The sequence of amino acids for each chain is known, and this difference being on the ‘p’ chain at position number 6, where valine is substituted for a glutamic acid.
There are hundreds of abnormal forms of haemoglobin; this is because of a single amino acid substitution in the beta chain. HbS is important in that the abnormal forms are associated with significant clinical effects, this being due to the ‘s’ the many different variants of haemoglobin, including HbS, the substitution that takes place at position number ‘6’ this happens at the external surface of the molecule, where the valine molecule is able to bond with leucine and phenylalanine groups on the neighbouring haemoglobin molecules when oxygen is released.
The conditions of low oxygen, HbS molecules polymerize, or 'stack', converting the haemoglobin from a Fluid, or 'sol', state to a viscous or 'gel', state. The stiff rods of HbS form, this then means the deformation of red cells into an elongated or sickle shaped cells. Polymerisation will only take place, if the cell contains mainly HbS molecules. If there is a diluted state of HbS with normal HbA this makes the red blood cells reasonably resistant to sickling this is because of polymerisation being a result of reactions between HbS molecules. HbS and HbA molecules do not 'bond' in the same way as two HbS molecules. The red blood cells in a person with sickle Cell anaemia (SS) the HbS is generally between 80 and 100 per cent. For people with sickle cell trait (AS) the per cent of HbS is between 45 and 55, this is generally deemed too low to cause sickling, although sickling could occur under extreme conditions. HbS has several other unusual properties, which is why it can be detected in a very precise way. Its solubility differs from HbA in a way that it can be detected by inexpensive screening tests. Midence and Elander (1994 p9-10)
Clinical Features
Platt et al(1994) as cited in Frith and Head(2004 p771-2) states "The clinical picture of sickle cell disease is one of evolving organ damage punctuated by intermittent periods of severe pain and pulmonary complications. The severity and progression of the disease is remarkably varied, with some patients experiencing a relatively indolent course and others suffering early organ dysfunction and death. Pulmonary and neurological disease are the leading causes of morbidity and mortality." According to Firth and Head (2004 p772) “Many deaths are not attributable to overt chronic organ failure but occur during an acute episode of pain, respiratory compromise, stroke, or a combination of these events."
Perioperative
Even though sickle cell trait does not have a marked increase of morbidity or mortality in the perioperative setting. Atlas SA (1974) and Heller et al(1979) cited in Firth and Head (2004 p773), patients with sickle cell disease are known to have high incidences of perioperative problems, these can be sickle cell disease specific and can include pain crisis and acute respiratory syndrome, occurring with high frequency in the perioperative period there may also be a risk of erythrocyte alloimmunization and transfusion reaction complications, or there may be non-specific these can include fever, infection, bleeding, thrombosis, embolism and death from other causes than sickle cell disease.
In patients with sickle cell disease the main risk we have to be careful of is vaso-occlusive crisis a precipitating event leads to a sickling cycle as blood flow becomes more sluggish and coaguable leading to hypoxia in the tissue. Ross (1997)
When considering the precipitating factors of vaso-occlusive crisis it is clear that every patient who undergoes surgery may be exposed to some or all of these precipitating factors these factors being hypoxia, dehydration, temperature changes, acidosis, and infection. Bassett (1996)
Hypothermia or temperature control is important as sickling is affected by temperatures below 36.6-37.5c stimulating the sickling process. This is caused because hypothermia triggers vasoconstriction in the peripheral circulation reducing the oxygen delivery to the tissues, due to the very nature of the operating theatre hypothermia is common especially due to long and invasive surgeries so steps must be taken to actively warm the patients. Hammer (2003).
Intraoperative hypothermia exists for many patients undergoing surgery including those with sickle cell anaemia, the delivery of the anaesthetic depresses the patients own ability to maintain temperature due to the suppressing the patients thermoregulatory centre. Muscle relaxants used on the patient relaxes the patients striated muscle tone, this being one of the major sources of heat production in the body. King (1998)
In a patient who has no underlying medical conditions prior to surgery, hypothermia is easy to reverse and the effects it has on the body are reversible, with a patient who has sickle cell anaemia the effects of hypothermia are painful and possibly dangerous, if a patient becomes hypothermic a vaso-occlusive crisis will happen, this means the blood flow is interrupted and restricted, when severe ischemia happens the patient will experience pain excessive to the pain of surgery, during this period patients tissues are at risk of circulatory interruptions causing any area of the body to be susceptible to ischemia and necrosis. Bassett (1996)
Failure to plan for the possibility of hypothermia is an important factor, especially during the period of setting up for a major case, where there is a heightened risk of prolonged exposure to the patient, also the administration of cold blood and fluids during surgery also adds to the likelihood of hypothermia. Hypothermia may be prevented by being aware of the possibility, monitoring of the patient, increased theatre temperature, covering the patient, warm water or warm air mattress, warm IV fluids and blood, and the use of forced air warming blankets. Davey and Ince (2004)
As an Operating department practitioner I would prepare the theatre to receive a patient. With the knowledge of sickle cell disease I would be aware of providing the adequate warming equipment, I would prepare the fluid warmer so that none of the fluid was cold when it entered the patient I would also have a warm air blanket and increase the ambient temperature of the theatres.
