Hemodynamics during laparoscopic surgery in pregnancy.

IMPLICATIONS: During laparoscopic cholecystectomy in four pregnant women, we observed hemodynamic changes similar to those in nonpregnant patients (i.e., decreases in cardiac index together with increases in mean arterial blood pressure and systemic vascular resistance).

The effect of magnesium on coagulation in parturients with preeclampsia.

UNLABELLED: Preeclampsia is associated with complex coagulation abnormalities that include altered platelet function and consumption and activation of the fibrinolytic system. Magnesium sulfate, which is used as a therapeutic modality for the prevention of seizures in preeclamptic parturients, has anticoagulant and antiplatelet effects. We sought to determine the effects of magnesium on various components of the coagulation system in patients with preeclampsia. We assessed the coagulation status of 18 parturients with preeclampsia being treated with magnesium. The assessment was performed with the thromboelastograph test, which provides an overall assessment of blood coagulation via the coagulation index. Thromboelastography was performed before beginning magnesium therapy and 30 min and 2 h after a 6-g bolus of IV magnesium. The R value (time to first clot formation) was found to be significantly slower (P < 0.05) at 30 min after the magnesium bolus. This result suggests increased coagulant factor activity resulting from the magnesium bolus. However, there was no effect of magnesium on the overall coagulation, as evidenced by the lack of change in the coagulation index either at 30 min or at 2 h after the completion of the initial magnesium bolus. Therefore, this therapy should have no effect on the use of neuraxial techniques. IMPLICATIONS: On the basis of the thromboelastography assessment, we found that the current practice of administering magnesium did not influence overall coagulation in preeclamptic women. Therefore, magnesium administration should not affect the use of neuraxial techniques.

Laparoscopic surgery during pregnancy.

Important factors in laparoscopic surgery during pregnancy are listed here: There is a risk of aspiration because of a hormonally induced decrease in lower esophageal sphincter tone and mechanical effects of a gravid uterus. Supine hypotensive syndrome because of aortocaval compression can be a major problem. Pneumoperitoneum during pregnancy results in more pronounced restrictive lung physiology. Avoid hypoxemia, hypotension, acidosis, hypoventilation, and hyperventilation. No anesthetic drugs have been proven to be teratogenic in humans. Surgery during pregnancy is associated with the delivery of low birth-weight, growth-restricted babies. Standard noninvasive monitoring could be sufficient for healthy parturients undergoing laparoscopic surgery. Fetal heart rate and uterine activity should be monitored pre- and postoperatively. Laparoscopic surgery during pregnancy is safe, has multiple advantages over open techniques, can be performed during all gestational ages, and does not require invasive or continuous fetal and uterine monitoring for routine cases; however, the anesthesiologist must be aware of the physiologic changes associated with pregnancy and the effects of positioning, and the consequences of CO2 pneumoperitoneum on the parturient and the fetus. Although no special monitoring is required in healthy parturients, each case must be assessed carefully, and invasive monitoring could be required in those patients with significant cardiovascular or pulmonary disease. Fetal heart rate should be assessed preoperatively and postoperatively. Surveillance with an external tocodynamometer should be instituted immediately preoperatively and postoperatively and tocolytic agents instituted if documented or perceived uterine activity is detected.

Defining segments and phases of a time capnogram.

UNLABELLED: The division of a time capnogram into inspiratory and expiratory segments is arbitrary and results in the inability of a time capnogram to detect rebreathing instantaneously. Demarcation of a time capnogram into inspiratory and expiratory components using gas flow signals will not only facilitate prompt detection of rebreathing, but will also allow application of standardized and physiologically appropriate nomenclature for better understanding and interpretation of time capnograms. A Novametrix((R)) CO(2)-SMO plus respiratory profile monitor (Novametrix Medical Systems, Wallingford, CT) was used to obtain a simultaneous display of CO(2) and respiratory flow waveforms on a computer screen during spontaneous and controlled ventilation using a circle system with the inspiratory valve competent (no rebreathing) and with the valve displaced (rebreathing). Because the response time of the CO(2) analyzer was similar to the response time of the flow sensor, a comparison was made between the two waveforms to determine the inspiratory segment (Phase 0) and the expiratory segment of the time capnogram and its subdivisions (Phases I, II, and III). The end of expiration almost coincides with the downslope of the CO(2) waveform in the capnograms when there is no rebreathing. However, in the presence of rebreathing, the alveolar plateau is prolonged and includes a part of inspiration (Phase 0), in addition to the expiratory alveolar plateau (Phase III). IMPLICATIONS: Presently, the division of a time capnogram into inspiratory and expiratory segments is arbitrary. Demarcation of a time capnogram into various components using the gas flow signals facilitates prompt detection of the cause of abnormal capnograms that can widen the scope of future clinical applications of time capnography.

