Karl-Friedrich Klotz

Automated Evaluation of Functional Residual Capacity by Oxygen Washout

Objective.Measurement of functional residual capacity (FRC) is of considerable interest for monitoring ventilated patients in ICUs. However, the lack of instruments that can be used in the clinical setting has so far impeded the routine application of this measurement. It was the aim of our study to evaluate the accuracy and the reproducibility of a simplified oxygen washout technique (FRC[O2]). Materials and methods.For the evaluation of FRC[O2], gas flow, CO2 and O2 concentrations were determined by the flow probe of an ICU ventilator, a mainstream capnometer and O2 analyser. In 30 volunteers FRC[O2] as measured during spontaneous breathing was compared to: 1. Helium dilution technique (FRC[He], n= 21), 2. Body plethysmography (FRC[bp], n= 9). In n= 7 male patients FRC[O2] was repeatedly evaluated during mechanical ventilation and compared to the preoperative FRC[bp]. Results.FRC[O2] corresponded well with FRC[He] (range: 1.9 to 6.0 l, bias of FRC[O2]: 0.53 l (95% CI 0.24 l to 0.82 l)) and FRC[bp] (range: 2.1 to 4.3 l, bias of FRC[O2] 0.03 l (95% CI –0.30 l to 0.37 l)). The mean of the repeated FRC[O2]-measurements (basic range: 1.3 to 3.6 l) during mechanical ventilation with unchanged ventilator settings stayed unchanged. The within subject-between error ranged from 0.1 to 0.4 l (mean = 0.23 l). Mean FRC[O2] during mechanical ventilation decreased to 66.6 percent of the preoperative mean FRC[bp]. Conclusions.The automated oxygen washout technique is a simple method to measure FRC in the ICU patient.

A rise of MMP-2 and MMP-9 in bronchoalveolar lavage fluid is associated with acute lung injury after cardiopulmonary bypass in a swine model

Postoperative acute lung injury (ALI) contributes to the morbidity and mortality following cardiopulmonary bypass (CPB). To determine whether the presence of matrix metalloproteinases (MMPs) is associated with ALI after CPB, MMP-2 and MMP-9 activities in bronchoalveolar lavage fluid (BALF) were compared with parameters indicating impaired gas exchange. In a prospective study, 17 minipigs were subjected to CPB for 60 min. Before and at five and 180 min after CPB, MMP-2 and MMP-9 were assayed in BALF and the arterial-alveolar gradient of oxygen tension (AaDO2), the pulmonary capillary wedge pressure (PCWP) and the water content of lung tissue samples (Wt) were evaluated and compared with baseline values. MMP-2 and MMP-9 increased significantly 5 minutes (2.1- and 6.2-fold, respectively) and 180 minutes (3.4- and 14.3-fold, respectively) post-CPB. AaDO2 and Wt, but not PCWP, increased significantly 180 minutes after CPB and only AaDO2, but not PCWP or Wt, was significantly correlated with MMP-2 (r /0.66, p /0.006) and MMP-9 (r /0.62, p /0.01). In conclusion, high levels of MMP-2 and MMP-9 in the pulmonary compartment are associated with ALI after CPB.

Organ-specific extravasation of albumin-bound Evans blue during nonresuscitated hemorrhagic shock in rats.

Shock-induced enhanced capillary permeability is associated with alterations in the interstitial matrix composition and contributes to organ damage. This study was designed to evaluate albumin extravasation in various organ tissues during severe, hemorrhagic shock without fluid resuscitation and reperfusion. Target value of hemorrhagic shock was a reduction of cardiac output (CO) by 50% induced by removal of blood. Twelve anesthetized Sprague-Dawley rats (260–325 g) kept under continuous hemodynamic monitoring were randomly assigned to a group of hemorrhagic shock (n = 6) and a control group of normovolemic animals (n = 6). After 30 min of shock 50 mg/kg b.w. Evans blue (EB) was injected intravenously followed by an incubation period of 20 min. Exsanguination and wash out of the intravascular space was performed by a pressure-controlled perfusion with heparinized saline before harvesting organs to quantify albumin-bound EB extravasation. We found that withdrawal of 4.7 ± 0.4 mL (mean, ±SEM) blood, which accounts for 21.1% of the calculated total blood volume, resulted in a reduction of CO from 36.1 ± 3.1 to 19.4 ± 2.7 mL/min. Simultaneously, MAP decreased from 98 ± 6 to 40 ± 1 mmHg. In hemorrhaged rats, the interstitial concentration of EB in lung and kidney was significantly higher than observed in intact animals, whereas heart, spleen, liver, ileum, skeletal muscle, and skin showed no significant microvascular damage. We conclude that despite the absence of fluid resuscitation and reperfusion, microvascular damage in lung and kidney is evident within the first thirty minutes of hemorrhagic shock.

