Protective ventilation with high versus low positive end-expiratory pressure during one-lung ventilation for thoracic surgery (PROTHOR): study protocol for a randomized controlled trial

BACKGROUND

Postoperative pulmonary complications (PPC) may result in longer duration of in-hospital stay and even mortality. Both thoracic surgery and intraoperative mechanical ventilation settings add considerably to the risk of PPC. It is unclear if one-lung ventilation (OLV) for thoracic surgery with a strategy of intraoperative high positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM) reduces PPC, compared to low PEEP without RM.

METHODS

PROTHOR is an international, multicenter, randomized, controlled, assessor-blinded, two-arm trial initiated by investigators of the PROtective VEntilation NETwork. In total, 2378 patients will be randomly assigned to one of two different intraoperative mechanical ventilation strategies. Investigators screen patients aged 18 years or older, scheduled for open thoracic or video-assisted thoracoscopic surgery under general anesthesia requiring OLV, with a maximal body mass index of 35 kg/m2, and a planned duration of surgery of more than 60 min. Further, the expected duration of OLV shall be longer than two-lung ventilation, and lung separation is planned with a double lumen tube. Patients will be randomly assigned to PEEP of 10 cmH2O with lung RM, or PEEP of 5 cmH2O without RM. During two-lung ventilation tidal volume is set at 7 mL/kg predicted body weight and, during OLV, it will be decreased to 5 mL/kg. The occurrence of PPC will be recorded as a collapsed composite of single adverse pulmonary events and represents the primary endpoint.

DISCUSSION

PROTHOR is the first randomized controlled trial in patients undergoing thoracic surgery with OLV that is adequately powered to compare the effects of intraoperative high PEEP with RM versus low PEEP without RM on PPC. The results of the PROTHOR trial will support anesthesiologists in their decision to set intraoperative PEEP during protective ventilation for OLV in thoracic surgery.

TRIAL REGISTRATION

The trial was registered in clinicaltrials.gov ( NCT02963025 ) on 15 November 2016.

The immune response to one-lung-ventilation is not affected by repeated alveolar recruitment manoeuvres in pigs

BACKGROUND

Acute lung injury after thoracic surgery relates to alveolar inflammation induced by one-lung ventilation (OLV) and surgical manipulation. However, alveolar recruitment manoeuvres (ARM), conventional ventilation, and airway manipulation may increase alveolar trauma. This study evaluates pulmonary immune effects of these co-factors in a porcine model.

METHODS

Twenty-two piglets (27.3 kg) were randomised to spontaneous breathing (N.=4), two-lung ventilation (TLV, N.=6), OLV with propofol (6 mg/kg/h, N.=6) or desflurane anesthesia (1MAC, N.=6). Mechanical ventilation settings were constant throughout the experiment: VT=10 mL/kg, FIO2=0.4, PEEP=5 cmH2O. OLV was performed by left-sided bronchial blockade. Thoracic surgery was simulated for 60 min. ARM (airway pressure of 40 mbar for 10 s) was applied before and after each airway manipulation. Cytokines and mRNA-expression were assessed by immunoassays and semi-quantitative RT-PCR in alveolar lavage fluids, serum and tissue samples prior to and after OLV (TLV in controls).

RESULTS

Repetitive ARM and TLV induced no significant proinflammatory effects. OLV enhanced cytokine release but less with desflurane inhalation than propofol infusion (median (IQR) [pg/mL], dependent lung): Interleukin-8: TLV 44 (17) to 68 (35), propofol 82 (17) to 494 (231), desflurane 89 (30) to 282 (44). Likewise, serum cytokines were different: tumour necrosis factor-a: TLV 37 (13) to 62 (7), propofol 55 (39) to 94 (60), desflurane 43 (33) to 41 (25). Expression of interleukin-8-mRNA increased after OLV, but mRNA expression was not modulated by anesthetics.

CONCLUSION

ARM, standard TLV and repetitive BAL do not additionally contribute to lung injury resulting from OLV for thoracic surgery in healthy porcine lungs. OLV induces expression of interleukin-8-mRNA in alveolar cells, which is not modulated by different anesthetic drugs.

