Extracorporeal carbon dioxyde removal for additional pulmonary resection after pneumonectomy

Additional pulmonary surgery in a previously pneumonectomized patient requires apnea during surgical manipulation of the surviving lung. We report on a novel approach to manage the intraoperative apnea period, combining apneic oxygenation and minimally invasive, low flow extracorporeal CO2 removal. A 69-year-old man previously submitted to left pneumonectomy was scheduled for wedge resection of a single right upper lobe lesion. During the intraoperative apnea period, oxygenation was maintained through apneic oxygenation with continuous positive airway pressure (CPAP) of 5 cmH2O and inspiratory oxygen fraction (FiO2) of 1 and respiratory acidosis was prevented through extracorporeal CO2 removal, performed with the Decap® system (Hemodec, Salerno, Italy), a veno¬venous pump-driven extracorporeal circuit including a neonatal membrane lung. The extracorporeal circuit was connected to the right femoral vein, accessed via a 14 Fr double lumen catheter. The blood flow through the circuit was 350 mL/min and the sweep flow of oxygen through the membrane lung was 8 L/min. The intraoperative apnea period lasted 13 minutes. Our approach allowed maintaining normocapnia (PaCO2 38,5 and 40 mmHg before and at the end of the apnea period, respectively), preserving oxygenation (P/F ratio 378, 191, 198 and 200 after 3, 6, 9 and 12 min of apnea, respectively). Our report suggests that the minimally invasive CO2 removal associated with apneic oxygenation is an useful technique for managing anesthesiological situations requiring moderate apnea periods.

Damage control resuscitation for the Special Forces medic: simplifying and improving prolonged trauma care: Part One

Current operational theaters have developed to where medical evacuation and surgical assets are accessible in times comparable to the United States. While this has been an essential tool in achieving the best survivability on a battlefield in our history, the by-product of this experience is a recognized shortcoming in current protocols and capabilities of Special Forces medics for prolonged care. The purpose of this article is to provide a theory of care, identify training and support requirements, and to capitalize on current successful resuscitation theories in developing a more efficient and realistic capability under the worst conditions.

MONITORING OF THE VENTILATORY STATUS OF ANESTHETIZED BIRDS OF PREY BY USING END-TIDAL CARBON DIOXIDE MEASURED WITH A MICROSTREAM CAPNOMETER

The relationship between end-tidal partial pressure of carbon dioxide (PETCO2), arterial partial pressure of carbon dioxide (PaCO2), and blood pH in isoflurane-anesthetized raptors was evaluated. PaCO2 and pH were determined in serial arterial samples from isoflurane anesthetized birds and compared with concurrent end-tidal partial pressure of carbon dioxide measured with a Microstream sidestream capnograph. Forty-eight paired samples, taken from 11 birds of prey (weighing 416-2,062 g), were used to determine correlations coefficients between PaCO2 and PETCO2, and between PETCO2 and pH. Limits of agreement between PaCO2 and PETCO2 also were calculated. Strong correlations were observed between PaCO2 and PETCO2 (r = 0.94; P < 0.0001) as well as between PETCO2 and pH (r = -0.90; P < 0.0001). However, the level of agreement between PaCO2 and PETCO2 varied considerably. Low values of PETCO2, ranging from 18 to 29 mm Hg, exceeded the concomitantly measured values of PaCO2 by an average of 6.0 mm Hg (6.0 +/- 1.9 mm Hg; mean +/- SD). Conversely, high values of PETCO2, ranging from 50 to 63 mm Hg, were on average 7.6 mm Hg (7.6 +/- 9.8 mm Hg) lower than values of PaCO2. In the 30 to 49 mm Hg range for PETCO2, the difference between PETCO2 and PaCO2 was on average 1.0 mm Hg (1.0 +/- 8.5 mm Hg). These results suggest that the capnograph used provided a sufficiently accurate estimation of arterial partial pressure of carbon dioxide for birds weighing > 400 g and receiving manual positive ventilation with a Bain system. In our study, the linear relationship observed between the pH and the end-tidal partial pressure of carbon dioxide suggested that the monitoring of end-tidal partial pressure of carbon dioxide also can be useful to prevent respiratory acidosis.

