Retrospective evaluation of cardiopulmonary and acid-base variables during long-term balanced anesthesia for experimental surgery in dogs

Cardiopulmonary and acid-base variables recorded during long-term balanced anesthesia lasting between 12.5 and 16.9 h were evaluated retrospectively in 15 healthy foxhounds that underwent experimental bulla osteotomy with implantation of hearing aids. After premedication with propionylpromazine (0.11 +/- 0.02 mg/kg of body weight) and L-methadone (0.71 +/- 0.06 mg/kg) intravenously (i.v.) and induction with pentobarbital sodium (6.02 +/- 0.83 mg/kg i.v.), anesthesia was maintained with halothane (end-tidal concentration; ETHAL: 0.4 to 1.5%) in nitrous oxide (2 L/min) and oxygen (1 L/min). Because of positional changes from sternal to right lateral recumbency after presurgical brain stem electric response audiometry and differences in duration of surgery, data obtained between 4 (baseline) and 14 h after induction of anesthesia were analyzed. Arterial (PaO2) and alveolar (PAO2) O2 tensions, arterial-to-alveolar O2 tension ratio (PaO2/PAO2), and arterial O2 content (CaO2) remained relatively stable throughout anesthesia. Arterial carbon dioxide tension (PaCO2) was significantly increased above baseline (39, 33 to 46 mm Hg [median, range]) between 7 (39.8, 36.5 to 48.9 mm Hg) and 9 (42, 37.5 to 49.5 mm Hg) h after induction. Because changes in PaCO2 were accompanied by significant increases in body temperature from baseline (36.3, 34.6 to 37.4 degrees C) between 8 (37.1, 35 to 38 degrees C) and 11 (37.6, 35.3 to 38.1 degrees C) h after anesthesia induction as well as by slight increases in arterial blood pressure, the PaCO2 increase may have been caused by increase in metabolic CO2 production and enhanced drainage of CO2 from the tissues into systemic circulation. Furthermore, mild metabolic acidosis (pHa: 7.31, 7.26 to 7.38; HCO3-: 18.9, 16.7 to 21.8 mEq/L; base deficit [BD]: -6.3, -8.5 to -3.4 mEq/L) already existed at 4 h after induction and was related in part to tissue hypoperfusion. Small increases in pHa during the course of anesthesia were accompanied by significant increases in HCO3- concentration and significant decreases in BD between 5 and 10 h after induction. Minor circumscribed swelling of the dependent triceps or masseter muscle was noticed on the first postoperative day in two dogs, and marked tissue swelling with hematoma formation at the medial side of one hind limb was noticed in a third dog. All dogs recovered completely and were submitted to follow-up studies. The anesthetic protocol and extent of monitoring used were adequate to provide safe long-term anesthesia for an experimental surgical procedure with a 100% survival rate and uneventful recovery in most of the dogs.     

Blood gas changes during laparoscopic cholecystectomy--comparative study of N2O pneumoperitoneum and CO2 pneumoperitoneum

During laparoscopic cholecystectomy by alternative insufflation of nitrous oxide and carbon dioxide, the changes of blood gas tensions were measured and analyzed in 12 patients. During N2O insufflation, PaO2 decreased by about 25 mmHg and PaCO2 was unaltered compared with the values before pneumoperitoneum. While during CO2 insufflation, PaO2 decreased by about 13 mmHg and PaCO2 increased by about 6 mmHg. We considered that decrease in PaO2 during N2O insufflation was associated with not only uneven ventilation/blood flow ratios but also with the reduction in the alveolar O2 tension caused by the diffusion of N2O absorbed from the peritoneum. PaCO2 increases during CO2 insufflation because CO2 is absorbed from the peritoneum, and is not excreted entirely through the lungs.     