Improved ventilation-perfusion matching by abdominal insufflation (pneumoperitoneum) with CO2 but not with air

BACKGROUND

Pneumoperitoneum (PP) by CO2-insufflation causes atelectasis however with maintained or even improved oxygenation. We studied the effect of abdominal insufflation by carbon dioxide (CO2) and air on gas exchange during PP.

METHODS

Twenty-seven anesthetized pigs were studied during PP with insufflations to 12 mmHg by either 1/CO2, 2/ air or 3/CO2 during intravenous nitroprusside infusion (SNP) (N.=9 in each group). In 3 pigs in each group, gamma camera technique (SPECT) was used to study ventilation and perfusion distributions, in another 6 pigs an inert-gas technique (MIGET) was used for assessing ventilation-perfusion matching (VA/Q). Measurements were made during anesthesia before and after 60 minutes of PP.

RESULTS

CO2-PP caused a shift of blood flow away from dependent, non-ventilated (atelectatic) to ventilated regions. Air-PP caused smaller, and SNP-PP even less shift of lung blood flow. Shunt decreased during CO2-PP (6 ± 1% compared to baseline 9 ± 2%, P<0.05), did not change during Air-PP (10 ± 2%) and increased during SNP-PP (16 ± 2%, P<0.05). PaO2 increased from baseline 35 ± 2 to 41 ± 3 kPa during CO2-PP and decreased to 32 ± 3 kPa during Air-PP and to 27 ± 3 kPa during SNP-PP (P<0.05 for all three comparisons). PaCO2 increased during CO2- and SNP-PP.

CONCLUSION

CO2-PP enhanced the shift of blood flow towards better ventilated areas of the lung compared to Air-PP and SNP blunted the effects seen with CO2-PP. SNP may thus have blunted and CO2 potentiated vasoconstriction, by hypoxic pulmonary vasoconstriction or another mechanism.

[45-year old patient with progressive shortness of breath and "crazy paving"]

A 45-year-old man referred with progressive shortness of breath. Chest X-ray revealed a diffuse parenchymal process in the lungs, which was characterized as a "crazy paving" pattern in the thoracic CT. Pulmonary function test showed severe impairment of diffusion capacity and apparent respiratory insufficiency. Bronchoalveolar lavage and histological examinations of transbronchial lung biopsies revealed alveolar proteinosis. Because of the presence of anti-granulocyte macrophage colony-stimulating factor (GM-CSF) autoantibodies, a primary form of this disorder was diagnosed. Therapeutic whole-lung lavage was performed twice and resulted in a continuing remission.

[Sexual hallucinations and dreams under anesthesia and sedation : medicolegal aspects]

Dreams and hallucinations under sedation or anesthesia have been well known phenomena since the introduction of anesthesia. Sexual hallucinations may lead to allegations of sexual molestation or assault by medical doctors or professional nursing staff. Hallucinations under the influence of sedative or hypnotic drugs may be very vivid and as misinterpreted as being real and it is therefore often difficult to disprove the resulting false allegations. In this report the terms drug-induced dreams and hallucinations are defined and the probable mechanism described. By a historical review and case reports the medicolegal consequences are demonstrated and procedures recommended to avoid allegations of sexual assault.

Improved ventilation-perfusion matching with increasing abdominal pressure during CO(2) -pneumoperitoneum in pigs

BACKGROUND

CO(2) -pneumoperitoneum (PP) is performed at varying abdominal pressures. We studied in an animal preparation the effect of increasing abdominal pressures on gas exchange during PP.

METHODS

Eighteen anaesthetized pigs were studied. Three abdominal pressures (8, 12 and 16 mmHg) were randomly selected in each animal. In six pigs, single-photon emission computed tomography (SPECT) was used for the analysis of V/Q distributions; in another six pigs, multiple inert gas elimination technique (MIGET) was used for assessing V/Q matching. In further six pigs, computed tomography (CT) was performed for the analysis of regional aeration. MIGET, CT and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia and after 60 min on each of the three abdominal pressures. SPECT was performed three times, corresponding to each PP level.