Intercompartmental fluid volume shifts during cardiopulmonary bypass measured by A-mode ultrasonography.

To investigate the time course of fluid extravasation during cardiopulmonary bypass (CPB), we measured the peripheral tissue thickness (TT) by A-mode ultra-sound in 34 patients undergoing elective cardiac surgery. TT of the forehead was determined by a handheld A-mode ultrasound device and 10 MHz Transducer at nine defined intervals, from the night before surgery until the first postoperative day. Mean calculated loss of 1700±40 mL (SEM) water during the fasting period resulted in a significant reduction of TT by 0.28±0.03 mm. From induction to start of CPB, rehydration with 1000 mL of fluid was performed and TT increased to baseline. After 60 min of extracorporal circulation, forehead TT increased significantly by 0.75±0.08 mm and remained unchanged until the end of surgery when the measured fluid gain was 1580±138 mL. At discharge from ICU, negative fluid regimen resulted in a balance of -127±146 mL whereas TT declined significantly to + 0.16±0.09 mm compared to baseline. Dehydration due to fasting and the marked interstitial fluid extravasation during CPB could be detected by the changes of the peripheral TT. We conclude that parts of the fluid load during CPB are shifted from the intravascular compartment to the interstitial space in a time-dependent manner.

Na+/H+exchange inhibitor cariporide: effects on respiratory dysfunction after cardiopulmonary bypass:

The purpose of the present study was to evaluate the potential of the Na+/H+ exchange inhibitor cariporide to protect the lung from injury after cardiopulmonary bypass (CPB). In a randomized placebo-controlled study, 16 pigs were subjected to CPB for 75 min. Administration of vehicle or cariporide (bolus 180 mg, 40 mg/hour) began 30 min pre-CPB and was continued throughout the protocol. The alveolo-arterial O2-gradient (AaDO2), the pulmonary shunt (Qs/Qt), the compliance (Cpl), haemo-dynamic variables and glycerol and water content in lung tissue were measured 10 min before and up to 180 min post-CPB. All animals in the control versus 75% in the cariporide group survived the experiment. At 5 and 60 min post-CPB, the mean AaDO2 and at 5, 60 and 180 min post-CPB, the mean pulmonary vascular resistance index were higher in the cariporide group (p < 0.05), respectively. More lung water accumulation was found in the cariporide group (p < 0.05). Mean Cpl decreased; the Qs/Qt and glycerol in lung tissue increased without significant intergroup difference. In this model, the inhibitor of the Na+/H+ antiporter showed no protective effect on lung injury after CPB and might even have harmful effects on pulmonary vascular tone and function.