In module seven of the operating department practitioner’s education course we discussed the disease and pathology of disease, we discussed how disease affects an individual’s body and how the body creates its own homeostasis to live with the disease. Each patient lives within homeostasis and under anaesthetic we try to create this artificially and must try to create a homeostasis that is appropriate for that individual as care should be individualised to each patient, in a patient with sickle cell disease their homeostasis must be protected and the care by myself and the theatre team adapted personally for that patient, for example in my time in practice we don't warm every patient for every procedure but patients with sickle cell disease we would do.
Conclusion
Sickle cell disease is a dynamic, lifelong and sometimes debilitating disease. People with sickle cell disease can often present for surgical intervention of ailments related or unrelated to the consequences of the illness. Tobin and Butterworth (2004)
Management of a patient with sickle cell disease during the Intraoperative phase is a challenge to the anaesthetic team, as reversal of the sickling process to date has been difficult, with the anaesthetist focusing on prevention. Dix HM (2001) Most recommendations with regarding the measures to protect the patient from potential vaso-occlusive crisis are generally accepted with little controversy. Tobin and Butterworth (2004)
Recommendations that are readily accepted are to keep the operative area warm, the patient hydrated and well oxygenated as well as paying meticulous attention to positioning in order to avoid circulatory stasis. Dix (2001) Throughout this assignment I have been looking at the importance of how underlying medical conditions affect the peri-operative care of the patient, with this in mind I feel that recognising these factors would greatly improve the care I would give the patient.
Reference List
Bassett C (1996) Caring for surgical patients with sickle cell disease Nursing Standard May 10(33) 38-39
Davey A and Ince CS (2004) Fundamentals of Operating Practice 2nd London:2004
Dix HM (2001) New Advances in the treatment of sickle cell disease: Focus on perioperative significance AANA Journal August 69(4) 281-6
Firth PG, Head A (2004) Sickle Cell Disease and Anaesthesia. Anaestesiology Sep 101(3) 766-85
Hammer et al (2003) Perioperative care for patients with sickle cell who are undergoing total hip replacement as treatment for osteonecrosis. Orthopaedic Nursing Nov/Dec 22(6): 384-97
King (1998) Brigdens Operating Department Practice 1st Bath:Churchill Livingstone
Midence K, Elander J, (1994) Sickle Cell Disease a Psychosocial Approach. 1st. Oxford: Radcliffe Medical Press
Ross J (1997) a trauma patient with sickle cell anemia Journal of Emergency Nursing June 23(3) 211-13
Tobin JR, Butterworth J (2004) Sickle Cell Disease: Dogma, Science and Clinical Care Anesthesia and Analgesia Febuary 98(2) p283-284
Bibliography
Southorn P (2002) Perioperative Management of the medically at risk patient Clinical Obstetics Gynecology June 45(2) 449-468
Riddington C, Williamson L, Perioperative blood transfusion for sickle cell disease (Cochrane Review) In: The Chochrane Library Issue 3 2004. Chicester UK: John Wiley & sons, Ltd
Riddington C, Wang W, Blood transfusion for preventing stroke in people with sickle cell disease (Cochrane Review) In: The Chochrane Library Issue 3 2004. Chicester UK: John Wiley & sons, Ltd
Pemberton PL et al (2002) A retrospective observational study of pre-operative sickle cell screening. Anaesthesia 57 334-7
Anthony M L, Hardee E, (1999) Laparoscopic splenectomy in children with sickle cell disease AORN Journal March 69(3) 568-90
Provan D (2003) ABC of Clinical Haematology 2nd (BMJ Books) London: BMJ Books
Pallister CJ (1999) Haematology 1st (BMS Explained) Oxford: Butterworth & Heinemann
Mehta A, Hoffbrand V, (2000) Haematology at a Glance 1st London: Blackwell Science
