Informed consent for epidural analgesia in labour

Consent for epidural analgesia for labour is unique. The issues of patient autonomy and competence are controversial because of the limited antenatal education that most South African patients receive, and the absence of a culture of structured birth planning. Frequently, such patients are first encountered by the anaesthetist when in advanced labour and limited time is available for explanation. Overall, this represents the most extreme example of obtaining consent in compromised circumstances

Recipes for obstetric spinal hypotension: The clinical context counts

Hypotension following obstetric spinal anaesthesia remains a common and important problem. While recent research advances have brought us closer to the perfect recipe for the obstetric spinal anaesthetic, these advances have not been translated into practical guidelines able to reduce the unacceptable number of fatalities that occur in environments where resources are limited. In South Africa, more than half of anaesthetic deaths are still related to spinal hypotension. A gap exists between the ‘perfect recipe’, developed from a clinical context rooted in resource-rich research environments, and its application and performance in real-world resource-poor environments – conditions experienced by more than 75% of the world’s population. This review attempts to define this knowledge gap and proposes a research agenda to address the deficiencies

Managing spinal hypotension during caesarean section: An update

Hypotension is common after spinal local anaesthesia for caesarean section. However, the substandard treatment of spinal hypotension and associated complications are responsible for up to two-thirds of deaths that occur in South Africa (SA) for caesarean section under spinal anaesthesia. In some cases, spinal hypotension may be predicted by simple parameters such as age >25 years, preoperative heart rate >90 bpm and preoperative mean arterial pressure <90 mmHg. Heart rate variability and point-of-care echocardiography also predict hypotension with greater accuracy, but are limited by equipment and training issues. Spinal anaesthesia is absolutely contraindicated if the parturient is hypovolaemic. Left lateral tilt is still advised, despite the absence of strong supporting evidence. The dose of spinal bupivacaine should not be reduced in obese patients. Crystalloid co-loading is an adequate fluid strategy in most cases, but is of limited efficacy in the prevention of hypotension. It is imperative that immediately after the patient is placed supine, close attention is paid to communication with her, heart rate changes and pulse volume. Early intervention with phenylephrine is the first-line approach for hypotension if heart rate is preserved under spinal anaesthesia. Phenylephrine infusions (25 - 50 μg/min) are easy to administer, maintain baseline maternal haemodynamics and are applicable to the SA context. The vigilant use of phenylephrine boluses (50 - 100 μg), targeting maternal heart rate as a surrogate for cardiac output, is also effective. Noradrenaline has been used successfully to prevent spinal hypotension, but evidence does not yet suggest practice change. Local and international guidelines have recently been published

Observation of the pulse oximeter trace to estimate systolic blood pressure during spinal anaesthesia for Caesarean section: the effect of body mass index

Background: The estimation of systolic blood pressure by disappearance and reappearance of the pulse oximeter trace during cuff inflation and deflation was compared with non-invasive blood pressure (NIBP) measurement, across the range of body mass index (BMI), during spinal anaesthesia for Caesarean section.Methods: Seventy-five parturients were recruited, with BMI of < 30 (Group 1), 30–40 (Group 2), and > 40 kg/m2 ((morbidly obese, Group 3). A non-invasive blood pressure monitor was used with the pulse oximeter probe on the ipsilateral arm. Estimations were done before induction and 5 min after induction of spinal anaesthesia, during cuff inflation and deflation. Bland and Altman analysis was performed and the concordance correlation coefficient (r) estimated.Results: For estimation of systolic blood pressure during cuff inflation under spinal anaesthesia in Groups 1, 2 and 3: r = 0.57, 0.74 and 0.91; bias = –0.4, –2.9 and 0.8 mmHg, and limits of agreement = –27.7 to 26.9, –27.7 to 21.9, and –15.9 to 17.5 mmHg respectively. The mean (SD) time saved by estimation during inflation compared with measurement in Groups 1, 2 and 3 was 22.8 (13.2) s, 30.0 (11.6) s and 33.0 (15.6) s respectively. In Group 3, the percentage error was ± 13% of mean systolic blood pressure.Conclusions: Estimation of systolic blood pressure during cuff inflation under spinal anaesthesia in the morbidly obese is more precise than in lower BMI parturients. Time to estimation is relevantly shorter than measurement. This could improve patient safety by rapid and accurate identification of hypotension in these high-risk patients. This estimation method is associated with limits of agreement that may be clinically significant even in morbidly obese patients, and should not be considered a replacement for subsequent NIBP measurement.Keywords: body mass index, Caesarean section, pulse oximeter trace, spinal anaesthesia, systolic blood pressur

Incidence of intraoperative nausea and vomiting during spinal anaesthesia for Caesarean section in two Cape Town state hospitals