Oxygen alert cards and controlled oxygen: preventing emergency admissions at risk of hypercapnic acidosis receiving high inspired oxygen concentrations in ambulances and A&E departments

BACKGROUND

Appropriate resuscitation of hypoxic patients is fundamental in emergency admissions. To achieve this, it is standard practice of ambulance staff to administer high concentrations of oxygen to patients who may be in respiratory distress. A proportion of patients with chronic respiratory disease will become hypercapnic on this.

OBJECTIVES AND METHODS

A scheme was agreed between the authors' hospital and the local ambulance service, whereby patients with a history of previous hypercapnic acidosis with a Pao2 >10.0 kPa--indicating that oxygen may have worsened the hypercapnia--are issued with "O2 Alert" cards and a 24% Venturi mask. The patients are instructed to show these to ambulance and A&E staff who will then use the mask to avoid excessive oxygenation. The scheme was launched in 2001 and this paper present the results of an audit of the scheme in 2004.

RESULTS

A total of 18 patients were issued with cards, and 14 were readmitted on 69 occasions. Sufficient documentation for auditing purposes was available for 52 of the 69 episodes. Of these audited admissions, 63% were managed in the ambulance, in line with card-holder protocol. This figure rose to 94% in the accident and emergency department.

CONCLUSION

These data support the usability of such a scheme to prevent iatrogenic hypercapnia in emergency admissions.

Comparison of pH-Stat Versus Alpha-Stat During Hypothermic Cardiopulmonary Bypass in the Prevention and Control of Acidosis in Cardiac Surgery

OBJECTIVES

To compare the effects of blood-gas management using either alpha-stat (temperature-uncorrected blood-gas management) or pH-stat (temperature-corrected blood-gas management) strategies, 30 patients undergoing coronary artery bypass surgery allocated randomly to either one of the approaches were studied. Acid-base balance, tissue oxygenation, and biochemical parameters were measured at distinct times: before bypass, after 15 min of hypothermia at 32 degrees C, after 45 min of hypothermia at 32 degrees C, after 15 min of rewarming at 37 degrees C, and 45 min after the end of bypass in normothermic conditions.

RESULTS

The groups were similar with regard to physical characteristics, physiological parameters, and bypass time. In the pH-stat group, CO2 administered with the aim of correcting pH for the patients hypothermic temperature caused a significant increase in temperature-uncorrected PaCO2 and a decrease in arterial temperature-uncorrected pH at 45 min. During the rewarming period and following bypass, the pH was lower and PaCO2 higher in the pH-stat group (P < 0.001).

CONCLUSION

It was found that during the rewarming period and following bypass, the resulting acidosis caused by the procedure was less in the alpha-stat group. It was found that there were no difference between the two groups, with regard to tissue perfusion, as is seen by the tissue oxygenation parameters and lactic acid concentration.

Tracheal double-lumen ventilation attenuates hypercapnia and respiratory acidosis in lung injured pigs

OBJECTIVE

Evaluation of ventilatory and circulatory effects with coaxial double-lumen tube ventilation for dead-space reduction as compared with standard endotracheal tube ventilation.

DESIGN

Experimental study in a pig model of lung lavage induced acute lung injury.

SETTING

University research laboratory.

MEASUREMENTS AND RESULTS

Tidal volumes of 6, 8 and 10 ml/kg body weight with a set respiratory rate of 20 breaths per minute were used in a random order with both double-lumen ventilation and standard endotracheal tube ventilation. Measurements of ventilatory and circulatory parameters were obtained after steady state at each experimental stage. With a tidal volume of 6 ml/kg, PaCO(2) was reduced from 10.9 kPa (95% CI 9.0-12.9) with a standard endotracheal tube to 8.2 kPa (95% CI 7.0-9.4) with double-lumen ventilation. This corresponds to a reduction in carbon dioxide levels by 25%. At 6 ml/kg, pH increased from 7.17 (95% CI 7.09-7.24) with a standard endotracheal tube to 7.27 (95% CI 7.21-7.32) with double-lumen ventilation. Tracheal pressure was monitored continuously and no difference between single- or double-lumen ventilation was noted at corresponding levels of ventilation. There was no formation of auto-PEEP. Partial tube obstruction due to secretions was not observed during the experiments.

CONCLUSIONS

Coaxial double-lumen tube ventilation is an effective adjunct to reduce technical dead space. It attenuates hypercapnia and respiratory acidosis in a lung injury pig model.

