End-tidal carbon dioxide concentration, carbon dioxide production, heart rate, and blood pressure as indicators of induced hyperthermia

Predicting a pulse: Can monitoring heart rate and end-tidal carbon dioxide minimize compression pauses and impact outcomes in out-of-hospital cardiac arrest?

Case Scenario

Simple SummaryIn this observational study, we aimed to describe the cardiorespiratory variations during laparoscopic abdominal surgery in baboons (Papio hamadryas) anesthetized via a laryngeal mask. Animals were immobilized with a combination of tiletamine/zolazepam and medetomidine. A laryngeal mask was inserted to allow for the delivery of oxygen and isoflurane. Cardiovascular variables showed no alterations, while the respiratory parameters indicated a rise in respiratory rate and end-tidal carbon dioxide concentration during the pneumoperitoneum. Hypercapnia was mild, even with the animal in spontaneous breathing, and it was solved rapidly after the discontinuation of the pneumoperitoneum. The results of this study suggest that laparoscopy can be performed safely in spontaneously breathing baboons. Furthermore, adequate ventilation and gas exchange can be achieved using a laryngeal mask without the need for endotracheal intubation.The study aims to describe the anesthetic and airway management of baboons (Papio hamadryas) undergoing laparoscopic salpingectomy with a laryngeal mask airway (LMA) device. Eleven baboons received tiletamine-zolazepam and medetomidine; anesthesia was induced with propofol. An LMA was positioned for oxygen and isoflurane administration in spontaneous respiration. Heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), end tidal carbon dioxide (EtCO2), minute volume (MV), and peripheral hemoglobin oxygen saturation (SpO2) were recorded before (PREPP) and immediately after abdomen insufflation (PP1), at 10 (PP2), 20 (PP3), and 30 (PP4) minutes during pneumoperitoneum, and after (POSTPP) pneumoperitoneum. The respiratory rate was significantly higher at all times compared to PREPP. The end tidal carbon dioxide concentration was significantly higher at PP2, PP3, PP4, and POSTPP, compared to the previous times. The higher values for RR and EtCO2 were registered at PP4: 22.7 (95% CI 17.6–27.8) breaths/min and 57.9 (95% CI 51.9–63.8) mmHg, respectively. The minute volume was significantly higher at PP4 and POSTPP compared to the other times. The higher value for MV was registered at POSTPP (269.1 (95% CI 206.1–331.8) mL/kg/min). This protocol is suitable for baboons undergoing laparoscopic salpingectomy. The LMA was easy to insert and allowed for good ventilation, gas exchange, and delivery of the anesthetic in spontaneous breathing baboons.

In patients with phaeochromocytoma there may be marked catecholamine release during anaesthesia, particularly during manipulation of the tumour. The release may result in a hypermetabolic state, and an increase in blood pressure and heart rate. We have observed another consequence – an increase in the end-tidal carbon dioxide concentration (EtCO2). Case 1: a 38 year-old man with a phaeochromocytoma was scheduled for adrenalectomy. Pre-operatively, both α- and β-blocking agents were used to control blood pressure (124/70 mmHg) and heart rate (112 bpm). After insertion of an epidural catheter, general anaesthesia was induced, and anaesthesia was maintained with sevoflurane 2% in oxygen and intermittent epidural infusion of mepivacaine 1.5%. The lungs were ventilated with a tidal volume of 650 ml and respiratory rate 10. The EtCO2 was 30–32 mmHg (4.1 kPa). Blood pressure, heart rate and end-tidal carbon dioxide remained stable until the surgeons started to manipulate the tumour, when blood pressure started to increase. The hypertension was controlled (< 160/80 mmHg) with an infusion of nitroglycerin and nicardipine, and the heart rate controlled with propranolol. The EtCO2 increased to 40 mmHg (5.3 kPa) (see Figure 4). There was difficulty in identifying the adrenal veins, but when the vessels were tentatively identified and clamped the EtCO2 started to fall, indicating that they were the correct veins. The blood pressure also fell and crystalloids and a dopamine infusion were required to maintain it within normal limits. Change in end-tidal carbon dioxide concentration during adrenalectomy for phaeochromocytoma. Case 2: a 45 year-old woman with a phaeochromocytoma was scheduled for adrenalectomy. After induction of general anaesthesia and neuromuscular blockade, the trachea was intubated and her lungs ventilated to produce an EtCO2 of 35–36 mmHg (4.7 kPa). During manipulation of the tumour, the EtCO2 increased and then decreased after surgery to baseline value (see Figure 4). It is likely in our patients that catecholamine release during adrenectomy produced a hypermetabolic state, increasing production of carbon dioxide. Correct ligation of adrenal veins may be confirmed by observing a decrease in the EtCO2.