Perioperative Tissue Thickness Measurement by a New Miniature Ultrasound Device

Introduction. A recently developed mini ultrasound device for measurement of peripheral tissue thickness is now available for use in clinical practice. Whether this device allows a better guidance of perioperative fluid therapy has to be investigated. Therefore, it is necessary to get basic data on the parameter tissue thickness in otherwise healthy patients during surgery. The aim of the present study was to evaluate differences in tissue thickness change between patients in supine and head down position with a novel handheld ultrasound device during the perioperative course of healthy surgical patients under a standardized fluid regimen. Methods. After obtaining ethics committee approval and informed consent we studied 19 ASA 1–2 female patients undergoing gynecological procedures in supine (SUP, n = 11) or in 30° head down position (HD, n = 8) in general anesthesia. Preoperative NPO status was comparable in both groups. Lactated Ringers solution (LR) was continuously infused at a rate of 8 ml/kg b.w./h over 90 min and tissue thickness (TT) was determined by ultrasound before induction (t0) and in 30 min intervals (t30, t60, t90) at the forehead. Simultaneously plasma viscosity (PV) was evaluated. Results. Group SUP presented at t0 a forehead TT of 5.3 mm (SD ±0.5), at t30 TT was unchanged. At t60 mean TT increased significantly to 5.6 mm, (±0.6). At t90 mean TT remained stable at 5.7 mm (±0.5). Group HD presented at t0 a mean TT of 4.6 mm (±0.7), at t30 mean TT was 4.9 mm (±0.7) and at t60 mean TT of the forehead skin was measured as 5.3 mm (±0.6). Significance to t0 was reached at t90 with a mean TT of 5.4 mm (±0.7). Group HD showed a steeper increase and a parallel stabilization phase at the end. Differences between t0 and t90 have been significant. Mean PV in the SUP group at t0 (1.361 mPa*s, SD: ±0.045) decreased under the infusion therapy to 1.276 mPa*s (±0.04) at t90. Mean PV in the HD group was determined 1.351 mPa*s (±0.06) at t0 and declined to 1.274 mPa*s (±0.03) at t90. Conclusions.The findings suggest that fluid replacement after an NPO period and the expected changes of forehead TT due to positioning of the patient are detectable by this new ultrasound device.

A miniature self-inflating bag-mask ventilator for rats

Respiratory depression and apnoea during anaesthesia may lead to hypoxia and myocardial ischaemia. A self-inflating miniature bag-mask device was assembled combining characteristics from the Ambu-bag and the Kuhn-system. This bag-mask device permitted ventilation during anaesthesia-induced apnoea in rats until a safe airway by tracheotomy was achieved.

Pulmonary artery perfusion during cardiopulmonary bypass improves postoperative gas exchange in a swine model: A-182

L-NMMA (100 mol/l) to block NO-synthesis reduced coronary flow by 15%. In the presence of L-NMMA hypercapnic perfusion was associated with a reduced flow increase (22%). Additional infusion of TEA (1 mmol/l) to block Ca2 -dependent K -channels was associated with a slight increase of coronary flow and LVD. However, the hypercapnia-related flow increase was not further reduced. In contrast, acetylcholine (0.5 M) induced flow increase was decreased in the presence of L-NMMA and in the additional presence of TEA. Conclusions: NO is important for the mediation of hypercapnic coronary dilation in mouse heart. While K Ca-channels are involved in the mediation of cholinergic coronary dilation, they are unimportant for hypercapnic vasodilation.

Intrathecal spread of mepivacaine, ropivacaine and levobupivacaine after epidural application in sheep: A-487

femoral nerve territory 4, 24, and 48 h after the initial injection. VAS at rest (R) and on movement (M) (0: no pain–100: severe pain) at 4, 24 and 48 h; satisfaction score (0: unsatisfied–100: completely satisfied) at 24 and 48 h; supplemental analgesia (Propacetamol (Propac) and/or Morphine (Morph)); first request of LA, Propac, and Morph; total LA consumption; PCA boluses requested; and side effects were recorded. Statistical analysis was done with ANOVA and Fischer test and 2 when appropriate. A p value 0.05 was considered significant. Results are expressed as mean SD. Results and Discussions: Population data, pain scores, sensory and motor blockade, total LA consumption, PCA boluses requested, satisfaction score, and side effects were comparable in the 3 groups. When compared with groups B and L, less Propac (B: 11 5, R: 7 5, and L: 9 4 g/48 h) and Morph (B: 8 11, R: 2 4, and L: 9 12 mg/48 h) was required in group R. In this group, first request of LA (B: 229 62, R: 275 52, and L: 230 72 min.) was later. Conclusion(s): The 3 studied LA are efficient to maintain CFB after THR. As it is associated with less supplemental analgesia, R would be the preferred solution. References: 1 Singelyn FJ, Gouverneur JM. J Clin Anesth 1999;11:550–4. 2 Singelyn FJ, Vanderelst P, Gouverneur JM. Anesth Analg 2001;92:455–9.

Comparison of two oxygen delivery systems for safe sedation and spinal anesthesia in sheep

Proper oxygenation is critical to prevent hypoxia and myocardial ischemia in animals during pharmacological sedation. The authors compared the efficacy of two oxygen delivery masks during sedation and spinal anesthesia for knee surgery in sheep.