Permissive hypercapnia--role in protective lung ventilatory strategies

"Permissive hypercapnia" is an inherent element of accepted protective lung ventilation. However, there are no clinical data evaluating the efficacy of hypercapnia per se, independent of ventilator strategy. In the absence of such data, it is necessary to determine whether the potential exists for an active role for hypercapnia, distinct from the demonstrated benefits of reduced lung stretch. In this review, we consider four key issues. First, we consider the evidence that protective lung ventilatory strategies improve survival and we explore current paradigms regarding the mechanisms underlying these effects. Second, we examine whether hypercapnic acidosis may have effects that are additive to the effects of protective ventilation. Third, we consider whether direct elevation of CO(2), in the absence of protective ventilation, is beneficial or deleterious. Fourth, we address the current evidence regarding the buffering of hypercapnic acidosis in ARDS. These perspectives reveal that the potential exists for hypercapnia to exert beneficial effects in the clinical context. Direct administration of CO(2) is protective in multiple models of acute lung and systemic injury. Nevertheless, several specific concerns remain regarding the safety of hypercapnia. At present, protective ventilatory strategies that involve hypercapnia are clinically acceptable, provided the clinician is primarily targeting reduced tidal stretch. There are insufficient clinical data to suggest that hypercapnia per se should be independently induced, nor do outcome data exist to support the practice of buffering hypercapnic acidosis. Rapidly advancing basic scientific investigations should better delineate the advantages, disadvantages, and optimal use of hypercapnia in ARDS.

Carbon dioxide added late in inspiration reduces ventilation-perfusion heterogeneity without causing respiratory acidosis

We have shown previously that inspired CO2 (3-5%) improves ventilation-perfusion (Va/Q) matching but with the consequence of mild arterial hypercapnia and respiratory acidosis. We hypothesized that adding CO2 only late in inspiration to limit its effects to the conducting airways would enhance Va/Q matching and improve oxygenation without arterial hypercapnia. CO2 was added in the latter half of inspiration in a volume aimed to reach a concentration of 5% in the conducting airways throughout the respiratory cycle. Ten mixed-breed dogs were anesthetized and, in a randomized order, ventilated with room air, 5% CO2 throughout inspiration, and CO2 added only to the latter half of inspiration. The multiple inert-gas elimination technique was used to assess Va/Q heterogeneity. Late-inspired CO2 produced only very small changes in arterial pH (7.38 vs. 7.40) and arterial CO2 (40.6 vs. 39.4 Torr). Compared with baseline, late-inspired CO2 significantly improved arterial oxygenation (97.5 vs. 94.2 Torr), decreased the alveolar-arterial Po2 difference (10.4 vs. 15.7 Torr) and decreased the multiple inert-gas elimination technique-derived arterial-alveolar inert gas area difference, a global measurement of Va/Q heterogeneity (0.36 vs. 0.22). These changes were equal to those with 5% CO2 throughout inspiration (arterial Po2, 102.5 Torr; alveolar-arterial Po2 difference, 10.1 Torr; and arterial-alveolar inert gas area difference, 0.21). In conclusion, we have established that the majority of the improvement in gas exchange efficiency with inspired CO2 can be achieved by limiting its application to the conducting airways and does not require systemic acidosis.

pH-stat ventilation management: a simple method of achieving this regimen

Since the advent of extracorporeal circulation for life support during cardiac surgery, there have been varied opinions as to the best method of ventilating an oxygenator to achieve the optimum arterial blood gas. With respect to the optimum pCO2, clinical investigators have focused primarily on the pros and cons of the alpha-stat and pH-stat ventilation schemes. pH-stat is a ventilation scheme that attempts to maintain the temperature corrected pH of the arterial blood at 7.40, no matter what the actual temperature of the blood. This paper does not attempt to elucidate the benefits of one scheme over the other, but is offered to provide perfusionists with a simple method of achieving pH-stat ventilation, using a CO2 source and materials readily available in any operating room. Strict adherence to a few cautionary notes should enable any perfusionist to safely deliver pH-stat ventilation when indicated. This technique of providing pH-stat ventilation has been used at our institution for over three years. It has proven to be easy to accomplish, adjust and maintain.