RESULTS

Atelectasis, as assessed by CT, increased during PP and in proportion to abdominal pressure [from 9 ± 2% (mean ± standard deviation) at 8 mmHg to 15 ± 2% at 16 mmHg, P<0.05]. SPECT during increasing abdominal CO(2) pressures showed a shift of blood flow towards better ventilated areas. V/Q analysis by MIGET showed no change in shunt during 8 mmHg PP (9 ± 1.9% compared with baseline 9 ± 1.2%) but a decrease during 12 mmHg PP (7 ± 0.9%, P<0.05) and 16 mmHg PP (5 ± 1%, P<0.01). PaO(2) increased from 39 ± 10 to 52 ± 9 kPa (baseline to 16 mmHg PP, P<0.01). Arterial carbon dioxide (PCO(2) ) increased during PP and increased further with increasing abdominal pressures.

CONCLUSION

With increasing abdominal pressure during PP perfusion was redistributed more than ventilation away from dorsal, collapsed lung regions. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction mediated by increasing PCO(2) .

[Postoperative wound infections. Pathophysiology, risk factors and preventive concepts]

Postoperative wound infections are the third most common type of nosocomial infection in German emergency hospitals after pneumonia and urinary infections. They are associated with increased morbidity and mortality, prolonged hospital stay and increased costs. The most important risk factors include the microbiological state of the skin surrounding the incision, delayed or premature prophylaxis with antibiotics, duration of surgery, emergency surgery, poorly controlled diabetes mellitus, malignant disease, smoking and advanced age. Anesthesiological measures to decrease the incidence of wound infections are maintaining normothermia, strict indications for allogenic blood transfusions and timely prophylaxis with antibiotics. Blood glucose concentrations should be kept in the range of 8.3-10 mmol/l (150-180 mg/dl) as lower values are associated with increased complications. Intraoperative and postoperative hyperoxia with 80% O(2) has not been shown to effectively decrease wound infections. The application of local anesthetics into the surgical wound in clinically relevant doses for postoperative analgesia does not impair wound healing.

Ventilation-perfusion distributions and gas exchange during carbon dioxide-pneumoperitoneum in a porcine model

BACKGROUND

Carbon dioxide (CO₂)-pneumoperitoneum (PP) of 12 mm Hg increases arterial oxygenation, but it also promotes collapse of dependent lung regions. This seeming paradox prompted the present animal study on the effects of PP on ventilation-perfusion distribution (V/Q) and gas exchange.

METHODS

Fourteen anaesthetized pigs were studied. In seven pigs, single photon emission computed tomography (SPECT) was used for spatial analysis of ventilation and perfusion distributions, and in another seven pigs, multiple inert gas elimination technique (MIGET) was used for detailed analysis of V/Q matching. SPECT/MIGET and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia before and 60 min after induction of PP.

RESULTS

SPECT during PP showed no or only poorly ventilated regions in the dependent lung compared with the ventilation distribution during anaesthesia before PP. PP was accompanied by redistribution of blood flow away from the non- or poorly ventilated regions. V/Q analysis by MIGET showed decreased shunt from 9 (sd 2) to 7 (2)% after induction of PP (P<0.05). No regions of low V/Q were seen either before or during PP. Almost no regions of high V/Q developed during PP (1% of total ventilation). Pa(o₂) increased from 33 (1.2) to 35.7 (3.2) kPa (P<0.01) and arterial to end-tidal Pco₂ gradient (Pae'(co₂) increased from 0.3 (0.1) to 0.6 (0.2) kPa (P<0.05).

CONCLUSIONS

Perfusion was redistributed away from dorsal, collapsed lung regions when PP was established. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction.

Development of atelectasis and arterial to end-tidal PCO2-difference in a porcine model of pneumoperitoneum

BACKGROUND

Intraperitoneal insufflation of carbon dioxide (CO2) may promote collapse of dependent lung regions. The present study was undertaken to study the effects of CO2-pneumoperitoneum (CO2-PP) on atelectasis formation, arterial oxygenation, and arterial to end-tidal PCO2-gradient (Pa-E'(CO2)).

