Chan Yk

Retrospective review of spinal versus epidural anaesthesia for caesarean section in preeclamptic patients

A 5-year retrospective survey of anaesthesia for caesarean section for mild/moderate and severe preeclampsia was performed, covering the period between 1 January 1996 and 31 December 2000. One hundred and twenty-one cases of non-labouring preeclamptic patients receiving spinal or epidural anaesthesia for caesarean section were included for analysis. Comparisons were made of the lowest blood pressures recorded before induction of anaesthesia, during the period from induction to delivery and the period from delivery to the end of operation. The decreases in blood pressure were similar after spinal and epidural anaesthesia. The use of intravenous fluids and ephedrine were also comparable in the two anaesthetic groups. There was no difference in maternal or neonatal outcome. Our result supports the use of spinal anaesthesia in preeclamptic women.

Carbetocin compared to oxytocin in emergency cesarean section: a randomized trial.

OBJECTIVE To evaluate the uterotonic effect of carbetocin compared with oxytocin in emergency cesarean delivery. STUDY DESIGN Participants were randomized to intravenous bolus injection of 100mcg carbetocin or 10IU oxytocin after cesarean delivery of the baby. The primary outcome is any additional uterotonic which may be administered by the blinded provider for perceived inadequate uterine tone with or without hemorrhage in the first 24hours after delivery. Secondary outcomes include operating time, perioperative blood loss, change in hemoglobin and hematocrit levels, blood transfusion and reoperation for postpartum hemorrhage. RESULTS Additional uterotonic rates were 107/276 (38.8%) vs. 155/271 (57.2%) [RR 0.68 95% CI 0.57-0.81 p<0.001; NNTb 6 95% CI 3.8-9.8], mean operating time 45.9±16.0 vs. 44.5±13.1minutes p=0.26, mean blood loss 458±258 vs. 446±281ml p=0.6, severe postpartum hemorrhage (≥1000ml) rates 15/276 (5.4%) vs. 10/271 (3.7%) p=0.33 and blood transfusion rates 6/276 (2.2%) vs. 10/271 (3.7%); p=0.30 for carbetocin and oxytocin arms respectively. There was only one case of re-operation (oxytocin arm). In the cases that needed additional uterotonic 98% (257/262) was started intraoperatively and in 89% (234/262) the only additional uterotonic administered was an oxytocin infusion over 6hours. CONCLUSION Fewer women in the carbetocin arm needed additional uterotonics but perioperative blood loss, severe postpartum hemorrhage, blood transfusion and operating time were not different.

Pain during elective caesarean section under epidural anaesthesia: the effect of a 10° head-up tilt position

Abstract One hundred patients scheduled for elective caesarean section under epidural anaesthesia were randomized to have epidural loading doses in either the horizontal or a 10° head-up position. They were assigned to their position only after an initial dose of 4 ml of 0.5% bupivacaine had been given. Ten minutes after this dose they were given 10 ml of 0.5% bupivacaine and 50 μg of fentanyl in their allocated position. Pain during surgery was assessed by the patients using a visual analogue scale and by a blinded anaesthetist. Giving the main dose in the head-up tilt position reduced the incidence of intea-operative pain significantly. The median pain score for the head-up position was zero while the score was two for the horizontal position. The inter-quartile range was 0 to 2 for the head-up tilt position and 0 to 4 for the horizontal position ( P

Regional analgesia in obstetrics in the Far East

Regional analgesia and anaesthesia for obstetrics are established techniques in the Far East. Their availability and utilisation vary amongst the different countries in the region due not only to economic considerations but also to the cultural beliefs of the parturients as well as their health care providers. The use of regional analgesia for labour is abysmally low for a fair number of countries. However, the rates for labour analgesia in Hong Kong and Singapore approximate those found in the West reflecting their socio-economic status and strong links with the West. The predominant use of regional anaesthesia for caesarean section in the Far East is an appropriate practice in keeping with current recommended standards of obstetric anaesthetic care.

Local and Regional Analgesia for Labor and Delivery

Regional anesthesia is a safe, effective, and widely used modality for caesarean section delivery. In addition it is useful for controlling labor pain and postoperative pain. While severe complications are rare, common complications, such as hypotension, must be considered when using neuraxial anesthesia. Hypotension occurs in around half of individuals receiving central neuraxial block; coloading with crystalloid is a common method to prevent hypotension. Administration of vasopressors may be required to stabilize blood pressure. Local anesthetic toxicity is a potential complication, given the abundant vascularity of the epidural space; this presents concern for both parturient and fetus. Treating every epidural dose as a test dose can help avoid infusion of toxic doses. Paracervical and pudendal blocks are decreasing in popularity due to inadequate pain control and associated complications. Other complications to be considered in the obstetric population include neurologic dysfunction, infection, chronic adhesive arachnoiditis, postdural puncture headache, cauda equina lesion, damage to the spinal cord, transient neurologic symptoms, inadequate/extensive block, and rarely, respiratory and cardiac arrest.