支气管阻塞器用于胸腔镜下肺癌术患者单肺通气的效果

Objective: The aim of this study was to observe the effect of endobronchial blocker tube in the pulmonary carcinoma with video-assisted thoracic surgery. Methods: Forty patients of pulmonary carcinoma with video-assisted thoracic surgery were randomly assigned into two groups with twenty cases each : endobronchial blocker tube group (group 1) and double-lumen endobronchial tube group (group 2). After anesthesia was induced, in group 1, single lumen tube was intubated at first, and then endobronchial blocker tube intubated to left or right primary bronchus under the guidance of fiber-optic bronchoscope according to operational necessary, injected 2–4 mL air to blocker balloon and blocker one lateral primary bronchus for one-lung ventilation necessarily; while in group 2, the position of double-lumen endobronchial tube was confirmed with fiber-optic bronchoscope after intubation. Blood samples were collected before anesthesia induction, double lumen ventilation, at the one-lung ventilation of 5 min, 30 min, 60 min, 120 min and 180 min, SBP, DBP, HR, SpO2, partial pressure of end tidal carbon dioxide (PetCO2), pH, PaO2, PaCO2,PaO2/FiO2 were recorded. Results: Forty cases' intubations were all successful. There were no differences in SBP, DBP, HR, SpO2, PetCO2, pH, PaCO2 between two groups in different points (P > 0.05). Paw in group 1 was lower than group 2, PaO2 and PaO2/FiO2 in group 1 was higher than group 2 in the one lung ventilation of 5 min, 30 min, 60 min, 120 min and 180 min. Conclusion: The endobronchial blocker tube can meet the request of video-assisted thoracic surgery, with the special advantages of simple insertion, lower airway and better oxygenation. Endobronchial blocker tube offer a new way for one-lung ventilation in the pulmonary carcinoma with video-assisted thoracic surgery.     

Ultrasonographic assessment of bladder neck mobility in continent bitches and bitches with urinary incontinence attributable to urethral sphincter mechanism incompetence

OBJECTIVE: To determine bladder neck positional changes between standing and recumbent positions in bitches and whether change is related to continence status or general anesthesia, or both, and to evaluate reproducibility of measurements. ANIMALS: 45 continent animals and 46 incontinent bitches with urethral sphincter mechanism incompetence (SMI). PROCEDURE: Distance between the bladder neck and perineal skin was measured ultrasonographically via the perineum while each dog was conscious in standing and right lateral recumbency and in right lateral recumbency under general anesthesia. Measurements of the bladder neck position obtained in right lateral recumbency under anesthesia were compared with radiographic measurements of the same parameter. Reproducibility of the ultrasonographic measurements of the distance between bladder neck and perineum was assessed on 3 occasions for each position in 50 dogs. RESULTS: In all dogs, differences in bladder neck position between standing and recumbent conscious-associated positions were not significant. However, caudal bladder neck movement between standing conscious- and recumbent anesthesia-associated positions and between recumbent conscious- and anesthesia-associated positions was significant for all dogs. Incontinent bitches had greater degree of caudal bladder movement during anesthesia. Mean difference in bladder neck positions between recumbent conscious- and recumbent anesthesia-associated positions was 0.24 cm in continent, compared with 0.73 cm in incontinent, bitches. Radiographic measurements were significantly greater than ultrasonographic measurements. Differences between repeated measurements for standing position were not significant, but those for recumbent conscious- and recumbent anesthesia-associated positions were significant. CONCLUSIONS: Additional vesicourethral support mechanisms in continent dogs, are deficient in bitches with SMI, allowing the bladder neck to move further caudad.     

Continuous low-flow tracheal gas insufflation during partial liquid ventilation in rabbits

BACKGROUND: Both partial liquid ventilation (PLV) and tracheal gas insufflation are novel techniques for mechanical ventilation. In this study we examined whether PLV superimposed by continuous low-flow tracheal gas insufflation (TGI) offers any advantage to the blood gases and lung mechanics in normal-lung rabbits compared to the use of PLV only. METHODS: Eighteen anesthetized, paralyzed and mechanically ventilated rabbits were used. After obtaining a baseline PaCO2 value between 29 and 39 mmHg (3.9 and 5.2 kPa), the animals were assigned to three equal groups according to the ventilation they received--A group: PLV superimposed by TGI; B group: PLV only; and C group: continuous mandatory ventilation (CMV) superimposed by TGI. Serial arterial blood gases, pH and lung mechanics were measured. RESULTS: The animals in each group were hemodynamically stable. In the case of the A group, PaO2 continuously increased, and PaCO2 stabilized around 40.8 +/- 5.5 mmHg (5.4 +/- 0.7 kPa, mean +/- SD, NS). In the B group, the tendency for PaO2 to increase was not as definite; PaCO2 continuously increased from 35.2 +/- 2.3 mmHg (4.7 +/- 0.3 kPa) to 56.3 +/- 12.7 mmHg (7.5 +/- 1.7 kPa, P < 0.05) at the end of the experiment. In the C group, PaO2 and PaCO2 were stable during the observation period. The superimposition of TGI on PLV did not decrease the airway pressures compared to PLV alone. CONCLUSION: In summary, continuous low-flow TGI superimposed on PLV can decrease and stabilize the PaCO2 elevation caused by the initiation of PLV.     