Capnography: Clinical Aspects.

Nitrous oxide, in a concentration of 50% or more, is a known cerebral vasodilator. This study investigated whether a lower dose (30%) of nitrous oxide would also increase cerebral blood flow. In addition, the authors wished to study whether the increase in cerebral blood flow was accompanied by an increase in cerebral metabolism. Multimodal Magnetic Resonance Imaging at 3T was performed, and data were obtained in 17 healthy volunteers during three inhalation conditions: medical air, oxygen-enriched medical air (40% oxygen), and 30% nitrous oxide with oxygen-enriched medical air (40% oxygen). Arterial spin labeling was used to derive the primary tissue specific hemodynamic outcomes: cerebral blood flow, arterial blood volume and arterial transit times. Magnetic Resonance Susceptometry and proton Magnetic Resonance Spectroscopy were used for secondary metabolic outcomes: venous oxygenation, oxygen extraction fraction, cerebral metabolic oxygen rate and prefrontal metabolites. Nitrous oxide in 40% oxygen, but not 40% oxygen alone, significantly increased gray matter cerebral blood flow (22%; P < 0.05) and arterial blood volume (41%; P < 0.05). Venous oxygenation increased in both oxygen and nitrous oxide conditions. Compared with medical air inhalation, nitrous oxide condition caused a significantly larger decrease in oxygen extraction fraction than 40% oxygen alone (mean [SD] 11.3 [5.6]% vs. 8.3 [5.9]% P < 0.05), while global cerebral metabolic rate and prefrontal metabolites remained unchanged. This study demonstrates that 30% nitrous oxide in oxygen-enriched air (40% oxygen) significantly increases cerebral perfusion, and reduces oxygen extraction fraction, reflecting a strong arterial vasodilatory effect without associated increases in metabolism.

S177 INTRODUCTION: During general anesthesia, most patients have their ventilation controlled mechanically, in spite of touted advantages of spontaneous breathing. Further, modes of partial ventilatory support ubiquitous in the ICU, have gained little popularity in the operating room. We developed methodology to augment gas exchange of spontaneously breathing, anesthetized patients. METHODS: Twenty-seven adult patients (52 +/- 16 yrs; 75 +/- 16 kg) scheduled to undergo inhalation anesthesia signed a consent form approved by the Institutional Review Board. Anesthesia was induced with IV propofol, a laryngeal mask airway was positioned, and patients were allowed to breathe spontaneously. Anesthesia was maintained with isoflurane, nitrous oxide, oxygen and air. A flow transducer and gas sampling tube were connected to a monitor for determination of respiratory rate (RR), tidal volume (VT), minute ventilation (VE), inspired oxygen concentration, end-tidal carbon dioxide tension (PETCO2) and concentration of anesthetic agents. Heart rate (HR), mean arterial blood pressure (MAP), and SpO2 (%) were recorded. Baseline data were collected after surgical incision and patients breathed spontaneously for 15-min. They then randomly were assigned to undergo alternating 15-min trials of CPAP, or Apneustic Anesthesia Ventilation (AAV). CPAP was titrated to a level that, when released to atmospheric pressure, would produce a VT of 6 mL/kg body weight. The rate of AAV was titrated to reduce spontaneous breathing to [approximate]30% of the baseline value. Data are summarized as mean +/- SD. Data obtained during AAV and CPAP were compared using Student's t test for paired observations and were compared to baseline with Dunnett's test. RESULTS: End-tidal concentration of isoflurane (1.1 +/- 0.4%) and N2 O (62 +/- 11%), FIO2 (0.33 +/- 0.07), HR (73 +/- 14 /min), MAP (78 +/- 16 mmHg) and SpO2 (97 +/- 2%) statistically were comparable throughout the study. Total RR and E during AAV were less than baseline values (P<.001), but VT was significantly greater when generated by decrease in airway pressure than by spontaneous breathing during AAV. Movement of the surgical field was barely detectable. Variables reflecting respiratory function during baseline (Base), CPAP (9 +/- 2 cmH2 O) and AAV (Spont=spontaneous breath, Mech=mechanical breath) are summarized in Table 1 (*P<.001 v. Base; [dagger]P<.001 v. CPAP).Table 1DISCUSSION: Application of AAV in anesthetized, spontaneous breathing patients reduced respiratory rate and minute ventilation, but not alveolar ventilation. Breathing was facilitated with a peak airway pressure much lower than observed during traditional intermittent positive pressure ventilation. We conclude that AAV provides an efficient means of supplementing spontaneous breathing with minimal disruption of the surgical field. Therefore, AAV may be useful in patients who require general anesthesia, who might benefit from lack of paralysis and/or hyperventilation, and who are deemed to benefit from partial ventilatory support.