Ability and safety of a heated humidifier to control hypercapnic acidosis in severe ARDS

OBJECTIVE

To assess the ability of a heated humidifier to improve CO(2) clearance in ARDS patients submitted to protective ventilation.

DESIGN

Prospective clinical study.

SETTING

University hospital intensive care unit.

PATIENTS

During a 12-month period, we studied 11 ARDS patients under protective mechanical ventilation with severe hypercapnia.

INTERVENTION

When PaCO(2) was above 55 mmHg, the heat and moisture exchanger (HME) was removed and patients were ventilated using a heated humidifier (HH) until their recovery or death. The heated humidifier was inserted on the inspiratory limb of the respirator and the inspirated air was saturated to achieve a temperature of 40 degrees C at the Y connector of ventilator tubing and of 37 degrees C at the outlet of the endotracheal tube.

MEASUREMENTS AND RESULTS

Mechanical measurements and blood gas analysis were performed just before removal of the HME, and 30 min after mechanical ventilation using HH. Ventilator parameters were kept constant in the two conditions. Using HH instead of HME, PaCO(2) was safely decreased by 11+/-5 mmHg, without any need to change respiratory rate. No significant difference was noted in intrinsic PEEP or airway plateau pressure. Decrease in PaCO(2) after HME removal was strongly correlated with the initial value of PaCO(2).

CONCLUSION

Supposing there is an interest in correcting or limiting hypercapnic acidosis in ARDS patients submitted to protective ventilation, HME removal and use of HH appears to be an efficient and safe way of increasing CO(2) clearance.

[Can subpartal fetal acidosis be avoided? Investigations on the complex causes of intrauterine asphyxia]

OBJECTIVE

The extent to which faulty medical treatment and defective apparatus are concomitant causes for the development of subpartal acidosis was investigated in a retrospective study. At the same time, the incidence of acidosis in the Lippe-Detmold Hospital, Department of Gynaecology and Obstetrics, its morbidity and mortality were analysed.

METHODS

Data from all case histories of neonates with acidosis (pH in the umbilical artery < 7.100) who were born between 1 st January 1992 and 31 st December 1998 at the Department of Gynecology and Obstetrics at the Lippe-Detmold Hospital were evaluated electronically. Analytical measurements of blood gases (pH, pCO 2 and pO 2 ) in umbilical artery and venous blood were available from all cases. The base excess was corrected by computations according to Siggaard-Andersen and R. Zander for the actual oxygen saturation. The delivery cardiotocograms (CTG) were appraised qualitatively. Equipment defects, mistakes on the part of doctors and/or midwives (including the head of the department) were recorded after critical analysis of each individual case and documented in accordance with a key. The neonatal data were taken from the files of the paediatric division of the hospital (head of the department Dr. K. Wesseler).

RESULTS

In seven years under report, 9.876 babies were born, 156 (1.58 %) of whom showed a pH of less than 7.100 in the umbilical arterial blood. The mean actual pH value was 7.047 +/- 0.058, and the oxygen-corrected base excess was - 16.3 +/- 3.2 mmol/l. Correction of the base excess resulted in a numerical lowering by about 2.0 mmol/l. The rate of premature births was 17.4 %. One newborn baby died of hypoxic shock (0.67 %). 94 % of these neonates could be discharged in a healthy condition. 4.6 % still showed symptoms on discharge. Disorders of respiratory adaptation were the most prominent feature in morbidity from acidosis (about 18 %). Only two babies showed neonatal convulsions. Renal, cardiac and haemostaseological complications were rarely observed. Only 5 (3.9 %) of the 128 neonates with available recordings did not show any pathological changes in the CTG. 26.4 % of all acidoses had to be designated as "pure fate". In a further 35 % medical mistakes could not be discerned. Consequently, 61.4 % of the acidoses had to be designated as "unavoidable". In the remaining roughly 40 %, inadequate cardiotocographical knowledge, inattentiveness, defective equipment etc. clearly played a causal role. In the severe cases (pH in the umbilical artery < 7.000), medical mistakes were much more frequent (50 %).

CONCLUSIONS

Three-fifths of all subpartal acidoses in this study have a fateful nature, i.e. they cannot be prevented even by optimal professional management in good time. About two-fifths are avoidable if appropriate equipment and trained staff are available around the clock. Use of cardiotocography alone enables the threat of asphyxia to be detected in 97 % of the cases. The short-term prognosis of subpartal acidosis is good provided very low pH values (< 6.900) can be avoided. In perinatological studies, the base excess value should be corrected by computation. "Quality control" worthy of the name should include critical single-case analysis at least in severe acidosis.