Handedness in man: The energy availability hypothesis

More than 90% of the human species are right handed. Although outwardly our body appears symmetrical, a 50/50% lateralization in handedness never occurs. Neither have we seen more than 50% left handedness in any subset of the human population. By 12-15weeks of intrauterine life, as many as 6 times more fetuses are noted by ultrasound studies to be sucking on their right thumbs. Distinct difference in oxygenation leading to dissimilar energy availability between right and left subclavian arteries in place by week 9 of life may hold the clue to the lateralization of hand function and eventually, the same in the brain. We know there is a higher incidence of left handedness in males, twins, premature babies and those born to mothers who smoke. They may represent a subset with less distinct difference in oxygenation between the 2 subclavian arteries during the fetal stage. This hypothesis if correct not only closes the gap in understanding human handedness and lateralization but also opens a vista for new research to focus on in utero tissue energy availability and its impact on outcome in life.

Why Drugs Are Administered

We are alive due to the many physiological processes in the body that sustain life in an integrated and controlled manner. When these processes are not working adequately, care providers resort to the use of drugs to try to improve them. At other times, these physiological processes need to be reversed to reduce damage to the functions of cells, tissues, organs or systems in the body. Drugs may also be used for diagnostic reasons to determine the presence of a disease condition in a patient. Increasingly, drugs are used for non-clinical reasons to enhance a physiological process, usually in sports, to provide a competitive edge to the user. The variability in drug requirements may stem from pharmaceutical, pharmacokinetic and pharmacodynamic differences, and all these must be taken into consideration in meeting the needs of individual patients. A database of use of drugs in a country indirectly reflects the health status and disease patterns of that country.

Dosage Forms, Drug Calculations and Prescription

The pharmacodynamics and pharmacokinetics of a drug play an important role in how the drug is formulated, and which dosage form is suitable for use. It is also necessary to have different dosage forms to meet the different requirements of the patient. Drug formularies are a list of medicines available in an institution or country. When drugs are prescribed from a drug formulary, the drugs are very likely to be available. A clearly written prescription allows the pharmacist to dispense the drug without error. Error from this is further reduced by electronic prescribing which incorporates an inbuilt decision support strategy. Drug doses are expressed in different units and may be confusing to providers. An understanding of what these units signify is essential to enable accurate and reliable calculation of drug doses. It is also important to have a good understanding of this to know how to dilute the drugs and to be able to administer the correct dosage from these dilutions.

Oxygen as a Drug

Oxygen is a drug naturally available in the atmosphere. In the acutely ill patient, we administer it either from the environment at 21 % or from stored oxygen sources in higher concentrations. It is administered via nasal prongs, masks or other oxygen delivery and/or ventilator devices. Oxygen is delivered to the tissues by the cardiopulmonary system and is mainly carried by hemoglobin. Under hyperbaric conditions, more oxygen is carried in solution in the blood. Oxygen is necessary for the optimal production of ATP within the cells, which is the source of energy for all cellular function, without which cell death occurs. It is administered whenever tissue oxygen supply may be compromised, such as in low inspired oxygen conditions, poor tissue perfusion states, and inadequate or impaired hemoglobin carrying capacity. Oxygen from hyperbaric sources is used to combat air embolism and also to assist in poorly healing wounds associated with cancer therapy. Hazards of oxygen therapy include retinopathy of prematurity, lung fibrosis and seizures. Oxygen administration areas are also fire risk zones.

Steady-State Principles

Drugs must reach adequate concentrations at the site of action to achieve therapeutic effect. This is achievable with a single dose if the desired duration is short but most times the effective concentration should be of adequate duration. In order to maintain the required concentration for adequate duration, we try to achieve steady state at the tissue level whereby the rate of infusion is equal to the rate of elimination. With constant infusion, this is usually achievable within four to five half-lives of the drug. There are several strategies to accelerate the onset of steady state both in the plasma as well as in the tissue. This includes using a loading dose or intermittent loading doses. Once the steady state is achieved, the maintenance dose must still be continued. When the maintenance dose is stopped, the concentration in the blood and tissue starts to fall and may decrease below therapeutic levels. In the critically ill patients, tissue perfusion and renal function may affect the achievement and maintenance of steady state at the target site.