有效地降低COPD患者肺动脉压,改善肺功能。     

Dyspnoea and hyperventilation induced by synthetic progesterone chlorpromadinone acetate for the treatment of prostatic hypertrophy

We describe a 74-year-old patient with dyspnoea and tachypnoea induced by chlorpromadinone acetate, a synthetic progesterone used to treat prostatic hyperplasia. The dyspnoea, tachypnoea and hypocapnia improved after discontinuing the chlorpromadinone acetate. It is important to recognize that synthetic progesterones can cause dyspnoea and hyperventilation.