[Noninvasive intermittent positive pressure ventilation in treatment of chronic respiratory disease exacerbation]

Noninvasive intermittent positive pressure ventilation (NIPPV) via nasal mask became a routine method of treatment of severe exacerbations of chronic respiratory failure. The aim of the study was to apply NIPPV in patients with COPD admitted to hospital due to exacerbation of the disease who on standard treatment developed progressing respiratory acidosis (pH < 7.30). Fourteen COPD patients were treated with NIPPV. Arterial blood gases at the beginning of treatment were: PaO2 41 +/- 9 mmHg, PaCO2 = 87 +/- 17 mmHg, pH = 7.30 +/- 0.05. In 10 patients NIPPV applied quasi continuously resulted in clinical improvement and an amelioration of arterial blood gases. PaO2 rose from 41 +/- 9 mmHg to 56 +/- 12 mmHg, PaCO2 fell from 85 +/- 17 to 57 +/- 9 mmHg and pH rose from 7.30 +/- 0.05 to 7.41 +/- 0.04. In 4 patients NIPPV did not prevent further progression of respiratory acidosis. They were intubated and mechanically ventilated. Three patients survived and were discharged home. One patient died from septic shock. We conclude that NIPPV is an effective method to treat respiratory acidosis developing during exacerbation of severe COPD.

Effects of inspired gas content during respiratory arrest and cardiopulmonary resuscitation

Mouth-to-mouth and bag-valve-mask ventilation have been an indispensable part of cardiopulmonary resuscitation (CPR). However, only recently have the effects of different tidal volumes on arterial oxygenation been reported for mouth-to-mouth and bag-valve-mask ventilation. Currently recommended tidal volumes (10-15 mL/kg) are associated with an increased risk of gastric inflation because they produce high peak inspiratory pressures. An animal model of ventilation with an unprotected airway showed that a smaller tidal volume (6 mL/kg) is as effective as a larger tidal volume (12 mL/kg) in maintaining Sao2 at >96%. However, a smaller tidal volume with exhaled gas ventilation produced a mean Sao2 of 48%, which is ineffective. Ventilation gas mixtures have been studied in models of cardiac arrest and CPR. One study showed that ventilation with air during 6 mins of CPR resulted in a return of spontaneous circulation in 10 of 12 animals compared with only 5 of 12 animals ventilated with exhaled gas (p<.04). Arterial and mixed-venous Po2 were significantly higher, and Pco2 was significantly lower in the air ventilation group. Investigations of the cardiovascular effects of mouth-to-mouth ventilation during CPR suggest that there are adverse effects during low blood flow states. However, mouth-to-mouth ventilation during respiratory arrest is lifesaving and should continue to be taught and emphasized in basic life support courses.

Combined lung injury, meningitis and cerebral edema: how permissive can hypercapnia be?

We describe a patient with combined meningococcal septicemia and meningitis, cerebral edema and acute respiratory distress syndrome, in whom we balanced the conflicting carbon dioxide strategies for optimal pulmonary and neurological management using jugular oxygen saturation (SjvO2) monitoring to identify the upper limit of "tolerable" hypercapnia. Our observations suggest that significant acidosis was not well tolerated; however, cautious induction of pH down to 7.32 and an arterial carbon dioxide tension (PaCO2) < 5.9 kPa was tolerated acutely without significant cerebral hyperemia. Moreover, with the development of metabolic compensation and normal pH, higher levels of PaCO2 could be permitted. In similar cerebro-pulmonary circumstances we suggest that these findings warrant consideration. Alternatively, invasive monitoring of SjvO2 could be undertaken so that patient-specific criteria for permissive hypercapnia can be determined.