What is a migraine, anyway, and when is it gone?

PURPOSE: To assess the effect of pneumoperitoneum on P(a-ET)CO2 gradient in children. METHODS: Sixty one ASA I and II children (10.7 +/- 3.0 yr, 38.4 +/- 14.2 kg, mean +/- SD), scheduled for visceral or urological laparoscopic procedures, were studied. They were anaesthetized, intubated, paralysed and their lungs ventilated with constant ventilator settings to obtain PETCO2 values between 4.3 and 4.8 kPa. Intra-abdominal pressure was maintained between 8 and 14 mmHg. The following measurements were performed at steady state, before the pneumoperitoneum (T1) and 15 min later (T2): heart rate, systolic and diastolic arterial pressure; peak airway and intra-abdominal pressure; PaCO2 corrected for the patient's temperature; PETCO2 drawn between the micropore filter and the ventilator tubes, corrected for BTPS conditions; P(a-ET)CO2. Values between -1.0 and +1.0 mmHg were considered nil; patient position (horizontal or head-down tilt): all patients were horizontal at T1. RESULTS: Arterial pressure, heart rate and peak airway pressure increased at T2: PaCO2 and PETCO2 increased by 14%. The incidence of negative gradients increased from 54 to 67% although mean P(a-ET)CO2 remained clinically unchanged. No difference was found in P(a-ET)CO2 gradient, whatever the position and intra-abdominal pressure. The 95% confidence intervals for P(a-ET)CO2 were [-5.6; +3.2] at T1 and [-8.8; +4.8] at T2. CONCLUSION: PETCO2 often overestimates PaCO2 during laparoscopy in children, by up to 8.8 mmHg. Arterial blood gas analysis should be performed during long procedures to avoid hyperventilation.     

Intraabdominal carbon dioxide insufflation in the pregnant ewe. Uterine blood flow, intraamniotic pressure, and cardiopulmonary effects

BACKGROUND: Laparoscopic surgical procedures are being performed in pregnant women with increasing frequency. Maternal-fetal physiologic changes occurring during intraabdominal carbon dioxide insufflation are poorly understood, and maternal-fetal safety is of concern during carbon dioxide pneumoperitoneum. A previous pilot study using end-tidal carbon dioxide-guided ventilation resulted in maternal and fetal acidosis and tachycardia during carbon dioxide pneumoperitoneum. Using serial arterial PCO2 to guide ventilation, this study was designed to evaluate maternal-fetal cardiopulmonary status, uterine blood flow, and the intraamniotic pressure effects of intraabdominal carbon dioxide insufflation in singleton pregnant ewes between 120 and 135 days of gestation. METHODS: In a prospective randomized cross-over study, nine ewes were to receive either abdominal insufflation with carbon dioxide to an intraabdominal pressure of 15 mmHg (n = 9; insufflation group) or receive no insufflation (n = 9; control group). Anesthesia was induced with thiopental and maintained with end-tidal halothane (1 to 1.5 minimum alveolar concentration/100% oxygen). Mechanical ventilation was guided by serial maternal arterial blood gas analysis to maintain PaCO2 between 35 and 40 mmHg. Data from insufflated animals were collected during insufflation (60 min) and after desufflation (30 min). Control group data were collected and matched to similar time intervals for 90 min. Ewes were allowed to recover, and after a rest period (48 h) they were entered in the cross-over study. RESULTS: During insufflation there was a significant increase (P < 0.05) in maternal PaCO2 to end-tidal carbon dioxide gradient and minute ventilation, with concomitant decreases in maternal end-tidal carbon dioxide and PaO2. Intraamniotic pressure increased significantly during insufflation. No significant changes were observed in maternal hemodynamic variables, fetal variables, or in uterine blood flow during the study. There were no fetal deaths or preterm labor in any of the animals during the experiment. CONCLUSIONS: During the 1-h insufflation, a marked increase in PaCO2-to-end-tidal carbon dioxide gradient was observed, suggesting that capnography may be an inadequate guide to ventilation during carbon dioxide pneumoperitoneum in the pregnant patient. No other significant circulatory changes were observed.     

