Cardiac output monitoring: Technology and choice.

The accurate quantification of cardiac output (CO) is given vital importance in modern medical practice, especially in high-risk surgical and critically ill patients. CO monitoring together with perioperative protocols to guide intravenous fluid therapy and inotropic support with the aim of improving CO and oxygen delivery has shown to improve perioperative outcomes in high-risk surgical patients. Understanding of the underlying principles of CO measuring devices helps in knowing the limitations of their use and allows more effective and safer utilization. At present, no single CO monitoring device can meet all the clinical requirements considering the limitations of diverse CO monitoring techniques. The evidence for the minimally invasive CO monitoring is conflicting; however, different CO monitoring devices may be used during the clinical course of patients as an integrated approach based on their invasiveness and the need for additional hemodynamic data. These devices add numerical trend information for anesthesiologists and intensivists to use in determining the most appropriate management of their patients and at present, do not completely prohibit but do increasingly limit the use of the pulmonary artery catheter.

Beware the airway filter: deadspace effect in children under 2 years.

BACKGROUND: Filters are increasingly used in breathing circuits as they protect the circuit from contamination and facilitate humidification of inspired gas. The use of filters, however, can augment the anatomical deadspace. This can be significant in children because they have much smaller tidal volumes. METHODS: Following institutional ethical approval, 20 healthy children <2 years of age who required tracheal intubation were recruited. Ventilation was adjusted to achieve an endtidal carbon dioxide (P(E)CO(2)) of 4.6 kPa (35 mmHg) when sampled at the tracheal tube (TT) adapter. Following a 10-min period of stabilization, an airway filter (22 ml) was introduced into the circuit. The respiratory rate (RR) was then adjusted to return P(E)CO(2) to 4.6 kPa (35 mmHg). RESULTS: A mean increase in ventilation of 1.42 (0.38) l x min(-1) was required to maintain a normal P(E)CO(2) level. Airway pressure and respiratory rate increased by 7.9 mmHg (4.6) and 19.8 breath x min(-1) (8.7) respectively. The P(E)CO(2) and partial pressure of inspired carbon-di-oxide (PiCO(2)) measured from the TT adapter were higher than measured from the filter port. The mean increase was 3.6 (1.6) mmHg for P(E)CO(2) and 5.9 (3.9) mmHg for PiCO(2). CONCLUSION: Amplified deadspace from airway filters results in a significant increase in ventilation needed to maintain a normal P((E)CO(2) in children <2 years of age with normal lungs. Sampling of P((E)CO(2) and PiCO(2) from the filter significantly underestimates the effect of increased deadspace. The effect of increased deadspace may be predicted using a proposed mathematical model.

Intravenous ketamine sedation for painful oncology procedures.

BACKGROUND: The aim of the study was to determine the efficacy and adverse effects of intravenous (i.v.) ketamine sedation administered by nonanesthetist physicians for painful procedures. METHODS: A single-agent, procedural sedation protocol using titrated doses of ketamine i.v. (maximum 2 mg.kg(-1)) was conducted in outpatient pediatric oncology patients undergoing lumbar puncture (LP), bone marrow biopsy/aspiration (BMBx/A) or combination (LP/BMBx/A) in a tertiary care setting. The efficacy of analgesia and sedation (ability to perform the procedure), procedure duration, recovery time and the occurrence of adverse events are described. RESULTS: Fifty-eight subjects of a median age of 5 years (1-13) and median weight of 20 kg (10.5-68) underwent 119 sedations. An LP was performed in 73% of cases, a BMBx/A in 13% and LP/BMBx/A in 13%. Efficacy was 100% and the mean dose of ketamine was 1.3 mg.kg(-1) (0.4). The mean duration of the procedure was 6.6 min (4.2) and the recovery time was 11 min (4-45). Two subjects (1.7%) had a hypoxemia (SpO2 of <94%). No major airway complications occurred. The prevalence of hypertension (systolic > 20% at 5 min) was 54%. The median pain visual analogue score (VAS) for an observer was 0 (range 0-3) and caregiver was 0 (range 0-4). The median VAS for satisfaction (observer) was 10 (range 7-10) and caregiver VAS was also 10 (range 5-10). At 24 h after discharge, the incidence of bad dreams was 3.3%; vomiting, 10.8%; and abnormal behavior, 4.2%. CONCLUSION: Ketamine i.v. up to 2 mg.kg(-1) is an effective sedative for oncology procedures using a defined protocol.