Comparative stress hormone changes during helium versus carbon dioxide laparoscopic cholecystectomy

Laparoscopic surgery has been termed minimally invasive surgery by advocates of this technology. It has been demonstrated previously that using carbon dioxide for insufflation produces a respiratory acidosis due to transperitoneal absorption of gas. Insufflation with helium does not create this acidosis. We questioned whether laparoscopic surgery would elicit a stress response and whether the absence of acidosis with helium might prevent or reduce the levels of stress hormones. Sixteen female patients undergoing laparoscopic cholecystectomy were randomly assigned to helium (n = 8) or CO2 (n = 8) insufflation. Serum cortisol, epinephrine, and norepinephrine were measured preoperatively, after induction of anesthesia but before insufflation, at 45 min of surgery, and after desufflation. There were increases in epinephrine, norepinephrine, plasma cortisol, and urine cortisol at 45 min and at the conclusion of the procedure over the preoperative value. With ANOVA, each variable showed significant increases from preoperative values, at 45 min, and at the end of the case. Except for the increased epinephrine when helium was used, there were no significant differences in the other variables between helium and CO2. Laparoscopic cholecystectomy produces significant increases in stress hormone levels. Prevention of acidosis with helium insufflation does not appear to protect against increases in stress hormones. Epinephrine levels with helium insufflation are higher than with CO2, and elevations in stress hormones suggest that laparoscopic cholecystectomy is not physiologically minimally invasive.

Comparison of vecuronium and meperidine on the clinical and metabolic effects of shivering after hypothermic cardiopulmonary bypass

The use of vecuronium and meperidine on the clinical and metabolic effects of shivering in mechanically ventilated patients after hypothermic cardiopulmonary bypass (CPB) was compared. Twenty adult male patients undergoing cardiac surgery were randomized to meperidine, 25 to 75 mg (n = 10), or vecuronium, 0.1 microgram/kg (n = 10), for the treatment of shivering during postoperative rewarming. Vecuronium was continued as an infusion at 1.0 microgram/kg/min for 4 hours. Meperidine abolished shivering in 50% of patients with a 60% recurrence within 2 hours and did not correct acute respiratory acidosis when it occurred. Vecuronium uniformly abolished shivering, corrected acute respiratory acidosis, and improved mixed venous oxygen saturation (20% v 4%), decreased oxygen consumption (-32% v -7%) and decreased end-tidal carbon dioxide (-21% v -5%) significantly more than meperidine (p < 0.005). Meperidine administration caused a significant decline in systolic blood pressure (121.9 +/- 10.6 mmHg to 106.9 +/- 8.5 mmHg, p = < 0.02). The authors conclude that, during rewarming after hypothermic CPB, muscle relaxation with vecuronium reverses both the clinical and metabolic effects of shivering more reliably and effectively than repeated boluses of meperidine, and with greater hemodynamic stability. Control can be maintained by continuous infusion of vecuronium with concomitant sedation for up to 4 hours without prolonging intubation time.

Preoperative pulmonary function evaluation for laparoscopic cholecystectomy

OBJECTIVE

Hypercarbia with respiratory acidosis is a recognized complication of laparoscopic cholecystectomy. This study was performed to identify preoperatively those patients who may develop hypercarbia and acidosis during the procedure.

DESIGN

Retrospective analysis of preoperative variables.

PATIENTS

Thirty-one consecutive patients underwent laparoscopic cholecystectomy at one institution who were receiving both preoperative pulmonary function tests and arterial blood gas analysis.

RESULTS

More than 80 demographic, laboratory, and perioperative variables were entered into a univariate analysis to identify predictors of intraoperative acidosis (pH, < 7.35). Patient age, duration of the procedure, and preoperative blood gas values were not predictors of intraoperative acidosis. Several univariant predictors for patients experiencing carbon dioxide pneumoperitoneum-induced hypercarbia were identified; these included an elevated American Society of Anesthesiologists classification and significant decreases in forced expiratory flow at 25% of maximum, maximal forced expiratory flow, maximal voluntary ventilation, vital capacity, inspiratory capacity, and diffusing capacity of the lung for carbon monoxide.

CONCLUSIONS

This study suggests that neither age nor preoperative arterial blood gas values are predictive of intraoperative hypercarbia and acidosis during periods of carbon dioxide pneumoperitoneum. However, preoperative pulmonary function measures of decreased flow, limited capacity, and compromised diffusion do correspond to the development of intraoperative acidosis. Preoperative evaluation with pulmonary function tests demonstrating forced expiratory volumes less than 70% of predicted values and diffusion defects less than 80% of predicted values can identify those patients who are at risk of developing hypercarbia and acidosis.