Possibilities for psychotherapy treatment of Alzheimer disease patients in the early stage of the disease]

This presentation examines the relation of arterial CO2 tension to the severity of acidemia in three large groups of cases of diabetic ketoacidosis, totalling 405 episodes. In particular, it evaluates the previously reported anecdotal observation that PaCO2 (in torr) in such patients is usually numerically close to the two-digit number to the right of the pH decimal point, down to a pH of 7.10-7.15. The relations between measured arterial CO2 tension levels and calculated plasma bicarbonate concentration in the three groups were very similar to those previously reported by others and us, the regression equations approximating PaCO2 = 1.5 x [HCO3-] + 8. Further, in the 262 episodes with blood pH 7.10-7.37, down to a pH of 7.10-7.15, the average PaCO2 in torr often did approximate the two-digit number to the right of the decimal point in the pH value. This relation provides a quick and easily remembered alternative guide for predicting the approximate expected PaCO2 in patients with metabolic acidosis. The basis for this apparently fortuitous relation between PaCO2 and blood pH may be the closely similar correlation between PaCO2 and 1/cH+ (i.e., 10PH), which in turn derives from the physiologically significant relation of alveolar ventilation to blood pH, and the inverse relation between PaCO2 and alveolar ventilation.     

Opinion of the people in charge of the medical graduation disciplines at the S?o Paulo University Medical School on the ''curriculum evaluation program''

Several studies were focused on the consequences of reduced PaO2 (hypoxemia) on the Breuer-Hering inspiration-inhibiting vagal reflex. However, these data are often contradictory and do not allow us to decide whether hypoxemia interacts with the central integration of pulmonary vagal afferents and/or exerts peripheral influence on pulmonary stretch receptor (PSR) activity. The present study was performed in anesthetized rabbits breathing different gas mixtures containing O2, N2 and CO2. Intravenous injection of bicarbonates and CO2 addition in the inspired mixture maintained pHa and PaCO2 within their physiological ranges. The Breuer-Hering reflex, assessed from the changes in diaphragmatic EMG activity, was elicited either by inflating the lungs at different volumes above the functional residual capacity (PSR activation) or by direct electrical stimulation of vagal afferents (central stimulation). Hypoxemia never significantly modified the strength of the reflex or its threshold. Thus, acute hypoxemia present at high altitude does not seem to modify the key role played by PSR afferents in the ventilatory control.     

Anesthetic and cardiorespiratory effects of tiletamine-zolazepam-medetomidine in cheetahs

OBJECTIVE: To evaluate anesthetic and cardiorespiratory effects of an intramuscular injection of a tiletamine-zolazepam-medetomidine combination in cheetahs. DESIGN: Prospective study. ANIMALS: 17 adult captive cheetahs. PROCEDURE: The anesthetic combination was administered intramuscularly via a dart. Induction quality, duration of lateral recumbency, duration of recovery, and quality of anesthetic reversal with atipamezole were assessed. Cardiorespiratory variables (arterial blood gas partial pressures, arterial blood pressure, heart and respiratory rates, end-tidal CO2, oxygen saturation, and rectal temperature) were measured during anesthesia. RESULTS: Sedation and lateral recumbency developed within 1.9 +/- 1.0 (mean +/- SD) and 4.3 +/- 2.0 minutes of drug administration, respectively. Clinically acceptable cardiorespiratory and blood gas values were recorded for at least 87 minutes after drug administration in all but 1 cheetah. Hypoxemia and arrhythmias developed in 1 cheetah breathing room air but resolved after treatment with oxygen. Hypertension developed in all cheetahs. Significant differences in heart and respiratory rates, mean arterial blood pressure, arterial pH, partial pressure of oxygen, and hemoglobin saturation were found between cheetahs that did and did not receive oxygen supplementation. After administration of atipamezole, sternal recumbency and mobility returned within 6.9 +/- 5.8 and 47.5 +/- 102.2 minutes, respectively. Postreversal sedation, which lasted approximately 4 hours, developed in 4 cheetahs. CLINICAL IMPLICATIONS: Tiletamine-zolazepam-medetomidine delivered via a dart provided an alternative method for induction and maintenance of anesthesia in cheetahs. Atipamezole at the dose used was effective for reversal of this combination in the initial phase of anesthesia.     