Arterial to end-tidal carbon dioxide pressure difference during laparoscopic surgery in pregnancy.

BACKGROUND: There is controversy about whether capnography is adequate to monitor pulmonary ventilation to reduce the risk of significant respiratory acidosis in pregnant patients undergoing laparoscopic surgery. In this prospective study, changes in arterial to end-tidal carbon dioxide pressure difference (PaCO2--PetCO2), induced by carbon dioxide pneumoperitoneum, were determined in pregnant patients undergoing laparoscopic cholecystectomy. METHODS: Eight pregnant women underwent general anesthesia at 17-30 weeks of gestation. Carbon dioxide pnueumoperitoneum was initiated after obtaining arterial blood for gas analysis. Pulmonary ventilation was adjusted to maintain PetCO2 around 32 mmHg during the procedure. Arterial blood gas analysis was performed during insufflation, after the termination of insufflation, after extubation, and in the postoperative period. RESULTS: The mean +/- SD for PaCO2--PetCO2 was 2.4 +/- 1.5 before carbon dioxide pneumoperitoneum, 2.6 +/- 1.2 during, and 1.9 +/- 1.4 mmHg after termination of pneumoperitoneum. PaCO2 and pH during pneumoperitoneum were 35 +/- 1.7 mmHg and 7.41 +/- 0.02, respectively. There were no significant differences in either mean PaCO2--PetCO2 or PaCO2 and pH during various phases of laparoscopy. CONCLUSIONS: Capnography is adequate to guide ventilation during laparoscopic surgery in pregnant patients. Respiratory acidosis did not occur when PetCO2 was maintained at 32 mmHg during carbon dioxide pneumoperitoneum.

Airway changes during Cesarean hysterectomy.

PURPOSE: To document whether hemorrhage and fluid administration during peripartum hysterectomy results in changes in the airway that may predispose to subsequent difficult intubation, in the event that intraoperative general anesthesia is required during regional anesthesia. CLINICAL FEATURES: A 32-yr-old underwent peripartum hysterectomy for placenta accreta. Blood loss of 5.5 L occurred during surgery requiring 6 L crystalloid, 1 L hetastarch, five units packed RBCs and two units fresh frozen plasma. Airway changes were followed using Samsoon's modification of Mallampati airway classification. In addition, airway photographs were obtained using a Polaroid camera. The airway of the patient changed from class 2 preoperatively to class 4 in the immediate postoperative period. The airway gradually returned to normal over the ensuing 48 hr, during which a negative fluid balance of 4 L occurred due to substantial postoperative diuresis. CONCLUSION: Peripartum airway changes were detected during Cesarean hysterectomy and fluid resuscitation that gradually returned to normal within 48 hr after surgery.

Pregnancy, labour and delivery in a Jehovah's Witness with esophageal varices and thrombocytopenia.

PURPOSE: An increasing number of women with cirrhosis are conceiving and carrying their pregnancies to term. However, the maternal mortality rate remains high (10-61%). This case report describes the management of a parturient with esophageal varices and thrombocytopenia. She was also a Jehovah's Witness. CLINICAL FEATURES: A 25-yr-old Jehovah's Witness parturient with portal hypertension and esophageal varices secondary to cryptogenic cirrhosis was referred to our obstetrical unit at eight weeks gestation. In addition she was thrombocytopenic with platelet counts ranging from 42,000-67,000 x microl(-1). Her esophageal varices were banded prophylactically on three occasions during her pregnancy. Magnetic resonance imaging at 32 wk gestation showed extensive caput medusa and dominant midline varix. Therefore, the planned mode of delivery was changed from Cesarean section which could result in massive hemorrhage, to elective induction of labour with an assisted second stage. The patient refused any blood product transfusion except acute hemodilution and cell saving if necessary during labour and delivery. Despite elaborate preparations for a planned vaginal delivery, she underwent an unanticipated rapid labour. Spinal analgesia was provided to facilitate smooth assisted vacuum delivery. CONCLUSION: Multidisciplinary care is the key for a successful outcome in parturients with cirrhosis. Periodic examination and banding of esophageal varices is recommended during pregnancy. Active consideration should be given to availing of the benefits of regional anesthesia.