Mechanical ventilation. Physiology, equipment design, and management

The major goals of mechanical ventilation are the prevention of significant respiratory acidosis and the correction of arterial hypoxemia. Ventilators are categorized as negative- or positive-pressure types, depending on their effect on airway pressure. Positive-pressure ventilators, which are used in the treatment of acute respiratory failure, may be subclassified as pressure-, volume-, or time-cycled. Volume types provide stable tidal volumes and inspiratory oxygen concentrations over the range of changing ventilatory conditions seen in acute respiratory failure. Ventilation may be provided in a number of modes. No clear-cut advantage of intermittent mandatory ventilation over assisted mechanical ventilation has been demonstrated. By following simple guidelines, the clinician can initiate mechanical ventilation that provides an ideal ventilatory pattern.

Problems before, during and after mechanical ventilation in chronic bronchitis and emphysema

Recent work has shown considerable advance in the potential for treatment of patients with acute exacerbations of chronic respiratory failure, and the "blue and bloated" pattern of chronic bronchitis and emphysema. New guidelines for controlled oxygen therapy have been developed, which appear to enable the dangers of hypoxaemia and respiratory acidosis in an acute exacerbation to be reduced. New modalities of therapy, long-term oxygen treatment. Almitrine, and beta 2-agonists, hold promise of prolonging the survival of useful life in these severely afflicted patients.

Effects of acidemia and sodium bicarbonate therapy in advanced cardiac life support

Cardiac output using the currently recommended closed-chest cardiopulmonary resuscitation (CPR) technique is marginal (less than 30% of control), and eventually will result in tissue hypoperfusion and lactic acidemia. Intermittent sodium bicarbonate administration currently is recommended for treatment of this metabolic acidemia, and based on available data recommended dosages are empiric but sound. In this review the potential complications of acidemia and sodium bicarbonate administration are considered from the viewpoint of resuscitation outcome. In our opinion, available data are limited, and further evaluation and consideration of sodium bicarbonate requirements in the resuscitation setting are required.

Respiratory acidosis with the small Storz-Hopkins bronchoscopes: occurrence and management

Carbon dioxide retention in the Storz rigid ventilating bronchoscope with the Hopkins lens system was investigated in the laboratory. The 3.5, 4.0, and 5.0 30-cm Storz bronchoscopes with a 3.95-mm (outside diameter) telescope lens were used in 10 mongrel dogs weighing between 8 and 15 kg. Significant (p less than 0.01) accumulation of arterial carbon dioxide tension (PaCO2) (respiratory acidosis) was observed after 5 and 10 minutes of ventilation through the 3.5 and 4.0 bronchoscopes, but no significant increase in PaCO2 was noted with the 5.0 bronchoscope. There was no significant change in arterial oxygen tension under the same conditions. Manual compression of the upper anterior abdominal wall during expiration was applied during bronchoscopy in 6 children. Arterial blood samples were taken before insertion of the bronchoscope and 5 minutes later with and without abdominal compression during expiration. A significant increase (p less than 0.05) in PaCO2 and a decrease in pH were observed after 5 minutes of the bronchoscopic procedure without manual compression of the abdominal wall, while no significant changes in PaCO2 were observed with abdominal compression.

[Clinical studies on acidosis morbidity (author's transl)]

Basing on the pH values of the umbilical artery of a total of 3,421 births in 1977 and in the first half of 1978, the acidosis morbidity associated with the various methods of delivery and dependent upon the weight at birth is determined, and compared with the Apgar score. The results are discussed with reference to literature. It is concluded from this study that electronic monitoring should be intensified, that indication for abdominal Caesarean section should be considered on a relatively liberal scale, and that the quota of underweight children should be reduced further.

[Necessity to control endexpiratory CO2-concentration during laparoscopic sterilisation under general anaesthesia with controlled ventilation (author's transl)]

During laparoscopy and intraabdominal insufflation of CO2 cardio-respiratory accidents following increased PaCO2 are possible. The continuous measurement of endexpiratory CO2-concentration by infrared absorption spectrometry is a simple method for controlling the level of ventilation. Respiratory acidosis under controlled artificial ventilation during laparoscopy can thus be avoided.