METHODS

Fifteen anaesthetized pigs [mean body weight 28 (SD 2) kg] were studied. Spiral computed tomography (CT) scans were obtained for analysis of lung tissue density. In Group 1 (n=5) mechanical ventilation (V(T)=10 ml kg (-1), FI(O2)=0.5) was applied, in Group 2 (n=5) FI(O2) was increased for 30 min to 1.0 and in Group 3 (n=5) negative airway pressure was applied for 20 s in order to enhance development of atelectasis. Cardiopulmonary and CT data were obtained before, 10, and 90 min after induction of CO2-PP at an abdominal pressure of 12 mmHg.

RESULTS

Before CO2-PP, in Group 1 non-aerated tissue on CT scans was 1 (1)%, in Group 2 3 (2)% (P<0.05, compared with Group 1), and in Group 3 7 (3)% (P<0.05, compared with Group 1 and Group 2). CO2-PP significantly increased atelectasis in all groups. PaO2/FI(O2) fell and venous admixture ('shunt') increased in proportion to atelectasis during anaesthesia but CO2-PP had a varying effect on PaO2/FI(O2) and shunt. Thus, no correlation was seen between atelectasis and PaO2/FI(O2) or shunt when all data before and during CO2-PP were pooled. Pa-E'(CO2), on the other hand correlated strongly with the amount of atelectasis (r2=0.92).

CONCLUSIONS

Development of atelectasis during anaesthesia and PP may be estimated by an increased Pa-E'(CO2).

Effects of propofol and desflurane anaesthesia on the alveolar inflammatory response to one-lung ventilation

BACKGROUND

One-lung ventilation (OLV) induces a pro-inflammatory response including cytokine release and leucocyte recruitment in the ventilated lung. Whether volatile or i.v. anaesthetics differentially modulate the alveolar inflammatory response to OLV is unclear.

METHODS

Thirty patients, ASA II or III, undergoing open thoracic surgery were randomized to receive either propofol 4 mg kg(-1) h(-1) (n = 15) or 1 MAC desflurane in air (n = 15) during thoracic surgery. Analgesia was provided by i.v. infusion of remifentanil (0.25 microg kg(-1) min(-1)) in both groups. The patients were mechanically ventilated according to a standard protocol during two-lung ventilation and OLV. Fibre optic bronchoalveolar lavage (BAL) of the ventilated lung was performed before and after OLV and 2 h postoperatively. Alveolar cells, protein, tumour necrosis factor alpha (TNFalpha), interleukin (IL)-8, soluble intercellular adhesion molecule-1 (sICAM), IL10, and polymorphonuclear (PMN) elastase were determined in the BAL fluid. Data were analysed by parametric or non-parametric tests, as indicated.

RESULTS

In both groups, an increase in pro-inflammatory markers was found after OLV and 2 h postoperatively; however, the fraction of alveolar granulocytes (median 63.7 vs 31.1%, P < 0.05) was significantly higher in the propofol group compared with the desflurane group. The time courses of alveolar elastase, IL-8, and IL-10 differed between groups, and alveolar TNFalpha (7.4 vs 3.1 pg ml(-1), P < 0.05) and sICAM-1 (52.3 vs 26.3 ng ml(-1), P < 0.05) were significantly higher in the propofol group.

CONCLUSIONS

These data indicate that pro-inflammatory reactions during OLV were influenced by the type of general anaesthesia. Different patterns of alveolar cytokines may be a result of increased granulocyte recruitment during propofol anaesthesia.

Somatosensorisch evozierte Potenziale und biochemische Marker neuronaler Defizite während Endarterektomie der A. carotis in Regionalanästhesie

OBJECTIVE OF THE STUDY

Carotid endarterectomy (CEA) remains the standard procedure for primary and secondary prevention of stroke. Somato-sensory evoked potentials (SEP) are frequently used in carotid endarterectomy under general anaesthesia and recommended for monitoring cerebral functions. The aim of the study was to compare changes in SEP and serum levels of S-100 beta protein and neuron-specific enolase (NSE) with perioperative clinical neurological deficits in patients undergoing regional anaesthesia (RA).