Partial cardiopulmonary bypass in rats for evaluating ischemia-reperfusion injury

The authors developed a miniaturized partial cardiopulmonary bypass model in rats by using membrane oxygenators. Sprague-Dawley rats underwent general anesthesia and tracheostomy for ventilation. Partial cardiopulmonary bypass was carried out through the jugular cannula (18 gauge) for venous blood drainage and through the femoral arterial cannula (24 gauge) at a flow of 50 ml/kg/min. Membrane oxygenators used in this study maintained arterial oxygen tensions (PaO2) at 300-500 mmHg and carbon dioxide tensions (PaCO2) at 25-35 mmHg, with a gas mixture of 95% O2 + 5% CO2 (n = 7) for at least 2 hr of bypass circulation. To test the feasibility of this system for investigation of ischemia-reperfusion injury, hypoxic challenges with gas mixtures of different oxygen concentrations were examined. After equilibration of the bypass circulation for 1 hr, the following gases were tested for 15 min: Group I, 95% air + 5% CO2 (FiO2 = 0.21, n = 5); Group II, 10% O2 + 5% CO2 + 85% N2 (FiO2 = 0.1, n = 5); and Group III, 95% N2 + 5% CO2 (FiO2 = 0, n = 5). Equilibrated PaO2 values after challenge with these gases for 15 min were as follows: Group I: 89.6 +/- 3.7, Group II: 53.8 +/- 1.4, Group III: 25.6 +/- 2.0 mmHg (p < 0.01 between Groups I and II, I and III, II and III; p < 0.01 vs. prehypoxic PaO2 values in all groups). PaO2 values returned to the previous level within 15 min after return to the standard gas mixture (95% O2 + 5% CO2) supply. This system provided stable cardiopulmonary bypass in rats for at least 2 hr and may be useful for investigation of ischemia-reperfusion injury.     

Use of DNA end joining activity of a Xenopus laevis egg extract for construction of deletions and expression vectors for HIV-1 Tat and Rev proteins

Blood gases were analyzed in dogs with pulmonary heartworm (HW) disease. The arterial oxygen tension (PaO2) in dogs with mild signs of dirofilariasis (mildly affected group, n = 48, 85.7 +/- 8.2 mmHg) and in dogs with signs of right heart failure (severely affected group, n = 13, 76.4 +/- 11.6 mmHg) was lower (p < 0.01) than in dogs without HW infection (HW-free group, n = 19, 91.5 +/- 7.3 mmHg). Only 2 dogs in the severely affected group had a PaO2 less than 60 mmHg. The arterial carbon dioxide tension (PaCO2, p < 0.01) and mixed venous O2 (p < 0.01) and CO2 (p < 0.01) tensions were lower, and alveolar-arterial oxygen difference (AaDO2, p < 0.01) was greater in the severely affected group than in the HW-free and mildly affected groups. Arterial pH and bicarbonate (HCO3-) concentrations were lower (p < 0.01) in both affected groups than in the HW-free groups. The anion gap level was not different among the 3 groups. Serum lactic acid level in the severely affected group was higher (p < 0.01) than in the HW-free and mildly affected groups. However, a slightly higher serum lactic acid concentration was found only in 2 dogs of the severely affected group (3.84 mmol/l and 3.82 mmol/l). The PaO2 (r = -0.62) and AaDO2 (r = 0.66) correlated significantly (p < 0.01) with mean pulmonary arterial pressure. One week after HW removal, blood gases, pH and HCO3- concentration remained unchanged in the mildly affected group. In the severely affected group, blood gas values were the same, but pH and HCO3- concentration improved slightly.     

Influence of age on cardiac pump function during laparoscopic cholecystectomy--measurements by ear densitography

Using ear densitography, consisting of photoelectric plethysomography and Holter electrocardiography, we measured systolic time intervals (STI) in 21 patients, ASA class 1 and 2, undergoing laparoscopic cholecystectomy using CO2 insufflation under general anesthesia (neuroleptanesthesia with isoflurane in air, FIO2 0.5). The patients were divided into two groups: Y-group (10 patients under 59 years of age) and O-group (11 patients over 60 years of age). We investigated the influence of age on cardiac pump function during pneumoperitoneum non-invasively. Y-group showed improvement of cardiac pump function (reduction of PEP/LVET) from 30 minutes after the beginning of insufflation and quick recovery of cardiac function immediately after deflation. O-group showed a tendency of increasing PaCO2 and arterial diastolic pressure, and delayed recovery of cardiac function (elongation of PEP at 60 minutes, and increase of PEP/LVET at 60 and 90 minutes, respectively, after insufflation). Hypertension and tachycardia were apparent immediately after pneumoperitoneum in the O-group. We conclude that special care and monitoring are mandatory for the aged patients with impaired cardiac or respiratory function during laparoscopic surgery.     