Transcutaneous PCO2 monitoring during laparoscopic cholecystectomy in pregnancy.

PURPOSE: Respiratory acidosis during carbon dioxide (CO2) insufflation has been suggested as a cause of spontaneous abortion and preterm labour following laparoscopic cholecystectomy during pregnancy. Capnography may not be adequate as a guide to adjust pulmonary ventilation during laparoscopic surgery and hence arterial carbon dioxide (PaCO2) monitoring has been recommended. We report the feasibility and benefits of transcutaneous carbon dioxide monitoring (PtcCO2) as an approach to optimise ventilation during laparoscopic surgery in pregnancy. METHOD: A healthy parturient received general anaesthesia for laparoscopic cholecystectomy. Pulmonary ventilation was adjusted to maintain end-tidal carbon dioxide (conventional PETCO2) at 32 mmHg during CO2 insufflation. A PtcCO2 monitor was used to trend PaCO2 throughout the procedure. Mechanical ventilation was interrupted every five minutes to obtain an end-tidal PCO2 value at large tidal volume (squeeze PETCO2). RESULTS: The PtcCO2 increased from 39 mmHg before induction to 45 mmHg after CO2 insufflation. This corresponds to an estimated maximum PaCO2 of 39-40 mmHg during insufflation. The PtcCO2 gradually returned to pre-induction baseline values one hour after the termination of CO2 insufflation. Squeeze PETCO2 values approximated PtcCO2 more closely than did conventional PETCO2 values (P < 0.01). CONCLUSION: Continuous PtcCO2 measurements as well as squeeze PETCO2 may be of clinical value in trending and preventing hypercarbia during laparoscopic surgery.

Negative pressure induced airway and pulmonary injury.

PURPOSE: To describe negative pressure injury occurring during the use of a laryngeal mask airway (LMA) in which airway bleeding rather than pulmonary oedema was the major complication. CLINICAL FEATURES: A patient presented to the day surgery unit for resection of a ganglion cyst on her right wrist. She underwent general anaesthesia using an LMA, and experienced severe laryngospasm and transient hypoxaemia (oxygen saturation to 66%) seven minutes after incision. This resolved within 90 sec of succinylcholine administration. Nonetheless, the LMA was removed, a tracheal tube was inserted atraumatically and positive pressure ventilation was maintained until the time of emergence, when fresh blood appeared in the tracheal tube. The blood ultimately became frothy, resembling pulmonary oedema fluid. Haemoptysis, continued postoperatively and led to the hospitalization of this ambulatory patient. CONCLUSION: Rapid development of large subatmospheric pressures, as can occur during severe laryngospasm, may disrupt the tracheobronchial vasculature causing airway bleeding. This bleeding should be distinguished from negative pressure pulmonary oedema.

Terminology and the current limitations of time capnography: a brief review.

The carbon dioxide (CO2) trace versus time (time capnography) is convenient and adequate for clinical use. This is the method most commonly utilized in capnography. However, the current terminology in time capnography has not yet been standardized and is, therefore, a potential source of confusion. Standard terminology that is based on convention and logic to represent the various phases of a time capnogram is essential. The time capnogram should be considered as two segments: an inspiratory segment and an expiratory segment. The inspiratory segment is termed as phase ); the expiratory segment is divided into phases I, II, III, and, occasionally, IV. Phase I represents the CO2-free gas from the airways (anatomical dead space); phase II consists of a rapid S-shaped upswing on the tracing due to mixing of dead space gas with alveolar gas; and phase III, the alveolar plateau, represents CO2-rich gas from the alveoli. The physiologic basis of phase IV, the terminal upswing at the end of phase III, which is observed in capnograms recorded under certain circumstances (such as in pregnant subjects and obese subjects) is discussed in detail. The clinical implications of the alpha angle, which is the angle between phases II and III, and the beta angle, which is the angle between phases III and the descending limb of phase 0, are outlined. The subtle but important limitations of time capnography are reviewed; its current status as well as its future potential are explored.