Background: Intraoperative nausea and vomiting (IONV) during spinal anaesthesia (SA) for Caesarean section (CS) is unpleasant and may interfere with surgery. The incidence of IONV during elective CS was studied, as well as the influence of ethnicity on this outcome.Methods: A total of 258 healthy term patients undergoing SA for elective CS were recruited to this prospective observational study conducted at two Cape Town Level 2 hospitals. Standard practice was employed for SA for CS at the University of Cape Town: 2 ml hyperbaric bupivacaine plus 10 μg fentanyl at the L3/4 interspace, and 15 mL/kg crystalloid coload. Spinal hypotension was managed with phenylephrine boluses according to a standard protocol. Nausea and/or vomiting were treated by restoration of blood pressure, and metoclopramide. Intraoperative complaints of nausea, and vomiting, were noted. Patients were also interviewed postoperatively as to any experience of intraoperative or previous history of nausea.Results: Of the 258 patients enrolled in the audit, 112 (43.4%) were non-African and 146 (56.6%) were Black African patients. The overall incidence (95% CI) of nausea was 0.32 (0.27–0.38), with 20% occurring prior to and 11% after the delivery. The overall incidence of vomiting was 0.07 (0.05–0.11), with 3.2% occurring prior to and 3.8% after delivery. The incidence of nausea and/or vomiting was 0.33 (0.28 – 0.40). Black Africans experienced significantly less nausea than non-African patients (36/145 [24.8%] vs. 47/112 [42.0%] respectively, p = 0.004). There was no significant difference in the incidence of vomiting (10/145 [6.8%] vs. 8/112 [7.1%] respectively). The odds of experiencing intraoperative nausea for patients with any blood pressure value < 70% of baseline were 2.46 (95% CI 1.40–4.33).Conclusions: Though in keeping with international standards, the clinically significant incidence of nausea and/or vomiting of 33% requires adjustments to the management protocol for spinal hypotension. The inclusion of ethnicity as a risk factor for nausea during SA for CS should be considered.Keywords: Caesarean section, ethnicity, intraoperative, nausea and vomiting, spinal anaesthesi

Editorial: Is the HPCSA requirement for a research dissertation for specialist registration the best option?

No Abstrac

Radial asymptotics of Lemaitre-Tolman-Bondi dust models

We examine the radial asymptotic behavior of spherically symmetric Lemaitre-Tolman-Bondi dust models by looking at their covariant scalars along radial rays, which are spacelike geodesics parametrized by proper length $\ell$, orthogonal to the 4-velocity and to the orbits of SO(3). By introducing quasi-local scalars defined as integral functions along the rays, we obtain a complete and covariant representation of the models, leading to an initial value parametrization in which all scalars can be given by scaling laws depending on two metric scale factors and two basic initial value functions. Considering regular "open" LTB models whose space slices allow for a diverging $\ell$, we provide the conditions on the radial coordinate so that its asymptotic limit corresponds to the limit as $\ell\to\infty$. The "asymptotic state" is then defined as this limit, together with asymptotic series expansion around it, evaluated for all metric functions, covariant scalars (local and quasi-local) and their fluctuations. By looking at different sets of initial conditions, we examine and classify the asymptotic states of parabolic, hyperbolic and open elliptic models admitting a symmetry center. We show that in the radial direction the models can be asymptotic to any one of the following spacetimes: FLRW dust cosmologies with zero or negative spatial curvature, sections of Minkowski flat space (including Milne's space), sections of the Schwarzschild--Kruskal manifold or self--similar dust solutions.Comment: 44 pages (including a long appendix), 3 figures, IOP LaTeX style. Typos corrected and an important reference added. Accepted for publication in General Relativity and Gravitatio

DT/T beyond linear theory

The major contribution to the anisotropy of the temperature of the Cosmic Microwave Background (CMB) radiation is believed to come from the interaction of linear density perturbations with the radiation previous to the decoupling time. Assuming a standard thermal history for the gas after recombination, only the gravitational field produced by the linear density perturbations present on a $\Omega\neq 1$ universe can generate anisotropies at low z (these anisotropies would manifest on large angular scales). However, secondary anisotropies are inevitably produced during the nonlinear evolution of matter at late times even in a universe with a standard thermal history. Two effects associated to this nonlinear phase can give rise to new anisotropies: the time-varying gravitational potential of nonlinear structures (Rees-Sciama RS effect) and the inverse Compton scattering of the microwave photons with hot electrons in clusters of galaxies (Sunyaev-Zeldovich SZ effect). These two effects can produce distinct imprints on the CMB temperature anisotropy. We discuss the amplitude of the anisotropies expected and the relevant angular scales in different cosmological scenarios. Future sensitive experiments will be able to probe the CMB anisotropies beyong the first order primary contribution.Comment: plain tex, 16 pages, 3 figures. Proceedings of the Laredo Advance School on Astrophysics "The universe at high-z, large-scale structure and the cosmic microwave background". To be publised by Springer-Verla

On the spherical-axial transition in supernova remnants

A new law of motion for supernova remnant (SNR) which introduces the quantity of swept matter in the thin layer approximation is introduced. This new law of motion is tested on 10 years observations of SN1993J. The introduction of an exponential gradient in the surrounding medium allows to model an aspherical expansion. A weakly asymmetric SNR, SN1006, and a strongly asymmetric SNR, SN1987a, are modeled. In the case of SN1987a the three observed rings are simulated.Comment: 19 figures and 14 pages Accepted for publication in Astrophysics & Space Science in the year 201

Cosmological background solutions and cosmological backreactions

The cosmological backreaction proposal, which attempts to account for observations without a primary dark energy source in the stress-energy tensor, has been developed and discussed by means of different approaches. Here, we focus on the concept of cosmological background solutions in order to develop a framework to study different backreaction proposals.Comment: 14 pages, 5 figures; major changes, replaced to match the version published in General Relativity and Gravitatio