Value of orally administered retard morphine for therapy of severe pulmonary emphysema of the pink-puffer type. A pilot study

BACKGROUND AND OBJECTIVE: In severe "pink puffer" emphysema the patients' physical capacity is limited by dyspnoea despite maximal application of established treatment. This pilot study investigated the effect of retarded morphine, taken orally for 10 days, on ventilation, dyspnoea, walking capacity and wakefulness. PATIENTS AND METHODS: Twenty clinically stable patients (11 men, 9 women, mean age 68.5 [50-81] years) with "pink puffer" emphysema were studied over a period of 10 days in a prospective, non-controlled trial of cross-over design. Criteria for inclusion in the study were: 1-second forced expiratory volume (FEV1) < 1 I, vital capacity < 50% and normocapnia. In addition to their existing therapy patients received either no further therapy or retarded morphine. Morphine dosage was increased to maximally 3 x 30 mg daily, depending on effectiveness and side effects, dyspnoea at rest and immediately after a 6-min walk (assessed with Borg's visual analog scale), maximal walking capacity were determined, as well as blood gases, respiratory minute volume and the respiratory drive (airway occlusion pressure [P0.1]), responsiveness of the respiratory pathways to CO2 and wakefulness (concentration, fatigue, interest in surroundings). RESULTS: Twelve patients completed the study (group A). In the remaining patients (group B) the test had to be stopped prematurely because of undesirable side effects or an exacerbation of the underlying infection. In group A, morphine (mean dosage: 49.2 +/- 28.4 mg/d) caused a reduction of PaO2, dyspnoea on activity, the resting minute respiratory volume, respiratory drive and CO2 response, and an increase in PaCO2, HCO3- and the 6-min walking distance. Morphine did not produce a change in subjectively evaluated vigilance and the blood pH. CONCLUSION: After strict patient selection oral morphine produced a reduction of exercise dyspnoea and an increase in walking capacity in half of the patients with severe pulmonary emphysema. There also occurred a slight rise in PaCO2 without any relevant respiratory acidosis or significant decrease in wakefulness.     

Efficacy of dead-space washout in mechanically ventilated premature newborns

The prosthetic dead space makes a significant contribution to the total dead space in low-birth-weight premature newborns receiving artificial ventilation in response to respiratory distress. Use of an endotracheal tube with capillaries molded into the tube wall enables washout of the dead space without insertion of a tracheal catheter. In 10 premature newborns (mean gestational age, 27.5 +/- 2.2 wk; mean weight, 890 +/- 260 g) receiving continuous positive-pressure ventilation (Paw = 12.7 +/- 1.8 cm H2O; FIO2 = 39 +/- 17%), tracheal gas insufflation (TGI) for CO2 washout was conducted using this technique. The flow of tracheal insufflation (0.5 L/min) was derived from the inspiratory line of the ventilator circuit and blown into the trachea. Intratracheal pressures showed little or no TGI-related modification ( < 1 cm H2O). A control system enabled TGI discontinuation in the event of a pressure rise. At constant ventilation pressure, PaCO2 decreased by 12.1 +/- 5.9 mm Hg (delta PaCO2 = -26 +/- 12%) under TGI, whereas PaO2 remained unchanged. While maintaining PaCO2 constant, peak inspiratory pressure (PIP) was decreased by 5.4 +/- 1.7 cm H2O (delta PIP = -22.0 +/- 8.3%). TGI showed immediate efficacy (PCO2 reduction of at least 5 mm Hg) in nine of the 10 newborns who then received chronic TGI (14 to 138 h). TGI appears to be an effective method, suitable for long-term clinical application, enabling a reduction in the aggressive nature of conventional ventilation.     