Mature green bell pepper fruit (Capsicum annuum L. cv. Yolo Wonder) exhibited a non-climacteric pattern of ethylene and carbon dioxide production during normal ripening and red color development at 24°C. Exposing detached mature green fruit to 500 ppm propylene in air for 48 hours, did not induce an increase in ethylene or carbon dioxide production. Wounding excised plugs of ovary wall tissue caused an increase in carbon dioxide production within one day, and an increase in ethylene production by the second day.

Dexmedetomidine sedation for radiological imaging studies is a relatively recent application for this drug. Previous studies have demonstrated some haemodynamic effects of dexmedetomidine, however, the effects remain poorly described in children. The aim of this study was to better define the effect of age on heart rate (HR) and blood pressure changes in children sedated for CT imaging with dexmedetomidine. At our institution dexmedetomidine is given for sedation for CT imaging as a bolus of 2 mcg.kg(-1) over 10 min followed by an infusion of 1 mcg.kg(-1).h(-1) with a second bolus if required. Detailed quality assurance data sheets document patient demographics, sedation outcomes, adverse events, and hemodynamic data are recorded for each patient. A total of 250 patients (range 0.1-10.6 years) received dexmedetomidine. ANOVA revealed strong evidence for changes in HR and mean arterial blood pressure during bolus and infusion relative to presedation values (P < 0.001). These changes were apparent in each age group and similar between groups. During the first bolus and during infusion, 82% and 93% of patients respectively were within the age-based normal range for HR. For mean arterial blood pressure, 70% of patients were within the normal range during first bolus and 78% during infusion. In the pediatric population studied, intravenous dexmedetomidine sedation was associated with modest fluctuations in HR and blood pressure. Hemodynamic changes were independent of age, required no pharmacologic interventions and did not result in any adverse events. By anticipating these possible hemodynamic effects and avoiding dexmedetomidine in those patients who may not tolerate such fluctuations in HR and blood pressure, dexmedetomidine is an appropriate sedative for children undergoing CT imaging.