PATIENTS AND METHODS

After approval of the ethics committee of the Otto-von-Guericke-University, Magdeburg fifty patients undergoing elective CEA under RA were prospectively investigated. RA was performed by combined deep and superficial cervical plexus blockade. SEP was monitored continuously during the surgical procedure. A more of 50 % decrease of potentials (N 20 / P 25 amplitude) compared to potentials before clamping was considered to be significant. Arterial blood samples were collected preoperatively, before declamping and on the first postoperative day to determine serum levels of S-100 beta and NSE.

RESULTS

12 patients developed intraoperatively neurological deficits with carotid clamping. The symptoms were transient and regressed in one minute after shunting. One patient was discharged with persistent hemiparesis. In 8 of 12 patients (66 %) with neurological deficits a more of 50 % decrease of potentials was observed. In one patient with loss of consciousness and hemiparesis changes in SEP or decrease in N 20 / P 25 amplitude were absent. Decrease in amplitude was in patients with intraoperative neurological deficits with 78 % versus 34 % in patients without any deficits significantly reduced (p = 0.01). The sensitivity of monitoring was 67 % at a specificity of 74 %. Serum levels of S-100 beta increased before declamping between patients with and without any neurological deficits significantly (p = 0.02). On the first postoperative day, increased levels of S-100 beta correlated with decrease in amplitude (p = 0.001).

CONCLUSION

Compared to SEP, CEA under regional anaesthesia is a safer method to detect patients with cerebral ischaemia before irreversible cellular brain damage occurs. Measuring blood levels of S-100 beta could help to evaluate patients with risk to develop cerebral ischaemia during clamping.

Anesthetic considerations in patients with previous thoracic surgery

PURPOSE OF THE REVIEW

This review presents an overview of the different problems and challenges after thoracic surgery. It covers the pathophysiological changes that may occur regularly in the early and late period following surgery. In addition, surgical complications with anesthesiological implications for diagnosis, treatment and prevention are discussed, and consequences for anesthesia in further major and thoracic surgical procedures are shown.

RECENT FINDINGS

During the last decade, complications in the early period following surgery after thoracotomy have increasingly moved into the focus caused by their high morbidity and mortality. These problems, such as hemorrhagia and bronchopleural fistulas, are important because they call for a prompt revision or even an emergency operation. The therapy of acute bleeding follows general anesthesiological guidelines whereas the bronchopleural fistula demands methods to prevent aspiration pneumonia as a first priority. In the late period following surgery, typical cardiac and pulmonary modifications can be described that persist and have anesthesiological implications in the case of further surgery. Recent literature, however, lacks clear recommendations regarding anesthesiological management and practice for these cases.

SUMMARY

Current literature presents no general recommendations on how to manage patients after recent thoracic surgery. Therefore it is necessary to find an individual strategy to handle possible complications and well known pathophysiological changes. Knowledge and understanding of the etiology, the pathophysiology and the risk factors of the perioperative period, allows prevention and target intervention aimed at reducing morbidity and mortality following surgery.

Effects of different anaesthetic agents on immune cell function in vitro

BACKGROUND AND OBJECTIVE

Anaesthesia may affect the regulatory balance of postoperative immune response. The aim of this study was to investigate the effects of different volatile and non-volatile anaesthetic agents and particularly of clinically used agent combinations on the proliferation capacity and cytokine production of immune cells.

METHODS

Peripheral blood mononuclear cells from healthy donors were PHA-activated in the presence or absence of various concentrations of thiopental, propofol, fentanyl, sufentanil, sevoflurane, nitrous oxide and combinations of these anaesthetics. Cell proliferation was assessed by tritiated thymidine uptake. Interleukin-2 production and release of the soluble IL-2 receptor were determined by enzyme immunoassays and used as measures of lymphocyte activation.