8-year experience with force vector rhinoplasty by J.B. Tebbetts: comparative results

BACKGROUND: Previous studies have suggested that diagnostic laparoscopy may be contraindicated in multiple trauma patients with closed head injuries because of the detrimental effects of carbon dioxide (CO2) pneumoperitoneum on intracranial pressure (ICP). In this study we compared the effects of two alternative inflation gases, helium (He) and nitrous oxide (N2O), against the standard agent used in most hospitals, CO2. ICP was monitored in experimental animals both with and without a space occupying intracranial lesion designed to simulate a closed head injury. METHODS: Twenty-four domestic pigs (mean, 30 kg) were divided into four groups (6 CO2, 6 He, 6 N2O, and 6 control animals without insufflation). All animals were monitored for ICP, intraabdominal pressure, mean arterial pressure, end-tidal CO2 (ETCO2), and arterial blood gases. These parameters were measured for 30 minutes prior to introducing a pneumoperitoneum and then for 80 minutes thereafter. The measurements were repeated after artificially elevating the ICP with a balloon placed in the epidural space. RESULTS: The mean ICP increased significantly in all groups during peritoneal insufflation compared with the control group (P < 0.005). The CO2-insufflated animals also showed a significant increase in PaCO2 (P < 0.05) and ETCO2 (P < 0.05), as well as a decrease in pH (P < 0.05). After inflating the epidural balloon the ICP remained significantly higher in animals inflated with CO2 as compared with the He and N2O groups (P < 0.05). CONCLUSIONS: Peritoneal insufflation with He and N2O resulted in a significantly less increase in ICP as compared with CO2. That difference was most likely due to a metabolically mediated increase in cerebral perfusion (PaCO2) in the CO2 group. Further studies need to be conducted to determine the safety and efficacy of using He and N2O as inflation agents prior to attempting diagnostic or therapeutic laparoscopy in patients with potential closed head injuries.     

Hemodynamic changes during laparoscopic cholecystectomy

Hemodynamics during laparoscopic cholecystectomy under general anesthesia (isoflurane in N2O/O2 (50%)) were investigated in 15 nonobese ASA Class I patients by using invasive hemodynamic monitoring including a flow-directed pulmonary artery catheter. During surgery, intraabdominal pressure was maintained automatically at 14 mm Hg by a CO2 insufflator, and minute ventilation was controlled and adjusted to avoid hypercapnia. Hemodynamics were measured before anesthesia, after the induction of anesthesia, after tilting into 10 degrees head-up position, 5 min, 15 min, and 30 min after peritoneal insufflation, and 30 min after exsufflation. Induction of anesthesia decreased significantly mean arterial pressure and cardiac index (CI). Tilting the patient to the head-up position reduced cardiac preload and caused further reduction of CI. Peritoneal insufflation resulted in a significant increase (+/- 35%) of mean arterial pressure, a significant reduction (+/- 20%) of CI, and a significant increase of systemic (+/- 65%) and pulmonary (+/- 90%) vascular resistances. The combined effect of anesthesia, head-up tilt, and peritoneal insufflation produced a 50% decrease in CI. Administration of increasing concentrations of isoflurane, via its vasodilatory activity, may have partially blunted these hemodynamic changes. These results demonstrate that laparoscopy for cholecystectomy in head-up position results in significant hemodynamic changes in healthy patients, particularly at the induction of pneumoperitoneum.     

Laparoscopy in high-risk cardiac patients

Fifteen patients with severe cardiac disease (American Society of Anesthesiologists III or IV) underwent laparoscopy using radial artery and pulmonary artery catheters to determine intraoperative hemodynamic changes. Cardiac output (CO), mean arterial blood pressure (MAP), central venous pressure, heart rate, systemic vascular resistance (SVR) and mixed venous oxygen saturation (SVO2) were recorded before anesthetic induction, after induction, but before peritoneal insufflation, after insufflation and after release of pneumoperitoneum. Peritoneal insufflation led to significant elevations in MAP and SVR and reduction in CO. For seven patients, a decrease in SVO2 after peritoneal insufflation was predictive of significant worsening of hemodynamic parameters, suggesting inadequate cardiac reserve. In all patients, hemodynamic parameters returned toward baseline once pneumoperitoneum was released. There were no perioperative cardiac complications. While it is evident that laparoscopy presents serious hemodynamic stress, it can be performed safely in high-risk patients, using aggressive intraoperative monitoring.