Background: Carbon dioxide pneumoperitoneum during laparoscopic surgery produces significant elevation of arterial pressure and systemic and pulmonary vascular resistance. Dexmedetomidine (DX) and magnesium sulfate (MG) both depress the sympathetic activity and control the hemodynamic responses to pneumoperitoneum. Bolus followed by continuous infusion of DX has been used during laparoscopic surgeries as per literature. In the present study, a single dose of DX was used in view of its elimination half-life (2.1–3.1 h) (duration of action up to 2 h), sufficient to cover the average period of pneumoperitoneum created for laparoscopic cholecystectomy (LC). Aim: The aim of this study was to compare the effects of a single dose of DX, MG, and normal saline (NS) on hemodynamic responses to pneumoperitoneum during LC and postoperative hemodynamic stability. Methods: Forty-five patients (the American Society of Anesthesiologists Class I, 18–60 years, male and female) undergoing elective LC were selected and randomly divided by computer-generated randomization table into three equal groups. Patients were given either 100 ml NS 0.9% intravenous (group NS, n = 15) or DX 1 μg/kg in 100 ml NS (group DX, n = 15) or MG 50 mg/kg in 100 ml NS (group MG, n = 15) over 10 min in double-blinded manner after induction of anesthesia but before the creation of pneumoperitoneum. All patients were monitored for their heart rate (HR), noninvasive blood pressure, oxygen saturation, end-tidal carbon dioxide (CO2), intra-abdominal pressure, and isoflurane concentration and recorded at various intervals. Results: HR in groups DX and MG remained below the baseline value (before induction) of respective group throughout the procedure following the infusion of drug with a significant difference. There was also significant difference in HR among the groups at various time intervals (P &lt; 0.05). Systolic blood pressure was significantly different between groups NS and DX and groups DX and MG during the period of pneumoperitoneum at 10, 20, 30, and 40 min. A significant reduction in systolic blood pressure (SBP) of group DX as compared to its baseline value was observed throughout the period of pneumoperitoneum (P &lt; 0.05). Conclusion: DX 1 μg/kg and MG 50 mg/kg both were effective in their respective groups to control hemodynamic responses during CO2 pneumoperitoneum created for LC. MG provided more stability in hemodynamic parameters, whereas DX was associated with more than desired reduction in HR and SBP, hence further evaluation with a lower dose of DX is suggested.

Evaluation of Sevoflurane Anesthesia in Donkeys (Equus asinus) Premedicated With Xylazine and Induced With Thiopental

Blood pressure and heart periods fluctuate at respiratory frequencies in healthy humans. Some researchers ([8][1], [23][2]) explain this as a cause-and-effect relation: blood pressure changes trigger baroreflex-mediated R-R interval changes. Here I make the case that respiratory sinus arrhythmia is

SUMMARYExperiments have been carried out on carbon dioxide production from sand cultures with peptone and glucose solution inoculated with various types of bacteria and protozoa, and with glucose and ammonium sulphate solutions of varying concentrations and C/N ratio. The following results were obtained: The presence of protozoa increases the carbon dioxide production especially in mixed bacterial cultsres The increase of carbon dioxide production is greater in glucose solution than in peptone. A further increase in the number of protozoa has an unfavourable effect on the carbon dioxide production. The number of bacteria is smaller in the presence of protozoa than in their absence, but the bacterial efficiency is greater and more uniform. The bacterial numbers and carbon dioxide production are definitely correlated in peptone, but in glucose to a less degree especially in the presence of protozoa. The reduction of concentrations of glucose from 0–6 to 0–2 per cent. resulted in a greater percentage production of carbon dioxide. With a lower concentration (0–2 per cent.) of glucose the presence of protozoa causes a greater increase in carbon dioxide production than in higher concentrations (0–6 per cent.). In the absence of protozoa increasing the C/N ratio had no or only a slight depressing effect on carbon dioxide production. In the presence of protozoa increasing the C/N ratio is followed by a marked increase in carbon dioxide production. In bacterial cultures a lessening of the C/N ratio below 10/1 results in a fluctuation of bacterial numbers.I am indebted to Sir John Russell for his kindness in giving me facilities to carry out the work in this Institution. The work was done in Mr D. Ward Cutler's department, and I take this opportunity of expressing my gratitude for his ever ready help and unfailing kindness. For the culture of Colpidium I am greatly indebted to Miss Jane Meiklejohn of the same department.

Anesthetic effects of ketamine–medetomidine–hydromorphone in dogs during high-quality, high-volume surgical sterilization program under field conditions

Air Embolism during Intraoperative Endoscopic Localization and Surgical Resection for Blue Rubber Bleb Nevus Syndrome