Inspiratory valve malfunction in a circle system: pitfalls in capnography.

Capnography is a useful technique in monitoring the integrity of anaesthetic equipment such as the malfunctioning of unidirectional valves in circle system. However, the lack of a precise mechanism in existing capnographs to identify the start of inspiration and the beginning of expiration in the capnograms, makes the analysis of the carbon dioxide waveforms during inspiration difficult and thus results in inaccurate assessment of rebreathing. We report a case where, during the malfunction of the inspiratory unidirectional valve in the circle system, the capnograph failed to detect the presence of substantial rebreathing. Critical analysis of the capnogram recorded during the malfunction revealed that there was substantial rebreathing which was underestimated by the capnograph as it reports only the lowest CO2 concentration rebreathed during inspiration in such abnormal situations.

Inspiratory valve malfunction in a circle system: pitfalls in capnography

Capnography is a useful technique in monitoring the integrity of anaesthetic equipment such as the malfunctioning of unidirectional valves in circle system. However, the lack of a precise mechanism in existing capnographs to identify the start of inspiration and the beginning of expiration in the capnograms, makes the analysis of the carbon dioxide waveforms during inspiration difficult and thus results in inaccurate assessement of rebreathing. We report a case where, during the malfunction of the inspiratory unidirectional valve in the circle system, the capnograph failed to detect the presence of substantial rebreathing. Critical analysis of the capnogram recorded during the malfunction revealed that there was substantial rebreathing which was underestimated by the capnograph as it reports only the lowest CO2 concentration rebreathed during inspiration in such abnormal situations.(AU)

Anaesthesia without nitrous oxide

Nitrous oxide has a long history of successful use in inhalational anaesthesia. Nevertheless questions are being raised over possible deleterious effects which may complicate its routine use. As more potent volatile agents have become available, compressed air/oxygen mixtures are gradually replacing nitrous oxide as a carrier gas in inhalational anaesthesia. We recommend that compressed air be installed on all anaesthetic machines and that in future, machines be designed so as to make it impossible to administer both nitrous oxide and air simultaneously. (Summary)

Capnometry and anaesthesia.

In the last decade, capnography has developed from a research instrument into a monitoring device considered to be essential during anaesthesia to ensure patient safety. Hence, a comprehensive understanding of capnography has become mandatory for the anaesthetist in charge of patients in the operating room and in the intensive care unit. This review of capnography includes the methods available to determine carbon dioxide in expired air, and an analysis of the physiology of capnograms, which are followed by a description of the applications of capnography in clinical practice. The theoretical backgrounds of the effect of barometric pressure, water vapour, nitrous oxide and other factors introducing errors in the accuracy of CO2 determination by the infra-red technique, currently the most popular method in use, are detailed. Physiological factors leading to changes in end-tidal carbon dioxide are discussed together with the clinical uses of this measurement to assess pulmonary blood flow indirectly, carbon dioxide production and adequacy of alveolar ventilation. The importance of understanding the shape of the capnogram as well as end-tidal carbon dioxide measurements is emphasized and its use in the early diagnosis of adverse events such as circuit disconnections, oesophageal intubation, defective breathing systems and hypoventilation is highlighted. Finally, the precautions required in the use and interpretation of capnography are presented with the caveat that although no instrument will replace the continuous presence of the attentive physician, end-tidal carbon dioxide monitoring can be effective in the early detection of anaesthesia-related intraoperative accidents.

Propofol: a new intravenous anaesthetic

Propofol, a new intravenous anaesthetic induction agent, was evaluated on female patients undergoing short surgical procedures. The incidence of pain on injection, apnoea following injection, and the fall of systolic and diastolic blood pressure levels, was similar to that previously reported. There was no significant fall in pulse rate. The quality of anaesthesia during induction was good in all patients who reported they would be happy to receive the drug again (AU)