[Advantages of blood gas analyses of an improved ventilation bronchoscope (author's transl)]

During bronchoscopy in elder patients the development of respiratory acidosis is a hazard. A new and improved ventilation bronchoscope decreases the risk, which was demonstrated by blood gas analyses. This bronchoscope differs from those normally used in the following ways: 1. An inflatable cuff on the outer tube seals the bronchoscope like a breathing tube against the trachea. 2. This bronchoscope, although in the endobronchial position, improves the ventilation of the contraleateral lung aided by wider side holes lying above the bifurcation. 3. Jet-ventilation can be employed.

[Oxygen therapy in pneumology]

Circumstances under which the use of oxygen-therapy in lung disease can be effective and harmless, depend upon a careful evaluation of its indications: they are suggested by the clinical need of correction of hypoxaemia as well as by the awareness of factors determining respiratory failure and of problems concerning O(2) transport and supply to tissues in health and disease. Blood gases monitoring enables to control the effects of treatment on arterial O2 and CO2 tensions thus giving all the useful data for oxygen administering particularly as far as components of hyperoxygenated mixtures, flow rate, duration, use of very effective low-risk devices (Venturi masks) are concerned. Correction of hypoxaemia involves the reduction of hypertension of the pulmonary circulation and hyperglobulia, improvement of tolerance of exertion, and attention to the metabolic compensation of respiratory acidosis. These results are influenced by the nature of the pathogenetic factors behind broncho-obstructive disease, which may lead to either a primarily "bronchitis" or a primarily "emphysematous" syndrome. An interesting feature relates to prognosis in the case of patients making home use of hyperoxygenated mixtures as part of a rehabilitation program, or to improve their quality of life. The cost and benifits of such treatment should be carefully weighed. Lastly, in the event of protracted treatment, attention must be paid to the possibility of toxicity and the means to be adopted for its prevention.

The management of sickle cell patients undergoing surgery

Between 10 and 15 percent of blacks have sickle cell disease or sickle cell trait. Either is capable of a sickle cell crisis which could occur during a surgical procedure. Because of this, we as otolaryngologists should be aware of how to diagnose sickle cell disease and what specific measures should be followed in order to avoid a sickle cell crisis. This paper deals with specific diagnostic tests available, their interpretation, and our protocol for managment of these patients when they are in the hospital for a surgical procedure.

[Effect of 1,4-benzodiazepine derivatives on the toxic action of oxygen under increased pressure]

The 1,4-benzodiazepine derivatives (diazepam, nitrazepm, lorazepam, clonazepam and two newly synthetized compounds of this series) increase the resistance of albino rats and rabbits to the toxic effect of oxygen under high pressure (7 and 5.5 atm respectively). The compounds under study are apt to avert over a long period the development of metabolic acidosis which appears following the action of high-pressure oxygen on the body.

The effect of intravenous ritodrine on the acid-base status of the fetus during the second stage of labour

A progressive fetal respiratory acidosis occurs in the second stage of labour. A double-blind controlled trial showed that the intravenous infusion of Ritodrine abolished this.

[Blood gas studies on the efficiency of the ventilator "Pulmomat" (author's transl)]

Efficiency of ventilation of Pulmomat has been examined in 48 patients under general anaesthesia and relaxation during normoventilation and hyperventilation of 15 and 30% degree. For criteria the acid-base status of arterial blood has been used. In normoventilation acid-base status remained unchanged within the normal range providing a regular control respectively correction of ventilationvolumes. There was no significant difference between results of 15 and 30% hyperventilation. In both situations arterial pCO-2 was reduced 15-20%. There was a tendency to acidosis in all kinds of ventilation presumably as a consequence of surgical effects. For security using the Pulmomat as respirator, a hyperventilation of 15% degree is recommanded in clinical use.

Postoperative pulmonary atelectasis and collapse, and its prophylaxis with intravenous bicarbonate

Of 181 patients undergoing major abdominal surgery 116 developed chest complications associated with a metabolic acidosis, low Pco2, depressed tidal volume, increased respiratory rate, but no increase in minute volume. In a matched group of 116 patients given intravenous bicarbonate postoperatively only 15 developed chest complications. This suggests that respiratory physiological dead space decreases in patients with pulmonary collapse and atelectasis following surgery. Acidotic respiration proved inefficient in the postoperative period, and intravenous bicarbonate had a very pronounced effect on the tidal and minute volumes of acidotic patients with pulmonary collapse and atelectasis.