RESULTS

Thiopental inhibited cell proliferation in a dose dependent manner (P < 0.001) and reduced sIL-2R release (2090-970 microg mL(-1); P < 0.05). Propofol reduced sIL-2R release at the high concentration of 10 microg mL(-1) (2220 pg mL(-1) 1780 microg mL(-1); p < 0.05). Fentanyl and sufentanil did not compensate for or enhance the inhibitory effects of thiopental. Nitrous oxide, but not sevoflurane, reduced the proliferation of human peripheral blood mononuclear cells (P < 0.05). In combinations with thiopental or nitrous oxide, sevoflurane compensated the inhibitory effects of these two agents. Fentanyl, sufentanil, sevoflurane and nitrous oxide did not affect PHA-induced IL-2 and sIL-2 receptor release by human peripheral blood mononuclear cells.

CONCLUSION

Thiopental and nitrous oxide have immunosuppressive activity. In contrast, sevoflurane may have a beneficial effect by alleviating the immunosuppressive effects of both substances.

Trikuspidalklappenersatz bei einer heroinabhängigen Patientin

A 24-year-old female with a history of former heroin addiction underwent open heart surgery for a mechanical tricuspid valve replacement. Anaesthesiological management included a thoracic epidural catheter at the Th(2)/Th(3) segments and balanced general anaesthesia (remifentanil, desflurane/propofol). Additionally, clonidine (2 microg*kg(-1)*h(-1)) was continuously administered. Pain therapy was achieved using 0.375% ropivacaine via a thoracic epidural catheter (4 ml*h(-1)) and metamizole (4 x 1 g/day) intravenously. With this concept we were able to achieve an appropriate anaesthesia and analgesia and the operation was carried out without complications.

Influence of muscle relaxation on neuromonitoring of the recurrent laryngeal nerve during thyroid surgery

BACKGROUND

The influence of muscle relaxation on the intra-operative neuromonitoring of the recurrent laryngeal nerve during thyroid surgery is unclear.

METHODS

In a prospective study involving 200 patients undergoing elective thyroid surgery, the influence of muscle relaxation on neuromonitoring of the recurrent laryngeal nerve was investigated. The patients received balanced anaesthesia with oxygen-nitrous oxide-isoflurane, and rocuronium bromide was used as the non-depolarizing neuromuscular blocking agent. The degree of relaxation was monitored continuously by accelerometry [twitch (% TW)]. Summed action potentials (SAcP) obtained from the vocalis muscle were characterized by the area under the electromyographic curve expressed in millivolt seconds.

RESULTS

Evoked potentials were obtainable in all patients and at all time points. With decreasing neuromuscular blockade a significant increase in the potentials evoked at the vocalis muscle was observed. At 0% TW SAcP was 1.27 (SD 1.02) mV s. An increase in TW to 10% was accompanied by an increase in SAcP to 2.68 (2.01) mV s (P<0.01). At a TW of 25%, mean SAcPs of 5.08 mV s were recorded.

CONCLUSIONS

There was a significant difference in the degree of relaxation of the adductor pollicis muscle and the vocalis muscle. The laryngeal muscles exhibited a shorter response time than the adductor pollicis and recovered more quickly. These results confirm the feasibility of intra-operative neuromonitoring of the recurrent laryngeal nerve during neuromuscular blockade.

[Is the pneumoperitoneum minimally invasive during laparoscopic colonic surgery?]

The importance of laparoscopic colonic surgery has increased considerably in the past decade. However, a minimally invasive operation with induction of pneumoperitoneum does not imply a minimally invasive anaesthesia. The haemodynamic effects of intraperitoneal carbon dioxide insufflation depend an the extent of intraabdominal pressure elevation, severity of preexisting cardiopulmonary diseases, alterations of arterial PCO (2) and pH, volume state of the patient and co-medications. In addition, positioning of the patient for laparoscopic colonic surgery and endocrinological reactions during and after induction of pneumoperitoneum may significantly affect systemic and pulmonary haemodynamics. Intraabdominal operations may impair respiratory function independent from anaesthesia. Preoperative evaluation of the high risk patient is of utmost importance. Assessment of expiratory PCO (2), extended cardiopulmonary monitoring and maintenance of intraabdominal pressure in the range of 5 - 7 mmHg are recommended during laparoscopic colonic surgery.

Cardiopulmonary effects of non-invasive positive pressure ventilation (NPPV)--a controlled, prospective study

BACKGROUND

This study was undertaken to investigate the haemodynamic effect of non-invasive positive pressure ventilation (NPPV) in patients after cardiac surgery. NPPV has recently become popular as method for treating acute respiratory failure. Its influence on cardiopulmonary haemodynamics is still unknown.

METHODS

30 extubated low-risk patients were included in four study intervals after cardiac surgery. During the first and the third interval, the patients breathed spontaneously and received oxygen via face mask for 45 min. Both intervals were followed by 45 min on NPPV.

RESULTS

Cardiac index increased significantly from 2.8 to 3.1 ml/min/m2 during NPPV (p < 0.001) and from 2.7 to 3.2 ml/ min/m2 (p < 0.001). Mixed venous saturation rose significantly from 72.4 to 74.8 % (p < 0.001) and from 72.1 to 75.4 % (p < 0.001) during NPPV while the oxygen extraction ratio decreased from 25.5 and 26.1 % to 23.0 (p < 0.001) and 22.6 % (p < 0.001) during NPPV. At the same time, urine production increased significantly from 182 to 328 ml/h and from 186 to 285 ml/h (p < 0.001). Heart rate and mean arterial blood pressure rose significantly during NPPV. There were no significant changes in systemic and pulmonary haemodynamics, oxygenation or CO 2 elimination.

CONCLUSIONS

NPPV improves CI significantly in stable cardiac surgery patients. Factors other than blood pressure, vascular resistance or blood gases must exert an additional influence on CI. They are still not identified. Changes in transmural pressure during NPPV may play an important role.

Endocrine effects of dopexamine vs. dopamine in high-risk surgical patients

OBJECTIVES

To compare the endocrine effects of dopexamine and dopamine on prolactin (PRL), dihydroepiandrosterone sulfate (DHEAS), cortisol, thyrotropin (TSH), and peripheral thyroid hormone serum concentrations in surgical patients at risk of developing postoperative complications because of hypoperfusion of various organ systems.

DESIGN AND SETTING

A prospective, randomized, placebo-controlled, blinded clinical trial in an adult surgical intensive care unit in a university hospital.

PATIENTS

Thirty-two male surgical risk patients undergoing elective major abdominal surgery.

INTERVENTIONS

Patients were randomized to receive placebo ( n=8), dopexamine (0.5 microg kg(-1) min(-1), n=8), dopexamine (1 microg kg(-1) min(-1), n=8) or dopamine (5 microg kg(-1) min(-1), n=8) on the first postoperative day.

MEASUREMENTS AND RESULTS

All patients received either a placebo or catecholamine infusion for 24 h. Blood samples were obtained every 2 h for the next 2 days. PRL, DHEAS, cortisol, TSH, triiodothyronine, thyroxin, free triiodothyronine, and free thyroxin serum concentrations were determined by radioimmunoassay or luminescence immunoassay. Dopexamine (0.5 microg kg(-1) min(-1)) had no effects on serum concentrations of PRL or TSH. Higher doses of dopexamine (1 microg kg(-1) min(-1)) suppressed PRL secretion significantly, but not TSH. In contrast, infusion of dopamine (5 microg kg(-1) min(-1)) completely inhibited PRL and TSH secretion. DHEAS, cortisol, and thyroid hormone serum concentrations were not affected by either dopexamine or dopamine infusion. Measurements of hemodynamic parameters, peripheral oxygen saturation, diuresis, blood gases, and standard laboratory parameters were repeated hourly. Significant differences were not found between placebo, dopexamine (0.5 microg kg(-1) min(-1)) and dopamine (5 microg kg(-1) min(-1)) group. Dopexamine at 1 microg kg(-1) min(-1) increased the heart rate significantly.

CONCLUSIONS

Routine postoperative optimizing of men undergoing abdominal surgical procedures with dopexamine at higher doses or dopamine induces at least partial hypopituitarism, which may possibly affect postoperative morbidity.